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Dearomatising Addition of Organolithiums<br />

<strong>to</strong> 2-Aryloxazolines:<br />

A <strong>Route</strong> <strong>to</strong> <strong>Carbasugar</strong> <strong>Analogues</strong><br />

A thesis submitted <strong>to</strong> the University of Manchester<br />

for the degree of Doc<strong>to</strong>r of Philosophy<br />

in the Faculty of Engineering and Physical Sciences<br />

2008<br />

Sean Parris<br />

School of Chemistry


Contents<br />

Abstract 6<br />

Declaration 7<br />

Notes on Copyright and the Ownership of Intellectual Property Rights 7<br />

<strong>The</strong> Author 8<br />

Acknowledgments 9<br />

Abbreviations & Conventions 10<br />

Chapter 1 – Dearomatising Additions in Organic Synthesis. . . . . . . . . . . . . . . . . 15<br />

1.1 Introduction 15<br />

1.2 Dearomatisation with Electrophilic Functionalisation 15<br />

1.2.1 Von Auwers-Woodward 15<br />

1.2.2 <strong>The</strong> Birch reduction 16<br />

1.3 Nucleophilic Dearomatisation without Heavy Metals 19<br />

1.3.1 Favourable electron withdrawing groups 20<br />

1.3.2 Dearomatising additions <strong>to</strong> oxzolines 26<br />

1.3.3 Catalytic systems 36<br />

1.4 Nucleophilic Dearomatisation of Metal Complexes 41<br />

1.4.1 (η 6 -Arene)Cr(CO) 3 41<br />

1.4.2 (η 6 -Arene)Mn(CO) 3 cationic complexes 45<br />

1.4.3 Pd-mediated dearomatisation 48<br />

1.5 Summary of Methods 50<br />

Chapter 2 – Dearomatising Additions <strong>to</strong> Aryl Oxazolines . . . . . . . . . . . . . . . . . . 51<br />

2.1 Establishing a New Reaction 51<br />

2.2 Optimisation of Reaction Conditions 57<br />

2.2.1 Solvent system 57<br />

2.2.2 Duration of reaction 60<br />

2.2.3 Concentration of organolithium 61<br />

2.2.4 Temperature 61<br />

2.2.5 Order of addition 62<br />

3


2.3 Synthetic Scope 64<br />

2.3.1 Organolithiums 64<br />

2.3.2 Arenes 66<br />

2.3.3 Electrophiles 70<br />

2.4 Mechanistic Discussion 73<br />

2.4.1 Stereoselectivity 73<br />

2.4.2 Reaction pathway: one electron or two? 74<br />

2.4.3 Aggregation in organolithium chemistry 89<br />

2.5 Summary & Future Work 89<br />

Chapter 3 – Oxazoline Synthesis and Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . 95<br />

3.1 <strong>The</strong> Synthesis of 2,4,5-Oxazolines 95<br />

3.1.1 Literature methods for synthesis 95<br />

3.1.2 General strategies 100<br />

3.1.3 Amine synthesis 100<br />

3.1.4 Oxazoline synthesis 102<br />

3.2 Oxazoline Removal 107<br />

3.2.1 Literature methods for removal 107<br />

3.2.2 General strategies 111<br />

3.2.3 Reduction of oxazolines 114<br />

3.2.4 Oxazoline hydrolysis 118<br />

3.2.5 Quaternisation-reduction 121<br />

3.2.6 Determination of optical purity 128<br />

3.3 Summary and Future work 129<br />

Chapter 4 – <strong>The</strong> Synthesis of <strong>Carbasugar</strong>s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131<br />

4.1 <strong>Carbasugar</strong>s 131<br />

4.1.1 What they are and what they do 131<br />

4.1.2 Existing syntheses 133<br />

4.1.3 Synthetic outlook 137<br />

4.2 Synthesis of a <strong>Carbasugar</strong> Analogue 138<br />

4.2.1 Synthetic Strategy 138<br />

4.2.2 Influence axial oxazoline on reactivity 140<br />

4.2.3 Oxidation of the dienyl ether 142<br />

4.2.4 Enone reduction 145<br />

4


4.2.5 Protecting group strategy 147<br />

4.2.6 Oxidation of the allylic alcohol 148<br />

4.2.7 Synthesis of an altrose analogue 153<br />

4.2.8 Synthesis of an epoxycarbasugar 155<br />

4.2.9 1,4 transannular relationship for oxazolidine hydrolysis 157<br />

4.3 Revised Synthetic Strategy 157<br />

4.4 <strong>The</strong> Protecting Group-Free Synthesis of an Altrose Analogue 158<br />

4.4.1 <strong>Route</strong> A 159<br />

4.4.2 <strong>Route</strong> B or C: a model dihydroxylation 159<br />

4.4.3 <strong>Route</strong> B 160<br />

4.4.4 <strong>Route</strong> C 163<br />

4.5 Synthesis of a Mannose Analogue 164<br />

4.5.1 Strategy I: Lac<strong>to</strong>nisation 166<br />

4.5.2 Strategy II: Cyclohexene oxides 171<br />

4.6 Summary & Future Work 180<br />

References for Chapters 1-4 185<br />

Chapter 5 – Experimental Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193<br />

5.1 General 193<br />

5.2 Experimental Procedures for Chapter 2 197<br />

5.3 Experimental Procedures for Chapter 3.1 211<br />

5.4 Experimental Procedures for Chapter 3.2 235<br />

5.5 Experimental Procedures for Chapter 4.1 247<br />

5.6 Experimental Procedures for Chapter 4.2 263<br />

5.7 References for Experimental Section 274<br />

Appendix A Selected NMR spectra 275<br />

Appendix B Crystallographic Information Files 285<br />

Word count: 58,000<br />

5


Abstract<br />

Dearomatising Addition of Organolithiums <strong>to</strong> 2-Aryloxazolines:<br />

A <strong>Route</strong> <strong>to</strong> <strong>Carbasugar</strong> <strong>Analogues</strong><br />

A submission for the degree of Doc<strong>to</strong>r of Philosophy at <strong>The</strong> University of Manchester,<br />

Sean Parris April 2008<br />

Nucleophilic addition <strong>to</strong> functionalised benzenoid nuclei with concomitant<br />

dearomatisation is a powerful method for the construction of highly substituted<br />

synthetic building blocks. This thesis presents a highly stereoselective dearomatising<br />

addition of organolithium nucleophiles <strong>to</strong> 2-aryloxazolines A as the key step in the<br />

synthesis of carbasugar analogues.<br />

Ph<br />

O<br />

Ph<br />

N<br />

R<br />

A<br />

i) NuLi, DMPU<br />

ii) MeI<br />

Nu: i-Pr, s-Bu<br />

Ph<br />

O<br />

Ph<br />

N<br />

Nu<br />

R<br />

B<br />

i) H +<br />

ii) MeOTf,<br />

then NaBH 4<br />

iii) H 3 O +<br />

iv) NaBH 4<br />

Nu = i-Pr<br />

R = 4-OMe<br />

HO<br />

OH<br />

>99:1 er<br />

This methodology is analogous <strong>to</strong> that of Meyers with 2-naphthyloxazolines, but<br />

requires less rigorous conditions than existing dearomatising additions <strong>to</strong> sixmembered<br />

carbocycles which often use heavy metals (chapter 1). A range of<br />

oxazolines and reaction conditions have been studied and the diphenyl oxazoline A<br />

found <strong>to</strong> be optimal, with DMPU being crucial for the reaction (section 2.1).<br />

Reactivity of the nucleophile follows 2° > 3° >> 1° alkyllithiums, hinting at a single<br />

electron transfer process, which has been studied by preliminary EPR studies and<br />

cyclisable probes (section 2.4). Oxazolines A may be synthesised in high enantiomeric<br />

purity from trans-stilbene, whilst a number of methods have been studied for the<br />

cleavage of oxazolines <strong>to</strong> synthetically useful functional groups (chapter 3). <strong>The</strong><br />

dearomatising functionalisation has been used as the key step in the protecting groupfree<br />

synthesis of carbasugar analogues C and D, in fewer steps and better yields than<br />

most chiral pool syntheses, whilst permitting far greater flexibility (chapter 4).<br />

HO<br />

HO<br />

HO<br />

HO<br />

HO<br />

H<br />

O<br />

B<br />

Nu = i-Pr<br />

R = 4-OMe<br />

Ox*<br />

O<br />

OH<br />

OH<br />

OH<br />

HO<br />

O<br />

OH<br />

OH<br />

HO<br />

OH<br />

C<br />

HO<br />

HO<br />

HO<br />

OH<br />

D<br />

OH<br />

33%,<br />

6 steps from A<br />

OH<br />

43%,<br />

8 steps from A<br />

HO OH<br />

OH<br />

α-L-Altrose<br />

HO<br />

H<br />

HO<br />

O<br />

HO OH<br />

OH<br />

α-L-Mannose<br />

6


Declaration<br />

No portion of the work referred <strong>to</strong> in the thesis has been submitted in support of an<br />

application for another degree or qualification of this or any other university or other<br />

institute of learning.<br />

Notes on Copyright and the Ownership of Intellectual<br />

Property Rights<br />

i. <strong>The</strong> author of this thesis (including any appendices and/or schedules <strong>to</strong> this<br />

thesis) owns any copyright in it (the “Copyright”) and he has given <strong>The</strong><br />

University of Manchester the right <strong>to</strong> use such Copyright for any<br />

administrative, promotional, educational and/or teaching purposes.<br />

ii.<br />

Copies of this thesis, either in full or in extracts, may be made only in<br />

accordance with the regulations of the John Rylands University Library of<br />

Manchester. Details of these regulations may be obtained from the Librarian.<br />

This page must form part of any such copies made.<br />

iii.<br />

<strong>The</strong> ownership of any patents, designs, trade marks and any and all other<br />

intellectual property rights except for the Copyright (the “Intellectual Property<br />

Rights”) and any reproductions of copyright works, for example graphs and<br />

tables (“Reproductions”), which may be described in this thesis, may not be<br />

owned by the author and may be owned by third parties. Such Intellectual<br />

Property Rights and Reproductions cannot and must not be made available for<br />

use without the prior written permission of the owner(s) of the relevant<br />

Intellectual Property Rights and/or Reproductions.<br />

iv.<br />

Further information on the conditions under which disclosure, publication and<br />

exploitation of this thesis, the Copyright and any Intellectual Property Rights<br />

and/or Reproductions described in it may take place is available from the Head<br />

of School of Chemistry (or the Vice-President).<br />

7


<strong>The</strong> Author<br />

<strong>The</strong> Author graduated from the University of Cambridge in 2004 with a first class<br />

Masters degree in Natural Sciences. He completed his Part III research project under<br />

the supervision of Dr. Stuart Warren concerning the asymmetric synthesis of<br />

dihydrofurans using phosphine oxide chemistry. In the penultimate year of his<br />

undergraduate course, the Author attended the Massachusetts Institute of Technology<br />

where he gained a 5.0 grade point average, and also <strong>to</strong>ok the opportunity <strong>to</strong> work in the<br />

labora<strong>to</strong>ries of Prof. Stephen Buchwald, studying the copper-catalysed amidation of<br />

aryl halides. Since September 2004 he has been engaged in research with Prof.<br />

<strong>Jonathan</strong> <strong>Clayden</strong> at the University of Manchester, and the results of these<br />

investigations are embodied in this thesis. All being well, the Author looks forward <strong>to</strong><br />

undertaking a Leverhulme Trust postdoc<strong>to</strong>ral research position under the guidance of<br />

Dr Craig Williams at the University of Queensland.<br />

8


Acknowledgments<br />

I would like <strong>to</strong> thank <strong>Jonathan</strong> for his guidance, support, barbeques and boat trips over<br />

the last three-and-a-bit years. I am also very grateful <strong>to</strong> Andy Payne who supervised<br />

me during my period of work at GSK Harlow, and <strong>to</strong> Bob and Phyllis who made my<br />

stay there much more enjoyable than it would otherwise have been.<br />

I am of course thankful <strong>to</strong> the technical staff at the University of Manchester,<br />

especially Val, Gareth and Rohana; and <strong>to</strong> Phil and John at GSK. Madeleine and Jim<br />

have always been very helpful when I’ve been stuck squinting at the crystal structures<br />

they always seem able <strong>to</strong> solve. Johanna and Eric also deserve a special mention for<br />

their assistance with everything EPR, and for their willingness <strong>to</strong> let me taint their<br />

machines with organic compounds.<br />

I have enjoyed spending the past years with members of the <strong>Clayden</strong> group both inside<br />

and outside of lab. Particular thanks <strong>to</strong> Betson, Wes, and Tim for proof reading and<br />

generally being great friends and lab-neighbours. I am also incredibly grateful <strong>to</strong><br />

Nuria, Beckii, Olga and James for the conversations, and over the past months for<br />

allowing me <strong>to</strong> experiment vicariously. Cousin It for being generally great, Heloise for<br />

being a wonderful hostess, Lluis for general mischief in Japan, Worral for his company<br />

through the night-time hours (both lab and pub), Vas for being Vas, and Simon for his<br />

enthusiastic morning greetings and Glas<strong>to</strong>. I am been grateful <strong>to</strong> everyone else for<br />

contributing <strong>to</strong> a friendly atmosphere, in particular Abby, Riz, Tom, Damo, Steve,<br />

James, Jordi, Boris, Pickworth, and Uli Uli Uli Uli.<br />

I have been very fortunate <strong>to</strong> have had a string of insightful men<strong>to</strong>rs over the years; <strong>to</strong><br />

them I am indebted for the care and time they have taken in educating me and my<br />

peers. I am grateful <strong>to</strong> my parents for always supporting me in everything I do, and<br />

being there <strong>to</strong> offer advice or support whenever I need it.<br />

Special thanks of course go <strong>to</strong> Giudi, for far <strong>to</strong>o many reasons <strong>to</strong> list. Her support,<br />

<strong>to</strong>lerance and love over the last three years have helped me <strong>to</strong> get through the lows and<br />

embrace the highs.<br />

– LLFF<br />

9


Abbreviations & Conventions<br />

Ac acetate<br />

AD Sharpless asymmetric dihydroxylation<br />

Anh. Anhydrous<br />

AIBN azobisisobutyronitrile<br />

Ar aryl<br />

aq aqueous<br />

BHA butylated hydroxyanisole / 2,6-di-tert-butyl-4-methoxyphenol<br />

Bn benzyl<br />

Bu butyl<br />

t-Bu tert-butyl<br />

n-Bu n-butyl<br />

s-Bu sec-butyl<br />

Bz benzoyl<br />

c. circa<br />

cat. catalytic<br />

CDI 1,1’-carbonyldiimidazole<br />

c-Hex cyclohexyl<br />

CI chemical ionisation mass spectroscopy<br />

CIP contact ion pair<br />

CIPE complex-inducted proximity effect<br />

conv. conversion of starting material<br />

COSY<br />

1 H- 1 H correlation spectroscopy<br />

Δ heat under reflux<br />

DCE dichloroethane<br />

DEPT dis<strong>to</strong>rtionless enhancement by polarisation transfer<br />

DIC N,N'-Diisopropylcarbodiimide<br />

DIAD diisopropyl azodicarboxylate<br />

DMAP N,N-dimethyl-4-aminopyridine<br />

DMF N,N-dimethylformamide<br />

DMPU dimethylpropyleneurea / dimethylhexahydro-2-pyrimidinone<br />

d.r. diastereomeric ratio<br />

10


EDC 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride<br />

e.e. enantiomeric excess<br />

e.r. enantiomeric ratio<br />

EI electron impact<br />

ESI electrospray ionisation<br />

eq equivalent<br />

Et ethyl<br />

ET electron transfer<br />

EWG electron-withdrawing group<br />

FT-IR Fourier transform infrared spectroscopy<br />

HMQC heteronuclear multiple quantum coherence<br />

HPLC high performance liquid chroma<strong>to</strong>graphy<br />

HRMS high resolution mass spectroscopy<br />

IPA isopropyl alcohol<br />

J coupling constant in Hertz<br />

KIE kinetic iso<strong>to</strong>pe effect<br />

LDA lithium diisopropylamide<br />

mCPBA meta-chloroperbenzoic acid<br />

Me methyl<br />

MO molecular orbital theory<br />

mpt melting point<br />

MS mass spectroscopy<br />

MTPA α-methoxy-α-trifluoromethylphenylacetate<br />

NMR nuclear magnetic resonance<br />

NMO N-methylmorpholine N-oxide<br />

nr no reaction<br />

Ox* oxazoline<br />

Ph phenyl<br />

PMA dodecamolybdophosphoric acid (TLC stain)<br />

Pl polar<br />

ppm parts per million<br />

i-Pr isopropyl<br />

Pyr. pyridine<br />

11


RDS rate determining step<br />

R f<br />

RC<br />

rt<br />

SIP<br />

SM<br />

sat.<br />

TA<br />

Tf<br />

Thd.<br />

THP<br />

THF<br />

TLC<br />

TMS<br />

retention fac<strong>to</strong>r<br />

radical combination<br />

ambient temperature<br />

solvent separated solvent pair<br />

starting material<br />

saturated<br />

Donohoe tethered aminohydroxylation<br />

triflate/trifluoromethanesulfonate<br />

thermodynamic<br />

tetrahydropyran<br />

tetrahydrofuran<br />

thin-layer chroma<strong>to</strong>graphy<br />

trimethylsilyl<br />

TMANO trimethylamine N-oxide<br />

TMP 2,2,6,6-tetramethylpiperidine<br />

UV ultraviolet<br />

w/w weight percentage<br />

All compounds synthesised by the Author were the single enantiomers shown unless<br />

labelled racemic (±) when their relative geometries and designated by an asterisk (R*,<br />

S*). Enantiomeric purity is measured as the enantiomeric ratio (e.r.) where possible,<br />

but enantiomer excess (e.e.) is quoted when the method was used for its determination<br />

is unclear. Numbering conventions in the main body and experimental sections are:<br />

<strong>The</strong> suffix <strong>to</strong> compound numbers 100, 101, 102 & 165 refers <strong>to</strong> the aromatic<br />

substitution; for example 100a, 101a, 102a and 165a are all phenyl (C 6 H 5 ) derivatives.<br />

12


"To expect a scientist <strong>to</strong> do philosophy of science, is like expecting a fish<br />

<strong>to</strong> do hydrodynamics." Imre Laka<strong>to</strong>s<br />

13


Chapter 1: Introduction<br />

Chapter 1 – Dearomatising Additions in Organic Synthesis<br />

1.1 Introduction<br />

Aromaticity and aromatic compounds have enjoyed a central role in chemistry<br />

throughout its his<strong>to</strong>ry. Since Kekule’s first visions, the cyclic delocalised systems<br />

have captured the imagination of chemists of all flavours, and their predictable<br />

behaviour means that no undergraduate course goes without early examples of the<br />

manipulation of aromatic compounds. Much work in organic synthesis has involved<br />

the functionalisation of the aromatic nucleus, and it is fundamental <strong>to</strong> the reper<strong>to</strong>ire of<br />

any synthetic chemist. Arenes are widely available, highly stable and affordable<br />

starting materials, and this pool of available building blocks may extended by<br />

technologies such as cross-coupling, ortho-lithiation, and electrophilic or nucleophilic<br />

substitution.<br />

This thesis concerns the development of a dearomatising functionalisation of a<br />

benzenoid system, and a brief survey of existing methods follows. A recent review by<br />

Ortiz et al. 1 covers a range of methods for dearomatising anthracenes, naphthalenes<br />

and benzene systems. <strong>The</strong> following survey will study reductive intermolecular<br />

methods for the nucleophilic dearomatisation of the benzene system, although some<br />

exceptions have been made where they are of particular relevance or interest.<br />

1.2 Dearomatisation with Electrophilic Functionalisation<br />

1.2.1 Von Auwers-Woodward<br />

When subjecting ortho- and para- alkylated phenols <strong>to</strong> Reimer-Tiemann conditions, 2<br />

Von Auwers isolated significant amounts of cyclohexadienone 2, as well as the<br />

expected phenolic aldehyde 1 (Scheme 1.1). 3 First reported in 1902, this appears <strong>to</strong> be<br />

the first dearomatisation of a benzene nucleus. Like phenol 1, dienone 2 is the product<br />

of addition of dichlorocarbene <strong>to</strong> p-cresol, but unlike its regioisomer the product of<br />

para-addition is unable <strong>to</strong> undergo rearomatisation, but must abstract a pro<strong>to</strong>n from<br />

elsewhere <strong>to</strong> become dienone 2.<br />

15


1.2 – Electrophilic dearomatisation<br />

HO<br />

NaOH, CHCl 3<br />

OHC<br />

HO<br />

1<br />

+<br />

O<br />

2<br />

CHCl 2<br />

NaOH, CHCl 3<br />

CHCl 2<br />

HO<br />

O<br />

3 80%<br />

Scheme 1.1 – the first dearomatising addition by Von Auwers 3<br />

Other than providing mechanistic evidence for the Reimer-Tiemann reaction, this<br />

dearomatisation remained unexplored until Woodward proposed its use <strong>to</strong> introduce<br />

the angular methyl group in the synthesis of sterols. Tetralin 4 was subjected <strong>to</strong> the<br />

conditions, giving both the aldehyde and the desired dienone 5 (Scheme 1.2a). 4 Upon<br />

gentle hydrogenation alcohol 6 was obtained, whilst stronger conditions led <strong>to</strong><br />

dehalogenation. This observation led Woodward <strong>to</strong> postulate the possible biosynthesis<br />

of the male hormone oesterone from andros<strong>to</strong>ne (Scheme 1.2b).<br />

a)<br />

H 2<br />

CHCl 2<br />

HO<br />

4<br />

NaOH, CHCl 3<br />

O<br />

OHC<br />

CHCl 2<br />

15%<br />

5<br />

+<br />

HO<br />

6<br />

b)<br />

Me<br />

O<br />

HO<br />

50%<br />

Me O<br />

proposed<br />

biosynthesis<br />

Me<br />

HO<br />

HO<br />

oestrone<br />

andros<strong>to</strong>ne<br />

Scheme 1.2 – a) introduction of the angular methyl group b) proposed biosynthesis 4<br />

1.2.2 <strong>The</strong> Birch reduction<br />

<strong>The</strong> most widely used dearomatising reaction is the dissolving metal reduction<br />

discovered by Birch. 5 <strong>The</strong> reduction yields the product of the 1,4-addition of hydrogen<br />

across the arene system, giving the non-conjugated diene 8 (Scheme 1.3). <strong>The</strong><br />

formation of the thermodynamically unfavoured 1,4-diene is due <strong>to</strong> the kinetically-<br />

16


Chapter 1: Introduction<br />

controlled pro<strong>to</strong>nation of cyclohexadienyl anion 7, arguments for which mostly<br />

resemble the principle of least motion analysis. 6 Relatively recent MO calculations of<br />

7 by Zimmerman show that electron density is highest at the centre of the conjugated<br />

H<br />

H<br />

system. 7 Li, NH 3<br />

ROH<br />

ROH, −33 °C<br />

7 8<br />

~70%<br />

Scheme 1.3 – the Birch reduction<br />

<strong>The</strong> regioselectivity of the reaction of substituted benzenes is highly dependent upon<br />

the substituent, but often follows the Birch rule, 7 in which the product is the<br />

“regioisomer with the maximum number of alkyl and/or alkoxy groups on the residual<br />

double bonds.” <strong>The</strong> reason for this empirical rule becomes clear when considering the<br />

most stable radical anion resulting from the first reduction, allowing the above<br />

statement <strong>to</strong> be generalised; electron donating groups result in vinylogous products<br />

(9), 8 whilst electron withdrawing groups give allylic products (11). 9<br />

OMe<br />

OMe<br />

Li, NH 3 , THF<br />

t-BuOH, −33 °C<br />

9<br />

75%<br />

O<br />

NMe 2<br />

K (2.2 eq), NH 3<br />

t-BuOH (1 eq)<br />

THF, −78 °C<br />

OK<br />

NMe 2<br />

NH 4 Cl<br />

O<br />

NMe 2<br />

10 11<br />

92%<br />

Scheme 1.4 – regiomeric products of the Birch reduction<br />

As expected, more electron deficient arenes are reduced more rapidly, and a<br />

conjugated electron withdrawing group, such as an ester, gives stable enolates (10)<br />

which may be quenched with a range of electrophiles. If there is a source of<br />

asymmetry in the enolate, then preferential attack may occur on one of the<br />

diastereo<strong>to</strong>pic faces. This source of diastereoselectivity may be inherent in the<br />

substrate (Scheme 1.5) or by means of a chiral auxiliary (Scheme 1.6, next section).<br />

<strong>The</strong> former was demonstrated in House’s study of the synthesis of gibberellins, when<br />

the stereochemistry of the quench was shown <strong>to</strong> be determined solely by the bulk of<br />

17


1.2 – Electrophilic dearomatisation<br />

the γ-carboxylic acid; stereospecifically forming diastereomeric tetrahydroindenes 12a<br />

and 12b.<br />

H<br />

H<br />

i) Li, NH 3 , THF<br />

MeO<br />

CO 2 H<br />

H<br />

CO 2 H<br />

ii) MeI<br />

MeO<br />

Me<br />

H<br />

CO2 H CO 2 H<br />

12a 51%<br />

H<br />

i) Li, NH 3 , THF<br />

H<br />

MeO<br />

CO 2 H<br />

H<br />

CO 2 H<br />

ii) MeI<br />

MeO<br />

Me<br />

CO2 H<br />

12b<br />

H<br />

CO 2 H<br />

46%<br />

Scheme 1.5 – facial selectivity in gibberellin synthesis 10<br />

1.2.2.a Asymmetric Birch reductions<br />

<strong>The</strong> development of stereocontrol in the Birch reduction by use of chiral auxiliary was<br />

pioneered by Schultz and co-workers, and was reviewed in 1999. 9 Schultz used a<br />

chiral amide <strong>to</strong> activate the aromatic ring <strong>to</strong> reduction, and the resulting enolates (14)<br />

trapped by a facially selective electrophilic quench (Scheme 1.6).<br />

13<br />

O<br />

N<br />

OMe<br />

OMe<br />

Na/K, NH 3 ,<br />

t-BuOH<br />

THF, −78 °C<br />

N<br />

O<br />

O M<br />

14<br />

OMe<br />

−78 °C<br />

MeI<br />

i) rt<br />

ii) −78 °C<br />

MeI<br />

O<br />

Me<br />

O<br />

Me<br />

N<br />

N<br />

OMe<br />

OMe<br />

OMe<br />

85%<br />

15 dr 260:1<br />

product of chelate<br />

OMe<br />

80%<br />

dr 99:1<br />

16<br />

product in absence of chelate<br />

11<br />

Scheme 1.6 – use of a chiral auxiliary in the Birch reduction<br />

When used in conjunction with an ortho-methoxy group (13), the proline-derived<br />

amide is found <strong>to</strong> offer excellent diastereomeric excesses. At low temperature,<br />

chelation by metal ions or ammonia allows the trapping enolate 14 giving diene 15.<br />

However, raising the temperature <strong>to</strong> 25 °C is afforded the diastereomer 16 in good<br />

18


Chapter 1: Introduction<br />

diastereomeric excess; this is believed <strong>to</strong> be formed due <strong>to</strong> the disruption of chelate 14,<br />

allowing the diastereomeric product <strong>to</strong> be formed.<br />

<strong>The</strong> methoxy group serves two purposes; firstly an ortho-substituent is essential <strong>to</strong><br />

desymmetrise the enolate intermediate, and secondly it participates in the internal<br />

chelate 14. This was demonstrated by replacement of the methoxy group with a<br />

methyl one, giving the thermodynamic diastereomer related <strong>to</strong> diene 16. <strong>The</strong><br />

replacement of the prolinol methoxy has minimal effect, showing that it plays no<br />

significant role. 11 Reduction products 15 and 16 are amenable <strong>to</strong> a wide range of<br />

functional group manipulations; the diene portion may be further reduced or<br />

functionalised, whilst removal of the auxiliary permits facile lac<strong>to</strong>nisation.<br />

Pioneering work on the asymmetric Birch reduction of aromatic heterocycles has also<br />

been performed in the labora<strong>to</strong>ries of Donohoe, however this is outside of the scope of<br />

this survey. 12<br />

1.3 Nucleophilic Dearomatisation without Heavy Metals<br />

Unlike the electrophilic Birch reduction, nucleophilic dearomatisation permits the<br />

concomitant nucleophilic and electrophilic functionalisation of an aromatic system,<br />

allowing two stereocentres <strong>to</strong> be formed in a single reaction. <strong>The</strong> methods presented<br />

below generally employ strong π-accep<strong>to</strong>rs <strong>to</strong> lower the energy of the benzene LUMO;<br />

however the functional groups which promote the addition are often prone <strong>to</strong> reaction<br />

themselves which is minimised by judicious choice of reaction conditions, or by the<br />

use of steric bulk <strong>to</strong> protect the functional groups.<br />

<strong>The</strong> reactions often suffer from rearomatisation of reaction intermediates, poor<br />

chemoselectivity and poor regioselectivity during either the nucleophilic or<br />

electrophilic functionalisation. <strong>The</strong> first section presents some examples of the<br />

dearomatisation of benzenoid rings, the next explores Meyers’ dearomatisation of<br />

naphthyloxazolines, before catalytic methods for dearomatisation are briefly discussed.<br />

19


1.3 – Nucleophilic dearomatisation<br />

1.3.1 Favourable electron withdrawing groups<br />

1.3.1.a Nitro group<br />

Perhaps one of the most widely explored electron withdrawing groups in aromatic<br />

chemistry is the relatively inert and strongly π-withdrawing nitro group. In light of the<br />

significant body of work performed with respect <strong>to</strong> Meisenheimer complexes, it is<br />

perhaps surprising that the dearomatisation of nitrobenzenes has only been generally<br />

achieved by borohydride species, which is beyond the scope of this discussion. 1<br />

However, Bar<strong>to</strong>li and co-workers were able <strong>to</strong> achieve the dearomatisation of<br />

dinitrobenzene by Grignard reagents.<br />

O 2 N<br />

17<br />

NO 2<br />

i) RMgX (2 eq)<br />

THF, −70 °C 10 min<br />

ii) NaOCl<br />

O 2 N<br />

R<br />

18<br />

NO 2<br />

R<br />

+ 17<br />

entry R 18 / % 17 / %<br />

a Me 56 31<br />

b Et 30 37<br />

c Me 3 SiCH 2 18 50<br />

d Bn 20 53<br />

e PhCH 2 CH 2 34 38<br />

f CH 2 =CH(CH 2 ) 2 36 37<br />

13<br />

Table 1.1 – dearomatisation of dinitrobenzene<br />

Dearomatisation of dinitrobenzene with Grignard reagents (Table 1.1) suffers from<br />

competing reduction of the nitro group, which upon an oxidative workup returns<br />

starting material 17. It was possible <strong>to</strong> minimise reduction by performing the reaction<br />

at low temperature. Interestingly, only trace amounts of the mono-alkylated adduct<br />

were obtained when using a single equivalent of the organometallic, presumably<br />

because the intermediate nitroalkene is significantly more electrophilic than the<br />

nitroarene.<br />

It is proposed that the decrease in dearomatisation with increasing bulk (entries a-c) is<br />

indicative of a single electron transfer (SET) mechanism since a bulky radical would<br />

20


Chapter 1: Introduction<br />

combine more slowly with the aromatic radical anion. ESR studies show the presence<br />

of radical species, although these studies were inconclusive since they were unable <strong>to</strong><br />

show that the radical anion was an intermediate in the dearomatisation rather than<br />

another trace species, or the reduced nitrobenzene.<br />

1.3.1.b Nitrile<br />

Cyano groups are highly susceptible <strong>to</strong> 1,2-addition reactions with organolithiums, and<br />

the lithiation of benzonitriles normally requires the use of a non-nucleophilic base. 14<br />

However, in an extension of his dearomatisation of cyanonaphthalenes, 15 Ortiz found<br />

that at very low temperatures, lithiated phosphine boranes (20) underwent<br />

dearomatising addition in a 1,6-fashion.<br />

CN<br />

CN<br />

PPh 2 BH 3<br />

Li 20<br />

CN<br />

H 2 O<br />

PPh 2 BH 3<br />

21<br />

65%<br />

THF, HMPA (6 eq)<br />

−90 °C 12 hr<br />

PPh 2 BH 3<br />

RX<br />

PPh 2 BH 3<br />

R<br />

CN<br />

22<br />

R = Me, 97% 1:1.2 dr<br />

= allyl, 97% 1:1.5 dr<br />

= Bn, 77% 97:1 dr<br />

16<br />

Scheme 1.7 – dearomatisation of benzonitrile<br />

<strong>The</strong> above summary shows that alkylation of the dearomatised intermediate proceeds<br />

in much better yield than simple pro<strong>to</strong>nation; indeed most of the remaining mass<br />

balance accompanying 21 (32%) were products of 1,2-addition. Ortiz does not<br />

comment on these results which apparently show the electrophilic addition affecting<br />

the prior nucleophilic addition, which could indicate a reversible reaction. <strong>The</strong><br />

dearomatisation was highly regioselective with no 1,4-addition observed;<br />

dearomatisation was also achieved for 3-chloro (79%) and 3-methyl (36%)<br />

benzonitriles <strong>to</strong> give 1,3 dienes similar <strong>to</strong> 21.<br />

21


1.3 – Nucleophilic dearomatisation<br />

1.3.1.c Strained amides<br />

Tertiary amides are often used <strong>to</strong> direct metalation of aromatic rings and are not prone<br />

<strong>to</strong> direct addition. During conformational studies of secondary amides, <strong>Clayden</strong> found<br />

that tetramethylpiperidenes 22 underwent conjugative addition rather than the expected<br />

ortho-lithiation.<br />

R R’ E 23 / %<br />

O N<br />

O N<br />

i) RLi, THF R<br />

ii) E<br />

E<br />

R'<br />

R<br />

22 23<br />

Table 1.2 – dearomatising addition <strong>to</strong><br />

TMP amides 17,18<br />

a s-Bu H MeI 55 *<br />

b Me OMe MeI 22<br />

c n-Bu OMe MeI 40<br />

d s-Bu OMe MeI 71 *<br />

e s-Bu OMe EtI 51 *<br />

f s-Bu OMe BnBr 61 *<br />

g s-Bu OMe Me 2 CO 32 *<br />

h s-Bu OMe NH 4 Cl 76 *<br />

* 3:1 exocyclic d.r.<br />

Only trans-adducts were isolated and both nucleophilic and electrophilic additions<br />

were highly regio- and stereoselective, with the mass balance mostly identified as<br />

starting material. <strong>The</strong> unexpected reactivity is attributed <strong>to</strong> an amide in which the<br />

ground state is destabilised by <strong>to</strong>rsional strain, reducing the n N →π* C=O interaction and<br />

allowing the carbonyl <strong>to</strong> accept more electron density from the aromatic system, whilst<br />

direct addition is prevented by the TMP geminal dimethyl groups. Whilst the reduced<br />

π* interaction is not observed in the IR absorption of amides 22 (1620 cm -1 ) this<br />

appears <strong>to</strong> be the most likely explanation.<br />

22


Chapter 1: Introduction<br />

O<br />

Ar<br />

Cl<br />

TMP<br />

NaH<br />

O<br />

Ar<br />

N<br />

22<br />

12-34%<br />

O<br />

N<br />

O<br />

NH<br />

s-Bu<br />

TMSI, CH 2 Cl 2<br />

rt, 48 hr<br />

s-Bu<br />

OMe<br />

23'<br />

O<br />

24<br />

50%<br />

18<br />

Scheme 1.8 – installation & cleavage of the TMP group<br />

In light of the good regio- and stereoselectivity, this dearomatisation compares<br />

favourably with the other methods. However amides 22 could only be made in very<br />

low yield from the acid chloride (Scheme 1.8) and are very sensitive <strong>to</strong> strong acid –<br />

presumably with respect <strong>to</strong> 24 – limiting options for workup. Controlled hydrolysis<br />

could be achieved upon treatment with iodotrimethylsilane in the dark, but this gave<br />

only a modest yield of the secondary amide 24.<br />

23


1.3 – Nucleophilic dearomatisation<br />

1.3.1.d Bulky esters<br />

When studying S N Ar reactions of aromatic esters, Miyano found that BHA benzoate<br />

25 underwent conjugative addition <strong>to</strong> the aromatic ring for a range of organolithiums<br />

and Grignard reagents.<br />

OMe<br />

i) RM, THF<br />

OMe<br />

OMe<br />

R<br />

COBHA −78 °C<br />

COBHA<br />

COBHA<br />

ii) NH 4 Cl<br />

+ +<br />

iii) DDQ<br />

R R<br />

25 26 27 28<br />

entry RM 26 / % 27 / % 28 / %<br />

a t-BuMgBr * 74 – –<br />

b BnMgBr * 76 – –<br />

c BnLi 71 – –<br />

d n-BuLi – – 70<br />

e n-BuLi ‡ 6 29 42<br />

f i-PrLi 14 57 –<br />

g t-BuLi 33 – 50<br />

h t-BuLi ‡ 45 – 16<br />

i allyl-Li 73 – –<br />

j Me 3 SiLi ‡ 85 – –<br />

k PhLi – – 85<br />

l n-BuMgBr * – – 93<br />

m i-PrMgBr * – – 92<br />

* reactions in diethyl ether at rt ‡ THF-HMPA solvent (4:1)<br />

19<br />

Table 1.3 – dearomatisation-oxidation of aryl esters<br />

COBHA<br />

Whilst exclusive substitution (S N Ar) of the methoxy group was observed in a number<br />

of instances (entries k-m) the bulky ester both resists direct addition and promotes 1,4-<br />

and occasionally 1,6-addition <strong>to</strong> the unsaturated system. <strong>The</strong> dearomatised compounds<br />

could not be isolated since they were unstable <strong>to</strong> chroma<strong>to</strong>graphy, and were instead<br />

oxidised and characterised as rearomatised adducts 26 and 27. It seems that the<br />

reaction is sensitive <strong>to</strong> both the nature of the organometallic and the reaction<br />

24


Chapter 1: Introduction<br />

conditions, although the data allow few direct comparisons <strong>to</strong> be made, and it is<br />

unclear if the results presented have been optimised.<br />

Miyano et al. propose a SET mechanism for this dearomatisation stating that<br />

carbanions have an electron donating ability which follows Bn > allyl- >> t-Bu > i-Pr<br />

> Bu >> Ph, and is consistent with their results. 19 <strong>The</strong>y cite Bar<strong>to</strong>li as the source of<br />

this data, who had used oxidation potentials of Grignard reagents <strong>to</strong> propose electron<br />

donating ability i-Pr > Bn ≥ Et > Me >>Ph; 20 contradicting Miyano. Miyano also cites<br />

Yamamo<strong>to</strong>, who used ionisation potentials of organostannanes <strong>to</strong> infer an electron<br />

donating ability allyl >> n-Bu > vinyl. 21 Aside from the data appearing <strong>to</strong> disagree<br />

with the conclusions of the authors, they also fail <strong>to</strong> note Yamamo<strong>to</strong>’s advice that<br />

“there must be an argument against extending this substituent order of ionization<br />

potential for organotins <strong>to</strong> that for organocoppers,” when applying these data.<br />

Further evidence of an SET mechanism is evidenced in the especially high yield<br />

resulting from addition trimethylsilyllithium (entry j), a species which has been used as<br />

single electron reductant for the production of EPR spectra. However, many other<br />

dearomatisations have occurred with silicon nucleophiles in good yield (vide infra)<br />

without stimulating thoughts of an SET reaction.<br />

25


1.3 – Nucleophilic dearomatisation<br />

1.3.2 Dearomatising additions <strong>to</strong> oxazolines<br />

1.3.2.a Pyridyloxazolines<br />

During the attempted ortho-lithiation of 3-pyridyl oxazoline 30, Meyers and coworkers<br />

isolated dihydropyridine 31, the product of nucleophilic addition (Scheme<br />

1.9).<br />

E<br />

N<br />

O<br />

N<br />

i) RLi<br />

X<br />

ii) E +<br />

O<br />

N<br />

i) RLi,<br />

trace H 2 O<br />

N<br />

ii) E +<br />

N<br />

H<br />

30 31<br />

R<br />

H<br />

O<br />

N<br />

82-100%<br />

R = Ph, Me, n-Bu, t-Bu<br />

Scheme 1.9 – unexpected dearomatising addition <strong>to</strong> pyridine 22<br />

Use of a chiral oxazoline 32 was found <strong>to</strong> impart good diastereoselectivity giving<br />

carbamates 33 in high diastereomeric purity (Table 1.4). Nucleophilic addition was<br />

also possible for Grignard nucleophiles (entries d, e).<br />

N<br />

O<br />

N<br />

Ph<br />

OMe<br />

i) Nu-M<br />

ii) ClCO 2 Me<br />

Nu<br />

32 COOMe 33<br />

N<br />

O<br />

N<br />

Ph<br />

entry Nu-M T / °C Yield / % d.r.<br />

a MeLi –45 79 93 : 7<br />

b MeLi –78 79 94 : 6<br />

c n-BuLi –78 92 97 : 3<br />

d MeMgCl 0 88 91 : 9<br />

e n-BuMgCl 0 98 95 : 5<br />

H<br />

OMe<br />

Table 1.4 – asymmetric dearomatising addition <strong>to</strong> pyridines 23<br />

1.3.2.b Addition <strong>to</strong> achiral naphthyloxazolines<br />

Meyers and co-workers later managed <strong>to</strong> extend this reaction <strong>to</strong> carbocycles in the<br />

form of naphthalene 34 (Table 1.5). 24<br />

Whilst the first reactions were discovered for<br />

26


Chapter 1: Introduction<br />

chiral oxazolines, 25 initial development focused on racemic 1-naphthyloxazoline 34. 26<br />

No mention of the dearomatisation of naphthyloxazolines by Grignard reagents has<br />

been found.<br />

O<br />

N<br />

NuLi<br />

O<br />

NLi<br />

Nu<br />

MeI<br />

O<br />

N<br />

Me<br />

Nu<br />

34 35 trans-36<br />

entry NuLi T / °C Yield / % trans : cis-36<br />

a MeLi –20 65 >99 : 1<br />

b n-BuLi –45 90 >99 : 1<br />

c s-BuLi –45 94 >99 : 1<br />

d t-BuLi –45 99 >99 : 1<br />

e Li –80<br />

95 >99 : 1<br />

f allyl-Li –80 85 >62 : 38<br />

g PhCH 2 Li –80 91 >99 : 1<br />

h Ph-C≡CCH 2 Li –40 90 70 : 30<br />

i<br />

THPO Li –40 74 84 : 16<br />

j NC-CH 2 Li –80 <strong>to</strong> –10 0 –<br />

k n-Pr-C≡CLi –80 <strong>to</strong> –10 0 –<br />

l 27<br />

Li<br />

OEt<br />

–10 66 * –<br />

* including 16% ke<strong>to</strong>ne<br />

26<br />

Table 1.5 – addition of nucleophiles <strong>to</strong> 1-naphthyloxazolines<br />

<strong>The</strong> addition proceeds with high trans selectivity, induced by attack on the less<br />

hindered face of azaenolate 35. Pro<strong>to</strong>nation of the azaenolate with weak acids such as<br />

alcohols favoured the products of apparent syn addition, believed <strong>to</strong> be due <strong>to</strong><br />

epimerisation <strong>to</strong> the more stable trans adduct (vide infra). Initial studies showed that<br />

the addition of HMPA as deaggregating agent made no difference <strong>to</strong> selectivity or<br />

yields, whilst freshly prepared organolithium gave improved conversion of starting<br />

material. 28<br />

27


1.3 – Nucleophilic dearomatisation<br />

Additions <strong>to</strong> 2-naphthyloxazoline 37 were also successful (Scheme 1.10) but have<br />

been studied less. Oxazolines were also found <strong>to</strong> promote dearomatisation of<br />

anthracenes but not phenyloxazolines. 29,30<br />

37<br />

O<br />

N<br />

i) NuLi, −45 °C<br />

ii) MeI<br />

Nu O Me<br />

N Nu = n-Bu, 90%<br />

s-Bu, 91%<br />

t-Bu, 90%<br />

Scheme 1.10 - additions <strong>to</strong> 2-naphthyloxazoline 26<br />

1.3.2.c Addition <strong>to</strong> chiral naphthyloxazolines<br />

As with chiral pyridyloxazolines, high levels of asymmetry could be introduced <strong>to</strong> the<br />

already highly diastereoselective addition. 31 Enantiomerically pure oxazolines 38 were<br />

subject <strong>to</strong> the same conditions, with the initial addition proceeding in high<br />

diastereoselectivity followed by exclusively trans-addition for alkyl electrophiles<br />

(Table 1.6). Oxazoline cleavage of the major diastereomer (39 <strong>to</strong> 40) also proceeded<br />

with high fidelity and is discussed further in section 3.2. A comprehensive list of<br />

results has been compiled by Ortiz et al. in their recent review. 1<br />

Ph<br />

O<br />

N<br />

OMe<br />

i) NuLi, 2-4 hr<br />

ii) E<br />

Ph<br />

O<br />

OMe<br />

N<br />

E<br />

Nu<br />

i) MeOTf<br />

then NaBH 4<br />

ii) H +<br />

OHC<br />

38 39 40<br />

NuLi E T / °C 39 / % d.r.* 40 † / % e.e. † / %<br />

a n-BuLi MeI –45 97 94 : 6 – –<br />

b n-BuLi (PhS) 2 –45 91 94 : 6 – –<br />

c n-BuLi ClCO 2 Me –45 99 97 : 3 88 88<br />

d MeLi (PhS) 2 –20 56 86 : 14 62 >99<br />

e PhLi MeI –45 99 83 : 17 89 >99<br />

f 32 vinyl-Li MeI –60 79 94 : 6 – –<br />

g 32 vinyl-Li MeI –60 65 89:11 – –<br />

* ratio of adduct 39 <strong>to</strong> that of trans addition from opposite face † from 39<br />

31<br />

Table 1.6 – selected nucleophilic additions <strong>to</strong> chiral 1-naphthyloxazolines<br />

E<br />

Nu<br />

28


Chapter 1: Introduction<br />

Again a large range of nucleophiles and electrophiles were <strong>to</strong>lerated. Temperature was<br />

found <strong>to</strong> have a significant effect on the diastereoselectivity of addition by vinyllithium<br />

(Table 1.6, entries f, g). Studies of protic quenches found that the use of trifluoroacetic<br />

acid (TFA) gave the expected trans-dihydronaphthalene 41 rather than its epimer as<br />

had previously been observed (Scheme 1.11). It is proposed that this is due <strong>to</strong><br />

trifluoroacetate being <strong>to</strong>o weak a base <strong>to</strong> epimerise the allylic stereocentre. Quenching<br />

with TFA led <strong>to</strong> the formation of TFA salt 41 upon workup, which could be reduced <strong>to</strong><br />

give carbinol 42 and is discussed further in section 3.2.1.<br />

Ph<br />

O<br />

N<br />

OMe<br />

i) i-PrLi<br />

ii) TFA<br />

O<br />

H<br />

Ph<br />

O<br />

i-Pr<br />

NH 2<br />

OMe<br />

i) LiAlH 4 , Et 2 O<br />

ii) H 2 O, NaOH<br />

H<br />

OH<br />

i-Pr<br />

38 41<br />

42<br />

73%<br />

d.r. 24:1<br />

Scheme 1.11 – TFA quench of dearomatising addition<br />

It has also been possible <strong>to</strong> perform a tandem addition <strong>to</strong> naphthalene 38 by tethering<br />

an electrophilic site <strong>to</strong> the organolithium, giving an effective stereoselective annulation<br />

<strong>to</strong> yield syn-fused carbocycle 43 in good yield.<br />

Ph<br />

O<br />

N<br />

OMe<br />

i)<br />

Li<br />

Cl<br />

THF −78 °C <strong>to</strong> rt<br />

Ph<br />

O<br />

OMe<br />

N<br />

ii) NH 4 Cl<br />

H<br />

38<br />

43<br />

84%<br />

Scheme 1.12 – annulation by ambident organolithium 33<br />

29


1.3 – Nucleophilic dearomatisation<br />

<strong>The</strong> effect of oxazoline substituents on diastereoselectivity was investigated using 2-<br />

naphthyloxazolines 44 (Table 1.7). This work shows that the C4 substituent was key<br />

<strong>to</strong> determining the stereochemistry of the product (entries a, b, d) whilst the C5<br />

substituent shows minimal effect except when syn <strong>to</strong> the C4 substituent (entry c).<br />

Similar results were seen for 1-naphthyloxazolines in the same study.<br />

Oxz<br />

i) PhLi<br />

ii) MeI<br />

Ph<br />

Oxz<br />

+<br />

Ph<br />

Oxz<br />

44<br />

45a<br />

45b<br />

Entry T / °C Oxz Yield / % 45a : b<br />

Ph<br />

5 4<br />

a –30 O N<br />

OMe<br />

89 90 : 10<br />

Me<br />

b –78 O N<br />

OMe<br />

90 9 : 91<br />

Me<br />

c –78 O N<br />

OMe<br />

93 25 : 75<br />

d –78 O N<br />

OMe<br />

90 9 : 91<br />

Table 1.7 – the effect of oxazoline substituents on diastereoselectivity 31<br />

To explain the high diastereoselectivity, Meyers proposes a bidentate interaction<br />

between the aryloxazoline and organolithium (Scheme 1.13); the two remaining<br />

coordination sites around lithium being occupied by solvent and the alkyl group, and<br />

are free <strong>to</strong> interchange. 34<br />

30


Chapter 1: Introduction<br />

34<br />

Scheme 1.13 – reproduction of Meyers’ proposed reaction intermediates<br />

“<strong>The</strong> two possible complexes should be capable of ligand exchange, placing<br />

R or the solvent (THF) in either of two positions. If the R-Li bond is situated<br />

as shown in 12, then the σ-orbital is aligned parallel <strong>to</strong> the π-system, whereas<br />

in 13, the R-Li σ-orbital is orthogonal <strong>to</strong> the π-system. In a formal sense<br />

reaction from 12 may be viewed as a concerted suprafacial 1,5-sigmatropic<br />

rearrangement from the HOMO (ψ3) of the six-electron system, according <strong>to</strong><br />

Woodward-Hoffman rules <strong>to</strong> furnish 14.”<br />

In the proposed mechanism, coordination <strong>to</strong> the lithium species aligns the σ C-Li orbital<br />

with the aromatic π-system. Meyers provides little evidence <strong>to</strong> support this<br />

mechanism, and there seems <strong>to</strong> be no literature precedent for such a polarised process<br />

<strong>to</strong> be pericyclic. Involvement of a σ C-Li orbital seems unlikely as, although unknown at<br />

the time, the C–Li internuclear axis has very little electron density, and bonding is now<br />

accepted <strong>to</strong> be 80-90% ionic. 35<br />

Instead, lithium could be viewed as holding the<br />

carbanion in place such that the sp 3 n C orbital is aligned with the aromatic π-system.<br />

a) b) Ph<br />

O<br />

H<br />

H<br />

N<br />

OMe<br />

Li 1,5-sigmatropic rgmnt<br />

R<br />

" Ph OMe "<br />

O N<br />

Li<br />

R<br />

48<br />

Scheme 1.14 – Meyers’ pericyclic interpretation of dearomatising addition<br />

<strong>The</strong> absence of an available p-orbital on lithium means that whilst a π-bond is broken,<br />

it cannot be replaced as it would in the rearrangement of pentadiene (Scheme 1.14a).<br />

If we assume that the initial association is not covalent then the product would<br />

resemble adduct 48 (Scheme 1.14b).<br />

31


1.3 – Nucleophilic dearomatisation<br />

Later studies of amino acid-derived oxazolines, which only have one Lewis basic<br />

centre and would not be able <strong>to</strong> form the bidentate chelates, gave some interesting<br />

results.<br />

R<br />

O<br />

N<br />

R'<br />

i) NuLi<br />

ii) MeI<br />

R<br />

O<br />

R'<br />

N<br />

E<br />

Nu<br />

i) MeOTf<br />

then NaBH 4<br />

ii) H +<br />

OHC<br />

E<br />

Nu<br />

52<br />

53<br />

Entry Nu R R’ T / °C 53 / % d.r. e.e. / %<br />

a n-Bu Ph CH 2 OMe –78 97 96 : 4 90<br />

b Ph Ph CH 2 OMe –40 86 83 : 17 78<br />

c n-Bu H i-Pr –78 97 97 : 3 90<br />

d Ph H i-Pr –40 87 87 : 13 74<br />

e n-Bu H t-Bu –78 99 99 : 1 98<br />

f Ph H t-Bu –40 81 95 : 5 90<br />

Table 1.8 – non-chelating vs chelating oxazoline substituents 37<br />

<strong>The</strong> diastereoselectivity of addition <strong>to</strong> the chelating oxazoline (entries a, b) are<br />

comparable <strong>to</strong> those of the oxazoline derived from valine (entries c & d), whilst that of<br />

the oxazoline derived from tert-leucine (entries e & f) is significantly better. Meyers<br />

proposed a new rationale for these monodentate auxiliaries. 37<br />

R<br />

Li<br />

54<br />

Scheme 1.15 – Meyers’ stereochemical rational for “monodentate” oxazolines<br />

In this description, the nitrogen lone pair lies in the plane of the oxazoline and the<br />

bulky C4 substituent favours attack from the opposite face. Complexation with<br />

nitrogen is consistent with the complex-induced proximity effect (CIPE) of Meyers<br />

and Beak, 38 although Meyers does not seem <strong>to</strong> acknowledge this. This simple<br />

explanation could be applied for Meyers’ earlier chiral auxiliary, but until recently<br />

monodentate and bidentate oxazolines were described as having different mechanisms.<br />

O<br />

N<br />

32


Chapter 1: Introduction<br />

<strong>The</strong> amino acid-derived naphthyloxazolines have more recently been found <strong>to</strong> be<br />

superior in the addition of secondary lithium amides, and silyllithiums.<br />

1.3.2.d Heteroa<strong>to</strong>mic nucleophiles<br />

In early investigations, silyllithiums had undergone dearomatising addition <strong>to</strong><br />

bidentate naphthyloxazolines 38 in good yield, but poor diastereoselectivity. 31 It had<br />

been postulated that residual HMPA from formation of the silyllithium was responsible<br />

for this by preventing oxazoline from forming a tight complex with the lithium species<br />

(vide supra). By preparing dimethylphenylsilyllithium from lithium wire, and using<br />

valine-derived monodentate oxazoline 55, the diastereoselectivity of addition was<br />

significantly improved (Table 1.9, entry a).<br />

O<br />

N<br />

i) Me 2 PhSiLi<br />

−78 °C<br />

O<br />

N<br />

E<br />

Bu 4 NF<br />

THF/H 2 O<br />

O<br />

N<br />

E<br />

ii) EX<br />

SiPhMe 2<br />

"70-71%"<br />

55 56<br />

57<br />

entry Solvent EX 56 / % d.r. *<br />

a THF MeI 75 25:75<br />

b Et 2 O-THF (3:1) MeI 76 95:5<br />

c Et 2 O-THF (3:1) n-PrBr 70 97:3<br />

d Et 2 O-THF (3:1) allyl-Br 77 95:5<br />

* exclusively trans-addition<br />

39<br />

Table 1.9 – addition of silyllithiums<br />

Use of a less Lewis-basic solvent, diethyl ether, further improved the<br />

diastereoselectivity of the reaction (entries b-d). Pro<strong>to</strong>desilylation was achieved in<br />

good yield by treatment with tetrabutylammonium fluoride in aqueous THF <strong>to</strong> afford<br />

57 as the major products in >9:1 ratio with the regiomeric alkene.<br />

Meyers and Shimano succeeded in achieving the dearomatising addition of lithium<br />

amides <strong>to</strong> both 1- and 2-naphthyloxazolines before subsequent alkylation (Table 1.10).<br />

HMPA was essential <strong>to</strong> the reaction, although a large excess (10 eq) reduced<br />

33


1.3 – Nucleophilic dearomatisation<br />

diastereoselectivity, whilst DMPU was also found <strong>to</strong> be moderately effective.<br />

Although addition was successful for a number of lithium amides, an equal number did<br />

not show any dearomatisation; including diethylamide, diallylamide and allylamide. It<br />

appears that β-substitution in the lithium amide disfavours addition, as does an<br />

adjacent π-system.<br />

O<br />

N<br />

i) NuLi (3 eq)<br />

HMPA (1.4 eq)<br />

−78 <strong>to</strong> −50 °C<br />

ii) EX<br />

58 59<br />

O<br />

N<br />

E<br />

Nu<br />

>99:1 dr<br />

entry NuLi EX Yield / %<br />

a Me 2 NLi MeI 93 *<br />

b n-BuN(Me)Li MeI 93<br />

c n-C 5 H 11 N(Me)Li MeI 93<br />

d Li-piperidide MeI 95<br />

e Li-piperidide allyl-Br 92<br />

f Li-piperidide BnBr 67<br />

g Li-piperidide CO(OEt) 2 0<br />

h<br />

O<br />

O<br />

NLi<br />

MeI 96<br />

* + 1% 1,6-adduct<br />

40<br />

Table 1.10 – 1,4-addition of lithium amides <strong>to</strong> 1-naphthyloxazolines<br />

One particularly surprising result was that upon quenching with diethyl carbonate no<br />

dearomatisation was observed. This led the authors <strong>to</strong> investigate whether the addition<br />

might be reversible, which was confirmed by the sequential addition of lithium<br />

piperidide and n-butyllithium, which gave only butylated product. That any<br />

dearomatising reaction is under thermodynamic control seems remarkable.<br />

34


Chapter 1: Introduction<br />

It was envisaged that a one-pot hydrolysis of dearomatised adduct 59h would return β-<br />

amino acid 61, but instead a three-step hydrolysis was necessary (Scheme 1.16). <strong>The</strong><br />

ethylene glycol group was found <strong>to</strong> be particularly resilient, but was eventually<br />

removed in concentrated acid before the base-catalysed hydrolysis in the presence of<br />

butylamine gave the free amine 60. Finally, the acid-catalysed hydrolysis of the<br />

oxazoline gave the desired β-amino acid 61.<br />

O<br />

N<br />

59h<br />

N<br />

O<br />

O<br />

i) HCl (conc) rt<br />

ii) NaOH, H 2 O<br />

n-BuNH 2 Δ<br />

O<br />

60<br />

N<br />

CO 2 H<br />

NH 2<br />

HCl (6N)<br />

NH 2<br />

Δ<br />

78%<br />

61<br />

85%<br />

Scheme 1.16 – synthesis of a β-amino alcohol 40<br />

In extension of this work, Shimano and Meyers found that by simply adding a larger<br />

excess of HMPA, they were able <strong>to</strong> entice some of the unreactive lithium amides <strong>to</strong><br />

undergo dearomatisation in a 1,6-manner.<br />

O<br />

N<br />

i) NuLi (1.5 eq)<br />

HMPA (8 eq)<br />

−78 <strong>to</strong> −60 °C 6 hr<br />

O<br />

N<br />

E<br />

O<br />

N<br />

34<br />

ii) EX, −10 °C<br />

62<br />

Nu<br />

63<br />

Nu<br />

E<br />

entry NuLi EX 62 / % d.r. 63 / %<br />

a Bn 2 NLi MeI 88 5:1 5<br />

b Bn 2 NLi BnBr 93 99:1 0<br />

c BnN(Me)Li allylBr 86 50:1 6<br />

d (allyl) 2 NLi MeI 88 5:1 7<br />

e (allyl) 2 NLi MeOTf 92 5:1 0<br />

f (allyl) 2 NLi allylBr 85 99:1 5<br />

g (allyl) 2 NLi BnBr 92 99:1 0<br />

41<br />

Table 1.11 – 1,6-addition of bulky lithium amides <strong>to</strong> 1-naphthyloxazolines<br />

35


1.3 – Nucleophilic dearomatisation<br />

For such a small change in conditions regioselectivity is very high, presumably<br />

because the addition remains under thermodynamic control. This was supported when<br />

lithium amides from Table 1.10 were re-subjected <strong>to</strong> the new conditions still gave 1,4-<br />

adducts. Diastereoselectivities were somewhat less than the previous 1,4-additions, as<br />

would be expected for the formation of such distant stereocentres. Unlike the 1,4-<br />

additions, DMPU did not promote reaction, and adducts 62 were used in the synthesis<br />

of δ-amino acids. 41<br />

1.3.3 Catalytic systems<br />

<strong>The</strong> above systems have been specific <strong>to</strong> a single functional group which remains in<br />

the product. Whilst this may be acceptable if that functionality is desired, or can easily<br />

be removed, it places significant restriction on synthetic design. In principle, a<br />

generally applicable catalytic methods offers clear advantages over a comparable<br />

s<strong>to</strong>ichiometric process.<br />

1.3.3.a Bulky Lewis acid<br />

In a series of communications, Yamamo<strong>to</strong> and Sai<strong>to</strong> have achieved dearomatising<br />

additions <strong>to</strong> aromatic ke<strong>to</strong>nes, 42 aldehydes, 42 acid chlorides 43 and esters. 44 This has<br />

been accomplished by the use of the “carbonyl protec<strong>to</strong>r” ATPH (Table 1.12)<br />

promoting 1,6-addition by acting as a Lewis acid and preventing direct addition <strong>to</strong> the<br />

electron withdrawing group.<br />

36


Chapter 1: Introduction<br />

COR'<br />

i) ATPH, −78 °C<br />

then RM (2-3 eq)<br />

1-12 hr<br />

ii) HCl (conc.)<br />

R<br />

65a<br />

COR'<br />

+<br />

65b<br />

COR'<br />

R<br />

Al<br />

Ph<br />

O<br />

Ph<br />

ATPH<br />

3<br />

entry RM R’ Solvent 65 / % 65a:b<br />

a 42 t-BuLi H PhMe/THF 81 99:1<br />

b 42 n-BuLi H PhMe/THF 47 * 99:1<br />

c 43 MeLi H PhMe 1 -<br />

d 45<br />

e 45<br />

OLi<br />

MeO<br />

H PhMe/THF 23 99:1<br />

OLi<br />

MeO H PhMe/THF 77 99:1<br />

f 44 PhMe 2 SiLi H PhMe 59 99:1<br />

g 42 t-BuLi Me PhMe/THF 93 99:1<br />

h 42 s-BuLi Me PhMe/THF 80 99:1<br />

i 42 n-BuLi Me PhMe/THF 45 99:1<br />

j 45<br />

OLi<br />

MeO<br />

Me PhMe/THF 88 99:1<br />

k 44 PhMe 2 SiLi Me PhMe 44 ** 6:1<br />

l 43 MeLi Cl PhMe 99 2.6:1<br />

m 43 PhLi Cl PhMe 96 99:1<br />

n 43 i-PrMgBr Cl PhMe 71 13:1<br />

o 43 t-BuMgBr Cl PhMe 90 15:1<br />

p 43<br />

OLi<br />

Cl PhMe 75 99:1<br />

MeO<br />

q 44 PhMe 2 SiLi OMe PhMe 34 ‡ 35:13<br />

* + 13% regiomeric 1,3-diene ** + 43% SM ‡+30% SM +35% rearomatised 65a<br />

Table 1.12 – selected dearomatisations by Yamamo<strong>to</strong> et al.<br />

Initial studies showed the reaction <strong>to</strong> be highly sensitive <strong>to</strong> the choice of solvent with a<br />

<strong>to</strong>luene-THF mixture being preferred at first, whilst more the recent work favours<br />

37


1.3 – Nucleophilic dearomatisation<br />

<strong>to</strong>luene alone. In particular, degassed solvent was found <strong>to</strong> be essential, and the use of<br />

aqueous solutions of acid was detrimental <strong>to</strong> the successful isolation of diene; failure <strong>to</strong><br />

observe these measures leads <strong>to</strong> near quantitative rearomatisation. 42 Regioselectivity<br />

of addition is generally very good, but slightly diminished for acid chlorides, this is<br />

rationalised by comparison of the crystal structures of ATPH-PhCHO and ATPH-<br />

PhCOCl which show one of the ortho-carbons <strong>to</strong> be exposed in the latter complex.<br />

Interestingly a number of other differences are observed between the acid chloride and<br />

simple carbonyl complexes; the IR carbonyl stretch for ATPH-PhCOCl is 42 cm -1<br />

lower than the free acid chloride, whereas little difference is reported for the ATPH-<br />

PhCHO complex. 43 This is consistent with the crystal data which shows the C=O in<br />

the ATPH-PhCOCl complex <strong>to</strong> be almost 0.1 Å shorter than the benzaldehyde<br />

complex. Indeed, additions <strong>to</strong> benzoyl chloride seem <strong>to</strong> <strong>to</strong>lerate a larger range of<br />

nucleophiles, including Grignard reagents which do not react with the other systems<br />

studied.<br />

O<br />

i) ATPH, −78 °C<br />

PhMe/THF<br />

then t-BuLi (2 eq)<br />

O<br />

ii) MeOTf<br />

t-Bu<br />

66<br />

68%<br />

d.r. 1:1<br />

O<br />

OMe<br />

i) ATPH, −78 °C<br />

PhMe/THF<br />

then PhMe 2 SiLi (2 eq)<br />

O<br />

OMe<br />

ii) MeOTf<br />

Me 2 PhSi<br />

67<br />

51%<br />

d.r. >95:5<br />

Scheme 1.17 – alkylation of dearomatised ATPH complexes<br />

Whilst the vast majority of the dearomatising additions were γ-pro<strong>to</strong>nated with<br />

concentrated acid, methylation with methyl triflate (Scheme 1.17) was highly<br />

regioselective for α-addition. No stereochemical preference was seen for addition of t-<br />

BuLi/MeOTf <strong>to</strong> ace<strong>to</strong>phenone (66), 42 but addition of the bulky dimethylphenylsilyl<br />

group engendered high diastereoselectivity in the subsequent alkylation, giving silane<br />

67. 44 This is consistent with the observations of 1,6-additions <strong>to</strong> benzonitriles by<br />

Ortiz, who also found that bulky reagents increased facial selectivity in the distal<br />

addition-alkylation (Scheme 1.7).<br />

38


Chapter 1: Introduction<br />

O<br />

i) ATPH, −78 °C<br />

PhMe/THF<br />

then t-BuLi (2 eq)<br />

O<br />

ii) HCl (conc.)<br />

t-Bu<br />

89%<br />

O<br />

Cl<br />

i) ATPH, −78 °C<br />

PhMe<br />

then MeLi (3 eq)<br />

CO 2 H<br />

CO 2 H<br />

69<br />

ii) HCl (conc.)<br />

70<br />

22% 38%<br />

71<br />

Scheme 1.18 – addition <strong>to</strong> functionalised aromatic systems<br />

Some degree of aromatic functionalisation is <strong>to</strong>lerated by the reaction, but only methyl<br />

substituents have been studied and have a significant effect of the regioselectivity of<br />

addition (Scheme 1.18). Dearomatising addition of MeLi <strong>to</strong> dimethylbenzoyl chloride<br />

69, favours 1,4-addition over 1,6-addition (entry l, Table 1.12) and shows poor<br />

regioselectivity in light of the ‘pocket’ found in the crystal structure of the ATPHcomplex<br />

(vide supra). 43 Equally interesting is that no benzylic lithiation is reported for<br />

these reactions; even addition of t-BuLi <strong>to</strong> 69 only gives 1,6-addition without any<br />

reported lithiation.<br />

<strong>The</strong> only attempt <strong>to</strong> induce asymmetry in the reaction is the use of an O-(+)-menthyl<br />

enolate, with gave the dearomatised adduct with 3% d.e. in 77% yield. 45 <strong>The</strong>re has<br />

been no reported use of any chiral analogues of ATPH, this is possibly because<br />

Yamamo<strong>to</strong> has found the complexes <strong>to</strong> be quite labile. 43<br />

39


1.3 – Nucleophilic dearomatisation<br />

1.3.3.b Asymmetric catalysis<br />

Tomioka and co-workers found that bulky alkyl imines 72 reduce direct addition and<br />

preferentially react in a conjugative manner. This process becomes asymmetric in the<br />

presence of chiral diether 73.<br />

Ph<br />

c-Hex<br />

Ph<br />

N<br />

OMe<br />

i) NuLi, OMe 73<br />

ii) H 3 O +<br />

CHO<br />

Nu<br />

NaBH 4<br />

HO<br />

Nu<br />

72<br />

74<br />

Nu = n-Bu, 80%, 91% e.e.<br />

= t-Bu, 79%, 59% e.e.<br />

= Ph, 82%, 94% e.e.<br />

= Me, 19%, 64% e.e.<br />

Scheme 1.19 – asymmetric addition of organolithiums <strong>to</strong> naphthylimines 46<br />

Whilst the reaction is catalytic in diether 73, s<strong>to</strong>ichiometric amounts are required,<br />

proposed <strong>to</strong> be due <strong>to</strong> the azaenolate intermediate competing as a ligand for the<br />

organolithium, reducing the amount of unbound catalyst in solution. Since enolates<br />

are less basic, this work was extended <strong>to</strong> look at the catalytic asymmetric addition <strong>to</strong><br />

BHA ester 75 (Scheme 1.20). In racemic reactions BHA ester 75 was found <strong>to</strong> offer<br />

the best regio- and diastereoselectivity of a number of ester 47 and a 20% loading of the<br />

chiral ether was found <strong>to</strong> be optimal for asymmetric catalysis. Only a small sample of<br />

nucleophiles is reported, and both yields and enantiomeric purities are modest.<br />

O<br />

OBHA<br />

i) NuLi, 73 (20 mol%)<br />

Toluene, −45 °C<br />

HO<br />

Nu<br />

75<br />

ii) LiEt 3 BH<br />

iii) MeOH<br />

iv) NaBH 4<br />

74<br />

Nu = 1-Naphthyl, 75%, 67% e.e.<br />

= Ph, 76%, 75% e.e.<br />

= n-Bu, − %, 21% e.e.<br />

Scheme 1.20 – asymmetric addition of organolithiums <strong>to</strong> naphthylcarboxylates 48<br />

40


Chapter 1: Introduction<br />

1.4 Nucleophilic Dearomatisation of Metal Complexes<br />

High levels of diastereoselectivity have been achieved for a range of nucleophiles and<br />

substrates in the dearomatising addition <strong>to</strong> transition metal-complexed arenes. Most<br />

widely applied are the chemistries of Cr(CO) 3 and Mn(CO) + 3 arene complexes, which<br />

are discussed below.<br />

1.4.1 (η 6 -Arene)Cr(CO) 3<br />

<strong>The</strong> chemistry of arene-tricarbonyl chromium complexes is extensive, allowing a<br />

broad range of functionalisations <strong>to</strong> be performed prior <strong>to</strong> dearomatisation (Scheme<br />

1.21). <strong>The</strong>se are possible due <strong>to</strong> the electron-withdrawing properties of the Cr(CO) 3<br />

R=F, Cl, OR<br />

Nu<br />

R<br />

complex. 49 Cr(CO) 3 Cr(CO) 3<br />

NuLi<br />

R<br />

75 76<br />

Nu<br />

E +<br />

[O]<br />

R<br />

77<br />

E<br />

Nu<br />

Crystal Structure for<br />

Nu = dithiane, R = H<br />

R<br />

Nu<br />

6<br />

Scheme 1.21 – general reactivity of (η -arene)Cr(CO) 3 complexes<br />

A range of carbon nucleophiles may attack the chromium-complexed arene 75 from<br />

the face exo <strong>to</strong> the bulky metal centre, yielding the η 5 -cyclohexadienyl 76 (Scheme<br />

1.21) which has been characterised by crystal structure for the addition of dithiane <strong>to</strong><br />

benzene. 50<br />

Addition <strong>to</strong> the arene complex is relatively facile and labile. This has the advantage of<br />

high levels of selectivity – the thermodynamic product is formed rapidly – but it also<br />

means that regioselectivity is highly substrate-dependent. Furthermore, the addition of<br />

an electrophile other than a pro<strong>to</strong>n will often react with the dissociated nucleophile. In<br />

light of this, many studies have been conducted with dithiane as nucleophile since it<br />

41


1.4 – Metal complexation<br />

has a very slow rate of dissociation. A summary of the preferred regioselectivity of<br />

different nucleophiles and aryl substituents is given in a recent review by Kündig. 51<br />

Electron withdrawing groups on the arene can reduce the backwards reaction,<br />

oxazolines and hydrazines are often use since they also tend <strong>to</strong> direct attack <strong>to</strong>wards<br />

the ortho-position. Below is presented a overview of the possible routes dearomatising<br />

additions might take; the use of these groups in asymmetric synthesis is discussed in<br />

the next section.<br />

R<br />

NuLi<br />

Nu<br />

R<br />

EX<br />

Nu<br />

R<br />

Cr(CO) 3<br />

Cr(CO) 3<br />

75 76<br />

Cr(CO) 3<br />

E<br />

L = CO, MeCN, PhCN<br />

+L<br />

E = Bn, allyl, propargyl<br />

endo migration<br />

R<br />

CO insertion<br />

Nu<br />

R<br />

Nu<br />

E<br />

+ Cr(CO) 2 L 4<br />

E<br />

+ Cr(CO) 2 L 4<br />

Cr(CO) 2 L<br />

E<br />

Cr(CO) 3 L<br />

E<br />

77 O<br />

endo migration L<br />

[O]<br />

Nu<br />

R<br />

Nu<br />

R<br />

E<br />

Cr(CO) 2 L 2<br />

E + Cr(CO) 3 L<br />

O<br />

80<br />

[O]<br />

H 2 (5 bar)<br />

R = H, Nu = dithiane<br />

Nu<br />

R<br />

Nu<br />

O<br />

78<br />

O<br />

79<br />

Scheme 1.22 – dearomatisation strategies of (η -arene)Cr(CO) complexes<br />

6<br />

3<br />

42


Chapter 1: Introduction<br />

Unlike the dearomatising additions discussed in the previous section, the anti addition<br />

of the electrophile is not due <strong>to</strong> the relative steric bulk of the nucleophile, but is due <strong>to</strong><br />

endo migration of the electrophile after alkylation of the chromium centre (76) and can<br />

happen in two ways (Scheme 1.22). In the presence of a suitable ligand such as<br />

ace<strong>to</strong>nitrile, benzonitrile or CO, the electrophile migrates <strong>to</strong> one of the carbonyl<br />

ligands <strong>to</strong> form acylated complex 77 before endo-migration delivers the acyl group<br />

opposite <strong>to</strong> the nucleophile. In the absence of a suitable ligand, or if E is a poor<br />

migra<strong>to</strong>ry group (benzyl, allyl, propargyl) non-acylated products 80 are isolated.<br />

Again, the electrophilic quench is highly sensitive <strong>to</strong> the nature of the substrate and<br />

nucleophile. This facility greatly enhances the scope of the methodology, allowing the<br />

formation of two stereocentres, and the possibility for further functionalisation via the<br />

enolate of acyl diene 78. Furthermore, olefins 79 have been obtained by the addition<br />

of lithium dithiane <strong>to</strong> a benzene complex, followed by in situ hydrogenation. 52<br />

1.4.1.a Asymmetric addition using Cr(CO) 3 complexes<br />

Asymmetry has been successfully introduced by the use of substrate-bound chiral<br />

auxiliaries (Table 1.13) and chiral ligands (Scheme 1.23). Oxazolines 81, derived<br />

from amino alcohols are effective in directing the asymmetric addition <strong>to</strong> the benzene<br />

nucleus; tert-leucine-derived oxazolines (entries d-f) react with greater<br />

diastereoselectivity than for those derived from L-valine, consistent with Meyers’<br />

observations of additions <strong>to</strong> naphthyloxazolines (vide supra). Electrophilic<br />

substitution occurs via addition <strong>to</strong> the metal centre, without acylation since allyl is a<br />

poor migra<strong>to</strong>ry group.<br />

43


1.4 – Metal complexation<br />

R<br />

R<br />

R<br />

O<br />

N<br />

O<br />

N<br />

O<br />

N<br />

i) NuLi<br />

ii) allyl Br, HMPA<br />

Nu<br />

+<br />

Nu<br />

Cr(CO) 3<br />

81<br />

82a<br />

82b<br />

Entry R Nu 82 / % 82a : b<br />

a i-Pr Me 61 96 : 4<br />

b i-Pr n-Bu 54 95 : 5<br />

c i-Pr Ph 48 95 : 5<br />

d t-Bu Me 69 >99 : 1<br />

e t-Bu n-Bu 62 >99 : 1<br />

f t-Bu Ph 51 95 : 5<br />

Table 1.13 – use of chiral oxazoline auxiliaries 53<br />

Asymmetric additions <strong>to</strong> prochiral arene chromium species 84 has been achieved with<br />

chiral ligand 73 (Scheme 1.23), the same ligand used by Tomioka in the asymmetric<br />

addition <strong>to</strong> naphthylesters and imines (Scheme 1.20). This ligand is proposed <strong>to</strong> work<br />

by coordinating either the organolithium nucleophile or the arene-chromium complex.<br />

Whilst an advantage of using a chiral ligand rather than an auxiliary would normally<br />

be that little or no trace of activation remains, the need for a ortho-directing group<br />

seems <strong>to</strong> negate this.<br />

i) RLi Ph<br />

Ph<br />

O N<br />

OMe O N<br />

73 OMe 2 eq<br />

R<br />

ii)<br />

Br<br />

Cr(CO) 3<br />

84<br />

54<br />

Scheme 1.23 – use of an asymmetric ligand<br />

51-67%<br />

65 - 93% e.e.<br />

<strong>The</strong> above methods have been utilised by Kündig et al. in the recent synthesis of both<br />

enantiomers of aceteoxytubipofuran via the key intermediates (–)-86 and (+)-86. In<br />

the key step, two stereocentres, one of them quaternary, are formed (Scheme 1.24).<br />

44


Chapter 1: Introduction<br />

Diene (–)-86 is prepared in high enantiomeric excess from the imine of D-valinol,<br />

whilst enantiomeric diene (+)-86 is obtained by the use of the chiral ether 73, but only<br />

in modest optical purity, which is improved by recrystallisation.<br />

N<br />

OMe<br />

i)<br />

EtO<br />

85<br />

Li<br />

−78°C<br />

CHO<br />

H<br />

OEt<br />

Cr(CO) 3<br />

N<br />

c-Hex<br />

ii) MeI, CO, THF/HMPA<br />

iii) NaOEt, MeI, rt<br />

Ph<br />

i) 85,<br />

Ph<br />

OMe<br />

OMe 73 −40°C<br />

O<br />

(−)-86<br />

CHO<br />

H<br />

53%<br />

>95% e.e.<br />

OEt<br />

Cr(CO) 3<br />

ii) MeI, CO, THF/HMPA<br />

iii) NaOEt, MeI, rt<br />

O<br />

OAc<br />

H<br />

(+)-86<br />

42%<br />

>76% e.e.<br />

O<br />

ace<strong>to</strong>xytubipofuran<br />

55<br />

Scheme 1.24 – complementary enantiomeric syntheses<br />

1.4.2 (η 6 -Arene)Mn(CO) 3 cationic complexes<br />

Cationic arene-tricarbonyl manganese complexes are inherently more reactive than<br />

their neutral chromium counterparts. Whilst this means these species react with a<br />

larger number of nucleophiles, it also causes problems for their handling and<br />

sensitivity <strong>to</strong> reaction conditions. <strong>The</strong> predominant difference <strong>to</strong> the chemistry of<br />

chromium complexes is that the product of nucleophilic addition <strong>to</strong> the manganese<br />

complex (88) is neutral and electrophilic in character, allowing it <strong>to</strong> undergo a second<br />

nucleophilic addition, giving syn-adducts 89 (Table 1.14). Bubbling air in<strong>to</strong> a stirred<br />

solution of the manganese complexes is sufficient <strong>to</strong> obtain the free diene 89.<br />

45


1.4 – Metal complexation<br />

LiAlH 4<br />

R<br />

i) NuLi<br />

or MeLi<br />

+<br />

Mn(CO) 3 Mn(CO) ii) O 2<br />

3<br />

87 88 R = H, Me<br />

Entry R Nu 89 / %<br />

a Me LiCHPh 2 73<br />

b Me LiC(CN)Me 2 58<br />

c Me LiCMe 2 CO 2 Et 43<br />

d H LiCHPh 2 77<br />

e H LiC(CN)Me 2 88<br />

f H LiCMe 2 CO 2 Et 91<br />

R<br />

Nu<br />

±89<br />

51<br />

Table 1.14 – dearomatising additions <strong>to</strong> Mn(CO) 3 complexes<br />

Complex 88 is only moderately electrophilic in character, and attempted isolation<br />

gives mostly rearomatised adduct, with trace amounts of regioisomeric dienes. Unless<br />

reacting with strong nucleophiles as above, activation of 88 is required, and has been<br />

achieved by ligand exchange, forming a cationic η 5 -complex 90 which is more reactive<br />

than the original η 6 -complex. 56 Addition <strong>to</strong> this complex may now be performed by<br />

soft carbon nucleophiles or borohydride.<br />

i) RM<br />

R<br />

iii) NuM<br />

R<br />

Mn(CO) 3<br />

+<br />

ii) NOPF 6<br />

Mn(CO) 2 NO<br />

iv) Me 3 NO<br />

Nu<br />

87<br />

90<br />

±89<br />

Entry RM Nu 89 / %<br />

a MeLi NaCH(CO 2 Et)(COMe) 67<br />

b MeLi NaCH(CO 2 Et)CN 59<br />

c MeLi NaCH(CO 2 Me)(SO 2 Ph) 67<br />

d PhMgBr NaCH(CO 2 Et)(COMe) 66<br />

e PhMgBr NaCH(CO 2 Et)CN 59<br />

f PhMgBr NaCH(CO 2 Me)(SO 2 Ph) 62<br />

g PhMgBr NaBH 4 85<br />

51<br />

Table 1.15 – activation of Mn(CO) 3 complexes<br />

46


Chapter 1: Introduction<br />

A scheme summarising this reactivity is presented below.<br />

87<br />

Mn(CO) 3<br />

+<br />

RM<br />

LiAlH 4<br />

or MeLi<br />

R<br />

E +<br />

R<br />

88<br />

Mn(CO) 3 R = H, Me<br />

NOPF 6<br />

DCM<br />

i) NuM<br />

ii) O 2<br />

"Reactive"<br />

nucleophiles<br />

R<br />

i) NuM<br />

ii) Me 3 NO<br />

R<br />

Mn(CO) 2 NO +<br />

Nu<br />

90 ±89<br />

Scheme 1.25 – synthetic summary of Mn(CO) chemistry<br />

3<br />

Due <strong>to</strong> their more reactive nature, the regioselectivity of addition <strong>to</strong> these arenes is not<br />

as dependent upon the substrate or nucleophile as Cr(CO) 3 complexes. This is<br />

presumably due <strong>to</strong> the irreversible nature of the addition.<br />

1.4.2.a Asymmetric synthesis using Mn(CO) 3 complexes<br />

Due <strong>to</strong> the limitations of the chemistry outlined above, little work has been done<br />

regarding asymmetric additions <strong>to</strong> these complexes. Miles and co-workers found that<br />

use of chiral oxazolidine enolates as nucleophiles results in diastereoselectivity at the<br />

dearomatised centre. 57<br />

(Scheme 1.26).<br />

This technique was extended <strong>to</strong> the synthesis of (+)-juvabione<br />

47


1.4 – Metal complexation<br />

Ph<br />

O<br />

O<br />

N<br />

O<br />

i) LDA<br />

ii)<br />

O<br />

Mn(CO) 3<br />

+<br />

Ph<br />

O<br />

O<br />

O<br />

N<br />

H<br />

O<br />

Mn(CO) 3<br />

d.r. = 3.5:1<br />

O<br />

i) LiAlH 4<br />

ii) p-nitrobenzoyl chloride<br />

iii) Recrystallisation O 2 N<br />

O<br />

H<br />

i) NOPF 6<br />

ii) NaBH 4<br />

>97:3 dr<br />

Mn(CO) 3<br />

O<br />

O<br />

O 2 N<br />

O<br />

H<br />

O<br />

H<br />

Mn(CO) 3<br />

O<br />

COOCH 3<br />

(+)-Juvabione<br />

58<br />

Scheme 1.26 – asymmetric synthesis using Mn(CO) 3 methodology<br />

<strong>The</strong> (η 2 -arene) Os(NH 3 ) 2+ 5 complexes are also susceptible <strong>to</strong> dearomatisation, and this<br />

chemistry has recently been reviewed. 60 However the <strong>to</strong>xic nature of the reagent, and<br />

limited use in asymmetric functionalisation of benzenoid rings means it will not be<br />

discussed.<br />

1.4.3 Pd-mediated dearomatisation<br />

<strong>The</strong> attempted synthesis of homoallyl benzene by the cross-coupling of benzylchloride<br />

and tributylallylstannane (93), yielded tetraene 94 the apparent product of 1,4-addition<br />

(Table 1.16).<br />

48


Chapter 1: Introduction<br />

Cl<br />

R<br />

+<br />

93<br />

SnBu 3<br />

Pd 2 (dba) 3. CHCl 3 (5%)<br />

PPh 3 (40 mol. %)<br />

ace<strong>to</strong>ne, rt<br />

R<br />

94<br />

entry R Time / hr Yield / %<br />

a H 24 80<br />

b 2-Me 32 82<br />

c 3-Me 35 80<br />

d 4-Me 37 76<br />

e 4-Ph 60 71<br />

f 4-i-Pr 34 79<br />

g naphthyl 11 85<br />

61<br />

Table 1.16 – Pd-mediated addition of allyl stannanes<br />

Further inspection of the reaction conditions soon belies the likely oxidative additiontransmetallation-reductive<br />

elimination sequence proposed in Scheme 1.27.<br />

Substitution is presumably seen due <strong>to</strong> the migration of the Pd II species (95 <strong>to</strong> 96) <strong>to</strong><br />

give π-allyl complex 97 before reductive elimination of tetraene 94. Addition has been<br />

possible <strong>to</strong> a range of aromatic compounds, although only allylstannane 93 has been<br />

used as the cross coupling partner.<br />

Cl<br />

Pd(0)<br />

94<br />

97<br />

95<br />

L<br />

Pd II L<br />

Cl<br />

Pd II SnBu 3<br />

Bu 3 SnCl<br />

PdII L<br />

Cl<br />

61<br />

93<br />

Scheme 1.27 - proposed catalytic cycle for allylative dearomatisation<br />

49


1.5 Summary of Methods<br />

In their recent review, Ortiz et al. cover 16 different functional groups that have<br />

promoted nucleophilic addition <strong>to</strong> anthracene, naphthalene and benzene systems. Yet<br />

only the 6 methods above do so for the benzene system, and none offer any significant<br />

enantiomeric enrichment in the product. Whilst transition metal-mediated<br />

dearomatisations have been more synthetically useful, if highly substrate dependent,<br />

the metals used are highly <strong>to</strong>xic and need <strong>to</strong> be treated under careful conditions. <strong>The</strong><br />

most general method discussed is clearly that of Meyers, but is has been restricted <strong>to</strong><br />

naphthyl, pyridyl and anthracene aromatic systems.<br />

It is clear that there is a need for a method <strong>to</strong> achieve the asymmetric dearomatising<br />

bisfunctionalision of benzene-derived systems. <strong>The</strong> following chapter will present the<br />

development of such a methodology.<br />

50


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

Chapter 2 – Dearomatising Additions <strong>to</strong> Aryl Oxazolines<br />

2.1 Establishing a New Reaction<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

Ph<br />

SiO 2<br />

O<br />

N<br />

i) RLi (1.5 eq)<br />

THF:DMPU 25:1<br />

−78 °C<br />

ii) MeI<br />

O<br />

N<br />

Me<br />

R<br />

100a<br />

prepared <strong>to</strong> attempt<br />

dearomatising cyclisation<br />

101a<br />

102a<br />

R = i-Pr, 102a, 61%<br />

s-Bu, 102a', 91%<br />

(dr 4:1)<br />

Scheme 2.1 – first dearomatising additions by Purewal 63<br />

Whilst attempting the dearomatising cyclisation of benzoyl aziridine 100a, Purewal<br />

unintentionally prepared oxazoline 101a. When subjected <strong>to</strong> the conditions of<br />

dearomatising cyclisation 62 this material underwent nucleophilic attack by the<br />

organolithium <strong>to</strong> give dienes 102a’. This was successfully repeated with i-PrLi <strong>to</strong> give<br />

a single diastereomer, confirming that this reaction is highly diastereoselective,<br />

however dienes 102a were described as aziridines in his thesis. 63 A crystal structure<br />

later obtained by Cabedo confirmed the relative stereochemistry of the diene, and<br />

showed it <strong>to</strong> be an oxazoline rather than an aziridine, 64 making a clear link <strong>to</strong> the<br />

chemistry Meyers had developed with 2-naphthyl- and pyridyloxazolines (section<br />

1.3.2).<br />

Personal communication with Meyers confirmed that during the oxazoline research<br />

programme in his labora<strong>to</strong>ries he had been unable <strong>to</strong> achieve dearomatising addition <strong>to</strong><br />

benzenoid aromatics. 36 With this news it was clear that this might be a novel reaction,<br />

differing from Meyers’ in both the oxazoline and co-solvent. This was confirmed by<br />

treating Meyers’ anisoyloxazoline 104b under both sets of conditions. 31<br />

51


2.1 – A new reaction<br />

Ph<br />

OMe<br />

No DMPU<br />

No isolable products<br />

or starting material<br />

O N<br />

OMe<br />

104b<br />

i) i-PrLi, THF<br />

ii) MeI<br />

Ph<br />

O<br />

N<br />

OMe<br />

Ph<br />

O<br />

N<br />

OMe<br />

Me<br />

+ DMPU<br />

OMe<br />

105<br />

24%<br />

OMe<br />

7%<br />

106<br />

Ph<br />

Me<br />

OMe<br />

Ph<br />

Me<br />

OMe<br />

O<br />

N<br />

Me<br />

O<br />

Me<br />

N<br />

22% 4%<br />

OMe<br />

OMe<br />

107 108<br />

Scheme 2.2 – dearomatising addition using the Meyers oxazoline<br />

<strong>The</strong> contrast between the two sets of conditions was very pleasing; a similarly strong<br />

distinction was seen with the 2-phenyl oxazoline. 64 Although the Meyers’ oxazoline<br />

returned a significant amount of diene 105 (stereochemistry assigned by analogy <strong>to</strong><br />

known compounds), it was accompanied by greater amounts of difunctionalised<br />

products 107 and 108. It was clear that the reaction of the Meyers oxazoline was<br />

plagued by side reactions that were not observed with bis-phenyl oxazoline 101a.<br />

para-Anisole 101b was treated under both sets of conditions, and equally stark results<br />

were seen (Scheme 2.3). Addition <strong>to</strong> the electron rich system was very encouraging;<br />

the structure of 102b was again confirmed by crystallography (Scheme 2.6).<br />

Ph Ph<br />

Ph Ph Ph Ph<br />

O<br />

N<br />

OMe<br />

i) i-PrLi (1.5 eq)<br />

THF, −78 °C<br />

ii) MeI<br />

O<br />

N<br />

Me<br />

OMe<br />

O<br />

N<br />

Me<br />

OMe<br />

Additive 102b 103b<br />

None 22% 73%<br />

DMPU 70% 18%<br />

101b<br />

102b<br />

103b<br />

Scheme 2.3 – effect of DMPU on addition <strong>to</strong> aryl oxazolines<br />

52


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

<strong>The</strong>se results show that both the presence of the DMPU co-solvent and the nature of<br />

the oxazoline are important. To see if the reaction could be further improved, a<br />

number of other 2-aryloxazolines were made from chiral pool amino alcohols (the<br />

synthesis of oxazolines is discussed in section 3.1) and treated <strong>to</strong> the reaction<br />

conditions.<br />

i) NuLi (1.5 eq)<br />

DMPU (6 eq), THF<br />

ii) MeI<br />

Me<br />

Nu<br />

R<br />

R<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Me<br />

Ph<br />

OMe<br />

O<br />

N<br />

O<br />

N<br />

O<br />

N<br />

O<br />

N<br />

O<br />

N<br />

101 110 111<br />

109<br />

104<br />

Entry Oxazoline R Nu Diene † (SM) / % Reaction colour*<br />

a 101a H i-Pr 59-70 (4) dark green<br />

b 101a H s-Bu 76-81 ‡ (1) dark green<br />

c 101b OMe i-Pr 58-70 (3) dark green<br />

d 109a H s-Bu 0 (95)<br />

electric blue,<br />

disappears<br />

e 109b OMe s-Bu


2.1 – A new reaction<br />

anticipated that changing <strong>to</strong> a cis geometry would only affect the diastereoselectivity<br />

of the addition, as found by Meyers (section 1.3.2.c).<br />

<strong>The</strong> norephedrine-derived oxazoline 110 (entry f) proved better at promoting the<br />

dearomatising addition than Meyers’ oxazoline (104) had, however it was also<br />

accompanied by benzylic lithiation (114).<br />

Ph<br />

Me<br />

Ph<br />

Me<br />

Ph<br />

Me<br />

Ph<br />

Me<br />

Me<br />

O<br />

N<br />

i) i-PrLi (1.5 eq), DMPU (6 eq)<br />

−78 °C, 30 min<br />

ii) MeI<br />

O<br />

N<br />

Me<br />

+<br />

O<br />

N<br />

Me<br />

+<br />

O<br />

N<br />

Me<br />

40% 12% 5%<br />

110 112 113 114<br />

Scheme 2.4 – dearomatising addition <strong>to</strong> norephedrine-derived oxazoline<br />

Valine-derived oxazolines had been synthetically useful in many asymmetric reactions,<br />

most notably for additions <strong>to</strong> naphthyloxazolines 37 and (η 6 -arene)Cr(CO) 3 species. 53<br />

However, valine-derived oxazolines 111 (entries g, h) showed no significant reaction<br />

with the organolithium, and a translucent reaction solution was seen as opposed <strong>to</strong> the<br />

opaque solutions which had become characteristic of a successful reaction.<br />

<strong>The</strong> high levels of diastereoselectivity, and the potential for use in asymmetric<br />

synthesis was shown by removing the oxazoline moiety, and derivative 115 was shown<br />

<strong>to</strong> be enantiomerically pure by HPLC analysis. Oxazoline removal is described in<br />

section 3.2.<br />

Ph Ph<br />

(p-BrBz)O<br />

O N<br />

Section 3.2.6<br />

OMe<br />

101b 115<br />

O(p-BrBz)<br />

Scheme 2.5 – determination of enantiomeric purity<br />

58%, 5 steps<br />

>99:1 er<br />

54


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

2.1.1 Summary of initial reactions<br />

Whilst the dearomatising addition of organolithiums was possible with three of the five<br />

oxazolines, the anti-diphenyl oxazoline is clearly best at promoting the<br />

dearomatisation. Failure of the cis oxazoline (109) after repeated attempts shows that<br />

the trans geometry is key, whilst the benzylic lithiation of the Meyers (104) and<br />

norephedrine (110) oxazolines indicate that the diphenyl system may be successful due<br />

<strong>to</strong> the mutual hindrance of C4 and C5. Mechanistically, the pseudo-C 2 nature of<br />

oxazolines 101 offers a very appealing rationale for the high levels of<br />

diastereoselectivity observed, although equally high diastereoselectivity was seen with<br />

anti-oxazolines 104 and 110.<br />

<strong>The</strong> other key component in the reaction is the DMPU co-solvent. DMPU has been<br />

used extensively in organolithium chemistry, largely as a less <strong>to</strong>xic substitute for<br />

HMPA. 65 It is a Lewis basic ligand for lithium, donating electron density through its<br />

oxygen lone pairs, purportedly making the organolithium more reactive through<br />

deaggregation, which is discussed at the end of the chapter.<br />

Oxazolines are traditionally used <strong>to</strong> direct ortho-metalation, and Scheme 2.3 shows<br />

that it might be possible <strong>to</strong> tune the reactivity of the aromatic ring, permitting<br />

functionalisation before dearomatisation. Addition of a range of Grignard reagents<br />

was also attempted <strong>to</strong> anisole 101b, but neither dearomatisation nor nucleophilic<br />

aromatic substitution were observed and only starting material was isolated. Finally,<br />

Table 2.1 shows that the six reactions in which dearomatisation occurred had similar<br />

opaque brown/green solutions such as that shown below.<br />

Scheme 2.6 – crystal structure and reaction solution of 102b<br />

55


2.1 – A new reaction<br />

<strong>The</strong> next section will outline the study and optimisation of the stereoselective<br />

dearomatising addition, and the subsequent section looks at its application <strong>to</strong> a number<br />

of organolithiums, aromatic systems, and electrophiles. Section 2.4 will discuss the<br />

mechanistic implications of these results. Throughout these sections, the anti-diphenyl<br />

oxazoline discussed above will be abbreviated:<br />

Ph<br />

Ox* = O<br />

N<br />

Ph<br />

56


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

2.2 Optimisation of Reaction Conditions<br />

Having established that this chemistry is novel, the reaction conditions were reviewed<br />

<strong>to</strong> improve the yield of dearomatised adduct, and reduce side reactions. For most of<br />

these studies the para-anisole aromatic system was be used since it showed more<br />

ortho-lithiation than the phenyl ring – the main side-reaction – and its aromatic pro<strong>to</strong>ns<br />

are easily distinguished by 1 H NMR. Isopropyllithium was generally used for these<br />

test reactions since it gives single diastereoisomers with characteristic diastereo<strong>to</strong>pic<br />

methyl signals.<br />

2.2.1 Solvent system<br />

DMPU is a key additive for dearomatising addition, yet it is unclear whether its role is<br />

simply <strong>to</strong> deaggregate the organolithium, or <strong>to</strong> promote a specific reactivity. A direct<br />

comparison of the crude 1 H NMR spectra of reactions in the presence of DMPU,<br />

TMEDA and no co-solvent was made (Table 2.2). HMPA was not studied since<br />

Meyers had not been able <strong>to</strong> achieve dearomatisation using it, and due <strong>to</strong> its <strong>to</strong>xicity, 65<br />

but has recently been found by Karlubíková <strong>to</strong> make little difference. 66<br />

Ox*<br />

i) i-PrLi (1.5 eq), THF<br />

co-solvent (n eq)<br />

Ox*<br />

Ox*<br />

Me<br />

OMe<br />

101b<br />

ii) MeI<br />

OMe<br />

102b<br />

OMe<br />

103b<br />

Co-solvent (eq) 102b / % 103b / % SM / %<br />

None 22 73 4<br />

TMEDA (6 eq) 23 72 5<br />

DMPU (6 eq) 67 20 4<br />

Table 2.2 – crude ratios of addition with different co-solvent<br />

57


2.2 – Reaction optimisation<br />

% Composition<br />

80%<br />

60%<br />

40%<br />

20%<br />

102b<br />

103b<br />

SM<br />

Misc<br />

Aromatic<br />

0%<br />

0 2 4 6 8 10 12 14 16<br />

Eq. DMPU<br />

Scheme 2.7 – crude reaction composition vs. eq of DMPU (relative <strong>to</strong> oxazoline)<br />

<strong>The</strong>se data show that the inclusion of TMEDA in the reaction has no impact on the<br />

course of the reaction, indicating that DMPU has a specific mode of action. This study<br />

was extended <strong>to</strong> investigate the importance of the concentration of DMPU (Scheme<br />

2.7).<br />

<strong>The</strong> results show that whilst DMPU is essential for the dearomatising addition, higher<br />

concentrations promote side reaction. <strong>The</strong> miscellaneous aromatics were not<br />

identified, but appear <strong>to</strong> be products of lithiation, possibly ortho <strong>to</strong> the methoxy group.<br />

From these studies, it was concluded that six equivalents of DMPU with respect <strong>to</strong> the<br />

oxazoline were optimal. A small quantity of co-solvent is consistent with the guidance<br />

of Collum, who suggests that higher concentrations are rarely necessary. 67<br />

Ethereal solvents, primarily THF and diethyl ether, are commonly used in<br />

organolithium chemistry since they are both relatively inert and good Lewis bases<br />

which coordinate lithium, making the organic counter ion more reactive. 14 Whilst<br />

both ether and THF gave similar crude reaction mixtures, <strong>to</strong>luene was also found <strong>to</strong> be<br />

a promising solvent.<br />

58


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

Ox*<br />

i) s-BuLi (1.5 eq)<br />

−78 °C, DMPU (6 eq)<br />

solvent<br />

Ox*<br />

Ox*<br />

ii) MeI<br />

R<br />

R<br />

R<br />

101 102' 116'<br />

Solvent R 102’ / % 116’ / % SM / %<br />

THF H 81 0 5<br />

PhMe H 66 5 20<br />

THF OMe 71 7 5<br />

PhMe OMe 50 10 20<br />

Table 2.3 – isolated yields comparing <strong>to</strong>luene and THF as solvents<br />

Although no ortho-lithiation was observed in <strong>to</strong>luene, less diene was isolated and a<br />

significant amount of rearomatised adduct (116’). This is most likely due <strong>to</strong> pro<strong>to</strong>n<br />

abstraction from the methyl group of the solvent which also explains the increased<br />

amount of recovered starting material, since any ortho-lithiated oxazoline may simply<br />

abstract a pro<strong>to</strong>n from the solvent. Whilst this in-situ regeneration of starting material<br />

is appealing, it is more than offset by the losses in the formation of rearomatised 116’.<br />

Other solvents such as DMPU, benzene and hexane, were tried but the reaction failed<br />

either due <strong>to</strong> poor solvation, or freezing under the reaction conditions. Cumene<br />

presents itself as a less acidic alternative <strong>to</strong> <strong>to</strong>luene but initial reactions have shown<br />

little improvement. 66 <strong>The</strong> role of solvent and aggregation state is discussed in section<br />

2.4.3.<br />

59


2.2 – Reaction optimisation<br />

2.2.2 Duration of reaction<br />

<strong>The</strong> reaction was known <strong>to</strong> be relatively rapid since all initial results were obtained<br />

after 30 minutes of reaction, but it was unclear how the reaction progressed with time.<br />

To better understand this, parallel reactions were quenched at time intervals of 1, 5, 15<br />

and 30 minutes and their crude compositions compared.<br />

Ox*<br />

i) i-PrLi (1.5 eq)<br />

THF, DMPU (6 eq),<br />

t mins<br />

Ox*<br />

Ox*<br />

Me<br />

OMe<br />

ii) MeI<br />

OMe<br />

OMe<br />

101b<br />

102b<br />

103b<br />

% composition<br />

70%<br />

60%<br />

50%<br />

40%<br />

102b<br />

103b<br />

30%<br />

SM<br />

20%<br />

10%<br />

0%<br />

0 5 10 15 20 25 30<br />

t / min<br />

Scheme 2.8 – change in crude reaction composition with time<br />

<strong>The</strong>se data show that the reaction is essentially complete within 5 minutes of<br />

organolithium addition, and that a modest period of standing does not cause any<br />

significant decomposition of product. <strong>The</strong>re is no significant change in the ratio of<br />

ortho-lithiation <strong>to</strong> dearomatisation, implying that the reactions occur at a similar rate.<br />

2.2.3 Concentration of organolithium<br />

Initial analysis of crude reaction mixtures indicated that a larger excess of<br />

organolithium improved the conversion of starting material. However, comparison of<br />

60


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

isolated yields indicates that any variation more likely reflects the capricious nature of<br />

the reaction, and in future it is suggested that 1.5 equivalents is used since these are the<br />

conditions that the concentration of DMPU was optimised for.<br />

Ox*<br />

i) i-PrLi (n eq),<br />

THF, DMPU (6 eq),<br />

Ox*<br />

Ox*<br />

Me<br />

ii) MeI<br />

OMe<br />

OMe<br />

OMe<br />

101b<br />

102b<br />

103b<br />

Entry Equivalents 102b / % 103b / % SM / %<br />

a 1.5 64 22 3<br />

b 1.5 58 - 4<br />

c 2.0 70 17 0<br />

d 3.0 62 12 3<br />

Table 2.4 – variation in isolated yield of diene 102b and eq. of organolithium<br />

<strong>The</strong> progress of the reaction can be quite delicate. If stirring s<strong>to</strong>pped during reaction,<br />

particularly during addition of the organolithium, this generally resulted in the reaction<br />

turning brown, slowly getting lighter and poor conversion of starting material.<br />

Commercially available isopropyllithium was used, since when made from lithium<br />

wire and i-PrCl 68 filtration of the solids proved impossible and solutions completely<br />

degraded within a week. When this isopropyllithium was used, yields were similar <strong>to</strong><br />

those above. Meyers noted improved yields when using organolithiums prepared in<br />

situ from Freeman’s reagent (lithium 4,4’-ditert-butylbiphenyl, LiDBB) 28 including the<br />

generation of i-PrLi from i-PrBr, normally considered impractical. 14<br />

2.2.4 Temperature<br />

When the internal temperature of a two gram reaction was moni<strong>to</strong>red, no significant<br />

change was observed. 69 Whilst no reliable results were obtained from experiments<br />

performed at different temperatures, it was noted that when the reaction was allowed <strong>to</strong><br />

warm past –60 °C it would quickly decolourise.<br />

61


2.2 – Reaction optimisation<br />

2.2.5 Order of addition<br />

It was hoped that changing the order of addition of reagents might have a significant<br />

effect upon the outcome of the reaction. A summary of these experiments is given in<br />

Table 2.5 and Table 2.6, in which the presence of the characteristic opaque-green<br />

reaction colour is noted alongside the presence of any product.<br />

Entry Description Reaction vessel Syringe Green? Product?<br />

a<br />

b<br />

RLi last<br />

(Normal)<br />

RLi last, preaggregate<br />

101b in<br />

DMPU/THF,<br />

101b in THF,<br />

c Oxazoline last THF, s-BuLi<br />

d<br />

Oxazoline last,<br />

pre-aggregate<br />

DMPU/THF,<br />

s-BuLi<br />

e 66 Oxazoline last s-BuLi<br />

s-BuLi Y Y<br />

DMPU/THF,<br />

s-BuLi<br />

101b in<br />

DMPU/THF,<br />

N<br />

Disappears<br />

N<br />

N<br />

101b in THF N N<br />

101a in<br />

DMPU/THF,<br />

Y<br />

Y<br />

Table 2.5 – outcome of changing the order of combining reagents in THF<br />

<strong>The</strong> normal reaction conditions (entry a) involve the organolithium being added last <strong>to</strong><br />

the other cooled reagents. All orders of addition in which the organolithium and a<br />

Lewis base were pre-mixed gave no product, presumably due <strong>to</strong> deaggregation of the<br />

organolithium. This hypothesis was confirmed when reverse addition without premixing<br />

the organolithium and THF was successful (entry e), and yields were<br />

comparable <strong>to</strong> normal addition. Similar results were seen in <strong>to</strong>luene:<br />

Entry Reaction Reaction vessel Syringe Green? Product?<br />

a<br />

b<br />

c<br />

RLi last<br />

(Normal)<br />

Oxazoline last,<br />

pre-aggregate<br />

Oxazoline last,<br />

pre-aggregate<br />

– 40 °C<br />

101b in<br />

DMPU/PhMe,<br />

DMPU/ PhMe,<br />

s-BuLi<br />

DMPU/ PhMe,<br />

s-BuLi<br />

d Oxazoline last PhMe, s-BuLi<br />

s-BuLi Y Y<br />

101b in PhMe Y N<br />

101b in PhMe N N<br />

101b in<br />

DMPU/PhMe,<br />

? ?<br />

Table 2.6 – outcome of changing the order of combining reagents in <strong>to</strong>luene<br />

62


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

Whilst colouration was seen when the organolithium was pre-mixed with DMPU this<br />

did not yield any product despite quenching the reaction after 1 minute whilst still<br />

coloured. It is thought likely that as before, avoiding pre-mixing the organolithium<br />

with the Lewis base is key (entry d) but unwise with the relatively acidic <strong>to</strong>luene.<br />

It was not expected that the reaction would prove <strong>to</strong> be so sensitive <strong>to</strong> reaction<br />

conditions, but it does seem <strong>to</strong> emphasise the importance of deaggregation of the<br />

organolithium. <strong>The</strong> role of aggregation in this reaction is discussed in section 2.4.3.<br />

63


2.3 – Synthetic scope<br />

2.3 Synthetic Scope<br />

Until now, most reactions have used secondary organolithiums isopropyllithium and<br />

sec-butyllithium, only two aromatic substituents and iodomethane as electrophilic<br />

quench. For the reaction <strong>to</strong> be synthetically useful, it should be general <strong>to</strong> a number of<br />

nucleophiles, electrophiles and <strong>to</strong>lerate a number of aryl groups.<br />

2.3.1 Organolithiums<br />

2-Phenyl oxazoline 101a was treated with a number of commercially available<br />

organolithiums. <strong>The</strong> results are summarised below.<br />

Ox*<br />

i) NuLi (1.5 eq),<br />

THF, DMPU (6eq)<br />

−78 °C 5 min<br />

Ox*<br />

Nu<br />

ii) MeI<br />

101a 102a<br />

Entry Nu 102a (SM) / % Lithiated Colour<br />

a n-Bu < 5 (95) 0 Electric blue<br />

b 64 Me < 5 (95) 0 –<br />

c † Me 3 SiCH 2 1 (45) 22 Electric blue<br />

d s-Bu 81 * (1) 8 Dark green<br />

e i-Pr 70 (12) 6 Dark green<br />

f 70 t-Bu 17 (12) 17 Dark green<br />

g 64 PhLi < 5 (95) 0 –<br />

† addition <strong>to</strong> 101b (Scheme 2.9) * 3:1 exocyclic d.r.<br />

Table 2.7 – survey of organolithium nucleophiles<br />

Primary alkyllithiums (entries a-c) show little or no dearomatisation, indeed diene was<br />

only isolated from addition of (trimethylsilyl)methyllithium (Scheme 2.9). This<br />

reaction saw mainly benzylic lithiation, previously unseen for these oxazolines,<br />

predominantly at the aza-allylic C4 position (117). Diene 102b” is tentatively<br />

assigned by 1 H, COSY and mass spectroscopic data, similar results were seen when<br />

solvated in <strong>to</strong>luene.<br />

64


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

Ph<br />

Ph<br />

Ph<br />

Me<br />

Ph<br />

Ph<br />

Me Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

i) Me 3 SiCH 2 Li (3 eq)<br />

THF, DMPU (6 eq)<br />

O<br />

N<br />

O<br />

N<br />

O<br />

N<br />

Me<br />

ii) MeI<br />

SiMe 3<br />

OMe<br />

101b<br />

OMe 20% OMe 2% OMe 1%<br />

117 118 102b"<br />

Scheme 2.9 – addition of (trimethylsilyl)methyllithium<br />

A similar by-product was observed by Cabedo when treating the unsubstituted<br />

aromatic oxazoline with tert-butyllithium. In the absence of both regioisomers, 119<br />

was initially assigned with a methyl at C5, in light of the above result it has been<br />

reassigned as shown.<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph Me<br />

Ph<br />

O<br />

N<br />

i) t-BuLi (1.5 eq)<br />

THF, DMPU (6 eq)<br />

O<br />

N<br />

Me<br />

O<br />

N<br />

ii) MeI<br />

17%<br />

17%<br />

101a<br />

102a"'<br />

119<br />

Scheme 2.10 – addition of tert-butyllithium<br />

<strong>The</strong> modest diastereoselectivity for addition of s-BuLi is likely <strong>to</strong> be the result of the<br />

kinetic resolution of the organolithium whose stereogenic centre can rapidly invert. A<br />

similar level of diastereoselectivity was observed for the addition <strong>to</strong> para-anisole<br />

101b.<br />

Ox*<br />

i) s-BuLi (3 eq)<br />

THF, DMPU (6 eq)<br />

Ox* Me<br />

*<br />

Ox*<br />

OMe<br />

101b<br />

ii) MeI<br />

OMe<br />

102b'<br />

71%<br />

*d.r. 7:2<br />

OMe<br />

116b'<br />

7%<br />

Scheme 2.11 – addition of sec-butyllithium <strong>to</strong> oxazoline 101b<br />

Perhaps the most surprising outcome of these reactions is the specificity for secondary<br />

nucleophiles, in stark contrast with the dearomatising additions of Meyers, which<br />

worked with a vast range of alkyllithiums. <strong>The</strong> nucleophilicity of organolithiums<br />

65


2.3 – Synthetic scope<br />

generally follows their basicity; tertiary > secondary > primary (steric encumbrance<br />

aside) however this has not be borne out in these studies, which see an effective<br />

nucleophilicity secondary > tertiary >> primary. Whilst the order of reactivity is not<br />

inconsistent with the traditional nucleophilicity once <strong>to</strong>rsional strain is accounted for,<br />

the absence of reaction of primary organolithiums is surprising, and led <strong>to</strong> the proposal<br />

of a single electron transfer (SET) mechanism. This proposition is supported by<br />

Bar<strong>to</strong>li’s ranking of the electron donating ability of organomagnesium reagents from<br />

their oxidation potentials: i-Pr > Bn ≥ Et > Me >>Ph. 20 Similar data is not available for<br />

organolithiums due <strong>to</strong> electrode degradation 71 (vide infra) but this series indicates that<br />

the isopropyl anion as one of the better electron transfer reagents. A SET mechanism<br />

is discussed in section 2.4.2, alongside the role of aggregation state on the reactivity of<br />

different organolithiums in section 2.4.3.<br />

2.3.2 Arenes<br />

Reaction with a number of arenes would allow this methodology <strong>to</strong> bring the<br />

advantages of aromatic chemistry, primarily good regioselectivity and a wealth of<br />

starting materials, <strong>to</strong> making aliphatic compounds with dense stereochemistry. A<br />

number of oxazolines were synthesised (section 3.1) and subjected <strong>to</strong> the reaction in<br />

THF; if addition was unsuccessful then it was repeated in <strong>to</strong>luene, with a positive<br />

result in two instances.<br />

66


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

Ox*<br />

i) i-PrLi (1.5 eq),<br />

THF, DMPU (6 eq)<br />

−78 °C 5 min<br />

Ox*<br />

Ox*<br />

Ox*<br />

Me<br />

ii) MeI<br />

R R R<br />

101 102 116<br />

R<br />

103<br />

Entry R 102 116 103 SM Colour<br />

a H 70 0 6 12 Dark green<br />

b # p-OMe 64 0 17 6 Dark green (Scheme 2.6)<br />

c m-OMe 54 * 0 9 * 20 Apple green (Scheme 2.12)<br />

d 72 m-F † 10 * 0 10 * 40 Forest green (Scheme 2.13)<br />

e 72 p-F † c. 30 20 c. 40 ‡ 5 Forest green<br />

f p-Ph 32 30 0 14 Cherry red (Scheme 2.13)<br />

g p-CN 0 0 0 0 Wine red<br />

h p-NO 2 0 0 0 >95 Wine red (Scheme 2.14)<br />

i o-OMe 72 0 90 0 0 Wine red<br />

j 2-Me-4- 0 0 65 0 Wine red<br />

OMe<br />

*1,2,3 substituted regioisomer † in <strong>to</strong>luene ‡ sum of 2 regioisomers # average of 4 reactions<br />

Table 2.8 – addition <strong>to</strong> different aromatic systems<br />

Addition <strong>to</strong> the electron-rich meta-anisole system (101c, entry c) proceeded in good,<br />

unoptimised yield and only 1,2,3-substituted regioisomers isolated; confirmed by x-ray<br />

crystallography of 102c. <strong>The</strong> same regioselectivity was observed for meta-fluoro<br />

101d.<br />

Scheme 2.12 – crystal structure & reaction solution of meta anisole 102c<br />

<strong>The</strong> stereoelectronic preference for 1,2,3-substitution is quite clear; both oxygen and<br />

fluorine are effective π-donors and equally disfavour addition at C2 and C6, whilst<br />

67


2.3 – Synthetic scope<br />

their electronegativity makes them strong σ-withdrawing groups, favouring C2.<br />

Furthermore by analogy <strong>to</strong> anisole's propensity <strong>to</strong> ortho-lithiation, 14 anisole 101c could<br />

direct attack <strong>to</strong>wards C2, possibly explaining the significantly better yield of 102c.<br />

Whilst Meyers also observed high regioselectivity, the choice of carbons <strong>to</strong> attack was<br />

stark; addition <strong>to</strong> 1-naphthyloxazolines could only happen at the C2 since attack at C9<br />

position would impact upon the aromaticity of the adjacent ring. Addition <strong>to</strong><br />

substituted 2-naphthyloxazolines was not studied by Meyers.<br />

Toluene promoted addition <strong>to</strong> both fluorinated aromatic systems where THF had<br />

failed, and could be seen in a change of reaction colour from electric blue <strong>to</strong> forest<br />

green (entries e, f, Scheme 2.13a). Unfortunately these reactions were plagued by<br />

products of rearomatisation which proved hard <strong>to</strong> separate and characterise. Extensive<br />

prepara<strong>to</strong>ry TLC was performed by Baker <strong>to</strong> separate diene 102d from the orthomethyl<br />

103d; yields for addition <strong>to</strong> 4-fluoro 101e are estimated from the combined<br />

fractions since mixed regioisomers 103e were not separable from diene 102e. 72<br />

a) b)<br />

Scheme 2.13 – reaction solutions of a) 101d (3-F) in PhMe and b) 101f (p-Ph)<br />

Pleasingly, addition <strong>to</strong> biaryl 101f (entry f, Scheme 2.13b) showed addition in 60%<br />

yield, however despite being performed in THF, approximately half of the<br />

dearomatised material abstracted pro<strong>to</strong>ns from the solvent. It is possible that this<br />

reflected the quality of the purchased THF used in this reaction compared <strong>to</strong> that<br />

distilled from sodium, but no significant depletion in yield was noticed for addition <strong>to</strong><br />

anisole 101b under similar conditions.<br />

68


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

Addition <strong>to</strong> para-cyano 210g resulted in complete consumption of starting material,<br />

with no products isolated. Nitriles are very susceptible <strong>to</strong> nucleophilic attack, and<br />

lithiation of cyanobenzenes usually requires non-nucleophilic bases such as LDA. 73<br />

<strong>The</strong> lack of reaction with the para-nitro 101h was disappointing since by lowering the<br />

energy of the LUMO it should make the aromatic ring more susceptible <strong>to</strong> attack. <strong>The</strong><br />

complete absence of reaction is also surprising since Köbrich found that aromatic nitro<br />

groups are readily reduced even when competing with the rapid halogen-lithium<br />

exchange, indeed reduction still dominated at –100 °C. 74 <strong>The</strong> meta isomers of both<br />

these oxazolines would be better predisposed <strong>to</strong> dearomatising addition by cumulative<br />

electron withdrawal.<br />

Scheme 2.14 – reaction solution of 101i (p-NO 2 )<br />

ortho-Anisole 101i underwent S N Ar (entry i) which was also observed by Baker for the<br />

2,4-dimethoxyoxazoline; 72 nucleophilic aromatic substitution was also observed by<br />

Meyers for similar compounds. 75 Treatment of ortho-alkylated 103b (entry j, Scheme<br />

2.15) led <strong>to</strong> benzylic lithiation, reaffirming that the organolithium is still highly basic<br />

under the reaction conditions. Analysis of the crude reaction mixture showed small<br />

quantities of another lithiation product, as well as traces of dearomatisation; a<br />

disappointing outcome in light of Yamamo<strong>to</strong>’s ATPH-promoted dearomatisation of<br />

similar methyl benzenes by organolithiums (section 1.3.3).<br />

Ox*<br />

i) i-PrLi (3 eq)<br />

THF, DMPU (6 eq)<br />

−78 °C<br />

ii) MeI<br />

Ox*<br />

OMe OMe 65%<br />

103b 120<br />

Scheme 2.15 – reaction of ortho-alkylated oxazoline<br />

69


2.3 – Synthetic scope<br />

<strong>The</strong> presence of the ortho substituent causes a significant movement in the chemical<br />

shift of the oxazoline pro<strong>to</strong>ns; all non-ortho substituted oxazolines have characteristic<br />

1 H chemical shifts very close <strong>to</strong> 5.4 and 5.2 ppm (C5 and C4 respectively, identified by<br />

correlation spectroscopy), always 0.20 ppm apart. In contrast those of anisole 103b<br />

are 5.31 and 5.26 ppm, separated by only 0.05 ppm. Whilst the coupling constants and<br />

13 C NMR chemical shifts are similar <strong>to</strong> other aryloxazolines, the change in pro<strong>to</strong>n<br />

chemical shift might be indicative of a subtle change in the oxazoline environment.<br />

However since few ortho-substituted aromatic systems have been treated, no<br />

correlation with reactivity many be inferred.<br />

It is surprising that the electron-rich anisole derivatives were readily dearomatised<br />

whilst a number of less demanding aromatic systems were not. Strong π-donors such<br />

as methoxy reduce the electrophilicity of the arene by raising the energy of the LUMO,<br />

and would also destabilise a transition state with a developing negative charge.<br />

Generally groups which are relatively π-neutral such as Ph and F would not be<br />

expected <strong>to</strong> differ from the unsubstituted ring. Meyers only published reactions with<br />

methoxynaphthalenes, and whilst these are synthetically very versatile, it may be<br />

assumed that other aromatic substituents were tried and failed.<br />

2.3.3 Electrophiles<br />

Equally important <strong>to</strong> the utility of the final compounds is the range of electrophiles<br />

<strong>to</strong>lerated and the regioselectivity of their addition. Upon addition of the electrophilic<br />

quench, immediate decolourisation was seen, indicating that reaction is rapid.<br />

Regioselectivity was found <strong>to</strong> be dependent upon the nature of the electrophile, and is<br />

summarised below. <strong>The</strong> products are identified as α, γ, ε by the site of addition with<br />

respect <strong>to</strong> C=N, and a brief rationalisation of the selectivity follows.<br />

70


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

Ph<br />

Ph<br />

EX<br />

Ox*<br />

E<br />

Ox*<br />

O<br />

N<br />

i-PrLi, DMPU<br />

THF<br />

R<br />

102α<br />

Ox*<br />

E<br />

R<br />

102ε<br />

Ox*<br />

Ox*<br />

R<br />

101<br />

NH 4 Cl<br />

R<br />

102ε<br />

R<br />

102γ<br />

R<br />

116<br />

Entry R EX 102α / % 102γ / % 102ε / % 116 / % SM / %<br />

a H MeI 70 0 0 0 12<br />

b ‡64 H allyl Br 50 0 10 0 12<br />

c ‡64 H BnBr 24 0 36 0 21<br />

d ‡64 H PhCHO 0 0 0 30 20<br />

e ‡70 H NH 4 Cl 0 47 0 5 32<br />

f †70 F * NH 4 Cl 0 0 53 7 37<br />

g OMe * MeOH 0 30 15 5 29<br />

* PhMe solvent ‡ reaction by N. Cabedo † reaction by T Baker<br />

Table 2.9 – electrophilic additions<br />

Addition of alkyl halides proceeded preferentially at the α position (entries a-c), as<br />

observed with the extended enolates of ke<strong>to</strong>nes, esters 76 and most other nucleophilic<br />

dearomatising additions (section 1.3). Increasing the size of the electrophile caused<br />

addition at the less encumbered ε position, giving conjugated dienes 102ε. Soft<br />

electrophiles such as alkyl halides react preferentially with soft nucleophiles; if we<br />

approximate azaenolate 121 as the heptatriene anion (Scheme 2.16), we see that the<br />

HOMO has the largest coefficients at the α and γ carbons. Using this model, addition<br />

<strong>to</strong> the ε position would not be expected under the kinetic conditions of reaction,<br />

however since the presence of the nitrogen in is likely <strong>to</strong> perturb the HOMO it is quite<br />

possible the ε carbon has a larger coefficient.<br />

71


2.3 – Synthetic scope<br />

Ph<br />

O<br />

Ph<br />

NLi<br />

R ≈<br />

α<br />

β<br />

γ ε<br />

δ<br />

121<br />

Scheme 2.16 – approximation of the HOMO of the azaenolate<br />

However the hard protic quench of azaenolate 121 shows complete regioselectivity for<br />

the ε position (entry e). This is be explained if pro<strong>to</strong>n addition is in equilibrium, since<br />

102ε has the longest conjugated system; also explaining why α-pro<strong>to</strong>nation is not seen.<br />

Unfortunately, pro<strong>to</strong>nation of para-substituted oxazolines (entries f, g) does not<br />

support thermodynamic pro<strong>to</strong>nation, however a change in solvent and method of<br />

pro<strong>to</strong>nation means that further experimentation would be necessary <strong>to</strong> gain further<br />

insight.<br />

This is consistent with the reaction of electrophiles with 2-oxazolinylnaphthalene<br />

azaenolate 122, by Meyers. Whilst iodomethane also gave α addition, pro<strong>to</strong>nation<br />

gave the thermodynamic product 124 in low yield, accompanied by rearomatisation. 26<br />

Nu<br />

122<br />

O<br />

N<br />

Li<br />

MeI<br />

MeOH<br />

Nu<br />

Nu<br />

O<br />

N<br />

Me<br />

O<br />

N<br />

124<br />

Nu = n-Bu 90%<br />

= s-Bu 91%<br />

= t-Bu 90%<br />

Nu = n-Bu 18%<br />

= t-Bu 31%<br />

= Ph 74%<br />

Scheme 2.17 – electrophilic quench of 2-oxazolinylnaphthalenes 26<br />

Meyers observed regiospecific α addition <strong>to</strong> the azaenolates of 1-<br />

oxazolinylnaphthalenes for a large range of electrophiles (section 1.3.2). This is most<br />

likely because the HOMO is likely <strong>to</strong> be confined <strong>to</strong> the non-aromatic carbons;<br />

although Ortiz 1 makes the unlikely suggestion that it is a complex-induced proximity<br />

effect (CIPE). 38 Whilst the principle of least motion analysis is often applied <strong>to</strong><br />

rationalise the pro<strong>to</strong>nation of the hydrobenzene anion in the Birch reduction, it cannot<br />

be applied <strong>to</strong> this situation since the resonance structures will not contribute equally.<br />

72


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

2.4 Mechanistic Discussion<br />

In the above studies a number of unexpected observations have been made. In this<br />

section a number of these will be discussed in the context of the reaction mechanism<br />

and the relevant literature.<br />

2.4.1 Stereoselectivity<br />

Regio- and stereoselectivity scarcely received mention in the sections above since few<br />

isomers were isolated. It was suggested that the complete stereoselectivity is simply<br />

due <strong>to</strong> the steric bulk of the pseudo-C 2 symmetric oxazoline strongly favours the attack<br />

of the nucleophile on one face.<br />

R<br />

Li<br />

O<br />

N<br />

Li<br />

O<br />

N<br />

R<br />

Scheme 2.18 – stereochemical rationale for addition <strong>to</strong> diphenyl oxazolines 101<br />

<strong>The</strong> nitrogen lone pair lies in the plane of the oxazoline and must coordinate lithium in<br />

the same manner whilst the adjacent phenyl group favours delivery of the organic<br />

ligand from the opposite face. Attack by complexation with nitrogen is consistent with<br />

the complex-induced proximity effect (CIPE), and with the mechanism proposed by<br />

Meyers for monodentate oxazolines (section 1.3.2.c).<br />

monodentate oxazoline<br />

bidentate oxazoline<br />

R<br />

Li<br />

O<br />

N<br />

R<br />

Li<br />

O<br />

N<br />

O<br />

54<br />

126<br />

Scheme 2.19 – Meyers’ reactive complexes<br />

Unlike Meyers, we have been unable <strong>to</strong> gain insight in<strong>to</strong> the cause of the<br />

stereochemical induction since studies of different substituents at C4 and C5 were<br />

unsuccessful. Since both stereogenic centres direct in the same sense <strong>to</strong> the pendant<br />

aromatic ring, it is possible that the alkyl group does not exclusively attack from a<br />

73


2.4 – Mechanistic discussion<br />

chelate with nitrogen. Indeed, it is not clear how closely associated the organic and<br />

metallic portions of the organolithium are; whether they exist as contact ion pairs<br />

(CIPs) or solvent separated ion pairs (SIPs). <strong>The</strong> rationalisation given in Scheme 2.18,<br />

as well as those of Meyers, requires contact ion pairs <strong>to</strong> direct delivery over the C4<br />

stereocentre.<br />

This stereochemical rationale assumes a two-electron mechanism. Separate electron<br />

transfer and radical coupling steps are not inconsistent with this proposal, but radical<br />

combination would need <strong>to</strong> occur rapidly, otherwise the neutral organic radical can<br />

diffuse outside of the solvent cage (i.e. is after the rate determining step).<br />

2.4.2 Reaction pathway: one electron or two?<br />

Chemical reactions between occur when valence electrons move from donor <strong>to</strong><br />

accep<strong>to</strong>r whilst the species themselves move. In a perfectly polar, or “two electron”<br />

reaction, these processes are synchronous, whilst the extreme case whereby electron<br />

motion precedes nuclear motion is termed single electron transfer (SET). It has been<br />

suggested that the dearomatising reaction proceeds through an SET mechanism,<br />

requiring an initial electron transfer (ET) and radical coupling (RC) of the resulting<br />

radicals (Scheme 2.20a). Whilst it is commonplace <strong>to</strong> differentiate one and two<br />

electron reactions in organic chemistry, in his insightful account on the course of<br />

electron and nuclear motion, Pross disagrees with this distinction since chemical bond<br />

making only requires the movement of one valence electron from the donor (Scheme<br />

2.20b). 77<br />

Polar (Pl)<br />

Pl<br />

D−M + A − D−A + M + R−M + E−X<br />

R−E + MX<br />

ET<br />

RC<br />

ET<br />

RC<br />

D • M + + A •−<br />

R • M + + E−X •−<br />

ET<br />

R • E • + Mg + X −<br />

a) Addition Mechanisms b) Substiution Mechanisms<br />

Scheme 2.20 – SET and polar interpretations of addition and substitution reaction<br />

<strong>The</strong> energetic processes involved in an SET reaction may be depicted in a<br />

configuration model (CM) presented by Pross (Scheme 2.21). Here, the donor (D) and<br />

accep<strong>to</strong>r (A) exist as separate species before ET, and are represented by the DA curve;<br />

74


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

after ET the species are represented by the line D + A – , and the gap between the lines<br />

represents the energy required for ET. <strong>The</strong> reaction pathway consists of solvent<br />

reorganisation and geometric dis<strong>to</strong>rtions that occur before ET <strong>to</strong> raise the energy of the<br />

DA complex until it is isoenergetic with D + A – (point B), at which time ET occurs and<br />

the species relax <strong>to</strong> their new ground state. <strong>The</strong> strong similarity between the CM<br />

diagram and Marcus theory’s avoided crossing diagrams is deliberate – the dashed<br />

lines were added by Pross – and the ET process if often termed outer-sphere electron<br />

transfer.<br />

B<br />

E<br />

Reaction coordinate<br />

Scheme 2.21 – energy profile of electron transfer from species D <strong>to</strong> A<br />

Like the balance between inner and outer sphere electron transfer, Pross proposes that<br />

SET occurs when the stabilising interactions of synchronous bond formation do not<br />

outweigh the energetic cost of bringing the two sets of nuclei <strong>to</strong>gether. <strong>The</strong> fac<strong>to</strong>rs<br />

determining where a reaction lies on this continuum have been widely discussed.<br />

Since redox potentials are a direct measure of how readily a species accepts or donates<br />

an electron they are often mooted as allowing prediction about a reaction, although this<br />

is often limited by available data (vide infra). Viewing ET in a molecular orbital<br />

sense, reagents with high energy HOMOs will have little interaction with low lying<br />

LUMOs in a transition state, making a SET reaction likely.<br />

Whilst the nature of the two reagents is important <strong>to</strong> the manner in which the reaction<br />

proceeds, the difficulties faced when trying <strong>to</strong> make generalisations indicate that many<br />

other fac<strong>to</strong>rs influence how the valence electrons move. In the application of Marcus<br />

theory <strong>to</strong> organic reactions, Eberson also emphasises that any fac<strong>to</strong>r that minimises<br />

75


2.4 – Mechanistic discussion<br />

orbital overlap as the transition state is approached will disfavour the polar mechanism<br />

or inner-sphere electron transfer. 78 <strong>The</strong>se can be fac<strong>to</strong>rs such as steric or geometrical<br />

strain, solvent interactions or simply that a weak bond is being formed.<br />

A number of methods have been developed <strong>to</strong> study the nature of electron transfer in<br />

organic reactions. <strong>The</strong> mechanism of halogen-lithium exchange has been a <strong>to</strong>pic of<br />

much investigation and controversy 79 since 1956 when the first observations hinting at<br />

radical intermediates were made. 14 Whilst spectral data confirmed the presence of<br />

radicals, they were not shown <strong>to</strong> be reaction intermediates until a number of<br />

experiments led <strong>to</strong> a consensus such as those performed on norbornenes 130 by Ashby<br />

(Scheme 2.22).<br />

Fast<br />

X<br />

130X<br />

t-BuLi<br />

Li<br />

Slow at −78 °C<br />

131<br />

X = I at −78 °C<br />

X = Br at 0 °C<br />

Scheme 2.22 – Ashby’s norbornene radical trapping experiments 80<br />

<strong>The</strong>se and other results strongly support the presence of radical intermediates in<br />

bromine-lithium exchange, 81 and their absence in iodine lithium exchange. 82 This is in<br />

disagreement with predictions based upon electrode potentials (alkyl bromides E ½ –2.5<br />

V and iodides E ½ –1.6 V 83 ) and emphasises the lack of predictability using this<br />

method. Very little electrochemical data is available for organolithiums, presumably<br />

due <strong>to</strong> electrode decomposition, as reported by Breslow, who was only able <strong>to</strong> obtain<br />

potentials for allyllithium (–1.63 V) and phenyllithium (–1.43 V). 71<br />

<strong>The</strong> investigations above highlight that whilst it might be relatively easy <strong>to</strong> indicate<br />

that a reaction proceeds via SET, it can be particularly difficult <strong>to</strong> prove so. Ashby<br />

suggests a number of general methods; spectroscopic evidence showing that the rate of<br />

decay of a paramagnetic species is in line with the rate of reaction; loss of<br />

stereochemistry during reaction; and use of a cyclisable probe, preferably of known<br />

lifetime (a radical clock). 79 Rate data from UV-vis spectra of the reduction of<br />

76


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

dimesityl ke<strong>to</strong>ne showed that the decaying radical species observed in EPR spectrum<br />

was a radical anion intermediate now known <strong>to</strong> be present in the reduction of<br />

benzophenone. 84 <strong>The</strong> stereochemical fidelity of a reaction has been used the lithiation<br />

of pyrolidines 85 and most recently by Hoffmann who moni<strong>to</strong>red racemisation of<br />

enantiomerically enriched Grignard reagents (vide infra). 86 Others have inferred a<br />

SET mechanism from rate data showing more hindered species react faster that less<br />

hindered ones, since it is often found <strong>to</strong> be a rapid process. 87<br />

<strong>The</strong> electron transfer (ET) and radical combination (RC) steps of the possible SET<br />

reaction are outlined below, along with the possible polar (Pl) reaction.<br />

Ph Ph<br />

O<br />

N<br />

Li<br />

Ph<br />

Ph<br />

Pl<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

Li<br />

‡Nu<br />

O<br />

N<br />

Li<br />

MeI<br />

O<br />

N<br />

Me<br />

101a<br />

ET<br />

Ph<br />

O<br />

N<br />

Ph<br />

Li<br />

RC<br />

121<br />

102a<br />

‡ET<br />

solvent cage<br />

Scheme 2.23 – possible polar and SET reaction pathways<br />

Often a debate over a polar or SET pathways is only of mechanistic interest, however,<br />

with a reaction that has proved hard <strong>to</strong> optimise, any insights in<strong>to</strong> the processes<br />

occurring could help focus reaction optimisation. <strong>The</strong> first strong indication that a<br />

SET mechanism might be involved was the absence of reaction with primary<br />

organolithiums, which would make very unstable radicals and are unlikely <strong>to</strong> undergo<br />

ET. Other observations are more qualitative such as the opaque reaction solutions<br />

reminiscent of the benzophenone radical anion, high sensitivity <strong>to</strong> solvation, and the<br />

absence of reaction with syn diphenyl oxazoline 109 or para-nitro 101i, as well as a<br />

remarkably quick reaction.<br />

77


2.4 – Mechanistic discussion<br />

Whilst no mechanistic studies were published, Meyers proposed a polar mechanism for<br />

the dearomatising addition <strong>to</strong> 2-naphyloxazolines 38 giving azaenolate 132 (Scheme<br />

2.24). Meyers states that the reactions gradually formed red solutions over the course<br />

or an hour, which decolourised upon quench. 31 <strong>The</strong> reaction also <strong>to</strong>lerated a large<br />

range of organolithiums.<br />

Ph OMe Ph OMe Ph OMe<br />

O<br />

N<br />

Li<br />

O<br />

NLi<br />

n-Bu<br />

MeI<br />

O<br />

N<br />

n-Bu<br />

n-Bu<br />

38 132<br />

97%<br />

d.r. 47:3<br />

Scheme 2.24 – polar reaction mechanism proposed by Meyers<br />

In contrast, the colour of our dearomatisation reaction varies with substrate, regardless<br />

of whether addition occurs or not. <strong>The</strong> reaction is complete within minutes, and deep<br />

colouration observed immediately indicating that trace amounts of intermediate form<br />

rapidly. Such a rapid dearomatisation, without warming above –78 °C is quite<br />

remarkable; for example the kinetically more favourable intramolecular dearomatising<br />

cyclisations of <strong>Clayden</strong> require warming <strong>to</strong> ambient temperature. 88<br />

Miyano and Ber<strong>to</strong>li propose that the dearomatising addition of organometallic reagents<br />

<strong>to</strong> BHA benzoates and dinitrobenzenes respectively proceed through a SET pathway<br />

(section 1.3.1). Whilst these claims were made with different degrees of experimental<br />

support, they lend credence <strong>to</strong> the possibility of an ET process. Two approaches have<br />

been undertaken <strong>to</strong> study the mechanism of reaction; EPR spectroscopy and radical<br />

trapping experiments, and are described below.<br />

2.4.2.a Electron paramagnetic resonance (EPR)<br />

<strong>The</strong> defining characteristic of a radical is its unpaired electron, which it paramagnetic.<br />

Just as NMR spectroscopy measures the energy difference of nuclear spin states in an<br />

applied magnetic field, so does EPR spectroscopy measure the difference of spin states<br />

of the unpaired electron. This energy, denoted g, is of similar magnitude <strong>to</strong> microwave<br />

radiation, and can be characteristic of the type of compound, but has <strong>to</strong> be measured<br />

78


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

very accurately since organic radicals normally have a value around 2.00. <strong>The</strong> g-value<br />

in organic compounds is especially close <strong>to</strong> that of a free electron since all other<br />

electrons are spin paired and make no contribution <strong>to</strong> the spin state. Because of this<br />

the term electron spin resonance (ESR) is often applied <strong>to</strong> organic radicals since the<br />

spin state of a single electron is being measured.<br />

In contrast <strong>to</strong> NMR, only one spin state is normally studied and only one absorbance is<br />

observed in the EPR spectrum. However, more information is obtained from that peak<br />

by plotting the derivative of absorption, which normally results in hyperfine splitting,<br />

as seen in the spectrum of benzene radical (Scheme 2.25). As observed in NMR<br />

spectroscopy, splitting occurs due <strong>to</strong> interactions with the magnetic moment of nuclei,<br />

giving 2n+1 lines. <strong>The</strong> magnitude of the hyperfine coupling, a, depends on the density<br />

of the electron at that nucleus, in the case of benzene, the radical is equally dispersed<br />

across the ring giving a septet.<br />

Scheme 2.25 – EPR spectrum of benzene anion radical (septet, a = 3.75G) 89<br />

Two of the great strengths of EPR spectroscopy are that it is very specific for<br />

identifying radical species and is also very sensitive. <strong>The</strong> former is very useful for a<br />

number of reasons, but mostly because it means that special solvents do not need <strong>to</strong> be<br />

used, the latter can be very useful for analysing trace reaction intermediates which may<br />

have low steady-state concentrations before they are consumed in the reaction.<br />

Compared <strong>to</strong> benzene, radical anion ‡ET has few degenerate pro<strong>to</strong>ns, and might show<br />

a coupling <strong>to</strong> a 14 N nucleus. <strong>The</strong> spectrum would be made more complicated by the<br />

presence of the alkyl radical which generated the radical anion, since the paramagnetic<br />

79


2.4 – Mechanistic discussion<br />

centres would have very similar g-values and the resulting signal would be a<br />

superposition of the two. Fortunately the spectrum of i-Pr• is known which would aid<br />

the analysis.<br />

Sample preparation proved problematic as it required transferring in<strong>to</strong> the narrow<br />

quartz tubes at low temperature under inert conditions. Whilst this was eventually<br />

overcome, it was not possible <strong>to</strong> obtain a homogenous sample. Once prepared,<br />

samples were cooled in liquid nitrogen and transported <strong>to</strong> the X-band 90 spectrometer at<br />

the University of Manchester, and one spectrum is below.<br />

101b + s-BuLi in<br />

DMPU/PhMe<br />

Ph<br />

O<br />

N<br />

Ph<br />

3300 3320 3340 3360 3380 3400 3420<br />

OMe<br />

‡ETb<br />

Scheme 2.26 – X-band EPR spectrum acquired at 220K (doublet, A= 20G, g=1.99)<br />

<strong>The</strong> spectra obtained clearly show the presence of radical species in solution although<br />

the poor resolution means little can be inferred. 91 Sample warming meant that better<br />

spectra could not be acquired, and attempts <strong>to</strong> re-make samples failed. Karlubíková<br />

has since obtained better resolved spectra under similar conditions showing a sextet<br />

with a strong spin coupling of 11.5 G. 66<br />

Whilst these results show unpaired electrons in the reaction mixture, they indicate little<br />

else. Since EPR is a very sensitive technique, the spectrum might simply be due <strong>to</strong> a<br />

low concentration species not on the reaction pathway. A spectrum with better<br />

resolution would give information about the environment of the radical which might<br />

indicate its nature. However sufficient information had been gained <strong>to</strong> continue<br />

investigating the SET mechanism <strong>to</strong> show whether or not this paramagnetic species is<br />

a reaction intermediate.<br />

80


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

2.4.2.b Radical trap<br />

Internal radical traps are commonly used as mechanistic probes and may be attached <strong>to</strong><br />

either the nucleophile or the electrophile. <strong>The</strong>y have often been used <strong>to</strong> measure the<br />

rate of reaction (radical clocks), but since we are mainly interested in a qualitative<br />

understanding of the reaction such studies will not be made. <strong>The</strong> radical trap must be<br />

stable under the reaction conditions and the resulting radical should not propagate any<br />

reaction; halogens or dithianes are often used <strong>to</strong> trap reaction intermediates, but would<br />

also be likely <strong>to</strong> react under the conditions. Methylcyclopropanes are also often used<br />

but their use as mechanistic probes has been discouraged since non-radical<br />

intermediates have been reported <strong>to</strong> trigger ring opening. 92<br />

Appending a probe <strong>to</strong> the oxazoline is preferred since it is synthetically easier, and a<br />

broader range of aromatic substituents have been <strong>to</strong>lerated than have nucleophiles.<br />

<strong>The</strong> group that seems best suited is the allyl group since its behaviour in the presence<br />

of organolithiums has been thoroughly studied and its products should be stable and<br />

readily characterised. Allyl ether 101j (Scheme 2.27) is well suited <strong>to</strong> the task. <strong>The</strong><br />

meta-anisole analogue 101c dearomatised in good yield and complete regioselectivity,<br />

whilst O-allylphenol radical 133 is one of the fastest cyclisation probes, 93 with a halflife<br />

determined by Ingold of 0.1 ns at 30 °C 94 (c. 10 ns at –80 °C). 95 Whilst the radical<br />

anion intermediate is likely <strong>to</strong> be similar <strong>to</strong> that of benzene (Scheme 2.25), a useful<br />

approximation of the rate of cyclisation of an alkyl radical is given by heptene radical<br />

134. 96 Allyl ether 101j is preferred <strong>to</strong> the homoallyl analogue because it undergoes<br />

cyclisation more rapidly 94 and it would be prone <strong>to</strong> benzylic lithiation which might<br />

influence the reactivity of the aromatic system.<br />

Ph<br />

O<br />

N<br />

Ph<br />

133<br />

O<br />

k = 6.3 x 10 9 s -1<br />

t ½ ~0.1 ns<br />

30 °C<br />

O<br />

t ½ ~10 ns<br />

−80 °C<br />

101j<br />

O<br />

134<br />

k = 1.3 x 10 5 s -1<br />

t ½ ~5 ms<br />

25 °C<br />

t ½ ~1 s<br />

−80 °C<br />

Scheme 2.27 – proposed allyl ether radical trap & rate of cyclisation 94<br />

81


2.4 – Mechanistic discussion<br />

Subjecting oxazoline 101j <strong>to</strong> the dearomatising conditions could have a number of<br />

outcomes; those that are of mechanistic interest are outlined in Scheme 2.28. <strong>The</strong><br />

kinetically controlled cyclisation of radical anion ‡ETj, followed by electrophilic<br />

quench should give dearomatised bicycle 136, followed by possible coupling with the<br />

isopropyl radical or pro<strong>to</strong>n abstraction from the solvent. If the dearomatising addition<br />

proceeds along a polar pathway (Pl), or RC is significantly faster than cyclisation of<br />

the tether, then allyl ether 102j will be the major product.<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

Ph<br />

O<br />

i-PrLi<br />

ET<br />

O<br />

‡ETj<br />

N<br />

O<br />

Li<br />

RC<br />


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

O<br />

N<br />

O<br />

N<br />

O<br />

O<br />

137 138 139<br />

OH<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

O<br />

NLi<br />

O<br />

N<br />

Li<br />

140<br />

O<br />

O<br />

141 142<br />

O<br />

Ox*<br />

Ox*<br />

Ox*<br />

OH<br />

O<br />

Me<br />

O<br />

143<br />

SN2'<br />

144<br />

lithiation<br />

144a<br />

isomerisation<br />

Scheme 2.29 – possible reaction pathways of allyl ether<br />

Still and co-workers found that treatment of allyl ether 133 with n-BuLi led <strong>to</strong> near<br />

quantitative α- and γ-alkylation, the latter being selective for the cis isomer (144a);<br />

this is presumably due <strong>to</strong> the formation of a π-allyllithium complex similar <strong>to</strong> 140. 98<br />

This intermediate might also act as an intramolecular nucleophile in a similar manner<br />

<strong>to</strong> the work of Kenworthy and <strong>Clayden</strong>, who found related naphthyloxazoline 145<br />

underwent dearomatising cyclisation. 99 Whilst Kenworthy was performing a<br />

kinetically more favourable 5-exo-trig cyclisation, 6-exo cyclisation <strong>to</strong> give<br />

tetrahydrochromene 142 might be possible.<br />

O<br />

N<br />

O<br />

SnBu 3<br />

MeLi, THF<br />

−78 °C 1 hr<br />

then MeI<br />

O<br />

N<br />

Me<br />

O<br />

OMe<br />

145<br />

OMe<br />

79%<br />

>25:1 dr<br />

Scheme 2.30 – dearomatising cyclisation on<strong>to</strong> 2-naphthyloxazolines 99<br />

83


2.4 – Mechanistic discussion<br />

<strong>The</strong> tethered oxazoline 101j was treated under the reaction conditions, giving a forest<br />

green solution. Mass recovery from the reaction was poor, but the isolated products<br />

were very interesting.<br />

Ox*<br />

i) i-PrLi (2 eq)<br />

THF, DMPU<br />

−78 °C<br />

Ox*<br />

Ox*<br />

Ox*<br />

101j<br />

O<br />

ii) MeI<br />

O<br />

102j<br />

O<br />

O<br />

10% 5% 20%<br />

102j*<br />

142 dr 2:3<br />

Scheme 2.31 – dearomatising addition of allyl tether<br />

<strong>The</strong> major products of the reaction are believed <strong>to</strong> be two diastereomers of bicycle 142,<br />

with a combined yield of 20%. However, two discrepancies exist in this assignment;<br />

whilst the 1 H spectra NMR of the separated diastereomers appears <strong>to</strong> be show single<br />

compounds, adjacent half-intensity peaks appear in the 13 C NMR, resembling a 1:1<br />

mixture of diastereomers. Furthermore the 1 H NMR spectra contain many high<br />

multiplicity peaks with small couplings (1-2 Hz). <strong>The</strong>se spectra are provided in<br />

appendix A.<br />

Dearomatised adduct 102j and its isomer 102j* were characterised by having almost<br />

identical 13 C and 1 H spectra <strong>to</strong> adduct 102c, which had been identified by crystal<br />

structure, only differing in the pendent allyl system. Importantly, no other products<br />

could be identified in the crude NMR. Unfortunately only 15% of the dearomatised<br />

adducts 102j were recovered, compared with 54% of 102c. Whilst diminished yields<br />

were anticipated due <strong>to</strong> the reactivity of the allyl group, it means that we cannot be<br />

sure that some tetrahydrobenzofuran 136 was not formed, and cannot exclude two<br />

reaction pathways. As indicated in Scheme 2.28, the absence of a trapped radical does<br />

not exclude electron transfer, but simply gives an upper limit on the lifetime of a<br />

radical anion ‡ETj of around 10 ns. This allows us <strong>to</strong> rule out a slow RC step which<br />

might have involved diffusion of i-Pr• out of the solvent cage.<br />

Whilst much controversy has surrounded the use of allyl tethers as mechanistic probes,<br />

in Newcomb’s critique on the practice he concludes that the only mechanistic certainty<br />

they provide is in the absence of radical trapping. 92 Although the poor yield means we<br />

cannot be certain, we have shown that free radical intermediates are unlikely.<br />

84


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

2.4.2.c Mechanistic conclusions<br />

<strong>The</strong> data outlined in the previous sections contradict each other; the EPR studies<br />

indicated a stable, long-lived radical species, whilst trapping studies were unable <strong>to</strong><br />

capture the radical anion presumed responsible. If we accept that the poor mass<br />

balance was due <strong>to</strong> a molecule with <strong>to</strong>o many reactive sites we can conclude that the<br />

lifetime of any radical anion intermediate is less than 10 ns, and that species observed<br />

in the EPR spectra is unlikely <strong>to</strong> be a reaction intermediate.<br />

Any further studies of the mechanism must focus on measuring changes inside the<br />

solvent cage, by studying the a<strong>to</strong>ms involved in the rate determining step rather than<br />

trying <strong>to</strong> deduce information from neighbouring groups. Two such methods have been<br />

developed by Yamataka <strong>to</strong> infer a rate determining ET step in nucleophilic additions <strong>to</strong><br />

benzaldehyde (147) and benzophenone (148); the absence of a 14 C kinetic iso<strong>to</strong>pe<br />

effect at the carbonyl, and a near zero linear free-energy relationship (ρ). 87<br />

O<br />

O<br />

H<br />

RLi<br />

THF, 0 °C<br />

14 C=O Kinetic iso<strong>to</strong>pe effect<br />

Hammett plots<br />

147 148<br />

Entry RLi Electrophile<br />

KIE<br />

12 k/ 14 k<br />

ρ<br />

isomerisation<br />

of 152*<br />

RDS<br />

a 100 MeLi 148 1.000 +0.27 1% 101 ET<br />

b 102 PhLi 148 1.003 +0.24 – ET<br />

c 102 PhLi 147 0.998 +0.18 – ET<br />

d 102 allyl-Li 148 0.994 +0.17 – ET<br />

e 87 PhSCH 2 Li 148 – +0.24 – ET<br />

f 87 PhSCH 2 Li 147 0.998 +0.17 – ET<br />

g 87 NCCH 2 Li 147 0.992 +0.14 5% ET<br />

h 103 Li-Pinacolate 147 1.039 +1.16 1% Pl<br />

i 104 MeMgBr 148 1.056 +0.90 – RC<br />

j 104 PhMgBr 148 1.056 +0.59 – RC<br />

k 104 allylMgBr 148 0.999 -0.02 – ET<br />

* % isomerisation of recovered 152 after 1 hr reaction, Scheme 2.33<br />

Table 2.10 – addition of organolithiums <strong>to</strong> benzophenone and benzaldehyde<br />

85


2.4 – Mechanistic discussion<br />

Yamataka developed these approaches <strong>to</strong> moni<strong>to</strong>r nucleophilic attacks since there is<br />

normally no free radical intermediate <strong>to</strong> intercept with a tethered probe. Yamataka’s<br />

use of 14 C labelling at the site of attack works on the assumption that the transfer of an<br />

electron will not perturb the hybridisation or geometry, whilst a polar reaction, or a<br />

rate determining RC clearly would. <strong>The</strong> rational for a small ρ-value for an ET rate<br />

determining step is not so well unders<strong>to</strong>od, but is taken <strong>to</strong> be characteristic since a Pl<br />

anionic processes would clearly be assisted by removing electron density. <strong>The</strong> data<br />

presented in Table 2.10 indicate that Yamataka and co-workers have found a method<br />

for distinguishing the three rate determining steps; they even seem able <strong>to</strong> differentiate<br />

a change in RDS of Grignard addition (entries h-k). This change from an ET <strong>to</strong> a RC<br />

rate determining step is reported <strong>to</strong> reflect how finely balanced SET reaction is.<br />

In a similar manner, Gajewski measured secondary deuterium KIEs of some of these<br />

additions by “α-deuteration” of benzaldehyde. 105 ortho-Deuteration of oxazolines<br />

would allow α-deuteration studies <strong>to</strong> be undertaken and would be significantly easier<br />

than 14 C. Surprisingly, the ortho-lithiation of oxazolines 101a and 101b was<br />

unsuccessful, however meta-anisole 101c should be particularly amenable <strong>to</strong> orthodeuteration<br />

and kinetic study of the resulting d-101c (Scheme 2.32). Whilst<br />

unexpected, Meyers reports that ortho-lithiation can be slow when studying the<br />

deuteration of phenyl oxazolines. 106<br />

Ox*<br />

D<br />

Ox*<br />

Ox*<br />

OMe<br />

d-101c<br />

α-deuteration<br />

KIE<br />

R<br />

150<br />

linear free-energy<br />

relationship<br />

t-Bu<br />

151<br />

radical isomerisation<br />

Scheme 2.32 – possible mechanistic probes<br />

Whilst it may not be strictly valid, a Hammett linear free energy study might provide<br />

some insight, possibly through the study of para-aryl oxazolines 150; since reaction<br />

occurs at the aromatic ring, kinetic data could not be collected for substituents on that<br />

ring since they would have both a direct electronic and steric interaction with the<br />

reacting centres. Fortunately a wealth of Hammett substituent constants are available<br />

86


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

for both para and meta-benzenoid rings, 107 the former might be preferred since<br />

<strong>to</strong>rsional strain would be minimised, although Yamataka purports that ET is not<br />

effected by such considerations. Biaryls 150 might be most readily made by aromatic<br />

cross-coupling, along with one of the methods described in the next chapter.<br />

Ashby has identified the isomerisation of cis-enone 152 as a possible measure of the<br />

existence of radical anion intermediates in its reaction with organometallics (Scheme<br />

2.33). Under conditions of excess 152, the E:Z ratio of recovered starting material and<br />

products were taken <strong>to</strong> indicate the extent <strong>to</strong> which electron transfer occurred, although<br />

it was acknowledged that like other methods it also depended upon the lifetime of the<br />

radical. <strong>The</strong> results were far from conclusive, with only partial isomerisation seen<br />

under dissolving metal conditions, and none with MeLi (entry a, Table 2.10).<br />

Yamataka also subjected enone 152 <strong>to</strong> sub-s<strong>to</strong>ichiometric organolithiums (entries g, h,<br />

Table 2.10) with little isomerisation observed, even for cyanomethyllithium, which<br />

was classified as an ET reagent on the basis of the other results; further questioning the<br />

methods validity.<br />

Whilst this study did not provide any definitive conclusions, it is based upon an very<br />

reasonable idea which could produce interesting results. If it were <strong>to</strong> be adapted <strong>to</strong><br />

studying these additions, para-butenyl 210n might serve a similar function; parasubstitution<br />

is preferred since there have been no successful additions <strong>to</strong> orthosubstituted<br />

oxazolines (vide supra).<br />

t-Bu<br />

O<br />

t-Bu<br />

RM<br />

t-Bu<br />

O<br />

t-Bu<br />

R<br />

t-Bu<br />

HO<br />

t-Bu<br />

R<br />

Ph<br />

O<br />

Ph<br />

NLi<br />

152<br />

O<br />

t-Bu<br />

t-Bu<br />

O<br />

t-Bu<br />

R<br />

t-Bu<br />

O<br />

t-Bu<br />

t-Bu<br />

t-Bu<br />

trans-152<br />

Scheme 2.33 – isomerisation of cis-alkenes<br />

R<br />

151 −<br />

In his study of the nucleophilic addition of Grignard reagents, Reinhard Hoffmann<br />

<strong>to</strong>ok the measures of bond isomerisation <strong>to</strong> its logical conclusion; the racemisation of<br />

the reacting stereocentre as a radical clock. 86 <strong>The</strong> first attempt at achieving this was a<br />

87


2.4 – Mechanistic discussion<br />

Gringard derived from norbornane, which was found <strong>to</strong> have an innate stereochemical<br />

bias in its reaction. However, Hoffmann and co-workers succeeded in generating the<br />

chiral secondary Grignard 154 in 90% e.e. from sulfoxide 153. In their reaction with<br />

achiral substrates any isomerisation of the nucleophilic centre would due <strong>to</strong> a radical<br />

intermediate; with a barrier <strong>to</strong> rotation estimated at only 0.5 kcal mol -1 this probe<br />

should identify even the most short-lived radicals.<br />

Ph<br />

Cl<br />

S Ar<br />

O<br />

153<br />

EtMgCl (5 eq)<br />

−78 <strong>to</strong> −30 °C<br />

Ph<br />

O<br />

MgCl<br />

E =<br />

R H<br />

< −30 °C<br />

154 90% e.e.<br />

R<br />

OH<br />

155<br />

Ph<br />

Entry E Product Yield / % e.e. / %<br />

a R = Ph 155 84 84 & 88<br />

b R = p-OMe C 6 H 4 155 82 84 & 89<br />

c R = C 6 F 6 155 90 43 & 47<br />

d CO 2 HO 2 C-CH(Et)Bn 80 92<br />

e Ph 2 CO Ph 2 CO- CH(Et)Bn 85 12<br />

Table 2.11 – addition of Hoffmann’s chiral Grignard <strong>to</strong> electrophiles 108<br />

<strong>The</strong>se results show a surprising preference for polar addition, with even addition <strong>to</strong><br />

benzophenone apparently exhibiting some polar nature. 108<br />

Confirmation of absolute<br />

configuration showed that the polar reaction proceeded with retention. Intriguingly,<br />

the diastereomers resulting from addition <strong>to</strong> aldehydes were of different optical purities<br />

(entries a-c, Table 2.11), even though they were isolated from the same reaction; no<br />

explanation is offered for this outcome.<br />

Instead of identifying partial radical nature, it is of course possible that all or some of<br />

these reactions are entirely radical in nature, and that any apparent polar nature is<br />

because the rate of radical combination is greater that bond rotation of 154•. However<br />

this seems unlikely, and with the uncertainty of how <strong>to</strong> interpret data from other kinetic<br />

methods, radical clocks such as 154 appears <strong>to</strong> offer the best measure of SET<br />

behaviour, and the use of an organolithium equivalent would almost certainly offer<br />

illumination about the mechanism of the dearomatising addition. Indeed, the 3:1<br />

diastereomeric ratio of the exocyclic centre observed upon addition of s-BuLi could be<br />

88


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

viewed as evidence of an SET reaction. One could dispute that rather than<br />

representing a kinetic resolution of the s-BuLi in solution, that addition of both s-butyl<br />

enantiomers is equally likely and that the bond rotation occurs in the butyl radical<br />

before RC.<br />

2.4.3 Aggregation in organolithium chemistry<br />

Whilst the mechanistic studies are inconclusive, another area that might shed light on<br />

understanding the dearomatising chemistry is the role of aggregates which are<br />

implicated by the sensitivity of the reaction <strong>to</strong> the order of addition and solvent.<br />

Aggregates form since a monodentate alkyl ligand is unable <strong>to</strong> adequately stabilise its<br />

lithium counterpart, which is normally tetracoordinate. <strong>The</strong>se aggregates can shift <strong>to</strong><br />

their entropically favoured state by the addition of Lewis bases, such as THF, TMEDA<br />

and DMPU, which displace organic ligands around the cation. Deaggregation is often<br />

associated with making organolithiums more reactive since the organic portion no<br />

longer coordinates as many lithium centres, but this has been hard <strong>to</strong> prove. Indeed,<br />

Collum has authored a critique of the triad of strong solvation, lower aggregation and<br />

higher reactivity, by discussing examples of the behaviour of TMEDA in<br />

organolithium reactions. 109<br />

Collum highlights that the lower aggregation means higher reactivity assumption is<br />

fundamentally flawed since by stabilising lower aggregates of organolithiums, one is<br />

lowering the ground state energy of the reactants without necessarily lowering the<br />

energy of the transition state. Since it is the transition state we hope <strong>to</strong> stabilise<br />

observed increases in reaction rate cannot be used <strong>to</strong> infer lower aggregation. Indeed,<br />

a stronger ligand binding lithium would be less labile and the cation disinclined <strong>to</strong><br />

coordinate the substrate.<br />

Transition state stabilisation seems especially important when we consider that under<br />

normal conditions, dearomatisation is a very unfavourable process and it is likely that<br />

dearomatised intermediates require significant stabilisation. Hence the subtleties of<br />

how stabilisation takes place are important, and might explain why only certain cosolvents<br />

were found <strong>to</strong> assist dearomatisation. An example of a similarly solventspecific<br />

effect was observed by Streitwieser who found that the aromatic enolate of p-<br />

89


2.4 – Mechanistic discussion<br />

phenylisobutyrophenone is strongly coordinated by HMPA, weakly by DMPU, and<br />

that PMDTA and TMEDA have no effect. 110<br />

Unfortunately the role of co-solvents in organolithium chemistry is not thoroughly<br />

unders<strong>to</strong>od. <strong>The</strong> most studied co-solvent is hexamethylphosphoramide (HMPA) since<br />

it is an exceptional ligand for Li + and its interactions can be moni<strong>to</strong>red by IR and 31 P<br />

NMR spectroscopy. Reich recently studied the correlation between 1,2- and 1,4-<br />

addition of dithiane <strong>to</strong> enone systems and its HMPA-induced aggregation state<br />

(Scheme 2.34).<br />

O<br />

Li O<br />

S<br />

S S<br />

−78 °C<br />

HO S<br />

THF<br />

R<br />

S<br />

S<br />

157<br />

100 : 0<br />

+ 2 eq HMPA<br />

5 : 95<br />

Scheme 2.34 – the influence of co-solvent on addition <strong>to</strong> cyclohexenone 111<br />

<strong>The</strong> aggregation state of dithiane 157 was measured in solution and the results<br />

compared these <strong>to</strong> the regioselectivity of parallel reactions. Whilst a direct correlation<br />

was not observed, Reich concludes that the 1,4-addition is performed by trace amounts<br />

of organolithium existing as solvent-separated ion pairs (SIPs). In coming <strong>to</strong> this<br />

conclusion, he invokes a Curtin-Hammett pre-equilibrium between the predominant<br />

contact ion pairs (CIPs) and the lower concentration SIPs. Whether the conclusions of<br />

Reich are wholly valid, his experiments clearly show how an organolithium can switch<br />

its reactivity depending on its solvation.<br />

Coordinating ligands can also have unpredictable effects on the aggregation state of an<br />

organolithium. For example, Reich and co-workers also found that whilst aryllithiums<br />

158 exist as monomers in THF, addition of excess HMPA can cause them <strong>to</strong> redimerise<br />

<strong>to</strong> form bis-chelated triple ions 158-T, with one lithium cation completely<br />

solvated by HMPA. 112 <strong>The</strong> reactivity of these triple anions has not been studied, but<br />

that HMPA is found <strong>to</strong> promote aggregation highlights that many different<br />

organolithium species can exist in solution.<br />

90


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

R<br />

Li<br />

HMPA<br />

R<br />

Li<br />

R<br />

Li(HMPA) n<br />

R<br />

R R<br />

158 158-T<br />

R = Me, & i-Pr<br />

65-80% 158-T<br />

Scheme 2.35 – aggregation of aryllithiums by HMPA 112<br />

2.4.3.a <strong>The</strong> role of aggregation in the dearomatising addition<br />

<strong>The</strong>se studies show just how complex the reactivity of organolithiums can be, and with<br />

numerous possible intermediates, it is perhaps surprising that high degrees of control<br />

are ever achieved. <strong>The</strong> sensitivity of the dearomatising addition <strong>to</strong> solvent and order of<br />

addition shown (section 2.2) indicates that transient organolithium species, may be<br />

responsible for the dearomatising addition, and that these species – either reagent or<br />

reaction intermediates – are stabilised by DMPU. <strong>The</strong> time profile of the reaction<br />

(Scheme 2.8) indicates that ortho-lithiation and dearomatisation occur in parallel, so<br />

mixed aggregates are unlikely <strong>to</strong> either accelerate or inhibit the reaction. Excess<br />

organolithium appeared <strong>to</strong> have little impact, implying that product does not<br />

coordinate the reagent as, for example, LDA can. Finally, in common with other<br />

organolithium reactions, some co-solvent was essential <strong>to</strong> the reaction, whilst excess<br />

was found <strong>to</strong> promote side reactions.<br />

<strong>The</strong> reactivity of the nucleophiles further indicates that aggregation might be<br />

important, since the organolithium must be transferred in its native state (Table 2.5,<br />

Table 2.6). In hydrocarbon solvent, n-BuLi exists as a hexamer, and t-BuLi is a<br />

tetramer; below concentrations of 0.1M i-PrLi is also a tetramer but cryoscopic<br />

measurements of more concentrated solutions, and its crystalline form as hexameric; 113<br />

it’s likely that s-BuLi has similar aggregation states as i-PrLi, even though it is<br />

normally reported <strong>to</strong> be a tetramer. 14 Whilst it is unlikely that the reaction occurs with<br />

the organolithiums in their native state, it is possible that deaggregation in the presence<br />

of DMPU induces the formation of certain reactive species. <strong>The</strong>refore primary and<br />

tertiary organolithiums may not react simply because the deaggregation pathway they<br />

follow does not include aggregates which permit dearomatising addition <strong>to</strong> occur.<br />

91


2.5 Summary & Future Work<br />

It is unsurprising that the development of a reaction that evaded leading researchers for<br />

decades is challenging, and that careful reaction conditions might be necessary.<br />

Currently what is happening in the flask is unclear, but when the correct system is<br />

found encouraging improvements can be achieved; as demonstrated by the reaction of<br />

fluorinated oxazolines in <strong>to</strong>luene. A broader range of organolithiums, especially ones<br />

containing heteroa<strong>to</strong>ms would make the reaction more synthetically useful, in<br />

particular dimethylphenylsilyllithium would be particularly amenable <strong>to</strong> future<br />

synthetic manipulation. Importantly, it seems that once a system is found, the reaction<br />

is scalable, with two gram reactions proceeding in excellent yield without the need for<br />

especially rigorous conditions.<br />

<strong>The</strong> dearomatising cyclisation described in Scheme 2.31 highlights some possible<br />

areas <strong>to</strong> explore (Scheme 2.36). Since the aromatic system reacted with the lithium π-<br />

allyl system 140 (Scheme 2.29) <strong>to</strong> give a 6 membered ring, a 5-membered cyclisation<br />

should be move favourable, and certainly more stereoselective. This could be<br />

achieved through homologues 159 or 160, but since a non-pericyclic reaction is<br />

suspected 62 conjugation with the aromatic system (160) would disfavour cyclisation.<br />

If aryl ether 159-O lithiated at the allylic position in the absence of an adjacent<br />

heteroa<strong>to</strong>m, it would form an allyl system similar <strong>to</strong> 159, and might undergo<br />

cyclisation. Alkenes 159-C or 161 might also generate π-allyl intermediates 159, but<br />

benzylic lithiation could inhibit cyclisation. This could be minimised by use of<br />

lithium-halogen exchange or other related methods.<br />

Ox*<br />

X<br />

159<br />

Li<br />

Ox*<br />

160<br />

Li<br />

Ox*<br />

Ox*<br />

Ox*<br />

O<br />

O<br />

159-O 159-C<br />

Scheme 2.36 – allyl oxazolines promoting 5-membered dearomatising cyclisation<br />

161<br />

92


Chapter 2 – Dearomatising additions <strong>to</strong> aryl oxazolines<br />

Further suggestions for future work have been made throughout this discussion and a<br />

number have already been undertaken. Future improvements in the methodology will<br />

require further close study of the reaction conditions, which may prove <strong>to</strong> be substrate<br />

dependent. A number of ways <strong>to</strong> improve reactions involving organolithiums have<br />

recently be suggested by Collum. 67<br />

93


Chapter 3 – Oxazoline synthesis & removal<br />

Chapter 3 – Oxazoline Synthesis and Removal:<br />

Making & Breaking an Auxiliary<br />

<strong>The</strong> previous chapter introduced an asymmetric reaction guided by a pendant<br />

oxazoline group. Such s<strong>to</strong>ichiometric “auxiliary” chemistry can only be of synthetic<br />

use if the stereoinducing group can be easily incorporated in<strong>to</strong> a synthesis, meaning i)<br />

it must be easily installed and ii) easily removed. <strong>The</strong>se two measures can be more<br />

important in developing a chiral auxiliary than the stereoselectivity of the intervening<br />

reaction, since diastereoisomers can in principle be separated before its removal.<br />

Hence the facile synthesis and removal of the oxazoline moiety without loss of optical<br />

purity is essential <strong>to</strong> making the dearomatising methodology synthetically useful.<br />

3.1 <strong>The</strong> Synthesis of 2,4,5-Oxazolines<br />

2,4,5-Substituted oxazolines are generally synthesised from a carboxylic acid<br />

derivative and a β-amino alcohol which contains both stereogenic centres.<br />

<strong>The</strong><br />

oxazolines are required in high optical purity, both enantiomers should be equally<br />

accessible, and their synthesis should <strong>to</strong>lerate a range of aryl substituents. Whilst<br />

preliminary studies in the previous chapter required a number of different C4 and C5<br />

substituents, the synthesis of diphenyl oxazolines 101 will be the focus of this section.<br />

Ph<br />

5<br />

O N<br />

2<br />

Ar<br />

101<br />

Ph<br />

4<br />

3.1.1 Literature methods for synthesis<br />

Many literature methods are inappropriate for the synthesis of optically pure<br />

oxazolines 101 since they would proceed through achiral intermediates such as<br />

epoxides or electrocyclic transition states, which also presents problems for a number<br />

of asymmetric catalysis. 114<br />

Discussion will be restricted <strong>to</strong> methods which have been<br />

shown <strong>to</strong> give enantiomerically pure 2-aryloxazolines in reasonable yield;<br />

comprehensive summaries of the recent literature have been reviewed by Meyers 24 and<br />

Ager. 115<br />

95


3.1 – Oxazoline synthesis<br />

3.1.1.a Hydroxyamides – alcohol activation<br />

O<br />

R<br />

X<br />

H 2 N<br />

OH<br />

O<br />

R<br />

H<br />

N<br />

OH<br />

SOCl 2 , Na 2 CO 3<br />

O N<br />

Δ<br />

R<br />

c. 70%<br />

116<br />

Scheme 3.1 – unfunctionalised oxazolines via amides<br />

Oxazolines are traditionally made by condensation of β-amino alcohol with carboxylic<br />

acids or derivatives, before cyclisation by azeotropic reflux or treatment with excess<br />

thionyl chloride (Scheme 3.2). 117<br />

This method works well for generating oxazolines<br />

without a C5 stereocentre, although significant amounts of the intermediate chloramide<br />

is often isolated, diminishing the yield. A number of milder methods for activating the<br />

amido alcohol have been developed, which are compatible with more sensitive<br />

functional groups.<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

H<br />

165a<br />

Ph<br />

O<br />

N<br />

H<br />

166<br />

OH<br />

Ph<br />

OH<br />

Me<br />

DIC 1 eq<br />

Cu(OTf) 2 5%,<br />

dioxane, Δ 6 hr<br />

DIC 1 eq<br />

Cu(OTf) 2 5%,<br />

THF, μω 5 min<br />

Ph<br />

Ph<br />

O<br />

N<br />

Ph<br />

101a<br />

O<br />

Ph<br />

110<br />

N<br />

Ph<br />

Me<br />

78%<br />

> 95:5 dr<br />

88%<br />

> 95:5 dr<br />

R<br />

O<br />

N<br />

H<br />

i-Pr<br />

NH<br />

O<br />

N i-Pr<br />

R<br />

167<br />

61-98%<br />

16 examples<br />

Scheme 3.2 – cyclisation of amides by the method of Linclau 118<br />

Linclau recently developed a method using the coupling agent diisopropylcarbodiimide<br />

(DIC) <strong>to</strong> promote displacement of the newly activated alcohol. 118<br />

Catalytic copper<br />

triflate is added <strong>to</strong> promote in situ formation of isoureas 167 and is shown not <strong>to</strong> affect<br />

the cyclisation step which proceeds exclusively in an S N 2 manner for the examples<br />

shown. This method is particularly appropriate since they make not only diphenyl<br />

oxazoline 101a, but also the norephedrine-derived oxazoline 110 studied in the<br />

previous chapter.<br />

96


Chapter 3 – Oxazoline synthesis & removal<br />

HO<br />

Ph<br />

Ph<br />

OH<br />

Ph<br />

Ph Ph<br />

Ph<br />

Ph<br />

NH<br />

O<br />

H<br />

N<br />

O<br />

NH<br />

Ph<br />

i) MeSO 2 Cl, Et 3 N<br />

ii) NaOH, MeOH,<br />

H 2 O, Δ 4 hr<br />

O<br />

N<br />

H<br />

N<br />

O<br />

N<br />

168<br />

53%<br />

Scheme 3.3 – cyclisation of amides by mesylation 119<br />

Activation has also been achieved by Du and co-workers, by mesylation before<br />

cyclisation under strongly basic conditions (Scheme 3.3). Although an extra step is<br />

required in the isolation of the mesylate, shorter reaction times and cheaper reagents<br />

somewhat offset this practicality. 119 Whilst the synthesis of bis-oxazoline ligand 168<br />

proceeds in lower yield than the Linclau method, each cyclisation effectively takes<br />

place in 70-75% yield. In light of its simplicity it is somewhat surprising that this<br />

method has not been used more widely; given that the diastereoselectivity is not<br />

reported it is unclear how general this method is.<br />

3.1.1.b Acyl aziridines<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

Ph<br />

N<br />

100a<br />

Ph<br />

SiO 2 , CH 2 Cl 2<br />

O N<br />

Ph<br />

101a<br />

94%<br />

> 99:1 dr<br />

> 99:1 er<br />

64<br />

Scheme 3.4 – silica catalysed rearrangement of benzoyl aziridines<br />

Diphenyl oxazoline 101a was first synthesised by Purewal 63 and Cabedo 64 by the<br />

rearrangement of benzoyl aziridine 100a on silica, with only a single stereoisomer<br />

isolated. Although this was unexpected at the time, there is significant precedent for<br />

the ring expansion of acyl aziridines catalysed by iodide, 120 heat, 120 Lewis acid, 121<br />

aqueous acid, 122 and silica, 123 although the stereochemical outcome of the reaction had<br />

not generally been studied.<br />

97


3.1 – Oxazoline synthesis<br />

O<br />

Ar<br />

OH<br />

i) SOCl 2<br />

ii)<br />

HN<br />

O<br />

Ar<br />

N<br />

86%<br />

H 2 SO 4 , Et 2 O<br />

rt, 16 hr<br />

O<br />

Ar<br />

N<br />

75%<br />

Ar =<br />

NC<br />

122<br />

Scheme 3.5 – acid catalysed rearrangement of benzoyl aziridines<br />

<strong>The</strong> aziridine nitrogen is unable <strong>to</strong> fully participate in the stabilising n N →π * C–O<br />

interaction since it is constrained in a three membered ring. This is seen in a crystal<br />

structure obtained by Lectka and co-workers in which the aziridine C–N bonds are 68°<br />

out of the C=O plane, and longer than other secondary amines. 121 <strong>The</strong>refore the partly<br />

pyramidal acyl aziridines have reactivity akin <strong>to</strong> amines, and it is postulated by Lectka<br />

that the nitrogen basicity drives the rearrangement. This has been borne out by his<br />

studies which show that the rearrangement takes place in the presence of azaphilic<br />

Lewis acids (Cu II , Sn II , Zn II ) but not oxophilic ones (Yb III , Ti IV , Sb V , Al III , 122 BF 122 3 ).<br />

Another, and perhaps the main, impetus for the rearrangement would be the<br />

developing n N →π* C–O interaction in the transition state, which no doubt explains why<br />

the reverse reaction is not observed.<br />

Ar<br />

N<br />

O<br />

Cu(OTf) 2<br />

THF<br />

Ph<br />

Ph<br />

Cu(OTf) 2<br />

O N<br />

N<br />

O N<br />

THF<br />

Ar<br />

Ph O<br />

Ph<br />

76-89%<br />

169 4 examples 171 172<br />

M<br />

N<br />

O<br />

Ar<br />

170<br />

Scheme 3.6 – acid catalysed rearrangement of aziridines 121<br />

In this work, Leckta synthesises a number of cis-substituted oxazolines 169, and<br />

transition state calculations suggest a heterolytic process via cation 170 rather than a<br />

concerted mechanism favoured by other authors. 120 Under these conditions, optically<br />

pure aziridine 171 rearranges <strong>to</strong> give the known oxazoline 172 with complete regioand<br />

stereoselectivity; the regioselectivity is consistent with formation of the more<br />

stable cation, whilst the stereoselectivity is attributed <strong>to</strong> the formation of tight ion<br />

pairs. No yield is given for this final reaction in either the text or supporting<br />

information.<br />

98


Chapter 3 – Oxazoline synthesis & removal<br />

3.1.1.c Activated carbonyl<br />

Whilst the amide methods form the C–O bond of the oxazoline with inversion,<br />

condensation of the amino alcohol with an activated carbonyl proceeds with retention<br />

at the C5 stereocentre. <strong>The</strong>se methods would therefore allow the same amine <strong>to</strong> be<br />

used <strong>to</strong> make epimeric oxazolines.<br />

O<br />

NH 2<br />

i) (Et 3 O)BF 4 , CH 2 Cl 2<br />

Ph<br />

O<br />

N<br />

OMe<br />

R<br />

ii)<br />

Ph<br />

HO<br />

OMe<br />

NH 2 Δ<br />

38<br />

R<br />

83-94%<br />

3 examples<br />

Scheme 3.7 – oxazolines from primary amides 32<br />

Although Meyers published a number of ways <strong>to</strong> make oxazolines, his preferred<br />

method for making chiral oxazolines 38 was via an imidate formed in situ before<br />

addition of the desired amino alcohol. 32 This method has been used for a wide range<br />

of naphthalenes, and since it is a retentive reaction, the stereochemistry and optical<br />

purity of the product depends on the amino alcohol used.<br />

MeO<br />

OMe<br />

OMe<br />

Ph<br />

173<br />

R<br />

HO<br />

R'<br />

NH 2<br />

TFA, DCE<br />

Δ 4 hr<br />

R<br />

O<br />

Ph<br />

N<br />

R<br />

88-97%<br />

3 examples<br />

124<br />

Scheme 3.8 – oxazolines from ortho esters<br />

An analogous method published more recently by Meyers uses aryl ortho esters 173 <strong>to</strong><br />

give a small selection of aryl oxazolines in good yield. 124<br />

Since ortho esters can be<br />

made by methanolysis of nitriles, this would offer another route <strong>to</strong> their synthesis. <strong>The</strong><br />

zinc chloride catalysed condensation of aromatic nitriles with amino alcohols under<br />

reflux has also been used <strong>to</strong> synthesise 2-aryl oxazolines, but has only been used <strong>to</strong><br />

make a small range of compounds. 125<br />

99


3.1 – Oxazoline synthesis<br />

3.1.2 General strategies<br />

Retrosynthesis of oxazolines 101 using the three methods outlined reveals that each<br />

would require a different amine. However aziridine 173 might be made from β-amino<br />

alcohol 174.<br />

Retention<br />

Ph<br />

O N<br />

Ph<br />

Ar<br />

100<br />

aroyl aziridine<br />

Retention<br />

B<br />

HN<br />

Ph<br />

173<br />

Ph<br />

<strong>Route</strong> B<br />

acyl aziridines<br />

Inversion<br />

Ph Ph Inversion<br />

O N<br />

Ar<br />

101<br />

Ar<br />

Ph<br />

O<br />

N<br />

H<br />

O<br />

Ph<br />

R<br />

benzoyl amide,<br />

activated alcohol<br />

Retention<br />

A<br />

Ph<br />

Ph<br />

HO NH 2<br />

174<br />

<strong>Route</strong> A<br />

Amide alcohols<br />

Retention<br />

H<br />

R O<br />

O<br />

Ar<br />

N<br />

Ph<br />

Ph<br />

activated benzoyl<br />

amide<br />

Retention<br />

C<br />

Ph<br />

Ph<br />

HO NH 2<br />

175<br />

<strong>Route</strong> C<br />

Activated carbonyl<br />

Scheme 3.9 – retrosynthesis of diphenyl oxazoline 101<br />

Which route is preferred will depend on ease of access <strong>to</strong> the enantiomerically pure<br />

amine, the optical purity of the resulting oxazolines, and the overall yield of oxazoline<br />

formation.<br />

3.1.3 Amine synthesis<br />

<strong>The</strong> large scale synthesis (170 g) of amino alcohol 174 from trans-stilbene was<br />

completed by Sharpless in 81% overall yield and near complete enantiomeric purity. 126<br />

<strong>The</strong> synthesis was completed in comparable yield (Scheme 3.10), with substitution of<br />

CDI for dimethyl carbonate, making cyclic carbonate 177 in quantitative yield instead<br />

of 85%.<br />

100


Chapter 3 – Oxazoline synthesis & removal<br />

Ph<br />

Ph<br />

AD mix α, Me 2 SO 2 NH 2<br />

t-BuOH/H 2 O, 0 °C 2 d<br />

O<br />

Ph Ph CDI, CH 2 Cl 2<br />

O O<br />

HO OH rt 16 hr<br />

98%<br />

Ph Ph<br />

176 177 100%<br />

NaN 3 , DMF<br />

Ph<br />

Ph<br />

H 2 , Pd/C<br />

Ph<br />

Ph<br />

110 °C 2 d<br />

HO<br />

178<br />

N 3<br />

HCl/EtOH<br />

HO<br />

174<br />

NH 2<br />

82% (2 steps)<br />

>99:1 e.r.<br />

Scheme 3.10 – modified Sharpless synthesis of amino alcohol 174<br />

Aziridine 173 was made from the products of this synthesis either by intramolecular<br />

Mitsunobu reaction of amino alcohol 174, or treatment of azide 178 with<br />

triphenylphosphine. 64<br />

phosphazide.<br />

Ph<br />

HO<br />

178<br />

Ph<br />

N 3<br />

<strong>The</strong> latter reaction presumably proceeding via a Staudinger-type<br />

PPh 3 , Et 2 O<br />

rt 2 hr<br />

HN<br />

Ph<br />

173<br />

Ph<br />

64%<br />

(from carbonate)<br />

Ph<br />

HO<br />

174<br />

Ph<br />

NH 2<br />

Ph<br />

PPh 3 , DIAD<br />

HN<br />

Et 3 N, THF<br />

Ph<br />

rt 18 hr 92%<br />

173<br />

Scheme 3.11 – aziridine synthesis<br />

<strong>The</strong> asymmetric synthesis of amino alcohol 175 is not trivial since most obvious<br />

intermediates such as cis-stilbene oxide, 179, are meso. It should be possible <strong>to</strong> invert<br />

the alcoholic centre of 174 by Mitsunobu reaction after deactivating the amine as the<br />

carbamate, by the method of Lipshutz. 127 However this is presently deemed<br />

unnecessary since the racemic amino alcohol can be quickly synthesised (Table 3.1).<br />

101


3.1 – Oxazoline synthesis<br />

mCPBA<br />

O<br />

NH 4 OH, MeOH<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

CH 2 Cl 2<br />

Ph Ph Conditions<br />

90%<br />

179<br />

HO NH 2<br />

± 175<br />

Entry NH 4 OH:MeOH Temp / °C Time 175 (SM) / %<br />

a 1:1 100 Δ 24 hr 55 (25)<br />

b 3:1 120 µω 2 min 15 (85)<br />

c 3:1 140 µω 20 min 93 (5)<br />

Table 3.1 – synthesis of racemic amino alcohol<br />

<strong>The</strong> improvement seen under microwave conditions is believed <strong>to</strong> be due <strong>to</strong> the use of<br />

a sealed vessel increasing the partial pressure of ammonia, but is also assisted by a<br />

particularly easy isolation which only requires filtration of the cool reaction mixture.<br />

<strong>The</strong> synthesis of ±175 would be made particularly a<strong>to</strong>m efficient if an oxidant such as<br />

dimethyldioxirane or hydrogen peroxide were used for the epoxidation. 128<br />

3.1.4 Oxazoline synthesis<br />

<strong>The</strong> availability of only two of the three amines in near optical purity meant that the<br />

amide and aziridine methods (Scheme 3.9) are the remaining viable routes <strong>to</strong> the<br />

synthesis of enantiomerically pure diphenyl oxazolines. It is important <strong>to</strong> note that the<br />

amine syntheses above allow either enantiomer <strong>to</strong> be synthesised. <strong>The</strong> third method is<br />

still presented below, since it allows the synthesis of racemic diphenyl oxazoline as<br />

well as most of the other oxazolines studied in the previous chapter.<br />

102


Chapter 3 – Oxazoline synthesis & removal<br />

3.1.4.a Method A: hydroxyamide activation<br />

O<br />

Cl<br />

R<br />

Ph<br />

Ph<br />

HO<br />

(1.2 eq)<br />

NH<br />

174 2<br />

CH 2 Cl 2 , Et 3 N<br />

O<br />

H<br />

N<br />

Ph<br />

OH<br />

Ph<br />

DIC 1 eq<br />

Cu(OTf) 2 5%<br />

Conditions<br />

Ph<br />

R<br />

R<br />

165 101<br />

O<br />

N<br />

Ph<br />

d.r. >95:5<br />

e.r. >99:1<br />

Entry R 165 / % T ‡ / °C t 101 / % Compound<br />

a H 99 105 Δ 7 hr 65 101a<br />

b H 99 150 µω 20 min 58 101a<br />

c 4-OMe 99 140 µω 30 min 48-72 101b<br />

d ** 4-OMe 98 120 Δ 12 hr 46 101b<br />

e 3-OMe 96 120 Δ 17 hr 39 101c<br />

f 2-OMe 99 120 Δ 17 hr 50 101i<br />

g 70 4-F 61 120 Δ 16 hr 42 101e<br />

h 4-Ph 83 ‡ 120 Δ 17 hr 43 101f<br />

i 4-CN 41 ‡ 150 µω 20 min 53 101g<br />

‡ from carboxylic acid *reactions under reflux performed in dioxane, microwave reaction<br />

in THF **10 gram reactions<br />

Table 3.2 – synthesis of oxazolines via amides (<strong>Route</strong> A)<br />

Linclau had previously synthesised 2,4,5-triphenyl oxazoline 101a in 78% yield with<br />

good diastereoselectivity (section 3.1.1.a). Whilst this result could not be reproduced<br />

(entry a) the method was amenable <strong>to</strong> a range of 2-aryl groups, although yields were<br />

found <strong>to</strong> vary significantly, even when repeating the same reaction (entry c). Much of<br />

the losses are believed <strong>to</strong> be unreacted starting material, which is hard <strong>to</strong> quantify since<br />

it is inseparable from the urea. Longer reaction times did not improve yields,<br />

presumably due <strong>to</strong> decomposition of the product. Recently Karlubíková has<br />

synthesised oxazoline 101b by mesylation and cyclisation of amide 165b (vide supra)<br />

in the slightly higher 76-86% yield. 66<br />

103


3.1 – Oxazoline synthesis<br />

3.1.4.b Method B: ring expansion of benzoyl aziridines<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

Cl<br />

HN<br />

173<br />

Ph<br />

O<br />

N<br />

Ph<br />

SiO 2 , CH 2 Cl 2<br />

O<br />

N<br />

R<br />

Et 2 O, petrol,<br />

Et 3 N, -10 °C<br />

R<br />

R<br />

100 101<br />

e.r. >95:5<br />

Entry R 100 / % SiO 2 t 101 / % d.r.<br />

a H 84 “excess” 18 hr 94 64 >99:1<br />

b 4-OMe 89 “excess” 8 d 58 99:1<br />

c 4-OMe 89 10 x wt 7 hr 80 >95:5<br />

d 3-OMe 87 10 x wt 16 hr 85 >95:5<br />

Table 3.3 – synthesis of oxazolines via aziridines (<strong>Route</strong> B)<br />

Aziridines 100 were made under low solubility conditions <strong>to</strong> precipitate the<br />

triethylammonium salt <strong>to</strong> minimise chloride attack of the aziridine ring. 129 Initial<br />

studies of the aziridine rearrangement made it clear that “excess” silica was not<br />

sufficient for the reaction and known quantities were used. Parallel experiments<br />

showed that phenyl aziridine 100a rearranged approximately twice as quickly as paraanisoyl<br />

aziridine 100b, in disagreement with the observations of Lectka (section<br />

3.1.1.b) but consistent with later results. <strong>The</strong> transformation of aziridine 100b was<br />

also attempted in the presence of sodium iodide in ace<strong>to</strong>ne, 120 but no oxazoline was<br />

detected after 10 days. This is consistent with the findings of Meyers, who postulated<br />

that iodide only catalysed the rearrangement of electron-deficient arylaziridines. 122<br />

Whilst HPLC analysis of the product oxazolines showed them <strong>to</strong> be optically pure,<br />

some epimeric oxazoline was isolated (entry b) and characterised by comparison with<br />

known sample. Further studies in the group showed that under identical conditions<br />

syn-aziridine 180 gave a 2:1 cis:trans mixture (Scheme 3.12), 130 not dissimilar <strong>to</strong> the<br />

observations of Aggarwal who found a similar cis-aziridine rearranged in a 3:1<br />

trans:cis ratio, also on silica. 123 A stereoselective reaction is consistent with the<br />

cationic mechanism proposed by Lectka (vide supra).<br />

104


Chapter 3 – Oxazoline synthesis & removal<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

Ph<br />

SiO 2 , CH 2 Cl 2<br />

O<br />

N<br />

180<br />

109a<br />

dr 2:1<br />

Scheme 3.12 – stereoselectivity of aziridine rearrangement<br />

Since the reagents for the second step of the reaction were relatively inert, and<br />

numerous methods exist <strong>to</strong> couple acids and amines, a one-pot method of oxazoline<br />

synthesis was sought.<br />

O<br />

OH<br />

R<br />

HN<br />

Ph<br />

173<br />

Ph<br />

Carbodiimide<br />

SiO 2 , CH 2 Cl 2<br />

Ph<br />

O<br />

N<br />

R<br />

101<br />

Entry R Carbodiimide time / d 173 : 100 : 101*<br />

a H DIC 2 21 : 8 : 71<br />

b H DIC 8 7 : 7 : 86<br />

c H EDC.HCl 1.3 0 : 7 : 93<br />

d 4-F DIC 2.5 1 : 37 : 62<br />

e 4-Ph DIC 2.5 20 : 19 : 61<br />

f 4-OMe DIC 2 60 : 0 : 40<br />

g 4-OMe DIC 10 85 : 0 : 15<br />

* crude 1 H NMR ratio of reaction mixture<br />

Table 3.4 – one-pot synthesis of oxazolines via aziridines (<strong>Route</strong> B)<br />

Whilst the initial results were promising, extensive studies by Harvey found reaction<br />

times <strong>to</strong> be highly substrate dependent and could not be improved even with the<br />

addition of Lewis acid. 130<br />

<strong>The</strong> use of EDC hydrochloride seemed promising (entry c),<br />

but upon purification the product of chloride attack on the aziridine ring was isolated,<br />

indeed isolated yields were often poor. This method was used <strong>to</strong> synthesise allyl<br />

oxazoline 101j, although reaction was slow, and purification of the final alkylated<br />

product was problematic (Scheme 3.13).<br />

Ph<br />

105


3.1 – Oxazoline synthesis<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

OH<br />

OH<br />

HN<br />

Ph<br />

173<br />

Ph<br />

EDC.HCl<br />

SiO 2 , CH 2 Cl 2<br />

rt, 30 hr<br />

O<br />

N<br />

101k<br />

AllylBr, K 2 CO 3<br />

DMF, NaI<br />

OH<br />

57%<br />

(80% conv.)<br />

O<br />

N<br />

101j<br />

O<br />

38%<br />

3.1.4.c Method C: benzyl imidate<br />

Scheme 3.13 – synthesis of O-allyl oxazoline<br />

O NH 2<br />

i) (Et 3 O)BF 4 (1.1 eq)<br />

CH 2 Cl 2 , rt 16 hr<br />

ii)<br />

1.2 eq<br />

R 1<br />

R 1<br />

O<br />

N<br />

R 2<br />

R<br />

HO<br />

Δ<br />

16 hr<br />

R 2<br />

NH 2<br />

R<br />

Entry R R 1 (R/S) R 2 (R/S) Yield / % Compound<br />

a 4-OMe Ph (S) OMe (S) 72 104b<br />

b H H i-Pr (S) 82 111a<br />

c 4-OMe H i-Pr (S) 58 111b<br />

d H Ph (S) Ph (R) 70 109a<br />

e 4-OMe Ph (S) Ph (R) 66 109b<br />

f H Ph (RS) Ph (RS) 85 ±101a<br />

g 4-OMe Ph (RS) Ph (RS) 86 ±101b<br />

h 3-F Ph (RS) Ph (RS) 82 ±101d<br />

i 4-NO 2 Ph (RS) Ph (RS) 55 ±101h<br />

j c-Hex Ph (RS) Ph (RS) 93 ±101m<br />

Table 3.5 – synthesis of oxazolines via imidate (<strong>Route</strong> C)<br />

Although relatively slow, the one-pot imidate method favoured by Meyers proved <strong>to</strong><br />

be the most reproducible and highest yielding method used. Whilst an excess of the<br />

amino alcohol is used, the previous amide condensations used a similar excess.<br />

Unfortunately oxazolines 101 can only be made racemically since it had not been<br />

possible <strong>to</strong> attain optically pure amino alcohol 175; however this would be possible if<br />

the oxazoline could be cleaved <strong>to</strong> return the optically pure amino alcohol. Recently,<br />

106


Chapter 3 – Oxazoline synthesis & removal<br />

both enantiomers of amino alcohol 175 have become commercially available, but is<br />

approximately four times the price of (+)-174. 131<br />

3.2 Oxazoline Removal<br />

Clean and facile removal of the oxazoline moiety <strong>to</strong> a synthetically useful functional<br />

group without loss of optical purity is essential <strong>to</strong> making the dearomatising<br />

methodology described synthetically useful. Ideally any method developed would<br />

allow recovery of optically pure amino alcohol 175 since this cannot be synthesised by<br />

any other method (section 3.1.3), furthermore the ability <strong>to</strong> recycle material is often<br />

cited as one of the benchmarks of a chiral auxiliary. Ideally two or more orthogonal<br />

methods should be developed <strong>to</strong> aid synthetic design.<br />

3.2.1 Literature methods for removal<br />

Whilst oxazolines have not seen such broad use in synthetic chemistry as other<br />

heterocycles, they are still often taught in synthetic courses as masked carboxylic acids<br />

resistant <strong>to</strong> a range of nucleophiles and reducing agents, yet removable under strong<br />

acid hydrolysis. Whilst such robustness may be beneficial in designing a synthesis, it<br />

otherwise makes removing the oxazoline more challenging.<br />

<strong>The</strong> following literature survey presents three general strategies adopted in unmasking<br />

oxazolines. Only methods compatible with chiral aliphatic substituents are reported,<br />

most are two-step methods, and when possible reference has been made <strong>to</strong> the relay of<br />

optical purity.<br />

3.2.1.a Hydrolysis<br />

<strong>The</strong> most commonly encountered oxazolines in text books are geminal dimethyl<br />

oxazolines 185 where high temperature acid catalysed hydrolysis in ethereal or<br />

alcoholic solvent is suggested for removal <strong>to</strong> give the acid or ester. 6<br />

107


3.2 – Oxazoline removal<br />

O<br />

N<br />

O<br />

OH<br />

3N HCl (aq)<br />

87-95%<br />

Δ<br />

3 examples<br />

D<br />

D<br />

185<br />

Scheme 3.14 – acid hydrolysis of gem-dimethyl oxazolines 132<br />

Whilst this has mainly been used for removal of oxazolines from stable aromatic<br />

systems, Meyers also used acid hydrolysis in his early asymmetric work (Scheme<br />

3.15). 133 This method allowed the chiral amino alcohol 186 <strong>to</strong> be recovered without<br />

loss of optical purity, in fact, the hydrolysis intermediates were isolated and<br />

recrystallised, allowing enantiomeric ratios <strong>to</strong> be improved.<br />

Ph<br />

O<br />

H<br />

Me<br />

N<br />

R<br />

R = Et, n-Pr,<br />

n-Bu<br />

OMe<br />

HCl (aq)<br />

Δ, minutes<br />

Ph<br />

O<br />

H<br />

Me<br />

HCl (aq)<br />

Δ<br />

H<br />

Me<br />

OMe<br />

NH 2 Cl<br />

O<br />

R<br />

CO 2 H<br />

R<br />

i) NaHCO 3<br />

ii) recryst.<br />

Ph<br />

68-79%<br />

4:1 e.r.<br />

3 examples<br />

OMe<br />

NH 2<br />

OH 186<br />

O<br />

H<br />

Me<br />

H<br />

Me<br />

Scheme 3.15 – acid hydrolysis of chiral oxazoline 133<br />

H<br />

N<br />

R<br />

HO<br />

CO 2 H<br />

R<br />

Ph<br />

OMe<br />

4N HCl<br />

Δ 3 hr<br />

51-59%<br />

9:1 e.r.<br />

3 examples<br />

Alternatively, alkaline hydrolysis of N-alkylated oxazolines 187 can be employed <strong>to</strong><br />

reveal the acid (Scheme 3.16) with good retention of stereochemistry since<br />

enantiomeric excesses were generally in proportion <strong>to</strong> the preceding diastereomeric<br />

ratios. Mechanistically, alkylation can be thought of as replacing the first pro<strong>to</strong>nation<br />

in the hydrolysis sequence, although the amino alcohol can no longer be recycled.<br />

Ph<br />

O<br />

R<br />

HO<br />

N<br />

Ph<br />

OMe<br />

MeI, DMSO<br />

rt<br />

Ph<br />

O N<br />

Me<br />

R<br />

HO Ph<br />

187<br />

OMe<br />

KOH (2M)<br />

Δ 8 hr<br />

134<br />

Scheme 3.16 – alkylation-hydrolysis<br />

R<br />

HO<br />

CO 2 H<br />

Ph<br />

55-73%<br />

13 examples<br />

108


Chapter 3 – Oxazoline synthesis & removal<br />

3.2.1.b N-Quaternisation-reduction<br />

More recent methods have identified the lone pair of the oxazoline nitrogen as a<br />

weakness <strong>to</strong> be exploited, with an initial quaternisation step making it more reactive <strong>to</strong><br />

nucleophiles. This approach is typified by the N-alkylation-reduction method<br />

developed by Meyers which proceeds through reduction of oxazolinonium salt 188,<br />

before hydrolysis of the oxazolidine 189 <strong>to</strong> unmask the aldehydes and N-methyl amino<br />

alcohol. 25<br />

O<br />

R<br />

N<br />

MeOTf<br />

NaBH 4<br />

(CO 2 H) 2<br />

O N<br />

Me<br />

O N Me<br />

CH 2 Cl 2 MeOH/THF<br />

THF/H 2 O<br />

R<br />

R<br />

188 189<br />

Scheme 3.17 – alkylation-reduction, general scheme<br />

HO<br />

O<br />

R<br />

NHMe<br />

This became Meyers’ preferred method for oxazoline removal from<br />

dihydronaphthalenes 190 and has been applied <strong>to</strong> much methodology work and a<br />

number of syntheses appearing <strong>to</strong> be generally applicable and maintaining optical<br />

purity through the sequence. <strong>The</strong> main draw back with this method is the use of<br />

methyl triflate which will readily alkylate other functional groups such as ethers and<br />

nitriles and is highly <strong>to</strong>xic. 135,136<br />

Ph<br />

H<br />

O<br />

E<br />

N<br />

Nu<br />

OMe<br />

i) MeOTf, CH 2 Cl 2<br />

then NaBH 4<br />

E<br />

CHO<br />

Nu<br />

R<br />

190<br />

R<br />

ii) H 3 O + 62-97%<br />

>47:1 e.r.<br />

11 examples<br />

Scheme 3.18 – alkylation-reduction-hydrolysis of chiral oxazolines 31<br />

When trying different pro<strong>to</strong>n sources for quenching dearomatising additions, Meyers<br />

found that addition of trifluoroacetic acid also pro<strong>to</strong>nated the oxazoline, giving esters<br />

194 as their TFA salts upon aqueous workup. 34 This is believed <strong>to</strong> proceed via<br />

quaternised oxazoline 193 whose hydrolysis is enhanced by the addition of sodium<br />

sulfate (Scheme 3.19). Oxazoline 191 was unmasked <strong>to</strong> give carbinol 192 in the<br />

synthesis of phyltetralin using this method.<br />

109


3.2 – Oxazoline removal<br />

O<br />

Me<br />

O<br />

N<br />

OMe<br />

i) TFA, H 2 O<br />

OMe<br />

OH<br />

OMe<br />

OMe<br />

OMe<br />

OMe<br />

OMe<br />

MeO<br />

OMe<br />

OMe<br />

191<br />

192<br />

86% MeO OMe<br />

21:4 e.r.<br />

(+)-Phyltetralin<br />

Ph<br />

O NH<br />

R<br />

193<br />

OMe<br />

TFA<br />

ii) LiAlH 4<br />

Na 2 SO 4<br />

H 2 O<br />

MeO<br />

NH 3<br />

O O<br />

Ph<br />

R<br />

194<br />

TFA<br />

Scheme 3.19 – reduction of TFA salt in synthesis 31<br />

Since this technique is generally applied immediately after quenching the<br />

dearomatising addition, the stereochemical fidelity of the process is uncertain,<br />

although Meyers states that no loss in optical purity is observed. Unfortunately the<br />

chemistry of TFA esters such as 194 is not discussed since they are normally reduced<br />

without isolation.<br />

3.2.1.c Reduction<br />

Meyers also demonstrated that reduction of unfunctionalised oxazolines <strong>to</strong> secondary<br />

amines is possible using DIBAlH. 137 Whilst the reduction works well, cleavage of the<br />

resulting amine is problematic, requiring silylation, chlorination, oxidation and<br />

hydrolysis <strong>to</strong> give the aldehyde. Silylation is necessary <strong>to</strong> prevent Grob-type<br />

fragmentation of the N-chloride.<br />

i) TBDMSCl<br />

ii) NCS<br />

Ar<br />

O<br />

N<br />

Ph<br />

OMe<br />

DIBAlH<br />

4 eq, rt<br />

Ar<br />

HN<br />

OMe<br />

OH<br />

Ph<br />

195<br />

70-100%<br />

14 examples<br />

OMe<br />

OMe<br />

H<br />

Al<br />

Ph 2 O<br />

SiO 2<br />

3 Ph<br />

Ar N Ar N<br />

Cl<br />

OTBDMS<br />

OTBDMS<br />

ArCHO<br />

70-75%<br />

4 examples<br />

Scheme 3.20 – direct reduction of oxazoline followed by amine cleavage 137<br />

110


Chapter 3 – Oxazoline synthesis & removal<br />

A similar transformation had previously been developed by Pridgen using diborane<br />

with non-aromatic substituents, giving amines 196. 138 However, unlike the Meyers<br />

reduction the substituents were simple hydrocarbons, and diborane will react with<br />

unsaturated groups.<br />

Ph<br />

O<br />

R<br />

N<br />

B 2 H 6 , THF<br />

Δ<br />

R<br />

H<br />

N<br />

196<br />

Ph<br />

OH<br />

56-94%<br />

3 examples (aliphatic)<br />

Scheme 3.21 – borane reduction of oxazoline 138<br />

In the same publication, Pridgen reports the catalytic hydrogenolysis of the benzylic<br />

carbon-oxygen bond of oxazoline 197 <strong>to</strong> give secondary amide 198. This method is of<br />

particular interest since both carbon-heteroa<strong>to</strong>m bonds in the diphenyl oxazoline are<br />

benzylic.<br />

O<br />

N<br />

Ph<br />

Pd/C, H 2 (50 psi)<br />

O<br />

N<br />

H<br />

Ph<br />

EtOH/HCl<br />

OMe<br />

OMe<br />

OMe<br />

OMe<br />

197 198<br />

98%<br />

Scheme 3.22 – hydrogenolysis of oxazoline C–O bond 138<br />

3.2.2 General strategy<br />

<strong>The</strong> methods presented above generally involve two synthetic steps in good overall<br />

yield, but only a few permit the recovery of the amino alcohol. <strong>The</strong> most promising<br />

route appears <strong>to</strong> be the one-pot TFA-LiAlH 4 procedure which has been shown <strong>to</strong><br />

proceed in good yield and does not appear <strong>to</strong> affect optical purity. Likewise, acid<br />

hydrolysis permits recovery of the amino alcohol, but has not been employed on many<br />

non-aromatic or chiral substrates. From its extensive use by Meyers, the method most<br />

likely <strong>to</strong> work is the two-pot alkylation-reduction-hydrolysis procedure which unmasks<br />

the oxazoline as an aldehyde, accompanied by the N-methyl amino alcohol.<br />

111


3.2 – Oxazoline removal<br />

However, the diphenyl oxazoline lends itself <strong>to</strong> hydrogenolysis since both C–X bonds<br />

are benzylic, although the literature precedent for this reaction contained only the more<br />

labile C–O benzylic bond. Whilst it would not return the amino alcohol, the main<br />

advantage of this method is that it would involve a single reagent with very well<br />

unders<strong>to</strong>od reactivity with other functional groups.<br />

3.2.2.a Model compounds<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

O<br />

N<br />

101m<br />

O<br />

201<br />

Scheme 3.23 – model oxazolines<br />

Whilst we are interested in cleaving 2-alkyloxazolines all oxazolines studied so far,<br />

and most of those found in the literature, are 2-aryloxazolines. 2-Cyclohexyloxazoline<br />

101m and enone 201 will be used <strong>to</strong> study the removal of the oxazoline moiety. <strong>The</strong><br />

former is a simple system which can be quickly synthesised, whilst the latter contains a<br />

challenging quaternary centre and functionality that will be encountered in a future<br />

synthesis. Enone 201 can readily be synthesised from diene 102b (Table 3.6).<br />

112


Chapter 3 – Oxazoline synthesis & removal<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

O<br />

N<br />

conditions<br />

OMe<br />

102b<br />

O<br />

201<br />

Entry Conditions Time Yield of 201 (SM) / %<br />

a 1M HCl (aq) / CH 2 Cl 2 workup


3.2 – Oxazoline removal<br />

3.2.3 Reduction of oxazolines<br />

3.2.3.a Catalytic hydrogenolysis<br />

O NH 2<br />

Ph Ph<br />

O N<br />

c-Hex<br />

101m<br />

H 2 , Cat.<br />

HO N<br />

c-Hex Ph<br />

202<br />

Ph<br />

H 2 , cat.<br />

±H<br />

O<br />

c-Hex<br />

203<br />

H<br />

N<br />

H 2 , cat.<br />

Ph<br />

c-Hex<br />

Ph<br />

204<br />

Scheme 3.24 – hydrogenolysis of oxazolines<br />

Whilst the hydrogenolysis of an oxazoline containing a benzylic C–O bond is known<br />

(section 3.2.1.c), diphenyl oxazoline 101m also contains the much stronger C–N bond.<br />

It was unclear how labile this aza-allylic bond would be, but amine N-benzyl bonds are<br />

often resistant <strong>to</strong> hydrogenolysis, whilst those of amides such as 204 are no<strong>to</strong>riously<br />

resistant. 117<br />

114


Chapter 3 – Oxazoline synthesis & removal<br />

Ph<br />

O<br />

N<br />

c-Hex<br />

Ph<br />

H 2 / cat.<br />

O<br />

H<br />

N<br />

c-Hex<br />

Ph<br />

Ph<br />

c-Hex<br />

101m 204<br />

205<br />

Entry Catalyst H 2 pressure / T Solvent 204:205*<br />

a Pd/C 50 bar / 50 ºC MeOH 100:0<br />

b Pd/C 50 bar / 50 ºC MeOH:AcOH (9:1) 100:0<br />

c Pd/C 50 bar / 30 ºC EtOAc 100:0<br />

d Ru/Al 2 O 3 50 bar / rt MeOH 100:0<br />

e RaNi 50 bar / rt MeOH 100:0<br />

f Pd(OH) 2 /C 50 bar / 50 ºC MeOH:AcOH (9:1) 98:2<br />

g<br />

H-Cube<br />

Pd(OH) 2 /C 80 bar / 50 ºC AcOH 94:6<br />

h Pd(OH) 2 /C 80 bar / rt AcOH 66:22<br />

i Pd(OH) 2 /C 70 bar / rt EtOAc 85:15<br />

j Pd(OH) 2 /C 80 bar / rt TFA, MeOH/H 2 O 80:20<br />

k<br />

Bomb **<br />

Pd(OH) 2 /C 70 bar / rt TFA, MeOH (pre-stir) 80:20<br />

* Crude 1H NMR ratio ** overnight reactions, c. 14 hr<br />

Table 3.7 – hydrogenation of oxazoline<br />

Unfortunately none of the desired primary amide 203 was formed, only secondary<br />

amides 204 and 205. Aprotic solvent was used in an attempt <strong>to</strong> minimise tau<strong>to</strong>merism<br />

of 202 hoping that the aza-allylic intermediate might hydrogenolyse (entries c, i),<br />

however this is unlikely <strong>to</strong> have worked since the palladium contains up <strong>to</strong> 50% water.<br />

Bound water is also thought <strong>to</strong> be responsible for the formation of hydroxyamide 205<br />

(entries f-k), whose stereochemistry is assigned by comparison with a known sample<br />

(vide infra). TFA was added (entries j, k) in an attempt <strong>to</strong> form the trifluoroacetate salt<br />

of either the oxazoline or ester, again without success.<br />

+<br />

O<br />

H<br />

N<br />

Ph<br />

OH<br />

Ph<br />

115


3.2 – Oxazoline removal<br />

Ph<br />

O<br />

N<br />

Ph<br />

Ph<br />

H<br />

N<br />

O<br />

H 2 , Pd/C<br />

Ph<br />

R<br />

R'<br />

20 bar<br />

Et 3 N<br />

201: R = C=O, R'=H 2 , 96% 206<br />

102b: R = OMe, R'=H, 60% 206<br />

102a: R = R' = H, no isolabe prod<br />

Scheme 3.25 – hydrogenation of unsaturated oxazolines<br />

Similar results were found when dearomatised compounds were hydrogenated<br />

(Scheme 3.25). Enol ether 102b and the related enone 201 both gave ke<strong>to</strong>ester 206,<br />

presumably due <strong>to</strong> the acidity of the palladium catalyst, despite the presence of a mild<br />

base. This acidity might explain the complete degradation of diene 102a, which<br />

proved sensitive <strong>to</strong> most conditions it was treated with (vide infra).<br />

R<br />

R'<br />

<strong>The</strong> outcome of the above reactions is less surprising in light of the outcome of<br />

hydrogenation of oxazoline 207 in the synthesis of (+)-L-733,060, an NK-1 recep<strong>to</strong>r<br />

antagonist (Scheme 3.26). 139 Whilst little comment is made, synthesis of piperidinone<br />

209 from oxazoline 207 appears <strong>to</strong> require hydrogenation of the benzylic C–O bond<br />

indicated, hydrolysis by residual water and finally cyclisation. This would indicate<br />

that the aza-allylic C–N bond is extremely stable. Alternatively, amino alcohol 208<br />

could form by hydrolysis, possibly expedited by hydrogenolysis of a benzylated<br />

intermediate.<br />

MeO<br />

O<br />

Ph<br />

H 2 /Ph(OH) 2<br />

70 psi<br />

OH<br />

Ph<br />

F 3 C<br />

CF 3<br />

MeO<br />

O<br />

O<br />

HO<br />

Ph<br />

207<br />

Ph<br />

N<br />

Ph<br />

NH<br />

MeOH/AcOH<br />

NH<br />

10:1, rt 3 d<br />

O 76%<br />

209<br />

O<br />

MeO<br />

H 3 O +<br />

Ph<br />

H 2 /Pd(OH) 2<br />

HO NH 3<br />

208<br />

139<br />

Scheme 3.26 – hydrogenation of a 2-phenyloxazoline<br />

O<br />

NH<br />

Ph<br />

(+)-L-733,060<br />

116


Chapter 3 – Oxazoline synthesis & removal<br />

Since neither the aza-allylic nor amide N-benzyl bonds were apparently susceptible <strong>to</strong><br />

hydrogenolysis, it was hoped that this bond in the corresponding secondary amine<br />

would be. This could be made by reduction of the amide or by treating oxazolines<br />

directly with DIBAlH (section 3.2.1.c).<br />

3.2.3.b DIBAlH reduction<br />

Ph<br />

O<br />

N<br />

Ph<br />

DIBAlH<br />

solvent,<br />

0 °C<br />

H<br />

N<br />

Ph<br />

OH<br />

Ph<br />

101m 210 205<br />

O<br />

H<br />

N<br />

Ph<br />

OH<br />

Ph<br />

solvent 210/% 205/%<br />

THF (wet) 40 20<br />

THF 60 20<br />

Toluene 80 10<br />

Table 3.8 – DIBAlH reduction of oxazolines<br />

Whilst the procedure 137 did not specify whether wet or dry solvent should be used the<br />

reduction worked well on test substrate 101m using dry THF. <strong>The</strong> structure of amine<br />

210 was confirmed by synthesis from benzaldehyde and amino alcohol 175.<br />

Catalyst bar / ° C solvent<br />

Pd/C 80 / 50<br />

AcOH in MeOH<br />

(10% <strong>to</strong> 100%)<br />

Pd(OH) 2 /C 70 / rt AcOH<br />

H<br />

N<br />

Ph<br />

OH<br />

Ph<br />

H 2<br />

Conditions<br />

nr<br />

Pd(OH) 2 /C 70 / rt TFA/MeOH<br />

210<br />

Table 3.9 – hydrogenolysis of secondary amine 210<br />

<strong>The</strong> benzylic C–N bond of amine 210 was resistant <strong>to</strong> hydrogenolysis under a similar<br />

range of conditions as the parent compound. Whilst hydrogenation was only<br />

conducted under acid conditions, it is not thought this jeopardised the reaction since<br />

similar N-debenzylations have been conducted in TFA-MeOH. 140 Recently Li has<br />

shown that an equimolar mixture of Pd and Pd(OH) 2 catalysts on carbon can be more<br />

active than either individual catalyst, 141 but this, nor transfer hydrogenation are thought<br />

likely <strong>to</strong> prove more productive than the methods already attempted.<br />

117


3.2 – Oxazoline removal<br />

3.2.3.c Amide hydrolysis<br />

Amides 204 and 205 were stable <strong>to</strong> acid and alkaline hydrolysis. Following the<br />

pro<strong>to</strong>col of <strong>Clayden</strong>, 142 the hydrolysis of N-nitroso amides was attempted, but both<br />

nitrosation and hydrolysis proceeded slowly and in poor yield. McClure had<br />

previously hydrolysed secondary amides by conversion <strong>to</strong> the imidate and subsequent<br />

acid hydrolysis, but unfortunately it was found that the imidate could only be formed<br />

from aromatic amides. 143<br />

3.2.4 Oxazoline hydrolysis<br />

Ph Ph<br />

NH 3 Cl<br />

Ph<br />

HCl<br />

O N<br />

Ph O O Ph<br />

Reflux<br />

NH 2<br />

Ph<br />

OH<br />

c-Hex<br />

c-Hex<br />

101m 211.HCl<br />

175<br />

Entry Conditions Time 211 / % 175 / %<br />

a 6N HCl:THF, 3:1 2 min 91 0<br />

b 3N HCl:THF, 2:1 2 min 85 0<br />

c 6N HCl:EtOH, 3:1 1 hr 50 40<br />

d 6N HCl:EtOH, 3:1 16 hr 0 70<br />

Table 3.10 – hydrolysis of 2-cyclohexyloxazoline<br />

Hydrolysis of cyclohexane 101m was found <strong>to</strong> proceed in a similar manner <strong>to</strong> that<br />

described by Meyers (section 3.2.1.a). Gentle heating quickly gave ester 211.HCl as<br />

the crystalline ammonium salt which could be isolated by simple filtration. Continued<br />

heating allowed amine 175 <strong>to</strong> be recovered after aqueous work up, although<br />

cyclohexanecarboxylic acid was not isolated. In light of this possible isolation<br />

problem methods for reducing the ester were studied (Scheme 3.27).<br />

118


Chapter 3 – Oxazoline synthesis & removal<br />

Ph<br />

NH 3 Cl<br />

Ph<br />

O<br />

211.HCl<br />

c-Hex<br />

O<br />

Pd/C, H 2<br />

1 atm, 1 hr<br />

LiBH 4 ,<br />

THF, 0 °C<br />

O<br />

c-Hex<br />

O<br />

OH<br />

H<br />

N<br />

HO<br />

c-Hex Ph<br />

205<br />

H 2 N<br />

Ph<br />

quant<br />

Ph<br />

212<br />

Ph<br />

50%<br />

Scheme 3.27 – reduction of ester 211<br />

Cyclohexanecarboxylic acid was easily recovered from the hydrogenation, which did<br />

not require workup, whilst reduction with ethereal lithium borohydride returned mostly<br />

amide 205, rather than the desired alcohol. Disappointingly precipitation could not be<br />

induced with arene 101b, and amide 211, the thermodynamic product, was isolated in<br />

near quantitative yield (Scheme 3.28).<br />

Ph<br />

O<br />

N<br />

Ar<br />

101b<br />

Ph<br />

HCl (aq), EtOH<br />

Δ 12 hr<br />

O<br />

Ar<br />

H<br />

N<br />

211<br />

Ph<br />

OH<br />

Ph<br />

96%<br />

Scheme 3.28 – hydrolysis of aryl oxazolines<br />

Ar =<br />

MeO<br />

Hydrolysis of diol 213 and enone 201 both precipitated the ester as the major product,<br />

although enone 201 gave equal amounts of the ester and an unidentified oil. <strong>The</strong> IR<br />

spectrum of this oil contained only one strong absorption at 1672 cm -1 , likely <strong>to</strong> be the<br />

enone, and NMR analysis showed no significant aromatic or isopropyl peaks. Whilst<br />

attempting the epoxide opening of 216, ester 217 was isolated in good yield, but was<br />

not reacted further (Scheme 3.29).<br />

119


3.2 – Oxazoline removal<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

O OR O N<br />

O OR<br />

OH<br />

213<br />

OH<br />

HCl (aq), THF<br />

Δ, 12 hr<br />

OH<br />

214<br />

OH<br />

80%<br />

6N HCl:THF 2:1<br />

Δ, < 18hr<br />

O<br />

O<br />

201 215<br />

45%<br />

R =<br />

Ph<br />

NH 3 Cl<br />

O<br />

Ph<br />

Ph<br />

O<br />

N<br />

Ph<br />

HClO 4 (aq), dioxane<br />

O<br />

OR<br />

O<br />

rt, 28 hr<br />

O<br />

OH<br />

OH<br />

OH<br />

216 217<br />

OH<br />

40% (55% conv)<br />

Scheme 3.29 – hydrolysis of oxazolines <strong>to</strong> esters<br />

Since the amide would be expected <strong>to</strong> be the thermodynamic product of these<br />

reactions, and it was isolated in the absence of a precipitate, it is believed that the<br />

precipitate serves <strong>to</strong> move the hydrolysis equilibrium in favour of the ester. In light of<br />

this, other ammonium salts were tried; exposure and gentle heading of cyclohexane<br />

101m with solutions of HBF 4 , HCl/Et 2 O, H 2 SO 4 and TsOH did not promote any<br />

visible precipitation.<br />

<strong>The</strong> alkylation-hydrolysis of enone 201 was attempted in a similar fashion <strong>to</strong> Meyers<br />

(section 3.2.1.a). <strong>The</strong> resulting ester is closely related <strong>to</strong> the ammonium salt 211, and<br />

was isolated in slightly improved yield with some starting material recovered.<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

MeOTf, 16 hr<br />

then NH 4 Cl (aq)<br />

24 hr, rt<br />

MeHN<br />

Ph<br />

O<br />

O<br />

O<br />

201<br />

O<br />

218<br />

60%<br />

(90% conv.)<br />

Scheme 3.30 – alkylation-hydrolysis of oxazoline 201<br />

120


Chapter 3 – Oxazoline synthesis & removal<br />

3.2.5 Quaternisation-reduction<br />

3.2.5.a Trifluoroacetate salt<br />

Ph Ph<br />

O N<br />

c-Hex<br />

101m<br />

OH<br />

NH 3 TFA LiAlH 4<br />

c-Hex<br />

TFA, THF O O<br />

Ph<br />

then H 2 O, Na 2 SO 4<br />

c-Hex Ph<br />

H<br />

O OH<br />

3 O +<br />

211.TFA<br />

or H 2 /Pd<br />

c-Hex<br />

Scheme 3.31 – possible manipulations of ester-TFA salt<br />

This method seemed particularly appealing, since it had been used a number of times<br />

by Meyers, and hydrolysis of ester 211.TFA would allow recovery the amino alcohol<br />

<strong>to</strong> be recycled. Cabedo had applied this method <strong>to</strong> diene 102a, however the reaction<br />

proved unreliable and yields were inconsistent, although in retrospect this may be<br />

attributed <strong>to</strong> the observed acid sensitivity of alcohol 220. <strong>The</strong> poor yield of Mosher<br />

ester 221 means that the modest diastereomeric ratio could reflect kinetic resolution of<br />

the alcohol as much as any loss in optical purity during the dearomatisation and<br />

cleavage.<br />

Ph<br />

O<br />

N<br />

Ph<br />

i) TFA,<br />

H 2 O, THF<br />

ii) LiAlH 4<br />

HO<br />

102a 220<br />

F 3 C<br />

(R)-MTPA-Cl Ph<br />

MeO O<br />

Pyr./DMAP<br />

30-50%<br />

CH 2 Cl 2<br />

221<br />

Scheme 3.32 – reduction of diene 102a by Cabedo 64<br />

O<br />

Me<br />

62%<br />

d.r. 95:5<br />

Unfortunately, numerous attempts <strong>to</strong> reproduce the oxazoline cleavage with model<br />

oxazoline 101m failed; the only identifiable material by crude NMR being amide 205.<br />

This method was not applied <strong>to</strong> any other compounds since it was anticipated that TFA<br />

would not be compatible with the intended syntheses.<br />

Ph<br />

O<br />

N<br />

c-Hex<br />

101m<br />

Ph<br />

TFA, THF<br />

H 2 O, Na 2 SO 4<br />

O<br />

H<br />

N<br />

c-Hex Ph<br />

205<br />

OH<br />

Ph<br />

60%<br />

(90% conv.)<br />

Scheme 3.33 – TFA hydrolysis of 2-cyclohexyloxazoline<br />

121


3.2 – Oxazoline removal<br />

3.2.5.b N-Alkylation<br />

Meyers’ preferred method of oxazoline removal was alkylation-reduction followed by<br />

hydrolysis of the oxazolidine <strong>to</strong> reveal the aldehyde (section 3.2.1.b). Early attempts<br />

<strong>to</strong> reproduce this on two model compounds failed work after repeated attempts.<br />

Ph Ph<br />

O<br />

N<br />

i) MeOTf, 10 hr<br />

then NaBH 4<br />

ii) (CO 2 H) 2 , rt, 36 hr<br />

THF/H 2 O<br />

poor mass recovery,<br />

no isolable product<br />

102a<br />

Ph Ph<br />

O N<br />

c-Hex<br />

101m<br />

i) MeOTf, 5 hr<br />

then NaBH 4<br />

ii) (CO 2 H) 2 , rt, 16 hr<br />

THF/H 2 O<br />

poor mass recovery,<br />

no isolable product<br />

Scheme 3.34 – failed alkylation-reduction-hydrolysis reactions<br />

However, enone 201 underwent a smooth alkylation-reduction sequence <strong>to</strong> give<br />

oxazolidine 222 as a single observable diastereomer isolated by flash column<br />

chroma<strong>to</strong>graphy. <strong>The</strong> relative stereochemistry of 222 was established by forward<br />

reaction (section 4.4.2).<br />

Ph Ph<br />

Ph Ph<br />

O<br />

N<br />

O<br />

N<br />

O<br />

H<br />

MeOTf, 16 hr<br />

Conditions, rt<br />

then NaBH 4<br />

O<br />

201<br />

OH<br />

222<br />

70%<br />

>95:5 d.r<br />

OH<br />

223<br />

>95:5 d.r<br />

Entry Conditions Time conversion / %<br />

a THF/H 2 O, (CO 2 H) 2 40 hr 70<br />

b THF/H 2 O, (CO 2 H) 2 3 d 100<br />

c SiO 2 , CH 2 Cl 2 10 d 50<br />

d THF/pH 9 buffer 24 hr 0<br />

Table 3.11 – hydrolysis of 2-cyclohexyloxazoline<br />

122


Chapter 3 – Oxazoline synthesis & removal<br />

Hydrolysis of oxazolidine 222 was considerably slower than Meyers’ oxazolines,<br />

which are reported hydrolyse in 15 <strong>to</strong> 20 hours. Comparative hydrolysis of recovered<br />

oxazolidine and a crude mixture confirmed that the slow reaction rate was not due <strong>to</strong><br />

thermodynamic resolution of the possible diastereomers. Treatment of enol ether 102b<br />

proceeded in a similar manner, although significant amounts of hydrolysis was<br />

observed during the alkylation, and the ratio was the same whether bench or dry<br />

methanol were used. Interestingly the hydrolysis of the mixed oxazolidines <strong>to</strong>ok<br />

considerably longer than of 222 alone (vide infra).<br />

Ph<br />

O<br />

N<br />

Ph<br />

MeOTf<br />

15 hr<br />

then NaBH 4<br />

Ph<br />

O<br />

Ph<br />

NMe<br />

+<br />

Ph<br />

O<br />

Ph<br />

NMe<br />

i) (CO 2 H) 2 , rt 10 d<br />

THF/H 2 O<br />

ii) NaBH 4 , MeOH<br />

HO<br />

OMe<br />

102b<br />

O<br />

224<br />

OH<br />

222<br />

OH<br />

225<br />

55%<br />

Crude ratio<br />

224 : 222<br />

3 : 2<br />

Scheme 3.35 – alkylation-hydrolysis of enol ether 102b<br />

Alkylation of the oxazoline is reported by Meyers <strong>to</strong> proceed within 1-4 hours by TLC<br />

analysis, however in these studies complete conversion of starting material <strong>to</strong> baseline<br />

salts was never observed and reaction times are often longer than necessary. Later<br />

experiments indicate that alkylation was complete within 2-3 hours. Whilst the<br />

neopentyl aldehydes were stable <strong>to</strong> chroma<strong>to</strong>graphy and for weeks under atmospheric<br />

conditions, they were unstable <strong>to</strong> purification by acid resin (SCX) with rapid<br />

decomposition observed. <strong>The</strong> oxazolidines were largely stable <strong>to</strong> chroma<strong>to</strong>graphy,<br />

although it was observed that purification of this intermediate reduced the overall yield<br />

of auxiliary removal.<br />

During the synthesis of carbasugars (section 4.2.7), oxazolidine 226 was also found <strong>to</strong><br />

hydrolyse very slowly (Table 3.12).<br />

123


3.2 – Oxazoline removal<br />

Ph<br />

Ph<br />

O<br />

N<br />

H<br />

O<br />

BnO<br />

Conditions<br />

BnO<br />

BnO<br />

OBn<br />

OBn<br />

BnO<br />

OBn<br />

OBn<br />

226<br />

Time / d<br />

(<strong>to</strong>tal d)<br />

[Oxalic Acid] [Substrate] Temperature<br />

Remaining<br />

oxazolidine* / %<br />

6 (6) 0.5 0.05 rt 88<br />

2 (8) 0.0001 0.05 rt 87<br />

3 (11) 0.5 0.1 rt 80<br />

2 (13) 0.5 0.1 50 °C 67<br />

* calculated from ratio of SM:aldehyde signal in 1 H NMR<br />

Table 3.12 – acid-catalysed hydrolysis of the oxazolidine<br />

Bundgaard and co-workers have conducted comprehensive studies of the hydrolysis of<br />

oxazolidines, finding that whilst hydrolysis occurs in the pH range 2-9, it is fastest<br />

under neutral or slightly alkaline conditions, and also shows a strong dependence on<br />

buffer concentration. 144,145 Buffer solutions of acetate (pH 8) and borate (pH 9), as<br />

well as a silica/THF/water slurry were used with no observable improvement, similar<br />

results were found in the hydrolysis of 222 (Table 3.11). Addition of chloral as a<br />

‘sacrificial’ aldehyde <strong>to</strong> the original acid conditions gave no rate enhancement.<br />

As expected, study of reaction progress at elevated temperatures (Table 3.13) shows a<br />

significant increase in the rate of hydrolysis, reaching an acceptable speed at around 60<br />

°C, with a half life estimated as 2 days. <strong>The</strong> reaction was repeated at this temperature<br />

and deemed complete within 7 days in 85% yield, with no significant decomposition of<br />

the aldehyde noted (Table 3.13).<br />

124


Chapter 3 – Oxazoline synthesis & removal<br />

Ph<br />

Ph<br />

BnO<br />

O<br />

N<br />

(CO 2 H) 2 ,<br />

THF/water 4:1<br />

BnO<br />

H<br />

O<br />

BnO<br />

T / Days of rxn<br />

°C (<strong>to</strong>tal)<br />

OBn<br />

OBn<br />

226<br />

Remaining<br />

226 * /%<br />

40 7 (7) 82<br />

50 10 (17) 39<br />

60 4.5 (21) 10<br />

60 7 (28.5) 0<br />

* ratio SM:aldehyde in 1 H NMR<br />

T °C<br />

100<br />

80<br />

60<br />

40<br />

20<br />

0<br />

%<br />

BnO<br />

OBn<br />

OBn<br />

40 °C 50 °C 60 °C<br />

0 5 10 15 20 25<br />

Total days of reaction<br />

Table 3.13 – effect of temperature on hydrolysis of oxazolidine<br />

Two significant discrepancies have arisen; firstly, that oxazolidine 222 hydrolysed<br />

significantly faster (3 d) than oxazolidines 224 and 226 (>10 d), and secondly that all<br />

three hydrolyse considerably slower than the reports of either Meyers (c. 20 hr) or<br />

Bundgaard (c. 12 hr 146 ). <strong>The</strong> solution <strong>to</strong> the first quandary was found during the<br />

synthesis of carbasugars (section 4.2.9). Neighbouring group participation by the cishydroxyl<br />

group catalyses the reaction through intramolecular attack of Schiff base<br />

228 147 <strong>to</strong> form cyclic ether 229, which quickly hydrolyses <strong>to</strong> diol 225.<br />

Ph Ph<br />

Ph<br />

HO<br />

OH<br />

HO<br />

O N<br />

Ph<br />

N Ph Ph<br />

N i-Pr<br />

O<br />

OH<br />

222<br />

pK a ≈ 6.0 144<br />

OH<br />

228<br />

229<br />

OH<br />

225<br />

Scheme 3.36 – neighbouring group participation in the hydrolysis of oxazolidines<br />

<strong>The</strong> second situation is not as clear. Bundgaard studied both the role of the carbonyl 144<br />

(Scheme 3.37) and amino alcohol 145 portion of the oxazolidine and identified some<br />

clear trends in the rate of hydrolysis.<br />

125


3.2 – Oxazoline removal<br />

Ph<br />

Me<br />

Ph<br />

Me<br />

Ph<br />

Me<br />

O<br />

N<br />

O<br />

N<br />

O<br />

N<br />

230<br />

t ½ (pH 7.4)<br />

0.08<br />

0.3<br />

30<br />

min<br />

t ½ (pH 1.0)<br />

96<br />

70<br />

-<br />

min<br />

144<br />

Scheme 3.37 – half-lives of some oxazolidines at 37 °C<br />

This work clearly shows that a β-quaternary centre on the aldehyde clearly retards<br />

hydrolysis, but the half lives reported are still shorter than those observed for alcohol<br />

222 let alone benzyl ether 226. When looking at the role of amino alcohol substitution,<br />

Bundgaard also found that substitution α <strong>to</strong> nitrogen led <strong>to</strong> significant retardation, with<br />

geminal methyl groups causing a 50 times increase in half life than a simple<br />

methylene. However, whilst they did not compare a phenyl group with a methyl<br />

group, it is unlikely <strong>to</strong> be responsible for such a difference. In addition, recent<br />

calculations by Walker based upon this research shows that cis substituted<br />

oxazolidines hydrolyse more rapidly than their trans epimer, but do not quantify<br />

this. 148<br />

Whilst these combined effects might explain why the diphenyl oxazolidine with an<br />

adjacent quaternary centre hydrolyses much more slowly than many apparently similar<br />

oxazolidines, it does not explain the difference with the similarly substituted Meyers<br />

oxazolidine. Furthermore, the reaction does not seem <strong>to</strong> share the same pH<br />

dependence as Bungaard reported, meaning that it is possible that a change in<br />

mechanism has occurred. Two pathways for hydrolysis are considered (Scheme 3.38).<br />

126


Chapter 3 – Oxazoline synthesis & removal<br />

Ph<br />

O<br />

Ph<br />

NH<br />

Ph<br />

Ph<br />

O<br />

N<br />

H<br />

+H 2 O<br />

Ph<br />

Ph<br />

HO<br />

N<br />

H<br />

OH<br />

- H +<br />

Ph<br />

Ph<br />

NH<br />

OH<br />

O<br />

+ H + - H+<br />

pKa 6 144<br />

231<br />

pKa −2<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

Ph<br />

O<br />

N<br />

H 2<br />

OH<br />

230<br />

232<br />

pKa 10<br />

+ H +<br />

Ph<br />

HO<br />

pKa −2<br />

N<br />

Ph<br />

HO<br />

Ph<br />

N<br />

Ph<br />

+ H 2 O<br />

HO<br />

HO<br />

Ph<br />

NH<br />

Ph<br />

- H +<br />

Ph<br />

Ph<br />

NH<br />

OH<br />

O<br />

233<br />

Scheme 3.38 – hydrolysis of oxazolidine, pKa values are approximate in water<br />

<strong>The</strong> research of Bundgaard and Fife both identify the appearance and disappearance of<br />

iminium ion 233 during hydrolysis. This is initially surprising since this intermediate<br />

must come from pro<strong>to</strong>nation of an ether in the presence of an amine. However, this<br />

occurs on both hydrolytic pathways, and formation of iminium ion 233 is considerably<br />

more favourable than oxonium 231. <strong>The</strong>se equilibria seem <strong>to</strong> favour the use of acid<br />

conditions, and it remains unclear why hydrolysis should be favoured under neutral<br />

conditions in the studies of Bundgaard.<br />

127


3.2 – Oxazoline removal<br />

3.2.6 Determination of optical purity<br />

Ph<br />

Ph<br />

O<br />

N<br />

i) MeOTf, 18 hr<br />

then NaBH 4<br />

HO<br />

p-BrBzCl<br />

DMAP<br />

O-pBrBz<br />

O<br />

201<br />

ii) Oxalic acid, 3 d rt<br />

iii) NaBH 4<br />

OH<br />

225<br />

94%<br />

> 95:5 dr<br />

Et 3 N, CH 2 Cl 2<br />

O-pBrBz<br />

62%<br />

115<br />

> 99:1 e.r.<br />

Scheme 3.39 – determination of optical purity<br />

<strong>The</strong> alkylation-reduction-hydrolysis method was applied <strong>to</strong> enone 201 and the<br />

resulting diol benzoylated <strong>to</strong> allow HPLC analysis, showing bisbenzoate 115 <strong>to</strong> be<br />

essentially optically pure. <strong>The</strong> para-bromobenzoate was chosen since it x-ray<br />

crystallography would allow confirmation of the absolute stereochemistry, however<br />

bisbenzoate 115 could not be crystallised.<br />

128


Chapter 3 – Oxazoline synthesis & removal<br />

3.3 Summary and Future work<br />

Although far from complete, the work presented has permitted the study of<br />

dearomatising additions and the removal of the source chirality <strong>to</strong> a synthetically<br />

useful functional group without the loss of optical purity. <strong>The</strong> synthesis of optically<br />

pure oxazoline has been achieved by three methods, whilst a number of promising<br />

results have bee obtained <strong>to</strong>wards its removal.<br />

3.3.1 Moving closer <strong>to</strong> an auxiliary<br />

3.3.1.a Oxazoline synthesis<br />

Optically pure amino alcohol is readily available as either enantiomer from transstilbene<br />

(Scheme 3.10) or commercial sources. 149 Subsequent amide coupling<br />

followed by cyclisation returns the optically pure oxazoline in 40-70% (Table 3.2).<br />

Alternatively, racemic oxazolines can be synthesised in three steps from the benzamide<br />

and cis-stilbene in 72% overall yield (Table 3.5).<br />

3.3.1.b Oxazoline removal<br />

<strong>The</strong> current best method for oxazoline removal is the alkylation-reduction-hydrolysis<br />

procedure of Meyers which has returned up <strong>to</strong> 94% of the aldehyde. Even though it<br />

failed on two substrates, is has been shown <strong>to</strong> work for a number of oxazolines and<br />

more examples are presented in the following syntheses. <strong>The</strong> weakness of this method<br />

is the slow oxazolidine hydrolysis, and although literature examples suggest that a<br />

more rapid hydrolysis should be achievable, initial studies have failed <strong>to</strong> find any.<br />

Presently the best compromise has been <strong>to</strong> increase the temperature of the reaction<br />

since the resulting neopentylic aldehydes have proved quite stable. Fortunately, in the<br />

majority of cases unprotected alcohols have been available <strong>to</strong> aid oxazolidine<br />

hydrolysis.<br />

In its current form, this method of removal is inadequate since it either requires a week<br />

long reaction <strong>to</strong> a stable aldehyde, or places significant constraint on synthetic<br />

planning. One immediate solution might be the hydrolysis of the N-methylated<br />

oxazoline <strong>to</strong> the ester or acid, rather than reduction <strong>to</strong> the recalcitrant oxazolidine.<br />

129


Better, however, would be a method involving a reversible association with the<br />

oxazoline allowing the amino alcohol <strong>to</strong> be recovered.<br />

3.3.1.c Recycling the amino alcohol<br />

Whilst attempts <strong>to</strong> promote hydrolysis via the oxazoline trifluorosulfonate salt failed, it<br />

is important <strong>to</strong> note that the two oxazolines treated also did not respond <strong>to</strong> the methyl<br />

triflate conditions. Since this method would allow the recovery of the amino alcohol,<br />

and would be orthogonal <strong>to</strong> the current best method, it seems worthy of further<br />

experimentation.<br />

<strong>The</strong> examples of aqueous acid hydrolysis of oxazolines gave the ester in moderate <strong>to</strong><br />

good yield when successful, and it seems likely that extended acid hydrolysis would<br />

give the free acid. However this may not be generally applicable method, since<br />

precipitation of the ammonium salt seems <strong>to</strong> be key, possibly explaining why Meyers<br />

did not use it with any of his dearomatising additions.<br />

In the next chapter (section 4.5.1) some promising studies of the Lewis acid catalysed<br />

hydrolysis of oxazolines are presented. Whilst this work only studied removal by<br />

lac<strong>to</strong>nisation, it is possible that this might be a more general method than Brønsted<br />

acid hydrolysis.<br />

130


Chapter 4 – Synthesis of carbasugars<br />

Chapter 4 – <strong>The</strong> Synthesis of <strong>Carbasugar</strong>s<br />

4.1 <strong>Carbasugar</strong>s<br />

4.1.1 What they are and what they do<br />

<strong>Carbasugar</strong>s are sugar analogues in which the endocyclic oxygen is replaced with a<br />

carbon a<strong>to</strong>m, normally a methylene group. Saccharides, in the form of cellulose, are<br />

the most abundant organic compounds on the planet and are responsible for not only<br />

structure and energy s<strong>to</strong>rage, but also cell-cell recognition, blood clotting and<br />

intracellular signalling. As such, they play a significant biological role, and can<br />

feature in diseases such as cancer, inflammation and diabetes.<br />

HO<br />

OH<br />

HO<br />

OH<br />

HO<br />

OH<br />

OH<br />

250a<br />

5a-carba-α-DL-talopyranose<br />

HO<br />

OH<br />

OH<br />

250b<br />

5a-carba-α-DL-galac<strong>to</strong>pyranose<br />

Scheme 4.1 – the first carbasugars, synthesised by McCasland<br />

Carbohydrates and their mimics have been studied for a number of years; the first<br />

carbasugars (±250a, b) were synthesised by McCasland in 1966 150 and 1968 151<br />

respectively. McCasland postulated that the resemblance of carbasugars <strong>to</strong> the natural<br />

compounds might afford similar biological recognition, whilst the absence of the labile<br />

anomeric bonds would render them more stable. Indeed, studies have shown that<br />

humans cannot distinguish the taste of D-glucose from racemic carba-β-DLglucopyranose;<br />

furthermore carba-α-DL-glucopyranose is an effective inhibi<strong>to</strong>r of<br />

glucokinase in pancreatic islets, seemingly by competitive inhibition. 152 Seven years<br />

after McCasland’s first synthesis, naturally occurring carbagala<strong>to</strong>pyranose +250b was<br />

discovered in the fermentation broth of an actinomycete bacteria. 153 McCasland had<br />

chosen <strong>to</strong> synthesise carbagala<strong>to</strong>pyranose by chance as it was accessible by<br />

epimerisation of 250a, providing a rare example of synthesis preceding discovery. No<br />

naturally occuring carbasugars have been found since.<br />

131


4.1 – Introduction<br />

HO<br />

OH<br />

OH<br />

HO<br />

OH<br />

OH<br />

O<br />

Cyclophelli<strong>to</strong>l<br />

OH<br />

OH<br />

O<br />

251<br />

1,6-epi-Cyclophelli<strong>to</strong>l<br />

Scheme 4.2 – some natural cycli<strong>to</strong>ls<br />

<strong>The</strong>re are very few natural cycli<strong>to</strong>ls with the carbapyranose motif; cyclophelli<strong>to</strong>l<br />

(Scheme 4.2) has structural similarities <strong>to</strong> carbasugars and was isolated in 1990 from<br />

the culture filtration of the mushroom Phellinus sp. 154 It is considered <strong>to</strong> be an<br />

analogue of β-D-glucose since the epoxide is on the β-face, and has a much more<br />

potent biological profile that the simple carbasugars; it strongly inhibits β-<br />

glucosidases, and is a potential inhibi<strong>to</strong>r of HIV. Interestingly, the unnatural<br />

diastereomer 251 with the epoxide on the α-face is an α-glucosidase inhibi<strong>to</strong>r, which<br />

are important in the treatment of type II diabetes.<br />

OH<br />

HO<br />

HO<br />

HO<br />

HO<br />

HO<br />

OH<br />

NH 2<br />

HO<br />

HN HO<br />

O<br />

OH<br />

O HO<br />

OH<br />

O<br />

OH<br />

OH<br />

O HO<br />

OH OH<br />

O<br />

Valienamine Acarbose<br />

Scheme 4.3 – some natural aminocarbasugars<br />

Aminocarbasugars such as valienamine are more abundant in nature and are found <strong>to</strong><br />

exhibit greater biological activity. This is assumed <strong>to</strong> be due <strong>to</strong> the basicity of the<br />

amine, and valienamine is a common motif in many biologically active<br />

carbaoligosaccharides such as acarbose, and has been the <strong>to</strong>pic of a recent review. 155<br />

Due <strong>to</strong> its similarity <strong>to</strong> α-glucose, many of valienamine’s derivatives are potent α-<br />

glucosidase inhibi<strong>to</strong>rs, believed <strong>to</strong> be so effective because of a resemblance <strong>to</strong> the<br />

glucopyranosyl cation intermediate in the hydrolysis of α-glucosides. Acarbose was<br />

approved in 1995 as an α-glucosidase inhibi<strong>to</strong>r for use in the treatment of type II<br />

diabetes.<br />

132


Chapter 4 – Synthesis of carbasugars<br />

Superficially, the substitution of an endocyclic oxygen with a methylene should make<br />

little difference <strong>to</strong> the structure; the conformations of cyclohexane and oxane are<br />

similar despite the C–O bonds being almost 10% shorter. However, sugar chemistry is<br />

dominated by the anomeric n O →σ* C–O interactions, which afford significant<br />

stabilisation of the α-anomer in which the glycosidic bond is axial. <strong>The</strong> absence of this<br />

interaction in carbasugars means they can adopt conformations that the parent<br />

carbasugar cannot.<br />

4.1.2 Existing syntheses<br />

All 16 racemic carbasugars, and 25 of the possible 32 carbasugar stereoisomers have<br />

been synthesised, as well as a number of analogues. 156 Many approaches have been<br />

taken, the major difference being whether starting from chiral pool materials –<br />

normally a carbohydrate – or from simpler molecules; both methods have been<br />

recently recent reviewed by Gomez and Lopez. 156 This section will discuss syntheses<br />

of his<strong>to</strong>rical interest, and also some of general synthetic note and relevance <strong>to</strong> the use<br />

of compounds made in previous chapters.<br />

4.1.2.a Chiral pool methods<br />

Often the first decision <strong>to</strong> be made when planning an asymmetric synthesis is where<br />

the source of chirality is <strong>to</strong> come from. When making analogues of sugars,<br />

carbohydrates themselves are the most widely used starting point since they are fully<br />

oxygenated, optically pure and readily available. <strong>The</strong>re are, however two challenges<br />

involved in the conversion of sugars <strong>to</strong> carbasugars; the elongation of the carbon chain,<br />

and the cyclisation of the homologue. Quinic acid (Scheme 4.4) is probably the most<br />

widely used chiral pool material after monosaccharides, although the products often<br />

contain the quaternary centre of the starting material. A great number of quinic acid<br />

derivatives have been made, and have been used as starting materials themselves.<br />

HO<br />

CO 2 H<br />

CO 2 H<br />

HO<br />

OH<br />

OH<br />

HO<br />

OMe<br />

OH<br />

HO<br />

OH<br />

OH<br />

HO<br />

OH<br />

OH<br />

HO<br />

OH<br />

OH<br />

HO<br />

OH<br />

OH<br />

(−)-Quinic acid (−)-Shikimic acid<br />

myo-Inosi<strong>to</strong>l<br />

L-Quebrachi<strong>to</strong>l<br />

Scheme 4.4 – chiral pool starting materials used in carbasugar synthesis<br />

133


4.1 – Introduction<br />

(–)-Shikimic acid is a very appealing starting material, however with its use in the<br />

commercial synthesis of Tamiflu (oseltamivir phosphate) it is in high demand,<br />

exasperating the paucity of supply and making it unaffordable for most synthetic<br />

purposes. However this might slowly be relieved since a number of microbial<br />

biosynthesis of (–)-shikimic acid have from E. coli mutants been published, most<br />

recently by Johansson using mutants derived from the successful W3110 strain, under<br />

phosphate-limited conditions. 157 Indeed in 2005 Roche confirmed that they already get<br />

a third of the shikimic acid they use for synthesis of Tamiflu from fermentation. 158<br />

Inosi<strong>to</strong>ls seem <strong>to</strong> be well suited <strong>to</strong> the synthesis of cycli<strong>to</strong>ls, however seven of the nine<br />

known inosi<strong>to</strong>ls contain a mirror plane, including the most abundant myo-inosi<strong>to</strong>l<br />

(Scheme 4.4). L-Quebrachi<strong>to</strong>l is a chiral inosi<strong>to</strong>l which is reported <strong>to</strong> have been used<br />

in carbasugars synthesis, but at 2000 times the cost of myo-inosi<strong>to</strong>l, 159 is far <strong>to</strong>o<br />

expensive for common usage. Furthermore, the fully saturated system does not<br />

provide a clear synthetic handle as, shikimic acid does.<br />

4.1.2.b Non-chiral pool methods<br />

McCasland’s approach <strong>to</strong> the first synthesis of a carbasugar proceeded through an<br />

oxanorbornene (252); an approach that has been adopted in many subsequent<br />

syntheses. McCasland synthesised ke<strong>to</strong>ne 254 (Scheme 4.5) by the forcing hydrolysis<br />

of bicycle 253, causing ester migration, decarboxylation, and ether hydrolysis in a<br />

single reaction. 150 Reduction, esterification and further reduction yielded the racemic<br />

carba-talopyranose 250a. Peracylation of 250a followed by reflux in strong acid led <strong>to</strong><br />

partial epimerisation, giving peracylated carbagala<strong>to</strong>pyranose (250b) in 14% yield. 151<br />

O<br />

OAc<br />

O<br />

O<br />

O<br />

Δ<br />

O<br />

O<br />

O<br />

i) H 3 O + HO<br />

HO<br />

O<br />

ii) OsO 4<br />

AcO O<br />

AcO<br />

252 253<br />

O<br />

OH<br />

OH<br />

O<br />

H 3 O +<br />

Δ<br />

HO 2 C<br />

MeO 2 C<br />

HO<br />

HO<br />

HO<br />

254<br />

O<br />

OAc<br />

i) NaBH 4<br />

ii) MeOH, TFA<br />

iii) Ac 2 O<br />

AcO<br />

AcO<br />

OAc<br />

OAc<br />

i) LiAlH 4<br />

ii) H 3 O +<br />

HO<br />

OH<br />

HO OH<br />

250a<br />

Scheme 4.5 – McCasland’s synthesis of α-DL-talose analogue 150<br />

134


Chapter 4 – Synthesis of carbasugars<br />

Norbornenes have featured as key intermediates in the synthesis of many carbasugars<br />

in the labora<strong>to</strong>ries of Ogawa; an early example of which is shown in the divergent<br />

synthesis of carbasugars 250b, 257, and 260. 160 Norbornene 255 was made by<br />

cycloaddition, oxidation of which gave lac<strong>to</strong>ne 256 and subsequent reduction,<br />

acylation and hydrolysis gave an equimolar mixture of diastereomers 257 and 250b.<br />

O<br />

a<br />

O<br />

b<br />

HO<br />

O<br />

O<br />

256<br />

O<br />

c<br />

HO<br />

HO<br />

HO<br />

257<br />

OH<br />

OH<br />

+<br />

HO<br />

HO<br />

OH<br />

HO OH<br />

250b<br />

HO 2 C<br />

CO 2 H<br />

255<br />

d<br />

Br<br />

O<br />

O<br />

O<br />

e<br />

AcO<br />

AcO<br />

AcO<br />

Br<br />

OAc<br />

f<br />

HO<br />

HO<br />

HO<br />

OH<br />

OH<br />

258<br />

259<br />

d.r. 12:5 260 d.r. 3:1<br />

Major diastereomers drawn. a) hydroquinone, Δ, 45%; b) H 2 O 2 , formic acid, 45%; c) i)<br />

LiAlH 4 , ii) Ac 2 O, pyr., DMAP, iii) Ac 2 O, AcOH H 2 SO 4 , iv) NaOMe, MeOH: 257 (18%), 250b<br />

(19%). d) HOBr, 91%; e) i) LiAlH 4 , ii) AcOH, Ac 2 O, H 2 SO 4 , 46%; f) i) NaOAc, ii) NaOMe,<br />

MeOH, 41%.<br />

160<br />

Scheme 4.6 – Ogawa’s divergent syntheses of carbasugars<br />

Alternatively, treatment of 255 with hydrobromous acid gave bromolac<strong>to</strong>ne 258,<br />

which upon reduction and hydrolysis yielded a similar mixture of diastereomers of<br />

bromosugar 259. Ace<strong>to</strong>lysis of the major diastereomer gave a 3:1 mixture of 260 and<br />

250b, whilst ace<strong>to</strong>lysis of the minor diastereomer of 259 yielded further carbasugars.<br />

Using similar methods, Ogawa and colleagues have synthesised many carbasugars and<br />

aminocarbasugar analogues, often simultaneously.<br />

A number of methods offering higher degrees of stereocontrol have come from<br />

unsaturated carbocyclic starting material; the traditional way <strong>to</strong> access such materials<br />

is by the dissolving metal reduction of benzene derivatives (section 1.2). Landais and<br />

co-workers developed a selective reduction of benzylsilanes <strong>to</strong> give the meso diene<br />

261 (Scheme 4.7) which was desymmetrised using the Sharpless AD conditions with<br />

good diastereo- and enantioselectivity. Benzylation and a highly selective<br />

cyclopropanation gave bicycle 262, ready for fragmentation. Electrophile-driven<br />

fragmentation of the cyclopropane gave the homoallylic iodide, which was lithiated <strong>to</strong><br />

give the Fleming silane 263. Highly anti-selective dihydroxylation of the allylic ether<br />

135


4.1 – Introduction<br />

followed by Fleming-Tamao oxidation gave the β-L-altrose analogue 264 in 16% from<br />

261.<br />

SiMe 2 t-Bu<br />

i) AD mix α<br />

ii) NaH, BnBr<br />

SiMe 2 t-Bu<br />

OBn<br />

OBn<br />

ZnEt 2 , CH 2 I 2<br />

rt<br />

SiMe 2 t-Bu<br />

OBn<br />

OBn<br />

261 76%<br />

262 88%<br />

71% ee<br />

>99:1 dr<br />

OAc<br />

i) NIS, MeCN<br />

rt, 12 hr<br />

OBn<br />

i) OsO 4 , NMO, rt AcO OBn<br />

ii) t-BuLi, PhMe 2 SiCl<br />

−100 °C<br />

OBn ii) Hg(OAc) 2 , CH 3 CO 3 H<br />

OBn<br />

iii) Ac 2 O, pyr, rt<br />

SiMe 2 Ph<br />

OAc<br />

263 66% 264 79%<br />

>99:1 dr<br />

Scheme 4.7 – Landais’ synthesis of altrose analogue 161<br />

Using another desymmetrised diene, Landais reported a complementary synthesis<br />

starting from the Tamao silane 265, which was oxidised and alkylated <strong>to</strong> give ether<br />

266, ready for [2,3]-Wittig rearrangement. Rearrangement occurred in modest yield<br />

and with high facial selectivity <strong>to</strong> give allylic ether 267, which again underwent highly<br />

selective anti-dihydroxylation, giving α-D-galac<strong>to</strong>pyranose analogue 268 in 20%<br />

overall yield.<br />

SiMe 2 OMe<br />

O<br />

H 2 O 2 , KF<br />

OH<br />

O<br />

Bu 3 Sn<br />

KH, Bu 3 SnCH 2 I<br />

O<br />

O<br />

265<br />

O<br />

KHCO 3<br />

60 °C, 12 hr<br />

O<br />

O<br />

75%<br />

>99:1 dr 266 82%<br />

n-BuLi<br />

−60 °C 12 hr<br />

OH<br />

267<br />

O<br />

O<br />

51%<br />

i) Ac 2 O, pyr rt<br />

ii) OsO 4 , NMO, rt<br />

HO<br />

OH<br />

OAc<br />

268<br />

O<br />

O<br />

92%<br />

>99:1 dr<br />

Scheme 4.8 – Landais’ synthesis of galac<strong>to</strong>se analogue 161<br />

An alternative method for accessing unsaturated carbocycles is the enzymatic<br />

oxidation of benzene by Pseudomonas putida mutants, first used by Ley and coworkers<br />

in the syntheses of racemic cycli<strong>to</strong>ls. 162 <strong>The</strong> formation of a meso diol<br />

restricted its utility, but Pseudomonas putida mutants were developed that could<br />

oxidise substituted benzenes, yielding desymmetrised, enantiomerically pure diols<br />

136


Chapter 4 – Synthesis of carbasugars<br />

(270). Numerous research groups have taken advantage of these <strong>to</strong> access optically<br />

pure cycli<strong>to</strong>ls, one succinct if unselective example by Carless and Malik is shown in<br />

Scheme 4.9. 163<br />

Microbial oxidation of <strong>to</strong>luene gives optically pure diene 270, which<br />

was protected and dihydroxylated, before the remaining olefin was reduced with good<br />

facial selectivity <strong>to</strong> give ace<strong>to</strong>nide 271. Hydrolysis gave dehydro α-L-fucose analogue<br />

272 in 14% yield from <strong>to</strong>luene.<br />

Me<br />

Me<br />

Me<br />

i) Me 2 C(OMe) 2 ,<br />

Pseudomonas putida<br />

OH TFA<br />

ii) OsO 4 , NMO HO<br />

OH<br />

270<br />

OH<br />

Me<br />

Me<br />

H 2 , 20 psi<br />

O AcOH, H 2 O<br />

OH<br />

PtO 2 HO O<br />

100 °C<br />

HO OH<br />

OH<br />

271<br />

70%<br />

6:1<br />

Scheme 4.9 – synthesis of an α-L-fucose analogue by enzymatic dearomatisation 163<br />

OH<br />

272<br />

96%<br />

O<br />

O<br />

66%<br />

2:3<br />

4.1.3 Synthetic outlook<br />

In the recent review by Gomez and Lopez. 156 104 carbapyranose syntheses were<br />

discussed noting the yield, number of steps, type of molecule made and the starting<br />

material; of the 78 optically enriched syntheses only 13 had overall yields above 30%,<br />

interestingly this dropped for the racemic syntheses, of which only one of the 26 had<br />

an overall yield greater than 30%. <strong>The</strong> yields for the racemic syntheses are<br />

presumably lower for two reasons; most of the racemic syntheses came from less<br />

elaborated starting materials and most research has been focused on enantiomerically<br />

pure sugar analogues.<br />

Since the starting oxazolines can be readily made racemically, a carbasugars synthesis<br />

which used only substrate-controlled selectivity would be equally amenable <strong>to</strong> racemic<br />

and enantiopure synthesis. Furthermore, the authors of the report <strong>to</strong>ok overall yields<br />

from relatively late intermediates such as silane 265 (Scheme 4.8), and it is that a<br />

synthesis of better overall yield can be achieved.<br />

137


4.2 – <strong>Carbasugar</strong> synthesis<br />

4.2 Synthesis of a <strong>Carbasugar</strong> Analogue<br />

Ph<br />

O<br />

N<br />

OMe<br />

102b<br />

Ph<br />

HO<br />

HO<br />

OH<br />

OH<br />

OH<br />

275<br />

Stereochemistry:<br />

Relative set by anti-addition<br />

Absolute set by chosen auxilliary<br />

(sugar shown is L )<br />

Scheme 4.10 – a family of possible analogues<br />

<strong>The</strong> intention of this synthesis is <strong>to</strong> achieve the complete stereoselective oxygenation<br />

of an adduct produced by the methods outlined in the previous chapters. <strong>The</strong> most<br />

suitable aromatic derivatives are the anisoles since these are already partially<br />

oxygenated and dearomatisation gives enol ethers. Whilst enol ethers are versatile in<br />

their own right, they readily yield ke<strong>to</strong>nes, opening up a plethora of chemistry,<br />

furthermore, adduct 102b can be hydrolysed <strong>to</strong> an enone (section 3.2), a motif which<br />

has often been used in making cycli<strong>to</strong>ls. In light of this, and that the yields for addition<br />

are slightly higher, the 4-methoxy oxazoline derivative 102b will be used in the initial<br />

synthetic work. Since 275 contains densely packed hydrophilic and hydrophobic<br />

portions its biological activity might be of interest. Furthermore a synthesis including<br />

the isopropyl group might be seen as a guide for future work whilst we learn about the<br />

behaviour of the pendent oxazolinyl group.<br />

Since this synthesis is intended <strong>to</strong> exemplify the synthetic utility of the oxazoline<br />

chemistry, it is hoped that this substituent may prove useful in two ways; by enhancing<br />

stereoselectivity by hindering one face of the carbocycle, and providing a useful<br />

chromophore for reaction moni<strong>to</strong>ring and purification.<br />

4.2.1 Synthetic strategy<br />

We are afforded the luxury of planning a forward synthesis based upon chemistry we<br />

are most confident will work since all diastereoisomers of 275 are possible synthetic<br />

targets. This is outlined below, with a brief rational of reagents suitable for substratebased<br />

stereoselectivity, much of which is based around the axial position of the<br />

138


Chapter 4 – Synthesis of carbasugars<br />

oxazoline motif, predicted by A-values, and confirmed by vicinal coupling constants<br />

(vide infra).<br />

In this chapter, the oxazoline moiety previously developed will be abbreviated Ox*:<br />

Ph<br />

Ox* = O<br />

N<br />

Ph<br />

Ox*<br />

Ox*<br />

Ox*<br />

[O]<br />

H -<br />

OMe<br />

O<br />

102b 276<br />

OH<br />

anti <strong>to</strong><br />

Ox*& i-Pr<br />

OH<br />

213<br />

OH<br />

axial hydride<br />

delivery<br />

213<br />

i) Protect<br />

HO<br />

ii) OsO 4<br />

HO<br />

anti "Kishi"<br />

dihydroxylation<br />

Ox*<br />

OR<br />

277<br />

OR<br />

HO<br />

HO<br />

OH<br />

OH<br />

OH<br />

278<br />

HO<br />

HO<br />

OH<br />

OH<br />

H<br />

O<br />

α-L-altrose<br />

OH<br />

213<br />

[O]<br />

O<br />

H-bonded<br />

syn epoxidation<br />

Ox*<br />

OH<br />

216<br />

OH<br />

Nu<br />

trans-diaxial<br />

opening<br />

Nu<br />

HO<br />

OH<br />

OH<br />

OH<br />

279<br />

OH<br />

H<br />

HO<br />

O<br />

HO OH<br />

OH<br />

α-L-mannose<br />

Scheme 4.11 – proposed divergent synthesis of carbasugars<br />

Regioselective oxidation of diene 102b would give α-hydroxy ke<strong>to</strong>ne 276 upon<br />

workup, with facial selectivity guided by the equa<strong>to</strong>rial isopropyl and axial oxazoline.<br />

Axial 1,2-reduction of the resulting enone would furnish allylic alcohol 213, which is<br />

intended as the point of variation in this synthesis. Dihydroxylation of allylic alcohols<br />

normally shows good anti-stereoselectivity, reinforced by the axial oxazoline, giving<br />

the stereocentres of the unnatural sugar α-L-altrose. Alternatively, hydrogen bonddirected<br />

epoxidation of the allylic alcohol, followed by hydrolysis would give the<br />

139


4.2 – <strong>Carbasugar</strong> synthesis<br />

stereocentres of α-L-mannose. Enone 276 would also allow further functionalisation<br />

of the carbocycle through the vast chemistry associated with this functional group. It<br />

is anticipated that pentaols 275 will be polar and highly water soluble, and that their<br />

synthesis will require a careful protecting group strategy.<br />

Since two key steps in the planned syntheses rely on the steric bulk of the axial<br />

oxazoline, it was deemed necessary <strong>to</strong> gauge how strong an influence it could have on<br />

the stereochemistry of the adjacent ring.<br />

4.2.2 Influence axial oxazoline on reactivity<br />

<strong>The</strong> axial oxazoline is key <strong>to</strong> the stereoselectivity proposed in the above synthesis.<br />

Whilst an axial conformation has been confirmed by vicinal coupling constants, it<br />

remains <strong>to</strong> be seen if this will affect its reactivity and how rigid the system is.<br />

4.2.2.a Model study<br />

It was felt that dihydroxylation of enone 201 would provide a good indication of the<br />

facial selectivity that could be expected in the synthesis. This olefin was ideally suited<br />

as the oxazoline is the predominant encumbering group, whilst the dihydroxylation<br />

reaction was chosen since the formation of the bulky osmate ester 282 164 would be<br />

very sensitive <strong>to</strong> the surrounding environment, and is a key reaction in the proposed<br />

synthesis.<br />

Ox*<br />

Ox*<br />

Ox*<br />

HO<br />

HO<br />

OsO 4 (1%), NMO.H 2 O<br />

O<br />

CH 2 Cl 2 , 8 d<br />

HO<br />

O<br />

HO<br />

55% O 2%<br />

201<br />

axial<br />

280 281<br />

Ox*<br />

O O<br />

Os<br />

O O<br />

O<br />

282<br />

Scheme 4.12 – facial selectivity imparted by the axial oxazoline<br />

<strong>The</strong> dihydroxylation of the enone under modified Upjohn conditions 165 proceeded<br />

slowly, giving good diastereomeric ratio of 27:1, and relative stereochemistry was<br />

140


Chapter 4 – Synthesis of carbasugars<br />

assigned by nOe (vide infra). This result is consistent with the results of Figueredo et<br />

al. in the diversity-orientated synthesis of gabosines (Scheme 4.13). 166 With matched<br />

bulky groups they observed only one diastereomer, but found that inversion of the α’<br />

centre reversed the stereochemical preference for the reaction. In light of this it is<br />

likely that the presence of the isopropyl group is also important.<br />

OTBS<br />

OTBS<br />

HO<br />

OsO 4 (cat.), NMO<br />

O<br />

SPh<br />

ace<strong>to</strong>ne/H 2 O<br />

HO<br />

O<br />

SPh<br />

70%<br />

OTBS<br />

O<br />

SPh<br />

OsO 4 (cat.), NMO<br />

ace<strong>to</strong>ne/H 2 O<br />

HO<br />

HO<br />

OTBS<br />

O<br />

SPh<br />

62%<br />

dr: 2.8 : 1<br />

166<br />

Scheme 4.13 – matched and mismatched steric encumbrance<br />

A more rapid dihydroxylation of the electron deficient olefin might have been possible<br />

under other conditions, but optimisation of this reaction was not deemed necessary<br />

since it would not significantly affect the stereochemical outcome.<br />

4.2.2.b nOe studies of oxazoline 280<br />

Scheme 4.14 –nOe interactions superposed on structure of 280 (MM2-minimised)<br />

<strong>The</strong> relative stereochemistry of diol 280 was assigned by nOe experiments showing<br />

that the axial H3 pro<strong>to</strong>n (shown) interacts with H5. <strong>The</strong>se experiments revealed very<br />

strong interactions between the individual methyl groups and the pro<strong>to</strong>ns on either face<br />

141


4.2 – <strong>Carbasugar</strong> synthesis<br />

of the oxazoline as depicted, with none <strong>to</strong> the other face; showing that the cyclic<br />

system is very rigid in solution. <strong>The</strong> oxazoline group remained axial throughout the<br />

synthesis (identified by J H2–H3 ), presumably since the cumulative equa<strong>to</strong>rial preference<br />

of the isopropyl and methyl groups (c. 3.5 kcal mol -1 ) was greater than the oxazoline<br />

(methyl ester c. 1.5 kcal mol -1 ). <strong>The</strong> crystal structure of a later product is consistent<br />

with the energy minimised structure presented (Scheme 4.17). With this result in hand<br />

we were confident that the proposed synthesis would proceed with high levels of<br />

substrate control.<br />

4.2.3 Oxidation of the dienyl ether<br />

<strong>The</strong> regioselective oxidation of conjugated silyl enol ethers was developed by<br />

Rubot<strong>to</strong>m <strong>to</strong> give α-hydroxy enones. 167 This was achieved by using the electrophilic<br />

oxidant mCPBA which oxidises the electron rich olefin more rapidly and has since<br />

been applied <strong>to</strong> enol ethers. 168 Unfortunately, when diene 102b was subjected <strong>to</strong><br />

modified Rubot<strong>to</strong>m conditions, enone 276 was isolated in very low quantities with<br />

many unidentified by-products, including significant amounts of enone 201.<br />

Ox*<br />

Ox*<br />

T n 276 /%<br />

OMe<br />

102b<br />

mCPBA (n eq)<br />

CH 2 Cl 2 , T °C<br />

O<br />

276<br />

OH<br />

20 3.0 7<br />

– 40 1.2 3<br />

– 78 1.2 n.r.<br />

Table 4.1 – attempted Rubot<strong>to</strong>m oxidation of the dienyl ether<br />

In a similar manner <strong>to</strong> Rubot<strong>to</strong>m, McCormick used osmium tetroxide <strong>to</strong> oxidise<br />

unconjugated silyl enol ethers <strong>to</strong> α-hydroxy ke<strong>to</strong>nes. 169 Since dihydroxylation is a<br />

pericyclic process 170 involving the HOMO of the olefin, the more electron rich alkene<br />

will again react first. Enol ether 102b was subject <strong>to</strong> the conditions of Upjohn 171<br />

(entries a-d, Table 4.2) and Poli 172 (entries e, f).<br />

142


Chapter 4 – Synthesis of carbasugars<br />

Ox*<br />

Ox*<br />

i) OsO 4 , NMO, solvent<br />

ii) reducing agent (aq)<br />

OMe<br />

O<br />

102b 276<br />

OH<br />

Ox*<br />

OH<br />

O<br />

283<br />

Entry Solvent Reductant (pH) Workup ratio 276 : 283 * 276 / %<br />

a t-BuOH / H 2 O Na 2 SO 3 (8) Aq 86 : 14 47<br />

b t-BuOH / H 2 O Na 2 S 2 O 5 (4) Aq 95 : 5 68<br />

c Ace<strong>to</strong>ne / H 2 O Na 2 S 2 O 5 (4) Aq 87 : 13 50<br />

d t-BuOH / H 2 O Na 2 S 2 O 5 (4) SiO 2<br />

‡<br />

e CH 2 Cl 2 / H 2 O Na 2 S 2 O 5 (4) SiO 2<br />

‡<br />

f CH 2 Cl 2 Na 2 S 2 O 5 (4) SiO 2<br />

‡<br />

97 : 3 93<br />

73 : 5 ** –<br />

78 : 22 73<br />

* determined by 1 H NMR of crude material; ** + 22% 201 ‡ passed thorough silica plug<br />

Table 4.2 – dihydroxylation of the dienyl ether<br />

<strong>The</strong> oxidation was completely regioselective giving α-hydroxyenone 276 in high yield,<br />

although surprisingly accompanied by dienone 283. <strong>The</strong> presence of greater amounts<br />

of the dienone under moderately alkaline quench for a short period of time (c. 1 hr,<br />

entry a) implies that enone 276 is highly base sensitive. This was confirmed during<br />

the attempted benzylation of enone 276 under the conditions employed by Lockwood<br />

in the modification of carotenoids which returned dienone 283 (Scheme 4.15). 173<br />

Ox*<br />

O<br />

276<br />

OH<br />

pKa in DMSO<br />

i) LiHMDS (1.2 eq)<br />

CH 2 Cl 2 , -20 °C<br />

ii) BnBr (1.3 eq)<br />

O<br />

OMe<br />

Ox*<br />

O<br />

283<br />

Ph<br />

O<br />

OH<br />

24.6 174 22.9 174<br />

50%<br />

80% conv<br />

OMe<br />

HO<br />

Ox*<br />

O<br />

O H<br />

284<br />

30.3 175<br />

Scheme 4.15 – au<strong>to</strong>xidation of 276<br />

Under the strongly basic conditions, it is unclear whether this oxidation of 276<br />

occurred during the reaction – solvents were not degassed – or upon workup.<br />

However, a small excess of base returning a relatively high yield of dienone lends<br />

143


4.2 – <strong>Carbasugar</strong> synthesis<br />

support <strong>to</strong> the formation of diene 284 – (Scheme 4.15) via a single depro<strong>to</strong>nation. Even<br />

though this seems unlikely as the secondary alcohol might be expected <strong>to</strong> be both<br />

kinetically and thermodynamically more acidic, it is consistent with the pKas of related<br />

compounds in DMSO, and with the observation of the dienone in relatively neutral<br />

condition (Table 4.2). Anion 284 – would receive additional stabilisation from<br />

delocalisation of its charge; consistent with the strong hydrogen bonding seen in the IR<br />

and 1 H NMR spectra of 276.<br />

<strong>The</strong> formation of dienone 283 in the oxidation of the enol ether even under weakly<br />

acidic conditions (entry b, Table 4.2), makes the absence of the diastereomeric epi-276<br />

conspicuous; raising the possibility that the dienone formed under these conditions<br />

comes from oxidation of the opposite face (285, Scheme 4.16). Further oxidation<br />

might then take place under the reaction conditions or upon workup; below are the<br />

equilibria present in the reaction, again intermediate 284 would be susceptible <strong>to</strong><br />

further oxidation.<br />

Ox*<br />

Ox*<br />

[O]<br />

Ox*<br />

−H +<br />

Ox*<br />

+H +<br />

OH<br />

284<br />

OH<br />

O<br />

283<br />

OH<br />

MeO<br />

OH<br />

OH<br />

285<br />

H<br />

O<br />

OH<br />

−H +<br />

Ox*<br />

OH<br />

O<br />

epi-276<br />

Scheme 4.16 – proposed in-situ oxidation of epi-276<br />

Oxidation of olefins <strong>to</strong> α-dike<strong>to</strong>nes is known <strong>to</strong> occur under Upjohn conditions 176<br />

although hemiacetal 285 – the product of disfavoured syn oxidation – would not be<br />

amenable <strong>to</strong> further oxidation. Rapid hydrolysis of 285 would give epi-276, which is<br />

not isolated, but might be even more sensitive <strong>to</strong> base than 276 (vide supra) and<br />

readily tau<strong>to</strong>merise <strong>to</strong> diene 284, which might oxidise <strong>to</strong> the dienone under the reaction<br />

conditions.<br />

144


Chapter 4 – Synthesis of carbasugars<br />

4.2.4 Enone reduction<br />

Reduction of enone 276 with a small nucleophile is expected <strong>to</strong> proceed from the axial<br />

face <strong>to</strong> give equa<strong>to</strong>rial alcohol 213. <strong>The</strong> 1,2-reduction of cyclic enones is normally<br />

achieved with high degrees of regioselectivity 177 and stereoselectivity 178 by the use of<br />

Luche conditions, which employ s<strong>to</strong>ichiometric cerium trichloride and sodium<br />

borohydride. However, the stereoselective reduction has also been achieved using 9-<br />

BBN, 179 DIBAlH 180 and sodium borohydride without any additive. 181<br />

In the Luche reduction, it is postulated 178 that the lanthanide additive promotes direct<br />

1,2-addition <strong>to</strong> the unsaturated system by promoting the rapid methanolysis of the<br />

borohydride <strong>to</strong> generate what are termed mixed methoxyborohydrides. <strong>The</strong><br />

regioselectivity is in turn attributed <strong>to</strong> the hard nature of these species, rather than any<br />

complexation of the carbonyl by the lanthanide.<br />

Whilst this is not supported by experiments with trimethoxyborohydride – which<br />

shows identical regioselectivity <strong>to</strong> borohydride and improves with addition of<br />

lanthanide – it is consistent with a number of other observations. Firstly,<br />

regioselectivity increases with dilution in methanol and ethanol. Secondly, when<br />

exploring possible catalysis, it was observed that just 25 mol% of cerium returns<br />

regioselectivities above 95:5, and although not commented on, this would strongly<br />

support the role of cerium as catalysing the first methanolysis, rather than as<br />

complexing the enone.<br />

<strong>The</strong> nature of the reducing species still remains unclear however as<br />

alkoxyborohydrides are prone <strong>to</strong> further disproportionation, 182 which cerium<br />

trichloride may also catalyse. It is of interest that Luche’s investigations were almost<br />

exclusively conducted in alcoholic solvents due <strong>to</strong> poor solubility of cerium<br />

trichloride, however, unoptimised studies of Sm and Eu salts in THF were also<br />

promising. 178 Whilst it is clear is that under the Luche conditions cerium coordination<br />

<strong>to</strong> the enone plays no role, this may not be true for other solvent systems.<br />

<strong>The</strong> application of these conditions is shown below (Table 4.3, entries a-c), alongside<br />

reduction in the absence of cerium trichloride.<br />

145


4.2 – <strong>Carbasugar</strong> synthesis<br />

Ox*<br />

Ox*<br />

Ox*<br />

NaBH 4<br />

O<br />

OH<br />

T °C<br />

OH<br />

OH<br />

OH<br />

OH<br />

quant.<br />

276 213<br />

287<br />

Entry T Conditions Reaction time 213 : 287<br />

a rt + CeCl 3 .7H 2 O 10 min 8 : 1<br />

b 0 + CeCl 3 .7H 2 O 20 min 10 : 1<br />

c –60 + CeCl 3 .7H 2 O 60 min 5 : 1<br />

d 0 – 30 min 10 : 1<br />

e 0 – 6 hr > 20 : 1<br />

Table 4.3 – borohydride reduction of the hydroxyenone<br />

<strong>The</strong> stereoselectivity of the reductions do not correlate with either reagent or<br />

temperature, but instead correlate strongly with the time of the reaction. Whilst this<br />

was initially puzzling, it was found that enone 276 does not visualise well under either<br />

UV irradiation or permanganate stain, but only under the molybdenate-based PMA<br />

stain. When reactions were moni<strong>to</strong>red using PMA stain, it was found that the reaction<br />

was considerably slower than previously believed. Since sodium borohydride only<br />

decomposes slowly in aqueous ammonium chloride, 183 which had been used <strong>to</strong> quench<br />

the reactions, it is believed that unreacted borohydride species were responsible for the<br />

loss of diastereoselectivity upon warming in entries a-d. When appropriate, future<br />

reductions were quenched with acetic acid.<br />

Under the mildly basic Luche conditions (entries a-c) it was found that the enone was<br />

prone <strong>to</strong> oxidation <strong>to</strong> small amounts of dienone 283 (Scheme 4.15). This could be<br />

countered by conducting the reaction at lower pH, which has been shown have little<br />

effect on the regioselectivity. 178<br />

<strong>The</strong> structure of 213 was confirmed by x-ray<br />

diffraction.<br />

146


Chapter 4 – Synthesis of carbasugars<br />

Scheme 4.17 – crystal structure of allylic alcohol 213<br />

Diol 213 is highly crystalline but inseparable from the syn-diol 287 by flash column<br />

chroma<strong>to</strong>graphy. Whilst the majority could be isolated by recrystallisation, it could<br />

also be separated by the formation of the ace<strong>to</strong>nide of the syn-diol, and subsequent<br />

chroma<strong>to</strong>graphy.<br />

DIBAlH has also been used <strong>to</strong> effect the stereoselective 1,2-reduction of similar<br />

enones. 180 Unfortunately only 1,4-reduction was observed (288), with mainly starting<br />

material isolated from the reaction.<br />

Ox*<br />

Ox*<br />

DIBAlH, CH 2 Cl 2<br />

OH<br />

-78 °C<br />

O<br />

O<br />

276 288<br />

OH<br />

15%<br />

40% conv<br />

Scheme 4.18 – DIBAlH reduction<br />

4.2.5 Protecting group strategy<br />

It was anticipated that as the number of polar groups increased in the synthesis<br />

isolation and purification would become more difficult and protecting groups would be<br />

needed <strong>to</strong> mask some of the free alcohols. <strong>The</strong> protecting group would have <strong>to</strong><br />

withstand strongly alkylating, moderately reducing and moderately acidic reaction<br />

conditions; it also should be removed without the need for aqueous workup. In light of<br />

these requirements, the benzyl ether protecting group is ideally suited, and there is<br />

significant precedent its use in sugar chemistry.<br />

147


4.2 – <strong>Carbasugar</strong> synthesis<br />

Ox*<br />

Ox*<br />

NaH (4 eq), BnBr (5 eq)<br />

OH<br />

213<br />

OH<br />

Bu 4 NI (cat), DMF<br />

OBn<br />

289<br />

OBn<br />

72%<br />

Scheme 4.19 – benzylation<br />

<strong>The</strong> benzylation conditions were adapted from those of Provelenghiou 184<br />

using<br />

catalytic tetrabutylammonium iodide, generating benzyl iodide in situ, <strong>to</strong> assist<br />

functionalisation of the secondary alcohols. Dimethylformamide was chosen as<br />

solvent as it promotes the nucleophilicity of anionic species through solubilisation of<br />

the counter ion. 185<br />

This yield was sufficient <strong>to</strong> continue the synthesis, however it<br />

might be improved by benzylation with benzyltrichloroacetimidate, developed by<br />

Bundle for use in sugar chemistry. 186<br />

4.2.6 Oxidation of the allylic alcohol<br />

Allylic alcohol 213 is the point of divergence in this synthesis since two<br />

complementary stereoselective oxidations exist.<br />

4.2.6.a Epoxidation<br />

In 1957 Henbest demonstrated that stereoselective epoxidation of allylic alcohols may<br />

be effected through association with the alcohol with an organic peracid. 187 A number<br />

of other stereoselective methods exist for the epoxidation of allylic alcohols, the most<br />

noteworthy being the seminal work by Sharpless and Katsuki; 188 an entirely reagentcontrolled<br />

method using (+) or (–) diethyl tartrate as the source of chirality.<br />

Whilst the original studies of Henbest were performed using peracids, these are not<br />

always the best reagents. An insightful study in<strong>to</strong> the selectivity of such oxidations<br />

was recently authored by Adam 168 comparing both regio and chemo selectivity of<br />

different reagents with acyclic allylic alcohols, and making mechanistic inferences<br />

from the results. He divided oxidants in<strong>to</strong> two broad groups; hydrogen bonding<br />

reagents (such as peracids) and metal-alcoholate binding reagents (typified by the<br />

vanadyl acetyl ace<strong>to</strong>ace<strong>to</strong>nate, VO(acac) 2 system). Prior studies found these reagents<br />

<strong>to</strong> differ in their optimal reaction geometry, specifically the angle, α, between the<br />

148


Chapter 4 – Synthesis of carbasugars<br />

plane of the olefin and the allylic C–O bond. Hydrogen-bonding reagents generally<br />

proceed through a transition state with α ~120° whilst metal-alcoholate reagents prefer<br />

α ~ 40°.<br />

Adam applied this analysis <strong>to</strong> cyclohexenols, concluding that since α for equa<strong>to</strong>rial<br />

cyclohexenols is approximately 140°, hydrogen bonding reagents are more suited <strong>to</strong><br />

their epoxidation. This is somewhat borne out when such reagents are considered in a<br />

rigid system such as allylic alcohols 290 (Table 4.4).<br />

t-Bu<br />

290a<br />

pseudoaxial OH<br />

OH<br />

H<br />

α<br />

t-Bu<br />

H<br />

α<br />

OH<br />

α = +110° α = +140°<br />

290b<br />

pseudoequa<strong>to</strong>rial OH<br />

Me<br />

R<br />

Ox*<br />

213<br />

OH OH<br />

α = +134°<br />

syn : anti ratio<br />

Entry oxidant solvent axial 290a equa<strong>to</strong>rial 290b<br />

a 168 mCPBA CH 2 Cl 2 90:10 98:2<br />

b 189 CF 3 CO 3 H CH 2 Cl 2 99:1 99:1<br />

c 168 DMDO CCl 4 58:42 82:18<br />

d 168 DMDO ace<strong>to</strong>ne 30:70 60:40<br />

Table 4.4 – epoxidation of allylic alcohols 290 by different reagents<br />

However it should be noted that epoxidation of cyclohexen-3-ol (α = 110° or 140°)<br />

with VO(acac) 2 proceeds with 98:2 syn-selectivity 190 despite the apparent unoptimal α-<br />

values. This casts some doubt upon the validity of Adam’s argument, but with many<br />

examples demonstrating their use, peracids are clearly the reagents of choice since they<br />

are cheap, readily available and easily handled.<br />

<strong>The</strong> crystal structure of 213 shows the allylic C6–C5=C4–O <strong>to</strong>rsional angle <strong>to</strong> be 134°;<br />

well-suited <strong>to</strong> the conditions suggested by Adam. To direct the mCPBA <strong>to</strong> the synface<br />

the free alcohol 213 would be used for the epoxidation. <strong>The</strong> slightly more polar<br />

epoxide is not expected <strong>to</strong> present any isolation problems since it has the same number<br />

of hydrogen bonding sites as the diol which showed no hydrophilicity.<br />

149


4.2 – <strong>Carbasugar</strong> synthesis<br />

Ox*<br />

Ox*<br />

mCPBA, CH 2 Cl 2<br />

O<br />

OH 0 °C<br />

OH<br />

OH<br />

213 216<br />

OH<br />

quant.<br />

Scheme 4.20 – epoxidation of allylic alcohol<br />

Pleasingly, complete facial selectivity was observed without the need for optimisation;<br />

the epoxide is isolated cleanly from the reductive workup without the need for further<br />

purification. In keeping with the protecting group strategy, epoxide 216 was<br />

benzylated.<br />

Ox*<br />

Ox*<br />

Ox*<br />

O<br />

OH<br />

216<br />

OH<br />

NaH (2.4 eq), BnBr<br />

Bu 4 NI (cat), DMF<br />

O<br />

OBn<br />

291<br />

O<br />

OH<br />

OBn<br />

68%<br />

OBn<br />

10%<br />

292<br />

NaH, BnBr, Bu 4 NI<br />

DMF<br />

35% (55% conv)<br />

Scheme 4.21 – benzylation<br />

When using a slight excess of sodium hydride, monobenzyl ether 291 – identified by<br />

1 H- 1 H correlation spectroscopy – was isolated with moderate selectivity. With no clear<br />

use for this alcohol it was re-subjected <strong>to</strong> the reaction conditions, returning mainly the<br />

desired dibenzyl ether 292, with some mono-benzylated starting material recovered.<br />

4.2.6.b Dihydroxylation of the allylic alcohol<br />

<strong>The</strong> anti-selectivity in the osmylation of cyclic and acyclic allylic alcohols was<br />

discovered in the labora<strong>to</strong>ries of Kishi 191 and has been borne out by the research of a<br />

number of other groups. 192 <strong>The</strong> Kishi model <strong>to</strong> rationalise the stereochemical outcome<br />

assumes a transition state resembling the ground state of the alkene which is governed<br />

by allylic (1,3) strain.<br />

150


Chapter 4 – Synthesis of carbasugars<br />

OsO 4<br />

L<br />

R 2 O<br />

R 1<br />

H<br />

R c<br />

R t<br />

Kishi model:<br />

ground state-like transition state<br />

governed by A(1,3) strain<br />

Scheme 4.22 – Kishi model for dihydroxylation of allylic alcohols<br />

It was later found by Evans 193 that for 1,1-disubstituted olefins (R t = R c = H), that<br />

decreasing the size of R 2 or increasing L enhanced facial selectivity, despite reducing<br />

the conformational preference for the ground state. <strong>The</strong>se observations lent support <strong>to</strong><br />

reacting conformer models of Houk and Vedejs. 192 Interestingly, these models all<br />

assume a single [3+2] cycloaddition <strong>to</strong> form the osmate ester, even though this was not<br />

shown until computational and kinetic studies were performed almost 10 years later. 170<br />

Subsequent computational modelling by Houk 164 showed that whilst for 1,2-cissubstituted<br />

alkenes the dominant fac<strong>to</strong>r in the transition state conformation was in fact<br />

A(1,3) strain, in all other cases, the transition state was determined primarily by the<br />

inside alkoxy effect, with a further contribution <strong>to</strong> minimise σ* C-O -π interactions which<br />

withdraw electron density from the nucleophilic olefin.<br />

E +<br />

OsO 4<br />

(Outside) (Inside)<br />

H OR 2<br />

R 1<br />

L (Anti)<br />

H<br />

L<br />

R 1 R t<br />

H<br />

OR 2<br />

Houk model:<br />

transition state determined by<br />

inside alkoxy effect<br />

Scheme 4.23 – Houk model for dihydroxylation of allylic alcohols<br />

Although many studies have investigated the origin of the asymmetry of<br />

dihydroxylation in acyclic systems, little attention has been given <strong>to</strong> cyclic systems. 194<br />

<strong>The</strong> stereochemical outcome of the reaction is attributed <strong>to</strong> a minimisation of the<br />

dipole in the transition state, consistent with the increased diastereoselectivity observed<br />

for oxidation of pseudo-axial allylic alcohol 295 by Donohoe (Scheme 4.24).<br />

151


4.2 – <strong>Carbasugar</strong> synthesis<br />

OsO 4 (cat.), NMO<br />

OH<br />

OH<br />

t-Bu OH<br />

OH equa<strong>to</strong>rial<br />

ace<strong>to</strong>ne/H 2 O<br />

OsO 4 (cat.), NMO<br />

t-Bu<br />

OH<br />

OH<br />

91%<br />

85:15 dr<br />

OH<br />

t-Bu<br />

OH<br />

OH axial<br />

295<br />

ace<strong>to</strong>ne/H 2 O<br />

t-Bu<br />

OH<br />

90%<br />

94:6 dr<br />

Scheme 4.24 – dihydroxylation of axial and equa<strong>to</strong>rial alcohols 195<br />

Kishi showed that etherification does not affect facial selectivity significantly, whilst<br />

esterification does, shown particularly well by Arjona et al. (Scheme 4.25). 196<br />

OR 1<br />

OR 2<br />

OR 1<br />

OR 2<br />

OR 1<br />

OR 2<br />

OsO 4 (cat.), Me 3 NO<br />

ace<strong>to</strong>ne/H 2 O<br />

OH<br />

OH<br />

296 297<br />

OH<br />

OH<br />

R1 R2 296 : 297<br />

TBS Me 50:50<br />

TBS Bz 80:20<br />

Bn Bz 76:24<br />

196<br />

Scheme 4.25 – effect of etherification vs esterification on dihydroxyation<br />

This shows that dihydroxylation of the olefin may employ either the free diol or the<br />

benzyl ether. In our synthesis, if the free diol is used, the resulting tetraol would at<br />

best be very polar, and at worst be amphiphilic, causing problems with isolation by<br />

normal methods. As such, benzyl ether 289 was subject <strong>to</strong> a range of standard<br />

dihydroxylation conditions.<br />

Ox*<br />

OBn<br />

289<br />

OBn<br />

OsO 4 , NMO<br />

solvent<br />

HO<br />

HO<br />

Ox*<br />

OBn<br />

300<br />

OBn<br />

Solvent Yield / %<br />

t-BuOH / H 2 O n.r.<br />

ace<strong>to</strong>ne / H 2 O n.r.<br />

CH 2 Cl 2 96<br />

Scheme 4.26 – dihydroxylation of allyl ether<br />

Under the conditions of Poli 172 only the expected anti-diol was observed, although<br />

once again the reaction was slow, taking six days <strong>to</strong> complete. <strong>The</strong> relative<br />

stereochemistry was assigned by vicinal coupling constants, and later confirmed by<br />

crystal structure. <strong>The</strong> failure of the standard Upjohn conditions is surprising, although<br />

152


Chapter 4 – Synthesis of carbasugars<br />

during the course of the reactions black deposits were observed at the neck of the<br />

reaction vessel. This is presumed <strong>to</strong> be osmium dioxide, indicating a lack of available<br />

re-oxidant, even though two equivalents of NMO were used, and the oxidant is stable<br />

under the conditions.<br />

Benzylation of the resulting diol gave a mixture of mono- and dibenzylation products.<br />

Tribenzyl ether 301 was isolated as a single compound and characterised by COSY<br />

NMR, implying that benzylation first occurs at the more encumbered neopentylic<br />

alcohol. This alcohol was re-subjected <strong>to</strong> the reaction conditions <strong>to</strong> give perbenzyl<br />

ether 302 in good yield, ready for onward reaction.<br />

Ox*<br />

Ox*<br />

Ox*<br />

HO<br />

BnO<br />

NaH (2.4 eq), BnBr<br />

BnO<br />

HO<br />

OBn<br />

300<br />

OBn<br />

Bu 4 NI (cat), DMF<br />

HO<br />

OBn BnO OBn<br />

OBn<br />

54 %<br />

OBn<br />

33%<br />

301 302<br />

NaH, BnBr, Bu 4 NI<br />

DMF<br />

70%<br />

Scheme 4.27 – benzylation of diol<br />

4.2.7 Synthesis of an altrose analogue<br />

Oxazoline 302 has all the stereocentres of α-L-altrose (Scheme 4.11). Employing the<br />

alkylation-reduction-hydrolysis-reduction procedure (section 3.2), would reveal the<br />

primary alcohol, and debenzylation would yield the desired carbasugar analogue.<br />

302<br />

MeOTf<br />

then NaBH 4<br />

BnO<br />

BnO<br />

Ph<br />

O<br />

Ph<br />

NMe<br />

i) (CO 2 H) 2 , THF/water<br />

7 d, 60 °C<br />

ii) NaBH 4 , MeOH<br />

OBn<br />

OBn<br />

70%<br />

225<br />

Scheme 4.28 – removal of oxazoline auxiliary<br />

<strong>The</strong> alkylation-reduction step proceeded well; however as previously discussed the<br />

hydrolysis was much slower than for other related oxazolidines, which had typically<br />

BnO<br />

BnO<br />

OH<br />

OBn<br />

304<br />

OBn<br />

85%<br />

153


4.2 – <strong>Carbasugar</strong> synthesis<br />

taken one <strong>to</strong> three days at ambient temperature. In the next section, this is shown <strong>to</strong> be<br />

due <strong>to</strong> neighbouring group participation of a cis hydroxyl group at the 4 position.<br />

OH<br />

OH<br />

OH<br />

BnO<br />

Pd(OH) 2<br />

HO<br />

HO<br />

H<br />

O<br />

BnO<br />

OBn<br />

304<br />

OBn<br />

85%<br />

H 2 , 20 bar<br />

HO<br />

OH<br />

278<br />

OH<br />

quant.<br />

HO OH<br />

OH<br />

α-L-Altrose<br />

Scheme 4.29 – final step in synthesis of α-L-altrose analogue<br />

Pleasingly, hydrogenolysis using Pearlman’s catalyst 197 proceeded cleanly without the<br />

need for purification, and the relative stereochemistry was confirmed by crystal<br />

structure.<br />

water molecule<br />

Scheme 4.30 – crystal structure confirming relative stereochemistry of 278<br />

Somewhat surprisingly, pentaol 278 was apolar enough <strong>to</strong> be purified on normal phase<br />

silica, eluting with just ethyl acetate (R f ~0.1). This was unexpected and led <strong>to</strong> the<br />

review of the protecting group strategy (vide infra).<br />

154


Chapter 4 – Synthesis of carbasugars<br />

Ox*<br />

Ox*<br />

Ox*<br />

Ox*<br />

a<br />

b<br />

c,d<br />

OMe<br />

101b<br />

OMe<br />

102b<br />

Ox*<br />

O<br />

276<br />

OH<br />

OH<br />

OBn<br />

289<br />

OBn<br />

e,f<br />

BnO<br />

g<br />

BnO<br />

BnO<br />

OBn<br />

OBn<br />

BnO<br />

OBn<br />

OBn<br />

302<br />

304<br />

OH<br />

h<br />

HO<br />

HO<br />

OH<br />

278<br />

OH<br />

α-L-altrose<br />

analogue<br />

18.8% overall yield in<br />

10 steps from arene 101b<br />

a) i-PrLi, THF, DMPU, 20 min, –78 °C, then MeI, 70%; b) OsO 4 , NMO, t-BuOH then Na 2 S 2 O 5 ,<br />

93%; c) NaBH 4 , MeOH, 0 °C, 6 hr, 98%; d) BnBr, NaH, Bu 4 NI, DMF, 72%; e) OsO 4 , NMO,<br />

CH 2 Cl 2 , 96%; f) BnBr, NaH, Bu 4 NI, DMF, 71%; g) MeOTf, CH 2 Cl 2 , then NaBH 4 , 0 °C,<br />

MeOH/THF, 70%; ii) (CO 2 H) 2 , THF/H 2 O, 50 °C 24 hr, iii) NaBH 4 , MeOH, 85% (2 steps); h)<br />

Pd(OH) 2 , H 2 (20 bar), quant.<br />

Scheme 4.31 – first synthesis of the α-L-altrose analogue<br />

4.2.8 Synthesis of an epoxycarbasugar<br />

<strong>The</strong> successful synthesis of the altrose analogue 278 indicated that protecting groups<br />

may not be necessary, as such oxazoline removal was attempted with diol 216 without<br />

benzylation.<br />

O<br />

Ph<br />

O<br />

OH<br />

N<br />

Ph<br />

OH<br />

MeOTf<br />

t hr<br />

then NaBH 4<br />

Ph<br />

O<br />

OH<br />

216 306<br />

O<br />

H<br />

H<br />

Ph<br />

NMe<br />

OH<br />

O<br />

O<br />

O<br />

307<br />

OH<br />

t 306 / % 307 / %<br />

16 40 30<br />

4 79


4.2 – <strong>Carbasugar</strong> synthesis<br />

As well as the expected oxazolidine, an almost equivalent amount of lac<strong>to</strong>ne 307 was<br />

seen when the alkylation reaction was left overnight before reduction. This<br />

unexpected product is clearly produced by base catalysed hydrolysis of the ammonium<br />

salt 308 before reduction (Scheme 4.33) and is only possible due <strong>to</strong> the 1,4-cis<br />

relationship between the oxazoline and the free alcohol. <strong>The</strong> bicyclic structure of 307<br />

is corroborated by a 1 Hz 4 J H4-H6 “W-coupling”.<br />

Ph<br />

Ph<br />

O<br />

O<br />

N<br />

OH<br />

216<br />

OH<br />

Ph<br />

O<br />

Ph<br />

OH<br />

H N O<br />

O<br />

OH<br />

308<br />

Scheme 4.33 – lac<strong>to</strong>nisation of oxazoline 216<br />

O<br />

O<br />

O<br />

307<br />

OH<br />

<strong>The</strong> increase of lac<strong>to</strong>ne 307 with time shows that hydrolysis occurs under the<br />

alkylation conditions rather than the mildly basic reduction. <strong>The</strong> hydrolysis is likely<br />

catalysed by trace water which would facilitate pro<strong>to</strong>n transfers and is basic enough <strong>to</strong><br />

depro<strong>to</strong>nate the final pro<strong>to</strong>nated lac<strong>to</strong>ne. Hydrolysis of oxazolidine 306 proceeded<br />

smoothly returning epoxycabasugar 309 in excellent yield over three steps. <strong>The</strong> rate of<br />

reaction was consistent with the hydrolysis of earlier oxazolidines with the cis-1,4<br />

pattern discussed.<br />

O<br />

Ph<br />

O<br />

N<br />

OH<br />

216<br />

Ph<br />

OH<br />

MeOTf, 2 hr<br />

then NaBH 4<br />

O<br />

Ph<br />

H<br />

H<br />

O<br />

OH<br />

306<br />

Ph<br />

NMe<br />

OH<br />

i) (CO 2 H) 2 , THF/water<br />

17 hr, 50 °C<br />

ii) NaBH 4 , MeOH<br />

O<br />

HO<br />

OH<br />

OH 83%<br />

3 steps<br />

309<br />

Scheme 4.34 – oxazolidine hydrolysis facilitated by 1,4-cis-hydroxyl group<br />

156


Chapter 4 – Synthesis of carbasugars<br />

4.2.9 <strong>The</strong> 1,4 transannular relationship for oxazolidine hydrolysis<br />

Whilst lac<strong>to</strong>nisation of the quaternised oxazoline showed that the 1,4-cis-transannular<br />

interaction was possible, material was already in hand which could show that<br />

neighbouring group participation was indeed important. Alkylation of the monobenzylated<br />

oxazoline 291 proceeded, on small scale, <strong>to</strong> give oxazolidine 299 in<br />

comparable yield <strong>to</strong> previous reactions. Hydrolysis of this oxazolidine was determined<br />

by 1 H NMR <strong>to</strong> be approximately 10% complete after 24 hours at 50 °C. This decrease<br />

in rate by an order of magnitude is consistent with the observations in the previous<br />

section, showing that when available, neighbouring group participation is the dominant<br />

mechanism for oxazolidine hydrolysis.<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

O<br />

N<br />

OBn<br />

OH<br />

MeOTf, 18 hr<br />

then NaBH 4<br />

O<br />

H<br />

H<br />

O<br />

OBn<br />

291 299<br />

NMe<br />

OH<br />

75%<br />

(CO 2 H) 2 , THF/water<br />

24 hr, 50 °C<br />

Scheme 4.35 – oxazolidine hydrolysis without cis-hydroxyl<br />

c. 10%<br />

hydrolysed<br />

4.3 Revised Synthetic Strategy<br />

<strong>The</strong> above section described the successful application of the dearomatising chemistry<br />

<strong>to</strong> the synthesis of an analogue of altrose. In the process, it raised a number of areas of<br />

synthetic importance which might expedite a revised synthesis. It is clear that a<br />

hydroxyl group is necessary <strong>to</strong> facilitate oxazolidine hydrolysis, which would normally<br />

have a profound impact on a protecting group strategy; however the functional<br />

simplicity and surprising hydrophobicity mean no such strategy is necessary.<br />

Whilst the lac<strong>to</strong>nisation of the cis-hydroxyoxazoline should not have been so<br />

surprising, it opens new synthetic possibilities for oxazoline removal and controlling<br />

stereochemistry around the carbocycle. This will be explored in the synthesis of a<br />

mannose analogue in section 4.5.<br />

157


4.4 – Revised altrose synthesis<br />

4.4 <strong>The</strong> Protecting Group-Free Synthesis of an Altrose Analogue<br />

<strong>The</strong> revised synthetic strategy of the altrose analogue (Scheme 4.36) will build upon<br />

the key steps of the previous synthesis but remove the protecting group steps. It is also<br />

anticipated that a step can be saved in routes B and C by simultaneous 1,2-reduction of<br />

the enone and the quaternised oxazoline.<br />

Ox*<br />

Ox*<br />

i) H - HO<br />

A<br />

OH ii) [O]<br />

HO OH<br />

O<br />

OH<br />

276<br />

309<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

O<br />

N<br />

B<br />

OH<br />

310<br />

OH<br />

[O]<br />

HO<br />

HO<br />

OH<br />

311<br />

OH<br />

HO<br />

HO<br />

[O]<br />

HO<br />

C<br />

OH<br />

312<br />

OH<br />

HO<br />

OH<br />

278<br />

OH<br />

Scheme 4.36 – proposed protecting group-free syntheses of altrose analogue<br />

158


Chapter 4 – Synthesis of carbasugars<br />

4.4.1 <strong>Route</strong> A<br />

<strong>Route</strong> A is the same as the first synthesis but excludes the two protecting groups steps.<br />

Intermediate 213 had been previously synthesised in 64% in three steps from the<br />

anisole derivative.<br />

Entry Conditions<br />

Ox*<br />

OH<br />

213<br />

OH<br />

OsO 4 , conditions<br />

no<br />

reaction<br />

a CH 2 Cl 2, NMO.H 2 O nr<br />

b t-BuOH/H 2 O, NMO nr<br />

c<br />

quinuclidine,<br />

K 3 Fe(CN) 6 , K 2 CO 3<br />

nr<br />

Table 4.5 – dihydroxylation of allylic alcohol (route A)<br />

Surprisingly, no reaction was seen for this dihydroxylation under a range of conditions.<br />

No reaction had occurred after 4 weeks under the Poli conditions (entry a, Table 4.5),<br />

whilst standard Upjohn conditions failed, as did the modified AD conditions of<br />

Warren, 176 the racemic dihydroxylation, RD (entry c). In light of the close precedent<br />

in the previous synthesis this is especially disappointing, however the remaining routes<br />

are both one step shorter than route A.<br />

4.4.2 <strong>Route</strong> B or C: a model dihydroxylation<br />

<strong>Route</strong>s B and C involve the same number of synthetic steps, but differ in the execution<br />

of the key dihydroxylation step. In the previous synthesis it was assumed that the<br />

matched “Kishi” stereoelectronics and the encumbrance afforded by the axial<br />

oxazoline were responsible for the high diastereoselectivity. However this was not<br />

tested, and is only now important since two different routes are being considered.<br />

Whilst it may seem clear that route B would afford greater stereoselectivity, it is also<br />

possible that the internal amine will complex osmium, shutting down the catalytic<br />

cycle; dihydroxylation in route C would not face this problem.<br />

In a model study, the dihydroxylation of allylic alcohol 225 was undertaken, also<br />

serving <strong>to</strong> assign the relative stereochemistry of C4 (Scheme 4.37). As expected, the<br />

anti-diol was favoured by Kishi selectivity (vide supra), however the selectivity was<br />

significantly worse than in the previous synthesis, when it was matched by the<br />

encumbrance of the oxazoline. In light of this, it seemed likely that route C would<br />

159


4.4 – Revised altrose synthesis<br />

suffer from poor facial selectivity and route B was favoured. Debenzylation of the<br />

resulting diol gave tetraol 315, which was apolar enough <strong>to</strong> elute on silica gel.<br />

HO<br />

BnO<br />

BnO<br />

BnBr, NaH<br />

OsO 4 , NMO<br />

HO<br />

6<br />

Bu 4 NI, DMF<br />

CH 2 Cl 2 HO<br />

OH<br />

OBn<br />

93%<br />

OBn<br />

225 313 314<br />

3<br />

60% (80% conv.)<br />

5:1 dr<br />

BnO<br />

HO<br />

HO<br />

OBn<br />

314<br />

Pd/C, H 2<br />

10 bar, MeOH<br />

HO<br />

HO<br />

HO<br />

OH<br />

315<br />

quant.<br />

3 J H2-H3ax = 13.5<br />

3 J H3ax-H4 = 11.0<br />

3 J H3eq-H4 = 5.0<br />

3 J H4-H5 = 11.0<br />

3 J H5-H6 = 3.0<br />

Scheme 4.37 – model dihydroxylation and assignment of relative stereochemistry<br />

4.4.3 <strong>Route</strong> B<br />

This route would be four steps shorter than the previous altrose synthesis; three<br />

protecting group manipulations, and the simultaneous reduction of the enone and<br />

oxazoline. Furthermore, since there is no available hydroxyl group during the<br />

alkylation step, lac<strong>to</strong>nisation is not possible.<br />

Ph Ph Ph Ph<br />

Ox*<br />

O<br />

NMe<br />

O<br />

NMe<br />

MeOTf, 7 hr<br />

O<br />

276<br />

OH<br />

then NaBH 4<br />

0 °C<br />

OH<br />

310<br />

OH<br />

OH<br />

78%<br />

OH<br />

1%<br />

316<br />

Scheme 4.38 – synthesis of the allylic alcohol (<strong>Route</strong> B)<br />

<strong>The</strong> alkylation-reduction sequence proceeded in good yield and with excellent<br />

diastereoselectivity, consistent with the previous enone reduction with sodium<br />

borohydride (Table 4.3). <strong>The</strong> resulting oxazolidine was treated under a range of<br />

dihydroxylation conditions.<br />

160


Chapter 4 – Synthesis of carbasugars<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

NMe<br />

O<br />

NMe<br />

O<br />

NMe<br />

O<br />

NMe<br />

OsO 4 HO<br />

HO<br />

Conditions<br />

OH<br />

HO OH<br />

OH HO<br />

OH<br />

OH<br />

O<br />

O<br />

310 311 318 319<br />

OH<br />

Time Ratio † (isolated yield / %)<br />

Entry Conditions / d 311 318 319 Conv.*<br />

a CH 2 Cl 2, Me 3 NO.H 2 O 5 39 21 15 -<br />

b CH 2 Cl 2, Me 3 NO.H 2 O 7 30 (25) 28 (25) 19 (19) 81%<br />

c CH 2 Cl 2, NMO.H 2 O 5 21 45 18 -<br />

d CH 2 Cl 2, NMO.H 2 O 7 18 (21) 18 (11) 59 (42) 100%<br />

e t-BuOH / H 2 O 9 11 (10) 14 (15) 4 (0) 40%<br />

f Ace<strong>to</strong>ne / H 2 O 9 5 (5) 38 (32) 3 (0) 58%<br />

g RD 2 8 31 40 -<br />

h Donohoe 2 hr – ‡ – – 100%<br />

* conversion given when products isolated † ratio in crude 1 H NMR, remainder is starting material<br />

‡ no product isolated, see text<br />

Table 4.6 – dihydroxylations of allylic alcohol (route B)<br />

<strong>The</strong> dihydroxylation of the allylic alcohol was generally slow and unselective (Table<br />

4.6). <strong>The</strong> most promising result was under the original conditions of Poli, using<br />

trimethylamine N-oxide as reoxidant (entries a,b), indicating almost 40% of the desired<br />

tetraol 311 by crude 1 H NMR. Unfortunately leaving the reaction for longer did not<br />

improve conversion, and the isolated yield was poor with almost equal amounts of<br />

each by-product seen. Under other dihydroxylation conditions enone 318 was the<br />

major product, which under prolonged reaction oxidised <strong>to</strong> triol 319 (entries c, d). <strong>The</strong><br />

relative stereochemistry of 319 was assigned by analogy <strong>to</strong> the dihydroxylation of the<br />

related enone 201 (section 4.2.2).<br />

Whilst unexpected, the oxidation of allylic alcohols <strong>to</strong> enones under s<strong>to</strong>ichiometric<br />

osmium tetroxide has been previously observed by Donohoe 195 who proposed it <strong>to</strong> be<br />

161


4.4 – Revised altrose synthesis<br />

indicative of a strong interaction between the allylic alcohol and osmium tetroxide.<br />

<strong>The</strong> substrate-metal interaction might be further strengthened by the presence of an<br />

internal amine which would compete with the amine ligands of the catalytic systems<br />

(N-methylmorpholine, trimethylamine or quinuclidine). Sharpless has previously<br />

shown that osmate esters are unreactive <strong>to</strong> NMO when coordinatively saturated with<br />

amines. 198<br />

Since it is postulated that it is the catalytic cycle that is being inhibited, the problem<br />

might be overcome under s<strong>to</strong>ichiometric conditions. <strong>The</strong> most notable such reaction is<br />

the application of the s<strong>to</strong>ichiometric TMEDA/osmium tetroxide by Donohoe. 199 A<br />

further advantage of this system is that it has been estimated <strong>to</strong> be 100 times more<br />

reactive than the monodentate catalytic systems previously used, although conducting<br />

the reaction at –78 °C <strong>to</strong> enhance selectivity might be expected <strong>to</strong> negate this. We<br />

would not expect <strong>to</strong> obtain tetraol 311 as the major product from this reaction as<br />

Donohoe conditions generally prefer syn-dihydroxylation.<br />

Despite rapid consumption of starting material, no products could be identified either<br />

before or after purification (Table 4.6, entry h). <strong>The</strong> reaction mixture remained rust<br />

brown after all recommended hydrolysis conditions were employed, making analysis<br />

of the reaction difficult. It is noted that osmate esters are normally detectable by 1 H<br />

NMR and TLC, and no compounds could be identified by either method. Meanwhile,<br />

enough of tetraol 311 had been isolated <strong>to</strong> investigate the forward reaction.<br />

4.4.3.a <strong>Route</strong> B: oxazolidine hydrolysis<br />

<strong>The</strong> isolated tetraol 311 and ke<strong>to</strong>ne 319 were subject <strong>to</strong> the hydrolysis conditions<br />

previously developed (Scheme 4.39). <strong>The</strong> tetraol could be seen <strong>to</strong> go <strong>to</strong> a UV-inactive<br />

product by TLC at both ambient and elevated temperatures, but upon workup no<br />

aldehyde could be seen in the crude NMR. Reaction of ke<strong>to</strong>ne 319 was slow,<br />

presumably since it lacked an available hydroxyl group <strong>to</strong> facilitate hydrolysis (section<br />

4.2.9).<br />

162


Chapter 4 – Synthesis of carbasugars<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

NMe<br />

O<br />

NMe<br />

HO<br />

HO<br />

OH<br />

311<br />

OH<br />

(CO 2 H) 2<br />

THF/H 2 O<br />

rt or<br />

50 °C<br />

no isolable<br />

products<br />

HO<br />

HO<br />

O<br />

319<br />

OH<br />

(CO 2 H) 2<br />

THF/H 2 O<br />

50 °C<br />

95:5 dr<br />

α-L-Altrose<br />

analogue<br />

Scheme 4.40 – dihydroxylation of allylic alcohol (route C)<br />

Pleasingly, the dihydroxylation proceeded cleanly with no other diastereomers<br />

observed in the crude NMR or upon purification. Optimisation of this step was<br />

deemed unnecessary since it completed the five step synthesis from diene 102b in<br />

45.3% yield. An overview of the synthesis is given in Scheme 4.58 at the end of the<br />

chapter.<br />

163


4.5 – Mannose synthesis<br />

4.5 Synthesis of a Mannose Analogue<br />

Hydrolysis of the known epoxide 309 (section 4.2.8) would give an epimer of the<br />

altrose analogue synthesised above. Regioselectivity of nucleophilic attack on<br />

oxiranes can often be predicted by considering stabilisation of a developing charge and<br />

<strong>to</strong>rsional strain in the transition state.<br />

If we consider the opening of epoxide 309 (Scheme 4.41) there is little stabilisation of<br />

a developing charge at either juncture but clear differences when we consider <strong>to</strong>rsional<br />

strain in the transition states. Nucleophilic attack of cyclohexene oxides generally<br />

proceeds through a chair-like trans-diaxial transition state, 200 whereas the regiomeric<br />

opening requires the carbocycle <strong>to</strong> go through a strained twist-boat.<br />

HO<br />

HO<br />

O<br />

H 2 O<br />

Me<br />

HO<br />

R<br />

O<br />

OH 2<br />

321<br />

twist-boat<br />

OH OH<br />

HO<br />

HO OH<br />

OH<br />

α-L-Idose<br />

analogue<br />

322<br />

OH<br />

OH<br />

309<br />

H 2 O<br />

R = i-Pr<br />

Me<br />

HO<br />

R<br />

OH 2<br />

O<br />

OH<br />

323<br />

trans-diaxial &<br />

neopentyllic<br />

OH<br />

HO<br />

HO<br />

HO OH<br />

OH<br />

α-L-Mannose<br />

analogue<br />

324<br />

Scheme 4.41 – hydrolysis of cyclohexane epoxide 309<br />

However, the example above is complicated by the presence of a quaternary centre<br />

hindering the approach of the nucleophile in the diaxial transition state 323. <strong>The</strong>se<br />

conflicting strains make it hard <strong>to</strong> predict the preferred product, and the likely result<br />

would be poor regioselectivity, as was seen in the work of Gonzalez in the synthesis of<br />

cycli<strong>to</strong>ls from (–)-quinic acid. 201<br />

164


Chapter 4 – Synthesis of carbasugars<br />

TBSO<br />

HO<br />

HO<br />

OH<br />

OH<br />

OH<br />

TFA/H 2 O HO<br />

HO<br />

O<br />

80 °C, 11 hr<br />

OH<br />

HO OH HO OH<br />

OH<br />

OH<br />

OH<br />

42% 58%<br />

325 326<br />

Scheme 4.42 – hydrolysis of an epoxycyclohexane similar <strong>to</strong> 309 201<br />

Assuming that the ground state conformation of epoxide 325 is the same as that of 309,<br />

the same choice of transition states exists; clearly these were very close in energy, with<br />

a 3:2 preference for neopentylic, trans-diaxial opening (326). <strong>The</strong> elevated<br />

temperature and prolonged time of the reaction may be indicative of the strain that had<br />

<strong>to</strong> be overcome in both transition states.<br />

This conflict of high <strong>to</strong>rsional strain in the regioisomeric transition states may be<br />

overcome if we consider the opening of the diastereomeric epoxide 327 (Scheme<br />

4.43). trans-Diaxial hydrolysis of this epoxide would instead proceed by attack at the<br />

distal centre; presenting a strong preference for the isomer with the stereocentres of α-<br />

L-mannose.<br />

O<br />

HO<br />

OH<br />

327<br />

OH<br />

H 2 O<br />

H 2 O<br />

R = i-Pr<br />

Me<br />

HO<br />

Me<br />

HO<br />

R<br />

R<br />

O<br />

trans-diaxial<br />

OH 2<br />

OH 2<br />

O<br />

OH<br />

Twist boat<br />

& neopentyllic<br />

OH<br />

OH OH<br />

HO<br />

HO OH<br />

OH<br />

α-L-Mannose<br />

analogue<br />

324<br />

HO<br />

HO<br />

HO<br />

FAVOURED<br />

HO<br />

OH<br />

α-L-Idose<br />

analogue<br />

322<br />

OH<br />

DISFAVOURED<br />

Scheme 4.43 – possible hydrolysis of a diastereomer of epoxide 309<br />

165


4.5 – Mannose synthesis<br />

It is clear that if such an epoxide could be synthesised, selective hydrolysis would be<br />

expected <strong>to</strong> yield an analogue of mannose with good regioselectivity. <strong>The</strong> next section<br />

will discuss the synthesis of the diastereomeric epoxide by employing the lac<strong>to</strong>nisation<br />

previously discovered (section 4.2.8). This approach was chosen since it explores a<br />

new method of oxazoline removal, and would complement the previous synthesis. It<br />

should be noted that it would also possible <strong>to</strong> favour anti epoxidation by making the<br />

silyl ether, 189 or by employing the Sharpless-Katsuki asymmetric epoxidation. 188<br />

4.5.1 Strategy I: Lac<strong>to</strong>nisation<br />

It was recognised that lac<strong>to</strong>nisation of diol 213 would leave only one hydrogen bond<br />

donor <strong>to</strong> direct epoxidation in the newly formed bicycle 328 (Scheme 4.44). Simple<br />

MM2 modelling indicates that whilst there is little <strong>to</strong> encumber the approach of the<br />

oxidant <strong>to</strong> either face of the alkene, the pseudo-equa<strong>to</strong>rial alcohol is well placed <strong>to</strong><br />

direct a hydrogen bonding reagent.<br />

Ox*<br />

MeOTf O<br />

[O] O<br />

O<br />

OH<br />

O<br />

O<br />

OH<br />

OH<br />

213 328 329<br />

OH<br />

Scheme 4.44 – proposed lac<strong>to</strong>nisation-epoxidation & molecular model (MM2)<br />

If successful, the resulting epoxide 329 should undergo diaxial hydrolysis <strong>to</strong> give an<br />

analogue of mannose (Scheme 4.45). Whilst it might be possible <strong>to</strong> hydrolyse both the<br />

epoxide and lac<strong>to</strong>ne in a single reaction, the resulting carboxylic acid would be<br />

extremely polar and hard <strong>to</strong> isolate, instead a reduction-hydrolysis strategy is preferred.<br />

166


Chapter 4 – Synthesis of carbasugars<br />

O<br />

Me<br />

Me<br />

i) H -<br />

HO<br />

HO<br />

O<br />

O<br />

O CO 2<br />

OH<br />

213 328<br />

OH<br />

ii) H 2 O<br />

HO<br />

OH<br />

α-L-Mannose<br />

analogue<br />

329<br />

OH<br />

Scheme 4.45 – proposed reduction-hydrolysis of lac<strong>to</strong>ne 213<br />

4.5.1.a Initial studies of lac<strong>to</strong>nisation-epoxidation strategy<br />

It was anticipated that lac<strong>to</strong>nisation could be induced under similar conditions <strong>to</strong> those<br />

found before (section 4.2.8), but that replacing the reductive quench with an aqueous<br />

one might increase yield of lac<strong>to</strong>ne and return some starting material. As before, the<br />

alkylation was left overnight, but instead of the standard methanol/THF-borohydrdride<br />

quench, aqueous ammonium chloride was added <strong>to</strong> the reagents in dichloromethane<br />

with vigorous stirring.<br />

Ox*<br />

i) MeOTf, CH 2 Cl 2<br />

16 hr<br />

O<br />

OH ii) NH 4 Cl (aq) O<br />

8 hr<br />

OH<br />

213 328<br />

OH<br />

36 %<br />

97% conv.<br />

Scheme 4.46 – lac<strong>to</strong>nisation<br />

Lac<strong>to</strong>ne 328 was isolated in a similar quantity <strong>to</strong> the previous conditions, and despite<br />

complete conversion of the oxazoline, no other products could be identified before or<br />

after purification. That similar amounts of lac<strong>to</strong>nisation were seen under reductive and<br />

aqueous quenches lends support <strong>to</strong> the conclusion that lac<strong>to</strong>nisation occurs during<br />

alkylation.<br />

Epoxidation of the resulting olefin went cleanly with no other products visible in the<br />

crude NMR (Scheme 4.47). <strong>The</strong>re was, however, a striking difference between the<br />

carbon NMR of this compound and its diastereomer 307; the carbonyl of the latter was<br />

only observable with a relaxation time of 25 seconds, whilst the carbonyl of 329 was<br />

observable with a standard relaxation time of 1 second. Since spin relaxation of 13 C<br />

nuclei is assisted by nearby pro<strong>to</strong>ns in a through-space interaction, this is explained by<br />

167


4.5 – Mannose synthesis<br />

considering the local environment in the two compounds. In lac<strong>to</strong>ne 329 methine H6<br />

is close <strong>to</strong> the carbonyl, whilst the diastereomeric lac<strong>to</strong>ne has no such available pro<strong>to</strong>n<br />

<strong>to</strong> assist relaxation; further confirming the stereochemistry of the two compounds.<br />

5s< T 1


Chapter 4 – Synthesis of carbasugars<br />

4.5.1.b Lac<strong>to</strong>nisation of cis-hydroxy oxazolines<br />

Initial experimentation had shown that the stereoselective epoxidation works well but<br />

that the lac<strong>to</strong>nisation and reduction steps need improvement. Since lac<strong>to</strong>nisation<br />

occurred in the presence of excess alkylating agent and only trace amounts of water,<br />

the rate determining step appears not <strong>to</strong> be the hydrolysis but the formation of the<br />

ortho-amide (section 4.2.8). Under these conditions lac<strong>to</strong>nisation might be improved<br />

through longer reaction times, heating, or the use of bench dichloromethane rather than<br />

that distilled over calcium hydride. However it is likely that such a method would be<br />

limited <strong>to</strong> small scale reactions, and the use of methyl trifluoromethylsulfonate at<br />

elevated temperature would increase the risk of exposure <strong>to</strong> the deadly reagent. 135,136<br />

Instead a number of alternative conditions were explored (Table 4.7).<br />

Ox*<br />

Conditions<br />

O<br />

OH<br />

O<br />

OH<br />

213 328<br />

OH<br />

Reagent Solvent Conditions 328<br />

a MeI (3 eq) CH 2 Cl 2 Δ 6 hr nr<br />

b HCl THF/H 2 O Δ 16 hr ester<br />

c Cu(OTf) 2 (1.2 eq) CH 2 Cl 2 rt 16 hr nr<br />

d Sc(OTf) 3 (1.2 eq), THF/H 2 O rt (16 hr) nr<br />

e Sc(OTf) 3 (1.2 eq), THF/H 2 O 50 °C (4 hr) 20% *<br />

* crude 1 H NMR SM:328:unknown = 2.5:1:1<br />

Table 4.7 – attempted lac<strong>to</strong>nisations<br />

Methyl iodide had previously been used <strong>to</strong> quaternise oxazolines in a similar manner <strong>to</strong><br />

methyl triflate, 202 but would be more amenable <strong>to</strong> use at elevated temperature and not<br />

as sensitive <strong>to</strong> water. Unfortunately, after prolonged reaction (entry a), only starting<br />

material was recovered.<br />

Likewise, it had previously been found that the oxazolines are quickly pro<strong>to</strong>nated in<br />

aqueous hydrochloric acid in THF <strong>to</strong> give esters (section 3.2.4), it was possible that<br />

this process might be catalysed by the formation of an ortho-amide, if not, the ester<br />

169


4.5 – Mannose synthesis<br />

which would result from oxazoline hydrolysis may itself undergo lac<strong>to</strong>nisation. When<br />

heated under these conditions (entry b) there was no sign of lac<strong>to</strong>nisation, instead only<br />

the ester was isolated. Treatment of this ester under mildly basic conditions (t-<br />

BuOH/t-BuONa) yielded trace amounts of lac<strong>to</strong>ne along with a number of unidentified<br />

products. Perchloric acid and sulfuric acid were also unsuccessful in catalysing the<br />

lac<strong>to</strong>nisation of the closely related epoxyoxazoline 216. Similarly trifluoroacetic acid<br />

has been found <strong>to</strong> catalyse the lac<strong>to</strong>nisation of oxazoline 331 at room temperature and<br />

would be worth attempting since the bisphenyl oxazolines hydrolyse <strong>to</strong> amides when<br />

treated with TFA (section 3.2.5).<br />

O<br />

N<br />

TFA, THF/H 2 O<br />

O<br />

O<br />

Ph<br />

Ph<br />

rt, 2 d<br />

OH<br />

331<br />

203<br />

Scheme 4.50 – lac<strong>to</strong>nisation of oxazolines<br />

Since the alkylating agent seemed <strong>to</strong> promote cyclisation by removing electron density<br />

from the oxazoline π-system, it was anticipated that a Lewis acid might also work.<br />

Oxazolines have been used <strong>to</strong> make copper (II) complexes which have proven <strong>to</strong> be of<br />

enormous value in asymmetric synthesis, exemplified by the Evans Copper BOX. 204<br />

In light of this, and that excess water did not seem necessary, copper (II) triflate was<br />

employed, but no reaction observed (entry c, Table 4.7). Since previous lac<strong>to</strong>nisations<br />

worked in similarly anhydrous conditions it is unlikely that the reaction failed for a<br />

lack of water, more likely is that the presence of trace water inhibited the sensitive<br />

Lewis acid.<br />

<strong>The</strong>re has been much interest in the use of lanthanide (III) triflates as water soluble,<br />

even water-activated, Lewis acids in catalytic synthesis. 205,206 In light of the above<br />

problems, these rare earth metal salts seemed like perfect reagents <strong>to</strong> catalyse the<br />

hydrolysis. Promisingly, excess scandium triflate returned a significant amount of the<br />

lac<strong>to</strong>ne, with the remaining crude material comprising mostly oxazoline starting<br />

material (entry e, Table 4.7); whilst only a small scale reaction, this result is indicative<br />

170


Chapter 4 – Synthesis of carbasugars<br />

that this strategy for hydrolysis could work. Whilst this was being pursued, another<br />

strategy was providing promising results.<br />

4.5.2 Strategy II: Cyclohexene oxides<br />

<strong>The</strong> lac<strong>to</strong>nisation strategy was appealing since hydrolysis of the resulting epoxide was<br />

expected <strong>to</strong> give good regioselectivity (Scheme 4.43). Whilst it would be possible <strong>to</strong><br />

make this diastereomeric epoxide (vide supra) initial experiments would focus on<br />

opening epoxides already in hand. A similar strategy <strong>to</strong> the final altrose synthesis may<br />

be envisaged (Scheme 4.51). <strong>The</strong> main difference being that oxidation of the allylic<br />

alcohol is directed by hydrogen bonding, and that steric encumbrance at C1 is<br />

unimportant.<br />

Ox*<br />

Ox*<br />

HO<br />

D<br />

O<br />

276<br />

a<br />

OH 97%<br />

b, 78%<br />

O<br />

OH<br />

216<br />

OH<br />

H 2 O<br />

d (i)<br />

HO<br />

HO OH<br />

OH<br />

α-L-Mannose<br />

analogue<br />

324<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

HO<br />

O<br />

N<br />

O<br />

N<br />

HO<br />

E<br />

OH<br />

310<br />

OH<br />

[O]<br />

c, 79%<br />

O<br />

OH<br />

306<br />

OH<br />

HO OH<br />

OH<br />

α-L-Idose<br />

analogue<br />

322<br />

d (ii, iii)<br />

83% 3 steps<br />

HO<br />

HO<br />

F<br />

OH<br />

312<br />

OH<br />

[O]<br />

O<br />

OH<br />

309<br />

OH<br />

H 2 O<br />

a) i) NaBH 4 , MeOH, 0 °C, 6 hr, 98% ii) mCPBA, CH 2 Cl 2 , 0 °C, 6 hr, 99%; b) MeOTf, CH 2 Cl 2 , then<br />

NaBH 4 , 0 °C, MeOH/THF, 78%; c) i) (CO 2 H) 2 , THF/H 2 O, 50 °C, 24 hr, ii) NaBH 4 , MeOH, 79% (2<br />

steps); d) i) MeOTf, CH 2 Cl 2 , then NaBH 4 , 0 °C, MeOH/THF, ii) (CO 2 H) 2 , THF/H 2 O, 50 °C 17 hr, iii)<br />

NaBH 4 , MeOH, 83% (3 steps).<br />

Scheme 4.51 – proposed synthesis of diastereomeric carbasugar<br />

171


4.5 – Mannose synthesis<br />

One clear advantage of this synthetic plan is that much of the chemistry has already<br />

been completed; the only query that remains is at which stage the oxidation and<br />

hydrolysis will prove most selective. Hydrolysis of epoxyoxazolidine 306 is not<br />

included in this synthetic plan since oxazolidine hydrolysis has proven problematic and<br />

reactions would likely be very complicated.<br />

4.5.2.a Epoxidations<br />

Epoxidation D has been shown <strong>to</strong> work very well (section 4.2.6), but requires an extra<br />

synthetic step than oxidations E and F. Furthermore, unlike the altrose synthesis,<br />

hindrance of one side of the olefin should not affect the facial selectivity, whilst having<br />

late stage intermediates in common would make the two syntheses less divergent and<br />

more amenable <strong>to</strong> future scale-up. <strong>The</strong> oxidant would again be mCPBA since it had<br />

performed excellently in the epoxidation of alkene 216.<br />

Oxidation E of oxazolidine 310 was conducted at low temperature since it was hoped<br />

that reduced temperature would favour stereoselective epoxidation whilst minimising<br />

oxidation of the tertiary amine, which often requires elevated temperatures. 171<br />

However epoxidation was accompanied by oxidation of the amine and only N-oxide<br />

332 (Scheme 4.52) was isolated. This is consistent with the observations of Ganem<br />

(Scheme 4.53). 207<br />

Ph<br />

O<br />

OH<br />

N<br />

310<br />

Ph<br />

OH<br />

mCPBA (2 eq)<br />

CH 2 Cl 2<br />

−40 °C<br />

O<br />

Ph<br />

O<br />

OH<br />

332<br />

Ph<br />

O<br />

N<br />

OH<br />

53%<br />

(CO 2 H) 2 , rt<br />

THF/H 2 O, 5 d<br />

Scheme 4.52 – epoxidation (route E)<br />

no isolable<br />

products<br />

It was thought that oxazolidine N-oxides might hydrolyse more rapidly <strong>to</strong> the aldehyde<br />

than the parent oxazolidine. Initial results were promising since after two days of mild<br />

hydrolytic conditions, an aldehyde was observed in the 1 H NMR spectrum of the crude<br />

mixture in a 1:2 ratio with starting material 332. Unfortunately, upon consumption of<br />

the oxazolidine, no aldehyde was present in the final reaction mixture (Scheme 4.52),<br />

172


Chapter 4 – Synthesis of carbasugars<br />

nor was any the desired triol 309 isolated upon reduction of this mixture with sodium<br />

borohydride.<br />

OH<br />

OH<br />

BnO<br />

NBn<br />

mCPBA (3.5 eq)<br />

CH 2 Cl 2<br />

BnO<br />

O<br />

NBn<br />

BnO<br />

OBn<br />

0 °C <strong>to</strong> rt<br />

BnO<br />

OBn<br />

O<br />

207<br />

Scheme 4.53 – N-oxidation of tertiary amines at ambient temperature<br />

Oxidation F of allylic alcohol 312, the final intermediate in the final altrose synthesis,<br />

was problematic due <strong>to</strong> its low solubility. <strong>The</strong> triol was only sparingly soluble in most<br />

non-alcoholic solvents, and although small amounts of alcohol made the triol<br />

completely soluble it was believed it would saturate the peracid with hydrogen bond<br />

donors and prevent facial discrimination. Under high dilution conditions at ambient<br />

temperature, the allylic alcohol was sparingly soluble in chloroform, but under these<br />

conditions oxidation gave no discernable products by TLC or upon workup. It was<br />

later found that whilst alcoholic solvents do destroy selectivity for the majority of<br />

hydrogen bond oxidants, they have little effect on mCPBA. 168<br />

HO<br />

HO<br />

OH<br />

OH<br />

mCPBA<br />

CHCl 3<br />

rt, 8 hr<br />

no isolable<br />

products<br />

O<br />

OH<br />

312 312<br />

OH<br />

Scheme 4.54 – epoxidation (route F)<br />

Although only single reactions had been performed, there were clear problems in both<br />

instances; oxidation E would suffer with competing oxidation of the amine, and<br />

oxidation F presented a significant practical challenge <strong>to</strong> which no solution was<br />

immediately clear. Before returning <strong>to</strong> these problems, it seemed prudent <strong>to</strong> attempt<br />

the hydrolysis of the respective epoxides which could be synthesised from<br />

epoxyoxazoline 216.<br />

173


4.5 – Mannose synthesis<br />

4.5.2.b Epoxide hydrolysis<br />

Following conditions employed in similar carbasugar syntheses, 165 epoxyoxazoline<br />

216 was heated under alkaline conditions. Whilst the reaction did not go <strong>to</strong><br />

completion, the crude mixture showed hydrolysis was occurring <strong>to</strong> give a 2:1 mixture<br />

of acylated starting material <strong>to</strong> oxazoline 333-Ac with the all trans stereochemistry of<br />

the unnatural sugar idose.<br />

O<br />

Ox*<br />

OH<br />

216<br />

OH<br />

i) THF, KOH<br />

(1M), Δ 22 hr<br />

ii) Ac 2 O,<br />

pyr., DMAP<br />

AcO<br />

AcO<br />

Ox*<br />

OAc<br />

333-Ac<br />

OAc<br />

30% conversion<br />

by 1 H NMR<br />

HO<br />

H<br />

HO<br />

O<br />

HO OH<br />

OH<br />

α-L-Idose<br />

3 J H3-H4 = 9.0<br />

3 J H4-H5 = 10.0<br />

3 J H5-H6 = 9.5<br />

Scheme 4.55 – base catalysed epoxide hydrolysis (route D)<br />

Such high regioselectivity was unexpected, especially since it requires a strained twistboat<br />

transition state. <strong>The</strong> regioselectivity suggests severe congestion around C6, and<br />

that forcing conditions will continue <strong>to</strong> be needed <strong>to</strong> promote reaction. Unfortunately<br />

the mixed acetates could not be separated, and 333-Ac was not fully characterised.<br />

Furthermore, this reaction could not be reproduced under the same or different<br />

conditions (Table 4.8).<br />

174


Chapter 4 – Synthesis of carbasugars<br />

O<br />

Ox*<br />

OH<br />

216<br />

OH<br />

Conditions<br />

X<br />

HO<br />

HO<br />

Ox*<br />

OH<br />

333<br />

OH<br />

Entry Conditions Result<br />

a KOH (1M, aq) THF, Δ 22 hr nr<br />

b KOH (3M, aq) THF, Δ 36 hr nr<br />

c KOH (3M, aq) dioxane, Δ 36 hr nr<br />

d KOH, d 6 -DMSO, rt, 2 hr nr<br />

e KOH, d 6 -DMSO, 50 °C, 1 hr no isolable product<br />

f KOH, d 6 -DMSO, 18-crown-6, rt, 2 hr no isolable product<br />

g HCl (3M) THF, Δ 24 hr polymerised<br />

h HCl (1M) THF, rt, 1 hr nr<br />

i HCl (1M) THF, rt, 18 hr polymerised<br />

j H 2 SO 4 (1M), THF, rt, 5 hr nr<br />

k H 2 SO 4 (1M), THF, rt, 28 hr polymerised<br />

m HClO 4 (1M), dioxane, rt, 28 hr 20% ester *<br />

* rest SM, see section 3.2.4<br />

Table 4.8 – attempted epoxide hydrolysis (route D)<br />

Initial work attempted <strong>to</strong> repeat the above hydrolysis using the original and more<br />

forcing conditions (entries a-c). <strong>The</strong> nucleophilicity of potassium hydroxide is<br />

enhanced by the use of DMSO 208 which solvates potassium 185 making the counter ion<br />

more reactive. At ambient temperature (entries d-f), no reaction was observed when<br />

followed by 1 H NMR, however raising the temperature caused rapid decomposition of<br />

the oxazoline ring. Similar degradation occurred when 18-crown-6 was added <strong>to</strong> the<br />

reaction at ambient temperature.<br />

Upon treatment with acid, the epoxyoxazoline rapidly turned <strong>to</strong> baseline salts (c. 10<br />

min), and reverted back <strong>to</strong> starting material upon workup. This is most likely due <strong>to</strong><br />

pro<strong>to</strong>nation of the oxazoline which has previously been shown <strong>to</strong> be susceptible <strong>to</strong> acid<br />

175


4.5 – Mannose synthesis<br />

hydrolysis (section 3.2.4). Extended reaction with aqueous sulfuric and hydrochloric<br />

acids led <strong>to</strong> polymerisation, with greater than ten times the mass of the reaction being<br />

isolated as a globular oil. Treatment with perchloric acid (entry m) caused incomplete<br />

hydrolysis <strong>to</strong> the ester, which could not be further hydrolysed.<br />

Despite the initially promising result, the reactivity of the oxazoline was dominating<br />

the reaction of 216. In light of this, the hydrolysis of the free epoxide 309 was<br />

attempted (Table 4.9).<br />

HO<br />

HO<br />

HO<br />

O<br />

OH<br />

309<br />

OH<br />

Conditions<br />

HO<br />

HO<br />

OH<br />

324<br />

OH<br />

+<br />

HO<br />

HO<br />

OH<br />

322<br />

OH<br />

Entry Conditions Result<br />

a KOH (1M, aq) THF, Δ 16 hr no isolable product<br />

b KOH, d 6 -DMSO, 50 °C, 1 hr elimination<br />

c TFA:H 2 O 1:3, rt, 16 hr nr<br />

d H 2 SO 4 (3M), THF, rt, 5 hr polymerised<br />

e HClO 4 (3M), dioxane, rt, 1 hr polymerised<br />

f HCl (3M) THF, rt, 3 hr 50% 5:1 (324:322)<br />

g HCl (3M) THF, 0 °C <strong>to</strong> rt, 8 hr 81% (324) *<br />

* no crude NMR ratio obtainable<br />

Table 4.9 – epoxide hydrolysis (route F)<br />

Hydroxide opening of the epoxide was again unsuccessful (entries a-b). <strong>The</strong> KOH-<br />

DMSO system again gave mixed oxirane products which were inseparable by<br />

chroma<strong>to</strong>graphy and only identified by similar chemical shift and couplings in the<br />

crude 1 H NMR. Further analysis of the crude mixture indicates the product of<br />

elimination at C3-C4. A range of acid conditions were also employed (entries c-g); the<br />

epoxide was unreactive under TFA-H 2 O conditions despite good precedent. 201 It is<br />

likely this is due <strong>to</strong> the poor solubility of the epoxide in water. Treatment with<br />

perchloric acid and sulfuric acid returned crude reaction mixtures with UV active<br />

products, and significant mass increase; this is again attributed <strong>to</strong> polymerisation.<br />

176


Chapter 4 – Synthesis of carbasugars<br />

Pleasingly, the epoxide reacted with hydrochloric acid at ambient temperature (Table<br />

4.9, entry f) in a clean and rapid reaction with 5:1 regioselectivity favouring the<br />

product of neopentylic, trans-diaxial opening. <strong>The</strong> relative stereochemistries of the<br />

products were assigned by vicinal couplings, but their identities were initially<br />

uncertain since their polarities were similar <strong>to</strong> that of the starting material.<br />

-<br />

Furthermore, EI mass spectroscopy showed a C 11 H 22 ClO 5 ion which was taken <strong>to</strong><br />

indicate the oxirane had undergone chloride opening <strong>to</strong> give carbocycle 335.<br />

HO<br />

HO<br />

HO<br />

O<br />

OH<br />

309<br />

OH<br />

HCl (aq), THF<br />

0 °C - rt<br />

8 hr<br />

HO<br />

HO<br />

OH<br />

324<br />

OH<br />

81%<br />

Cl<br />

HO OH<br />

OH<br />

335<br />

C 11 H 21 ClO 4<br />

13C δ/ppm<br />

CH: 75.5, 73.7<br />

70.8, 69.1<br />

CH 2 : 67.1<br />

Scheme 4.56 – final hydrolysis of epoxide<br />

δ C 51.0<br />

Cl<br />

OH<br />

Repetition of the reaction at low temperature (entry g) gave enough product for 13 C<br />

NMR showing four methine carbons above 69 ppm, significantly downfield of that<br />

expected for chloride 335 (51 ppm for 2-chloro-1-propanol 209 ). <strong>The</strong> EI+ mass<br />

spectrum confirmed that chloride had been the ionising species, and revealed that a<br />

tightly bound molecule of water might be responsible for the unexpected<br />

hydrophobicity. Unfortunately, the crystals grown from methanol-water were not of<br />

high enough quality for x-ray diffraction.<br />

4.5.2.c Discussion of epoxide hydrolysis<br />

<strong>The</strong> outcome of this final hydrolysis was surprising for three reasons. Firstly the<br />

reaction proceeded rapidly at ambient temperature, which whilst common for epoxides<br />

that develop no <strong>to</strong>rsional strain, is surprising in light of the encumbrance present (vide<br />

supra).<br />

177


4.5 – Mannose synthesis<br />

<strong>The</strong> second interesting feature is the high regioselectivity of the reaction. Whilst a<br />

diastereomeric ratio was not obtained for the final conditions, it should be greater than<br />

5:1, as none of the diastereomer was isolated. This is much more selective than the<br />

similar example from Gonzalez presented earlier (Scheme 4.42) which showed<br />

approximately 3:2 preference for a similar hydrolysis. It is possible that some of this<br />

reduced selectivity reflects the elevated temperature of the Gonzalez reaction, skewing<br />

the Bolzmann distribution. A literature survey of the hydrolysis of epoxides with<br />

adjacent quaternary centres shows that in contrast <strong>to</strong> the results above, the vast<br />

majority favour opening at the distal centre. 210<br />

<strong>The</strong> third surprise was that the regioselectivity apparently switched when changing<br />

from alkali <strong>to</strong> acid conditions (Scheme 4.57). Whilst it is often possible <strong>to</strong> change the<br />

regioselectivity of epoxide hydrolysis by changing the pH of the reaction, this requires<br />

an adjacent system <strong>to</strong> stabilise a developing positive charge. No such system exists in<br />

these two instances, yet basic hydrolysis of epoxyoxazoline 216 occurred at the distal<br />

centre (albeit as an isolated case), whilst acid hydrolysis of epoxide 309 <strong>to</strong>ok place at<br />

the proximal one. In principle, the primary alcohol of 309 might participate in the<br />

oxirane opening, but this would require a 6,5 trans-fused intermediate and result in<br />

retention of stereochemistry at C5. Since the epoxides are very similar and are<br />

expected <strong>to</strong> have similar stereoelectronic characteristics – corroborated by 13 C NMR<br />

data – the only significant change in the reaction seem <strong>to</strong> be the conditions of<br />

hydrolysis.<br />

δ C6 61.0<br />

δ C5 56.0<br />

O<br />

Ox*<br />

OH<br />

216<br />

OH<br />

THF, KOH<br />

(1M, aq),<br />

Δ 22 hr<br />

HO<br />

HO<br />

Ox*<br />

OH<br />

333<br />

OH<br />

dr: high<br />

irreproducible<br />

δ C6 61.9<br />

δ c5 58.8<br />

HO<br />

O<br />

OH<br />

309<br />

OH<br />

HCl (aq), THF<br />

0 °C - rt<br />

8 hr<br />

HO<br />

HO<br />

HO<br />

OH<br />

324<br />

OH<br />

dr >5:1<br />

Scheme 4.57– chemical shift and reactivity of the two epoxides<br />

178


Chapter 4 – Synthesis of carbasugars<br />

Acidic conditions favour epoxide attack at the centre with nearby orbitals available <strong>to</strong><br />

stabilise a developing positive charge. In these examples the only difference in<br />

available orbitals are the adjacent σ bonds which could in principle stabilise<br />

developing p-character at either C5 or C6 through hyperconjugation. However, for<br />

this <strong>to</strong> be responsible for the high selectivity, the two σ C1-C orbitals would have <strong>to</strong> be<br />

significantly more stabilising for C6 than the σ C4-H and σ C4-O are for C5. This is<br />

211<br />

unlikely since the pseudo-axial σ C4-H should equivalent <strong>to</strong> the pseudo-axial σ C6-C<br />

whilst the remaining two pseudo-equa<strong>to</strong>rial orbitals would have little overlap with an<br />

empty p-orbital.<br />

In light of this, it seems that there is no reason for such a stark, and irreproducible,<br />

change in reactivity, other than <strong>to</strong> assume that the alkaline hydrolysis of the<br />

epoxyoxazoline was spurious. Subsequent studies by Karlubíková have shown that<br />

azide opening occurs at the neopentylic position, consistent with these latter results. 66<br />

179


4.6 – Summary<br />

4.6 Summary & Future Work<br />

<strong>The</strong> synthesis of two carbasugar analogues is summarised below. <strong>The</strong> overall yields<br />

compare extremely well <strong>to</strong> the literature syntheses summarised in section 4.1, of which<br />

only six of the 104 routes had overall yields – taken from advanced intermediates or<br />

chiral pool materials – above 40%. Using a similar measure, altrose analogue 278 has<br />

been synthesised in 45% overall yield and mannose analogue 324 in 60% yield.<br />

Ox*<br />

Ox*<br />

Ox*<br />

a<br />

b<br />

OH<br />

OMe<br />

OMe<br />

O<br />

101b<br />

102b<br />

276<br />

HO<br />

HO<br />

HO<br />

d<br />

HO<br />

HO<br />

H<br />

O<br />

OH<br />

HO<br />

OH<br />

HO<br />

OH<br />

c<br />

OH<br />

OH<br />

OH<br />

312<br />

278<br />

α-L-Altrose<br />

276<br />

45.3%, 5 steps from 102b<br />

32.7%, 6 steps from 101b<br />

e, f<br />

O<br />

Ox<br />

g, h<br />

HO<br />

HO<br />

HO<br />

HO<br />

H<br />

O<br />

OH<br />

OH<br />

HO<br />

OH<br />

OH<br />

HO<br />

OH<br />

OH<br />

309<br />

324<br />

α-L-Mannose<br />

60.6%, 7 steps from 102b<br />

42.5%, 8 steps from 101b<br />

a) i-PrLi, THF, 20 min, –78 °C, then MeI, 70%; b) OsO 4 , NMO, t-BuOH then Na 2 S 2 O 5 , 93%; c)<br />

MeOTf, CH 2 Cl 2 , then NaBH 4 , 0 °C, MeOH/THF, 78%; ii) (CO 2 H) 2 , THF/H 2 O, 50 °C 24 hr, iii) NaBH 4 ,<br />

MeOH, 79% (2 steps); d) OsO 4 , quinuclidine, MeSO 2 NH 2 , K 2 CO 3 , K 3 Fe(CN) 6 , t-BuOH/H 2 O, 3 d, 79%.<br />

e) NaBH 4 , MeOH, 0 °C, 6 hr, 98%; f) mCPBA, CH 2 Cl 2 , 0 °C, 6 hr, 99%; g) i) MeOTf, CH 2 Cl 2 , then<br />

NaBH 4 , 0 °C, MeOH/THF, ii) (CO 2 H) 2 , THF/H 2 O, 50 °C 17 hr, iii) NaBH 4 , MeOH, 83% (3 steps); h)<br />

THF, HCl (aq), 0 °C rt, 8 hr, 81%.<br />

Scheme 4.58 – divergent synthesis of α-L-mannose and α-L-altrose analogues<br />

180


Chapter 4 – Synthesis of carbasugars<br />

Despite being the shorter synthesis, the mannose analogue was obtained in a<br />

significantly lower yield than the altrose analogue, largely because of two unoptimised<br />

steps; the final dihydroxylation (step d) and the oxazoline removal in which the<br />

oxazolidine was chroma<strong>to</strong>graphed which is believed have diminished the yield (step<br />

c). It might be possible <strong>to</strong> access epoxide 309 by the other routes briefly explored in<br />

section 4.5.2.a, but this is unlikely <strong>to</strong> give a significant improvement in the overall<br />

yield.<br />

4.6.1 Future work<br />

Since aminocarbasugars are more common in nature and in medicinal compounds than<br />

cycli<strong>to</strong>ls (section 4.1), this would be an interesting synthetic avenue <strong>to</strong> explore. <strong>The</strong><br />

most obvious way <strong>to</strong> adapt the current syntheses would be the azide opening of either<br />

epoxide 216 or 309 <strong>to</strong> which would be expected <strong>to</strong> proceed with the same<br />

regioselectivity as hydrolysis (vide supra) <strong>to</strong> give azidosugar 340. Hydrogenation<br />

would be preferred <strong>to</strong> Staudinger reduction since separation of triphenylphosphine<br />

oxide from aminocarbasugar 341 would prove challenging, indeed isolation of<br />

aminocarbasugars might prove significantly more challenging.<br />

HO<br />

HO<br />

HO<br />

O<br />

OH<br />

OH<br />

NaN 3 , DMF<br />

N 3<br />

HO<br />

OH<br />

OH<br />

H2 , Pd/C<br />

or PPh 3 , H 2 O<br />

H 2 N<br />

HO<br />

OH<br />

OH<br />

309<br />

340<br />

341<br />

Scheme 4.59 – divergent synthesis of α-L-mannose and α-L-altrose analogues<br />

Complete regioselectivity could be achieved by application of the Donohoe tethered<br />

aminohydroxylation (TA) reaction, which overcomes the regioselectivity problems that<br />

plague the Sharpless aminohydroxylation 212 by tethering the amine source, the<br />

carbamate. 213 <strong>The</strong> TA conditions have recently been optimised, improving the scope<br />

and yield of the reaction (Scheme 4.60). 214<br />

181


4.6 – Summary<br />

OH<br />

CDI, NH 2 OH.HCl,<br />

C 6 F 5 COCl, pyr.<br />

Et 2 O, Et 3 N<br />

O<br />

O<br />

O<br />

O C 6 F 5<br />

N<br />

O<br />

H<br />

O 1% K 2 OsO 2 (OH)<br />

NH<br />

4<br />

t-BuOH/H 2 O<br />

OH<br />

78% 98%<br />

2-<br />

HO O OH<br />

Os<br />

HO<br />

O<br />

OH<br />

VI<br />

O<br />

O<br />

H 2 O<br />

O O<br />

O<br />

Os<br />

O<br />

N<br />

O<br />

N<br />

VIII<br />

O<br />

Os<br />

O<br />

O<br />

VI<br />

214<br />

Scheme 4.60 – Donohoe tethered aminohydroxylation (TA)<br />

Attaching pentafluorobenzoate <strong>to</strong> the carbamate removes the need for the<br />

s<strong>to</strong>ichiometric t-butyl hyperchlorite re-oxidant which had caused chlorination under<br />

the previous conditions. <strong>The</strong> tethered oxidant acts as a nitrene equivalent, oxidising<br />

Os VI <strong>to</strong> form a complex that is able <strong>to</strong> stereoselectively oxidise the syn face of the<br />

allylic olefin. This could be used with allylic alcohol 213 <strong>to</strong> give carbamate 343 as<br />

shown, which should <strong>to</strong>lerate the existing conditions for oxazoline removal. 117<br />

213<br />

Ox*<br />

R<br />

O OP<br />

HN O<br />

O<br />

342<br />

OsO 4<br />

HO<br />

HN<br />

O<br />

Ox*<br />

O<br />

343<br />

OP<br />

R =<br />

O<br />

312<br />

O<br />

O<br />

O<br />

NH<br />

R<br />

OP<br />

344<br />

OP<br />

OsO 4<br />

O<br />

HN<br />

HO<br />

O<br />

H<br />

OH<br />

345<br />

OP<br />

C 6 F 5<br />

Scheme 4.61 – possible application of the TA <strong>to</strong> make aminocarbasugars<br />

Donohoe has shown this new pro<strong>to</strong>col <strong>to</strong> be effective for homoallylic alcohols,<br />

although it has only been demonstrated for acyclic terminal olefins thus far. Oxidation<br />

182


Chapter 4 – Synthesis of carbasugars<br />

of cyclic homoallylic alcohols such as 344 is unlikely <strong>to</strong> occur since it would form syn<br />

6,6 bicycle 345.<br />

Other interesting cycli<strong>to</strong>ls might be made by using different organolithium<br />

nucleophiles <strong>to</strong> introduce more interesting functional groups. Cyclohexyllithium<br />

would be expected <strong>to</strong> work similarly <strong>to</strong> isopropyllithium, allowing the synthesis of<br />

disaccharide mimics such as 346. Use of THP-Li 215 would allow access <strong>to</strong> more<br />

oxygenated analogues such as 347, whilst silicon nucleophiles could be oxidised <strong>to</strong><br />

give compounds such as 348 which resembles the inosi<strong>to</strong>l family. Fluorinated dienes<br />

102d and 102e have been synthesised in modest yield; these could offer an alternative<br />

method of synthesising alkyl fluorides from a range of commercially available aryl<br />

fluorides.<br />

HO<br />

HO<br />

HO<br />

HO<br />

HO<br />

O<br />

HO<br />

OH<br />

HO<br />

OH<br />

HO<br />

OH<br />

HO<br />

OH<br />

OH<br />

OH<br />

OH<br />

Nu = c-Hex<br />

346<br />

Nu = THP<br />

347<br />

Nu = SiMe 2 Ph<br />

348<br />

Ox*<br />

Ox*<br />

102d<br />

F<br />

F<br />

102e<br />

Scheme 4.62 – possible synthetic targets and starting materials<br />

183


184


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(176) Eames, J.; Mitchell, H. J.; Nelson, A.; O'Brien, P.; Warren, S.; Wyatt, P. J.<br />

Chem. Soc., Perkin Trans. 1 1999, 1095-1103.<br />

(177) Luche, J. L. J. Am. Chem. Soc. 1978, 100, 2226-2227.<br />

(178) Gemal, A. L.; Luche, J. L. J. Am. Chem. Soc. 1981, 103, 5454-5459.<br />

(179) Krishnamurthy, S.; Brown, H. C. J. Org. Chem. 1977, 42, 1197-201.<br />

(180) Kumamo<strong>to</strong>, T.; Tabe, N.; Yamaguchi, K.; Yagishita, H.; Iwasa, H.; Ishikawa,<br />

T. Tetrahedron 2001, 57, 2717.<br />

(181) D. J. Dixon, personal communication<br />

(182) Wigfield, D. C. Tetrahedron 1979, 35, 449.<br />

(183) Leo A. Paquette, D. C., Philip L. Fuchs and Gary Molander e-EROS<br />

Encyclopedia of Reagents for Organic Synthesis; John Wiley & Sons, Ltd.,<br />

2006.<br />

(184) Czernecki, S.; Georgoulis, C.; Provelenghiou, C. Tetrahedron Lett. 1976, 17,<br />

3535.<br />

(185) Owensby, D. A.; Parker, A. J.; Diggle, J. W. J. Am. Chem. Soc. 1974, 96, 2682-<br />

2688.<br />

(186) Wessel, H. P.; Iversen, T.; Bundle, D. R. J. Chem. Soc., Perkin Trans. 1 1985,<br />

2247-2250.<br />

(187) Henbest, H. B.; Wilson, R. A. L. J. Chem. Soc. 1957, 1958 - 1965.<br />

(188) Katsuki, T.; Sharpless, K. B. J. Am. Chem. Soc. 1980, 102, 5974-5976.<br />

(189) McKittrick, B. A.; Ganem, B. Tetrahedron Lett. 1985, 26, 4895.<br />

(190) Sharpless, K. B.; Michaelson, R. C. J. Am. Chem. Soc. 1973, 95, 6136-6137.<br />

(191) Cha, J. K.; Christ, W. J.; Kishi, Y. Tetrahedron 1984, 40, 2247.<br />

(192) Cha, J. K.; Kim, N.-S. Chem. Rev. 1995, 95, 1761-1795.<br />

(193) Evans, D. A.; Kaldor, S. W. J. Org. Chem. 1990, 55, 1698-1700.<br />

(194) In Haller & Houk, 1997, the final sentence of the results and discussion reads<br />

"<strong>The</strong> Kishi model is also valid in cyclic alkenes where the stereogenic centre is<br />

fixed in a position resembling that dictated by the 1,3-allylic strain."<br />

(195) Donohoe, T. J.; Garg, R.; Moore, P. R. Tetrahedron Lett. 1996, 37, 3407.<br />

(196) Arjona, O.; de Dios, A.; Plumet, J.; Saez, B. J. Org. Chem. 1995, 60, 4932-<br />

4935.<br />

(197) Pearlman, W. M. Tetrahedron Lett. 1967, 8, 1663.<br />

(198) Jacobsen, E. N.; Marko, I.; France, M. B.; Svendsen, J. S.; Sharpless, K. B. J.<br />

Am. Chem. Soc. 1989, 111, 737-739.<br />

(199) Donohoe, T. J.; Blades, K.; Moore, P. R.; Waring, M. J.; Winter, J. J. G.;<br />

Helliwell, M.; Newcombe, N. J.; Stemp, G. J. Org. Chem. 2002, 67, 7946-<br />

7956.<br />

(200) Fürst, A.; Plattner, P. A. Helv. Chim. Acta 1949, 32, 275-283.<br />

(201) Gonzalez, C.; Carballido, M.; Castedo, L. J. Org. Chem. 2003, 68, 2248-2255.<br />

190


References<br />

(202) Meyers, A. I.; Temple, D. L.; Nolen, R. L.; Mihelich, E. D. J. Org. Chem.<br />

1974, 39, 2778-2783.<br />

(203) Kurosaki, Y.; Fukuda, T.; Iwao, M. Tetrahedron 2005, 61, 3289.<br />

(204) Evans, D. A.; Kozlowski, M. C.; Murry, J. A.; Burgey, C. S.; Campos, K. R.;<br />

Connell, B. T.; Staples, R. J. J. Am. Chem. Soc. 1999, 121, 669-685.<br />

(205) Xie, W.; Jin, Y.; Wang, P. ChemTech 1999, 23-29.<br />

(206) Kobayashi, S.; Manabe, K. Acc. Chem. Res. 2002, 35, 209-217.<br />

(207) Liotta, L. J.; Lee, J.; Ganem, B. Tetrahedron 1991, 47, 2433.<br />

(208) Berti, G.; Macchia, B.; Macchia, F. Tetrahedron Lett. 1965, 6, 3421.<br />

(209) (AIST), N. I. A. I. S. a. T.; Vol. 2008.<br />

(210) Scifinder 2006 search of carbocyclic epoxides without adjacent π-systems<br />

returned 50 reactions, of which 2 showed preference for opening at the<br />

neopentylic centre. This survey did not consider the nature of the ground or<br />

transition states, but it is assumed that a significant proportion will have<br />

required a twist boat transition state <strong>to</strong> avoid neopentylic attack<br />

(211) Alabugin, I. V.; Manoharan, M. J. Org. Chem. 2004, 69, 9011-9024.<br />

(212) Bodkin, J. A.; McLeod, M. D. J. Chem. Soc., Perkin Trans. 1 2002, 2733-2746.<br />

(213) Donohoe, T. J.; Johnson, P. D.; Cowley, A.; Keenan, M. J. Am. Chem. Soc.<br />

2002, 124, 12934-12935.<br />

(214) Donohoe, T. J.; Bataille, C. J. R.; Gattrell, W.; Kloesges, J.; Rossignol, E. Org.<br />

Lett. 2007, 9, 1725-1728.<br />

(215) Cohen, T.; Matz, J. R. J. Am. Chem. Soc. 1980, 102, 6900-2.<br />

191


References<br />

192


Experimental section<br />

Chapter 5 – Experimental Section<br />

5.1 General<br />

NMR spectra were recorded on a Varian XL 300 or Bruker Ultrashield 500<br />

spectrometers. <strong>The</strong> chemical shifts (δ) are reported in ppm downfield of<br />

trimethylsilane and coupling constants (J) reported in hertz and rounded <strong>to</strong> 0.5 Hz.<br />

Splitting patterns are abbreviated as follows: singlet (s), doublet (d), triplet (t), quartet<br />

(q), quintet (qn), septet (p), octet (oct), mulitiplet (m), broad (br), or a combination of<br />

these. An asterisk, * denotes the signal disappears upon a mixture with D 2 O or<br />

CD 3 OD. Solvents were used as internal standard when assigning NMR spectra (δ H :<br />

CDCl 3 7.27 ppm;δ C : CDCl 3 77.0 ppm; δ H : DMSO-d 6 2.50 ppm; δ C : DMSO-d 6 39.4<br />

ppm; δ H : CD 3 OD 3.31 ppm; δ C : CD 3 OD 49.0 ppm; δ H : C 6 D 6 7.15 ppm; δ H : D 2 O 4.79<br />

ppm). Coupling constants were calculated using Mestre-C 4.8.6 software, 1 and<br />

complicated couplings simulated. 2 Structural assignment of NMR signals is based on<br />

chemical shift, integration, coupling pattern and COSY, DEPT and HMQC NMR<br />

experiments when necessary.<br />

Low and high resolution mass spectra were recorded by staff at the University of<br />

Manchester. EI and CI spectra were recorded on a Fisons VG Trio 2000; and high<br />

resolution mass spectra (HRMS) were recorded on a Kra<strong>to</strong>s Concept-IS mass<br />

spectrometer, and are accurate <strong>to</strong> ± 0.001. Infrared spectra were recorded as on a Ati<br />

Matson Genesis Series FTIR spectrometer as a film on a sodium chloride plate.<br />

Absorptions reported are sharp and strong unless otherwise stated as broad (br),<br />

medium (m), or weak (w), only absorption maxima of interest are reported.<br />

Microanalysis was carried out using Carlo-Erba au<strong>to</strong>matic analyser by members of<br />

staff of the University of Manchester. Melting points (Mpt) were determined on a<br />

GallenKamp apparatus and are uncorrected. Optical rotation measurements were taken<br />

on a AA-100 polarimeter with the solvent, concentration and sample temperature as<br />

stated.<br />

Thin layer chroma<strong>to</strong>graphy (TLC) was performed using commercially available precoated<br />

plates (Macherey-Nagel alugram. Sil G/ UV254 ) and visualised with UV light at<br />

193


Experimental section<br />

254nm, dodecamolybdophosphoric acid (PMA) dip, or over iodine.<br />

chroma<strong>to</strong>graphy was carried out using Fluorochem Davilsil 40-63u 60 Å.<br />

Flash<br />

All reactions were conducted under atmospheric conditions unless otherwise stated.<br />

Where a nitrogen atmosphere is employed, oven-dried glassware was used, and<br />

immediately purged under vacuum before being backfilled with nitrogen whilst still<br />

hot. Microwave reactions were conducted in a Biotage Initia<strong>to</strong>r synthesis system.<br />

Tetrahydrofuran (THF) and diethylether were distilled under nitrogen from sodium,<br />

using a benzophenone indica<strong>to</strong>r. Dichloromethane and <strong>to</strong>luene were obtained by<br />

distillation from calcium hydride under nitrogen. Triethylamine was distilled from and<br />

s<strong>to</strong>red over potassium hydroxide. Anhydrous dioxane, methanol and<br />

dimethylformamide were used as purchased from Sigma-Aldrich. Water was used as<br />

supplied by United Utilities. Anhydrous dimethylhexahydro-2-pyrimidinone (DMPU)<br />

was used as supplied by Fluka over molecular sieves (product number 41661); methyl<br />

trifluoromethanesulfonate was used as supplied from Fluka (product number 91736).<br />

Petrol refers <strong>to</strong> the fraction of light petroleum ether boiling between 40-65 °C. All<br />

other solvents and commercially obtained reagents were used as received or purified<br />

using standard procedures. Isopropyllithium was obtained as a solution (c. 0.7 M) in<br />

pentane, s-butyllithium was obtained as a solution (c. 1.3 M) in cyclohexane and n-<br />

butyllithium was obtained as a solution (c. 2.5 M) in cyclohexane. All organolithium<br />

solutions were titrated prior <strong>to</strong> use against a stirred solution of diphenylacetic acid in<br />

THF at 0 °C.<br />

Numbering conventions in the main body and experimental sections are:<br />

General Procedure 1: Amide synthesis<br />

<strong>The</strong> acyl chloride (1.0 eq) in CH 2 Cl 2 (2 cm 3 /mmol) was added drop wise over a period<br />

of 2 hr <strong>to</strong> a stirred solution of the commercially available amine (1.2 eq) in CH 2 Cl 2 (5<br />

cm 3 /mmol) and Et 3 N (2 eq) at 0 °C under a nitrogen atmosphere. <strong>The</strong> white emulsion<br />

194


Experimental section<br />

was triturated with water (2 x reaction volume), filtered, triturated with ace<strong>to</strong>ne (2 x<br />

reaction volume), filtered and triturated with EtOAc (1 x reaction volume). <strong>The</strong><br />

combined washes were reduced under vacuum, transferred <strong>to</strong> a separating funnel, the<br />

aqueous phase acidified, washed with EtOAc (3 washes, each 2 x reaction volume) and<br />

the organic washes reduced under vacuum <strong>to</strong> give the amide as a white powder which<br />

was combined with the residue from the filtration.<br />

General Procedure 2: Oxazoline synthesis from aryl amide<br />

Adapted from the method of Linclau, 3 diisopropylcarbodiimide (DIC, 1.0 eq) was<br />

added <strong>to</strong> a solution of the amide (1.0 eq) and Cu(OTf) 2 (0.06 eq) in cyclic ether (3<br />

cm 3 /mmol) under a nitrogen atmosphere. When heated under reflux, dioxane was used<br />

as solvent, and refluxed for the stated time. When heated under microwave irradiation,<br />

THF was used and the reaction conducted in a closed vial at the stated temperature for<br />

the stated time. Crude reaction mixture was filtered with EtOAc, concentrated under<br />

vacuum, and purified by flash chroma<strong>to</strong>graphy.<br />

General Procedure 3: Preparation of oxazolines from aryl amide and α-amino<br />

alcohol<br />

Adapted from the method of Meyers 4 <strong>to</strong> a stirred solution of benzamide (1 eq)<br />

dissolved in anhydrous CH 2 Cl 2 (10 cm 3 /mmol) was added triethyloxonium<br />

tetrafluoroborate (1.2 eq) under an atmosphere of nitrogen. After being stirred at room<br />

temperature for 16 hr, amino alcohol was added (1.3 eq), and solution brought <strong>to</strong> reflux<br />

for 16 hr. Upon cooling the mixture was washed with water, extracted with CH 2 Cl 2 ,<br />

dried over anhydrous Na 2 SO 4 , and concentrated under vacuum <strong>to</strong> give a residue which<br />

was purified by flash chroma<strong>to</strong>graphy.<br />

General Procedure 4: Nucleophilic Addition <strong>to</strong> Aryl Oxazolines<br />

<strong>The</strong> organolithium was added drop wise <strong>to</strong> a stirred solution of oxazoline in the stated<br />

dry solvent (0.05 mmol/cm 3 ) and co-solvent at –78 °C under a nitrogen atmosphere.<br />

After the stated time, the electrophile was added and the reaction mixture allowed <strong>to</strong><br />

warm <strong>to</strong> ambient temperature before addition of excess methanol. <strong>The</strong> reaction<br />

mixture was reduced under vacuum and passed through a silica plug (1:1 EtOAc:<br />

petrol) and solvent removed before purification by flash chroma<strong>to</strong>graphy.<br />

195


Experimental section<br />

General Procedure 5: Modified Upjohn Dihydroxylation<br />

Adapted from the methods of the Upjohn Company 5 and Nelson 6 , osmium tetroxide<br />

(0.01 eq, 2.5% solution w/w in t-BuOH) was added <strong>to</strong> a vigorously stirred solution of<br />

the olefin (1 eq) and N-methylmorpholine N-oxide (2 eq, NMO) in the stated solvent,<br />

and the reaction moni<strong>to</strong>red by TLC. When judged complete, an aqueous solution of<br />

sodium sulfite or sodium metabisulfite (c. 5 eq) was added <strong>to</strong> the solution and stirred<br />

for 2 hr, all solvent removed under vacuum, and the resulting emulsion dried on<strong>to</strong><br />

celite before being passed through a silica plug (EtOAc), and solvent again removed<br />

under vacuum, before final purification by flash chroma<strong>to</strong>graphy.<br />

General Procedure 6: Oxazoline alkylation-reduction<br />

Adapted from the method of Meyers 7 methyl trifluoromethanesulfonate (2.0 eq) was<br />

added drop wise <strong>to</strong> a stirred solution of oxazoline in CH 2 Cl 2 (0.1M) under a nitrogen<br />

atmosphere at room temperature. After the stated time, the reaction was cooled <strong>to</strong> 0 °C<br />

and a cooled solution of sodium borohydride (2 eq) in dry THF-methanol (4:1) was<br />

added over 10 min, resulting in a white foam. <strong>The</strong> reaction was warmed <strong>to</strong> room<br />

temperature, and ammonium chloride (1 x reaction volume) was added and solvent<br />

removed under vacuum. <strong>The</strong> reaction mixture was extracted with CH 2 Cl 2, dried over<br />

anhydrous Na 2 SO 4 and concentrated under vacuum <strong>to</strong> give the crude oxazolidine.<br />

General Procedure 7: Oxazolidine hydrolysis-reduction<br />

Adapted from the method of Meyers 7 oxalic acid (5 eq) was added <strong>to</strong> a solution of<br />

oxazolidine in 4:1 THF:water (0.1M) and stirred at the stated temperature. When<br />

judged complete by TLC, the solvent was removed, the aqueous layer washed with<br />

EtOAc and the combined organic phases dried over anhydrous MgSO 4 . <strong>The</strong> resulting<br />

aldehyde was dissolved in methanol (0.1M), cooled <strong>to</strong> 0 °C and sodium borohydride (2<br />

eq) added in a single portion. When judged complete by TLC, acetic acid was added<br />

until effervescence ceased and the solvent removed under vacuum. <strong>The</strong> resultant oil<br />

was partitioned between water and EtOAc, and the aqueous layer washed with EtOAc<br />

until no further organic compound was extracted (TLC). <strong>The</strong> combined organic<br />

washes were dried over anhydrous MgSO 4 and solvent removed under vacuum <strong>to</strong> give<br />

the crude alcohol.<br />

196


Experimental for chapter 2<br />

5.2 Experimental Procedures for Chapter 2<br />

Synthesis of (4R,5R)-2-((1S,6R)-6-isopropyl-1-methylcyclohexa-2,4-dienyl)-4,5-<br />

diphenyloxazoline (102a)<br />

Ph<br />

O<br />

N<br />

Ph<br />

i) i-PrLi (1.5 eq), DMPU (6 eq)<br />

-78 °C, 30 min<br />

ii) MeI<br />

Ph<br />

6<br />

5<br />

O<br />

1<br />

4<br />

N<br />

Ph<br />

Me<br />

2<br />

3<br />

+<br />

Ph<br />

6<br />

5<br />

O<br />

4<br />

1<br />

N<br />

102a 103a<br />

General procedure 4 was used employing oxazoline 101a (130 mg, 0.43 mmol) i-PrLi<br />

(0.65 mmol in pentane), DMPU (0.31 cm 3 , 6 eq) and methyl iodide (0.1 cm 3 ) quench<br />

after 30 min. Flash chroma<strong>to</strong>graphy (19:1 petrol:EtOAc) yielded, diene 102a (109 mg,<br />

70%) as clear needles, and inseparable oxazolines 101a and 103a (24 mg, 2:1 ratio).<br />

Ph<br />

2<br />

3<br />

102a R f : 0.41 (4:1 petrol:EtOAc); Mpt: 108-110 ºC (EtOAc); [α] 23 D : –296 (c = 1.0,<br />

EtOH); MS m/z (CI+): 358 (100%, MH + ), 359 (19%, (M+1)H + ); IR ν max (film)/cm -1 :<br />

2958 (m, C–H), 1660 (C=N), 1495, 1453, 1257; Microanalysis: % found (% calc’d for<br />

C 25 H 27 NO) C, 83.52 (83.99); H, 7.59 (7.61); N, 3.90 (3.92); 1 H-NMR (CDCl 3 , 300<br />

MHz) δ 7.48-7.20 (m, 10H, Ph), 6.34 (d, 1H, J 10.0, H6), 6.14 (dd, 1H, J 5.0, 9.5, H4),<br />

5.91 (dd, 1H, J 10.0, 5.0, 1.0, H5), 5.74 (dd, 1H, J 9.5, 6.0, H3), 5.22 (d, 1H, J 9.0,<br />

OCHPh), 5.06 (d, 1H, J 9.0, NCHPh), 2.53-2.51 (m, 1H, H2), 2.08-2.04 (m, 1H,<br />

CHMe 2 ), 1.55 (s, 3H, Me), 1.06 (d, 3H, J 7.0, CHMe A Me B ), 0.98 (d, 3H, J 7.0,<br />

CHMe A Me B ); 13 C-NMR (CDCl 3 , 75 MHz) δ 171.4 (C=N), 141.9 (ipso-Ph), 140.4<br />

(ipso-Ph), 132.5 (C6), 128.8, 128.7, 128.3, 127.5, 126.7, 125.7 (Ph), 124.4, 123.8,<br />

121.5 (C3-C5), 88.9 (CHOPh), 78.8 (CHNPh), 47.2 (C2), 41.3 (C1), 31.5 (CHMe 2 ),<br />

25.6 (CHMe A Me B ), 21.1 (CHMe A Me B ), 17.0 (Me).<br />

103a R f : 0.45 (4:1 petrol:EtOAc); MS m/z (CI+): 314 (100%, MH + ), 315 (22%,<br />

(M+1)H + ) 1 H-NMR (CDCl 3 , 300 MHz) δ 8.01 (d, 1H, J 7.5, H6), 7.45-7.22 (m, 10H,<br />

Ar), 5.34 (d, 1H, J 7.5, OCHPh), 5.28 (d, 1H, J 7.5, NCHPh), 2.73 (s, 3H, Me).<br />

197


Experimental for chapter 2<br />

Synthesis of (4R,5R)-2-((1S,6R)-6-sec-butyl-1-methylcyclohexa-2,4-dienyl)-4,5-<br />

diphenyloxazoline (102a’)<br />

Ph<br />

O<br />

N<br />

Ph<br />

i) s-BuLi (1.5 eq), DMPU (15 eq)<br />

-78 °C, 30 min<br />

ii) MeI<br />

Ph<br />

O<br />

6<br />

5<br />

N<br />

Ph<br />

7<br />

1<br />

2<br />

3<br />

4<br />

102a'<br />

8<br />

9<br />

11<br />

10<br />

Ph<br />

O<br />

6<br />

5<br />

4<br />

1<br />

N<br />

103a<br />

General procedure 4 was used employing oxazoline 101a (128 mg, 0.43 mmol) s-BuLi<br />

(0.64 mmol in hexane), DMPU (1.00 cm 3 , 13 eq) and methyl iodide quench after 30<br />

min. Flash chroma<strong>to</strong>graphy (19:1 petrol:EtOAc) yielded, dienes 102a’ (128 mg, 81%,<br />

inseparable) as white needles, and oxazolines 103a and starting material (11 mg, 10:1<br />

ratio, inseparable) as a clear oil.<br />

Ph<br />

2<br />

3<br />

102a’ R f : 0.58 (4:1 petrol:EtOAc); MS: m/z (CI+): 372 (100%, MH + ), 373 (29%,<br />

(M+1)H + ); IR: ν max (film)/cm -1 : 2958, 1737, 1659 (C=N), 1494, 1267; Microanalysis:<br />

% found (% calc’d for C 26 H 29 NO) C, 83.27 (84.06); H, 7.90 (7.87); N, 3.78 (3.77); 1 H-<br />

NMR (major diastereomer): (CDCl 3 , 300 MHz) δ 7.45-7.22 (m, 10H, Ar), 6.35 (dd,<br />

1H, J 10.0, 1.0, H6), 6.10-6.05 (m, 1H, H4), 5.86 (ddd, 1H, J 10.5, 5.0, 1.0, H5), 5.67-<br />

5.61 (m, 1H, H3), 5.22 (d, 1H, J 6.0, OCHPh), 5.06 (d, 1H, J 6.0, NCHPh), 2.65-2.61<br />

(m, 1H, H2), 1.76-1.67 (m, 1H, H9), 1.55 (s, 3H, H7), 1.46-1.18 (m, 2H, H10), 1.05 (d,<br />

3H, J 7.0, H8), 0.93 (m, 3H, H11); 13 C-NMR: (CDCl 3 , 75 MHz) δ 171.5 (C=N), 141.9<br />

(ipso-Ph), 140.5 (ipso-Ph), 132.7, 128.8, 128.7, 128.3, 127.6, 126.7, 125.1, 125.7,<br />

124.3, 123.9, 121.6 (Ph and C3 <strong>to</strong> C6), 88.9 (OCHPh), 78.9 (NCHPh), 45.3 (C2), 41.1<br />

(C1), 38.8 (C9), 27.5 (C10), 25.6 (C8), 14.7 (C7), 12.5 (C11).<br />

103a see previous page<br />

198


Experimental for chapter 2<br />

Synthesis of (4R,5R)-2-((1S,6R)-6-isopropyl-4-methoxy-1-methylcyclohexa-2,4-<br />

dienyl)-4,5-diphenyloxazoline (102b)<br />

Ph Ph<br />

O N<br />

i) i-PrLi (1.5 eq), DMPU (6 eq)<br />

ii) MeI<br />

OMe<br />

Ph Ph Ph Ph<br />

O N O N<br />

1<br />

6<br />

2<br />

5 3<br />

4<br />

+<br />

1<br />

6<br />

2<br />

5<br />

3<br />

4<br />

OMe<br />

OMe<br />

102b 103b<br />

General procedure 4 was used employing oxazoline 101b (2.00 g, 6.08 mmol) i-PrLi<br />

(18.2 mmol in pentane), DMPU (4.41 cm 3 , 36.4 mmol) and methyl iodide (0.76 cm 3 ,<br />

12.1 mmol) quench after 10 min. Flash chroma<strong>to</strong>graphy (19:1 <strong>to</strong> 4:1 petrol:EtOAc)<br />

yielded starting material (110 mg, 6%), oxazoline 103b (370 mg, 18%) as a clear oil<br />

and, after recrystallisation from diethyl ether, diene 102b (1.64 g, 70%) as colourless<br />

clear cubes.<br />

102b R f : 0.60 (4:1 petrol:EtOAc); Mpt: 113-117 °C (<strong>to</strong>luene/hexane), 108-110 °C<br />

(Et 2 O); [α] 24 D : –115 (c = 0.5, MeOH); MS m/z (CI+): 388 (100%, MH + ), 389 (29%,<br />

(M+1)H + ); HRMS (ESI+) m/z found 388.2270 (MH calcd. 388.2271); Microanalysis:<br />

% found (% calc’d for C 26 H 29 NO 2 ) C 80.42, (80.59); H, 7.76 (7.54); N, 3.56 (3.61); IR<br />

ν max (film)/cm -1 : 2957 (CH), 1661 (C=N), 1453, 1220, 1087; 1 H-NMR (CDCl 3 , 300<br />

MHz) δ 7.46-7.18 (m, 10H, Ph), 6.43 (d, 1H, J 10.0, H5), 5.74 (dd, 1H, J 10.0, 2.0,<br />

H6), 5.22 (d, 1H, J 5.0, HCO), 5.06 (d, 1H, J 5.0, HCN), 4.53 (dd, 1H, J 6.5, 2.0, H3),<br />

3.62 (s, 3H, OMe), 2.59 (ddd, 1H, J 6.5, 3.5, 1.0, H2), 2.08-1.96 (m, 1H, CHMe 2 ), 1.57<br />

(s, 3H, Me), 1.00 (d, 3H, J 6.5, CHMe a Me b ), 0.96 (d, 3H, J 6.5, CHMe a Me b ); 13 C-<br />

NMR (CDCl 3 , 125 MHz) δ 171.2 (C=N), 153.1 (C4), 141.9, 140.3 (ipso-Ph), 135.0<br />

(C5), 128.9 (meta-Ph), 128.7 (meta-Ph), 128.3 (para-Ph), 127.6 (para-Ph), 126.7<br />

(ortho-Ph), 125.7 (ortho-Ph), 121.6 (C6), 89.0 (COPh), 88.4 (C3), 78.8 (HCN), 54.2<br />

(OMe), 46.8 (C2), 41.9 (C1), 31.7 (CMe 2 ), 25.8 (CMe), 21.2 (CMe a Me b ), 17.0<br />

(CMe a Me b ).<br />

103b R f : 0.50 (4:1 petrol:EtOAc); [α] D 22 : –44 (c = 1.0, EtOH); MS m/z (CI+): 344<br />

(100%, MH + ), 345 (22%, (M+1)H + ); HRMS (ESI+) m/z found 344.1645 (MH calcd.<br />

344.1645); IR ν max (film)/cm -1 : 2927 (m, C-H), 1637 (C=N), 1605, 1247; 1 H-NMR<br />

199


Experimental for chapter 2<br />

(CDCl 3 , 300 MHz) δ 8.00 (d, 1H, J 8.5, H6), 7.46-7.28 (m, 10H, Ph), 6.86-6.78 (m,<br />

2H, H3, H5), 5.31 (d, 1H, J 7.5, CHO), 5.26 (d, 1H, J 7.5, CHN), 3.86 (s, 3H, OMe),<br />

2.73 (s, 3H, CMe); 13 C-NMR (CDCl 3 , 125 MHz) δ 164.7 (C=N), 161.3 (C4), 142.5<br />

(C2), 141.7 (ipso-Ph), 140.9 (ipso-Ph), 132.0, 128.9, 128.8, 128.3, 127.6, 126.6, 125.7,<br />

119.2, 116.8, 110.9 (Ar), 87.8 (COPh), 79.3 (CNPh), 55.3 (OMe), 22.7 (Me).<br />

Synthesis of (4R,5R)-2-((1S,6R)-6-sec-butyl-4-methoxy-1-methylcyclohexa-2,4-<br />

dienyl)-4,5-diphenyloxazoline (102b’)<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

i) s-BuLi (3 eq), DMPU (6 eq)<br />

-78 °C, 10 min<br />

ii) MeI<br />

O<br />

1<br />

6<br />

5<br />

N<br />

7<br />

2<br />

3<br />

4<br />

8<br />

9<br />

10<br />

11<br />

+<br />

O<br />

N<br />

OMe<br />

OMe<br />

dr 7:2<br />

OMe<br />

102b'<br />

103b'<br />

General procedure 2 was used employing oxazoline 101b (100 mg, 0.30 mmol) s-BuLi<br />

(0.90 mmol in hexanes), DMPU (0.22 cm 3 , 36.4 mmol) and methyl iodide (0.1 cm 3 )<br />

quench after 10 min. Flash chroma<strong>to</strong>graphy (49:1 <strong>to</strong> 4:1 petrol:EtOAc) yielded<br />

starting material (5 mg, 5%) and oxazolines 102b’ and 103b’ (94 mg, 78%, 9:1<br />

mixture) as a clear oil.<br />

R f : 0.29 (9:1, petrol:EtOAc); [α] 22 D : –104 (c = 1.0, CHCl 3 ); MS m/z (CI+) 402 (100%,<br />

MH + ), 403 (27%, [(M+1)H] + ); HRMS: found 402.2431, MH requires 402.2428; IR<br />

ν max (film)/cm⎯¹ 2959 (m), 1661 (C=N), 1452 (m), 1215, 1173 (m), 1086; ¹H-NMR<br />

(major compound) (CDCl 3 , 500 MHz) δ 7.42-7.28 (m, 8H, Ph), 7.24-7.20 (m, 2H, Ph),<br />

6.43 (d, 1H, J 10.0, H6), 5.74 (dd, 1H, J 10.0, 2.0, H5), 5.22 (d, 1H, J 8.5, CHOPh),<br />

5.05 (d, 1H, J 8.5, CHNPh), 4.47 (dd, 1H, J 6.5, 2.0, H3), 3.61 (s, 3H, OMe), 2.73-<br />

2.68 (m, 1H, H2), 1.71-1.64 (m, 1H, H9), 1.57 (s, 3H, H7), 1.42-1.32 (m, 1H, H10),<br />

1.28-1.20 (m, 1H, H10’), 0.99 (d, 3H, J 6.5, H8), 0.95-0.90 (m, 3H, H11); ¹³C-NMR<br />

(CDCl 3 , 125 MHz) δ 171.2 (C=N), 153.0 (C4), 141.9 (ipso-Ph), 140.4 (ipso-Ph), 135.1<br />

(C5), 128.7, 128.7, 127.6, 126.7, 125.7 (Ph), 121.7 (C6), 89.0, 88.6 (CHOPh, C3), 78.9<br />

(CHNPh), 54.2 (OMe), 44.8 (C2), 41.7 (C1), 39.0 (C9), 27.6 (C10), 25.8 (C7), 14.8,<br />

12.4 (C8, C11).<br />

200


Experimental for chapter 2<br />

Synthesis of (4R*,5R*)-2-((R*)-6-isopropyl-4-methoxycyclohexa-1,4-dienyl)-4,5-<br />

diphenyloxazoline (102γ) & (4R*,5R*)-2-((R*)-6-isopropyl-4-methoxycyclohexa-<br />

1,3-dienyl)-4,5-diphenyloxazoline (102ε)<br />

Ph<br />

O<br />

N<br />

OMe<br />

Ph<br />

i) i-PrLi (3 eq), DMPU (6eq)<br />

PhMe, −78°C, 20 min<br />

ii) MeOH<br />

Ph<br />

6<br />

5<br />

O<br />

1<br />

4<br />

N<br />

Ph<br />

2<br />

3<br />

Ph<br />

E<br />

O<br />

F<br />

A<br />

D<br />

OMe<br />

OMe<br />

OMe<br />

102γ 102ε 116b<br />

General procedure 4 was used employing oxazoline 101b (200 mg, 0.61 mmol) i-PrLi<br />

(1.82 mmol in pentane), DMPU (0.44 cm 3 , 3.66 mmol) in <strong>to</strong>luene, and a methanol<br />

(0.12 cm 3 3.04 mmol) quench after 5 min. Flash chroma<strong>to</strong>graphy (19:1 petrol:EtOAc)<br />

yielded diene 102γ (68 mg, 32%), as a colourless oil, diene 102ε and rearomatised<br />

adduct 116b (50 mg, 5:1 ratio), and starting material (58 mg, 29%) as colourless oils.<br />

N<br />

Ph<br />

B<br />

C<br />

Ph<br />

O<br />

Z<br />

Y<br />

U<br />

X<br />

N<br />

Ph<br />

V<br />

W<br />

102γ R f : 0.26 (9:1 petrol:EtOAc); MS m/z (CI+): 374 (100%, MH + ), 375 (26%,<br />

(M+1)H + ); HRMS (ESI+) m/z found 374.2123 (MH calcd. 374.2215); IR<br />

ν max (film)/cm -1 : 2950 (C-H), 1688 (C=N), 1618 (C=C), 1453 (m), 1217, 1168; 1 H-<br />

NMR (CDCl 3 , 300 MHz) δ 7.44-7.20 (m, 10H, Ph), 6.89 (dd, 1H, J 5.0, 3.0, H6), 5.22<br />

(d, 1H, J 7.0, CHO), 5.11 (d, 1H, J 7.0, CHN), 4.73 (dd, 1H, J 5.0, 2.0, H3), 3.63 (s,<br />

3H, OMe), 3.57 (m, 1H, H2), 2.99 (dm, 1H, J 22.5, H5 a ), 2.85 (dt, 1H, J 22.5, 5.0,<br />

H5 b ), 2.41 (pd, 1H, J 7.0, 2.5, CHMe 2 ), 1.03 (d, 3H, J 7.0, CHMe a Me b ), 0.76 (d, 3H, J<br />

7.0, CHMe a Me b ); 13 C-NMR (CDCl 3 , 125 MHz) δ 163.8 (C=N), 153.3 (C4), 142.1<br />

(ipso-Ph), 140.8 (ipso-Ph), 132.6 (C6), 129.0 (C1), 128.8 (meta-Ph), 128.7 (meta-Ph),<br />

128.2 (para-Ph), 127.6 (para-Ph), 126.6 (ortho-Ph), 125.4 (ortho-Ph), 91.1 (C3), 88.0<br />

(CHO), 79.0 (CHN), 54.2 (OMe), 42.0 (C2), 31.5 (CHMe 2 ), 30.0 (C5), 20.8<br />

(CHMe a Me b ), 16.1 (CHMe a Me b ).<br />

5:1 mixture 102ε:116b R f : 0.44 (4:1 petrol:EtOAc); HRMS: found 374.2115, MH<br />

requires 374.2115; ¹H-NMR (CDCl 3 , 400 MHz) δ 7.91 (d, 1H, J 9.0, Hz), 7.42-7.22<br />

(m, 10H, Ph), 7.04 (d, 1H, J 6, H f ), 6.97 (d, 1H, J 3.0, H w ), 6.77 (dd, 1H, J 9.0, 3.0,<br />

H y ), 5.30 (d, 1H, J 8.0, CHOPh Min ), 5.25 (d, 1H, J 8.0, CHNPh Min ), 5.20 (d, 1H, J 8.0,<br />

CHOPh Maj ), 5.07-5.02 (m, 2H, CHNPh Maj , H e ), 4.22 (p, 1H, J 7.0, CHMe 2Min ), 3.86 (s,<br />

201


Experimental for chapter 2<br />

3H, OMe Min ), 3.65 (s, 3H, OMe Maj ), 2.90-2.85 (m, 1H, H b ), 2.76 (ddd, 1H, J 17.0, 9.0,<br />

2.0, H cax ), 2.35 (d, 1H, J 17.0, H ceq ), 2.07 (p, 1H, J 7.5, CHMe 2Maj ), 1.28 (d, 6H, J 7.0,<br />

CHMe 2Min ), 0.99 (d, 3H, J 7.5, CHMe 2Maj ), 0.92 (d, 3H, J 7.5, CHMe 2Maj ).<br />

Synthesis of (4R,5R)- 2-((1S,6S)-6-isopropyl-5-methoxy-1-methylcyclohexa-2,4-<br />

dienyl)-4,5-diphenyloxazoline (102c)<br />

Ph<br />

O<br />

N<br />

Ph<br />

i) i-PrLi (1.5 eq.), DMPU (6eq)<br />

-78 °C, 20 min<br />

ii) MeI<br />

Ph<br />

6<br />

O<br />

1<br />

N<br />

Ph<br />

2<br />

Ph<br />

6<br />

O<br />

1<br />

N<br />

Ph<br />

2<br />

Me<br />

OMe<br />

5<br />

4<br />

3<br />

OMe<br />

5<br />

4<br />

102c 103c<br />

3<br />

OMe<br />

General procedure 4 was used employing oxazoline 101c (122 mg, 0.37 mmol) i-PrLi<br />

(0.55 mmol in pentanes), DMPU (0.27 cm 3 , 6 eq) and methyl iodide (0.1 cm 3 ) quench<br />

after 10 min. Flash chroma<strong>to</strong>graphy (99:1 <strong>to</strong> 95:1 petrol:EtOAc) yielded oxazoline<br />

102c (77 mg, 54%) as colourless flowers, 103c (11 mg, 9%) as a colourless oil, and<br />

starting material (24 mg, 20%).<br />

102c R f : 0.55 (4:1 petrol:EtOAc); Mpt: 135-7 °C (PhMe); [α] 19 D : –105 (c = 0.25,<br />

CH 2 Cl 2 ); MS m/z (CI+): 388 (100%, MH + ); HRMS (ESI+) m/z found 388.2281 (MH<br />

calcd. 388.2271); Microanalysis: % found (% calc’d for C 26 H 29 NO 2 ) C, 78.36 (80.59),<br />

H, 7.45 (7.54), N 3.37 (3.61); IR ν max (film)/cm -1 : 2961 (m), 1659 (C=N), 1590, 1453,<br />

1269, 1209, 1083; 1 H NMR: (CDCl 3 , 300 MHz) δ 7.47-7.21 (m, 10H, Ph), 6.04 (d,<br />

1H, J 9.5, H6), 5.85 (dd, 1H, J 9.5, 6.0, H5), 5.23 (d, 1H, J 8.5, CHOPh), 5.13-5.06<br />

(m, 2H, H4, CHNPh), 3.63 (s, 3H, OMe), 2.38 (d, 1H, J 3.0, H2), 2.08 (pd, 1H, J 7.0,<br />

3.0, CHMe 2 ), 1.56 (s, 3H, Me), 1.10 (d, 3H, J 7.0, CHMe A Me B ), 1.10 (d, 3H, J 7.0,<br />

CHMe A Me B ); 13 C NMR: (CDCl 3 , 75 MHz) δ 171.3 (C=N), 157.2 (C3), 141.9 (ipso-<br />

Ph), 140.4 (ipso-Ph), 128.8 (Ph), 128.7 (Ph), 128.2 (para-Ph), 127.5 (para-Ph), 126.6<br />

(Ph), 125.6 (Ph), 125.0 (C6), 122.0 (C5), 93.0 (C4), 88.8 (CHO), 78.7 (CHN), 54.2<br />

(OMe), 51.4 (C2), 43.6 (C1), 30.7 (CHMe 2 ) , 25.0 (Me), 23.6 (CHMe A Me B ), 17.9<br />

(CHMe A Me B ).<br />

202


Experimental for chapter 2<br />

103c R f : 0.45 (4:1, petrol:EtOAc); MS m/z (CI) 344 (100%, MH + ), 345 (25%,<br />

(M+1)H + ); HRMS: found 344.1650, MH requires 344.1645; IR ν max (film)/cm⎯¹ 2930<br />

(m), 1644, 1461 (m, C-Me), 1259, 1046; ¹H-NMR (CDCl 3 , 300 MHz) δ 7.56 (d, 1H, J<br />

8.0, H6), 7.50-7.22 (m, 11H, Ph, H5), 7.01 (d, 1H, J 8.0, H4), 5.37 (d, 1H, J 8.0,<br />

CHOPh), 5.29 (d, 1H, J 8.0, CHNPh), 3.89 (s, 3H, OMe), 2.59 (s, 3H, Me); ¹³C-NMR<br />

(CDCl3, 75.5 MHz) δ 164.8 (C3), 158.1 (C=N), 142.1 (ipso-Ph), 140.6 (ipso-Ph),<br />

128.9, 128.8, 128.4, 127.7, 126.7, 126.1, 125.8 (Ph, C6), 122.1 (C5), 112.6 (C4), 88.4<br />

(CHOPh), 79.3 (CHNPh), 55.8 (OMe), 13.4 (Me).<br />

Synthesis of (4R*,5R*)-2-((1S*,6R*)-6-isopropyl-1-methyl-4-phenylcyclohexa-2,4-<br />

dienyl)-4,5-diphenyloxazoline (102g) & (4R*,5R*)-2-(4-methoxy-2-methylphenyl)-<br />

4,5-diphenyloxazoline (116g)<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

i) i-PrLi (1.5 eq), DMPU (6 eq)<br />

-78°C<br />

ii) MeI<br />

O<br />

1<br />

6<br />

N<br />

2<br />

O<br />

1<br />

6<br />

N<br />

2<br />

Ph (±)<br />

5<br />

4<br />

Ph<br />

3<br />

5<br />

4<br />

Ph<br />

3<br />

102g<br />

116g<br />

General procedure 4 was used employing oxazoline 101g (70 mg, 0.19 mmol) i-PrLi<br />

(0.56 mmol in pentane), DMPU (0.14 cm 3 , 6 eq) in THF, and a methyl iodide (0.1<br />

cm 3 ) quench after 30 min. Flash chroma<strong>to</strong>graphy (19:1 petrol:EtOAc) and reverse<br />

phase mass directed au<strong>to</strong> purification (MDAP) yielded diene 102g (27 mg, 32%),<br />

oxazoline 116g (24 mg, 30%) and starting material (10 mg, 14%) all as clear<br />

colourless oils.<br />

102g R f : 0.51 (4:1 petrol:EtOAc); MS m/z (CI+): 434 (100%, MH + ), 435 (31%,<br />

(M+1)H + ); HRMS (ESI+): m/z found 434.2484 (MH calcd. 434.2478); IR<br />

ν max (film)/cm -1 : 2958 (m, C-H), 2360 (m), 1659 (C=N), 1453 (m), 1087; 1 H-NMR<br />

(CDCl 3 , 400 MHz) δ 7.41-7.26 (m, 8H, Ph), 7.25-7.14 (m, 6H, Ph), 7.11-7.07 (m, 1H,<br />

Ph), 6.46 (d, 1H, J 10.0, H6), 6.20 (dd, 1H, J 10.0, 1.5, H5), 5.92 (d, 1H, J 6.0, H3),<br />

5.17 (d, 1H, J 9.0, CHO), 5.01 (d, 1H, J 9.0, CHN), 2.63 (dd, 1H, J 6.0, 3.0, H2), 2.03<br />

(pd, 1H, J 7.0, 3.0, CHMe 2 ), 0.99 (d, 3H, J 7.0, CHMe A Me B ), 0.97 (d, 3H, J 7.0,<br />

CHMe A Me B ); 13 C-NMR (CDCl 3 , 125 MHz) δ 170.3 (C=N), 140.9 (C4), 139.4 (ipso-<br />

203


Experimental for chapter 2<br />

Ph), 139.3 (ipso-Ph), 135.1 (ipso-Ph), 132.8 (C5), 127.9, 127.8, 127.4 (Ph), 127.4<br />

(para-Ph), 126.6 (para-Ph), 126.1 (para-Ph), 125.7, 124.8, 124.6, 122.1, 88.0 (CHO),<br />

77.8 (CHN), 46.9 (C2), 40.2 (C1), 31.1 (CHMe 2 ), 24.8 (CMe), 20.4 (CHMe a Me b ), 16.5<br />

(CHMe a Me b ).<br />

116g R f : 0.44 (4:1 petrol:EtOAc); MS m/z (CI+): 418 (100%, MH + ), 419 (28%,<br />

(M+1)H + ); HRMS (ESI+): m/z found 418.2166 (MH calcd. 418.2165); IR<br />

ν max (film)/cm -1 : 2963 (C-H), 1640 (C=N), 1260, 1040; 1 H-NMR (CDCl 3 , 400 MHz) δ<br />

8.03 (d, 1H, J 8.5, H6), 7.72-7.66 (m, 3H, Ar) 7.55-7.34 (m, 15H, Ar), 5.41 (d, 1H, J<br />

8.0, CHO), 5.34 (d, 1H, J 8.0, CHN), 4.24 (p, 1H, J 7.0, CHMe 2 ), 1.40 (d, 6H, J 7.0,<br />

CHMe 2 ); 13 C-NMR (CDCl 3 , 100 MHz) δ 164.6 (C=N), 150.1 (C1), 143.8 (C4), 142.1<br />

(ipso-Ph), 140.7 (ipso-Ph), 140.6 (ipso-Ph), 130.8 (C6), 128.9 (meta-Ph), 128.8 (meta-<br />

Ph), 128.4, 127.7, 127.7 (C2, para-Ph), 127.3, 126.6, 125.8 (Ph), 125.2, 124.9, 124.3.<br />

88.3 (CHO), 79.4 (CHN), 29.6 (CHMe 2 ), 24.1 (CHMe a Me b ), 23.9 (CHMe a Me b ).<br />

Synthesis of (4R,5R)-2-((1S,6S)-5-allyloxy-6-isopropyl-1-methylcyclohexa-2,4-<br />

dienyl)-4,5-diphenyloxazoline (101j) & (4R,5R)-2-(4a,5-dihydro-5-methyl-4Hchromen-5-yl)-4,5-diphenyloxazoline<br />

(142)<br />

Ph Ph<br />

Ph Ph Ph Ph Ph Ph<br />

O<br />

N<br />

O<br />

N<br />

O<br />

N<br />

O<br />

N<br />

O<br />

i) i-PrLi, DMPU<br />

ii) MeI<br />

6<br />

5<br />

1<br />

4<br />

2<br />

3<br />

O<br />

102j<br />

7<br />

8<br />

9<br />

6<br />

5<br />

1<br />

4<br />

2<br />

3 7<br />

O<br />

102j*<br />

8<br />

9<br />

6<br />

5<br />

1<br />

4<br />

2<br />

3<br />

9<br />

O<br />

142<br />

8<br />

7<br />

General procedure 4 was used employing oxazoline 101j (73 mg, 0.21 mmol) i-PrLi<br />

(0.42 mmol in pentane), DMPU (0.15 cm 3 , 1.26 mmol) and methyl iodide (0.05 cm 3 )<br />

quench after 11 min. Flash chroma<strong>to</strong>graphy (99:1 <strong>to</strong> 1:4 petrol:EtOAc) yielded<br />

oxazoline 102j (8 mg, 10%), 102j* (4 mg, 5%) and 142 (15 mg, 20% 2:3 ratio) as<br />

colourless oils.<br />

204


Experimental for chapter 2<br />

102j R f : 0.32 (9:1, petrol:EtOAc); [α] 22 D : –105 (c = 1, CHCl 3 ); MS m/z (ES+) 414<br />

(100%, MH + ), 415 (32%, (M+1)H + ); HRMS: found 414.2421, MH requires 414.2428;<br />

IR ν max (film)/cm⎯¹ 2918 (m), 1658 (C=N), 1588, 1453 (m), 1268 (m), 1189 (m), 1083;<br />

¹H-NMR (CDCl 3 , 500 MHz) δ 7.43-7.34 (m, 5H, Ph), 7.33-7.28 (m, 3H, Ph), 7.25-<br />

7.21 (m, 2H, Ph), 6.06-5.96 (m, 2H, H6, H8), 5.82 (dd, 1H, J 9.5, 6.0, H5), 5.38 (dq,<br />

1H, J 17.5, 1.5, H9-trans), 5.25 (dq, 1H, J 10.5, 1.5, H9-cis), 5.21 (d, 1H, J 8.5,<br />

CHOPh), 5.09 (d, 1H, J 6.0, H4), 5.07 (d, 1H, J 8.5, CHNPh), 4.35 (ddt, 1H, J 13.0,<br />

5.5, 1.5, H7 a ), 4.29 (ddt, 1H, J 13.0, 5.0, 1.5, H7 b ), 2.41 (d, 1H, J 3.0, H2), 2.07 (pd,<br />

1H, J 7.0, 3.0, CHMe 2 ), 1.55 (s, 3H, Me), 1.09 (d, 3H, J 7.0, i-Pr), 1.03 (d, 3H, J 7.0, i-<br />

Pr); ¹³C-NMR (CDCl 3 , 125 MHz) δ 171.4 (C=N), 156.0 (C3), 142.0 (ipso-Ph), 140.5<br />

(ipso-Ph), 133.2 (C8), 128.9, 128.8, 128.3, 127.6, 126.7, 125.7 (Ph), 125.2 (C6), 122.0<br />

(C5), 116.9 (C9), 94.1 (C4), 88.8 (CHOPh), 78.8 (CHNPh), 67.7 (C7), 51.4 (C2), 43.7<br />

(C1), 30.9 (CHMe 2 ), 25.2 (Me), 23.8 (i-Pr), 17.9 (i-Pr).<br />

102j* R f : 0.32 (9:1, petrol:EtOAc); [α] 23 D : –56 (c = 0.5, CHCl 3 ); MS m/z (ES+) 414<br />

(100%, MH + ), 415 (34%, (M+1)H + ); HRMS: found 414.2423, MH requires 414.2428;<br />

IR ν max (film)/cm⎯¹ 2918 (m), 2362, 1995, 1661 (C=N), 1456 (m); ¹H-NMR (CDCl 3 ,<br />

500 MHz) δ 7.44-7.34 (m, 6H, Ph), 7.34-7.28 (m, 2H, Ph), 7.24-7.20 (m, 2H, Ph), 6.29<br />

(dd, 1H, J 6.0, 1.5, H7), 6.08 (d, 1H, J 9.5, H6), 5.81 (dd, 1H, J 9.5, 6.0, H5), 5.27 (d,<br />

1H, J 6.0, H4), 5.23 (d, 1H, J 8.5, CHOPh), 5.08 (d, 1H, J 8.5, CHNPh), 4.85 (quin,<br />

1H, J 6.5, H8), 2.48 (d, 1H, J 3.0, H2), 2.09 (pd, 1H, J 7.0, 3.0, CHMe 2 ), 1.66 (dd, 3H,<br />

J 7.0, 1.5, H9), 1.57 (s, 3H, Me), 1.11 (d, 3H, J 7.0, CHMe A Me b ), 1.07 (d, 3H, J 7.0,<br />

CHMe a Me B ); ¹³C-NMR (CDCl 3 , 125 MHz) δ 171.1 (C=N), 154.5 (C3), 141.9 (ipso-<br />

Ph), 140.4 (ipso-Ph), 139.3 (C7), 128.9, 128.8, 128.4, 127.6, 126.7, 126.5, 125.7 (Ph),<br />

121.5 (C5), 107.5 (C8), 97.5 (C4), 88.9 (CHOPh), 78.8 (CHNPh), 50.8 (C2), 43.8<br />

(C1), 31.0 (CHMe 2 ), 25.2 (Me), 23.5 (CHMe a Me B ), 17.9 (CHMe A Me b ), 9.6 (C9).<br />

142 (major diastereoisomer) R f : 0.16 (9:1, petrol:EtOAc); [α] 22 D : +52 (c = 1, CHCl 3 );<br />

MS m/z (ES+) 370 (100%, MH + ), 371 (74%, (M+1)H + ), 392 (30%, MNa + ), 761 (56%,<br />

2MNa + ); HRMS: found 370.1800, MH requires 370.1802; IR ν max (film)/cm⎯¹ 2918<br />

(w), 1649 (C=N), 1451 (m), 1243, 1078; ¹H-NMR (CDCl 3 , 500 MHz) δ 7.41-7.34 (m,<br />

6H, Ph), 7.33-7.29 (m, 2H, Ph), 7.23-7.18 (m, 2H, Ph), 6.38 (dd, 1H, J 6.0, 2.5, H7),<br />

6.00 (dq, 1H, J 10.0, 2.0, H5), 5.79 (dt, 1H, J 10.0, 3.0, H6), 5.50 (dt, 1H, J 16.0, 1.5,<br />

205


Experimental for chapter 2<br />

H4), 5.23 (dd, 1H, J 7.5, 1.5, CHOPh), 4.99 (dd, 1H, J 7.0, 2.0, CHNPh), 4.89 (td, 1H,<br />

J 6.0, 2.0, H8), 3.13-3.06 (m, 1H, H2), 2.28 (dtd, 1H, J 16.0, 6.0, 2.5, H9), 2.01-1.99<br />

(tm, 1H, J 16.0, H9'), 1.58 (d, 1H, J 1.5, Me); ¹³C-NMR (CDCl 3 , 125 MHz) δ (all<br />

peaks) 171.3, 171.3, 150.1, 150.0, 142.1, 141.8, 140.7, 129.1, 129.0, 128.8, 128.7,<br />

128.3, 127.6, 126.5, 126.4, 125.4, 105.3, 105.1, 101.1, 101.1, 88.9, 78.4, 78.4, 40.7,<br />

31.1, 31.1, 28.2, 28.2, 26.9, 26.9; ¹³C-NMR (CDCl 3 , 125 MHz) δ (assigned, ignoring<br />

apparent doublets) 171.3 (C=N), 150.1 (C3); 142.1, 141.8, 140.7 (ipso-Ph, C7), 129.1,<br />

129.0, 128.8, 128.7, 128.3, 127.6, 126.5, 126.4, 125.4 (Ph, C6, C5), 105.3, 101.1 (C8,<br />

C4), 88.9 (CHOPh), 78.4 (CHNPh), 40.7 (C2), 31.1 (C1), 28.2 (C9), 26.9 (Me).<br />

Synthesis of (4S,5S)-2-((1R,6R)-6-isopropyl-4-methoxy-1-methylcyclohexa-2,4-<br />

dienyl)-4-(methoxymethyl)-5-phenyloxazoline (105)<br />

Ph OMe<br />

O N<br />

i) i-PrLi, DMPU<br />

ii) MeI<br />

OMe<br />

104b<br />

Ph OMe<br />

O N<br />

OMe<br />

OMe<br />

107 108<br />

22% 4%<br />

General procedure 4 was used employing oxazoline 104b (180 mg, 0.60 mmol) i-PrLi<br />

(0.96 mmol), DMPU (1.0 cm 3 , 13 eq) and methyl iodide (0.1 cm 3 ) quench after 30<br />

min. Flash chroma<strong>to</strong>graphy (9:1 petrol:EtOAc) yielded diene 105 (50 mg, 24%),<br />

oxazoline 107 (46 mg, 22%), oxazoline 106 (14 mg, 7%) diene 108 (8 mg, 4%) and<br />

starting material (18 mg, 10%) as colourless oils.<br />

1<br />

6<br />

5<br />

Me<br />

2<br />

3<br />

4<br />

Ph OMe<br />

O N<br />

OMe<br />

OMe<br />

105<br />

106<br />

24% 7%<br />

Ph Me OMe Ph Me OMe<br />

O N<br />

O N<br />

Me<br />

1<br />

Me<br />

1<br />

6<br />

2<br />

5<br />

3<br />

5<br />

4<br />

1<br />

6<br />

5<br />

4<br />

6<br />

2<br />

3<br />

2<br />

3<br />

4<br />

Me<br />

206


Experimental for chapter 2<br />

105 R f : 0.60 (4:1 petrol:EtOAc); [α] 22 D : +268 (c = 1.6, CH 2 Cl 2 ); MS m/z (CI+): 356<br />

(100%, MH + ), 357 (19%, (M+1)H + ); HRMS (ESI+) m/z found 356.2217 (MH calcd.<br />

356.2220); IR ν max (film)/cm -1 : 2955, 2928 (m, C-H), 1662 (C=N), 1451 (m), 1217; 1 H-<br />

NMR (CDCl 3 , 300 MHz) δ 7.45-7.21 (m, 5H, Ph), 6.29 (d, 1H, J 9.5, H6), 5.70 (dd,<br />

1H, 9.5, 2.0, H5), 5.36 (d, 1H, J 6.5, CHPh), 4.49 (dd, 1H, J 6.5, 2.0, H3), 4.15 (td, 1H,<br />

J 6.5, 4.5, CHN), 3.67 (dd, 1H, J 9.5, 4.5, CH a H b ), 3.60 (s, 3H, OMe), 3.49-3.43 (m,<br />

1H, CH a H b ), 3.40 (s, 3H, OMe), 2.51 (dd, 1H, J 6.5, 3.5, H2), 1.95-1.83 (m, 1H,<br />

CHMe 2 ), 1.48 (s, 3H, Me), 0.91 (d, 3H, J 6.5, CHMe a Me b ) 0.82 (d, 3H, J 6.5<br />

CHMe a Me b ); 13 C-NMR (CDCl 3 , 75 MHz) δ 171.4 (CNO), 153.2 (C4), 141.5 (ipso-<br />

Ph), 135.2 (C5), 129.0 (meta-Ph), 128.3 (para-Ph), 125.7 (ortho-Ph), 121.8 (C4), 88.8<br />

(C3), 83.6 (CHPh), 74.7 (CH 2 OMe), 74.7 (CHN), 59.5 (OMe), 54.5 (OMe), 47.3 (C2),<br />

41.9 (C1), 31.6 (CHMe 2 ), 25.8 (C1-Me), 21.6 (CHMe a Me b ), 17.0 (CHMe a Me b ).<br />

106 R f : 0.30 (4:1 petrol:EtOAc); MS m/z (CI+): 312 (100%, MH + ), 313 (17%,<br />

(M+1)H + ); HRMS (ESI+) m/z found 312.1584 (MH calcd. 312.1594); IR<br />

ν max (film)/cm -1 : 2932 (m, C-H), 1639 (C=N), 1608, 1505, 1249; 1 H-NMR (CDCl 3 , 300<br />

MHz) δ 7.99 (d, 2H, J 9.0, ortho-H), 7.39-7.30 (m, 5H, Ph), 6.94 (d, 2H, J 9.0, meta-<br />

H), 5.46 (d, 1H, J 7.0, CHPh), 4.30 (td, 1H, J 6.5, 4.5, CHN), 3.86 (s, 3H, ArOMe),<br />

3.73 (dd, 1H, J 9.5, 3.5, CH a H b ), 3.61 (dd, 1H, J 9.5, 6.5, CH a H b ), 3.44 (s, 3H,<br />

CH 2 OMe); 13 C-NMR (CDCl 3 , 75 MHz) δ 164.2 (CNO), 162.5 (C4), 141.3 (ipso-Ph),<br />

130.5, 129.0, 128.4, 125.8 (Ar CH), 120.3 (C1), 114.0 (meta-CH), 83.8 (CHPh), 75.2<br />

(CH 2 ), 74.8 (HCN), 59.6, 55.6 (OMe), 22.8 (Me).<br />

107 R f : 0.40 (4:1 petrol:EtOAc); [α] 22 D : +106 (c = 1.4, CH 2 Cl 2 ) MS m/z (CI+): 326<br />

(100%, MH + ), 327 (20%, (M+1)H + ); HRMS (ESI+) m/z found 326.1745 (MH calcd.<br />

326.1751); IR ν max (film)/cm -1 : 2927 (m, C-H), 1641 (C=N), 1607,1503, 1248; 1 H-<br />

NMR (CDCl 3 , 300 MHz) δ 7.99 (d, 2H, J 9.0, ortho-H), 7.39-7.30 (m, 5H, Ph), 6.94-<br />

6.91 (m, 1H, meta-H), 4.30 (dd, 1H, J 6.5, 4.5, CHN), 3.86 (s, 3H, ArOMe), 3.73 (dd,<br />

1H, J 9.5, 3.5, CH a H b ), 3.61 (dd, 1H, J 9.5, 6.5, CH a H b ), 3.44 (s, 3H, CH 2 OMe), 2.62<br />

(s, 3H, BnMe), 1.79 (s, 3H, ArMe); 13 C-NMR (CDCl 3 , 75 MHz) δ 163.6 (CNO), 161.5<br />

(C4), 147.3, 141.3 (ipso-Ph), 132.1, 128.7, 127.4 (C2), 124.8, 120.1 (C1), 116.9,<br />

111.2, 88.3 (COPh), 75.3 (CH 2 ), 72.8 (HCN), 59.4 (OMe), 55.5 (OMe), 23.0 (Me),<br />

22.6 (Me).<br />

207


Experimental for chapter 2<br />

108 R f = 0.62 (4:1 petrol:EtOAc); [α] 22 D : +269 (c = 0.4); MS m/z (CI+): 370 (100%,<br />

MH + ), 371 (22%, (M+1)H + ); HRMS (ESI+) m/z found 370.2373 (MH calcd.<br />

370.2377); IR ν max (film)/cm -1 : 2929 (m), 1660, 1651, 1450, 1217; 1 H-NMR (CDCl 3 ,<br />

300 MHz) δ 7.44-7.19 (m, 5H, Ph), 6.21 (d, 1H, J 10.0, H6), 5.67 (dd, 1H, J 10.0, 2.0,<br />

H5), 5.36 (d, 1H, J 6.5, CHPh), 4.48 (dd, 1H, J 6.5, 2.0, H3), 4.28 (dd, 1H, J 9.0, 4.5,<br />

CHN), 3.72 (dd, 1H, J 9.5, 4.5, CH a H b ), 3.61 (s, 3H, OMe), 3.53 (dd, 1H, J 9.5, 9.0<br />

CH a H b ), 3.41 (s, 3H, OMe), 2.54 (ddd, 1H, J 6.5, 3.5, 1.0, H2), 1.90 (pd, 1H, J 7.0, 3.5<br />

CHMe 2 ), 1.47 (s, 3H, Me), 0.90 (d, 3H, J 6.5, CHMe a Me b ) 0.83 (d, 3H, J 6.5<br />

CHMe a Me b ); 13 C-NMR (CDCl 3 , 125 MHz) δ 169.7 (CNO), 153.0 (C4), 147.7 (ipso-<br />

Ph), 135.0 (C5), 128.8 (meta-Ph), 127.0 (para-Ph), 124.2 (ortho-Ph), 121.5 (C4), 88.5<br />

(C3), 83.6 (CHPh), 74.6 (CH 2 OMe), 72.3 (CHN), 59.0 (OMe), 54.3 (OMe), 47.0 (C2),<br />

41.6 (C1), 31.2 (CHMe 2 ), 25.8 (C1-Me), 23.2 (Bn-Me) 21.3 (CHMe a Me b ), 16.7<br />

(CHMe a Me b ).<br />

Synthesis of (4S,5S)-2-((1R,6S)-6-isopropyl-1-methylcyclohexa-2,4-dienyl)-4-<br />

methyl-5-phenyloxazoline (112)<br />

Ph<br />

Me<br />

Ph<br />

Me<br />

Ph<br />

Me<br />

Ph<br />

Me<br />

Me<br />

O<br />

N<br />

i) i-PrLi (1.5 eq), DMPU (6 eq)<br />

−78 °C, 30 min<br />

ii) MeI<br />

O<br />

N<br />

Me<br />

+<br />

O<br />

N<br />

Me<br />

+<br />

O<br />

N<br />

Me<br />

40% 12% 5%<br />

112 113 114<br />

General procedure 4 was used employing oxazoline 110 (100 mg, 0.42 mmol) i-PrLi<br />

(0.63 mmol in pentane), DMPU (0.34 cm 3 , 6 eq) and methyl iodide (0.1 cm 3 ) quench<br />

after 30 min. Flash chroma<strong>to</strong>graphy (9:1 petrol:EtOAc) yielded, diene 112 (41 mg,<br />

40%) as clear needles, oxazoline 113 (28 mg, 12%) as a clear oil and oxazoline 114<br />

(12 mg, 6%) as a clear oil.<br />

112 R f : 0.45 (4:1 petrol:EtOAc); Mpt: 72-73 °C (EtOAc); [α] 23 D : +388 (c = 0.3,<br />

EtOH); MS m/z (CI+): 296 (100%, MH + ), 297 (21%, (M+1)H + ); HRMS (ESI+) m/z<br />

found 296.2011 (MH calcd. 296.2009); IR ν max (film)/cm -1 : 2960 (C-H), 1663 (C=N),<br />

1453, 1109, 1077; 1 H-NMR (CDCl 3 , 300 MHz) δ 7.34-7.18 (m, 5H, Ph), 6.10 (dd, 1H,<br />

J 10.0, 1.0, H6), 5.97 (dd, 1H, J 10.0, 5.0, H4), 5.74 (ddd, 1H, J 10.0, 5.0, 1.0, H5),<br />

208


Experimental for chapter 2<br />

5.55 (dd, 1H, J 6.0, 10.0, H3), 4.87 (d, 1H, J 7.5, CHPh), 3.95 (quin, 1H, J 6.5, NCH),<br />

2.39-2.33 (m, 1H, H2), 1.85-1.72 (m, 1H, CHMe 2 ), 1.36 (s, 3H, H7), 1.31 (d, 3H, J<br />

6.5, CHMe), 0.85 (d, 3H, J 7.0, CHMe A Me b ), 0.82 (d, 3H, J 7.0, CHMe a Me B ); 13 C-<br />

NMR (CDCl 3 , 75 MHz) δ 169.8 (C=N), 140.8 (ipso-Ph), 132.4, 128.7, 128.1, 125.4,<br />

124.2, 123.8, 121.4, (C3, C4, C5, C6 & Ph), 87.6 (COPh), 70.5 (CN), 47.5 (C2), 31.2<br />

(CMe 2 ), 25.2 (C7), 21.6 (CNMe), 21.2 (CMe A Me b ), 16.7 (CHMe a Me B ).<br />

113 R f : 0.42 (4:1 petrol:EtOAc); [α] 23 D : +122 (c = 0.2, EtOH); MS m/z (CI+): 252<br />

(100%, MH + ), 253 (17%, (M+1)H + ); HRMS (ESI+) m/z found 252.1382 (MH calcd.<br />

252.1383); IR ν max (film)/cm -1 : 2964 (C–H), 1643 (C=N), 1453 (m), 1317 (m), 1039;<br />

1 H-NMR (CDCl 3 , 300 MHz) δ 7.79-7.76 (m, 1H, H6), 7.31-7.20 (m, 6H, Ar), 7.17-<br />

7.11 (m, 2H, Ar), 4.96 (d, 1H, J 7.5, CHPh), 4.13 (quin, 1H, J 6.5, CHMe), 2.53 (s,<br />

3H, ortho-Me), 1.39 (d, 3H, J 6.5, Me); 13 C-NMR (CDCl 3 , 75 MHz) δ 163.2 (C=N),<br />

140.7 (C), 138.8 (C), 131.2, 130.6, 129.9, 128.8, 128.2, 125.6 (Ar) 87.4 (PhCO), 71.2<br />

(MeCN), 21.8 (NCMe), 21.7 (ortho-Me).<br />

114 R f : 0.38 (4:1 petrol:EtOAc); [α] 23 D : +97 (c = 0.2, EtOH); MS m/z (CI+): 266<br />

(100%, MH + ), 253 (18%, (M+1)H + ); HRMS (ESI+) m/z found 266.1538 (MH calcd.<br />

266.1539); IR ν max (film)/cm -1 : 2975 (C-H), 1643 (C=N), 1448, 1319, 1266, 1037; 1 H-<br />

NMR (CDCl 3 , 300 MHz) δ 7.89-7.86 (m, 1H, H6), 7.44-7.23 (m, 9H, Ar), 4.34 (q, 1H,<br />

J 7.0, CHMe), 2.63 (s, 3H, ortho-Me), 1.65 (s, 3H, CMePh), 1.47 (d, 3H, J 7.0,<br />

CHMe); 13 C-NMR (CDCl 3 , 75 MHz) δ 162.4 (C=N), 149.3 (C), 146.6 (C), 138.6,<br />

131.2, 130.5 129.9, 128.8, 128.5, 127.2, 125.6, 124.0 (Ar), 88.5 (OCPh), 71.7<br />

(NCMe); 22.4 (OCMe) 21.7 (NCMe), 16.8 (ortho-Me).<br />

209


Experimental for chapter 2<br />

Synthesis of (4R*,5R*)-2-(2-ethyl-4-methoxyphenyl)-4,5-diphenyloxazoline (120)<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

i) i-PrLi (3 eq.), DMPU (6 eq)<br />

−78 °C<br />

O<br />

1<br />

N<br />

ii) MeI<br />

6<br />

2<br />

OMe<br />

5<br />

4<br />

OMe<br />

3<br />

General procedure 4 was used employing oxazoline 103b (250 mg, 0.73 mmol) i-PrLi<br />

(2.19 mmol in pentane), DMPU (0.52 cm 3 , 6 eq) in THF <strong>to</strong> give a wine red solution,<br />

and a methyl iodide (0.27 cm 3 ) quench after 5 min. Flash chroma<strong>to</strong>graphy (19:1 <strong>to</strong> 9:1<br />

petrol:EtOAc) yielded oxazoline 120 (170 mg, 65%) as a colourless oil.<br />

R f : 0.39 (4:1, petrol:EtOAc); MS m/z (ES+) 358 (100%, MH + ), 359 (30%, (M+1)H + );<br />

HRMS: found 358.1802, MH requires 358.1802; ¹H-NMR (CDCl 3 , 500 MHz) δ 7.89<br />

(d, 1H, J 8.5, H6), 7.31-7.16 (m, 10H, Ph), 6.75 (d, 1H, J 2.5, H3), 6.67 (dd, 1H, J 8.5,<br />

2.5, H5), 5.19 (d, 1H, J 7.5, CHOPh), 5.14 (d, 1H, J 7.5, CHNPh), 3.70 (s, 3H, OMe),<br />

3.11-3.05 (m, 2H, CH 3 ), 1.18 (t, 3H, J 7.5, CH 2 Me); ¹³C-NMR (CDCl 3 , 125 MHz) δ<br />

164.0 (C=N), 161.5 (C4), 147.6 (C2), 142.4 (ipso-Ph), 140.7 (ipso-Ph), 132.3 (C6),<br />

128.8 (meta-Ph), 128.7 (meta-Ph), 128.2 (para-Ph), 127.5 (para-Ph), 126.5 (ortho-Ph),<br />

125.6 (ortho-Ph), 115.3 (C3), 110.6 (C5), 87.8 (CHO), 79.2 (CHN), 55.1 (OMe), 27.8<br />

(CH 2 ), 15.6 (Me).<br />

210


Experimental for chapter 3.1<br />

5.3 Experimental Procedures for Chapter 3.1<br />

Synthesis of (S,S)-hydrobenzoin (176)<br />

OH<br />

Ph AD mix α, Me 2 SO 2 NH 2<br />

HO<br />

Ph<br />

Ph<br />

t-BuOH/H 2 O<br />

Ph<br />

By the Method of Sharpless 8 AD mix-α (45.93 g) and methylsulfonamide (4.70 g, 42.3<br />

mmol) were dissolved in t-BuOH (255 cm 3 ) and water (255 cm 3 ) with vigorous stirring<br />

and cooled <strong>to</strong> 0 °C. trans-Stilbene (6.00 g, 33.3 mmol) was added <strong>to</strong> the solution and<br />

stirred for 48 hr. Sodium sulfite (50 g) was added with stirring and allowed <strong>to</strong> warm <strong>to</strong><br />

ambient temperature before being partitioned in a separating funnel. <strong>The</strong> organic<br />

phase was concentrated under vacuum and recombined with the aqueous phase,<br />

washed with CH 2 Cl 2 (3 x 150 cm 3 ), brine (3 x 200 cm 3 ), and the combined organic<br />

phases dried over Na 2 SO 4 , and solvent concentrated under vacuum. <strong>The</strong> residue was<br />

purified by flash chroma<strong>to</strong>graphy (2:1 EtOAc:petrol) <strong>to</strong> give hydrobenzoin 176 (7.01<br />

g, 98%) as colourless needles.<br />

R f : 0.36 (1:2 petrol:EtOAc); Mpt: 146-147 ºC (petrol/EtOAc), lit. 9 148-150 ºC; [α] 23 D :<br />

–94 (c = 1.0, EtOH), lit. 9 –94.1 (c = 1, EtOH); MS m/z (CI + ): 232 (MNH + 4 , 100%),<br />

215 (MH + , 32%); IR ν max /cm -1 : 3498 (br, O–H), 2921, 2896, 1451, 1199, 1045;<br />

Microanalysis: % found (% calc’d for C 14 H 14 O 2 ) C, 78.73 (78.48); H, 6.73 (6.59); 1 H-<br />

NMR (DMSO, 300 MHz) δ 7.21-7.15 (m, 6H, Ph); 7.11-7.08 (m, 4H, Ph); 5.38* (s,<br />

2H, OH); 4.59 (s, 2H, CH); 13 C-NMR (DMSO, 75 MHz) δ 143.1 (ipso-Ph); 128.0,<br />

127.9, 127.4 (Ph); 78.4 (CH).<br />

Synthesis of (4S,5S)-4,5-diphenyl-1,3-dioxolan-2-one (177)<br />

O<br />

OH<br />

HO<br />

CDI<br />

O O<br />

Ph<br />

Ph<br />

Ph Ph<br />

To a stirred solution of (S,S)-hydrobenzoin (3.27 g, 15.2 mmol) in CH 2 Cl 2 (25 cm 3 )<br />

was added CDI (3.71 g, 22.9 mmol). Aqueous hydrochloric acid (50 cm 3 , 1N) was<br />

added after 6 hr and the mixture washed with CH 2 Cl 2 (2 x 50 cm 3 ), EtOAc (50 cm 3 ),<br />

211


Experimental for chapter 3.1<br />

saturated aqueous NaHCO 3 (2 x 40 cm 3 ) dried over Na 2 SO 4 and concentrated under<br />

vacuum <strong>to</strong> give cyclic carbonate 177 (3.65 g, 100%) as clear colourless prisms.<br />

20<br />

R f : 0.41 (9:1 petrol:EtOAc); Mpt: 106-108 ºC (CH 2 Cl 2 ); [α] D : –122 (c = 0.5,<br />

CH 2 Cl 2 ); MS m/z (CI+): 258 (100%, MNH + 4 ) 259 (18%, (M+1)NH + ), 241 (13%,<br />

MH + ); Microanalysis: % found (% calc’d for C 15 H 12 O 3 ) C, 75.22 (74.99); H, 5.06<br />

(5.03); IR ν max /cm -1 : 1822 (C=O), 1458, 1187, 1044; 1 H-NMR (CDCl 3 , 500 MHz) δ<br />

7.46-7.42 (m, 6H, ortho/para-Ph), 7.34-7.30 (m, 4H, meta-Ph), 5.43 (s, 2H, PhCH);<br />

13 C-NMR (CDCl 3 , 125 MHz) δ 154.1 (C=O), 134.8 (ipso-Ph), 129.8, 129.3, 126.1,<br />

85.4 (PhCH).<br />

Synthesis of (1S,2R)-2-azido-1,2-diphenylethanol (178) & (2R,3R)-2,3-<br />

diphenylaziridine (173)<br />

Ph<br />

O<br />

O<br />

O<br />

Ph<br />

H<br />

N<br />

i) NaN 3 HO N 3<br />

ii) PPh 3<br />

Ph Ph<br />

Ph Ph<br />

178 173<br />

Adapted from the methods of Sharpless 10 sodium azide (894 mg, 13.7 mmol) was<br />

added <strong>to</strong> a stirred solution of cyclic carbonate (3.0 g, 12.5 mmol) in DMF (12 cm 3 ) and<br />

water (0.20 cm 3 , 11 mmol) and heated <strong>to</strong> 110 °C for 48 hr under a nitrogen<br />

atmosphere. Upon cooling, the resulting slurry was triturated with Et 2 O (3 x 50 cm 3 ),<br />

filtered through Celite, and solvent removed under vacuum distillation <strong>to</strong> give crude<br />

azide 178 as an orange oil. 11<br />

By the method of Blum, 12 crude azide 178 was dissolved in Et 2 O (175 cm 3 ),<br />

triphenylphosphine (3.28 g, 12.5 mmol) added and the solution brought <strong>to</strong> reflux for 2<br />

hr. Et 2 O was added until precipitation s<strong>to</strong>pped, the mixture filtered and the filtrate<br />

concentrated under vacuum. Flash chroma<strong>to</strong>graphy (90:9:1 petrol:EtOAc:Et 3 N) gave<br />

aziridine 173 (1.57 g, 64%) as clear needles.<br />

R f : 0.16 (9:1 petrol:EtOAc); Mpt: 44-46 ºC (EtOAc), lit. 13 45-46 ºC; [α] D 20 : +350 (c =<br />

0.4, EtOH), lit +328.8 (c = 1.25, CHCl 3 ) 14 ; MS m/z (CI+): 196 (100%, MH + ), (19%,<br />

(M+1)H + ); HRMS (ESI+) m/z found 194.0959 (MH calcd. 194.0964); IR<br />

212


Experimental for chapter 3.1<br />

ν max (film)/cm -1 : 3030 (NH), 1602, 1496; 1 H-NMR (CDCl 3 , 300 MHz) δ 7.45-7.22 (m,<br />

10H, H-Ar), 3.18 (s, 2H, CHPh), 1.50 (br, 1H, NH); 13 C-NMR (CDCl 3 , 75 MHz) δ<br />

139.9 (ipso-Ph), 128.9, 127.6, 125.8 (Ph), 44.0 (CHPh).<br />

Synthesis of (1S, 2R)-2-amino-1,2-diphenylethanol (174)<br />

HO<br />

N 3<br />

H 2 , Pd/C, HCl HO NH 2<br />

Ph Ph<br />

Ph Ph<br />

By method of Sharpless 10 hydrochloric acid (0.56 cm 3 in 0.5 cm 3 water, 6.3 mmol) was<br />

added drop wise <strong>to</strong> a stirred solution of crude azide 178 (1.25 g, 5.23 mmol) and<br />

palladium on charcoal (10%, 60 mg) in EtOH (9 cm 3 ). <strong>The</strong> mixture was placed under<br />

atmospheric pressure of hydrogen, and stirred vigorously for 48 hr. Water (20 cm 3 )<br />

was added and the mixture concentrated under vacuum before filtration and acid-base<br />

extraction in<strong>to</strong> CH 2 Cl 2 (3 x 20 cm 3 ), dried over Na 2 SO 4 and solvent evaporated.<br />

Amino alcohol 174 (1.09 g, 97%) was isolated as clear colourless needles by<br />

recrystallisation from CH 2 Cl 2 .<br />

R f : 0.22 (19:1 EtOAc:MeOH); Mpt: 143-144 °C (CH 2 Cl 2 ), lit. 143-144 °C (no solvent<br />

stated) 10 ; [α] 22 D : +8.0 (c = 0.6, EtOH) lit. 10 for enantiomer –7.0 (c = 0.6, EtOH, no<br />

temp stated), MS m/z (CI+): 214 (100%, MH + ), 216 (6%, (M+1)H + ); IR ν max (film)/cm -<br />

1 : 3064, 1604, 1595; 1 H-NMR (CDCl 3 , 500 MHz) δ 7.36-7.21 (m, 10H, Ph), 4.77 (d,<br />

1H, J 6.5, CHOH), 4.19 (d, 1H, J 6.5, CHNH 2 ), 1.67 (br s, 3H, OH, NH 2 ); 13 C-NMR<br />

(CDCl 3 , 125 MHz) δ 141.5 (ipso-Ph), 140.5 (ipso-Ph), 128.5 (meta-Ph), 128.0 (meta-<br />

Ph), 127.7 (para-Ph), 127.6 (para-Ph), 127.1 (ortho-Ph), 126.6 (ortho-Ph), 78.3<br />

(CHOH), 61.7 (CHNH 2 ).<br />

Synthesis of cis-stilbene oxide (179)<br />

O<br />

mCPBA<br />

Ph Ph<br />

Ph Ph<br />

mCPBA (1.58 g, 70% purity, 6.4 mmol) was added portion wise <strong>to</strong> a solution of cisstilbene<br />

(1.011 cm 3 , 5.3 mmol) in CH 2 Cl 2 (50 cm 3 ) and stirred for 6 hr, before addition<br />

of aqueous sodium sulfite (saturated, 10 cm 3 ). <strong>The</strong> solution was washed with saturated<br />

aqueous NaHCO 3 (2 x 50 cm 3 ), CH 2 Cl 2 (2 x 50 cm 3 ), EtOAc (50 cm 3 ), dried over<br />

213


Experimental for chapter 3.1<br />

Na 2 SO 4 and solvent evaporated. cis-Stilbene oxide (935 mg, 90%) was obtained as<br />

clear colourless needles after flash chroma<strong>to</strong>graphy (20:1 <strong>to</strong> 4:1 petrol:EtOAc).<br />

R f : 0.35 (9:1 petrol:EtOAc); Mpt: 38 °C (CH 2 Cl 2 ), lit. 21 38-40 °C; MS m/z (CI+): 197<br />

(100%, MH + ), 189 (9%, (M+1)H + ), 214 (MNH + 4 ,57%); IR ν max (film)/cm -1 : 3163,<br />

2994, 1603, 1005; 1 H-NMR (CDCl 3 , 500 MHz) δ 7.72-7.16 (m, 10H, Ph), 4.40 (s, 2H,<br />

CH); 13 C-NMR (CDCl 3 , 125 MHz) δ 134.3 (ipso-Ph), 127.7, 127.5, 126.8 (Ph), 29.7<br />

(CH).<br />

Synthesis of (R*,R*)-2-amino-1,2-diphenylethanol (175)<br />

Ph<br />

O<br />

Ph<br />

NH3 (aq.)<br />

HO<br />

Ph<br />

(±)<br />

NH 2<br />

Ph<br />

Microwave: cis-Stilbene oxide (700 mg, 3.57 mmol) was fully dissolved in MeOH (2.5<br />

cm 3 ) before addition of saturated aqueous ammonia (7.5 cm 3 ) caused a fine precipitate.<br />

<strong>The</strong> resulting solution was heated at 140 °C under microwave irradiation for 20 min<br />

(pressure peaked at 11 bar) giving a clear yellow solution, which upon standing<br />

overnight gave colourless cubes. Filtration and two further recrystallisations from<br />

diethyl ether gave racemic amino alcohol 175 (710 mg, 93%).<br />

Reflux: cis-Stilbene oxide (500 mg, 2.55 mmol) was dissolved in MeOH (19 cm 3 ) with<br />

saturated aqueous ammonia (19 cm 3 ) and brought <strong>to</strong> gentle reflux (c. 70 °C, raising <strong>to</strong><br />

80 °C) for 24 hr. <strong>The</strong> clear solution was concentrated under vacuum, transferred <strong>to</strong> a<br />

separa<strong>to</strong>ry funnel with aqueous NaOH (2 cm 3 NaOH 2N in 50 cm 3 water), washed<br />

with CH 2 Cl 2 (2 x 50 cm 3 ) and EtOAc (50 cm 3 ), dried over Na 2 SO 4 , and concentrated<br />

under vacuum <strong>to</strong> give a white solid. Purification by flash chroma<strong>to</strong>graphy (1:1<br />

petrol:EtOAc <strong>to</strong> 19:1 EtOAc:MeOH) isolated stilbene oxide (125 mg) and a white<br />

solid, which was recrystallised from CH 2 Cl 2 <strong>to</strong> give clear colourless cubic crystals of<br />

racemic amino alcohol 175 (295 mg, 55%).<br />

R f : 0.24 (19:1 EtOAc:MeOH); Mpt: 127-128 °C (CH 2 Cl 2 ), lit: 116-119 °C; MS m/z<br />

(CI+): 214 (39%, MH + ), 106 (100%, CHPhNH 2 + ); IR ν max (film)/cm -1 : 3066 (br, OH),<br />

1604, 1595; 1 H-NMR (CDCl 3 , 300 MHz) δ 7.41-7.21 (m, 10H, Ph), 4.70 (d, 1H, J 6.5,<br />

214


Experimental for chapter 3.1<br />

CHOH), 4.04 (d, 1H, J 6.5, CHNH 2 ), 2.44 (br, 2H, NH 2 ); 13 C-NMR (CDCl 3 , 75 MHz)<br />

δ 142.3 (Ph CCOH), 141.6 (Ph CCNH 2 ), 128.6, 127.9, 127.4, 127.4, 127.0, 126.4 (Ph),<br />

78.0 (COH), 62.5 (CNH 2 ).<br />

Synthesis of (2R,3R)-1-benzoyl-2,3-diphenylaziridine (100a)<br />

O<br />

Cl<br />

H<br />

N<br />

Et 3 N, petrol/Et 2 O<br />

O<br />

N<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Adapted from the method of Lygo, 15 benzoyl chloride (0.084 cm 3 , 0.73 mg) was<br />

dissolved in petrol (2 cm 3 ) and added drop wise <strong>to</strong> a solution of aziridine 173 (150 mg,<br />

0.77 mmol) in petrol (5 cm 3 ), Et 2 O (2 cm 3 ) and Et 3 N (0.01 cm 3 , 0.80 mmol) at –10 °C<br />

and stirred until complete (IR). <strong>The</strong> resulting suspension was allowed <strong>to</strong> warm <strong>to</strong><br />

room temperature before trituration with Et 2 O (30 cm 3 ), filtration over celite and<br />

evaporation, yielding aroyl aziridine 100a (c. 185 mg, 84%) as a clear oil which was<br />

used without purification.<br />

R f : 0.37 (9:1 petrol:EtOAc); MS m/z (CI+): 300 (100%, MH + ), 301 (13%, (M+1)H + );<br />

IR ν max (film)/cm -1 : 3033 (CH), 1668 (CO), 1602, 1497; 1 H-NMR (CDCl 3 , 300 MHz)<br />

δ 7.96 (d, 2H, J 8.5, ortho-Ph), 7.45-7.30 (m, 13H, Ar), 4.04 (s, 2H, CHPh); 13 C-<br />

NMR (CDCl 3 , 75 MHz) δ 175.7 (CO), 135.5, 133.5, 132.3, 128.7, 128.5, 128.0, 127.9,<br />

126.4 (Ph), 49.0 (CHPh).<br />

215


Experimental for chapter 3.1<br />

Synthesis of (2R,3R)-1-(4-methoxybenzoyl)-2,3-diphenylaziridine (100b)<br />

O Cl<br />

OMe<br />

H<br />

N<br />

Ph Ph<br />

Et 3 N, petrol/Et 2 O<br />

+ 1<br />

Ph<br />

O N<br />

Ph<br />

OMe<br />

Adapted from the method of Lygo, 15 p-anisoyl chloride (800mg, 4.71mmol) was<br />

dissolved in petrol (10 cm 3 ) and added drop wise <strong>to</strong> a solution of aziridine (1.00g, 5.12<br />

mmol) in petrol (25 cm 3 ), Et 2 O (10 cm 3 ) and Et 3 N (0.71 cm 3 , 5.12 mmol) at –10 °C<br />

and stirred until complete (IR). <strong>The</strong> resulting suspension was allowed <strong>to</strong> warm <strong>to</strong><br />

room temperature before trituration with Et 2 O (200 cm 3 ), filtration over celite and<br />

evaporation, yielding aroyl aziridine 100b (1.38 g, 89%) as colourless clear needles.<br />

2<br />

3<br />

4<br />

R f : 0.29 (4:1 petrol:EtOAc); Mpt: 72 °C (Et 2 O); [α] 23 D +72 (c = 1.4, CH 2 Cl 2 ); MS m/z<br />

(CI+): 330 (100%, MH + ), 331 (22%, (M+1)H + ); HRMS (ESI+) m/z found 330.1493<br />

(MH calcd. 330.1489); IR ν max (film)/cm -1 : 1660 (C=O), 1604, 1510, 1321 (m), 1257<br />

(m); 1 H-NMR (CDCl 3 , 500 MHz) δ 7.86 (d, 2H, J 9.0, H2), 7.90-6.71 (m, 10H, Ph H),<br />

6.74 (d, 2H, J 9.0, H3), 3.93 (s, 2H, CH), 3.75 (s, 3H, OMe); 13 C-NMR (CDCl 3 , 125<br />

MHz) δ 175.0 (C=O), 162.8 (C4), 135.8 (ipso-Ph), 130.8, 128.6, 128.5, 127.9, 127.3,<br />

126.4, 126.2, 125.4 (Ar), 113.3 (C3), 55.2 (OMe), 49.1 (CN).<br />

Synthesis of (2R,3R)-1-(3-methoxybenzoyl)-2,3-diphenylaziridine (100c)<br />

O<br />

Cl<br />

Ph<br />

OMe<br />

Ph<br />

H<br />

N<br />

Ph<br />

i-Pr 2 EtN, petrol/Et 2 O<br />

6<br />

O<br />

5<br />

4<br />

N<br />

Ph<br />

1<br />

2<br />

3<br />

OMe<br />

Adapted from the method of Lygo, 15 m-anisoyl chloride (145 mg, 0.12 cm 3 , 0.85<br />

mmol) was dissolved in pentane (2 cm 3 ) and added drop wise <strong>to</strong> a solution of aziridine<br />

173 (200 mg, 1.02 mmol) in petrol (5 cm 3 ), Et 2 O (2 cm 3 ) and i-Pr 2 EtN (0.18 cm 3 , 1.02<br />

mmol) at –10 °C and stirred until complete (IR). <strong>The</strong> resulting suspension was<br />

allowed <strong>to</strong> warm <strong>to</strong> room temperature before tritriation with Et 2 O (30 cm 3 ), filtration<br />

216


Experimental for chapter 3.1<br />

over celite and evaporation, yielding aroyl aziridine 100c (244 mg, 87%) as a<br />

colourless oil.<br />

R f : 0.38 (4:1 petrol:EtOAc); IR ν max (film)/cm -1 : 1668 (C=O), 1601, 1510, 1321; 1 H-<br />

NMR (CDCl 3 , 400 MHz) δ 7.51 (d, 1H, J 8.0, Ph, H6), 7.71-7.69 (m, 1H, Ph), 7.17-<br />

7.06 (m, 11H, Ph, H5), 6.92 (ddd, 1H, J 8.5, 4.5, 1, H4), 3.95 (s, 2H, CHPh), 3.66 (s,<br />

3H, OMe); 13 C-NMR (CDCl 3 , 100 MHz) δ 175.4 (C=O), 159.3 (C3), 135.7 (ipso-Ph),<br />

140.3 (C1), 129.2 (para-Ph), 128.7 (meta-Ph), 128.2 (ortho-Ph), 121.4 (C4), 119.2<br />

(C6), 113.1 (C2), 55.3 (OMe), 49.4 (CPh).<br />

Synthesis of N-((1R,2S)-2-hydroxy-1,2-diphenylethanol)benzamide (165a)<br />

Ph<br />

O<br />

Cl<br />

Ph<br />

Ph<br />

NH 2<br />

HO<br />

O<br />

NH<br />

Ph<br />

OH<br />

Et 3 N<br />

General procedure 1 was used mixing benzoyl chloride (0.23 cm 3 , 1.95 mmol) with<br />

amino alcohol 174 (500 mg, 2.34 mmol) and triethylamine (5 cm 3 ) <strong>to</strong> give the title<br />

amide (615 mg, 99%) as a colourless powder.<br />

R f : 0.05 (EtOAc); Mpt: 243-246 °C (EtOAc); [α] 25 D : +89 (c = 0.4, DMSO); MS m/z<br />

(CI+): 318 (100%, MH + ), 319 (10%, (M+1)H + ); HRMS (ESI+) m/z found 318.1490<br />

(MH calcd. 318.1489); IR ν max (film)/cm -1 : 3337 (s, OH), 1630 (C=O), 1526; 1 H-NMR<br />

(DMSO, 300 MHz) δ 8.83 (d, 1H, J 9.0, NH), 7.74-7.67 (m, 2H, ortho-Ph), 7.50-7.34<br />

(m, 7H, Ph), 7.31-7.14 (m, 6H, Ph), 5.10 (d, 1H, J 5.0, OH), 5.13 (t, 1H, J 8.5,<br />

CHNH), 4.98 (dd, 1H, J 8.0, 5.0, CHOH); 13 C-NMR (DMSO, 125 MHz) δ 165.2<br />

(CO), 143.6, 141.3, 134.5 (ipso-Ph), 131.0, 128.5, 128.1, 127.6, 127.5, 127.3, 127.0,<br />

126.9, 126.6 (Ph), 74.4 (COH), 59.3 (CH 2 N).<br />

217


Experimental for chapter 3.1<br />

Synthesis of N-((1R,2S)-2-hydroxy-1,2-diphenylethyl)-4-methoxybenzamide<br />

(165b)<br />

Ph<br />

O Cl<br />

Ph HO<br />

Ph<br />

Ph<br />

NH 2<br />

O NH<br />

1<br />

OH<br />

2<br />

Et 3 N<br />

3<br />

OMe<br />

4<br />

OMe<br />

General procedure 1 was used mixing para-anisoyl chloride (13.9 g, 81.5 mmol) with<br />

(1R,2S)-(−)-2-amino-1,2-diphenylethanol 174 (20.0 g, 93.8 mmol) and triethylamine<br />

(22.5 cm 3 , 163 mmol) <strong>to</strong> give the title amide (25.3 g, 98%) as a colourless powder.<br />

R f : 0.42 (2:1 petrol:EtOAc); Mpt: 240-244 °C (EtOAc); [α] 25 D : +41 (c = 0.4, DMSO);<br />

MS m/z (CI+): 348 (100%, MH + ), 349 (27%, (M+1)H + ), 330 (57%, [M-H 2 O] + ), 96<br />

(61%); HRMS (ESI+) m/z found 348.1586 (MH calcd. 348.1594); IR ν max (film)/cm -1 :<br />

3334 (s, OH), 1632 (C=O), 1526; 1 H-NMR (MeOD, 300 MHz) δ 7.58 (d, 2H, J 9.0,<br />

ortho-Ph), 7.44-7.17 (m, 10H, Ph), 6.92 (d, 2H, J 9.0, meta-Ph), 5.32 (d, 1H, J 8.0,<br />

CHOH), 5.05 (d, 1H, J 8.0, CHN), 3.81 (s, 3H, OMe); 13 C-NMR (DMSO, 125 MHz) δ<br />

164.9 (CO), 161.8 (ipso-Ph), 144.1 (ipso-Ph), 142.0, 129.3, 128.7, 128.0, 127.9, 127.3,<br />

127.2, 127.1, 127.0 (Ar), 113.7 (C3), 74.9 (COH), 59.3 (CNH), 55.7 (OMe).<br />

Synthesis of N-((1R,2S)-2-hydroxy-1,2-diphenylethyl)-3-methoxybenzamide<br />

(165c)<br />

Ph<br />

O Cl<br />

Ph<br />

Ph<br />

NH 2<br />

OH<br />

OMe Et 3 N<br />

Ph<br />

HO<br />

O NH<br />

6<br />

5<br />

4<br />

1<br />

2<br />

3<br />

OMe<br />

General procedure 1 was used mixing meta-anisoyl chloride (0.30 cm 3 , 2.12 mmol)<br />

with the amino alcohol 174 (500 mg, 2.34 mmol) and triethylamine (0.6 cm 3 , 4.25<br />

mmol) <strong>to</strong> give amide 165c (710 mg, 96%) as colourless needles.<br />

218


Experimental for chapter 3.1<br />

R f : 0.45 (1:1 petrol:EtOAc); Mpt: 193-194 °C (ace<strong>to</strong>ne); [α] 24 D : –2.5 (c = 1.1,<br />

DMSO); MS m/z (CI+): 348 (100%, MH + ), 349 (22%, (M+1)H + ), 330 (16%, [M-<br />

H 2 O]H + ); HRMS (ESI+) m/z found 348.1591 (MH calcd. 348.1594); IR ν max /cm -1 :<br />

3321 (sharp, OH), 1633 (C=O), 1537, 1244; 1 H-NMR (DMSO, 500 MHz) δ 8.63 (d,<br />

1H, J 9.0, NH), 7.46 (d, 4H, J 7.5, Ph), 7.36-7.27 (m, 5H, Ar), 7.27-7.18 (m, 3H, Ar),<br />

7.15-7.11 (m, 1H, H2), 7.04 (dd, 1H, J 8.0, 2.0, H4), 5.47 (d, 1H, J 5.0, OH), 5.12 (t,<br />

1H, J 9.0, CHNH), 4.92 (dd, 1H, J 8.5, 5.0, CHOH); 13 C-NMR (DMSO, 125 MHz) δ<br />

165.4 (CO), 159.3 (C3), 144.1 (ipso-Ph), 141.9 (ipso-Ph), 136.5, 128.7, 127.3, 127.9,<br />

119.6, 117.0, 112.9, 112.7 (Ar), 74.9 (COH), 55.6 (CNH), 55.4 (OMe).<br />

Synthesis of N-((1R*,2S*)-2-hydroxy-1,2-diphenylethyl)-4-phenylbenzamide<br />

(165f)<br />

Ph<br />

O OH<br />

Ph<br />

i) DMF, (COCl) 2<br />

ii) Ph<br />

Ph<br />

OH<br />

NH 2<br />

(±)<br />

Et 3 N<br />

Ph<br />

HO<br />

O NH<br />

Ph<br />

One drop of DMF was added <strong>to</strong> a stirred solution of para-biphenyl carboxylic acid<br />

(397 mg, 2.0 mmol) and oxalyl chloride (0.19 cm 3 , 2.2 mmol) in CH 2 Cl 2 (4 cm 3 ).<br />

Once effervescence had s<strong>to</strong>pped, the solution was allowed <strong>to</strong> stir for 2 hr, the solvent<br />

was removed under reduced pressure, and the crude acid chloride reacted on. General<br />

procedure 1 was used mixing the acid chloride with the amino alcohol 174 (511 mg,<br />

2.40 mmol) and triethylamine (0.56 cm 3 , 4.0 mmol) <strong>to</strong> give amide 165f (650 mg, 83%)<br />

as a colourless powder.<br />

1<br />

2<br />

3<br />

4<br />

R f : 0.27 (1:1 petrol:EtOAc); Mpt: 222-224 °C (ace<strong>to</strong>ne); MS m/z (CI+): 394 (100%,<br />

MH + ), 395 (30%, (M+1)H + ), 376 (100%, [(M-H 2 O)H] + ); HRMS (ESI+) m/z found<br />

394.1803 (MH calcd. 394.1802); IR ν max (film)/cm -1 : 3320 (m), 1635 (C=O), 1540 (m);<br />

1 H-NMR (DMSO, 300 MHz) δ 8.69 (d, 1H, J 9.0, NH), 7.79-7.65 (m, 6H, Ar), 7.52-<br />

7.35 (m, 7H, Ar), 7.34-7.15 (m, 6H, Ar), 5.47 (d, 1H, J 5.0, OH), 5.16 (t, 1H, J 9.0,<br />

CHNH), 4.94 (dd, 1H, J 8.5, 5.0, CHOH); 13 C-NMR (DMSO, 75 MHz) δ 164.7<br />

(C=O), 143.6 (C1), 142.5 (ipso-Ph), 141.4 (ipso-Ph), 139.1 (ipso-Ph), 133.3 (ipso-Ph),<br />

219


Experimental for chapter 3.1<br />

128.9, 128.3, 127.9 (para-Ph), 127.7, 127.6, 127.5, 127.0 (para-Ph), 126.8, 126.7,<br />

126.6 (para-Ph), 126.3, 74.5 (CHO), 58.9 (CHN).<br />

Synthesis of 4-cyano-N-((1R*,2S*)-2-hydroxy-1,2-diphenylethyl)benzamide (165g)<br />

Ph<br />

O OH<br />

Ph<br />

i) DMF, (COCl) 2 HO<br />

ii)<br />

O NH<br />

Ph<br />

1<br />

Ph<br />

NH 2<br />

2<br />

CN<br />

OH<br />

3<br />

(±)<br />

4<br />

CN (±)<br />

One drop of DMF was added <strong>to</strong> a stirred solution of para-cyanobenzoic acid (500 mg,<br />

3.4 mmol) and oxalyl chloride (0.33 cm 3 , 3.74 mmol) in CH 2 Cl 2 (5 cm 3 ). Once<br />

effervescence had s<strong>to</strong>pped the solution was allowed <strong>to</strong> stir for 1 hr and the solvent was<br />

removed under reduced pressure. <strong>The</strong> crude acyl chloride in CH 2 Cl 2 (5 cm 3 ) was<br />

added drop wise over a period of 1 hr <strong>to</strong> a stirred solution of amine 174 (586 mg, 2.75<br />

mmol) in CH 2 Cl 2 (20 cm 3 ) and Et 3 N (0.69 cm 3 , 5 mmol) at 0 °C. After warming <strong>to</strong><br />

room temperature, the solution was diluted in CH 2 Cl 2 (10 cm 3 ) and washed with<br />

saturated aqueous sodium bicarbonate (20 cm 3 ), the aqueous extract washed with<br />

further CH 2 Cl 2 (2 x 20 cm 3 ) and the combined organic extracts dried over sodium<br />

sulphate and concentrated under vacuum. <strong>The</strong> resulting orange oil was purified by<br />

flash chroma<strong>to</strong>graphy (4:1 <strong>to</strong> 2:1 petrol:EtOAc) <strong>to</strong> yield amide 165g (480 mg, 41%) as<br />

colourless cubes.<br />

R f : 0.39 (1:1 petrol:EtOAc); Mpt: 199-200 °C (EtOAc); MS m/z (CI+): 343 (90%,<br />

MH + ), 344 (26%, (M+1)H + ), 325 (100%, [M - H 2 O]H + ); HRMS (ESI+) m/z found<br />

343.1434 (MH calcd. 343.1441); IR ν max (film)/cm -1 : 3324 (br, OH), 2232 (m, CH),<br />

1638 (C=O), 1539, 699; 1 H-NMR (CDCl 3 , 500 MHz) δ 7.85 (d, 2H, J 8.0, H2), 7.73<br />

(d, 2H, J 8.0, H3), 7.30-7.22 (m, 6H, Ph), 7.13-7.03 (m, 5H, Ph, NH), 5.45 (dd, 1H, J<br />

8.0, 4.0, CHNH), 5.23 (d, 1H, J 4.0, CHOH); 13 C-NMR (CDCl 3 , 125 MHz) δ 165.2<br />

(C=O), 139.5 (ipso-Ph), 138.2 (ipso-Ph), 136.5 (C1), 132.5 (C2), 128.3, 128.2 (Ph),<br />

128.2 (para-Ph), 128.0 (para-Ph), 127.9, 127.7 (Ph), 126.3 (C3), 117.9 (C4), 115.2<br />

(CN), 76.7 (COH), 59.6 (CNH).<br />

220


Experimental for chapter 3.1<br />

Synthesis of N-((1R,2S)-2-hydroxy-1,2-diphenylethyl)-2-methoxybenzamide (165i)<br />

Ph<br />

O<br />

Cl<br />

OMe<br />

Ph<br />

Ph<br />

NH 2<br />

OH<br />

Et 3 N<br />

HO<br />

O<br />

1<br />

6<br />

5<br />

Ph<br />

NH<br />

OMe<br />

2<br />

3<br />

4<br />

General procedure 1 was used mixing o-anisoyl chloride (0.38 cm 3 , 2.54 mmol) with<br />

the amino alcohol yy (600 mg, 2.80 mmol) and triethylamine (0.71 cm 3 ) <strong>to</strong> give the<br />

amide 165i (880 mg, 99%) as colourless needles.<br />

R f : 0.65 (EtOAc); Mpt: 172-3 °C (EtOAc); [α] 22 D : 100.7 (c = 0.6, EtOH); MS m/z<br />

(CI+): 348 (100%, MH + ), 349 (20%, (M+1)H + ), 330 (22%, [M-H 2 O]H + ); HRMS<br />

(ESI+) m/z found 348.1596 (MH calcd. 348.1594); IR ν max (film)/cm -1 : 3330, 1629<br />

(C=O), 1527; 1 H-NMR (CDCl 3 , 500 MHz) δ 8.75 (d, 1H, J 7.5, NH), 8.21 (dd, 1H, J<br />

8.0, 2.0, H6), 7.46 (ddd, 1H, J 8.0, 7.5, 2.0, H4), 7.28-7.21 (m, 6H, Ar), 7.10-7.02 (m,<br />

5H, Ar), 7.0 (d, 1H, J 8.5, 5.65 (dd, 1H, J 4.0, 7.5, CHNH), 5.17 (d, 1H, J 4.0, CHOH),<br />

3.91 (s, 3H, OMe); 13 C-NMR (CDCl 3 , 125 MHz) δ 165.6 (C=O), 157.6 (C1), 139.5<br />

(ipso-Ph), 137.7 (ipso-Ph), 133.0, 132.4, 132.3, 128.2, 127.6, 127.5, 126.9, 126.7,<br />

121.4, 121.2, 120.9, 111.2, 60.1 (COH), 56.0 (CNH).<br />

Synthesis of (4R,5R)-2,4,5-triphenyloxazoline (101a)<br />

HO<br />

O<br />

Ph<br />

NH<br />

Ph<br />

DIC, Cu(OTf) 2<br />

Ph<br />

O<br />

N<br />

Ph<br />

Δ<br />

Reflux: General procedure 2 was used with benzamide (317 mg, 1.0 mmol), DIC (0.15<br />

cm 3 , 1.0 mmol), Cu(OTf) 2 (22 mg, 0.06 mmol), dioxane (3 cm 3 ) and heated under<br />

reflux for 7 hr at 105 °C. Flash chroma<strong>to</strong>graphy (19:1 petrol:EtOAc) yielded<br />

oxazoline 101a (195 mg, 65%) as colourless needles.<br />

221


Experimental for chapter 3.1<br />

Microwave: General procedure 2 was used with benzamide (160 mg, 0.50 mmol), DIC<br />

(0.08 cm 3 , 0.38 mmol), Cu(OTf) 2 (11 mg, 0.03 mmol), THF (3 cm 3 ) and heated under<br />

microwave irradiation for 20 min at 150 °C. Flash chroma<strong>to</strong>graphy (19:1<br />

petrol:EtOAc) yielded oxazoline 101a (86 mg, 58%) as colourless needles.<br />

R f : 0.51 (4:1 petrol:EtOAc); Mpt: 106-108 ºC (<strong>to</strong>luene) lit. 16 93-95 ºC; [α] 25 D : –11 (c<br />

= 3.0, EtOH); MS m/z (CI+): 300 (100%, MH + ), 301 (21%, (M+1)H + ), 193 (12%, [M-<br />

PhCO] + ); IR ν max (film)/cm -1 : 1650 (C=N), 1602, 1494, 1325; 1 H-NMR (300 MHz,<br />

CDCl 3 ) δ 8.17 (d, 2H, J 7.0, ortho-Ph), 7.60-7.27 (m, 13H, Ph), 5.44 (d, 1H, J 7.5,<br />

OCHPh), 5.26 (d, 1H, J 7.5, NCHPh); 13 C-NMR (75 MHz, CDCl 3 ) δ 164.0 (C=N),<br />

141.9 (ipso-Ph), 140.4 (ipso-Ph), 131.7, 128.9, 128.8, 128.6, 128.4, 128.4, 127.7 (Ph)<br />

127.4 (ipso-Ph), 126.7, 125.7 (Ph), 88.9 (COPh), 79.0 (CNPh); chiral HPLC: Pirkle<br />

Covalent (R,R) Whelk-O1 column, 10% IPA in hexane, 1 cm 3 min -1 , 100%, 6.7 min;<br />

racemic sample: 50% - 6.8 min, 50% - 10.5 min.<br />

Synthesis of (4R*, 5R*)-2,4,5-triphenyloxazoline (101a) and (4R*, 5R*)-2-(4-<br />

methoxyphenyl)-4,5-diphenyloxazoline (101b)<br />

O NH 2<br />

Ph Ph<br />

O<br />

N<br />

Ph Ph<br />

O N<br />

O NH 2<br />

i) (Et 3 O)BF 4<br />

1<br />

Ph<br />

ii)<br />

HO Ph<br />

4<br />

OMe<br />

H 2 N (±)<br />

OMe<br />

±101a ±101b<br />

General procedure 3 was used mixing benzamide (67 mg, 0.55 mmol), para-anisamide<br />

(84 mg, 0.55 mmol) with the triethyloxonium salt (228 mg, 1.20 mmol) before<br />

addition of the α-amino alcohol (280 mg, 1.35 mmol). Purification by flash<br />

chroma<strong>to</strong>graphy (9:1 petrol:EtOAc), and recrystallisation from <strong>to</strong>luene/hexane yielded<br />

oxazoline 101a (140 mg, 85%) as colourless needles and oxazoline 101b (155 mg,<br />

86%) as colourless needles.<br />

101a data as enantiopure (previous page) Chiral HPLC: Pirkle Covalent (R,R) Whelk-<br />

O1 column, 10% IPA in hexane, 1mL/ min: 50% - 6.8 min, 50% - 10.5 min.<br />

2<br />

3<br />

222


Experimental for chapter 3.1<br />

101b data as enantiopure (vide infra) Chiral HPLC: Pircle Covalent (R,R) Whelk-O1<br />

column, 10% IPA in hexane, 1ml/ min: 50% - 11.3 min, 50% - 20.0 min.<br />

Synthesis of (4R, 5R)-2-(4-methoxyphenyl)-4,5-diphenyloxazoline (101b)<br />

HO<br />

O<br />

Ph<br />

NH<br />

Ph<br />

DIC, Cu(OTf) 2<br />

Ph<br />

O<br />

N<br />

Ph<br />

Δ<br />

OMe OMe<br />

Reflux:General procedure 2 was used with benzamide (20.0 mg, 57.6 mmol), DIC<br />

(8.96 cm 3 , 57.6 mmol), Cu(OTf) 2 (1.25 g, 3.50 mmol), dioxane (175 cm 3 ) and heated<br />

under reflux for 12 hr at 120 °C. Flash chroma<strong>to</strong>graphy (9:1 <strong>to</strong> 4:1 petrol:EtOAc)<br />

yielded oxazoline 101b (8.67 g, 46%) as colourless needles.<br />

Microwave:General procedure 2 was used with benzamide (700 mg, 2.01 mmol), DIC<br />

(0.31 cm 3 , 2.01 mmol), Cu(OTf) 2 (44 mg, 0.12 mmol), THF (7 cm 3 ) and heated under<br />

microwave irradiation for 30 min. at 140 °C. Flash chroma<strong>to</strong>graphy (9:1 <strong>to</strong> 4:1<br />

petrol:EtOAc) yielded oxazoline 101b (661 mg, 72%) as colourless needles.<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

Ph<br />

SiO 2 slurry, CH 2 Cl 2<br />

O<br />

1<br />

N<br />

O<br />

N<br />

2<br />

OMe<br />

3<br />

4<br />

OMe<br />

OMe<br />

101b 109b<br />

An excess of silica was added <strong>to</strong> a stirred solution of aziridine 100b (1.38 g, 4.2 mmol)<br />

in CH 2 Cl 2 (20 cm 3 ) and stirred for 8 days. <strong>The</strong> mixture was filtered, concentrated<br />

under vacuum and purified by flash chroma<strong>to</strong>graphy (9:1 <strong>to</strong> 3:1 petrol:EtOAc) <strong>to</strong> yield<br />

oxazoline 101b (800 mg, 58%) as clear cubic crystals, and its diastereomeric oxazoline<br />

109b (7 mg, 1%).<br />

223


Experimental for chapter 3.1<br />

R f : 0.38 (4:1 petrol:EtOAc); Mpt: 98-99 °C (<strong>to</strong>luene); [α] 32 D : –40.8 (c = 1.0, CHCl 3 );<br />

[α] 20 D : –38 (c = 0.5, EtOH); MS m/z (CI+): 330 (100%, MH + ), 331 (21%, (M+1)H + );<br />

HRMS (ESI+) m/z found 330.1488 (MH calcd. 330.1489); Microanalysis: % found<br />

(% calc’d for C 22 H 19 NO 2 ) C, 80.22 (80.00), H, 5.81 (5.81), N 4.25 (4.23); IR<br />

ν max (film)/cm -1 : 1641 (C=N), 1608, 1510, 1254; 1 H-NMR (CD 3 OD, 300 MHz) δ 8.06<br />

(d, 2H, J 9.0, H2), 7.51-7.29 (m, 10H), 7.09 (d, 2H, J 9.0, H3), 5.49 (d, 1H, J 7.5,<br />

CHO), 5.18 (d, 1H, J 7.5, CHN), 3.92 (s, 3H, OMe); 1 H-NMR (CDCl 3 , 300 MHz) δ<br />

8.10 (d, 2H, J 9.0, H2), 7.45-7.31 (m, 10H), 6.99 (d, 2H, J 9.0, H3), 5.40 (d, 1H, J 7.5,<br />

CHO), 5.21 (d, 1H, J 7.5, CHN), 3.89 (s, 3H, OMe); 13 C-NMR (CD 3 OD, 125 MHz) δ<br />

165.4 (C=N) 163.3 (C4), 141.8 (ipso-Ph), 140.2 (ipso-Ph), 130.3, 128.9, 128.8, 128.5,<br />

127.9, 126.7, 125.6 (Ph), 119.0 (C1), 114.0 (C3), 89.5 (CHOPh), 78.5 (CHNPh), 54.8<br />

(OMe); chiral HPLC: Pirkle Covalent (R,R) Whelk-O1 column, 10% IPA in hexane,<br />

1ml min -1 , 100%, 11.7 min; racemic sample: 50% - 11.3 min, 50% - 20.0 min. See<br />

appendix for crystallographic information.<br />

109b characterised separately (vide infra)<br />

Synthesis of (4R,5R)-2-(3-methoxyphenyl)-4,5-diphenyloxazoline (101c)<br />

HO<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

NH<br />

DIC, Cu(OTf) 2<br />

O<br />

N<br />

Δ<br />

6<br />

1<br />

2<br />

OMe<br />

5<br />

4<br />

3<br />

OMe<br />

General procedure 2 was used with benzamide 165c (195 mg, 0.56 mmol), DIC (0.09<br />

cm 3 , 0.56 mmol), Cu(OTf) 2 (12 mg, 0.03 mmol), dioxane (2 cm 3 ) and heated under<br />

reflux for 17 hr. Flash chroma<strong>to</strong>graphy (4:1 petrol:EtOAc) yielded oxazoline 101c (71<br />

mg, 39%) as colourless needles.<br />

R f : 0.38 (4:1 petrol:EtOAc); Mpt: 92-93 °C (PhMe); [α] 21 D : –25.0 (c = 0.4, EtOH);<br />

MS m/z (CI+): 330 (100%, MH + ), 331 (23%, (M+1)H + ), 223 (23%); HRMS (ESI+)<br />

m/z found 330.1495 (MH calcd. 330.1489); IR ν max (film)/cm -1 : 1646 (C=N), 1582,<br />

1452, 1321, 1039; 1 H-NMR (CDCl 3 , 300 MHz) δ 7.75 (dt, 1H, J 8.0, 1.0, H6), 7.71-<br />

7.69 (m, 1H, H2), 7.17-7.06 (m, 11H, Ph, H5), 7.11 (ddd, 1H, J 8.0, 2.5, 1.0, H4), 5.43<br />

224


Experimental for chapter 3.1<br />

(d, 1H, J 7.5, CHO), 5.25 (d, 1H, J 7.5, CHN), 3.88 (s, 3H, OMe); 13 C-NMR (CDCl 3 ,<br />

75 MHz) δ 163.9 (C=N), 159.5 (C3), 141.8 (ipso-Ph), 140.3 (ipso-Ph), 129.4, 128.9,<br />

128.8 (Ar), 128.6 (C1), 128.4, 127.7, 126.7, 125.6 (Ar), 121.0 (C4), 118.5 (C6), 112.7<br />

(C2), 88.9 (CHO), 78.9 (CHN), 55.4 (OMe).<br />

Synthesis of (4R*,5R*)-2-(3-fluorophenyl)-4,5-diphenyloxazoline (101d)<br />

Ph<br />

Ph<br />

O NH 2<br />

Ph<br />

F<br />

i) (Et 3 O)BF 4<br />

ii)<br />

Ph<br />

NH 2<br />

OH (±)<br />

6<br />

5<br />

O<br />

4<br />

N<br />

1<br />

2<br />

3<br />

F<br />

(±)<br />

General procedure 3 was used mixing meta-fluorobenzamide (266 mg, 1.91 mmol)<br />

with the triethyloxonium salt (400 mg, 2.10 mmol) stirring for 14 hr, before addition of<br />

the α-amino alcohol (490 mg, 2.30 mmol) and reflux for 24 hr. Purification by flash<br />

chroma<strong>to</strong>graphy (9:1 petrol:EtOAc), yielded oxazoline 101d (510 mg, 82%) as clear<br />

needles.<br />

R f : 0.29 (9:1 petrol:EtOAc); Mpt: 63-64 °C (PhMe); MS m/z (CI+): 318 (100%,<br />

MH + ), 319 (19%, (M+1)H + ), 211 (63%, [M-PhCHO]H + ); HRMS (ESI+) m/z found<br />

318.1290 (MH calcd. 318.1289); IR ν max (film)/cm -1 : 3031 (w), 1651 (C=N), 1588,<br />

1490 (m), 1453, 1321 (m), 1271 (m), 1185; 1 H-NMR (CDCl 3 , 500 MHz) δ 7.93 (d,<br />

1H, J 8.0, H2), 7.83 (dd, 1H, J 9.5, 1.5, H4), 7.49-7.28 (m, 11H, Ar), 7.27-7.22 (m,<br />

1H, Ar), 5.44 (d, 1H, J 7.5, CHO), 5.25 (d, 1H, J 7.5, CHN); 13 C-NMR (CDCl 3 , 125<br />

MHz) δ 163.0 (C=N), 162.6 (d, J 245, C-F), 141.6 (ipso-Ph), 140.1 (ipso-Ph), 130.2 (d,<br />

J 8, C1 or C5), 129.6 (d, J 8, C1 or C5), 129.1, 128.9, 128.0, 127.8, 126.8, 125.9,<br />

125.6, 124.6, 124.1, 118.9, 115.8 (d, J 24, C2 or C4), 115.3 (d, J 24, C2 or C4), 89.2<br />

(CHO), 78.9 (CHN).<br />

225


Experimental for chapter 3.1<br />

Synthesis of (4R*,5R*)-2-(4-cyanophenyl)-4,5-diphenyloxazoline (101g)<br />

HO<br />

O<br />

Ph<br />

NH<br />

Ph<br />

DIC, Cu(OTf) 2<br />

Δ<br />

Ph<br />

O<br />

Ph<br />

N<br />

1<br />

2<br />

CN<br />

(±)<br />

4<br />

CN<br />

3<br />

(±)<br />

General procedure 2 was used with benzamide (340 mg, 1.0 mmol), DIC (0.16 cm 3 ,<br />

1.0 mmol), Cu(OTf) 2 (21 mg, 0.06 mmol), THF (3 cm 3 ) and heated under microwave<br />

irradiation for 20 min. at 150 °C. Flash chroma<strong>to</strong>graphy (9:1 petrol:EtOAc) yielded<br />

oxazoline 101g (170 mg, 53%) as colourless needles.<br />

R f : 0.30 (4:1 petrol:EtOAc); Mpt: 134 °C (PhMe); MS m/z (CI+): 325 (100%, MH + ),<br />

326 (38%, (M+1)H + ), 130 (14%); IR ν max /cm -1 : 2934 (m), 2229 (w, CN), 1628 (C=N),<br />

1527, 1317 (m); 1 H-NMR (CDCl 3 , 400 MHz) δ 8.23 (d, 2H, J 7.0, H2), 7.76 (d, 2H, J<br />

7.0, H3), 7.44-7.25 (m, 10H, Ph), 5.46 (d, 1H, J 8.0, OCH), 5.27 (d, 1H, J 8.0, NCH);<br />

13 C-NMR (CDCl 3 , 100 MHz) δ 162.5 (C=N), 141.3 (ipso-Ph), 139.8 (ipso-Ph), 132.3<br />

(C3) 131.6 (C1), 129.2 (C2), 129.1, 129.0 (Ph), 128.8 (para-Ph), 128.1 (para-Ph),<br />

126.7, 125.8 (Ph), 118.3 (C4), 115.1 (C≡N), 89.6 (HCO), 79.1 (HCN).<br />

Synthesis of (4R*,5R*)-2-(4-nitrophenyl)-4,5-diphenyloxazoline (101h)<br />

Ph<br />

Ph<br />

O NH 2<br />

i) (Et 3 O)BF 4<br />

O N<br />

ii)<br />

Ph<br />

1<br />

2<br />

Ph<br />

NH<br />

NO 2<br />

2<br />

3<br />

OH (±)<br />

4<br />

NO 2 (±)<br />

General procedure 3 was used mixing para-nitrobenzamide (300 mg, 1.81 mmol) with<br />

the triethyloxonium salt (378 mg, 2.00 mmol) stirring for 19 hr, before addition of the<br />

amino alcohol (462 mg, 2.17 mmol) and reflux for 21 hr. Purification by flash<br />

chroma<strong>to</strong>graphy (19:1 <strong>to</strong> 9:1 petrol:EtOAc), yielded oxazoline 101h (340 mg, 55%) as<br />

colourless flowers.<br />

226


Experimental for chapter 3.1<br />

R f : 0.41 (4:1 petrol:EtOAc); Mpt: 121-122 °C (EtOAc), 118-120 °C (PhMe); MS m/z<br />

(CI+): 345 (100%, MH + ), 346 (20%, (M+1)H + ), 238 (6%); HRMS (ESI+) m/z found<br />

345.1237 (MH calcd. 345.1234); IR ν max (film)/cm -1 : 1648 (C=N), 1598, 1527, 1494<br />

(NO 2 ), 1347 (NO 2 ); 1 H-NMR (CDCl 3 , 300 MHz) δ 8.32 (d, 2H, J 3.0, H2), 8.30 (d,<br />

2H, J 3.0, H3), 7.44-7.33 (m, 8H, Ar), 7.31 (d, 1H, J 2.0, ortho-Ph), 7.28 (t, 1H, J 1.5,<br />

para-Ph), 5.49 (d, 1H, J 8.0, HCO), 5.30 (d, 1H, J 8.0, HCN); 13 C-NMR (CDCl 3 , 75<br />

MHz) δ 162.1 (C=N), 149.7 (C4), 141.1 (ipso-Ph), 139.6 (ipso-Ph), 133.2 (C1), 129.6,<br />

129.0, 129.0, 128.9 (Ph), 128.7 (para-Ph), 128.0 (para-Ph), 126.6, 125.7 (Ph), 123.6<br />

(Ph), 89.6 (CHO), 79.0 (CHN).<br />

Synthesis of (4R,5R)-2-(2-methoxyphenyl)-4,5-diphenyloxazoline (101i)<br />

HO<br />

O<br />

Ph<br />

NH<br />

Ph<br />

DIC, Cu(OTf) 2<br />

Ph<br />

O<br />

N<br />

Ph<br />

OMe Δ<br />

1<br />

6<br />

5<br />

4<br />

2<br />

3<br />

OMe<br />

General procedure 2 was used with benzamide (890 mg, 2.56 mmol), DIC (0.40 cm 3 ,<br />

2.56 mmol), Cu(OTf) 2 (56 mg, 0.15 mmol), dioxane (9 cm 3 ) and heated under reflux<br />

for 18 hr at 120 °C. Flash chroma<strong>to</strong>graphy (4:1 petrol:EtOAc) yielded oxazoline 101i<br />

(420 mg, 50%) as colourless needles.<br />

R f : 0.36 (3:1 petrol:EtOAc); Mpt: 79-81 °C (PhMe); [α] 21 D : –13 (c = 0.3, EtOH); MS<br />

m/z (CI+): 330 (100%, MH + ), 331 (23%, (M+1)H + ), 223 (14%, [M-PhCHO]H + );<br />

HRMS (ESI+) m/z found 330.1488 (MH calcd. 330.1489); IR ν max (film)/cm -1 : 1654<br />

(C=O), 1595, 1060; 1 H-NMR (CDCl 3 , 300 MHz) δ 7.95 (dd, 1H, J 8.0, 2.0, H6), 7.49<br />

(td, 1H, J 8.5, 2.0, H4), 7.44-7.39 (m, 5H, Ph), 7.39-7.36 (m, 3H, Ph), 7.35-731 (m,<br />

2H, Ph), 7.08-7.01 (m, 2H, H3, H5), 5.40 (d, 1H, J 7.0, CHO), 5.28 (d, 1H, J 7.0,<br />

CHN), 3.95 (s, 3H, OMe); 13 C-NMR (CDCl 3 , 75 MHz) δ 162.9 (C=N), 158.7 (C2),<br />

142.2 (ipso-Ph), 140.7 (ipso-Ph), 132.4 (C4), 131.3 (C6), 128.7, 128.6, 128.1, 127.5,<br />

126.6, 125.5 (Ar), 120.2 (C5), 116.9 (C1), 111.7 (C3), 88.1 (CHO), 79.0 (CHN), 55.9<br />

(OMe).<br />

227


Experimental for chapter 3.1<br />

Synthesis of (4R,5R)-2-(3-hydroxylphenyl)-4,5-diphenyloxazoline (101k) &<br />

(4R,5R)-2-(3-(allyloxy)phenyl)-4,5-diphenyloxazoline (101j)<br />

Ph Ph<br />

Ph Ph<br />

O<br />

OH<br />

OH<br />

HN<br />

Ph<br />

Ph<br />

EDC.HCl<br />

SiO 2 , CH 2 Cl 2<br />

rt, 30 hr<br />

O<br />

N<br />

OH<br />

AllylBr, K 2 CO 3<br />

DMF, NaI<br />

O<br />

1<br />

6<br />

5<br />

4<br />

N<br />

2<br />

3<br />

O<br />

101k<br />

101j<br />

EDC.HCl (382 mg, 2 mmol) was added <strong>to</strong> a stirred solution of aziridine (195 mg, 1<br />

mmol), silica (2 g) and 3-hydroxybenzoic acid (207 mg, 1.5 mmol) in CH 2 Cl 2 (10<br />

cm 3 ). <strong>The</strong> solvent was removed after 32 hr and the resulting residue partitioned<br />

between water (10 cm 3 ) and CH 2 Cl 2 (30 cm 3 ). <strong>The</strong> aqueous phase was washed with<br />

further CH 2 Cl 2 (3 x 30 cm 3 ) and the combined organic phases dried over sodium<br />

sulphate, before purification by flash chroma<strong>to</strong>graphy (4:1 petrol:EtOAc) <strong>to</strong> give<br />

phenol 101k (180 mg, 57%) and starting materials (20%).<br />

Adapted from the method of Ishizaki, 17 allyl bromide (83 µl, 0.95 mmol) was added <strong>to</strong><br />

a solution of phenol 101k (200 mg, 0.63 mmol), sodium iodide (9 mg, 0.06 mmol),<br />

potassium carbonate (173 mg, 1.26 mmol) in DMF (7 cm3) and stirred for 16 hr.<br />

Water (2 cm 3 , mild exotherm) was added and air blown of the stirred reaction mixture<br />

for a further 2 hr before the mixture was concentrated, partitioned between water (10<br />

cm 3 ) and EtOAc (40 cm 3 ) and the aqueous phase washed with CH 2 Cl 2 (3 x 30 cm 3 )<br />

and the combined organic phases dried over sodium sulphate. Purification by flash<br />

chroma<strong>to</strong>graphy (70% <strong>to</strong>luene in petrol) <strong>to</strong> give oxazoline 101j (75 mg, 38%).<br />

101k R f : 0.12 (4:1, petrol:EtOAc); MS m/z (ES-) 314 (100%, [M-H] - ), 315 (20%,<br />

[(M+1)-H] - ); HRMS: found 338.1143, MNa requires 338.1138; ¹H-NMR (CDCl 3 , 500<br />

MHz) δ 7.63-7.60 (m, 2H, H2, H6), 7.42-7.25 (m, 11H, Ar), 7.00-6.97 (m, 1H, H4),<br />

5.42 (d, 1H, J 7.5, CHOPh), 5.23 (d, 1H, J 7.5, CHNPh); ¹³C-NMR (CDCl 3 , 75.5<br />

MHz) δ 164.6 (C=N), 156.3 (C-OH), 141.6 (ipso-Ph), 140.1 (ipso-Ph), 129.8, 128.9,<br />

128.9, 128.5, 128.2, 127.9, 126.7, 125.6 (Ar), 120.6 (C2 or C6), 119.4 (C4), 115.5 (C2<br />

or C6), 89 (CHOPh), 78.4 (CHNPh).<br />

228


Experimental for chapter 3.1<br />

101j R f : 0.20 (9:1, petrol:EtOAc); [α] 24 D : –22.3 (c = 1.7, CHCl 3 ); MS m/z (ES+) 356<br />

(27%), 378 (100%), 379 (29%); HRMS: found 378.1453, MNa requires 378.1465; IR<br />

ν max (film)/cm⎯¹ 1992 (w), 1649 (C=N), 1582 (m, C=C), 1448 (m); ¹H-NMR (CDCl 3 ,<br />

500 MHz) δ 7.74 (d, 1H, J 8.0, Ar), 7.71-7.69 (m, 1H, H2), 7.44-7.31 (m, 11H, Ar),<br />

7.13 (dd, 1H, J 8.0, 2.0, H5), 6.13-6.04 (m, 1H, H8), 5.48-5.41 (m, 2H, CHOPh, H9),<br />

5.31 (d, 1H, J 9.5, H9), 5.24 (d, 1H, J 7.5, CHNPh), 4.61 (d, 2H, J 5.0, H7); ¹³C-NMR<br />

(CD 3 OD, 75.5 MHz) δ 166.3 (C=N), 160.2 (C3), 142.6 (ipso-Ph), 141.1 (ipso-Ph),<br />

134.5, 131.0, 130.1, 130.0, 129.8, 129.3, 129.2, 127.9, 126.8 (Ar), 122.1 (CH), 120.3<br />

(CH), 117.8 (CH 2 ), 115.2 (CH), 90.8 (CHOPh), 79.7 (CHNPh), 69.9 (CH 2 ).<br />

Synthesis of (4R*,5R*)-2-cyclohexyl-4,5-diphenyloxazoline (101m)<br />

Ph<br />

Ph<br />

i) (Et 3 O)BF 4<br />

(±)<br />

O NH 2<br />

HO Ph<br />

ii)<br />

Ph<br />

O<br />

N<br />

H 2 N<br />

(±)<br />

General procedure 3 was used mixing cyclohexanecarboxamide (500 mg, 3.92 mmol)<br />

with the triethyloxonium salt (860 mg, 4.5 mmol) stirring for 20 hr, before addition of<br />

the α-amino alcohol (500 mg, 2.35 mmol) and reflux for 16 hr. Purification by flash<br />

chroma<strong>to</strong>graphy (9:1 <strong>to</strong> 4:1 petrol:EtOAc), yielded oxazoline 101m (1.12 g, 93%) as a<br />

white wax.<br />

R f : 0.44 (4:1, petrol:EtOAc); MS m/z (CI+) 306 (100%, MH + ), 307 (22%, (M+1)H + );<br />

HRMS: found 306.1855, MH requires 306.1852; IR ν max (film)/cm⎯¹ 2930 (C-H),<br />

1663 (C=N), 1450 (m); ¹H-NMR (CDCl 3 , 500 MHz) δ 7.43-7.35 (m, 5H, Ph), 7.34-<br />

7.26 (m, 3H, Ph), 7.25-7.21 (m, 2H, Ph), 5.23 (d, 1H, J 7.0, CHOPh), 5.03 (d, 1H, J<br />

7.0, CHNPh), 2.67-2.56 (m, 1H, CH), 2.19-2.07 (m, 2H), 1.90-1.82 (m, 2H), 1.80-1.59<br />

(m, 3H), 1.46-1.18 (m, 3H); ¹³C-NMR (CDCl 3 , 125 MHz) δ 171.5 (C=N), 142.4 (ipso-<br />

Ph), 140.1 (ipso-Ph), 128.9 (meta-Ph), 128.8 (meta-Ph), 128.4 (para-Ph), 127.7 (para-<br />

Ph), 126.5 (ortho-Ph), 125.5 (ortho-Ph), 88.3 (CHOPh), 78.3 (CHNPh), 37.5 (CH),<br />

30.0, 29.9, 25.8, 25.6.<br />

229


Experimental for chapter 3.1<br />

Synthesis of (4S,5S)-4-(methoxymethyl)-2-(4-methoxyphenyl)-5-phenyloxazoline<br />

(104b)<br />

Ph OMe<br />

O NH 2<br />

i) (Et 3 O)BF 4<br />

O N<br />

ii) Ph<br />

1<br />

HO<br />

2<br />

OMe<br />

H 2 N<br />

OMe<br />

3<br />

4<br />

OMe<br />

General procedure 3 was used mixing p-anisamide (348 mg, 2.30 mmol) with the<br />

triethyloxonium salt (524 mg, 2.76 mmol) before addition of the α-amino alcohol (542<br />

mg, 2.99 mmol). Purification by flash chroma<strong>to</strong>graphy (9:1 petrol:EtOAc) yielded<br />

oxazoline 104b (493 mg, 72%) as colourless flowers.<br />

R f : 0.18 (4:1 petrol:EtOAc); Mpt: 60-61 °C from (CH 2 Cl 2 ); [α] 23 D : –94 (c = 0.4,<br />

EtOH); MS m/z (CI+): 298 (100%, MH + ), 299 (17%, (M+1)H + ); HRMS (ESI+) m/z<br />

found 298.1439 (MH calcd. 298.1438); IR ν max (film)/cm -1 : 1648 (s, C=N), 1609 (s),<br />

1512 (s), 1252 (s); 1 H-NMR (CDCl 3 , 300 MHz) δ 7.99 (d, 2H, J 9.0, ortho-Ph), 7.39-<br />

7.30 (m, 5H, Ph), 6.94 (d, 2H, J 9.0, meta-Ph), 5.46 (d, 1H, J 7.0, CHPh), 4.30 (td, 1H,<br />

J 6.5, 4.5, CHN), 3.86 (s, 3H, ArOMe), 3.73 (dd, 1H, J 9.5, 3.5, CH a H b ), 3.61 (dd, 1H,<br />

J 9.5, 6.5, CH a H b ), 3.44 (s, 3H, CH 2 OMe); 13 C-NMR (CDCl 3 , 75 MHz) δ 164.2<br />

(CNO), 162.5 (C4), 141.3 (ipso-Ph), 130.5, 129.0, 128.4, 125.8 (Ar CH), 120.3 (C1),<br />

114.0 (meta-CH), 83.8 (CHPh), 75.2 (CH 2 ), 74.8 (CHN), 59.6, 55.6 (OMe).<br />

230


Experimental for chapter 3.1<br />

Synthesis of (4R,5S)-2,4,5-triphenyloxazoline (109a) and (4R, 5S)-2-(4-<br />

methoxyphenyl)-4,5-diphenyloxazoline (109b)<br />

Ph Ph<br />

O NH 2<br />

O N<br />

Ph Ph<br />

O N<br />

i) (Et 3 O)BF 4<br />

109b<br />

OMe<br />

ii)<br />

O NH 2<br />

OMe<br />

HO<br />

Ph<br />

H 2 N<br />

Ph<br />

109a<br />

1<br />

4<br />

2<br />

3<br />

General procedure 3 was used mixing benzamide (89 mg, 0.74 mmol) para-anisamide<br />

(112 mg, 0.74 mmol) with the triethyloxonium salt (265 mg, 1.39 mmol), stirring for<br />

27 hr, before addition of the α-amino alcohol (350 mg, 1.5 mmol) and reflux for 24 hr.<br />

Purification by flash chroma<strong>to</strong>graphy (9:1 petrol:EtOAc), and recrystallisation from<br />

<strong>to</strong>luene/hexane yielded oxazoline 109a (155 mg, 70%) as clear colourless flowers and<br />

anisole 109b (160 mg, 66%) as colourless needles.<br />

109a R f : 0.41 (4:1 petrol:EtOAc); Mpt: 134-135 °C (<strong>to</strong>luene); [α] 25 D : +159 (c = 0.2,<br />

EtOH); MS m/z (CI+): 300 (100%, MH + ), 301 (20%, (M+1)H + ); HRMS (ESI+) m/z<br />

found 300.1387 (MH calcd. 300.1383); IR ν max (film)/cm -1 : 1643 (C=N), 1451, 1269;<br />

1 H-NMR (CDCl 3 , 500 MHz) δ 8.21 (d, 2H, J 7.0, ortho-Ph), 7.60 (tt, 1H, J 8.5, 2.0,<br />

para-Ph), 7.55-7.51 (m, 2H, Ph), 7.11-7.02 (m, 6H, Ph), 7.00-6.95 (m, 4H, Ph), 6.0 (d,<br />

1H, J 10.0, CHO), 5.79 (d, 1H, J 10.0, CHN); 13 C-NMR (CDCl 3 , 75 MHz) δ 164.9<br />

(CNO), 137.7 (ipso-Ph), 136.6 (ipso-Ph), 131.8, 128.6, 128.6, 127.9, 127.7, 127.6,<br />

127.5 (ipso-Ph), 127.4, 127.0, 126.3 (Ph), 85.3 (COPh), 74.5 (CNPh).<br />

109b R f : 0.23 (4:1 petrol:EtOAc); Mpt: 126 °C (<strong>to</strong>lene/petrol); [α] 20 D : +162 (c = 0.45<br />

EtOH); MS m/z (CI+): 330 (100%, MH + ), 331 (23%, (M+1)H + ); HRMS (ESI+) m/z<br />

found 330.1492 (MH calcd. 330.1489); IR ν max (film)/cm -1 : 1644 (C=N), 1608, 1511,<br />

1255; 1 H-NMR (MeOD, 300 MHz) δ 8.07 (d, 2H, J 9.0, H2), 7.12-6.92 (m, 12H, Ph),<br />

6.12 (d, 1H, J 10.0, CHO), 5.75 (d, 1H, J 10.0, CHN), 3.90 (s, 3H, OMe); 13 C-NMR<br />

(CDCl 3 , 125 MHz) δ 164.7 (CO), 162.5 (C4), 137.9 (ipso-Ph), 136.7 (ipso-Ph), 130.3,<br />

127.9, 127.6, 127.6, 126.3, 127.3, 126.9, 119.9 (C1), 113.9, 85.1 (COPh), 74.3<br />

(CNPh), 55.4 (OMe).<br />

231


Experimental for chapter 3.1<br />

Synthesis of (S)-4-isopropyl-2-phenyloxazoline (111a)<br />

O NH 2 i) (Et 3 O)BF 4<br />

ii)<br />

HO<br />

H 2 N<br />

O<br />

N<br />

General procedure 3 was used mixing benzamide (400 mg, 3.30 mmol) with the<br />

triethyloxonium salt (690 mg, 3.63 mmol) stirring for 24 hr, before addition of the<br />

amino alcohol (0.44 cm 3 , 3.96 mmol) and reflux for 21 hr. Purification by flash<br />

chroma<strong>to</strong>graphy (9:1 petrol:EtOAc), yielded oxazoline 111a (510 mg, 82%) as a clear<br />

oil.<br />

R f : 0.44 (4:1 petrol:EtOAc); [α] 24 D : –46 (c = 0.6, EtOH); MS m/z (CI+): 190 (100%,<br />

MH + ), 191 (9%, (M+1)H + ); HRMS (ESI+) m/z found 190.1227 (MH calcd. 190.1226);<br />

IR ν max (film)/cm -1 : 2960 (C-H), 1649 (C=N), 1450 (w), 1353 (m); 1 H-NMR (CDCl 3 ,<br />

300 MHz) δ 7.99-7.92 (m, 2H, ortho-Ph), 7.50-7.35 (m, 3H, Ph), 4.45-4.35 (m, 1H,<br />

CHN), 4.17-4.04 (m, 2H, CH 2 ), 1.93-1.79 (m, 1H, CHMe 2 ), 1.03 (d, 3H, J 7.0,<br />

CHMe a Me b ), 0.92 (d, 3H, J 7.0, CHMe a Me b ); 13 C-NMR (CDCl 3 , 75 MHz) δ 163.3<br />

(C=O), 131.1, 128.2, 128.2 (Ar), 127.8 (ipso-Ph), 72.5 (CO), 70.0 (CN), 32.8<br />

(CHMe 2 ), 18.9 (CHMe a Me b ), 18.0 (CHMe a Me b ).<br />

Synthesis of (S)-4-isopropyl-2-(4-methoxyphenyl)oxazoline (111b)<br />

O NH 2<br />

i) (EtO) 3 BF 4<br />

O<br />

N<br />

OMe<br />

1<br />

ii)<br />

HO<br />

4<br />

H 2 N<br />

OMe<br />

2<br />

3<br />

General procedure 3 was used mixing p-anisamide (451 mg, 2.98 mmol) with the<br />

triethyloxonium salt (651 mg, 3.43 mmol) and stirred for 26 hr before addition of the<br />

α-amino alcohol (400 mg, 3.88 mmol) and refluxed for 16 hr. Purification by flash<br />

chroma<strong>to</strong>graphy (4:1 petrol:EtOAc) yielded oxazoline 111b (382 mg, 58%) as a clear<br />

oil.<br />

232


Experimental for chapter 3.1<br />

R f : 0.52 (2:1 petrol:EtOAc); [α] 22 D : –40.8 (c = 1.5); MS m/z (CI+): 220 (100%, MH + ),<br />

221 (10%, (M+1)H + ); HRMS (ESI+) m/z found 220.1330 (MH calcd. 220.1332); IR<br />

ν max (film)/cm -1 : 2961 (m, C–H), 1645 (C=N), 1610, 1512, 1258 (C–Me); 1 H-NMR<br />

(CDCl 3 , 500 MHz) δ 7.87 (d, 2H, J 9.0, H2), 6.88 (d, 2H, J, 9.0, H3), 4.39-4.29 (m,<br />

1H, CH A H B ), 4.10-4.01 (m, 2H, CH A H B & CHN), 3.80 (s, 3H, OMe), 1.82 (oct, 1H, J<br />

6.5, CHMe 2 ), 1.00 (d, 3H, J 7.0, CHMe A Me b ), 0.89 (d, 3H, J 7.0, CHMe a Me B ); 13 C-<br />

NMR (CDCl 3 , 125 MHz) δ 163.0 (C=O), 161.8 (C1, 129.8 (C2), 120.4 (C4), 113.5<br />

(C3), 72.4 (CHN), 69.9 (OCH 2 ), 55.2 (OMe), 32.8 (CHMe 2 ), 18.9 (CHMe A Me b ), 18.0<br />

(CHMe a Me B );<br />

Synthesis of N-((1R,2S)-1-hydroxy-1-phenylpropan-2-yl)benzamide (166)<br />

Ph<br />

O<br />

Cl<br />

Ph<br />

Me<br />

NH 2<br />

HO<br />

O<br />

Me<br />

NH<br />

OH<br />

Et 3 N<br />

1<br />

2<br />

3<br />

4<br />

General procedure 3 was used mixing benzoyl chloride (0.32 cm 3 , 2.76 mmol), (–)-<br />

norepedrine (500 mg, 3.31 mmol) and triethylamine (10 cm 3 ) <strong>to</strong> give the amide 166<br />

(700 mg, 99%) as clear colourless cubes.<br />

R f : 0.21 (2:1 petrol:EtOAc); Mpt: 164-165 °C (ace<strong>to</strong>ne); [α] 22 D : +32 (c = 0.2, EtOH);<br />

MS m/z (CI+): 256 (100%, MH + ) 257 (14%, (M+1)H + ); HRMS (ESI+) m/z found<br />

256.1336 (MH + , calcd. 256.1332); IR ν max (film)/cm -1 : 3286 (OH), 1635 (C=N), 1543<br />

(C–Me); 1 H-NMR (CDCl 3 , 300 MHz) δ 7.84-7.76 (m, 2H, H2), 7.60-7.32 (m, 8H, Ph),<br />

6.33 (d, 1H, J 7.5, NH), 5.30 (d, 1H, J 3.0, CHPh), 4.60 (dqd, 1H, J 7.5, 7.0, 3.0<br />

CHMe), 1.17 (d, 3H, J 7.0, Me); 13 C-NMR (CDCl 3 , 125 MHz) δ 168.5 (CO), 141.0<br />

(ipso-Ph), 134.6 (ipso-Ph), 132.1, 129.1, 129.0, 128.7, 128.0, 127.4, 126.8, 126.8,<br />

126.7 (Ph), 51.8 (CNH), 12.2 (Me). COH under solvent peak by HMQC.<br />

233


Experimental for chapter 3.1<br />

Synthesis of (4S,5S)-4-methyl-2,5-diphenyloxazoline (110)<br />

HO<br />

O<br />

Ph<br />

NH<br />

Me<br />

DIC, Cu(OTf) 2<br />

Ph<br />

O<br />

Me<br />

N<br />

Δ<br />

General procedure 3 was used with benzamide (200 mg, 0.78 mmol), DIC (0.12 cm 3 ,<br />

0.78 mmol), Cu(OTf) 2 (18 mg, 0.05 mmol), THF (3 cm 3 ) and heated under microwave<br />

irradiation for 5 min at 150 °C. Flash chroma<strong>to</strong>graphy (4:1 petrol:EtOAc) yielded an<br />

inseparable mixture of oxazoline 110 and its diastereomer (195 mg, 65%, 95:5) as<br />

colourless needles.<br />

R f : 0.59 (2:1 petrol:EtOAc); MS m/z (CI+): 238 (100%, MH + ), 239 (18%, (M+1)H + ),<br />

131 (51%, [M-PhCHO] + ); HRMS (ESI+) m/z found 238.1224 (MH calcd. 238.1226);<br />

IR ν max (film)/cm -1 : 2926 (C-H), 1648 (C=N), 1450, 1269; 1 H-NMR data for major<br />

compound (CDCl 3 , 300 MHz) δ 8.07-8.00 (m, 2H, ortho-Ph), 7.54-7.25 (m, 8H, Ph),<br />

5.11 (d, 1H, J 8.0, CHPh), 4.22 (quin, 1H, J 7.0, CHMe), 1.50 (d, 3H, J 6.5, Me); 13 C-<br />

NMR (75 MHz, CDCl 3 ) δ 164.2 (C=N), 140.2 (ipso-Ph), 131.7, 128.9, 128.8, 128.6,<br />

128.4, 127.7 (Ph) 127.4 (ipso-Ph), 126.7, 125.7 (Ph), 86.2 (CHOPh), 63.3 (CHNMe),<br />

22.7 (Me).<br />

234


Experimental for chapter 3.2<br />

5.4 Experimental Procedures for Chapter 3.2<br />

(4S,5S)-4-((4R,5R)-4,5-diphenyloxazolinyl)-5-isopropyl-4-methylcyclohex-2-enone<br />

(201)<br />

Ph Ph<br />

Ph Ph<br />

O<br />

N<br />

O<br />

N<br />

SiO 2 , CH 2 Cl 2<br />

6<br />

1<br />

2<br />

5<br />

3<br />

4<br />

OMe<br />

O<br />

Silica (7.00 g) was added <strong>to</strong> a stirred solution of enol ether 102a (0.70 g, 1.81 mmol) in<br />

CH 2 Cl 2 (20 cm 3 ). Upon completion (36 hr) the mixture was filtered with EtOAc and<br />

the filtrate concentrated under vacuum <strong>to</strong> give enone 201 (0.67 mg, 100%) as a yellow<br />

oil.<br />

R f : 0.21 (4:1 petrol:EtOAc); [α] 22 D : +118 (c = 1.3, CHCl 3 ); MS m/z (CI+): 374 (100%,<br />

MH + ), 375 (27%, (M+1)H + ); HRMS (ESI+) m/z found 374.2110 (MH calcd.<br />

374.2115); IR ν max (film)/cm -1 : 2960, 1682 (C=O), 1659 (C=N), 1091 (m); ¹H NMR<br />

(CDCl 3 , 400 MHz) δ 7.43-7.15 (m, 10H, Ph), 7.11 (d, 1H, J 10.5, H6), 6.06 (d, 1H, J<br />

10.5, H5), 5.21 (d, 1H, J 9.5, CHO), 5.09 (d, 1H, J 9.5, CHN), 2.73 (dd, 1H, J 17.0,<br />

8.0, H3 A ), 2.58 (dd, 1H, J 17.0, 5.0, H3 B ), 2.27-2.20 (m, 2H, H2, CHMe 2 ), 1.67 (s, 3H,<br />

Me), 1.02 (d, 3H, J 7.0, CHMe A Me B ), 0.90 (d, 3H, J 7.0, CHMe A Me B ); ¹³C NMR<br />

(CDCl 3 , 100 MHz) δ 199.5 (C=O), 168.5 (C=N), 153.0 (C6), 141.0 (ipso-Ph), 139.2<br />

(ipso-Ph), 128.9, 128.7, 128.5 (C5), 128.0 (para-Ph), 127.7 (para-Ph), 126.5, 125.8,<br />

89.5 (CHO), 78.1 (CHN), 48.3 (C2), 42.3 (C1), 34.5 (C3), 28.4 (CHMe 2 ), 25.6 (Me),<br />

23.0 (CHMe A Me B ), 18.4 (CHMe A Me B ).<br />

235


Experimental for chapter 3.2<br />

Synthesis of N-(1,2-diphenylethyl)cyclohexanecarboxamide (204) and N-<br />

((1R*,2R*)-2-hydroxy-1,2-diphenylethyl)cyclohexanecarboxamide (205)<br />

Ph<br />

O<br />

N<br />

Ph<br />

O<br />

H<br />

N<br />

Ph<br />

Ph<br />

+<br />

O<br />

H<br />

N<br />

Ph<br />

OH<br />

Ph<br />

H 2<br />

204 205<br />

H-cube: A solution of oxazoline 101m (10 mg) in the stated solvent (1 cm 3 ) was<br />

passed thorough the H-cube (1 cm 3 /min, temperature & cartridge as stated) and the<br />

eluent collected for 15 min. <strong>The</strong> solvent was removed by rotary evaporation and<br />

products purified by flash chroma<strong>to</strong>graphy (9:1 <strong>to</strong> 4:1 EtOAc:petrol) <strong>to</strong> give amide 204<br />

as colourless needles and hydroxyamide 205 as a colourless oil (see text).<br />

Bomb: <strong>The</strong> bomb was charge with a solution of oxazoline 101m (20 mg) and catalyst<br />

(2 mg) in the stated solvent (2 cm 3 ), backfilled with hydrogen <strong>to</strong> the stated pressure<br />

and stirred overnight (c. 14 hr). <strong>The</strong> pressure was released, catalyst filtered under<br />

nitrogen, the solvent was removed by rotary evaporation and products purified by flash<br />

chroma<strong>to</strong>graphy (9:1 <strong>to</strong> 4:1 EtOAc:petrol) <strong>to</strong> give amide 204 as colourless needles and<br />

hydroxyamide 205 as a colourless oil (see text).<br />

204 R f : 0.22 (4:1, petrol:EtOAc); Mpt: 155-156 ºC (CH 2 Cl 2 ); MS m/z (CI+) 308<br />

(100%, MH + ), 309 (19%, (M+1)H + ), 216 (15%, [M-Bn] + ); HRMS: found 308.2018,<br />

MH requires 308.2009; IR ν max (film)/cm⎯¹ 2929 (C-H), 1639 (C=O), 1534 (N-H); ¹H-<br />

NMR (CDCl 3 , 500 MHz) δ 7.33-7.29 (m, 2H, Ph), 7.27-7.19 (m, 6H, Ph), 7.07-7.05<br />

(m, 2H, Ph), 5.69 (d, 1H, J 7.5, NH), 5.29 (q, 1H, J 7.5, CHPh), 3.13 (dd, 1H, J 14.0,<br />

7.5, CH 2 Ph), 3.08 (dd, 1H, J 14.0, 7.5, CH 2 Ph), 2.02 (tt, 1H, J 11.5, 3.0, CH), 1.81-<br />

1.69 (m, 4H), 1.67-1.57 (m, 1H), 1.41-1.27 (m, 2H), 1.28-1.12 (m, 3H); ¹³C-NMR<br />

(CDCl 3 , 125 MHz) δ 175.2 (C=N), 141.7 (ipso-Ph), 137.3 (ipso-Ph), 129.3, 128.5 (Ph),<br />

128.3 (para-Ph), 127.3 (para-Ph), 127.3, 126.5 (Ph), 53.8 (CHPh), 45.5 (CH 2 Ph), 42.6<br />

(CH), 29.6, 29.5, 25.7, 25.6 (CH 2 ).<br />

205 R f : 0.17 (2:1, petrol:EtOAc); MS m/z (CI) 324 (100%, MH + ), 325 (22%,<br />

(M+1)H + ), 217 (74%, [M-PhCH 2 OH] + ); HRMS: found 324.1963, MH requires<br />

236


Experimental for chapter 3.2<br />

324.1958; IR ν max (film)/cm⎯¹ 3315 (br, O-H), 2931 (C-H), 1641 (C=O), 1534 (N-H);<br />

¹H-NMR (CDCl 3 , 500 MHz) δ 7.25-7.23 (m, 10H, Ph), 6.32 (d, 1H, J 7.5, NH), 5.23<br />

(dd, 1H, J 8.0, 4.5, CHNPh), 4.30 (d, 1H, J 4.5, CHOPh), 2.09 (tt, 1H, J 11.5, 3.0,<br />

CH), 1.81-1.71 (m, 4H), 1.67-1.61 (m, 1H), 1.36-1.15 (m, 5H); ¹³C-NMR (CDCl 3 , 125<br />

MHz) δ 176.4 (C=N), 140.7 (ipso-Ph), 139.6 (ipso-Ph), 128.7, 128.2 (Ph), 127.7 (para-<br />

Ph), 127.7 (para-Ph), 126.8, 126 (Ph), 77.2 (CHOPh), 59 (CHNPh), 45.4 (CH), 29.6,<br />

29.4, 25.6, 25.6 (CH 2 ).<br />

Synthesis of (3S*,4S*)-N-((S*)-1,2-diphenylethyl)-3-isopropyl-4-methylcyclohexanone-4-carboxamide<br />

(206)<br />

Ph<br />

O<br />

N<br />

Ph<br />

H 2 Pd/C 20 bar<br />

Ph<br />

Ph<br />

H<br />

N<br />

O<br />

O<br />

O<br />

A solution of oxazoline 201 (90 mg, 0.24 mmol) in methanol (6 cm 3 ) was passed<br />

thorough the H-cube (1 cm 3 /min, 20 bar, Pd/C) and the eluent collected for 30 min.<br />

<strong>The</strong> solvent was removed by rotary evaporation <strong>to</strong> give amide 206 (93 mg, 96%) as a<br />

colourless oil.<br />

R f : 0.10 (4:1, petrol:EtOAc); MS m/z (CI+) 378 (100%, MH + ), 379 (24%, (M+1)H + );<br />

HRMS: found 378.2425, MH requires 378.2428; IR ν max (film)/cm⎯¹ 2932 (m, C-H),<br />

1714 (ke<strong>to</strong>ne), 1639 (amide), 1531 (m, N-H), 1453 (m); ¹H-NMR (CDCl 3 , 500 MHz)<br />

δ 7.37-7.18 (m, 8H, Ph), 7.11-7.16 (m, 2H, Ph), 5.93 (br d, 1H, J 8.0, NH), 5.39-5.29<br />

(m, 1H, CHNPh), 3.23 (dd, 1H, J 14.0, 6.0, CH 2 Ph), 3.02 (dd, 1H, J 14.0, 9.0, CH 2 Ph),<br />

2.96-2.85 (m, 1H), 2.93 (dd, 1H, J 14.5, 12.0), 2.74 (ddd, 1H, J 15.5, 11.5, 6.5), 2.17-<br />

2.11 (m, 2H), 1.82-1.75 (m, 2H, CHMe 2 , CH), 1.59-1.53 (m, 2H), 1.20 (s, 3H, J 6.5,<br />

Me), 0.81 (d, 3H, J 6.5, i-Pr), 0.52 (d, 3H, i-Pr); ¹³C-NMR (CDCl 3 , 75.5 MHz) δ<br />

213.4, 174.5, 141.5, 137.3, 129.2, 128.6, 128.4, 127.5, 126.7, 126.5, 53.7, 51.8, 43.2,<br />

42.7, 38.3, 38.1, 37.0, 27.7, 24.5, 23.7, 17.2.<br />

237


Experimental for chapter 3.2<br />

Synthesis of (1R*,2R*)-2-(cyclohexylmethylamino)-1,2-diphenylethanol (210)<br />

Ph<br />

O<br />

N<br />

Ph<br />

DIBALH (3 eq)<br />

0 °C<br />

H<br />

N<br />

Ph<br />

OH<br />

Ph<br />

O<br />

H<br />

N<br />

Ph<br />

OH<br />

Ph<br />

210 205<br />

A solution of DIBAlH (0.24 cm 3 , 1M in PhMe, 3 eq) was added drop wise <strong>to</strong> a stirred<br />

solution of oxazoline 101m (22 mg, 0.07 mmol) in <strong>to</strong>luene (1 cm 3 ) under a nitrogen<br />

atmosphere, maintained at 0 °C for 4 hr before warming <strong>to</strong> rt and stirred for 16 hr.<br />

Ammonium chloride (sat. aq. 2 cm 3 ) was added and stirred for 2 hr before being<br />

partitioned between water (2 cm 3 ) and CH 2 Cl 2 (10 cm 3 ) and the aqueous layer was<br />

extracted with CH 2 Cl 2 (3 x 10 cm 3 ) and the combined organic layers dried with sodium<br />

sulfate and reduced under vacuum. Flash chroma<strong>to</strong>graphy (9:1 petrol:EtOAc) yielded<br />

amine 210 (17 mg, 80%) as a colourless oil and hydroxyamide 205 (2 mg, 10%).<br />

210 R f : 0.26 (4:1, petrol:EtOAc+Et 3 N); MS m/z (CI+) 310 (100%, MH + ), 311 (19%,<br />

(M+1)H + ), 202 (68%, [M-PhCH 2 OH] + ); HRMS: found 310.2176, MH requires<br />

310.2165; IR ν max (film)/cm⎯¹ 3400 (br, N-H, O-H), 2922 (C-H), 1451 (m, C-H); ¹H-<br />

NMR (CDCl 3 , 500 MHz) δ 7.24-7.16 (m, 6H, Ph), 7.09-7.07 (m, 2H, Ph), 7.02-6.98<br />

(m, 2H, Ph), 4.55 (d, 1H, J 9.0 CHOPh), 3.53 (d, 1H, J 9.0 CHNPh), 2.77 (br s, 2H,<br />

OH, NH), 2.38 (dd, 1H, J 11.5, 6.5, H5), 2.27 (dd, 1H, J 11.5, 6.5 H5’), 1.79-1.62 (m,<br />

5H), 1.46-1.38 (m, 1H), 1.26-1.10 (m, 3H), 0.95-0.82 (m, 2H); ¹³C-NMR (CDCl 3 , 125<br />

MHz) δ 141.2 (ipso-Ph), 140.0 (ipso-Ph), 128.2, 127.8, 127.6, 127.3, 126.8 (Ph), 77.6<br />

(CHOPh), 70.8 (CHNPh), 54.2 (CH 2 N), 38.2 (CH), 31.4, 31.2, 26.6, 26.0, 26.0 (CH 2 ).<br />

205: see page 236<br />

238


Experimental for chapter 3.2<br />

Synthesis of (1R*,2R*)-2-amino-1,2-diphenylethyl cyclohexanecarboxylate<br />

hydrochloride (211.HCl)<br />

Ph Ph<br />

NH 3 Cl<br />

O N HCl (aq), THF, Δ<br />

O O<br />

Ph<br />

Ph<br />

Oxazoline 101m (44 mg, 0.14 mmol) was dissolved in a THF/HCl (aq) mixture (1 cm 3 ,<br />

3:1 HCl (6M):THF) and gently heated such that a white precipitate slowly forms.<br />

Once precipitate has s<strong>to</strong>pped forming (c. 2 min) the solution was triturated with THF<br />

(2 cm 3 ) and filtered, the residue was transferred <strong>to</strong> another flask (CH 2 Cl 2 ) and the<br />

filtrate concentrated under vacuum and triturated with diethyl ether and again filtered.<br />

<strong>The</strong> residues were combined (CH 2 Cl 2 ) dried over sodium sulfate and concentrated <strong>to</strong><br />

give ester 211.HCl (47 mg, 91%) as colourless needles.<br />

R f : 0.12 (2:1, petrol:EtOAc); Mpt: 134 ºC (CH 2 Cl 2 ); MS m/z (CI+) 324 (52%, [M-<br />

Cl] + ), 306 (100%, [M-NH 3 Cl] + ), 307 (20%, [(M+1)-NH 3 Cl] + ); HRMS: found<br />

324.1964, M-Cl requires 324.1958; IR ν max (film)/cm⎯¹ 2925 (N-H), 2853 (N-H), 2365<br />

(w), 1731 (C=O), 1162 (m), 1027 (w, C-N); ¹H-NMR (CD 3 OD, 500 MHz) δ 7.36-7.32<br />

(m, 3H, Ph), 7.28-7.22 (m, 5H, Ph), 7.19-7.14 (m, 2H, Ph), 5.98 (d, 1H, J 7.0,<br />

CHOPh), 4.76 (d, 1H, J 7.0, CHNPh), 2.58-2.51 (m, 1H, CH), 1.96-1.87 (m, 2H),<br />

1.79-1.62 (m, 3H), 1.50-1.41 (m, 1H), 1.39-1.18 (m, 4H); ¹³C-NMR (CD 3 OD, 75.5<br />

MHz) δ 175.8 (C=O), 137.1 (ipso-Ph), 134.5 (ipso-Ph), 130.6 (para-Ph), 130.1 (Ph),<br />

129.9 (para-Ph), 129.5, 129.1, 128.4 (Ph), 77.9 (CHOPh), 60.1 (CHNPh), 43.9 (CH),<br />

30.2, 29.5, 26.7, 26.5, 26.1 (CH 2 ).<br />

239


Experimental for chapter 3.2<br />

Synthesis of 1,2-diphenylethanamine (212)<br />

NH 3 Cl<br />

O<br />

O<br />

Ph<br />

Ph<br />

H 2 , Pd/C<br />

H 2 N<br />

Ph<br />

Ph<br />

A stirred solution of ester 211.HCl (20 mg) and palladium on carbon (5%, 2 mg) in<br />

ethanol (2 cm 3 ), was backfilled with hydrogen and maintained under a positive<br />

pressure until complete by TLC (1.5 hr). <strong>The</strong> pressure was released, catalyst filtered<br />

under nitrogen, the solvent was removed by rotary evaporation and the resulting<br />

residue partitioned between water (2 cm 3 ) and CH 2 Cl 2 (6 cm 3 ). <strong>The</strong> aqueous phase<br />

was washed with further CH 2 Cl 2 (2 x 5 cm 3 ) and the combined organic phases dried<br />

over sodium sulphate and concentrated <strong>to</strong> give amine 212 (11 mg, 100%) as a white<br />

powder.<br />

Analytical data consistent with literature. 18<br />

Synthesis of (1S*,4R*,5R*,6S*)-(1R,2R)-2-amino-1,2-diphenylethyl 4,5-dihydroxy-<br />

6-isopropyl-1-methylcyclohex-2-enecarboxylate.hydrochloride (214)<br />

Ph Ph<br />

NH 3 Cl<br />

O N<br />

Ph O O<br />

HCl (aq), THF<br />

Ph<br />

Δ<br />

OH<br />

OH<br />

OH<br />

OH<br />

A solution of oxazoline 213 (11 mg) in THF (0.4 cm 3 ) and HCl (3M, 0.2 cm 3 ) was<br />

heated at 90 °C for 13 hr, and partitioned between CH 2 Cl 2 (5 cm 3 ) and water (2 cm 3 ).<br />

<strong>The</strong> aqueous layer was washed with CH 2 Cl 2 (2 x 5 cm 3 ), the combined organic extracts<br />

dried over anhydrous sodium sulfate and solvent removed <strong>to</strong> yield ester 214 (10 mg,<br />

70%) as a colourless oil.<br />

R f : 0.25 (EtOAc); MS m/z (ES+) 410 (100%, [M-Cl] + ), 411 (27%, [(M+1)-Cl] + ), 432<br />

(34%, [M-HCl]Na + ); HRMS: found 426.2275, MH requires 426.2275; IR ν max<br />

(film)/cm⎯¹ 3340 (br, O-H), 2942 (m), 1733 (C=O), 1452 (m); ¹H-NMR (CDCl 3 , 500<br />

MHz) δ 7.22-7.15 (m, 7H, Ph), 7.12-7.10 (m, 3H, Ph), 5.81 (d, 1H, J 8.5, CHOPh),<br />

240


Experimental for chapter 3.2<br />

5.56 (d, 1H, J 10.0, H6), 5.41 (d, 1H, J 10.0, H5), 4.31 (d, 1H, J 8.5, CHNPh), 3.93-<br />

3.87 (m, 2H, H4, H3), 3.32 (br s, 1H, OH), 2.44 (br s, 1H, OH), 2.23 (pd, 1H, J 7.0,<br />

1.0, CHMe 2 ), 1.40 (d, 1H, J 10.5, 1.0, H2), 1.36 (s, 3H, Me), 1.11 (d, 3H, J 7.0, i-Pr),<br />

1.02 (d, 3H, J 7.0, i-Pr); ¹³C-NMR (CDCl 3 , 125 MHz) δ 194.9 (C=O), 138.3 (ipso-Ph),<br />

137.9 (ipso-Ph), 127.0, 126.2 (Ph), 132.5 (C5), 129.2 (C6), 128.7, 127.9, 126.3, 80.6<br />

(CHOPh), 74.7 (CHOH), 72.7 (CHOH), 63.1 (CHNPh), 53.9 (C2), 33.6 (C1), 26.9<br />

(CHMe 2 ), 22.7 (i-Pr), 20.5 (Me) , 18.2 (i-Pr).<br />

Synthesis of (1S*,6S*)-(1R*,2R*)-2-amino-1,2-diphenylethyl 6-isopropyl-1-<br />

methyl-4-oxocyclohex-2-enecarboxylate. hydrochlorate (215)<br />

Ph Ph<br />

O N<br />

Ph<br />

HCl (aq), THF, Δ<br />

O<br />

NH 2<br />

O O<br />

Ph<br />

6<br />

5<br />

1<br />

2<br />

3<br />

4<br />

A solution of oxazoline 201 (30 mg, 0.08 mmol) in THF (1.5 cm 3 ) and HCl (3 cm 3 ,<br />

6M) was heated at reflux for 12 hr, cooled, and the solvent removed under vacuum <strong>to</strong><br />

give a white solid. <strong>The</strong> white solid was triturated with Et 2 O (5 cm 3 ) and filtered,<br />

giving ester 215 (15 mg, 45%) as a white amorphous solid.<br />

O<br />

Mpt: 156 ºC (Et 2 O); MS m/z (ES+) 414 (100%, [M-HCl]Na + ), 415 (26%, [(M+1)-<br />

HCl]Na + ); HRMS: found 392.2218, [M-Cl] + requires 392.2220; IR ν max (film)/cm⎯¹<br />

3325 (br, NH), 2873 (m, C-H), 1737 (COOR), 1674 (C=C=O), 1458 (s), 1103 (m); ¹H-<br />

NMR (CD 3 OD, 300 MHz) δ 7.36-7.23 (m, 10H, Ph), 7.12 (d, 1H, J 10.0, H6), 6.18 (d,<br />

1H, J 9.0, CHOPh), 5.97 (d, 1H, J 10.0, H5), 4.99-4.95 (m, 1H, CHNPh), 2.56-2.48<br />

(m, 2H, H3), 2.27-2.19 (m, 1H, H2), 1.67 (s, 3H, Me), 1.47 (m, 1H, CHMe 2 ), 0.75 (d,<br />

3H, J 7.0, i-Pr), 0.28 (d, 3H, J 7.0, i-Pr); ¹³C-NMR (CDCl 3 , 125 MHz) δ 199.9<br />

(ke<strong>to</strong>ne), 172.0 (ester C=O), 152.1 (C6), 138.2 (ipso-Ph), 137.1 (ipso-Ph), 128.8,<br />

128.3, 128.5, 128.0, 127.9, 127.6, 127.1 (Ph, C5), 80.7 (CHOPh), 69.1 (CHNPh), 48.7<br />

(C2), 47.8 (C1), 34.6 (C3), 27.8 (CHMe 2 ), 25.2, 23.1, 18.5 (Me).<br />

241


Experimental for chapter 3.2<br />

Synthesis of (1R,2R,3S,4S,5R,6S)-(1R,2R)-2-amino-1,2-diphenylethyl 4,5-<br />

dihydroxy-2,3-epoxy-6-isopropyl-1-methylcyclohexanecarboxylate (217)<br />

Ph Ph<br />

O N<br />

HClO 4 (aq), dioxane<br />

O<br />

rt<br />

OH<br />

OH<br />

O<br />

Ph<br />

Ph<br />

NH 2<br />

O O<br />

6<br />

5<br />

1<br />

2<br />

3<br />

4 OH<br />

OH<br />

A solution of oxazoline 216 (9 mg) in dioxane (1.0 cm 3 ) and perchloric acid (1M, 0.1<br />

cm 3 ) was stirred at rt for 28 hr, and partitioned between CH 2 Cl 2 (5 cm 3 ) and sodium<br />

bicarbonate (sat. 2 cm 3 ). <strong>The</strong> aqueous layer was washed with CH 2 Cl 2 (2 x 5 cm 3 ), the<br />

combined organic extracts dried over anhydrous sodium sulfate and purified by flash<br />

column chroma<strong>to</strong>graphy <strong>to</strong> give ester 217 (4 mg, 40%) as a colourless oil and starting<br />

material (4 mg, 45%).<br />

Rf: 0.25 (10%, MeOH in EtOAc); [α] 22 D : –2.4 (c = 0.5, CHCl 3 ); MS m/z (ES+) 426<br />

(100%, MH + ), 427 (32%, (M+1)H + ), 448 (29%, MNa + ); HRMS: found 426.2275, MH<br />

requires 426.2275; IR ν max (film)/cm⎯¹ 3360 (br, O-H), 2963 (m), 1720, 1453 (m),<br />

1259 (m); ¹H-NMR (CD 3 OD, 500 MHz) δ 7.22-7.18 (m, 7H, Ph), 7.17-7.14 (m, 3H,<br />

Ph), 5.83 (d, 1H, J 8.5, CHOPh), 4.36 (d, 1H, J 8.5, CHNPh), 3.85 (dd, 1H, J 11.0, 8.0,<br />

H3), 3.69 (dd, 1H, J 8.0, 1.5, H4), 3.39 (dd, 1H, J 4.0, 1.5, H5), 3.29 (d, 1H, J 4.0,<br />

H6), 1.54 (p, 1H, J 7.0, CHMe 2 ), 1.47 (s, 3H, Me), 1.23 (d, 1H, J 11.0, H2), 0.92 (d,<br />

3H, J 7.0, CHMe A Me b ), 0.72 (d, 3H, J 7.0, CHMe a Me B ); ¹³C-NMR (CD 3 OD, 75.5<br />

MHz) δ 194.9 (C=O), 137.9 (ipso-Ph), 138.3 (ipso-Ph), 128.7, 128.2, 127.9, 127.8,<br />

127.3 (Ph), 80.6 (CHOPh), 75.2, 70.9 (C3, C4), 63.1 (CHNPh), 62.1, 57.2 (C5, C6),<br />

54.5 (C2), 32.4 (C1), 28.1 (CHMe 2 ), 26.2 (CHMe A Me b ), 23.4 (Me), 17.1 (CHMe a Me B ).<br />

242


Experimental for chapter 3.2<br />

Synthesis of (1S,6S)-(1R,2R)-2-(methylamino)-1,2-diphenylethyl 6-isopropyl-1-<br />

methyl-4-oxocyclohex-2-enecarboxylate (218)<br />

Ph<br />

O<br />

N<br />

Ph<br />

MeOTf, then NH 4 Cl<br />

Ph<br />

O<br />

1<br />

6<br />

O<br />

2<br />

HN<br />

Ph<br />

O<br />

General procedure 6 was used employing oxazoline 201 (55 mg, 0.15 mmol) and<br />

methyl triflate (34 µl, 0.29 mmol) for 16 hr and an ammonium chloride (sat. aq., 0.5<br />

cm 3 ) quench. <strong>The</strong> layers were partitioned, the aqueous layer washed with CH 2 Cl 2 (2 x<br />

5 cm 3 ) and the combined organic phases dried over anhydrous sodium sulfate. Flash<br />

chroma<strong>to</strong>graphy (9:1 <strong>to</strong> 2:1 petrol:EtOAc) gave ester 218 (35 mg, 60%) and starting<br />

material (3 mg, 5%).<br />

5<br />

4<br />

O<br />

3<br />

R f : 0.20 (4:1, petrol:EtOAc); [α] 25 D : +77 (c = 1.4, CHCl 3 ); MS m/z (CI) 406 (100%,<br />

MH + ), 407%, (M+1)H + , 428 (5%, MNa + ); HRMS: found 406.2375, MH requires<br />

406.2377; IR ν max (film)/cm⎯¹ 2959 (m), 1730 (C=O), 1683 (C=C–C=O), 1453 (m),<br />

1225 (m), 1107 (m); ¹H-NMR (CDCl 3 , 500 MHz) δ 7.21-7.16 (m, 6H, Ph), 7.05-7.01<br />

(m, 4H, Ph), 6.83 (d, 1H, J 10.0, H6), 6.05 (d, 1H, J 10.0, H5), 5.86 (d, 1H, J 8.0,<br />

CHOPh), 3.91 (d, 1H, J 8.0, CHNPh), 2.70 (dd, 1H, J 17.5, 9.0, H3 ax ), 2.48 (dd, 1H, J<br />

17.5, 5.0, H3 eq ), 2.26 (s, 3H, NMe), 2.12 (ddd, 1H, J 9.0, 5.0, 2.0, H2), 1.82 (pd, 1H, J<br />

7.0, 2.0, CHMe 2 ), 1.48 (s, 3H, Me), 0.85 (d, 3H, J 7.0, CHMe A Me b ), 0.57 (d, 3H, J 7.0,<br />

CHMe a Me B ); ¹³C-NMR (CDCl 3 , 125 MHz) δ 199.7 (C=C=O), 172.1 (CO2), 152.0<br />

(C6), 138.2 (ipso-Ph), 137.1 (ipso-Ph), 128.6, 128.3, 128.1, 128.0, 127.9, 127.6, 127.2<br />

(Ph, C5), 80.7 (CHOPh), 69.1 (CHNPh), 49.1 (C2), 47.8 (C1), 34.6 (C3), 34.3 (NMe),<br />

27.8 (CHMe 2 ), 25.0 (Me), 23.1 (CHMe A Me b ), 17.7 (CHMe a Me B ).<br />

243


Experimental for chapter 3.2<br />

Synthesis of (1S*,4S*,5S*)-5-isopropyl-4-methyl-4-(N-methyl- (4R*,5R*)-4,5-<br />

diphenyloxazolidin-2-yl)cyclohex-2-enol (222) & (1S*,4S*,6S*)-4-hydroxy-6-<br />

isopropyl-1-methylcyclohex-2-enecarbaldehyde (223)<br />

Ph Ph<br />

Ph Ph<br />

O<br />

N<br />

O N<br />

i) MeOTf, then NaBH 4<br />

6<br />

1<br />

2<br />

O<br />

H<br />

ii) H 3 O + 223<br />

O<br />

5<br />

4<br />

OH<br />

222<br />

3<br />

(±)<br />

OH<br />

(±)<br />

General procedure 6 was used employing oxazoline 201 (72 mg, 0.19 mmol) and<br />

methyl triflate (50 µl, 0.40 mmol) for 19 hr. <strong>The</strong> crude oxazolidine was dissolved in<br />

4:1 THF:water (2 cm 3 ) and oxalic acid (125 mg) was added and stirred at rt for 40 hr,<br />

the solvent was removed, the aqueous layer washed with EtOAc and the combined<br />

organic phases dried over anhydrous MgSO 4 . Flash chroma<strong>to</strong>graphy (5% <strong>to</strong> 10%<br />

EtOAc in petrol) gave aldehyde 223 (16 mg, 45%) and oxazolidine 222 (8 mg, 11%) as<br />

colourless oils.<br />

222 R f : 0.29 (4:1, petrol:EtOAc); MS m/z (CI+) 392 (100%, MH + ), 238 (38%);<br />

HRMS: found 392.2594, MH requires 392.2584; IR ν max (film)/cm⎯¹ 3583 (O-H),<br />

2955 (C-H), 1453 (C-Me); ¹H-NMR (CDCl 3 , 500 MHz) δ 7.32-7.28 (m, 3H, Ph), 7.26-<br />

7.21 (m, 5H, Ph), 7.09-7.02 (m, 2H, Ph), 6.13 (dd, 1H, J 10.0, 2.0, H5), 5.83 (dm, 1H,<br />

J 10.0, H6), 4.82 (d, 1H, J 9.5, CHOPh), 4.58 (s, 1H, CHON), 4.21-4.15 (m, 1H, H4),<br />

3.31 (d, 1H, J 9.5, CHNPh), 2.40 (s, 3H, NMe), 2.19 (p, 1H, CHMe 2 ), 1.95-1.86 (m,<br />

1H, H3), 1.84-1.76 (m, 1H, H3’), 1.61 (br s, 1H, OH), 1.39-1.34 (m, 1H, H2), 1.16 (s,<br />

3H, Me), 1.08 (d, 3H, J 7.0, i-Pr), 1.02 (d, 3H, J 7.0, i-Pr); ¹³C-NMR (CDCl 3 , 125<br />

MHz) δ 138.7 (ipso-Ph), 137.9 (ipso-Ph), 135.2 (C5), 132.4 (C6), 128.3, 128.2, 128.0<br />

(Ph), 127.7 (para-Ph), 127.6 (para-Ph), 126.3 (Ph), 100.6 (CHON), 85.4 (CHOPh),<br />

79.5 (CHNPh), 69.5 (C4), 49.6 (C2), 45.2 (NMe), 42.0 (C1), 34.3 (C3), 25.2 (i-Pr),<br />

25.0 (CHMe 2, i-Pr), 18.3 (Me).<br />

223 R f : 0.23 (2:1, petrol:EtOAc); MS m/z (CI+) 200 (100%, MNH + 4 ); HRMS: found<br />

200.1641, MNH 4 requires 200.1645; IR ν max (film)/cm⎯¹ 3405 (br, O-H), 2960 (m, C-<br />

H), 1716 (C=O); ¹H-NMR (CDCl 3 , 500 MHz) δ 9.80 (s, 1H, CHO), 5.99 (dm, 1H, J<br />

244


Experimental for chapter 3.2<br />

10.0, H5), 5.17 (dd, 1H, J 10.0, 2.0, H6), 4.39-4.33 (m, 1H, H4), 2.10-1.99 (m, 2H,<br />

H3), 1.63-1.58 (m, 2H, H2,CHMe 2 ), 1.20 (s, 3H, Me), 0.96 (d, 3H, J 7.0, CHMe A Me b ),<br />

0.78 (d, 3H, J 7.0, CHMe a Me B ); ¹³C-NMR (CDCl 3 , 125 MHz) δ 202.7 (CHO), 135.5<br />

(C5), 130.7 (C6), 68.5 (C4), 52.3 (C1), 49.2 (C2), 29.5 (C3), 25.8 (CHMe 2 ), 23.5<br />

(CHMe A Me b ), 20.5 (Me), 18.3 (CHMe a Me B ).<br />

Synthesis of (1S,4S,5S)-4-(hydroxymethyl)-5-isopropyl-4-methylcyclohex-2-enol<br />

(225)<br />

Ph<br />

O<br />

N<br />

Ph<br />

i) MeOTf, then NaBH 4<br />

ii) H 3 O +<br />

iii) NaBH 4 , MeOH<br />

HO<br />

OH<br />

O<br />

General procedure 6 was used employing oxazoline 201 (66 mg, 0.18 mmol) and<br />

methyl triflate (40 µl, 0.35 mmol) for 18 hr. <strong>The</strong> crude oxazolidine was subjected <strong>to</strong><br />

general procedure 7, the room temperature hydrolysis taking 3 days. <strong>The</strong> resulting<br />

crude alcohol was purified by flash column chroma<strong>to</strong>graphy (2:1 <strong>to</strong> 1:1 petrol:EtOAc)<br />

<strong>to</strong> give diol 225 (31 mg, 94%) as a colourless oil.<br />

R f : 0.12 (1:1, petrol:EtOAc); [α] 22 D : +49.5 (c = 1.1, CHCl 3 ); MS m/z (CI+) 185<br />

(100%, MH + ), 202 (44%, MNH + 4 ), 137 (62%); HRMS: found 202.1808, MNH 4<br />

requires 202.1802; IR ν max (film)/cm⎯¹ 3330 (br, O-H), 2955 (C-H), 2869 (m, C-H),<br />

1462, 1042 (m); ¹H-NMR (CDCl 3 , 500 MHz) δ 5.84-5.81 (m, 1H, H5), 5.41 (dd, 1H, J<br />

10.0, 2.0, H6), 4.26-4.21 (m, 1H, H4), 3.65 (d, 1H, J 11.0, H7 a ), 3.36 (d, 1H, J 11.0,<br />

H7 b ), 2.12 (br s, 1H, OH), 1.99 (p, 1H, J 7.0, CHMe 2 ), 1.89-1.83 (m, 1H, H3 a ), 1.77<br />

(br s, 1H, OH), 1.61-1.52 (m, 1H, H3 b ), 1.33 (d, 1H, J 12.5, H2), 0.96 (d, 3H, J 7.0, i-<br />

Pr), 0.94 (s, 3H, Me), 0.90 (d, 3H, J 7.0, i-Pr); ¹³C-NMR (CDCl 3 , 125 MHz) δ 136.0<br />

(C5), 133.2 (C6), 69.0 (C4), 67.4 (C7), 47.0, 40.9 (C2, C1), 29.9, 25.3 (C3, CHMe 2 ),<br />

24.5, 24.3, 18.0 (Me).<br />

245


Experimental for chapter 3.2<br />

Synthesis of ((1S,4S,5S)-4-(hydroxymethyl)-5-isopropyl-4-methylcyclohex-2-enol)<br />

bis para-bromobenzoate (115)<br />

O<br />

HO<br />

Cl<br />

Br Br<br />

DMAP<br />

Et<br />

OH<br />

3 N, CH 2 Cl 2<br />

8<br />

9<br />

O<br />

O<br />

7<br />

1 2<br />

3<br />

6<br />

4<br />

5<br />

O<br />

O<br />

Br<br />

4-bromobenzoyl chloride (120 mg, 0.55 mmol) was added <strong>to</strong> a solution of diol 225 (20<br />

mg, 0.1 mmol), DMAP (2 mg, 0.02 mmol), triethylamine (1 cm 3 ) in CH 2 Cl 2 (5 cm 3 )<br />

under a nitrogen atmosphere. After 12 hr sodium hydroxide (2.5 cm 3 , 3M aq.) was<br />

added <strong>to</strong> the reaction and stirred for 1 hr before being partitioned in EtOAc (1 cm 3 ) and<br />

the organic layer washed sequentially with HCl (3M aq.), sodium bicarbonate, and<br />

brine. <strong>The</strong> organic layer was dried over anhydrous sodium sulphate and solvent<br />

evaporated <strong>to</strong> give a clear yellow oil, which was purified by flash column<br />

chroma<strong>to</strong>graphy (99:1 petrol:EtOAc) <strong>to</strong> give benzoyl ester 115 (34 mg, 62%) as a<br />

white oil.<br />

R f : 0.46 (9:1, petrol:EtOAc); [α] 21 D : –15 (c = 1.0, CHCl 3 ); IR ν max (film)/cm⎯¹ 2960<br />

(m), 1717 (C=O), 1590 (m), 1266, 1101 (m); ¹H-NMR (CDCl 3 , 500 MHz) δ 7.92 (d,<br />

2H, J 8.5, H8 or H8'), 7.82 (d, 2H, J 8.5, H8 or H8'), 7.61-7.55 (m, 4H, H9, H9'), 5.78-<br />

5.72 (m, 1H, H5), 5.66 (dd, 1H, J 10.0, 2.0, H6), 5.64-5.59 (m, 1H, H4), 4.34 (d, 1H, J<br />

11.0, H7 a ), 4.26 (d, 1H, J 11.0, H7 b ), 2.19-2.07 (m, 2H, H3, CHMe2), 1.85-1.76 (m,<br />

1H, H3), 1.58 (d, 1H, J 14.0, H2), 1.16 (s, 3H, Me), 1.04 (d, 3H, J 7.0, i-Pr), 0.90 (d,<br />

3H, J 7.0, i-Pr); ¹³C-NMR (CDCl 3 , 75.5 MHz) δ 165.6 (C=O), 165.5 (C=O), 137.7 (C6<br />

or C5), 131.8, 131.7, 131.1, 129.3, 129.1, 128.1, 128.1 (Ar), 127.4 (C6 or C5), 72.2<br />

(C4), 68.6 (C7), 46.9, 39.5 (C2, C1), 25.7, 25.5 (C3, CHMe 2 ), 24.5 (CHMe a Me b ), 24.4<br />

(Me), 18.0 (CHMe a Me b ); Chiral HPLC: DAICEL Chiralcel OD-H, 2.5% IPA in<br />

hexane, 0.5 ml/min, 11.3 min (0.2%), 12.7 min (99.8%); racemic sample: 11.3 min<br />

(49.6%), 12.9 min (50.4%).<br />

246


Experimental for chapter 4.1<br />

5.5 Experimental Procedures for Chapter 4.1<br />

Synthesis of (2S,3S,4R,5S)-4-((4R,5R)-4,5-diphenyloxazolin-2-yl)-2,3-dihydroxy-5-<br />

isopropyl-4-methylcyclohexanone (280)<br />

Ph Ph<br />

Ph Ph<br />

Ph Ph<br />

O<br />

N<br />

O<br />

N<br />

O<br />

N<br />

OsO 4 , NMO, CH 2 Cl 2<br />

280 281<br />

HO<br />

6<br />

1<br />

2<br />

HO<br />

6<br />

1<br />

2<br />

O<br />

HO<br />

5<br />

O<br />

4<br />

3<br />

HO<br />

5<br />

O<br />

4<br />

3<br />

General procedure 5 was employed using enone (100 mg, 0.27 mmol), OsO 4 (0.6 mg,<br />

0.003 mmol), NMO monohydrate (73 mg, 0.54 mmol), in CH 2 Cl 2 (5 cm 3 ). Upon<br />

completion, sodium sulfite (0.5 cm 3 , sat. aq.) was added. Purification by flash<br />

chroma<strong>to</strong>graphy (9:1 <strong>to</strong> 2:1 petrol:EtOAc) yielded diol 280 (57 mg, 55%) as a<br />

colourless foam, and diol 281 (3 mg, 2%) and starting material (11 mg, 11%) as a<br />

colourless oil.<br />

280 R f : 0.39 (1:1 petrol:EtOAc); [α] 25 D : +36 (c = 1.0, CH 2 Cl 2 ); MS m/z (CI+): 408<br />

(100%, MH + ), 409 (24%, (M+1)H + ); HRMS (ESI+) m/z found 408.2170 (MH calcd.<br />

408.2169); IR ν max (film)/cm -1 : 3470 (br, O-H), 2952 (m, C-H), 1719 (C=O), 1453 (m);<br />

1 H-NMR (DMSO, 500 MHz) δ 7.36 (m, 2H, ortho-Ph), 7.45 (t, 2H, J 7.5, meta-Ph),<br />

7.40-7.38 (m, 3H, Ph), 7.32 (tt, 1H, J 7.5, 2.0, para-Ph), 7.32 (d, 2H, J 7.5, ortho-Ph),<br />

5.49 (d, 1H, J 4.5, C6OH), 5.25 (d, 1H, J 9.0, CHO), 5.14 (d, 1H, J 9.0, CHN), 5.00<br />

(dd, 1H, J 7.0, 3.5, H5), 4.72 (d, 1H, J 7.0, C5OH), 4.04 (t. 1H, J 4.0, H6), 2.76 (t, 1H,<br />

J 13.5, H3 axial ), 2.18 (dd, 1H, J 13.5, 4.0, H3 eq ), 2.12 (pd, 1H, J 7.0, 2.5, CHMe 2 ), 2.01<br />

(ddd, 1H, J 14.0, 4.0, 2.5, H2), 1.42 (s, 3H, Me), 0.94 (d, 3H, J 7.0, CHMe a Me b ), 0.83<br />

(d, 3H, J 7.0, CHMe a Me b ); 13 C-NMR (DMSO, 125 MHz) δ 209.9 (C=O), 168.6<br />

(C=N), 141.5 (ipso-Ph), 139.7 (ipso-Ph), 129.1 (meta-Ph), 128.8 (meta-Ph), 128.7<br />

(para-Ph), 127.3 (para-Ph), 126.6 (ortho-Ph), 126.4 (ortho-Ph), 126.3 (ortho-Ph), 87.3<br />

(CHO), 79.3 (C6), 77.4 (CHN), 75.5 (C5), 46.2 (C1), 45.4 (C2), 37.8 (C3), 26.6<br />

(CHMe 2 ), 24.6 (CHMe a Me b ), 21.6 (Me), 18.5 (CHMe a Me b ).<br />

247


Experimental for chapter 4.1<br />

281 R f : 0.30 (1:1 petrol:EtOAc); [α] 25 D : +58 (c = 0.8, DMSO); MS m/z (CI+): 408<br />

(100%, MH + ), 409 (28%, (M+1)H + ), 390 (20%, [M–H 2 O]H + ); HRMS (ESI+) m/z<br />

found 408.2168 (MH calcd. 408.2169); IR ν max (film)/cm -1 : 3468 (br, O-H), 2944 (m,<br />

C-H), 1712 (C=O), 1452 (m, C-Me); 1 H-NMR (DMSO, 500 MHz) δ 7.47-7.3 (m, 7H,<br />

Ph), 7.24-7.20 (m, 3H, Ph), 5.70 (d, 1H, J 4.5, C6OH), 5.28 (d, 1H, J 11.0, CHO), 5.12<br />

(d, 1H, J 11.0, CHN), 4.80 (d, 1H, J 8.5, C5OH), 4.77 (dd, 1H, J 8.5, 5.5, H5), 4.03<br />

(dd. 1H, J 5.5, 3.5, H6), 2.87 (t, 1H, J 17.0, H3 axial ), 2.18 (dd, 1H, J 17.0, 5.0, H3 eq ),<br />

216.-2.07 (m, 1H, J 7.0, 2.5, CHMe 2 ), 2.01 (dt, 1H, J 17.0, 5.0, H2), 1.43 (s, 3H, Me),<br />

0.93 (d, 3H, J 8.5, CHMe a Me b ), 0.84 (d, 3H, J 8.5, CHMe a Me b ); 13 C-NMR (DMSO,<br />

125 MHz) δ 209.9 (C=O), 168.6 (C=N), 141.5 (ipso-Ph), 139.4 (ipso-Ph), 128.8 (meta-<br />

Ph), 128.7 (meta-Ph), 128.5 (para-Ph), 127.5 (para-Ph), 126.5 (ortho-Ph), 126.2<br />

(ortho-Ph), 87.4 (CHO), 79.3 (C6), 77.1 (CHN), 75.5 (C5), 46.1 (C1), 45.1 (C2), 38.0<br />

(C3), 26.3 (CHMe 2 ), 24.6 (CHMe a Me b ), 21.8 (Me), 18.4 (CHMe a Me b ).<br />

Synthesis of (4S,5S,6R)-4-((4R,5R)-4,5-diphenyloxazolinyl)-6-hydroxy-5-<br />

isopropyl-4-methylcyclohex-2-enone (276)<br />

Ph Ph<br />

Ph Ph Ph Ph<br />

O<br />

N<br />

O<br />

N<br />

O<br />

N<br />

OMe<br />

OsO 4 , NMO, t-BuOH/H 2 O 1<br />

6<br />

5<br />

2<br />

3<br />

4 OH<br />

O<br />

6<br />

5<br />

1<br />

2<br />

3<br />

276 283<br />

4 OH<br />

O<br />

General procedure 5 was employed using enol ether 102b (700 mg, 1.80 mmol), OsO 4<br />

(4.5 mg, 0.018 mmol), NMO (458 mg, 3.6 mmol), in t-BuOH (15 cm 3 ) and water (3.7<br />

cm 3 ). Upon complete reaction of starting material (c. 40 hr), sodium metabisulfite (1.0<br />

cm 3 , 5% w/w aq. solution) was added. Purification by flash chroma<strong>to</strong>graphy (8%<br />

EtOAc in petrol) yielded enone 276 (651 mg, 93%) as a yellow oil and dienone 283<br />

(28 mg, 4%) as a colourless oil.<br />

276 R f : 0.14 (4:1 petrol:EtOAc); [α] 25 D : +256 (c = 1.2, CH 2 Cl 2 ); MS m/z (CI+): 390<br />

(100%, MH + ), 391 (27%, (M+1)H + ), 196 (5%, [M-Ph 2 CHO]H + ); HRMS (ESI+) m/z<br />

found 390.2074 (MH calcd. 390.2064); IR ν max (film)/cm -1 : 3474 (m, O-H), 2971 (w,<br />

C-H), 1686 (C=O), 1647 (C=N); 1 H-NMR (CDCl 3 , 400 MHz) δ 7.44-7.27 (m, 8H,<br />

248


Experimental for chapter 4.1<br />

Ph), 7.22-7.18 (m, 2H, Ph), 6.78 (d, 1H, J 10.0, H6), 6.18 (d, 1H, J 10.0, H5), 5.22 (d,<br />

1H, J 10.5, CHO), 5.09 (d, 1H, J 10.5, CHN), 4.68 (dd, 1H, J 13.0, 2.0, H3), 3.62* (d,<br />

1H, J 2.0, OH), 2.40 (p, 1H, J 7.5, CHMe 2 ), 1.99 (d, 1H, J 13.0, H2), 1.63 (s, 3H, Me),<br />

1.70 (d, 3H, J 7.5, CHMe a Me b ), 1.15 (d, 3H, J 7.5, CHMe a Me b ); 13 C-NMR (CDCl 3 ,<br />

100 MHz) δ 201.7 (C=O), 167.4 (C=N), 153.9 (C6), 140.5 (ipso-Ph), 138.5 (ipso-Ph),<br />

129.0, 128.9, 128.8, 127.9, 126.7, 126.2, 124.7 (Ph), 90.1 (CHO), 77.9 (CNH), 55.2<br />

(COH), 44.1 (C1), 27.1 (CHMe 2 ), 25.9 (CHMe a Me b ), 25.5 (CHMe a Me b ), 17.3 (Me).<br />

283 R f : 0.18 (4:1 petrol:EtOAc); [α] 21 D : +197.5 (c = 2.1, CHCl 3 ); MS m/z (CI+): 388<br />

(100%, MH + ), 389 (27%, (M+1)H + ), 194 (70%, [M-Ph 2 CHO]H + ); HRMS (ESI+) m/z<br />

found 388.1911 (MH calcd. 388.1907); IR ν max (film)/cm -1 : 3391 (m, O-H), 2931 (w,<br />

C-H), 1643 (C=O); 1 H-NMR (CDCl 3 , 300 MHz) δ 7.43-7.26 (m, 8H, Ph), 7.24-7.18<br />

(m, 2H, Ph), 7.04 (d, 1H, J 10.0, H6), 6.64 (s, 1H, OH), 6.49 (d, 1H, J 10.0, H5), 5.23<br />

(d, 1H, J 8.5, CHO), 5.18 (d, 1H, J 8.5, CHN), 2.61 (p, 1H, J 2.5, CHMe 2 ), 1.75 (s,<br />

3H, Me), 1.34 (d, 3H, J 7.0, CHMe a Me b ), 1.28 (d, 3H, J 7.0, CHMe a Me b ); 13 C-NMR<br />

(CDCl 3 , 75 MHz) δ 181.1 (C4), 167.1 (C=N), 152.8, 145.1 (C3, C6), 141.2 (ipso-Ph),<br />

138.8 (ipso-Ph), 136.0 (C5), 128.9 (meta-Ph), 128.9 (meta-Ph), 127.9 (para-Ph), 126.6<br />

(ortho-Ph), 126.5 (ortho-Ph), 125.6 (C2), 90.3 (CHO), 77.6 (CHN), 46.9 (CMe), 30.4<br />

(CHMe 2 ), 22.9 (Me), 19.9 (CHMe a Me b ), 19.4 (CHMe a Me b ).<br />

Synthesis of (1R,2R,5S,6S)-5-((4R,5R)-4,5-diphenyloxazolin-2-yl)-6-isopropyl-5-<br />

methylcyclohex-3-ene-1,2-diol (213)<br />

Ph Ph<br />

Ph Ph<br />

O<br />

N<br />

O<br />

N<br />

NaBH 4<br />

EtOH, 0 °C<br />

OH<br />

O<br />

6<br />

5<br />

1<br />

2<br />

3<br />

4 OH<br />

OH<br />

Sodium borohydride (24 mg, 0.63 mmol) was added in a single portion <strong>to</strong> a stirred<br />

solution of enone 276 (220 mg, 0.57 mmol) in ethanol (6 cm 3 ) at 0 °C. When judged<br />

complete by TLC (PMA stain c. 6 hr) acetic acid was added <strong>to</strong> the cooled reaction<br />

mixture until effervescence ceased and warmed <strong>to</strong> room temperature. <strong>The</strong> solvent was<br />

removed from the reaction mixture, which was partitioned between water (10 cm 3 ) and<br />

CH 2 Cl 2 (20 cm 3 ) and the aqueous layer further washed (2 x 20 cm 3 CH 2 Cl 2 ) and the<br />

249


Experimental for chapter 4.1<br />

combined organic layers washed with brine before being dried over sodium sulphate.<br />

Removal of solvent gave a white crystalline solid which was purified by<br />

recrystallisation from diethyl ether <strong>to</strong> give colourless cubes of allyl alcohol 213 (216<br />

mg, 98%)<br />

R f : 0.31 (1:1, petrol:EtOAc); Mpt: 155-156 ºC (Et 2 O); [α] 25 D : +174 (c = 1.0, CHCl 3 );<br />

MS m/z (CI+) 392 (100%, MH + ), 393 (24%, (M+1)H + ), 303 (15%, [M-PhCH] + ), 285<br />

(22%, [M-PhCHO] + ); HRMS: found 392.2228, MH requires 392.2220; Microanalysis<br />

found (%): C 75.03, H 7.56, N 3.48, C 25 H 29 NO 3 requires (%): C 76.70, H 7.47, N 3.58;<br />

IR ν max (film)/cm⎯¹ 3359 (br, OH), 2970 (m, C-H), 1638 (C=N), 1050 (C-OH); ¹H-<br />

NMR (CDCl 3 , 500 MHz) δ 7.33-7.25 (m, 5H, Ph), 7.24-7.20 (m, 1H, Ph), 7.20-7.16<br />

(m, 2H, Ph), 7.15-7.11 (m, 2H, Ph), 5.53 (d, 1H, J 10.0, H6), 5.44 (d, 1H, J 10.0, H5),<br />

5.07 (d, 1H, J 10.5, CHOPh), 4.94 (d, 1H, J 10.5, CHNPh), 3.93-3.87 (m, 2H, H4, H3),<br />

3.32 (br s, 1H, OH), 2.44 (br s, 1H, OH), 2.23 (p, 1H, J 7.0, CHMe 2 ), 1.51 (d, 1H, J<br />

10.5, H2), 1.37 (s, 3H, Me), 1.09 (d, 3H, J 7.0, CHMe a Me b ), 1.00 (d, 3H, J 7.0,<br />

CHMe a Me b ); ¹H-NMR (C 6 D 6 , 300 MHz) δ 7.28-7.22 (m, 2H, Ph), 7.20-7.03 (m, 8H,<br />

Ph), 5.64 (d, 1H, J 10.0, H6), 5.45 (dd, 1H, J 10.0, 2.0, H5), 5.12 (s, 2H, CHPh), 4.21<br />

(ddd, 1H, J 11.5, 7.5, 2.0, H3), 4.04 (br d, 1H, J 7.5, H4), 2.89 (br s, 2H, OH), 2.41 (p,<br />

1H, J 7.0, CHMe 2 ), 1.64 (d, 1H, J 11.5, H2), 1.40 (s, 3H, Me), 1.36 (d, 3H, J 7.0,<br />

CHMe a Me b ), 1.33 (d, 3H, J 7.0, CHMe a Me b ); ¹³C-NMR (CD 3 OD, 75.5 MHz) δ 171.8<br />

(C=N), 140.8 (ipso-Ph), 138.4 (ipso-Ph), 132.5 (C5), 129.2 (C6), 128.7, 127.9, 127.0,<br />

126.3 (Ph), 90.6 (CHOPh), 77.5 (CHNPh), 74.7 (CHOH), 72.7 (CHOH), 53.1 (C2),<br />

44.3 (C1), 26.9 (CHMe 2 ), 25.7 (CHMe a Me b ), 25.5 (Me), 17.0 (CHMe a Me b ).<br />

250


Experimental for chapter 4.1<br />

Synthesis of (1R,2S,5S,6S)-5-((4R,5R)-4,5-diphenyloxazolin-2-yl)-6-isopropyl-5-<br />

methylcyclohex-3-ene-1,2-diol (287)<br />

Ph Ph<br />

Ph Ph Ph Ph<br />

O<br />

N<br />

O<br />

N<br />

O<br />

N<br />

O<br />

OH<br />

CeCl 3. 7H 2 O, NaBH 4<br />

1<br />

MeOH, 0 °C<br />

OH<br />

OH<br />

213 287<br />

6<br />

5<br />

2<br />

3<br />

4 OH<br />

OH<br />

Sodium borohydride (24 mg, 0.63 mmol) was added portion wise <strong>to</strong> a stirred solution<br />

of enone 276 (100 mg, 0.26 mmol) and cerium trichloride heptahydrate (97 mg, 0.26<br />

mmol) in methanol (0.6 cm 3 ) at 0 °C. When judged complete by TLC (PMA stain c.<br />

20 min) ammonium chloride (sat. aqueous) was added <strong>to</strong> the cooled reaction mixture<br />

until. <strong>The</strong> solvent was removed from the reaction mixture, which was partitioned<br />

between water (3 cm 3 ) and CH 2 Cl 2 (10 cm 3 ) and the aqueous layer further washed (2 x<br />

10 cm 3 CH 2 Cl 2 ) and the combined organic layers washed with brine before being dried<br />

over sodium sulphate. Removal of solvent gave a mixture of diols 213 and 287 (100<br />

mg, 99%, 10:1 mixture) which were separated by recrystallisation from Et 2 O and<br />

forming the ace<strong>to</strong>nide of 287.<br />

213 – see page 250<br />

287 R f : 0.23 (2:1, petrol:EtOAc); [α] 22 D : +216 (c = 0.5, CHCl 3 ); MS m/z (CI+) 410<br />

(100%, MH + ), 411 (23%, (M+1)H + ); HRMS: found 432.2146, MNa requires<br />

432.2145; IR ν max (film)/cm⎯¹ 3359 (br), 2923 (m), 1639, 1451 (m), 1382, 1258; ¹H-<br />

NMR (CD 3 OD, 500 MHz) 7.43-7.30 (m, 8H, Ph), 7.27-7.23 (m, 2H, Ph), 5.92 (dd, 1H,<br />

J 5.0, 10.0, H5), 5.72 (d, 1H, J 10.0, H6), 5.24 (d, 1H, J 10.5, CHOPh), 5.02 (d, 1H, J<br />

10.5, CHNPh), 4.21 (dd, 1H, J 12.0, 4.5, H3), 4.06 (t, 1H, J 4.5, H4), 2.73 (sept, 1H, J<br />

7.0, CHMe2), 1.84 (d, 1H, J 12.0, H2), 1.48 (s, 3H, Me), 1.19 (d, 3H, J 7.0,<br />

CHMe A Me B ), 1.12 (d, 3H, J 7.0, CHMe A Me B ); ¹³C-NMR (CDCl 3 , 125 MHz) δ 169.5<br />

(C=N), 140.9 (ipso-Ph), 138.9 (ipso-Ph), 137.5 (C5), 128.8 (C6), 128.7, 128.5, 127.7,<br />

126.8 , 126.1, 125.7 (Ph), 90.0 (CHOPh), 78.0 (CHNPh), 69.0 (C3), 66.7 (C4), 48.7<br />

(C2), 44.2 (C1), 26.7 (Me), 26.4 (CHMe 2 ), 26.0 (Me), 17.5 (CHMe a Me b ).<br />

251


Experimental for chapter 4.1<br />

Synthesis of (2R,3S,4S)-4-((4R,5R)-4,5-diphenyloxazolinyl)-2-hydroxy-3-<br />

isopropyl-4-methylcyclohexanone (288)<br />

Ph Ph<br />

Ph Ph<br />

O<br />

N<br />

DIBAlH, CH 2 Cl 2<br />

O<br />

N<br />

−78 °C<br />

OH<br />

OH<br />

O<br />

O<br />

A solution of DIBAlH (0.18 cm 3 , 1M in CH 2 Cl 2 ) was added drop wise <strong>to</strong> a stirred<br />

solution of oxazoline 276 (60 mg, 0.15 mmol) in CH 2 Cl 2 (2 cm 3 ) at –78 °C under a<br />

nitrogen atmosphere <strong>to</strong> give a clear yellow solution. After 90 min, methanol (0.5 cm 3 )<br />

was added in a single portion <strong>to</strong> the cooled solution followed by ammonium chloride<br />

(sat. aq. 2 cm 3 ) and the reaction warmed <strong>to</strong> rt. <strong>The</strong> resulting solution was partitioned<br />

between water (2 cm 3 ) and EtOAc (10 cm 3 ) and the aqueous layer was extracted with<br />

EtOAc (3 x 10 cm 3 ) and the combined organic layers dried with sodium sulfate and<br />

reduced under vacuum. Flash chroma<strong>to</strong>graphy (petrol <strong>to</strong> 4:1 petrol:EtOAc) yielded<br />

ke<strong>to</strong>ne 288 (8 mg, 15%) as a colourless oil and starting material (35 mg, 58%).<br />

R f : 0.49 (2:1, petrol:EtOAc); [α] 22 D : –132 (c = 0.8, CHCl 3 ); MS m/z (CI+) 392 (100%,<br />

MH + ), 393 (25%, (M+1)H + ), 180 (53%), 305 (13%); HRMS: found 392.2227, MH<br />

requires 392.2220; IR ν max (film)/cm⎯¹ 3414 (br, O-H), 2928 (m, C-H), 1710 (C=O),<br />

1644 (C=N), 1451 (m), 1112 (m), 1085 (m), 1058 (m); ¹H-NMR (CDCl 3 , 500 MHz) δ<br />

7.44-7.28 (m, 8H, Ph), 7.24-7.20 (m, 2H, Ph), 5.21 (d, 1H, J 9.5, CHOPh), 5.11 (d, 1H,<br />

J 9.5, CHNPh), 4.68 (dd, 1H, J 12.0, 2.0, H3), 3.70 (d, 1H, J 2.0, OH), 3.39 (tdd, 1H, J<br />

14.0, 6.5, 1.0, H5 ax ), 2.52 (ddd, 1H, J 14.0, 4.5, 2.5, H5 eq ), 2.42 (ddd, 1H, J 14.0, 6.5,<br />

2.5, H6 eq ), 2.32 (p, 1H, J 7.0, CHMe 2 ), 1.79 (td, 1H, J 14.0, 4.5, H6 ax ), 1.57 (d, 1H, J<br />

12.0, H2), 1.50 (s, 3H, Me), 1.18-1.12 (m, 6H, CHMe 2 ); ¹³C-NMR (CDCl 3 , 125 MHz)<br />

δ 212.8 (C4), 170.0 (C=N), 141.3 (ipso-Ph), 139.5 (ipso-Ph), 129.0 (meta-Ph), 128.9<br />

(meta-Ph), 128.6 (para-Ph), 127.8 (para-Ph), 126.6 (ortho-Ph), 126.0 (ortho-Ph), 88.8<br />

(COPh), 78.2 (CNPh), 74.6 (C3), 59.8 (C2), 41.3 (C1), 39.3 (C5), 36.7 (C6), 28.2<br />

(CHMe 2 ), 26.6, 26.2, 17.9 (Me).<br />

252


Experimental for chapter 4.1<br />

Synthesis of (1R,2R,5S,6S)-5-((4R,5R)-4,5-diphenyloxazolin-2-yl)-1,2-<br />

bis(benzyloxy)-6-isopropyl-5-methylcyclohex-3-ene (289)<br />

Ph Ph<br />

Ph Ph<br />

O<br />

OH<br />

N<br />

OH<br />

BnBr, DMF, NaH<br />

n-Bu 4 NI<br />

6<br />

5<br />

O<br />

1<br />

N<br />

2<br />

3<br />

4 OBn<br />

OBn<br />

Adapted from the method of Provelenghi, 19 sodium hydride (25 mg, 0.62 mmol) was<br />

added slowly <strong>to</strong> a solution of benzyl bromide (0.1 cm 3 , 0.84 mmol), diol 213 (52 mg,<br />

0.13 mmol) and tetrabutylammonium iodide (4 mg, 0.01 mmol) in DMF (1.5 cm 3 )<br />

whilst the reaction mixture was maintained at ambient temperature. When the reaction<br />

was judged complete (c. 18 hr) aqueous ammonium chloride (saturated, 0.1 cm 3 ) was<br />

added <strong>to</strong> the reaction, the solvent removed under vacuum and the resulting residue<br />

partitioned between water (2 cm 3 ) and CH 2 Cl 2 (6 cm 3 ). <strong>The</strong> aqueous phase was<br />

washed with further CH 2 Cl 2 (2 x 5 cm 3 ) and the combined organic phases dried over<br />

sodium sulphate, before purification by flash chroma<strong>to</strong>graphy (9:1 <strong>to</strong> 4:1<br />

petrol:EtOAc) yielded benzyl ether 289 (54 mg, 72%) as a colourless oil.<br />

R f : 0.45 (4:1, petrol:EtOAc); [α] 20 D : +85 (c = 2.0, CH 2 Cl 2 ); MS m/z (ES+) 572 (100%,<br />

MH + ), 573 (40%, (M+1)H + ), 594 (7%, MNa + ), 465 (6%, [M-OBn]H + ); HRMS: found<br />

572.3150, MH requires 572.3159; IR ν max (film)/cm⎯¹ 3030 (m, C-H), 1646 (C=N),<br />

1453; ¹H-NMR (CDCl 3 , 500 MHz) δ 7.47-7.24 (m, 20H, Ph), 5.85 (dd, 1H, J 10.0,<br />

1.5, H5, H6), 5.82 (dd, 1H, J 10.0, 1.5, H5, H6), 5.23 (d, 1H, J 10.0, CHOPh), 5.13 (d,<br />

1H, J 11.5, OBn), 5.10 (d, 1H, J 10.0, CHNPh), 4.72 (d, 1H, J 11.5, OBn'), 4.65 ("t",<br />

2H, J 11.5, OBn, OBn'), 4.35 (d, 1H, J 6.5, H4), 4.16 (dd, 1H, J 10.0, 6.5, H3), 2.28 (p,<br />

1H, J 7.0, CHMe 2 ), 1.88 (d, 1H, J 10.0, H2), 1.52 (s, 3H, Me), 1.16 (d, 3H, J 7.0, i-Pr),<br />

1.01 (d, 3H, J 7.0, i-Pr); ¹³C-NMR (CDCl 3 , 75.5 MHz) δ 170.1, 141.4, 139.2, 138.5,<br />

134.0, 128.8, 128.7, 128.4, 128.3, 128.2, 127.8, 127.6, 127.5, 127.1, 126.7, 126.3,<br />

126.0, 89.9, 82.8, 78.1, 77.8, 73.0, 70.4, 52.2, 43.9, 27.4, 26.4, 26.0, 18.2.<br />

253


Experimental for chapter 4.1<br />

Synthesis of (1S,2R,3S,4R,5R,6S)-5-((4R,5R)-4,5-diphenyloxazolin-2-yl)-3,4-epoxy-<br />

6-isopropyl-5-methylcyclohexane-1,2-diol (216)<br />

Ph Ph<br />

Ph Ph<br />

O<br />

N<br />

O<br />

N<br />

OH<br />

OH<br />

mCPBA, CH 2 Cl 2<br />

−40 °C - rt<br />

O<br />

6<br />

5<br />

1<br />

2<br />

3<br />

4 OH<br />

OH<br />

mCPBA (192 mg, 50%, 0.56 mmol) was added in a single portion <strong>to</strong> a vigorously<br />

stirred solution of allyl alcohol 213 (110 mg, 0.28 mmol) at 0 °C in CH 2 Cl 2 (3 cm 3 ).<br />

After 6 hr, aqueous sodium sulfite (1 cm 3 sat.) was added and the reaction warmed <strong>to</strong><br />

ambient temperature. <strong>The</strong> reaction mixture was washed with aqueous sodium<br />

bicarbonate (2 cm 3 saturated) and the aqueous phase extracted with further CH 2 Cl 2 (3 x<br />

10 cm 3 ). <strong>The</strong> combined organic layers dried over anhydrous sodium sulfate, and the<br />

solvent removed under vacuum <strong>to</strong> yield epoxide 216 (113 mg, 99%) as a colourless oil.<br />

R f : 0.14 (1:1, petrol:EtOAc); [α] 26 D : 109.3 (c = 1.8, CH 2 Cl 2 ); MS m/z (EI+) 408<br />

(100%, MH + ), 409 (16%, (M+1)H + ), 430 (22%, MNa + ); HRMS: found 408.2179, MH<br />

requires 408.2169; IR ν max (film)/cm⎯¹ 3389 (br, OH), 2928 (m, C-H), 1637 (C=N),<br />

1454 (m), 1056; ¹H-NMR (CDCl 3 , 500 MHz) δ 7.41-7.33 (m, 7H, Ph), 7.32-7.28 (m,<br />

1H, Ph), 7.26-7.23 (m, 1H, Ph), 5.26 (d, 1H, J 9.0, CHOPh), 5.14 (d, 1H, J 9.0,<br />

CHNPh), 4.06 (dd, 1H, J 11.0, 8.0, H3), 3.81 (dd, 1H, J 8.0, 1.5, H4), 3.46 (dd, 1H, J<br />

4.0, 1.5, H5), 3.30 (d, 1H, J 4.0, H6), 2.24 (br s, 1H, OH), 2.00 (pd, 1H, J 7.0, 1.0,<br />

CHMe 2 ), 1.59 (s, 3H, Me), 1.39 (dd, 1H, J 11.0, 1.5, H2), 1.11 (d, 3H, J 7.0,<br />

CHMe A Me B ), 1.04 (d, 3H, J 7.0, CHMe A Me B ); ¹³C-NMR (CDCl 3 , 125 MHz) δ 168.9<br />

(C=N), 141.5 (ipso-Ph), 139.1 (ipso-Ph), 128.8 (Ph), 128.7 (Ph), 128.6 (Ph), 127.7<br />

(para-Ph), 126.9 (Ph), 126.8 (Ph), 89.7 (CHOPh), 77.6 (CHNPh), 75.9 (CHOH), 71.4<br />

(CHOH), 61.0 (C6), 56.0 (C5), 53.7 (C2), 42.9 (C1), 28.9 (CHMe 2 ), 27.1<br />

(CHMe A Me B ), 25.4 (Me), 19.0 (CHMe A Me B ).<br />

254


Experimental for chapter 4.1<br />

Synthesis of (1S,2R,3S,4R,5R,6S)-1,2-bis(benzyloxy)-5-((4R,5R)-4,5-<br />

diphenyloxazolin-2-yl)-3,4-epoxy-6-isopropyl-5-methylcyclohexane (292)<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

O<br />

OH<br />

N<br />

OH<br />

BnBr, DMF, NaH<br />

n-Bu 4 NI<br />

O<br />

O N<br />

O N<br />

1<br />

6 2<br />

3<br />

5<br />

4<br />

OBn<br />

O<br />

1<br />

6 2<br />

3<br />

5<br />

4<br />

OBn<br />

OBn<br />

292 291<br />

OH<br />

Adapted from the method of Provelenghi, 19 sodium hydride (7 mg, 0.16 mmol) was<br />

added slowly <strong>to</strong> a solution of benzyl bromide (40 µl, 0.29 mmol), diol 213 (30 mg,<br />

0.07 mmol) and tetrabutylammonium iodide (1 mg, 0.003 mmol) in DMF (0.8 cm 3 )<br />

whilst the reaction mixture was maintained at ambient temperature. When the reaction<br />

was judged complete (c. 16 hr) aqueous ammonium chloride (sat. 0.1 cm 3 ) was added<br />

<strong>to</strong> the reaction, the solvent removed under vacuum and the resulting residue partitioned<br />

between water (2 cm 3 ) and CH 2 Cl 2 (6 cm 3 ). <strong>The</strong> aqueous phase was washed with<br />

further CH 2 Cl 2 (2 x 5 cm 3 ) and the combined organic phases dried over sodium<br />

sulphate, before purification by flash chroma<strong>to</strong>graphy (19:1 <strong>to</strong> 3:1 petrol:EtOAc)<br />

yielded alcohol 291 (24 mg, 68%) and dibenzyl ether 292 (4 mg, 10%) as colourless<br />

oils.<br />

292 R f : 0.23 (4:1, petrol:EtOAc); [α] 23 D : +85 (c = 2, CHCl 3 ); MS m/z (ES+) 588<br />

(100%, MH + ), 610 (37%, (M+1)H + ), 610 (80%, MNa + ); HRMS: found 588.3106, MH<br />

requires 588.3108; IR ν max (film)/cm⎯¹ 2924 (C-H), 1995 (m), 1640, 1454, 1078; ¹H-<br />

NMR (CDCl 3 , 500 MHz) δ 7.41-7.24 (m, 20H, Ph), 5.29 (d, 1H, J 8.5, CHNPh), 5.14<br />

(d, 1H, J 8.5, CHOPh), 5.05 (d, 1H, J 11.5, OBn), 4.81 (d, 1H, J 11.5, OBn'), 4.76 (d,<br />

1H, J 11.5, OBn'), 4.59 (d, 1H, J 11.5, OBn), 4.07 (dd, 1H, J 9.0, 7.0, H3), 3.99 (d, 1H,<br />

J 7.0, H4), 3.45 (d, 1H, J 4.0, H6), 3.36 (d, 1H, J 4.0, H5), 1.98 (p, 1H, J 7.0, CHMe 2 ),<br />

1.63-1.57 (m, 4H, H2, Me), 1.11 (d, 3H, J 7.0, i-Pr), 1.03 (d, 3H, J 7.0, i-Pr); ¹³C-<br />

NMR (CDCl 3 , 75.5 MHz) δ 169.5, 141.8, 139.5, 139.3, 138.1, 128.7, 128.7, 128.5,<br />

128.4, 128.2, 128.0, 127.7, 127.6, 127.2, 127.1, 126.9, 126.8, 89.7, 83.8, 77.8, 73.2,<br />

72.1, 60.5, 54.0, 53.3, 43.1, 29.7, 26.8, 25.5, 19.8.<br />

255


Experimental for chapter 4.1<br />

291 R f : 0.11 (4:1, petrol:EtOAc); [α] 27 D : +89 (c = 1.2, CHCl 3 ); MS m/z (ES+) 520<br />

(100%, MNa + ), 521 (34%, (M+1)Na + ), 498 (75%, MH + ); HRMS: found 498.2632,<br />

MH requires 498.2639; IR ν max (film)/cm⎯¹ 3333 (br, O-H), 2954 (C-H), 1638, 1453,<br />

1076; ¹H-NMR (CDCl 3 , 500 MHz) δ 7.35-7.15 (m, 15H, Ph), 5.19 (d, 1H, J 9.0,<br />

CHOPh), 5.05 (d, 1H, J 9.0, CHNPh), 4.78 (d, 1H, J 11.5, OBn), 4.63 (d, 1H, J 11.5,<br />

OBn), 4.15-4.09 (m, 1H, H3), 3.63 (dd, 1H, J 8.0, 1.0, H4), 3.38 (dd, 1H, J 4.0, 1.0,<br />

H5), 3.21 (d, 1H, J 4.0, H6), 2.28 (s, 1H), 2.17 (d, 1H, J 2.0, C3OH), 1.90 (pd, 1H, J<br />

7.0, 1.0, CHMe 2 ), 1.50 (s, 3H), 1.36 (dd, 1H, J 11.0, 1, H2), 1.01 (d, 3H, J 7.0, i-Pr),<br />

0.94 (d, 3H, J 7.0, i-Pr); ¹³C-NMR (CDCl 3 , 75.5 MHz) δ 169.3 (C=N), 141.7 (ipso-<br />

Ph), 139.2 (ipso-Ph), 138.0 (ipso-Ph), 129.0, 128.7, 128.7, 128.6, 128.5, 128.2, 127.9,<br />

127.6, 126.9 (Ph), 89.8 (CHOPh), 83.0, 77.5, 71.9, 69.1, 60.4, 53.4, 53.0, 42.7, 29.2,<br />

26.9, 25.7, 18.7.<br />

Synthesis of (1S,2S,3R,4S,5R,6R)-5,6-bis(benzyloxy)-3-((4R,5R)-4,5-<br />

diphenyloxazolin-2-yl)-4-isopropyl-3-methylcyclohexane-1,2-diol (300)<br />

Ph Ph<br />

Ph Ph<br />

O<br />

N<br />

O<br />

N<br />

OsO 4 , NMO, CH 2 Cl 2<br />

HO<br />

6<br />

1<br />

2<br />

OBn<br />

OBn<br />

HO<br />

5<br />

3<br />

4 OBn<br />

OBn<br />

General procedure 5 was employed using olefin 289 (26 mg, 0.04 mmol), OsO 4 (0.2<br />

mg, 2 mol %), NMO (12 mg, 0.1 mmol), in CH 2 Cl 2 (0.5 cm 3 ). Upon complete<br />

reaction of starting material (c. 9 d), sodium metabisulfite (0.1 cm 3 , 5% w/w aq.<br />

solution) was added. Purification by flash chroma<strong>to</strong>graphy (10% EtOAc in petrol)<br />

yielded diol 300 (26 mg, 96 %) as a colourless oil.<br />

R f : 0.09 (4:1, petrol:EtOAc); [α] 26 D : +35 (c = 1.2, CHCl 3 ); MS m/z (ES+) 606.4<br />

(100%, MH + ), 607.4 (48%, (M+1)H + ), 628.4 (46%, MNa + ); HRMS: found 606.3222,<br />

MH requires 606.3214; IR ν max (film)/cm⎯¹ 3441 (br, OH), 2948 (m, C-H), 1642<br />

(C=N), 1453, 1069; ¹H-NMR (CDCl 3 , 500 MHz) δ 7.37-7.18 (m, 16H, Ph), 7.16-7.08<br />

(m, 4H, Ph), 5.09-5.06 (m, CHOPh, OBn), 4.99 (d, J 9.0, CHNPh), 4.82 (d, J 11.5,<br />

OBn'), 4.66 ("t", 2H, J 11.5, OBn, OBn'), 4.29 (dd, 1H, J 10.0, 3.0, H5), 4.09 (dd, 1H,<br />

J 11.0, 9.0, H3), 4.00 (d, 1H, J 3, H6), 3.88-3.82 (m, 1H, H4), 2.62 (br s, 1H, OH),<br />

256


Experimental for chapter 4.1<br />

2.30 (br s, 1H, OH), 2.10 (pd, 1H, J 7.0, 1.0, CHMe 2 ), 1.99 (dd, 1H, J 11.0, 1.0, H2),<br />

1.53 (s, 3H, Me), 1.11 (d, 3H, J 7.0, CHMe A Me b ), 1.01 (d, 3H, J 7.0, CHMe a Me B ); ¹³C-<br />

NMR (CDCl 3 , 75.5 MHz) δ 169.4 (C=N), 141.4 (ipso-Ph), 139.5 (ipso-Ph), 139.2<br />

(ipso-Ph), 138.5 (ipso-Ph), 129 (para-Ph), 128.9 (Ph), 128.8 (Ph), 128.7 (Ph), 128.5<br />

(para-Ph), 128.2 (Ph), 128.2 (para-Ph), 127.9 (Ph), 127.7 (para-Ph), 127.1, 127,<br />

126.6, 126.1 (Ph), 88.8 (CHOPh), 85.9 (CHOR), 80.1 (CHOR), 78.2 (CHNPh), 75.6<br />

(OBn), 75.1 (CHOR), 72.8 (OBn), 71.9 (CHOR), 49.1 (C2), 45.7 (C1), 27.6 (CHMe 2 ),<br />

26.7 (Me), 22.4 (CHMe A Me b ), 19.5 (CHMe a Me B ).<br />

Synthesis of (1R,2S,3S,4S,5R,6S)-2,3,4,5-tetra(benzyloxy)-1-((4R,5R)-4,5-<br />

diphenyloxazolin-2-yl)-6-isopropyl-1-methylcyclohexane (302)<br />

HO<br />

HO<br />

Ph<br />

O<br />

N<br />

OBn<br />

Ph<br />

OBn<br />

BnBr, DMF, NaH<br />

n-Bu 4 NI<br />

BnO<br />

BnO<br />

Ph<br />

5<br />

O<br />

6<br />

1<br />

N<br />

Ph<br />

2<br />

OBn<br />

3<br />

4 OBn<br />

BnO<br />

HO<br />

Ph<br />

5<br />

O<br />

6<br />

1<br />

N<br />

Ph<br />

2<br />

3<br />

4 OBn<br />

OBn<br />

Adapted from the method of Provelenghi, 19 sodium hydride (5 mg, 0.12 mmol) was<br />

added slowly <strong>to</strong> a solution of benzyl bromide (20 µl, 0.15 mmol), diol 300 (23 mg,<br />

0.04 mmol) and tetrabutylammonium iodide (1 mg, 0.003 mmol) in DMF (0.8 cm 3 )<br />

whilst the reaction mixture was maintained at ambient temperature. When the reaction<br />

was judged complete (c. 16 hr) aqueous ammonium chloride (saturated, 0.1 cm 3 ) was<br />

added <strong>to</strong> the reaction, the solvent removed under vacuum and the resulting residue<br />

partitioned between water (2 cm 3 ) and CH 2 Cl 2 (6 cm 3 ). <strong>The</strong> aqueous phase was<br />

washed with further CH 2 Cl 2 (2 x 5 cm 3 ) and the combined organic phases dried over<br />

sodium sulphate, before purification by flash chroma<strong>to</strong>graphy (19:1 <strong>to</strong> 9:1<br />

petrol:EtOAc) yielded alcohol 301 (14 mg, 54%), perbenzyl ether 302 (10 mg, 33%)<br />

and starting material (2 mg, 9%) as colourless oils.<br />

302 R f : 0.45 (9:1, petrol:EtOAc); [α] 24 D : +21 (c = 1, CHCl 3 ); MS m/z (ES+) 786<br />

(67%, MH + ), 808 (100%, MNa + ), 809 (52%, (M+1)Na + ); HRMS: found 786.4159,<br />

MH requires 786.4153; IR ν max (film)/cm⎯¹ 2930 (m, C-H), 1453 (m, C-Me), 1069; ¹H-<br />

NMR (CDCl 3 , 500 MHz) δ 7.36-7.10 (m, 30H, Ph), 5.20 (d, 1H, J 11.5, CHOPh), 5.12<br />

(s, 2H, OBn), 5.09 (d, 1H, J 11.5, CHNPh), 5.01 (d, 1H, J 10.5, OBn), 4.79-4.71 (m,<br />

257


Experimental for chapter 4.1<br />

3H, OBn), 4.69 (d, 1H, J 11.0, OBn), 4.65 (d, 1H, J 11.5, OBn), 4.22 (dd, 1H, J 10.0,<br />

8.5, H4), 4.18-4.10 (m, 2H, H5, H3), 4.02 (d, 1H, J 2.0, H6), 2.07 (pd, 1H, J 7.0, 1.5,<br />

CHMe 2 ), 2.01 (dd, 1H, J 11.0, 1.5, H2), 1.57 (s, 3H, Me), 1.13 (d, 3H, J 7.0,<br />

CHMe A Me b ), 1.08 (d, 3H, J 7.0, CHMe a Me B ); ¹³C-NMR (CDCl 3 , 75.5 MHz) δ 169.7<br />

(C=N), 141.7 (ipso-Ph), 139.7 (ipso-Ph), 139.6 (ipso-Ph), 138.9 (ipso-Ph), 138.8 (ipso-<br />

Ph), 138.7 (ipso-Ph), 128.9, 128.7, 128.7, 128.3, 128.3, 128.2, 128.1, 127.8, 127.7,<br />

127.4, 127.4, 127.1, 126.9, 126.5, 126.3 (Ph), 88.6 (CHOPh), 85.5, 82.3, 81.8, 80.7<br />

(C3, C4, C5, C6), 77.9 (CHNPh), 75.9 (OCH 2 Ph), 75.4 (OCH 2 Ph), 72.8 (OCH 2 Ph),<br />

72.7 (OCH 2 Ph), 49.1, 47.0 (C1, C2), 28.2 (CHMe 2 ), 27.3 (CHMe A Me b ), 23.2 (Me),<br />

19.4 (CHMe a Me B ).<br />

301 R f : 0.24 (4:1, petrol:EtOAc); [α] 27 D : +24 (c = 1, CHCl 3 ); MS m/z (ES+) 696<br />

(100%, MH + ), 697 (36%, (M+1)H + ), 718 (29%, MNa + ); HRMS: found 696.3681, MH<br />

requires 696.3686; IR ν max (film)/cm⎯¹ 3582 (O-H), 2924 (C-H), 1641 (C=N), 1453 (C-<br />

Me), 1069; ¹H-NMR (CDCl 3 , 500 MHz) δ 7.46-7.16 (m, 23H, Ph), 7.14-6.99 (m, 2H,<br />

Ph), 5.15 (d, 1H, J 9.0, CHOPh), 5.13 (d, 1H, J 11.5, OBn), 5.08 (d, 1H, J 9.0,<br />

CHNPh), 4.90 (d, 1H, J 11.0, OBn), 4.86 (d, 1H, J 11.0, OBn), 4.76 (dd, 2H, J 11.0,<br />

2.0, OBn), 4.73-4.67 (m, 2H, OBn), 4.25 (ddd, 1H, J 10.0, 5.5, 3.0, H5), 4.19 (dd, 1H,<br />

J 11.0, 8.5, H3), 4.00 (dd, 1H, J 10.0, 8.5, H4), 3.94 (d, 1H, J 3.0, H6), 2.11 (pd, 1H, J<br />

7.0, 1.5, CHMe 2 ), 2.02 (d, 1H, J 5.5, C5-OH), 2.01 (dd, J 11.0, 1.5, H2), 1.62 (s, 3H,<br />

Me), 1.16 (d, 3H, J 7.0, CHMe A Me b ), 1.11 (d, 3H, J 7.0, CHMe a Me B ); ¹³C-NMR<br />

(CDCl 3 , 125 MHz) δ 169.6 (C=N), 141.6 (ipso-Ph), 139.6 (ipso-Ph), 138.7 (ipso-Ph),<br />

138.5 (ipso-Ph), 128.9, 128.8, 128.6, 128.4, 128.2, 128.1, 127.9, 127.7, 127.1, 127.0,<br />

126.5, 126.2 (Ph), 88.8 (CHOPh), 86.4 (C4), 84.8 (C3), 80.5 (C6), 78.3 (CHNPh), 76.5<br />

(OCH 2 Ph), 75.1 (OCH 2 Ph), 72.8 (OCH 2 Ph), 72.7 (C5), 49.5 (C2), 47.3 (C1), 28.0,<br />

28.0 (CHMe 2 , CHMe A Me b ), 27.2 (Me), 19.7 (CHMe a Me B ).<br />

258


Experimental for chapter 4.1<br />

Synthesis of (1R,2S,3S,4S,5S,6S)-tetrakis(benzyloxy)5-((benzyloxy)methyl)-6-<br />

isopropyl-5-methylcyclohexane (304)<br />

BnO<br />

BnO<br />

Ph<br />

O<br />

N<br />

OBn<br />

Ph<br />

OBn<br />

i) MeOTf, then NaBH 4<br />

ii) H 3 O + 60 °C<br />

iii) NaBH 4<br />

BnO<br />

BnO<br />

HO<br />

6<br />

5<br />

1<br />

7<br />

2<br />

3<br />

4 OBn<br />

OBn<br />

General procedure 6 was used employing oxazoline 302 (20 mg, 0.025 mmol) and<br />

methyl triflate (6 µl, 0.05 mmol) for 20 hr. <strong>The</strong> crude oxazolidine was subjected <strong>to</strong><br />

general procedure 7, hydrolysis at 60 °C taking 7 days. <strong>The</strong> resulting crude alcohol<br />

was purified by flash column chroma<strong>to</strong>graphy (4:1 petrol:EtOAc) <strong>to</strong> give alcohol 304<br />

(9 mg, 60%) as a colourless oil.<br />

R f : 0.30 (40%, EtOAc in petrol); [α] 24 D : +135 (c = 1, CHCl 3 ); MS m/z (ES+) 430<br />

(100%, MNa + ), 408 (27%, MH + ), 838 (39%, 2MNa + ); HRMS: found 430.2349, MNa<br />

requires 430.2353; IR ν max (film)/cm⎯¹ 3364 (br, OH), 2947 (m), 2360 (w, C=C), 1453<br />

(m); ¹H-NMR (CDCl 3 , 500 MHz) δ 7.31-7.25 (m, 3H, Ar), 7.23-7.16 (m, 5H, Ar),<br />

7.05-7.00 (m, 2H, Ar), 6.06 (dd, 1H, J 10.0, 2.0, H5), 5.65 (dd, 1H, J 10.0, 2.0, H6),<br />

4.74 (d, 1H, J 9.0, CHOPh), 4.54 (s, 1H, CHON), 4.24 (dd, 1H, J 11.5, 7.0, H3), 3.95<br />

(br d, 1H, J 7.0, H4), 3.30 (d, 1H, J 9.0, CHNPh), 2.37 (s, 3H, NMe), 2.31-2.10 (m,<br />

3H, CHMe 2 & OH), 1.48 (d, 1H, J 11.5, H2), 1.29 (d, 3H, J 7.0, CHMe A Meb), 1.21-<br />

1.17 (m, 6H, Me & CHMeaMe B ); ¹³C-NMR (CDCl 3 , 75.5 MHz) δ 138.6 (ipso-Ph),<br />

137.6 (ipso-Ph), 134.7 (C5), 128.3 (C6), 128.1, 128.0, 127.8, 127.7, 126.4 (Ph), 99.9<br />

(CHON), 85.6 (CHOPh), 79.6 (CHNPh), 76.1 (C4), 74.1 (C3), 55.1 (C2), 48.6 (C1),<br />

41.9 (NMe), 27.3 (CHMeaMe B ), 25.9 (CHMe 2 ), 24.7 (Me), 17.9 (CHMe A Meb).<br />

259


Experimental for chapter 4.1<br />

Synthesis of (1R,2S,3S,4S,5S,6S)-5-(hydroxymethyl)-6-isopropyl-5-<br />

methylcyclohexane-1,2,3,4-tetraol (278)<br />

BnO<br />

BnO<br />

HO<br />

OBn<br />

OBn<br />

Pd(OH) 2 , MeOH<br />

H 2 , 20 bar<br />

Benzyl ether 304 (3 mg, 5 µmol) was dissolved in MeOH (0.5 cm 3 ) and passed<br />

through a Pd(OH) 2 H-Cube cartridge at 20 bar H 2 , flow rate 0.5 cm 3 min -1 . <strong>The</strong> solvent<br />

was removed from the resulting solution <strong>to</strong> yield pentaol 278 (1 mg, quant.) as<br />

colourless needles.<br />

HO<br />

HO<br />

OH<br />

OH<br />

OsO 4 , quinuclidine,<br />

MeSO 2 NH 2 ,<br />

K 2 CO 3 , K 3 Fe(CN) 6 ,<br />

t-BuOH/H 2 O<br />

HO<br />

HO<br />

HO<br />

HO<br />

5<br />

HO<br />

6<br />

1<br />

OH<br />

7<br />

2<br />

3<br />

OH<br />

4 OH<br />

OH<br />

Adapted from the method of Warren 20 osmium tetroxide (20 µl of 2.5% solution in t-<br />

BuOH) was added <strong>to</strong> a vigorously stirred orange solution of triol 312 (16 mg, 0.08<br />

mmol) in t-BuOH (0.4 cm 3 ), H 2 O (0.4 cm 3 ) with potassium ferricyanide (79 mg,<br />

ground, 0.24 mmol), potassium carbonate (33mg, 0.24 mmol), methyl sulfonamide (8<br />

mg, 0.08 mmol) and quinuclidine (1 mg, 0.01 mmol). When complete my TLC<br />

analysis (c. 72 hr) excess sodium sulfite was added, and the decolourised reaction<br />

mixture partitioned between EtOAc (5 cm 3 ) and water (2 cm 3 ), the aqueous layer was<br />

washed with EtOAc (5 x 5 cm 3 ), the combined organic extracts dried over anhydrous<br />

sodium sulfate and solvent removed <strong>to</strong> yield a white solid (16 mg). Flash column<br />

chroma<strong>to</strong>graphy (EtOAc <strong>to</strong> 1% MeOH in EtOAc) yields pentaol 278 (15 mg, 79%) as<br />

colourless needles.<br />

R f : 0.09 (EtOAc); Mpt: 175 ºC (MeOH); [α] 22 D : +7.2 (c = 1.0, MeOH); MS m/z (ES–)<br />

269 (100%, MCl 35- ), 271 (34%, MCl 37- ), 233 (32%, M – ), 467 (16%, 2M – ); HRMS:<br />

found 269.1179, MCl requires 269.1161; IR ν max (film)/cm⎯¹ 3364 (br, OH), 2943 (m),<br />

1021 (w); ¹H-NMR (D 2 O, 500 MHz) δ 3.81 (d, 1H, J 3.0, H6), 3.66 (dd, 1H, J 10.0,<br />

3.0, H5), 3.62-3.56 (m, 1H), 3.56-3.49 (m, 3H), 1.93 (p, 1H, J 7.0, CHMe 2 ), 1.48 (d,<br />

1H, J 11.5, H2), 1.06 (s, 3H, Me), 1.03 (d, 3H, J 7.0, i-Pr), 0.93 (d, 3H, J 7.0, i-Pr);<br />

260


Experimental for chapter 4.1<br />

¹³C-NMR (CD 3 OD, 75.5 MHz) δ 77.7 (CHOH), 76.3 (CHOH), 74.0 (CHOH), 72.6<br />

(CHOH), 65.8 (C7), 49.4 (C2), 45.3 (C1), 27.5 (CHMe 2 ), 26.9, 21.8, 18.7 (Me).<br />

Synthesis of (1S,2R,3S,4R,5R,6S)-5-(N-methyl-(4R,5R)-4,5-diphenyloxazolidin-2-<br />

yl)-3,4-epoxy-6-isopropyl-5-methylcyclohexane-1,2-diol (306) and<br />

(1S,2R,3S,4R,5R,6S)-2,3-epoxy-5-hydroxy-6-isopropyl-1-methylcyclohexane-δlac<strong>to</strong>ne<br />

(307)<br />

Ph Ph<br />

Ph Ph<br />

O<br />

O<br />

OH<br />

N<br />

OH<br />

O NMe<br />

MeOTf, then NaBH 4<br />

Me<br />

1<br />

1<br />

6 2 O<br />

2<br />

O<br />

O<br />

3<br />

O<br />

5 4 OH<br />

4<br />

OH<br />

306 307<br />

3<br />

OH<br />

General procedure 6 was used employing oxazoline 216 (101 mg, 0.25 mmol) and<br />

methyl triflate (56 µl, 0.50 mmol) for 16 hr. <strong>The</strong> solvent was removed, the aqueous<br />

layer washed with CH 2 Cl 2 (2 x 10 cm 3 ) and the combined organic phases dried over<br />

anhydrous sodium sulfate. Flash chroma<strong>to</strong>graphy (9:1 <strong>to</strong> 1:1 petrol:EtOAc) gave<br />

oxazolidine 306 (39 mg, 40%) and oxazolidine 307 (15 mg, 30%) as colourless oils.<br />

306 R f : 0.21 (2:1, petrol:EtOAc); [α] 23 D : +72 (c = 1.3, CHCl3); MS m/z (ES+) 424<br />

(23%, MH + ), 446 (100%, MNa + ), 447 (32%, (M+1)Na + ), 869 (40%, M 2 Na + ); HRMS:<br />

found 424.2483, MH requires 424.2482; IR ν max (film)/cm⎯¹ 3392 (br, O-H), 2928 (m,<br />

C-H), 2357 (m), 1456 (m, C-Me), 1068 (C-O-C); ¹H-NMR (CDCl 3 , 500 MHz) δ 7.31-<br />

7.28 (m, 5H, Ph), 7.26-7.22 (m, 2H, Ph), 7.21-7.16 (m, 1H, Ph), 7.11-7.07 (m, 2H, Ph),<br />

5.36 (d, 1H, J 9.5, CHOPh), 4.71 (s, 1H, CHNO), 4.16 (dd, 1H, J 11.5, 8.0H3), 3.68<br />

(dd, 1H, J 8.0, 1.5H4), 3.49 (d, 1H, J 4.0, H6), 3.43 (dd, 1H, J 4.0, 1.5, H5), 3.34 (d,<br />

1H, J 9.5, CHNPh), 2.41 (s, 3H, NMe), 2.16 (m, 1H, CHMe 2 ), 1.34 (d, 3H, J 7.0,<br />

CHMe A Me b ), 1.29-1.26 (m, 4H, Me, H2), 1.18 (d, 3H, J 7.0, CHMe a Me B ); ¹³C-NMR<br />

(CDCl 3 , 75.5 MHz) δ 139.9 (ipso-Ph), 138.2 (ipso-Ph), 128.6, 128.3, 128.0, 127.8,<br />

127.4, 126.1 (Ph), 101.5 (CHNO), 85.4 (CHOPh), 81.0 (CHNPh), 77.3 (C4), 72.0<br />

(C3), 61.0 (C6), 56.6 (C2), 55.3 (C5), 43.6 (C1), 42.1 (NMe), 27.6 (CHMe a Me B ), 26.4<br />

(CHMe 2 ), 24.9 (Me), 17.8 (CHMe A Me b ).<br />

261


Experimental for chapter 4.1<br />

307 R f : 0.24 (1:1, petrol:EtOAc); [α] 23 D : –72 (c = 0.5, CHCl 3 ); MS m/z (ES+) 213<br />

(4%, MH + ), 235 (100%, MNa + ), 236 (5%, (M+1)Na + ), 447 (10%, M 2 Na + ); HRMS:<br />

found 230.1389, MH requires 230.1387; IR ν max (film)/cm⎯¹ 3434 (br, O-H), 2928 (m,<br />

C-H), 1745 (C=O), 1453 (m, R-Me), 1058 (C-O-C); ¹H-NMR (CDCl 3 , 500 MHz) δ<br />

4.73 (t, 1H, J 3.5, H4), 4.35 (t, 1H, J 4.0, H3), 3.77 (dd, 1H, J 4.0, 3.0, H5), 3.36 (dd,<br />

1H, J 4.0, 1.0, H6), 2.09 (pd, 1H, J 7.0, 3.5, CHMe 2 ), 1.97 (s, 1H, OH), 1.72 (t, 1H, J<br />

4.0, H2), 1.43 (s, 3H, Me), 1.05 (d, 3H, J 7.0, i-Pr), 0.77 (d, 3H, J 7.0, i-Pr); ¹³C-NMR<br />

(CDCl 3 , 75.5 MHz, relaxation time 25 s) δ, 172.3 (C=O), 71.1 (CHOH), 67.7 (CHO-),<br />

53.9 (CHO-), 51.9 (CHO-), 48.1 (C2), 45.4 (C1), 26.1 (CH), 21.9, 16.4, 15.7 (Me).<br />

Synthesis of (1S,2R,3S,4R,5R,6S)-5-(hydroxymethyl)-3,4-epoxy-6-isopropyl-5-<br />

methylcyclohexane-1,2-diol (309)<br />

O<br />

Ph<br />

O<br />

OH<br />

Ph<br />

NMe<br />

OH<br />

HO<br />

7<br />

i) MeOTf, then NaBH 1<br />

4<br />

6 2<br />

ii) H 3 O + 60 °C<br />

O<br />

3<br />

iii) NaBH 4 5<br />

OH<br />

4 OH<br />

General procedure 3 was employed using oxazoline 216 (55 mg, 0.13 mmol) and<br />

methyl triflate (31 µl, 0.27 mmol) for 4 hr. <strong>The</strong> resulting crude oxazolidine was then<br />

subject <strong>to</strong> general procedure 4 and heated at 50 °C for 17 hr. <strong>The</strong> resulting oil was<br />

purified by flash chroma<strong>to</strong>graphy (3:2 <strong>to</strong> 1:1 petrol:EtOAc) <strong>to</strong> give triol 309 (24 mg,<br />

83%) as colourless needles.<br />

R f : 0.28 (EtOAc); Mpt: 116-117 ºC (H 2 O/MeOH); [α] 24 D : +312 (c = 0.5, CHCl 3 ); MS<br />

m/z (ES–) 431 (100%, [2M-H] – ), 251 (52%, [M+Cl] – ), 215 (27%, [M-H] – ); IR ν max<br />

(film)/cm⎯¹ 3369 (br, OH), 2963 (m, C-H), 1039 (C-O-C); ¹H-NMR (CD 3 OD, 500<br />

MHz) δ 3.80 (d, 1H, J 10.0, H7 a ), 3.67 (dd, 1H, J 8.0, 1.5, H4), 3.59 (dd, 1H, J 11.5,<br />

8.0, H3), 3.46 (d, 1H, J 10.0, H7 b ), 3.35 (dd, 1H, J 4.0, 1.5, H5), 3.03 (d, 1H, J 4.0,<br />

H6), 1.88 (p, 1H, J 7.0, CHMe 2 ), 1.20 (d, 1H, J 11.5, H2), 1.16 (s, 3H, Me), 1.09 (d,<br />

3H, J 7.0, i-Pr), 1.01 (d, 3H, J 7.0, i-Pr); ¹³C-NMR (CD 3 OD, 75.5 MHz) δ 76.9<br />

(CHOH), 71.0 (CHOH), 65.4 (C7), 61.9 (C6), 58.8 (C5), 54.5 (C2), 41.6 (C1), 28.1<br />

(CHMe 2 ), 27.3 (i-Pr), 22.4 (Me), 18.4 (i-Pr).<br />

262


Experimental for chapter 4.2<br />

5.6 Experimental Procedures for Chapter 4.2<br />

Synthesis of (1S*,4S*,5S*)-1-(benzyloxy)-4-((benzyloxy)methyl)-5-isopropyl-4-<br />

methylcyclohex-2-ene (313)<br />

HO<br />

BnO<br />

NaH, BnBr, DMF<br />

(±)<br />

OH<br />

(±)<br />

OBn<br />

Sodium hydride (10 mg, 0.24 mmol) was added slowly <strong>to</strong> a solution of benzyl bromide<br />

(40 µl, 0.35 mmol) and diol 225 (16 mg, 0.08 mmol) in DMF (1 cm 3 ) whilst the<br />

reaction mixture was maintained at ambient temperature. When the reaction was<br />

judged complete (c. 16 hr) methanol (0.1 cm 3 ) was added, the solvent removed under<br />

vacuum and the resulting residue partitioned between water (2 cm 3 ) and CH 2 Cl 2 (6<br />

cm 3 ). <strong>The</strong> aqueous phase was washed with further CH 2 Cl 2 (2 x 5 cm 3 ) and the<br />

combined organic phases dried over sodium sulphate, before purification by flash<br />

chroma<strong>to</strong>graphy (petrol <strong>to</strong> 19:1 petrol:EtOAc) <strong>to</strong> give 313 (27 mg, 93%) as a<br />

colourless oil.<br />

R f : 0.48 (9:1, petrol:EtOAc); MS m/z (CI+) 382 (100%, MNH + 4 ), 383 (26%,<br />

(M+1)NH + 4 ); HRMS: found 382.2740, MNH 4 requires 382.2741; IR ν max (film)/cm⎯¹<br />

2950 (C-H), 2862 (m, C-H), 1461 (C-Me), 1062 (m); ¹H-NMR (CDCl 3 , 500 MHz) δ<br />

7.39-7.31 (m, 8H, Ph), 7.30-7.25 (m, 2H, Ph), 5.79 (dd, 1H, J 10.0, 1.5, H6), 5.59 (dd,<br />

1H, J 10.0, 2.5, H5), 4.63 (d, 1H, J 12.0, OBn), 4.59 (d, 1H, J 12.0, OBn), 4.49 (d, 1H,<br />

J 12.0, OBn'), 4.45 (d, 1H, J 12.0, OBn'), 4.07 (ddt, 1H, J 10.0, 6.0, 2.0, H4), 3.42 (d,<br />

1H, J 9.0, H7), 3.36 (d, 1H, J 9.0, H7'), 2.08 (p, 1H, J 7.0, CHMe 2 ), 1.93-1.87 (m, 1H,<br />

H3), 1.66-1.57 (m, 1H, H3'), 1.31 (d, 1H, J 13.5, H2), 1.06 (s, 3H, Me), 0.95 (d, 3H, J<br />

7.0, i-Pr), 0.82 (d, 3H, J 7.0, i-Pr); ¹³C-NMR (CDCl 3 , 75.5 MHz) δ 139.0, 138.7,<br />

138.2, 138.0 (ipso-Ph, C5, C6), 128.4, 128.3, 128.2, 128.0, 127.8, 127.6, 127.4, 127.2<br />

(Ph), 76.0, 75.2, 73.3, 72.1, 69.6, 47.4, 40.5, 26.0, 25.4, 24.7, 24.5, 18.2.<br />

263


Experimental for chapter 4.2<br />

(1S*,2S*,3S*,4S*,6S*)-6-(benzyloxy)-3-((benzyloxy)methyl)-4-isopropyl-3-<br />

methylcyclohexane-1,2-diol (314)<br />

BnO<br />

BnO<br />

7<br />

OsO 4 , NMO<br />

HO<br />

6<br />

1<br />

2<br />

OBn (±)<br />

CH 2 Cl 2<br />

HO<br />

5<br />

4<br />

3<br />

OBn (±)<br />

General procedure 5 was employed using olefin 313 (26 mg, 0.07 mmol), OsO 4 (22 µl,<br />

2.5 mol%), NMO (9 mg, 0.19 mmol), in CH 2 Cl 2 (1 cm 3 ). Upon complete reaction of<br />

starting material (c. 14 d), sodium metabisulfite (0.2 cm 3 , 5% w/w aq. solution) was<br />

added. Purification by flash chroma<strong>to</strong>graphy (9:1 <strong>to</strong> 4:1 petrol:EtOAc) yielded diol<br />

314 (17 mg, 60%, 5:1 mixture of diastereomers) and starting material (6 mg, 20%) as a<br />

colourless oil.<br />

R f : 0.25 (2:1, petrol:EtOAc); MS m/z (ES+) 421 (100%, MNa + ), 437 (53%, MK + );<br />

HRMS: found 421.2342, MNa requires 421.2349; IR ν max (film)/cm⎯¹ 3434 (br, O-H),<br />

2957 (m, C-H), 1456 (m), 1085; ¹H-NMR (CDCl 3 , 500 MHz) δ 7.29-7.17 (m, 10H,<br />

Ph), 4.63 (d, 1H, J 11.5, OBn), 4.41 (d, 1H, J 11.5, OBn), 4.36 (s, 2H, OBn), 3.92 (d,<br />

1H, J 3.0, H6), 3.79-3.75 (m, 1H, H5), 3.60 (td, 1H, J 11.0, 5.0, H4), 3.42 (d, 1H, J<br />

9.5, H7), 3.21 (d, 1H, J 9.5, H7), 2.57 (br s, 1H, OH), 2.30 (br s, 1H, OH), 1.87-1.76<br />

(m, 2H, H3 eq & CHMe 2 ), 1.58 (dd, 1H, J 13.5, 3.0, H2), 1.37-1.28 (m, 1H, H3 ax ), 1.05<br />

(s, 3H, Me), 0.86 (d, 3H, J 7.0, i-Pr), 0.68 (d, 3H, J 7.0, i-Pr); ¹³C-NMR (CDCl 3 , 125<br />

MHz) δ 138.6 (ipso-Ph), 138.3 (ipso-Ph), 128.5, 128.3, 127.8 (Ph), 127.7 (para-Ph),<br />

127.3 (para-Ph), 79.1 (C4), 75.7 (C6), 73.8 (C7, OBn), 73.4 (C7, OBn), 73.0 (C7,<br />

OBn), 71.1 (C5), 43.0, 42.8 (C2, C1), 25.5 (CHMe 2 ), 25.2 (C3), 24.8, 21.4, 18.9 (Me).<br />

264


Experimental for chapter 4.2<br />

Synthesis of (1S*,2R*,3S*,4S*,5S*)-4-(hydroxymethyl)-5-isopropyl-4-<br />

methylcyclohexane-1,2,3-triol (315)<br />

BnO<br />

HO<br />

HO<br />

H 2 , Pd/C<br />

HO<br />

6<br />

1<br />

2<br />

HO<br />

OBn (±)<br />

HO<br />

5<br />

4<br />

OH<br />

3<br />

(±)<br />

A solution of oxazoline 314 (12 mg, 0.03 mmol) in methanol (1.5 cm 3 ) was passed<br />

thorough the H-cube (1 cm 3 /min, 10 bar, Pd/C) and the eluent collected for 15 min.<br />

<strong>The</strong> solvent was removed by rotary evaporation <strong>to</strong> give amide 315 (6 mg, 93%) as a<br />

colourless oil.<br />

R f : 0.11 (EtOAc); MS m/z (ES+) 241 (100%, MNa + ), 459 (30%, 2MNa + ); HRMS:<br />

found 241.1400, MNa requites 241.1410; IR ν max (film)/cm⎯¹ 3375 (br, O-H), 2958<br />

(CH), 1030; ¹H-NMR (CD 3 OD, 500 MHz) δ 3.87 (d, 1H, J 3.0, H6), 3.70 (d, 1H, J<br />

11.0, H7), 3.74-3.69 (m, 1H, H4), 3.58-3.53 (m, 1H, H5), 3.49 (d, 1H, J 11.0, H7'),<br />

1.93 (p, 1H, J 7.0, CHMe 2 ), 1.70-1.63 (m, 2H, H3), 1.36-1.28 (m, 1H, H2), 1.09 (s,<br />

3H, Me), 0.95 (d, 3H, J 7.0, i-Pr), 0.80 (d, 3H, J 7.0, i-Pr); ¹³C-NMR (CD 3 OD, 75.5<br />

MHz) δ 76.5, 75.0, 72.0, 65.6, 45.6, 44.0, 30.2, 26.3, 25.4, 21.7, 19.6.<br />

Synthesis of (1R,2R,5S,6S)-6-isopropyl-5-methyl-5-(N-methyl-(4R,5R)-4,5-<br />

diphenyloxazolidin-2-yl)cyclohex-3-ene-1,2-diol (310)<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

Ph<br />

O<br />

N<br />

O<br />

NMe<br />

O<br />

NMe<br />

MeOTf, then NaBH 4 1<br />

6<br />

2<br />

6<br />

1<br />

2<br />

OH<br />

5<br />

4<br />

3<br />

OH<br />

5<br />

4<br />

3<br />

OH<br />

O<br />

OH<br />

OH<br />

310<br />

316<br />

General procedure 3 was employed using oxazoline 276 (300 mg, 0.77 mmol) and<br />

methyl triflate (150 µl, 1.54 mmol) for 7 hr. <strong>The</strong> resulting yellow oil was purified by<br />

flash chroma<strong>to</strong>graphy (4:1 <strong>to</strong> 2:1 petrol:EtOAc) <strong>to</strong> give oxazolidine 310 (245 mg,<br />

78%) and oxazolidine 316 (4 mg, 1%) as colourless oils.<br />

265


Experimental for chapter 4.2<br />

310 R f : 0.30 (40%, EtOAc in petrol); [α] 24 D : +135 (c = 1.0, CHCl 3 ); MS m/z (ES + ) 430<br />

(100%, MNa + ), 408 (27%, MH + ), 838 (39%, [2M]Na + ); HRMS: found 430.2349, MNa<br />

requires 430.2353; IR ν max (film)/cm⎯¹ 3364 (br, O-H), 2947 (m), 2360 (w, C=C), 1453<br />

(m); ¹H-NMR (CDCl 3 , 500 MHz) δ 7.31-7.25 (m, 3H, Ar), 7.23-7.16 (m, 5H, Ar),<br />

7.05-7.00 (m, 2H, Ar), 6.06 (dd, 1H, J 10.0, 2.0, H5), 5.65 (dd, 1H, J 10.0, 2.0, H6),<br />

4.74 (d, 1H, J 9.0, CHOPh), 4.54 (s, 1H, CHON), 4.24 (dd, 1H, J 11.5, 7.0, H3), 3.95<br />

(br d, 1H, J 7.0, H4), 3.30 (d, 1H, J 9.0, CHNPh), 2.37 (s, 3H, NMe), 2.31-2.10 (m,<br />

3H, CHMe 2 , OH), 1.48 (d, 1H, J 11.5, H2), 1.29 (d, 3H, J 7.0, CHMe A Me b ), 1.21-1.17<br />

(m, 6H, Me & CHMe a Me B ); ¹³C-NMR (CDCl 3 , 75.5 MHz) δ 138.6 (ipso-Ph), 137.6<br />

(ipso-Ph), 134.7 (C5), 128.3 (C6), 128.1, 128.0, 127.8, 127.7, 126.4 (Ph), 99.9<br />

(CHON), 85.6 (CHOPh), 79.6 (CHNPh), 76.1 (C4), 74.1 (C3), 55.1 (C2), 48.6 (C1),<br />

41.9 (NMe), 27.3 (CHMe a Me B ), 25.9 (CHMe 2 ), 24.7 (Me), 17.9 (CHMe A Me b ).<br />

316 R f : 0.32 (2:1, petrol:EtOAc); [α] 24 D : +217 (c = 1.0, CHCl 3 ); MS m/z (ES + ) 430<br />

(100%, MNa + ); HRMS: found 430.2348, MNa requires 430.2353; IR ν max (film)/cm⎯¹<br />

3368 (br, O-H), 2957 (m, C-H), 1604 (m, C=C), 1453 (C-Me); ¹H-NMR (CDCl 3 , 500<br />

MHz) δ 7.33-7.28 (m, 3H, Ph), 7.26-7.22 (m, 3H, Ph), 7.22-6.98 (m, 2H, Ph), 7.05-<br />

7.01 (m, 2H, Ph), 6.29 (d, 1H, J 10.0, H6), 6.00 (dd, 1H, J 10.0, 5.0, H5), 4.67 (d, 1H,<br />

J 9.5, CHOPh), 4.61 (s, 1H, CHON), 4.52 (dd, 1H, J 12.0, 5.0, H3), 3.99 (t, 1H, J 5.0,<br />

H4), 3.31 (d, 1H, J 9.5, CHNPh), 2.39 (s, 3H, NMe), 2.21 (p, 1H, J 7.0, CHMe 2 ), 2.08<br />

(br s, 1H, OH), 1.86 (br s, 1H, OH), 1.52 (d, 1H, J 12.0, H2), 1.35 (d, 3H, J 7.0, i-Pr),<br />

1.23-1.20 (m, 6H, Me & i-Pr); ¹³C-NMR (CDCl 3 , 125 MHz) δ 138.7 (ipso-Ph), 138.5<br />

(ipso-Ph), 137.6 (C5), 128.3 (C6), 128.1, 128.0, 127.8, 127.7, 126.5, 126.2 (Ph), 100.0<br />

(CHON), 85.7 (CHOPh), 79.5 (CHNPh), 69.1, 66.7 (C3, C4), 50.4 (C2), 48.8 (C1),<br />

41.8 (NMe), 27.6 (i-Pr), 25.8 (i-Pr), 24.7 (Me), 17.7 (i-Pr).<br />

266


Experimental for chapter 4.2<br />

Synthesis of (1R,2S,3S,4S,5R,6S)-6-isopropyl-5-methyl-5-(N-methyl-(4R,5R)-4,5-<br />

diphenyloxazolidin-2-yl)cyclohexane-1,2,3,4-tetraol (311)<br />

Ph Ph<br />

Ph Ph Ph Ph Ph Ph<br />

O<br />

N<br />

O<br />

NMe<br />

O<br />

NMe<br />

O<br />

NMe<br />

1<br />

OsO 4<br />

HO 6<br />

HO<br />

2<br />

OH<br />

CH 2 Cl 2 , NMO<br />

5<br />

HO<br />

3<br />

4 OH<br />

OH HO OH<br />

OH<br />

OH<br />

O<br />

O<br />

311 318 319<br />

General procedure 5 was employed using olefin 310 (20 mg, 0.05 mmol), OsO 4 (12 µl,<br />

2.0 mol%), NMO (12 mg, 0.10 mmol), in CH 2 Cl 2 (0.5 cm 3 ). Upon complete reaction<br />

of starting material (7 days), sodium metabisulfite (0.2 cm 3 , 5% w/w aq. solution) was<br />

added. Purification by flash chroma<strong>to</strong>graphy (19:1 <strong>to</strong> 1:2 petrol:EtOAc) yielded<br />

tetraol 311 (4 mg, 21%), enone 318 (2 mg, 11%) and triol 319 (8 mg, 42%) as<br />

colourless oils.<br />

311 R f : 0.23 (2:1, petrol:EtOAc); [α] 20 D : +14 (c = 1, CHCl 3 ); MS m/z (ES–) 442<br />

(100%, MH + ), 443 (31%, (M+1)H + ); HRMS: found 442.2584, MH requires 442.2588;<br />

IR ν max (film)/cm⎯¹ 3398 (br, O-H), 2927 (m, C-H), 2360 (w), 1457 (w), 1065; ¹H-<br />

NMR (CDCl 3 , 500 MHz) δ 7.33-7.27 (m, 6H, Ph), 7.22-7.16 (m, 2H, Ph), 7.08-6.99<br />

(m, 2H, Ph), 4.63 (d, 1H, J 9.0, CHOPh), 4.59 (d, 1H, J 3.0, H6), 4.51 (s, 1H, CHNO),<br />

4.15 (dd, 1H, J 11.0, 9.0, H3), 3.95-3.90 (m, 1H, H5), 3.71 (t, 1H, J 9.0, H4), 3.35 (d,<br />

1H, J 9.0, CHNPh), 2.29 (s, 3H, NMe), 2.13 (p, 1H, J 7.0, CHMe 2 ), 1.74 (d, 1H, J<br />

11.0, H2), 1.29 (d, 3H, J 7.0, CHMe A Me b ), 1.28 (s, Me), 1.20 (d, 3H, J 7.0,<br />

CHMe a Me B ); ¹³C-NMR (CDCl 3 , 75.5 MHz) δ 139.2 (ipso-Ph), 137.1 (ipso-Ph),<br />

128.544, 128.3, 128.0, 127.7, 126.3 (Ph), 101.2 (CHNO), 85.2 (CHOPh), 79.7<br />

(CHNPh), 76.8 (CHOH), 73.6 (CHOH), 73.5 (CHOH), 72.6 (CHOH), 52.2 (C2), 47.2<br />

(C1), 39.7 (NMe), 27.7 (CHMe a Me B ), 25.3 (CHMe 2 ), 23.144 (Me), 18.2 (CHMe A Me b ).<br />

318 R f : 0.20 (9:1, petrol:EtOAc); [α] 24 D : +268 (c = 1, CHCl3); MS m/z (ES+) 428<br />

(100%, MNa + ), 429 (32%, (M+1)H + ); HRMS: found 428.2191, MNa requires<br />

428.2196; IR ν max (film)/cm⎯¹ 3383 (m, O-H), 2947 (m, C-H), 2355 (m), 1675 (C=O),<br />

1450 (w, C-Me), 1061 (m); ¹H-NMR (CDCl 3 , 500 MHz) δ 7.34-7.29 (m, 4H, Ph, H6),<br />

7.27-7.23 (m, 3H, Ph), 7.18-7.15 (m, 2H, Ph), 7.03-6.99 (m, 2H, Ph), 6.22 (d, 1H, J<br />

267


Experimental for chapter 4.2<br />

10.0, H5), 4.86 (dd, 1H, J 13.0, 1.0, H3), 4.82 (s, 1H, CHON), 4.62 (d, 1H, J 9.5,<br />

CHOPh), 3.42 (br d, 1H, J 1.0, OH), 3.38 (d, 1H, J 9.5, CHNPh), 2.45 (s, 3H, NMe),<br />

2.26 (p, 1H, J 7.0, CHMe 2 ), 1.85 (d, 1H, J 13.0, H2); 1.39 (s, 3H, Me), 1.37 (d, 3H, J<br />

7.0, CHMe A Me b ), 1.21 (d, 3H, J 7.0, CHMe a Me B ); ¹³C-NMR (CDCl 3 , 75.5 MHz) δ<br />

202.9 (C=O), 157.6 (C6), 137.8 (ipso-Ph), 136.9 (ipso-Ph), 128.5, 128.1, 128.1, 128.0,<br />

128.0, 126.4, 126.3 (Ph), 100.6 (CHNO), 86.6 (CHOPh), 79.6 (CHNPh), 72.2 (C3),<br />

56.6 (C2), 49.4 (C1), 41.7 (NMe), 26.6 (CHMe a Me B ), 26.5 (CHMe 2 ), 24.2 (Me), 17.5<br />

(CHMe A Me b ).<br />

319 R f : 0.33 (0.4, EtOAc in petrol); [α] 22 D : +43 (c = 1.3, CHCl 3 ); MS m/z (ES+) 440<br />

(100%, MH + ), 441 (29%, (M+1)H + ); HRMS: found 440.2434, MH requires 440.2431;<br />

IR ν max (film)/cm⎯¹ 3474 (O-H), 2950 (m, C-H), 1717 (C=O), 1453 (m); ¹H-NMR<br />

(CDCl 3 , 500 MHz) δ 7.37-7.25 (m, 6H, Ph), 7.23-7.18 (m, 2H, Ph), 7.10-7.04 (m, 2H,<br />

Ph), 4.98 (br d, 1H, J 11.0, H3), 4.87 (d, 1H, J 3.0, H5 or H6), 4.80 (d, 1H, J 3.0, H5 or<br />

H6), 4.69-4.64 (m, 2H, CHNO, CHOPh), 3.81 (br s, 1H, OH), 3.45 (d, 1H, J 9.0,<br />

CHNPh), 3.23. (br d, 1H, J 3.0, C3-OH), 2.65 (br s, 1H, OH), 2.35 (s, 3H, NMe), 2.24<br />

(p, 1H, J 7.0, CHMe 2 ), 2.01 (d, 1H, J 11.5, H2), 1.38 (s, 3H, Me), 1.35 (d, 3H, J 7.0, i-<br />

Pr), 1.18 (d, 3H, J 7.0, i-Pr); ¹³C-NMR (CDCl 3 , 125 MHz) δ 138.6, 136.6, 128.7,<br />

128.3, 128.2, 128.1, 126.4, 101.2, 86.2, 79.7, 74.7, 74.2, 57.0, 46.0, 39.4, 27.2, 25.9,<br />

22.8, 18.1.<br />

268


Experimental for chapter 4.2<br />

Synthesis of (1R,2R,5S,6S)-5-(hydroxymethyl)-6-isopropyl-5-methylcyclohex-3-<br />

ene-1,2-diol (312)<br />

Ph<br />

Ph<br />

O<br />

NMe<br />

i) H 3 O + , 50 °C<br />

HO<br />

6<br />

1<br />

2<br />

OH<br />

OH<br />

ii) NaBH 4<br />

5<br />

4<br />

OH<br />

3<br />

OH<br />

General procedure 7 was employed using oxazolidine 310 (50 mg, 0.12 mmol), and the<br />

reaction heated at 50 °C for 24 hr. Flash chroma<strong>to</strong>graphy (3:2 petrol:EtOAc) yielded<br />

triol 312 (19 mg, 79%) as colourless needles.<br />

R f : 0.34 (EtOAc); Mpt: 136-138 ºC (MeOH); [α] 22 D : +10.8 (c = 1.7, MeOH); MS m/z<br />

(ES+) 223 (100%, MNa + ), 224 (15%, (M+1)Na + ); HRMS: found 223.1299, MNa<br />

requires 223.1305; IR ν max (film)/cm⎯¹ 3348 (br, O-H), 2958 (m, C-H), 1651 (w, C=C);<br />

¹H-NMR (CD 3 OD, 500 MHz) δ 5.60 (dd, 1H, J 10.0, 1.5, H5), 5.44 (dd, 1H, J 10.0,<br />

2.0, H6), 4.00 (d, 1H, J 7.5, H4), 3.91 (dd, 1H, J 12.0, 7.5, H3), 3.59 (d, 1H, J 11.0,<br />

H7), 3.39 (d, 1H, J 11.0, H7’), 2.03 (p, 1H, J 7.0, CHMe 2 ), 1.48 (d, 1H, J 12.0, H2),<br />

1.19 (d, 6H, J 7.0, i-Pr), 1.01 (s, 3H, Me); ¹³C-NMR (CD 3 OD, 75.5 MHz) δ 136.8<br />

(C5), 129.3 (C6), 76.3 (C4), 74.1 (C3), 67.7 (C7), 53.7 (C2), 44.9 (C1), 27.5 (CHMe 2 ),<br />

27.5 (CHMe A Me B ), 24.7 (Me), 18.1 (CHMe A Me B ).<br />

For dihydroxylation of 312 <strong>to</strong> give altrose analogue 278, see page 260<br />

Synthesis of (1S,4R,5R,6S)-5-hydroxy-6-isopropyl-1-methylcyclohex-2-ene-δlac<strong>to</strong>ne<br />

(328)<br />

Ph<br />

Ph<br />

O<br />

N<br />

Me<br />

MeOTf, then NH 4 Cl<br />

O<br />

1<br />

2<br />

OH<br />

O<br />

4<br />

3<br />

OH<br />

OH<br />

General procedure 6 was used employing oxazoline 213 (45 mg, 0.11 mmol) and<br />

methyl triflate (27 µl, 0.23 mmol) for 16 hr and an ammonium chloride (sat. aq., 0.5<br />

269


Experimental for chapter 4.2<br />

cm 3 ) quench. <strong>The</strong> layers were partitioned, the aqueous layer washed with CH 2 Cl 2 (2 x<br />

5 cm 3 ) and the combined organic phases dried over anhydrous sodium sulfate. Flash<br />

chroma<strong>to</strong>graphy (9:1 <strong>to</strong> 1:1 petrol:EtOAc) gave lac<strong>to</strong>ne 328 (8 mg, 36%) as a<br />

colourless oil.<br />

R f : 0.09 (4:1, petrol:EtOAc); [α] 24 D : +187 (c = 0.8, CHCl 3 ); MS m/z (ES-) 391 (100%,<br />

[2M-H] – ), 195 (40%, [M-H] – ), 196 (4%, [(M+1)-H] – ); IR ν max (film)/cm⎯¹ 3432 (br,<br />

OH), 2964 (m, C-H), 1758 (C=O); ¹H-NMR (CDCl 3 , 500 MHz) δ 5.93 (d, 1H, J 9.0,<br />

H6), 5.79-5.74 (dm, 1H, J 9.0, H5), 4.54-4.50 (m, 1H, H4), 4.37-4.32 (m, 1H, H3),<br />

2.16 (d, 1H, J 3.5, H2), 2.01 (pd, 1H, J 7.0, 3.5, CHMe 2 ), 1.91 (br d, 1H, J 6.0, H3),<br />

1.32 (s, 3H, Me), 1.04 (d, 3H, J 7.0, i-Pr), 0.87 (d, 3H, J 7.0, i-Pr); ¹³C-NMR (CDCl 3 ,<br />

125 MHz) δ 179.0 (C=O), 139.2, 128.2, 66.8, 50.8, 25.5, 21.5, 17.6, 14.9.<br />

(1S,2S,3R,4R,5R,6S)-2,3-epoxy-5-hydroxy-6-isopropyl-1-methylcyclohexane-δlac<strong>to</strong>ne<br />

(329)<br />

O<br />

O<br />

Me<br />

OH<br />

mCPBA<br />

O<br />

Me<br />

1<br />

2<br />

O<br />

O<br />

4<br />

3<br />

OH<br />

mCPBA (17 mg, 50%, 0.05 mmol) was added in a single portion <strong>to</strong> a stirred solution<br />

of allyl alcohol 328 (5 mg, 0.05 mmol) at –20 °C in CH 2 Cl 2 (0.3 cm 3 ) and maintained<br />

at the temperature for 4 hr, after which period the reaction was allowed <strong>to</strong> warm <strong>to</strong> rt.<br />

After 18 hr, aqueous sodium bicarbonate (1 cm 3 sat.) was added, the reaction<br />

partitioned, and the aqueous phase extracted with further CH 2 Cl 2 (2 x 5 cm 3 ). <strong>The</strong><br />

combined organic layers were dried over anhydrous sodium sulfate, and the solvent<br />

removed. <strong>The</strong> resulting mixture was purified by flash column chroma<strong>to</strong>graphy (4:1<br />

petrol:EtOAc) <strong>to</strong> give epoxide 329 (4 mg, 80%) as a colourless oil.<br />

R f : 0.29 (2:1, petrol:EtOAc); [α] 24 D : +78 (c = 0.5, CHCl 3 ); MS m/z (ES–) 211 (100%,<br />

(M-H) – ), 212 (9%, ([M+1]-H) – ), 423 (90%, (2M-H) – ); HRMS: found 212.1044, M<br />

requires 212.1043; IR ν max (film)/cm⎯¹ 3431 (br, O-H), 2964 (m, C-H), 1779 (C=O),<br />

1261 (m); ¹H-NMR (CDCl 3 , 500 MHz) δ 4.33-4.29 (m, 1H, H3 or H4), 4.10-4.04 (m,<br />

1H, H3 or H4), 3.37-3.32 (m, 2H, H5, H6), 2.32 (d, 1H, J 3.5, H2), 2.19 (br s, 1H,<br />

OH), 1.89 (pd, 1H, J 7.0, 3.5, CHMe 2 ), 1.41 (s, 3H, Me), 0.99 (d, 3H, J 7.0, i-Pr), 0.83<br />

270


Experimental for chapter 4.2<br />

(d, 3H, J 7.0, i-Pr); ¹³C-NMR (CDCl 3 , 125 MHz) δ 177.6, 64.9, 60.1, 51.1, 44.6, 43.3,<br />

24.9, 21.4, 17.5, 14.0<br />

Synthesis of (1S,2R,3S,4R,5R,6S)-5-(N-methyl-N-oxo-(4R,5R)-4,5-<br />

diphenyloxazolidin-2-yl)-3,4-epoxy-6-isopropyl-5-methylcyclohexane-1,2-diol<br />

(332)<br />

Ph Ph<br />

Ph Ph<br />

O N<br />

mCPBA, CH 2 Cl 2<br />

O<br />

OH<br />

OH<br />

O<br />

O N<br />

1<br />

6 2<br />

3<br />

5<br />

4<br />

mCPBA (37 mg, 50%, 0.11 mmol) was added in a single portion <strong>to</strong> a stirred solution<br />

of allyl alcohol 310 (22 mg, 0.05 mmol) at –40 °C in CH 2 Cl 2 (0.5 cm 3 ) and maintained<br />

at the temperature for 4 hr, after which period the reaction was allowed <strong>to</strong> warm <strong>to</strong> rt.<br />

After 18 hr, aqueous sodium sulfite (1 cm 3 sat.) was added, the reaction mixture was<br />

washed with aqueous sodium bicarbonate (1 cm 3 sat.) and the aqueous phase extracted<br />

with further CH 2 Cl 2 (3 x 5 cm 3 ). <strong>The</strong> combined organic layers were dried over<br />

anhydrous sodium sulfate, and the solvent removed. <strong>The</strong> resulting mixture was<br />

purified by flash column chroma<strong>to</strong>graphy (9:1 petrol:EtOAc <strong>to</strong> 10% MeOH in EtOAc)<br />

<strong>to</strong> give epoxide 332 (12 mg, 53%) as a white wax.<br />

OH<br />

OH<br />

R f : 0.28 (9:1, EtOAc:MeOH); [α] 24 D : +125 (c = 1, CHCl 3 ); MS m/z (ES+) 440 (58%,<br />

MH + ), 462 (100%, MNa + ); 901 (36%, M 2 Na + ); HRMS: found 440.2428, MH requires<br />

440.2431; IR ν max (film)/cm⎯¹ 3435 (br, OH), 1187, 1121, 1040 (C-O-C), 1010 (m, N-<br />

O); ¹H-NMR (CD 3 OD, 500 MHz) δ 7.66-7.62 (m, 2H, Ph), 7.44-7.35 (m, 3H, Ph),<br />

7.34-7.28 (m, 2H, Ph), 7.23-7.19 (m, 3H, Ph), 6.04 (d, 1H, J 11.0, CHOPh), 5.50 (s,<br />

1H, CHNO), 4.67 (d, 1H, J 11.0, CHNPh), 4.07 (dd, 1H, J 11.5, 7.5, H3), 3.86 (d, 1H,<br />

J 3.5, H6), 3.61 (dd, 1H, J 7.5, 1.5, H4), 3.23-3.19 (m, 4H, NMe, H5), 2.10 (p, 1H, J<br />

7.0, CHMe 2 ), 1.57 (s, 3H, Me), 1.33 (d, 3H, J 7.0, i-Pr), 1.29 (d, 1H, J 11.5, H2), 1.21<br />

(d, 3H, J 7.0, i-Pr); ¹³C-NMR (CDCl 3 , 75.5 MHz) δ 136.6, 132.8, 130.1, 128.4, 128.3,<br />

128.0, 127.1, 126.4 (Ph), 108.1 (CHNO), 87.8 (CHOPh), 81.5 (CHNPh), 77.3 (C4),<br />

71.2 (C3), 61.4 (C6), 57.6 (C2), 54.8 (C5), 42.9 (NMe), 42.8 (C1), 27.5 (i-Pr), 27.2<br />

(CHMe 2 ), 22.7 (Me), 17.4 (i-Pr).<br />

271


Experimental for chapter 4.2<br />

Synthesis of (1R,2S,3R,4S,5S,6S)-5-(hydroxymethyl)-6-isopropyl-5-<br />

methylcyclohexane-1,2,3,4-tetraol (324)<br />

HO<br />

HCl (aq), THF<br />

O<br />

OH<br />

0 °C - rt<br />

OH<br />

HO<br />

HO<br />

HO<br />

1<br />

6<br />

5<br />

4<br />

Aqueous hydrochloric acid (0.3 cm 3 , 6M) was added <strong>to</strong> a solution of epoxide 309 in<br />

THF (0.3 cm 3 ) an ice bath at 0 °C which was allowed <strong>to</strong> warm <strong>to</strong> ambient temperature.<br />

Solvent was removed from the reaction after 8 hr, and the resulting oil was purified by<br />

flash chroma<strong>to</strong>graphy (2:1 <strong>to</strong> 2:3 petrol:EtOAc) <strong>to</strong> yield pentaol 324 (13 mg 81%) as<br />

colourless needles.<br />

OH<br />

2<br />

3<br />

OH<br />

R f : 0.30 (EtOAc); Mpt: 204-5 ºC (MeOH); [α] 23 D : –10.4 (c = 0.5, CHCl 3 ); MS m/z<br />

(ES+) 275 (100%, [M+H 2 O]Na + ); HRMS: found 275.1445, [M+H 2 O]Na + requires<br />

275.1465; IR ν max (film)/cm⎯¹ 3325 (br, O-H), 3161 (br, O-H), 2967 (m, C-H), 2913<br />

(m, C-H), 1471 (w, C-Me), 1100, 1058; ¹H-NMR (CD 3 OD, 500 MHz) δ 4.36 (d, 1H, J<br />

3.0, H6), 4.13 (t, 1H, J 3.0, H5), 4.08 (d, 1H, J 11.0, H7 a ), 3.90-3.86 (m, 2H, H3 or<br />

H4), 3.48 (d, 1H, J 11.0, H7 b ), 1.94 (p, 1H, J 7.0, CHMe 2 ), 1.69-1.63 (m, 1H, H2),<br />

1.16-1.12 (m, 6H, Me, i-Pr), 1.10 (d, 3H, J 7.0, i-Pr); ¹³C-NMR (CD 3 OD, 75.5 MHz) δ<br />

75.5 (CHOH), 73.7 (CHOH), 70.8 (CHOH), 69.1 (CHOH), 67.1 (C7), 50.4 (C2), 46.2<br />

(C1), 27.6, 27.0, 25.7, 18.6 (Me).<br />

272


Experimental for chapter 4.2<br />

Data for (1R,2S,3S,4R,5S,6S)-5-(hydroxymethyl)-6-isopropyl-5-<br />

methylcyclohexane-1,2,3,4-tetraol (322)<br />

HO<br />

7<br />

HO<br />

6<br />

1<br />

2<br />

HO<br />

5<br />

3<br />

4 OH<br />

OH<br />

R f : 0.47 (EtOAc); [α] 22 D : –104 (c = 0.1, CHCl 3 ); MS m/z (ES+) 275 (100%,<br />

[M+H 2 O]Na + ); IR ν max (film)/cm⎯¹ 3357 (br, O-H), 2909, 1993, 1458; ¹H-NMR<br />

(CDCl 3 , 500 MHz) δ 4.34 (t, 1H, J 10.5, H5), 3.92 (dd, 1H, J 11.5, 9.0, H3), 3.72 (d,<br />

2H, J 3.5, H7), 3.50-3.43 (m, 2H, H4, H6), 2.81 (d, 1H, J 3.0, OH), 2.64 (br s, 1H,<br />

OH), 2.43 (br s, 1H, OH), 2.29 (t, 1H, J 3.5, C7-OH), 2.02 (p, 1H, J 7.0, CHMe 2 ), 1.19<br />

(s, 3H, Me), 1.15 (d, 3H, J 7.0, i-Pr), 1.11 (d, 3H, J 7.0, i-Pr).<br />

273


Experimental for chapter 4.2<br />

5.7 References for Experimental Section<br />

(1) Gomez, J. C. C.; Lopez, F. J. S.; 4.8.6 ed.; MestRe-C, Ed. 2005.<br />

(2) Gomes, M.; 1.0 ed.; Paulo, U. d. S., Ed.; Universidade de Sao Paulo: 2004.<br />

(3) Crosignani, S.; Young, A. C.; Linclau, B. Tetrahedron Lett. 2004, 45, 9611-<br />

9615.<br />

(4) Meyers, A. I.; Roth, G. P.; Hoyer, D.; Barner, B. A.; Laucher, D. J. Am. Chem.<br />

Soc. 1988, 110, 4611-24.<br />

(5) VanRheenen, V.; Cha, D. Y.; Hartley, W. M. Org. Synth. 1978, 58, 43.<br />

(6) Hodgson, R.; Majid, T.; Nelson, A. J. Chem. Soc., Perkin Trans. 1 2002, 1444 -<br />

1454.<br />

(7) Barner, B. A.; Meyers, A. I. J. Am. Chem. Soc. 1984, 106, 1865-6.<br />

(8) Kolb, H.; VanNieuwenhze, M.; Sharpless, K. B. Chem. Rev. 1994, 2483.<br />

(9) Wang, Z. M.; Sharpless, K. B. J. Org. Chem. 1994, 8302.<br />

(10) Chang, H.-T.; Sharpless, K. B. Tetrahedron Lett. 1996, 37, 3219.<br />

(11) Cabedo, N. C.; University of Manchester: 2004-5.<br />

(12) Ittah, Y.; Sasson, Y.; Shahak, I.; Tsaroom, S.; Blum, J. J. Org. Chem. 1978, 43,<br />

4271-4273.<br />

(13) Heine, H. W.; King, D. C.; Portland, L. A. J. Org. Chem. 1966, 31, 4271-4272.<br />

(14) Reyes, A.; Juaristi, E. Chirality 1998, 10, 95-99.<br />

(15) Lygo, B., Suggestion <strong>to</strong> use diethyl ether-petrol solvent at low temperature <strong>to</strong><br />

encourage precipitation of Et 3 .HCl salt, reducing free chloride ions which<br />

would otherwise attack the aziridine ring.<br />

(16) Groundwater, P. W.; Garnett, I.; Mor<strong>to</strong>n, A. J.; Sharif, T.; Coles, S. J.;<br />

Hursthouse, M. B.; Nyerges, M.; Anderson, R. J.; Bendell, D.; McKillop, A.;<br />

Zhang, W. J. Chem. Soc., Perkin Trans. 1 2001, 2781-2787.<br />

(17) Hayashida, M.; Ishizaki, M.; Hara, H. Chem. Pharm. Bull. 2006, 54, 1299.<br />

(18) Haak, E.; Siebeneicher, H.; Doye, S. Org. Lett. 2000, 2, 1935-1937.<br />

(19) Czernecki, S.; Georgoulis, C.; Provelenghiou, C. Tetrahedron Lett. 1976, 17,<br />

3535.<br />

(20) Eames, J.; Mitchell, H. J.; Nelson, A.; O'Brien, P.; Warren, S.; Wyatt, P. J.<br />

Chem. Soc., Perkin Trans. 1 1999, 1095-1103.<br />

(21) Curtin, D. Y.; Kellom, D. B. J. Am. Chem. Soc. 1953, 75, 6011-6018<br />

274


Appendix A: Selected NMR Spectra<br />

275


276


277


278


279


280


281


282


283


284


Appendix B – Crystallographic Information Files (cif)<br />

a. Compound 102b<br />

Ph<br />

O<br />

N<br />

Ph<br />

Me<br />

OMe<br />

102b<br />

Identification code s2170m<br />

Empirical formula C26 H29 N O2<br />

Formula weight 387.50<br />

Temperature<br />

100(2) K<br />

Wavelength<br />

0.71073 A<br />

Crystal system, space group Orthorhombic, P2(1)2(1)2(1)<br />

Unit cell dimensions a = 12.1398(11) A alpha = 90 deg.<br />

b = 12.8480(11) A beta = 90 deg.<br />

c = 13.5618(12) A gamma = 90 deg.<br />

Volume<br />

2115.3(3) A^3<br />

Z, Calculated density 4, 1.217 Mg/m^3<br />

Absorption coefficient 0.076 mm^-1<br />

F(000) 832<br />

Crystal size<br />

0.40 x 0.20 x 0.15 mm<br />

<strong>The</strong>ta range for data collection 2.18 <strong>to</strong> 28.29 deg.<br />

Limiting indices -14


Absolute structure parameter 1.3(11)<br />

Largest diff. peak and hole 0.175 and -0.143 e.A^-3<br />

286


_audit_creation_method SHELXL-97<br />

_chemical_name_systematic<br />

_chemical_name_common ?<br />

_chemical_melting_point ?<br />

_chemical_formula_moiety ?<br />

_chemical_formula_sum<br />

'C26 H29 N O2'<br />

_chemical_formula_weight 387.50<br />

loop_<br />

_a<strong>to</strong>m_type_symbol<br />

_a<strong>to</strong>m_type_description<br />

_a<strong>to</strong>m_type_scat_dispersion_real<br />

_a<strong>to</strong>m_type_scat_dispersion_imag<br />

_a<strong>to</strong>m_type_scat_source<br />

'C' 'C' 0.0033 0.0016<br />

'International Tables Vol C Tables 4.2.6.8 and<br />

6.1.1.4'<br />

'H' 'H' 0.0000 0.0000<br />

'International Tables Vol C Tables 4.2.6.8 and<br />

6.1.1.4'<br />

'N' 'N' 0.0061 0.0033<br />

'International Tables Vol C Tables 4.2.6.8 and<br />

6.1.1.4'<br />

'O' 'O' 0.0106 0.0060<br />

'International Tables Vol C Tables 4.2.6.8 and<br />

6.1.1.4'<br />

_symmetry_cell_setting Orthorhombic<br />

_symmetry_space_group_name_H-M<br />

P2(1)2(1)2(1)<br />

loop_<br />

_symmetry_equiv_pos_as_xyz<br />

'x, y, z'<br />

'-x+1/2, -y, z+1/2'<br />

'-x, y+1/2, -z+1/2'<br />

'x+1/2, -y+1/2, -z'<br />

_cell_length_a 12.1398(11)<br />

_cell_length_b 12.8480(11)<br />

_cell_length_c 13.5618(12)<br />

_cell_angle_alpha 90.00<br />

_cell_angle_beta 90.00<br />

_cell_angle_gamma 90.00<br />

_cell_volume 2115.3(3)<br />

_cell_formula_units_Z 4<br />

_cell_measurement_temperature 100(2)<br />

_cell_measurement_reflns_used input<br />

_cell_measurement_theta_min 2.2475<br />

_cell_measurement_theta_max 20.9675<br />

_exptl_crystal_description prism<br />

_exptl_crystal_colour white<br />

_exptl_crystal_size_max 0.40<br />

_exptl_crystal_size_mid 0.20<br />

_exptl_crystal_size_min 0.15<br />

_exptl_crystal_density_meas 0<br />

_exptl_crystal_density_diffrn 1.217<br />

_exptl_crystal_density_method 'not measured'<br />

_exptl_crystal_F_000 832<br />

_exptl_absorpt_coefficient_mu 0.076<br />

_exptl_absorpt_correction_type none<br />

_exptl_absorpt_correction_T_min 0.9703<br />

_exptl_absorpt_correction_T_max 0.9887<br />

_exptl_absorpt_process_details ?<br />

_exptl_special_details<br />

_diffrn_ambient_temperature 100(2)<br />

_diffrn_radiation_wavelength 0.71073<br />

_diffrn_radiation_type MoK\a<br />

_diffrn_radiation_source 'fine-focus sealed<br />

tube'<br />

_diffrn_radiation_monochroma<strong>to</strong>r graphite<br />

_diffrn_measurement_device_type 'CCD area<br />

detec<strong>to</strong>r'<br />

_diffrn_measurement_method 'phi and omega<br />

scans'<br />

_diffrn_detec<strong>to</strong>r_area_resol_mean ?<br />

_diffrn_standards_number ?<br />

_diffrn_standards_interval_count ?<br />

287


_diffrn_standards_interval_time ?<br />

_diffrn_standards_decay_% ?<br />

_diffrn_reflns_number 13445<br />

_diffrn_reflns_av_R_equivalents 0.0713<br />

_diffrn_reflns_av_sigmaI/netI 0.1472<br />

_diffrn_reflns_limit_h_min -14<br />

_diffrn_reflns_limit_h_max 15<br />

_diffrn_reflns_limit_k_min -16<br />

_diffrn_reflns_limit_k_max 8<br />

_diffrn_reflns_limit_l_min -17<br />

_diffrn_reflns_limit_l_max 18<br />

_diffrn_reflns_theta_min 2.18<br />

_diffrn_reflns_theta_max 28.29<br />

_reflns_number_<strong>to</strong>tal 4966<br />

_reflns_number_gt 2771<br />

_reflns_threshold_expression >2sigma(I)<br />

_computing_data_collection<br />

'Bruker<br />

SMART'<br />

_computing_cell_refinement<br />

'Bruker<br />

SMART'<br />

_computing_data_reduction<br />

'Bruker<br />

SAINT'<br />

_computing_structure_solution 'SHELXS-97<br />

(Sheldrick, 1990)'<br />

_computing_structure_refinement 'SHELXL-97<br />

(Sheldrick, 1997)'<br />

_computing_molecular_graphics 'Bruker<br />

SHELXTL'<br />

_computing_publication_material 'Bruker<br />

SHELXTL'<br />

_refine_special_details<br />

Refinement of F^2^ against ALL reflections. <strong>The</strong><br />

weighted R-fac<strong>to</strong>r wR and<br />

goodness of fit S are based on F^2^, conventional<br />

R-fac<strong>to</strong>rs R are based<br />

on F, with F set <strong>to</strong> zero for negative F^2^. <strong>The</strong><br />

threshold expression of<br />

F^2^ > 2sigma(F^2^) is used only for calculating<br />

R-fac<strong>to</strong>rs(gt) etc. and is<br />

not relevant <strong>to</strong> the choice of reflections for<br />

refinement. R-fac<strong>to</strong>rs based<br />

on F^2^ are statistically about twice as large as<br />

those based on F, and R-<br />

fac<strong>to</strong>rs based on ALL data will be even larger.<br />

_refine_ls_structure_fac<strong>to</strong>r_coef Fsqd<br />

_refine_ls_matrix_type full<br />

_refine_ls_weighting_scheme calc<br />

_refine_ls_weighting_details<br />

'calc w=1/[\s^2^(Fo^2^)+(0.0000P)^2^+0.0000P]<br />

where P=(Fo^2^+2Fc^2^)/3'<br />

_a<strong>to</strong>m_sites_solution_primary direct<br />

_a<strong>to</strong>m_sites_solution_secondary difmap<br />

_a<strong>to</strong>m_sites_solution_hydrogens geom<br />

_refine_ls_hydrogen_treatment mixed<br />

_refine_ls_extinction_method none<br />

_refine_ls_extinction_coef ?<br />

_refine_ls_abs_structure_details<br />

'Flack H D (1983), Acta Cryst. A39, 876-881'<br />

_refine_ls_abs_structure_Flack 1.3(11)<br />

_refine_ls_number_reflns 4966<br />

_refine_ls_number_parameters 266<br />

_refine_ls_number_restraints 0<br />

_refine_ls_R_fac<strong>to</strong>r_all 0.0879<br />

_refine_ls_R_fac<strong>to</strong>r_gt 0.0407<br />

_refine_ls_wR_fac<strong>to</strong>r_ref 0.0598<br />

_refine_ls_wR_fac<strong>to</strong>r_gt 0.0518<br />

_refine_ls_goodness_of_fit_ref 0.675<br />

_refine_ls_restrained_S_all 0.675<br />

_refine_ls_shift/su_max 0.000<br />

288


_refine_ls_shift/su_mean 0.000<br />

loop_<br />

_a<strong>to</strong>m_site_label<br />

_a<strong>to</strong>m_site_type_symbol<br />

_a<strong>to</strong>m_site_fract_x<br />

_a<strong>to</strong>m_site_fract_y<br />

_a<strong>to</strong>m_site_fract_z<br />

_a<strong>to</strong>m_site_U_iso_or_equiv<br />

_a<strong>to</strong>m_site_adp_type<br />

_a<strong>to</strong>m_site_occupancy<br />

_a<strong>to</strong>m_site_symmetry_multiplicity<br />

_a<strong>to</strong>m_site_calc_flag<br />

_a<strong>to</strong>m_site_refinement_flags<br />

_a<strong>to</strong>m_site_disorder_assembly<br />

_a<strong>to</strong>m_site_disorder_group<br />

C1 C 0.83045(16) 0.49054(15) 0.14451(14)<br />

0.0204(5) Uani 1 1 d . . .<br />

C2 C 0.92740(14) 0.41706(15) 0.17390(14)<br />

0.0207(5) Uani 1 1 d . . .<br />

H2 H 0.9720 0.4561 0.2236 0.025 Uiso 1 1 calc<br />

R . .<br />

C3 C 0.88510(15) 0.32101(14) 0.22610(14)<br />

0.0220(5) Uani 1 1 d . . .<br />

H3 H 0.9308 0.2867 0.2727 0.026 Uiso 1 1 calc<br />

R . .<br />

C4 C 0.78501(16) 0.28394(15) 0.20775(14)<br />

0.0200(5) Uani 1 1 d . . .<br />

C5 C 0.71032(15) 0.33576(15) 0.13987(14)<br />

0.0233(5) Uani 1 1 d . . .<br />

H5 H 0.6448 0.3015 0.1194 0.028 Uiso 1 1 calc<br />

R . .<br />

C6 C 0.73267(15) 0.43020(16) 0.10625(14)<br />

0.0236(5) Uani 1 1 d . . .<br />

H6 H 0.6866 0.4604 0.0574 0.028 Uiso 1 1 calc<br />

R . .<br />

C7 C 0.79109(16) 0.55021(14) 0.23711(14)<br />

0.0300(6) Uani 1 1 d . . .<br />

H7A H 0.8506 0.5951 0.2611 0.045 Uiso 1 1 calc R<br />

. .<br />

H7B H 0.7708 0.5004 0.2887 0.045 Uiso 1 1 calc R<br />

. .<br />

H7C H 0.7269 0.5929 0.2202 0.045 Uiso 1 1 calc R<br />

. .<br />

C8 C 1.00781(15) 0.38867(16) 0.08889(14)<br />

0.0242(5) Uani 1 1 d . . .<br />

H8 H 1.0342 0.4554 0.0592 0.029 Uiso 1 1 calc R .<br />

.<br />

C9 C 0.95494(15) 0.32482(14) 0.00635(15)<br />

0.0298(6) Uani 1 1 d . . .<br />

H9A H 0.9297 0.2580 0.0328 0.045 Uiso 1 1 calc R<br />

. .<br />

H9B H 1.0092 0.3125 -0.0459 0.045 Uiso 1 1 calc<br />

R . .<br />

H9C H 0.8920 0.3630 -0.0208 0.045 Uiso 1 1 calc<br />

R . .<br />

C10 C 1.10924(15) 0.33115(15) 0.12915(14)<br />

0.0341(6) Uani 1 1 d . . .<br />

H10A H 1.0870 0.2626 0.1538 0.051 Uiso 1 1 calc<br />

R . .<br />

H10B H 1.1419 0.3716 0.1830 0.051 Uiso 1 1 calc<br />

R . .<br />

H10C H 1.1635 0.3225 0.0763 0.051 Uiso 1 1 calc<br />

R . .<br />

C11 C 0.80696(15) 0.13795(15) 0.31431(14)<br />

0.0286(6) Uani 1 1 d . . .<br />

H11A H 0.8747 0.1166 0.2807 0.043 Uiso 1 1 calc<br />

R . .<br />

H11B H 0.7674 0.0761 0.3374 0.043 Uiso 1 1 calc<br />

R . .<br />

H11C H 0.8255 0.1822 0.3707 0.043 Uiso 1 1 calc<br />

R . .<br />

C12 C 0.86735(15) 0.56876(16) 0.06908(15)<br />

0.0211(5) Uani 1 1 d . . .<br />

C13 C 0.89699(15) 0.66286(15) -0.06504(13)<br />

0.0215(5) Uani 1 1 d . . .<br />

289


H13 H 0.8405 0.7136 -0.0889 0.026 Uiso 1 1<br />

calc R . .<br />

C14 C 0.96120(16) 0.71333(15) 0.02178(14)<br />

0.0212(5) Uani 1 1 d . . .<br />

H14 H 1.0419 0.7126 0.0069 0.025 Uiso 1 1 calc<br />

R . .<br />

C15 C 0.97123(15) 0.63387(16) -0.15098(14)<br />

0.0198(5) Uani 1 1 d . . .<br />

C16 C 0.97990(16) 0.53350(16) -0.18628(14)<br />

0.0240(5) Uani 1 1 d . . .<br />

H16 H 0.9404 0.4786 -0.1555 0.029 Uiso 1 1<br />

calc R . .<br />

C17 C 1.04686(16) 0.51316(16) -0.26732(15)<br />

0.0291(5) Uani 1 1 d . . .<br />

H17 H 1.0531 0.4439 -0.2911 0.035 Uiso 1 1<br />

calc R . .<br />

C18 C 1.10389(15) 0.59113(17) -0.31340(15)<br />

0.0269(5) Uani 1 1 d . . .<br />

H18 H 1.1475 0.5763 -0.3699 0.032 Uiso 1 1<br />

calc R . .<br />

C19 C 1.09767(16) 0.69211(16) -0.27715(15)<br />

0.0278(5) Uani 1 1 d . . .<br />

H19 H 1.1388 0.7465 -0.3072 0.033 Uiso 1 1<br />

calc R . .<br />

C20 C 1.03127(16) 0.71245(16) -0.19718(15)<br />

0.0259(5) Uani 1 1 d . . .<br />

H20 H 1.0262 0.7816 -0.1729 0.031 Uiso 1 1<br />

calc R . .<br />

C21 C 0.92576(16) 0.82249(16) 0.04727(13)<br />

0.0210(5) Uani 1 1 d . . .<br />

C22 C 0.99991(16) 0.90429(16) 0.04092(13)<br />

0.0253(5) Uani 1 1 d . . .<br />

H22 H 1.0746 0.8911 0.0241 0.030 Uiso 1 1 calc<br />

R . .<br />

C23 C 0.96523(19) 1.00542(17) 0.05915(14)<br />

0.0325(6) Uani 1 1 d . . .<br />

H23 H 1.0161 1.0614 0.0544 0.039 Uiso 1 1 calc<br />

R . .<br />

C24 C 0.85718(19) 1.02462(16) 0.08415(14)<br />

0.0334(6) Uani 1 1 d . . .<br />

H24 H 0.8334 1.0940 0.0959 0.040 Uiso 1 1 calc R<br />

. .<br />

C25 C 0.78323(18) 0.94337(16) 0.09222(15)<br />

0.0321(6) Uani 1 1 d . . .<br />

H25 H 0.7089 0.9567 0.1103 0.039 Uiso 1 1 calc R<br />

. .<br />

C26 C 0.81767(16) 0.84271(16) 0.07395(15)<br />

0.0271(5) Uani 1 1 d . . .<br />

H26 H 0.7668 0.7869 0.0797 0.033 Uiso 1 1 calc R<br />

. .<br />

N1 N 0.83959(12) 0.57312(12) -0.02097(12)<br />

0.0220(4) Uani 1 1 d . . .<br />

O1 O 0.73859(10) 0.19485(10) 0.24714(9)<br />

0.0239(3) Uani 1 1 d . . .<br />

O2 O 0.93834(10) 0.64334(10) 0.10419(10)<br />

0.0244(4) Uani 1 1 d . . .<br />

loop_<br />

_a<strong>to</strong>m_site_aniso_label<br />

_a<strong>to</strong>m_site_aniso_U_11<br />

_a<strong>to</strong>m_site_aniso_U_22<br />

_a<strong>to</strong>m_site_aniso_U_33<br />

_a<strong>to</strong>m_site_aniso_U_23<br />

_a<strong>to</strong>m_site_aniso_U_13<br />

_a<strong>to</strong>m_site_aniso_U_12<br />

C1 0.0205(11) 0.0166(12) 0.0239(12) -0.0021(10) -<br />

0.0007(10) 0.0000(10)<br />

C2 0.0209(12) 0.0197(13) 0.0214(12) -0.0001(10) -<br />

0.0059(9) -0.0029(11)<br />

C3 0.0261(13) 0.0188(12) 0.0210(12) 0.0008(10) -<br />

0.0036(9) 0.0032(10)<br />

C4 0.0228(12) 0.0145(12) 0.0228(12) 0.0003(10)<br />

0.0009(10) 0.0007(10)<br />

C5 0.0181(11) 0.0252(14) 0.0265(13) -0.0045(11) -<br />

0.0023(10) -0.0039(11)<br />

C6 0.0210(11) 0.0244(13) 0.0254(12) -0.0003(11) -<br />

0.0048(10) 0.0029(10)<br />

290


C7 0.0311(13) 0.0244(13) 0.0347(13) -<br />

0.0026(11) 0.0077(11) -0.0019(10)<br />

C8 0.0229(12) 0.0225(13) 0.0271(13)<br />

0.0038(11) 0.0025(10) 0.0019(10)<br />

C9 0.0332(13) 0.0232(13) 0.0331(14) -<br />

0.0042(11) 0.0054(11) 0.0026(11)<br />

C10 0.0270(13) 0.0313(15) 0.0440(16)<br />

0.0037(12) 0.0014(11) 0.0056(11)<br />

C11 0.0319(13) 0.0226(13) 0.0313(13)<br />

0.0061(11) -0.0029(11) -0.0009(11)<br />

C12 0.0146(11) 0.0146(12) 0.0341(14) -<br />

0.0031(10) 0.0008(10) 0.0039(9)<br />

C13 0.0232(11) 0.0176(12) 0.0237(12) -<br />

0.0006(9) -0.0026(10) 0.0033(10)<br />

C14 0.0227(12) 0.0198(12) 0.0209(12)<br />

0.0032(10) 0.0044(10) -0.0039(10)<br />

C15 0.0175(11) 0.0216(13) 0.0205(12)<br />

0.0014(10) -0.0018(9) 0.0047(10)<br />

C16 0.0226(12) 0.0208(13) 0.0285(13) -<br />

0.0013(11) -0.0013(10) -0.0010(10)<br />

C17 0.0280(13) 0.0213(13) 0.0381(14) -<br />

0.0138(12) 0.0023(11) -0.0013(11)<br />

C18 0.0217(12) 0.0352(15) 0.0238(13) -<br />

0.0064(11) 0.0010(10) 0.0021(12)<br />

C19 0.0296(13) 0.0268(14) 0.0269(13)<br />

0.0080(11) -0.0029(10) -0.0011(11)<br />

C20 0.0326(13) 0.0180(13) 0.0271(13)<br />

0.0015(11) -0.0012(10) 0.0038(11)<br />

C21 0.0265(12) 0.0194(13) 0.0171(12)<br />

0.0033(9) 0.0011(9) 0.0007(11)<br />

C22 0.0306(13) 0.0204(13) 0.0249(13)<br />

0.0013(10) 0.0045(10) -0.0001(11)<br />

C23 0.0450(15) 0.0228(15) 0.0296(14)<br />

0.0016(11) 0.0040(12) -0.0071(12)<br />

C24 0.0567(17) 0.0179(13) 0.0255(13)<br />

0.0010(11) 0.0079(13) 0.0102(13)<br />

C25 0.0355(13) 0.0308(15) 0.0300(13)<br />

0.0007(12) 0.0117(12) 0.0075(12)<br />

C26 0.0279(13) 0.0211(14) 0.0324(14) 0.0002(10)<br />

0.0037(10) -0.0027(11)<br />

N1 0.0221(10) 0.0200(10) 0.0238(10) -0.0018(9)<br />

0.0016(8) -0.0008(8)<br />

O1 0.0251(8) 0.0176(8) 0.0290(9) 0.0025(7) -<br />

0.0006(7) -0.0024(7)<br />

O2 0.0290(8) 0.0191(9) 0.0251(8) 0.0025(7) -<br />

0.0045(7) -0.0027(7)<br />

_geom_special_details<br />

All esds (except the esd in the dihedral angle<br />

between two l.s. planes)<br />

are estimated using the full covariance matrix. <strong>The</strong><br />

cell esds are taken<br />

in<strong>to</strong> account individually in the estimation of esds<br />

in distances, angles<br />

and <strong>to</strong>rsion angles; correlations between esds in<br />

cell parameters are only<br />

used when they are defined by crystal symmetry.<br />

An approximate (isotropic)<br />

treatment of cell esds is used for estimating esds<br />

involving l.s. planes.<br />

loop_<br />

_geom_bond_a<strong>to</strong>m_site_label_1<br />

_geom_bond_a<strong>to</strong>m_site_label_2<br />

_geom_bond_distance<br />

_geom_bond_site_symmetry_2<br />

_geom_bond_publ_flag<br />

C1 C12 1.502(3) . ?<br />

C1 C6 1.510(2) . ?<br />

C1 C7 1.547(2) . ?<br />

C1 C2 1.561(2) . ?<br />

C2 C3 1.513(2) . ?<br />

C2 C8 1.554(2) . ?<br />

C2 H2 1.0000 . ?<br />

C3 C4 1.329(2) . ?<br />

C3 H3 0.9500 . ?<br />

C4 O1 1.383(2) . ?<br />

291


C4 C5 1.454(2) . ?<br />

C5 C6 1.324(2) . ?<br />

C5 H5 0.9500 . ?<br />

C6 H6 0.9500 . ?<br />

C7 H7A 0.9800 . ?<br />

C7 H7B 0.9800 . ?<br />

C7 H7C 0.9800 . ?<br />

C8 C9 1.529(2) . ?<br />

C8 C10 1.536(2) . ?<br />

C8 H8 1.0000 . ?<br />

C9 H9A 0.9800 . ?<br />

C9 H9B 0.9800 . ?<br />

C9 H9C 0.9800 . ?<br />

C10 H10A 0.9800 . ?<br />

C10 H10B 0.9800 . ?<br />

C10 H10C 0.9800 . ?<br />

C11 O1 1.4329(19) . ?<br />

C11 H11A 0.9800 . ?<br />

C11 H11B 0.9800 . ?<br />

C11 H11C 0.9800 . ?<br />

C12 N1 1.268(2) . ?<br />

C12 O2 1.374(2) . ?<br />

C13 N1 1.474(2) . ?<br />

C13 C15 1.520(2) . ?<br />

C13 C14 1.554(2) . ?<br />

C13 H13 1.0000 . ?<br />

C14 O2 1.461(2) . ?<br />

C14 C21 1.507(3) . ?<br />

C14 H14 1.0000 . ?<br />

C15 C16 1.380(2) . ?<br />

C15 C20 1.394(3) . ?<br />

C16 C17 1.392(2) . ?<br />

C16 H16 0.9500 . ?<br />

C17 C18 1.369(3) . ?<br />

C17 H17 0.9500 . ?<br />

C18 C19 1.390(2) . ?<br />

C18 H18 0.9500 . ?<br />

C19 C20 1.376(3) . ?<br />

C19 H19 0.9500 . ?<br />

C20 H20 0.9500 . ?<br />

C21 C26 1.386(2) . ?<br />

C21 C22 1.386(3) . ?<br />

C22 C23 1.388(3) . ?<br />

C22 H22 0.9500 . ?<br />

C23 C24 1.377(3) . ?<br />

C23 H23 0.9500 . ?<br />

C24 C25 1.381(3) . ?<br />

C24 H24 0.9500 . ?<br />

C25 C26 1.382(2) . ?<br />

C25 H25 0.9500 . ?<br />

C26 H26 0.9500 . ?<br />

loop_<br />

_geom_angle_a<strong>to</strong>m_site_label_1<br />

_geom_angle_a<strong>to</strong>m_site_label_2<br />

_geom_angle_a<strong>to</strong>m_site_label_3<br />

_geom_angle<br />

_geom_angle_site_symmetry_1<br />

_geom_angle_site_symmetry_3<br />

_geom_angle_publ_flag<br />

C12 C1 C6 110.12(16) . . ?<br />

C12 C1 C7 108.26(16) . . ?<br />

C6 C1 C7 106.90(15) . . ?<br />

C12 C1 C2 110.71(16) . . ?<br />

C6 C1 C2 111.73(16) . . ?<br />

C7 C1 C2 108.99(16) . . ?<br />

C3 C2 C8 111.65(16) . . ?<br />

C3 C2 C1 110.92(15) . . ?<br />

C8 C2 C1 115.23(15) . . ?<br />

C3 C2 H2 106.1 . . ?<br />

C8 C2 H2 106.1 . . ?<br />

C1 C2 H2 106.1 . . ?<br />

C4 C3 C2 121.02(18) . . ?<br />

C4 C3 H3 119.5 . . ?<br />

C2 C3 H3 119.5 . . ?<br />

C3 C4 O1 126.65(18) . . ?<br />

C3 C4 C5 121.66(19) . . ?<br />

292


O1 C4 C5 111.68(17) . . ?<br />

C6 C5 C4 120.66(19) . . ?<br />

C6 C5 H5 119.7 . . ?<br />

C4 C5 H5 119.7 . . ?<br />

C5 C6 C1 120.88(19) . . ?<br />

C5 C6 H6 119.6 . . ?<br />

C1 C6 H6 119.6 . . ?<br />

C1 C7 H7A 109.5 . . ?<br />

C1 C7 H7B 109.5 . . ?<br />

H7A C7 H7B 109.5 . . ?<br />

C1 C7 H7C 109.5 . . ?<br />

H7A C7 H7C 109.5 . . ?<br />

H7B C7 H7C 109.5 . . ?<br />

C9 C8 C10 109.79(16) . . ?<br />

C9 C8 C2 113.91(16) . . ?<br />

C10 C8 C2 110.66(15) . . ?<br />

C9 C8 H8 107.4 . . ?<br />

C10 C8 H8 107.4 . . ?<br />

C2 C8 H8 107.4 . . ?<br />

C8 C9 H9A 109.5 . . ?<br />

C8 C9 H9B 109.5 . . ?<br />

H9A C9 H9B 109.5 . . ?<br />

C8 C9 H9C 109.5 . . ?<br />

H9A C9 H9C 109.5 . . ?<br />

H9B C9 H9C 109.5 . . ?<br />

C8 C10 H10A 109.5 . . ?<br />

C8 C10 H10B 109.5 . . ?<br />

H10A C10 H10B 109.5 . . ?<br />

C8 C10 H10C 109.5 . . ?<br />

H10A C10 H10C 109.5 . . ?<br />

H10B C10 H10C 109.5 . . ?<br />

O1 C11 H11A 109.5 . . ?<br />

O1 C11 H11B 109.5 . . ?<br />

H11A C11 H11B 109.5 . . ?<br />

O1 C11 H11C 109.5 . . ?<br />

H11A C11 H11C 109.5 . . ?<br />

H11B C11 H11C 109.5 . . ?<br />

N1 C12 O2 118.01(19) . . ?<br />

N1 C12 C1 127.31(19) . . ?<br />

O2 C12 C1 114.68(17) . . ?<br />

N1 C13 C15 113.56(17) . . ?<br />

N1 C13 C14 104.86(15) . . ?<br />

C15 C13 C14 112.70(15) . . ?<br />

N1 C13 H13 108.5 . . ?<br />

C15 C13 H13 108.5 . . ?<br />

C14 C13 H13 108.5 . . ?<br />

O2 C14 C21 110.07(16) . . ?<br />

O2 C14 C13 103.15(14) . . ?<br />

C21 C14 C13 114.77(16) . . ?<br />

O2 C14 H14 109.5 . . ?<br />

C21 C14 H14 109.5 . . ?<br />

C13 C14 H14 109.5 . . ?<br />

C16 C15 C20 118.76(19) . . ?<br />

C16 C15 C13 122.72(18) . . ?<br />

C20 C15 C13 118.51(19) . . ?<br />

C15 C16 C17 119.6(2) . . ?<br />

C15 C16 H16 120.2 . . ?<br />

C17 C16 H16 120.2 . . ?<br />

C18 C17 C16 121.2(2) . . ?<br />

C18 C17 H17 119.4 . . ?<br />

C16 C17 H17 119.4 . . ?<br />

C17 C18 C19 119.62(19) . . ?<br />

C17 C18 H18 120.2 . . ?<br />

C19 C18 H18 120.2 . . ?<br />

C20 C19 C18 119.2(2) . . ?<br />

C20 C19 H19 120.4 . . ?<br />

C18 C19 H19 120.4 . . ?<br />

C19 C20 C15 121.5(2) . . ?<br />

C19 C20 H20 119.2 . . ?<br />

C15 C20 H20 119.2 . . ?<br />

C26 C21 C22 119.3(2) . . ?<br />

C26 C21 C14 120.31(18) . . ?<br />

C22 C21 C14 120.39(17) . . ?<br />

C21 C22 C23 120.11(19) . . ?<br />

C21 C22 H22 119.9 . . ?<br />

C23 C22 H22 119.9 . . ?<br />

293


C24 C23 C22 120.0(2) . . ?<br />

C24 C23 H23 120.0 . . ?<br />

C22 C23 H23 120.0 . . ?<br />

C23 C24 C25 120.2(2) . . ?<br />

C23 C24 H24 119.9 . . ?<br />

C25 C24 H24 119.9 . . ?<br />

C24 C25 C26 119.8(2) . . ?<br />

C24 C25 H25 120.1 . . ?<br />

C26 C25 H25 120.1 . . ?<br />

C25 C26 C21 120.6(2) . . ?<br />

C25 C26 H26 119.7 . . ?<br />

C21 C26 H26 119.7 . . ?<br />

C12 N1 C13 107.43(17) . . ?<br />

C4 O1 C11 115.58(15) . . ?<br />

C12 O2 C14 106.46(14) . . ?<br />

loop_<br />

_geom_<strong>to</strong>rsion_a<strong>to</strong>m_site_label_1<br />

_geom_<strong>to</strong>rsion_a<strong>to</strong>m_site_label_2<br />

_geom_<strong>to</strong>rsion_a<strong>to</strong>m_site_label_3<br />

_geom_<strong>to</strong>rsion_a<strong>to</strong>m_site_label_4<br />

_geom_<strong>to</strong>rsion<br />

_geom_<strong>to</strong>rsion_site_symmetry_1<br />

_geom_<strong>to</strong>rsion_site_symmetry_2<br />

_geom_<strong>to</strong>rsion_site_symmetry_3<br />

_geom_<strong>to</strong>rsion_site_symmetry_4<br />

_geom_<strong>to</strong>rsion_publ_flag<br />

C12 C1 C2 C3 -163.89(16) . . . . ?<br />

C6 C1 C2 C3 -40.8(2) . . . . ?<br />

C7 C1 C2 C3 77.1(2) . . . . ?<br />

C12 C1 C2 C8 -35.8(2) . . . . ?<br />

C6 C1 C2 C8 87.3(2) . . . . ?<br />

C7 C1 C2 C8 -154.78(16) . . . . ?<br />

C8 C2 C3 C4 -101.69(19) . . . . ?<br />

C1 C2 C3 C4 28.3(3) . . . . ?<br />

C2 C3 C4 O1 177.08(16) . . . . ?<br />

C2 C3 C4 C5 -2.3(3) . . . . ?<br />

C3 C4 C5 C6 -10.9(3) . . . . ?<br />

O1 C4 C5 C6 169.62(17) . . . . ?<br />

C4 C5 C6 C1 -5.7(3) . . . . ?<br />

C12 C1 C6 C5 155.26(18) . . . . ?<br />

C7 C1 C6 C5 -87.4(2) . . . . ?<br />

C2 C1 C6 C5 31.8(3) . . . . ?<br />

C3 C2 C8 C9 62.9(2) . . . . ?<br />

C1 C2 C8 C9 -64.8(2) . . . . ?<br />

C3 C2 C8 C10 -61.4(2) . . . . ?<br />

C1 C2 C8 C10 170.93(16) . . . . ?<br />

C6 C1 C12 N1 -13.7(3) . . . . ?<br />

C7 C1 C12 N1 -130.2(2) . . . . ?<br />

C2 C1 C12 N1 110.4(2) . . . . ?<br />

C6 C1 C12 O2 165.72(15) . . . . ?<br />

C7 C1 C12 O2 49.2(2) . . . . ?<br />

C2 C1 C12 O2 -70.2(2) . . . . ?<br />

N1 C13 C14 O2 3.15(19) . . . . ?<br />

C15 C13 C14 O2 -120.85(16) . . . . ?<br />

N1 C13 C14 C21 -116.57(17) . . . . ?<br />

C15 C13 C14 C21 119.43(18) . . . . ?<br />

N1 C13 C15 C16 2.5(3) . . . . ?<br />

C14 C13 C15 C16 121.6(2) . . . . ?<br />

N1 C13 C15 C20 -178.81(17) . . . . ?<br />

C14 C13 C15 C20 -59.8(2) . . . . ?<br />

C20 C15 C16 C17 -0.7(3) . . . . ?<br />

C13 C15 C16 C17 177.94(17) . . . . ?<br />

C15 C16 C17 C18 -0.5(3) . . . . ?<br />

C16 C17 C18 C19 1.9(3) . . . . ?<br />

C17 C18 C19 C20 -2.0(3) . . . . ?<br />

C18 C19 C20 C15 0.8(3) . . . . ?<br />

C16 C15 C20 C19 0.6(3) . . . . ?<br />

C13 C15 C20 C19 -178.16(17) . . . . ?<br />

O2 C14 C21 C26 -57.4(2) . . . . ?<br />

C13 C14 C21 C26 58.4(2) . . . . ?<br />

O2 C14 C21 C22 124.92(17) . . . . ?<br />

C13 C14 C21 C22 -119.28(19) . . . . ?<br />

C26 C21 C22 C23 -1.3(3) . . . . ?<br />

C14 C21 C22 C23 176.39(18) . . . . ?<br />

294


C21 C22 C23 C24 0.4(3) . . . . ?<br />

C22 C23 C24 C25 0.7(3) . . . . ?<br />

C23 C24 C25 C26 -0.8(3) . . . . ?<br />

C24 C25 C26 C21 -0.2(3) . . . . ?<br />

C22 C21 C26 C25 1.3(3) . . . . ?<br />

C14 C21 C26 C25 -176.48(19) . . . . ?<br />

O2 C12 N1 C13 0.7(2) . . . . ?<br />

C1 C12 N1 C13 -179.88(18) . . . . ?<br />

C15 C13 N1 C12 121.00(17) . . . . ?<br />

C14 C13 N1 C12 -2.4(2) . . . . ?<br />

C3 C4 O1 C11 -0.1(3) . . . . ?<br />

C5 C4 O1 C11 179.39(15) . . . . ?<br />

N1 C12 O2 C14 1.5(2) . . . . ?<br />

C1 C12 O2 C14 -178.00(15) . . . . ?<br />

C21 C14 O2 C12 120.13(17) . . . . ?<br />

C13 C14 O2 C12 -2.78(18) . . . . ?<br />

_diffrn_measured_fraction_theta_max<br />

0.970<br />

_diffrn_reflns_theta_full 28.29<br />

_diffrn_measured_fraction_theta_full<br />

0.970<br />

_refine_diff_density_max 0.175<br />

_refine_diff_density_min -0.143<br />

_refine_diff_density_rms 0.035<br />

295


. Compound 102c<br />

Ph<br />

O<br />

N<br />

Ph<br />

Me<br />

102c<br />

OMe<br />

Identification code s2291abs<br />

Empirical formula C26 H29 N O2<br />

Formula weight 387.50<br />

Temperature<br />

100(2) K<br />

Wavelength<br />

0.71073 A<br />

Crystal system, space group Orthorhombic, P2(1)2(1)2(1)<br />

Unit cell dimensions a = 8.2463(6) A alpha = 90 deg.<br />

b = 10.6095(7) A beta = 90 deg.<br />

c = 24.6291(19) A gamma = 90 deg.<br />

Volume<br />

2154.8(3) A^3<br />

Z, Calculated density 4, 1.194 Mg/m^3<br />

Absorption coefficient 0.075 mm^-1<br />

F(000) 832<br />

Crystal size<br />

0.70 x 0.50 x 0.50 mm<br />

<strong>The</strong>ta range for data collection 1.65 <strong>to</strong> 26.37 deg.<br />

Limiting indices -10


<strong>The</strong> structure was solved by the direct methods.<br />

All non-H a<strong>to</strong>ms were refined anisotropically.<br />

H a<strong>to</strong>ms were included in calculated positions.<br />

_chemical_name_common ?<br />

_chemical_melting_point ?<br />

_chemical_formula_moiety ?<br />

_chemical_formula_sum<br />

'C26 H29 N O2'<br />

_chemical_formula_weight 387.50<br />

loop_<br />

_a<strong>to</strong>m_type_symbol<br />

_a<strong>to</strong>m_type_description<br />

_a<strong>to</strong>m_type_scat_dispersion_real<br />

_a<strong>to</strong>m_type_scat_dispersion_imag<br />

_a<strong>to</strong>m_type_scat_source<br />

'C' 'C' 0.0033 0.0016<br />

'International Tables Vol C Tables 4.2.6.8 and<br />

6.1.1.4'<br />

'H' 'H' 0.0000 0.0000<br />

'International Tables Vol C Tables 4.2.6.8 and<br />

6.1.1.4'<br />

'N' 'N' 0.0061 0.0033<br />

'International Tables Vol C Tables 4.2.6.8 and<br />

6.1.1.4'<br />

'O' 'O' 0.0106 0.0060<br />

'International Tables Vol C Tables 4.2.6.8 and<br />

6.1.1.4'<br />

_symmetry_cell_setting Orthorhombic<br />

_symmetry_space_group_name_H-M<br />

P2(1)2(1)2(1)<br />

loop_<br />

_symmetry_equiv_pos_as_xyz<br />

'x, y, z'<br />

'-x+1/2, -y, z+1/2'<br />

'-x, y+1/2, -z+1/2'<br />

'x+1/2, -y+1/2, -z'<br />

_cell_length_a 8.2463(6)<br />

_cell_length_b 10.6095(7)<br />

_cell_length_c 24.6291(19)<br />

_cell_angle_alpha 90.00<br />

_cell_angle_beta 90.00<br />

_cell_angle_gamma 90.00<br />

_cell_volume 2154.8(3)<br />

_cell_formula_units_Z 4<br />

_cell_measurement_temperature 100(2)<br />

_cell_measurement_reflns_used 4494<br />

_cell_measurement_theta_min 2.54<br />

_cell_measurement_theta_max 26.37<br />

_exptl_crystal_description irregular<br />

_exptl_crystal_colour colourless<br />

_exptl_crystal_size_max 0.70<br />

_exptl_crystal_size_mid 0.50<br />

_exptl_crystal_size_min 0.50<br />

_exptl_crystal_density_meas ?<br />

_exptl_crystal_density_diffrn 1.194<br />

_exptl_crystal_density_method 'not measured'<br />

_exptl_crystal_F_000 832<br />

_exptl_absorpt_coefficient_mu 0.075<br />

_exptl_absorpt_correction_type multi-scan<br />

_exptl_absorpt_correction_T_min 0.9497<br />

_exptl_absorpt_correction_T_max 0.9637<br />

_exptl_absorpt_process_details 'SADABS'<br />

_exptl_special_details<br />

_diffrn_ambient_temperature 100(2)<br />

_diffrn_radiation_wavelength 0.71073<br />

_diffrn_radiation_type MoK\a<br />

_diffrn_radiation_source 'fine-focus sealed<br />

tube'<br />

_diffrn_radiation_monochroma<strong>to</strong>r graphite<br />

_diffrn_measurement_device_type 'CCD area<br />

detec<strong>to</strong>r'<br />

_diffrn_measurement_method 'phi and omega<br />

scans'<br />

_diffrn_detec<strong>to</strong>r_area_resol_mean ?<br />

_diffrn_standards_number ?<br />

_diffrn_standards_interval_count ?<br />

297


_diffrn_standards_interval_time ?<br />

_diffrn_standards_decay_% ?<br />

_diffrn_reflns_number 8895<br />

_diffrn_reflns_av_R_equivalents 0.0314<br />

_diffrn_reflns_av_sigmaI/netI 0.0297<br />

_diffrn_reflns_limit_h_min -10<br />

_diffrn_reflns_limit_h_max 6<br />

_diffrn_reflns_limit_k_min -7<br />

_diffrn_reflns_limit_k_max 13<br />

_diffrn_reflns_limit_l_min -30<br />

_diffrn_reflns_limit_l_max 22<br />

_diffrn_reflns_theta_min 1.65<br />

_diffrn_reflns_theta_max 26.37<br />

_reflns_number_<strong>to</strong>tal 2509<br />

_reflns_number_gt 2370<br />

_reflns_threshold_expression >2sigma(I)<br />

_computing_data_collection 'Bruker SMART'<br />

_computing_cell_refinement 'Bruker SMART'<br />

_computing_data_reduction 'Bruker SAINT'<br />

_computing_structure_solution 'SHELXS-97<br />

(Sheldrick, 1990)'<br />

_computing_structure_refinement 'SHELXL-97<br />

(Sheldrick, 1997)'<br />

_computing_molecular_graphics 'Bruker<br />

SHELXTL'<br />

_computing_publication_material 'Bruker<br />

SHELXTL'<br />

_refine_special_details<br />

Refinement of F^2^ against ALL reflections. <strong>The</strong><br />

weighted R-fac<strong>to</strong>r wR and<br />

goodness of fit S are based on F^2^, conventional<br />

R-fac<strong>to</strong>rs R are based<br />

on F, with F set <strong>to</strong> zero for negative F^2^. <strong>The</strong><br />

threshold expression of<br />

F^2^ > 2sigma(F^2^) is used only for calculating<br />

R-fac<strong>to</strong>rs(gt) etc. and is<br />

not relevant <strong>to</strong> the choice of reflections for<br />

refinement. R-fac<strong>to</strong>rs based<br />

on F^2^ are statistically about twice as large as<br />

those based on F, and R-<br />

fac<strong>to</strong>rs based on ALL data will be even larger.<br />

_refine_ls_structure_fac<strong>to</strong>r_coef Fsqd<br />

_refine_ls_matrix_type full<br />

_refine_ls_weighting_scheme calc<br />

_refine_ls_weighting_details<br />

'calc w=1/[\s^2^(Fo^2^)+(0.0405P)^2^+0.5305P]<br />

where P=(Fo^2^+2Fc^2^)/3'<br />

_a<strong>to</strong>m_sites_solution_primary direct<br />

_a<strong>to</strong>m_sites_solution_secondary difmap<br />

_a<strong>to</strong>m_sites_solution_hydrogens geom<br />

_refine_ls_hydrogen_treatment constr<br />

_refine_ls_extinction_method none<br />

298


_refine_ls_extinction_coef ?<br />

_refine_ls_abs_structure_details<br />

'Flack H D (1983), Acta Cryst. A39, 876-881'<br />

_refine_ls_abs_structure_Flack -0.4(13)<br />

_chemical_absolute_configuration syn<br />

_refine_ls_number_reflns 2509<br />

_refine_ls_number_parameters 266<br />

_refine_ls_number_restraints 0<br />

_refine_ls_R_fac<strong>to</strong>r_all 0.0350<br />

_refine_ls_R_fac<strong>to</strong>r_gt 0.0326<br />

_refine_ls_wR_fac<strong>to</strong>r_ref 0.0820<br />

_refine_ls_wR_fac<strong>to</strong>r_gt 0.0802<br />

_refine_ls_goodness_of_fit_ref 1.040<br />

_refine_ls_restrained_S_all 1.040<br />

_refine_ls_shift/su_max 0.001<br />

_refine_ls_shift/su_mean 0.000<br />

loop_<br />

_a<strong>to</strong>m_site_label<br />

_a<strong>to</strong>m_site_type_symbol<br />

_a<strong>to</strong>m_site_fract_x<br />

_a<strong>to</strong>m_site_fract_y<br />

_a<strong>to</strong>m_site_fract_z<br />

_a<strong>to</strong>m_site_U_iso_or_equiv<br />

_a<strong>to</strong>m_site_adp_type<br />

_a<strong>to</strong>m_site_occupancy<br />

_a<strong>to</strong>m_site_symmetry_multiplicity<br />

_a<strong>to</strong>m_site_calc_flag<br />

_a<strong>to</strong>m_site_refinement_flags<br />

_a<strong>to</strong>m_site_disorder_assembly<br />

_a<strong>to</strong>m_site_disorder_group<br />

O1 O 0.74597(16) 1.07720(12) 0.59978(5)<br />

0.0224(3) Uani 1 1 d . . .<br />

O2 O 0.85316(16) 1.21137(12) 0.80110(5)<br />

0.0207(3) Uani 1 1 d . . .<br />

N1 N 0.55197(18) 0.93270(14) 0.61905(6)<br />

0.0183(3) Uani 1 1 d . . .<br />

C1 C 0.6322(2) 1.02851(17) 0.63416(7)<br />

0.0195(4) Uani 1 1 d . . .<br />

C2 C 0.6042(2) 0.90213(16) 0.56341(7) 0.0177(4)<br />

Uani 1 1 d . . .<br />

H2 H 0.5123 0.9197 0.5380 0.021 Uiso 1 1 calc R .<br />

.<br />

C3 C 0.7436(2) 0.99817(16) 0.55146(7) 0.0180(4)<br />

Uani 1 1 d . . .<br />

H3 H 0.8490 0.9522 0.5481 0.022 Uiso 1 1 calc R .<br />

.<br />

C4 C 0.6086(2) 1.10139(17) 0.68643(7) 0.0182(4)<br />

Uani 1 1 d . . .<br />

C5 C 0.7666(2) 1.10303(16) 0.72129(7) 0.0166(3)<br />

Uani 1 1 d . . .<br />

H5 H 0.8392 1.1682 0.7049 0.020 Uiso 1 1 calc R .<br />

.<br />

C6 C 0.7256(2) 1.14878(15) 0.77815(7) 0.0175(4)<br />

Uani 1 1 d . . .<br />

C7 C 0.5818(2) 1.12851(17) 0.80158(7) 0.0194(4)<br />

Uani 1 1 d . . .<br />

H7 H 0.5631 1.1548 0.8379 0.023 Uiso 1 1 calc R .<br />

.<br />

C8 C 0.4539(2) 1.06579(17) 0.77093(7) 0.0208(4)<br />

Uani 1 1 d . . .<br />

H8 H 0.3602 1.0365 0.7895 0.025 Uiso 1 1 calc R .<br />

.<br />

C9 C 0.4653(2) 1.04862(17) 0.71759(7) 0.0205(4)<br />

Uani 1 1 d . . .<br />

H9 H 0.3832 1.0031 0.6989 0.025 Uiso 1 1 calc R .<br />

.<br />

C10 C 0.5667(3) 1.23878(18) 0.67028(7) 0.0254(4)<br />

Uani 1 1 d . . .<br />

H10A H 0.4680 1.2393 0.6481 0.038 Uiso 1 1 calc<br />

R . .<br />

H10B H 0.6566 1.2749 0.6494 0.038 Uiso 1 1 calc<br />

R . .<br />

H10C H 0.5489 1.2891 0.7031 0.038 Uiso 1 1 calc<br />

R . .<br />

C11 C 0.8641(2) 0.97756(16) 0.72155(7) 0.0183(4)<br />

Uani 1 1 d . . .<br />

299


H11 H 0.8924 0.9592 0.6829 0.022 Uiso 1 1 calc<br />

R . .<br />

C12 C 0.7710(2) 0.86323(16) 0.74238(7)<br />

0.0208(4) Uani 1 1 d . . .<br />

H12A H 0.7395 0.8772 0.7803 0.031 Uiso 1 1<br />

calc R . .<br />

H12B H 0.8401 0.7883 0.7400 0.031 Uiso 1 1<br />

calc R . .<br />

H12C H 0.6736 0.8507 0.7202 0.031 Uiso 1 1<br />

calc R . .<br />

C13 C 1.0248(2) 0.99158(18) 0.75205(9)<br />

0.0267(4) Uani 1 1 d . . .<br />

H13A H 1.0905 0.9156 0.7468 0.040 Uiso 1 1<br />

calc R . .<br />

H13B H 1.0032 1.0032 0.7909 0.040 Uiso 1 1<br />

calc R . .<br />

H13C H 1.0837 1.0650 0.7381 0.040 Uiso 1 1<br />

calc R . .<br />

C14 C 0.8279(2) 1.25963(18) 0.85485(7)<br />

0.0229(4) Uani 1 1 d . . .<br />

H14A H 0.8102 1.1894 0.8800 0.034 Uiso 1 1<br />

calc R . .<br />

H14B H 0.7327 1.3149 0.8550 0.034 Uiso 1 1<br />

calc R . .<br />

H14C H 0.9236 1.3076 0.8663 0.034 Uiso 1 1<br />

calc R . .<br />

C15 C 0.6557(2) 0.76646(16) 0.55634(7)<br />

0.0183(4) Uani 1 1 d . . .<br />

C16 C 0.7354(2) 0.70087(18) 0.59737(7)<br />

0.0229(4) Uani 1 1 d . . .<br />

H16 H 0.7541 0.7404 0.6314 0.028 Uiso 1 1 calc<br />

R . .<br />

C17 C 0.7879(3) 0.57792(19) 0.58883(8)<br />

0.0281(4) Uani 1 1 d . . .<br />

H17 H 0.8419 0.5337 0.6171 0.034 Uiso 1 1 calc<br />

R . .<br />

C18 C 0.7618(3) 0.51959(18) 0.53929(9)<br />

0.0292(4) Uani 1 1 d . . .<br />

H18 H 0.7974 0.4355 0.5336 0.035 Uiso 1 1 calc R<br />

. .<br />

C19 C 0.6835(2) 0.58456(19) 0.49813(8) 0.0276(4)<br />

Uani 1 1 d . . .<br />

H19 H 0.6666 0.5452 0.4639 0.033 Uiso 1 1 calc R<br />

. .<br />

C20 C 0.6296(2) 0.70694(18) 0.50665(7) 0.0231(4)<br />

Uani 1 1 d . . .<br />

H20 H 0.5746 0.7504 0.4784 0.028 Uiso 1 1 calc R<br />

. .<br />

C21 C 0.7137(2) 1.07484(16) 0.50097(7) 0.0180(4)<br />

Uani 1 1 d . . .<br />

C22 C 0.7765(2) 1.03311(17) 0.45186(7) 0.0230(4)<br />

Uani 1 1 d . . .<br />

H22 H 0.8464 0.9620 0.4512 0.028 Uiso 1 1 calc R<br />

. .<br />

C23 C 0.7381(3) 1.09433(18) 0.40382(7) 0.0272(4)<br />

Uani 1 1 d . . .<br />

H23 H 0.7804 1.0643 0.3703 0.033 Uiso 1 1 calc R<br />

. .<br />

C24 C 0.6379(3) 1.19955(19) 0.40461(7) 0.0280(4)<br />

Uani 1 1 d . . .<br />

H24 H 0.6108 1.2415 0.3717 0.034 Uiso 1 1 calc R<br />

. .<br />

C25 C 0.5778(3) 1.24278(18) 0.45361(8) 0.0274(4)<br />

Uani 1 1 d . . .<br />

H25 H 0.5107 1.3156 0.4543 0.033 Uiso 1 1 calc R<br />

. .<br />

C26 C 0.6143(2) 1.18102(17) 0.50177(7) 0.0229(4)<br />

Uani 1 1 d . . .<br />

H26 H 0.5716 1.2111 0.5352 0.028 Uiso 1 1 calc R<br />

. . loop_<br />

_a<strong>to</strong>m_site_aniso_label<br />

_a<strong>to</strong>m_site_aniso_U_11<br />

_a<strong>to</strong>m_site_aniso_U_22<br />

_a<strong>to</strong>m_site_aniso_U_33<br />

_a<strong>to</strong>m_site_aniso_U_23<br />

_a<strong>to</strong>m_site_aniso_U_13<br />

300


_a<strong>to</strong>m_site_aniso_U_12<br />

O1 0.0253(7) 0.0262(6) 0.0156(6) -0.0021(5)<br />

0.0016(5) -0.0058(6)<br />

O2 0.0212(6) 0.0213(6) 0.0196(6) -0.0046(5)<br />

0.0022(5) -0.0030(6)<br />

N1 0.0203(7) 0.0189(7) 0.0157(7) -0.0002(6)<br />

0.0029(6) 0.0017(7)<br />

C1 0.0197(8) 0.0227(8) 0.0162(8) 0.0041(7) -<br />

0.0015(7) 0.0051(8)<br />

C2 0.0173(8) 0.0212(9) 0.0146(8) 0.0015(7) -<br />

0.0006(7) -0.0005(7)<br />

C3 0.0191(8) 0.0193(8) 0.0157(8) -0.0022(7) -<br />

0.0003(7) -0.0009(7)<br />

C4 0.0193(9) 0.0195(8) 0.0160(8) 0.0003(7)<br />

0.0005(7) 0.0017(7)<br />

C5 0.0174(8) 0.0161(8) 0.0163(8) 0.0009(7)<br />

0.0019(7) -0.0016(7)<br />

C6 0.0199(9) 0.0145(7) 0.0181(8) 0.0000(7)<br />

0.0000(7) 0.0013(7)<br />

C7 0.0233(9) 0.0205(9) 0.0145(8) -0.0018(7)<br />

0.0027(7) 0.0023(8)<br />

C8 0.0179(8) 0.0214(8) 0.0231(9) -0.0013(7)<br />

0.0040(7) 0.0008(7)<br />

C9 0.0158(8) 0.0226(9) 0.0233(9) -0.0037(7) -<br />

0.0004(7) 0.0015(7)<br />

C10 0.0311(10) 0.0241(9) 0.0210(9) 0.0002(8) -<br />

0.0004(8) 0.0069(9)<br />

C11 0.0179(8) 0.0196(8) 0.0172(8) -0.0039(7)<br />

0.0018(7) 0.0023(7)<br />

C12 0.0241(9) 0.0190(8) 0.0192(8) -0.0001(7)<br />

0.0001(8) 0.0011(8)<br />

C13 0.0197(10) 0.0258(10) 0.0345(10) -<br />

0.0089(8) -0.0030(8) 0.0035(8)<br />

C14 0.0278(10) 0.0228(9) 0.0180(8) -0.0040(7)<br />

-0.0012(7) -0.0019(8)<br />

C15 0.0158(8) 0.0198(9) 0.0193(8) 0.0010(7)<br />

0.0054(7) -0.0039(7)<br />

C16 0.0249(9) 0.0260(9) 0.0178(8) 0.0001(7)<br />

0.0024(8) 0.0028(9)<br />

C17 0.0282(10) 0.0253(9) 0.0306(10) 0.0064(8)<br />

0.0046(8) 0.0046(9)<br />

C18 0.0244(10) 0.0212(9) 0.0421(11) -0.0032(9)<br />

0.0105(9) 0.0012(9)<br />

C19 0.0260(10) 0.0285(10) 0.0282(10) -0.0099(8)<br />

0.0056(8) -0.0048(9)<br />

C20 0.0224(9) 0.0257(9) 0.0211(8) -0.0005(8) -<br />

0.0001(8) -0.0026(8)<br />

C21 0.0189(8) 0.0179(8) 0.0171(8) 0.0008(7) -<br />

0.0006(7) -0.0048(7)<br />

C22 0.0278(10) 0.0197(8) 0.0213(8) 0.0002(7)<br />

0.0022(8) 0.0007(8)<br />

C23 0.0381(11) 0.0268(10) 0.0166(8) 0.0002(7)<br />

0.0036(8) -0.0027(10)<br />

C24 0.0356(11) 0.0263(9) 0.0221(9) 0.0100(8) -<br />

0.0019(8) -0.0037(9)<br />

C25 0.0279(10) 0.0216(9) 0.0326(10) 0.0045(8)<br />

0.0012(8) 0.0021(9)<br />

C26 0.0246(10) 0.0225(9) 0.0217(9) -0.0013(7)<br />

0.0046(8) 0.0000(8)<br />

_geom_special_details<br />

loop_<br />

_geom_bond_a<strong>to</strong>m_site_label_1<br />

_geom_bond_a<strong>to</strong>m_site_label_2<br />

_geom_bond_distance<br />

_geom_bond_site_symmetry_2<br />

_geom_bond_publ_flag<br />

O1 C1 1.365(2) . ?<br />

O1 C3 1.456(2) . ?<br />

O2 C6 1.366(2) . ?<br />

O2 C14 1.434(2) . ?<br />

N1 C1 1.269(2) . ?<br />

N1 C2 1.473(2) . ?<br />

C1 C4 1.514(2) . ?<br />

C2 C15 1.511(2) . ?<br />

C2 C3 1.564(2) . ?<br />

301


C2 H2 1.0000 . ?<br />

C3 C21 1.506(2) . ?<br />

C3 H3 1.0000 . ?<br />

C4 C9 1.516(2) . ?<br />

C4 C10 1.550(3) . ?<br />

C4 C5 1.560(2) . ?<br />

C5 C6 1.520(2) . ?<br />

C5 C11 1.555(2) . ?<br />

C5 H5 1.0000 . ?<br />

C6 C7 1.336(3) . ?<br />

C7 C8 1.458(3) . ?<br />

C7 H7 0.9500 . ?<br />

C8 C9 1.330(3) . ?<br />

C8 H8 0.9500 . ?<br />

C9 H9 0.9500 . ?<br />

C10 H10A 0.9800 . ?<br />

C10 H10B 0.9800 . ?<br />

C10 H10C 0.9800 . ?<br />

C11 C12 1.524(2) . ?<br />

C11 C13 1.531(3) . ?<br />

C11 H11 1.0000 . ?<br />

C12 H12A 0.9800 . ?<br />

C12 H12B 0.9800 . ?<br />

C12 H12C 0.9800 . ?<br />

C13 H13A 0.9800 . ?<br />

C13 H13B 0.9800 . ?<br />

C13 H13C 0.9800 . ?<br />

C14 H14A 0.9800 . ?<br />

C14 H14B 0.9800 . ?<br />

C14 H14C 0.9800 . ?<br />

C15 C16 1.392(3) . ?<br />

C15 C20 1.394(2) . ?<br />

C16 C17 1.390(3) . ?<br />

C16 H16 0.9500 . ?<br />

C17 C18 1.385(3) . ?<br />

C17 H17 0.9500 . ?<br />

C18 C19 1.386(3) . ?<br />

C18 H18 0.9500 . ?<br />

C19 C20 1.388(3) . ?<br />

C19 H19 0.9500 . ?<br />

C20 H20 0.9500 . ?<br />

C21 C22 1.388(2) . ?<br />

C21 C26 1.393(3) . ?<br />

C22 C23 1.386(3) . ?<br />

C22 H22 0.9500 . ?<br />

C23 C24 1.389(3) . ?<br />

C23 H23 0.9500 . ?<br />

C24 C25 1.383(3) . ?<br />

C24 H24 0.9500 . ?<br />

C25 C26 1.388(3) . ?<br />

C25 H25 0.9500 . ?<br />

C26 H26 0.9500 . ?<br />

loop_<br />

_geom_angle_a<strong>to</strong>m_site_label_1<br />

_geom_angle_a<strong>to</strong>m_site_label_2<br />

_geom_angle_a<strong>to</strong>m_site_label_3<br />

_geom_angle<br />

_geom_angle_site_symmetry_1<br />

_geom_angle_site_symmetry_3<br />

_geom_angle_publ_flag<br />

C1 O1 C3 106.24(13) . . ?<br />

C6 O2 C14 116.32(14) . . ?<br />

C1 N1 C2 107.28(14) . . ?<br />

N1 C1 O1 118.65(15) . . ?<br />

N1 C1 C4 126.28(16) . . ?<br />

O1 C1 C4 114.97(15) . . ?<br />

N1 C2 C15 113.53(13) . . ?<br />

N1 C2 C3 104.28(13) . . ?<br />

C15 C2 C3 113.13(14) . . ?<br />

N1 C2 H2 108.6 . . ?<br />

C15 C2 H2 108.6 . . ?<br />

C3 C2 H2 108.6 . . ?<br />

O1 C3 C21 111.48(14) . . ?<br />

O1 C3 C2 103.38(13) . . ?<br />

C21 C3 C2 112.77(14) . . ?<br />

O1 C3 H3 109.7 . . ?<br />

302


C21 C3 H3 109.7 . . ?<br />

C2 C3 H3 109.7 . . ?<br />

C1 C4 C9 109.98(15) . . ?<br />

C1 C4 C10 106.90(14) . . ?<br />

C9 C4 C10 107.64(15) . . ?<br />

C1 C4 C5 111.49(14) . . ?<br />

C9 C4 C5 112.12(14) . . ?<br />

C10 C4 C5 108.48(15) . . ?<br />

C6 C5 C11 112.60(14) . . ?<br />

C6 C5 C4 108.95(14) . . ?<br />

C11 C5 C4 115.11(14) . . ?<br />

C6 C5 H5 106.5 . . ?<br />

C11 C5 H5 106.5 . . ?<br />

C4 C5 H5 106.5 . . ?<br />

C7 C6 O2 125.65(15) . . ?<br />

C7 C6 C5 122.94(16) . . ?<br />

O2 C6 C5 111.41(15) . . ?<br />

C6 C7 C8 119.48(15) . . ?<br />

C6 C7 H7 120.3 . . ?<br />

C8 C7 H7 120.3 . . ?<br />

C9 C8 C7 121.53(17) . . ?<br />

C9 C8 H8 119.2 . . ?<br />

C7 C8 H8 119.2 . . ?<br />

C8 C9 C4 120.30(17) . . ?<br />

C8 C9 H9 119.9 . . ?<br />

C4 C9 H9 119.9 . . ?<br />

C4 C10 H10A 109.5 . . ?<br />

C4 C10 H10B 109.5 . . ?<br />

H10A C10 H10B 109.5 . . ?<br />

C4 C10 H10C 109.5 . . ?<br />

H10A C10 H10C 109.5 . . ?<br />

H10B C10 H10C 109.5 . . ?<br />

C12 C11 C13 110.37(15) . . ?<br />

C12 C11 C5 115.00(14) . . ?<br />

C13 C11 C5 111.50(14) . . ?<br />

C12 C11 H11 106.5 . . ?<br />

C13 C11 H11 106.5 . . ?<br />

C5 C11 H11 106.5 . . ?<br />

C11 C12 H12A 109.5 . . ?<br />

C11 C12 H12B 109.5 . . ?<br />

H12A C12 H12B 109.5 . . ?<br />

C11 C12 H12C 109.5 . . ?<br />

H12A C12 H12C 109.5 . . ?<br />

H12B C12 H12C 109.5 . . ?<br />

C11 C13 H13A 109.5 . . ?<br />

C11 C13 H13B 109.5 . . ?<br />

H13A C13 H13B 109.5 . . ?<br />

C11 C13 H13C 109.5 . . ?<br />

H13A C13 H13C 109.5 . . ?<br />

H13B C13 H13C 109.5 . . ?<br />

O2 C14 H14A 109.5 . . ?<br />

O2 C14 H14B 109.5 . . ?<br />

H14A C14 H14B 109.5 . . ?<br />

O2 C14 H14C 109.5 . . ?<br />

H14A C14 H14C 109.5 . . ?<br />

H14B C14 H14C 109.5 . . ?<br />

C16 C15 C20 118.93(16) . . ?<br />

C16 C15 C2 121.70(15) . . ?<br />

C20 C15 C2 119.29(16) . . ?<br />

C17 C16 C15 120.42(17) . . ?<br />

C17 C16 H16 119.8 . . ?<br />

C15 C16 H16 119.8 . . ?<br />

C18 C17 C16 120.28(19) . . ?<br />

C18 C17 H17 119.9 . . ?<br />

C16 C17 H17 119.9 . . ?<br />

C17 C18 C19 119.65(18) . . ?<br />

C17 C18 H18 120.2 . . ?<br />

C19 C18 H18 120.2 . . ?<br />

C18 C19 C20 120.25(18) . . ?<br />

C18 C19 H19 119.9 . . ?<br />

C20 C19 H19 119.9 . . ?<br />

C19 C20 C15 120.46(18) . . ?<br />

C19 C20 H20 119.8 . . ?<br />

C15 C20 H20 119.8 . . ?<br />

C22 C21 C26 119.32(16) . . ?<br />

C22 C21 C3 119.08(16) . . ?<br />

303


C26 C21 C3 121.41(15) . . ?<br />

C23 C22 C21 120.59(17) . . ?<br />

C23 C22 H22 119.7 . . ?<br />

C21 C22 H22 119.7 . . ?<br />

C22 C23 C24 120.03(17) . . ?<br />

C22 C23 H23 120.0 . . ?<br />

C24 C23 H23 120.0 . . ?<br />

C25 C24 C23 119.47(17) . . ?<br />

C25 C24 H24 120.3 . . ?<br />

C23 C24 H24 120.3 . . ?<br />

C24 C25 C26 120.76(18) . . ?<br />

C24 C25 H25 119.6 . . ?<br />

C26 C25 H25 119.6 . . ?<br />

C25 C26 C21 119.81(17) . . ?<br />

C25 C26 H26 120.1 . . ?<br />

C21 C26 H26 120.1 . . ?<br />

loop_<br />

_geom_<strong>to</strong>rsion_a<strong>to</strong>m_site_label_1<br />

_geom_<strong>to</strong>rsion_a<strong>to</strong>m_site_label_2<br />

_geom_<strong>to</strong>rsion_a<strong>to</strong>m_site_label_3<br />

_geom_<strong>to</strong>rsion_a<strong>to</strong>m_site_label_4<br />

_geom_<strong>to</strong>rsion<br />

_geom_<strong>to</strong>rsion_site_symmetry_1<br />

_geom_<strong>to</strong>rsion_site_symmetry_2<br />

_geom_<strong>to</strong>rsion_site_symmetry_3<br />

_geom_<strong>to</strong>rsion_site_symmetry_4<br />

_geom_<strong>to</strong>rsion_publ_flag<br />

C2 N1 C1 O1 -2.4(2) . . . . ?<br />

C2 N1 C1 C4 173.89(16) . . . . ?<br />

C3 O1 C1 N1 -0.3(2) . . . . ?<br />

C3 O1 C1 C4 -177.07(14) . . . . ?<br />

C1 N1 C2 C15 127.44(16) . . . . ?<br />

C1 N1 C2 C3 3.88(18) . . . . ?<br />

C1 O1 C3 C21 124.14(15) . . . . ?<br />

C1 O1 C3 C2 2.73(17) . . . . ?<br />

N1 C2 C3 O1 -3.96(16) . . . . ?<br />

C15 C2 C3 O1 -127.78(14) . . . . ?<br />

N1 C2 C3 C21 -124.49(15) . . . . ?<br />

C15 C2 C3 C21 111.69(16) . . . . ?<br />

N1 C1 C4 C9 -3.8(2) . . . . ?<br />

O1 C1 C4 C9 172.64(14) . . . . ?<br />

N1 C1 C4 C10 -120.4(2) . . . . ?<br />

O1 C1 C4 C10 56.1(2) . . . . ?<br />

N1 C1 C4 C5 121.23(19) . . . . ?<br />

O1 C1 C4 C5 -62.34(19) . . . . ?<br />

C1 C4 C5 C6 -166.51(14) . . . . ?<br />

C9 C4 C5 C6 -42.70(19) . . . . ?<br />

C10 C4 C5 C6 76.04(17) . . . . ?<br />

C1 C4 C5 C11 -38.9(2) . . . . ?<br />

C9 C4 C5 C11 84.87(18) . . . . ?<br />

C10 C4 C5 C11 -156.39(15) . . . . ?<br />

C14 O2 C6 C7 -0.5(3) . . . . ?<br />

C14 O2 C6 C5 179.64(14) . . . . ?<br />

C11 C5 C6 C7 -98.17(19) . . . . ?<br />

C4 C5 C6 C7 30.8(2) . . . . ?<br />

C11 C5 C6 O2 81.72(18) . . . . ?<br />

C4 C5 C6 O2 -149.32(14) . . . . ?<br />

O2 C6 C7 C8 176.77(16) . . . . ?<br />

C5 C6 C7 C8 -3.4(3) . . . . ?<br />

C6 C7 C8 C9 -12.4(3) . . . . ?<br />

C7 C8 C9 C4 -3.7(3) . . . . ?<br />

C1 C4 C9 C8 156.95(17) . . . . ?<br />

C10 C4 C9 C8 -86.9(2) . . . . ?<br />

C5 C4 C9 C8 32.3(2) . . . . ?<br />

C6 C5 C11 C12 66.75(19) . . . . ?<br />

C4 C5 C11 C12 -58.95(19) . . . . ?<br />

C6 C5 C11 C13 -59.9(2) . . . . ?<br />

C4 C5 C11 C13 174.44(15) . . . . ?<br />

N1 C2 C15 C16 -35.3(2) . . . . ?<br />

C3 C2 C15 C16 83.3(2) . . . . ?<br />

N1 C2 C15 C20 147.76(16) . . . . ?<br />

C3 C2 C15 C20 -93.66(19) . . . . ?<br />

C20 C15 C16 C17 -0.1(3) . . . . ?<br />

C2 C15 C16 C17 -177.07(17) . . . . ?<br />

C15 C16 C17 C18 0.2(3) . . . . ?<br />

C16 C17 C18 C19 0.2(3) . . . . ?<br />

304


C17 C18 C19 C20 -0.8(3) . . . . ?<br />

C18 C19 C20 C15 1.0(3) . . . . ?<br />

C16 C15 C20 C19 -0.5(3) . . . . ?<br />

C2 C15 C20 C19 176.55(17) . . . . ?<br />

O1 C3 C21 C22 151.21(16) . . . . ?<br />

C2 C3 C21 C22 -93.0(2) . . . . ?<br />

O1 C3 C21 C26 -33.8(2) . . . . ?<br />

C2 C3 C21 C26 82.0(2) . . . . ?<br />

C26 C21 C22 C23 -1.5(3) . . . . ?<br />

C3 C21 C22 C23 173.60(18) . . . . ?<br />

C21 C22 C23 C24 1.0(3) . . . . ?<br />

C22 C23 C24 C25 0.3(3) . . . . ?<br />

C23 C24 C25 C26 -1.1(3) . . . . ?<br />

C24 C25 C26 C21 0.5(3) . . . . ?<br />

C22 C21 C26 C25 0.8(3) . . . . ?<br />

C3 C21 C26 C25 -174.24(17) . . . . ?<br />

_diffrn_measured_fraction_theta_max 0.991<br />

_diffrn_reflns_theta_full 26.37<br />

_diffrn_measured_fraction_theta_full 0.991<br />

_refine_diff_density_max 0.245<br />

_refine_diff_density_min -0.155<br />

_refine_diff_density_rms 0.035<br />

305


c. Compound 213<br />

Ph<br />

O<br />

N<br />

Ph<br />

Me<br />

OH<br />

213<br />

OH<br />

Identification code s2494m<br />

Empirical formula C25 H29 N O3<br />

Formula weight 391.49<br />

Temperature<br />

100(2) K<br />

Wavelength<br />

0.71073 A<br />

Crystal system, space group Triclinic, P1<br />

Unit cell dimensions a = 7.8190(18) A alpha = 88.315(4) deg.<br />

b = 10.875(3) A beta = 83.873(5) deg.<br />

c = 12.833(3) A gamma = 85.179(4) deg.<br />

Volume<br />

1080.9(4) A^3<br />

Z, Calculated density 2, 1.203 Mg/m^3<br />

Absorption coefficient 0.078 mm^-1<br />

F(000) 420<br />

Crystal size<br />

0.40 x 0.20 x 0.06 mm<br />

<strong>The</strong>ta range for data collection 1.60 <strong>to</strong> 28.26 deg.<br />

Limiting indices -9


Final R indices [I>2sigma(I)] R1 = 0.0574, wR2 = 0.0998<br />

R indices (all data) R1 = 0.1426, wR2 = 0.1223<br />

Absolute structure parameter 0(10)<br />

Largest diff. peak and hole 0.242 and -0.242 e.A^-3<br />

_audit_creation_method SHELXL-97<br />

_chemical_name_systematic<br />

_chemical_name_common ?<br />

_chemical_melting_point ?<br />

_chemical_formula_moiety ?<br />

_chemical_formula_sum<br />

'C25 H29 N O3'<br />

_chemical_formula_weight 391.49<br />

loop_<br />

_a<strong>to</strong>m_type_symbol<br />

_a<strong>to</strong>m_type_description<br />

_a<strong>to</strong>m_type_scat_dispersion_real<br />

_a<strong>to</strong>m_type_scat_dispersion_imag<br />

_a<strong>to</strong>m_type_scat_source<br />

'C' 'C' 0.0033 0.0000<br />

'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'<br />

'H' 'H' 0.0000 0.0000<br />

'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'<br />

'N' 'N' 0.0061 0.0000<br />

'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'<br />

'O' 'O' 0.0106 0.0000<br />

'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'<br />

_symmetry_cell_setting Triclinic<br />

_symmetry_space_group_name_H-M P1<br />

loop_<br />

_symmetry_equiv_pos_as_xyz<br />

'x, y, z'<br />

_cell_length_a 7.8190(18)<br />

_cell_length_b 10.875(3)<br />

_cell_length_c 12.833(3)<br />

_cell_angle_alpha 88.315(4)<br />

_cell_angle_beta 83.873(5)<br />

_cell_angle_gamma 85.179(4)<br />

307


_cell_volume 1080.9(4)<br />

_cell_formula_units_Z 2<br />

_cell_measurement_temperature 100(2)<br />

_cell_measurement_reflns_used 540<br />

_cell_measurement_theta_min 2.4375<br />

_cell_measurement_theta_max 19.2385<br />

_exptl_crystal_description block<br />

_exptl_crystal_colour white<br />

_exptl_crystal_size_max 0.40<br />

_exptl_crystal_size_mid 0.20<br />

_exptl_crystal_size_min 0.06<br />

_exptl_crystal_density_meas 0<br />

_exptl_crystal_density_diffrn 1.203<br />

_exptl_crystal_density_method 'not measured'<br />

_exptl_crystal_F_000 420<br />

_exptl_absorpt_coefficient_mu 0.078<br />

_exptl_absorpt_correction_type none<br />

_exptl_absorpt_correction_T_min 0.9694<br />

_exptl_absorpt_correction_T_max 0.9953<br />

_exptl_absorpt_process_details ?<br />

_exptl_special_details<br />

_diffrn_ambient_temperature 100(2)<br />

_diffrn_radiation_wavelength 0.71073<br />

_diffrn_radiation_type MoK\a<br />

_diffrn_radiation_source 'fine-focus sealed tube'<br />

_diffrn_radiation_monochroma<strong>to</strong>r graphite<br />

_diffrn_measurement_device_type 'CCD area detec<strong>to</strong>r'<br />

_diffrn_measurement_method 'phi and omega scans'<br />

_diffrn_detec<strong>to</strong>r_area_resol_mean ?<br />

_diffrn_standards_number ?<br />

_diffrn_standards_interval_count ?<br />

_diffrn_standards_interval_time ?<br />

_diffrn_standards_decay_% ?<br />

_diffrn_reflns_number 6697<br />

_diffrn_reflns_av_R_equivalents 0.0699<br />

_diffrn_reflns_av_sigmaI/netI 0.2619<br />

_diffrn_reflns_limit_h_min -9<br />

_diffrn_reflns_limit_h_max 10<br />

308


_diffrn_reflns_limit_k_min -11<br />

_diffrn_reflns_limit_k_max 14<br />

_diffrn_reflns_limit_l_min -17<br />

_diffrn_reflns_limit_l_max 15<br />

_diffrn_reflns_theta_min 1.60<br />

_diffrn_reflns_theta_max 28.26<br />

_reflns_number_<strong>to</strong>tal 4736<br />

_reflns_number_gt 1921<br />

_reflns_threshold_expression >2sigma(I)<br />

_computing_data_collection 'Bruker SMART'<br />

_computing_cell_refinement 'Bruker SMART'<br />

_computing_data_reduction 'Bruker SAINT'<br />

_computing_structure_solution 'SIR2004 (Burla et al, 2005)'<br />

_computing_structure_refinement 'SHELXL-97 (Sheldrick, 1997)'<br />

_computing_molecular_graphics 'Bruker SHELXTL'<br />

_computing_publication_material 'Bruker SHELXTL'<br />

_refine_special_details<br />

Refinement of F^2^ against ALL reflections. <strong>The</strong> weighted R-fac<strong>to</strong>r wR and<br />

goodness of fit S are based on F^2^, conventional R-fac<strong>to</strong>rs R are based<br />

on F, with F set <strong>to</strong> zero for negative F^2^. <strong>The</strong> threshold expression of<br />

F^2^ > 2sigma(F^2^) is used only for calculating R-fac<strong>to</strong>rs(gt) etc. and is<br />

not relevant <strong>to</strong> the choice of reflections for refinement. R-fac<strong>to</strong>rs based<br />

on F^2^ are statistically about twice as large as those based on F, and R-<br />

fac<strong>to</strong>rs based on ALL data will be even larger.<br />

_refine_ls_structure_fac<strong>to</strong>r_coef Fsqd<br />

_refine_ls_matrix_type full<br />

_refine_ls_weighting_scheme calc<br />

_refine_ls_weighting_details<br />

'calc w=1/[\s^2^(Fo^2^)+(0.0289P)^2^+0.0000P] where P=(Fo^2^+2Fc^2^)/3'<br />

_a<strong>to</strong>m_sites_solution_primary direct<br />

_a<strong>to</strong>m_sites_solution_secondary difmap<br />

_a<strong>to</strong>m_sites_solution_hydrogens geom<br />

_refine_ls_hydrogen_treatment constr<br />

_refine_ls_extinction_method none<br />

_refine_ls_extinction_coef ?<br />

_refine_ls_abs_structure_details<br />

'Flack H D (1983), Acta Cryst. A39, 876-881'<br />

_refine_ls_abs_structure_Flack 0(10)<br />

309


_refine_ls_number_reflns 4736<br />

_refine_ls_number_parameters 533<br />

_refine_ls_number_restraints 3<br />

_refine_ls_R_fac<strong>to</strong>r_all 0.1426<br />

_refine_ls_R_fac<strong>to</strong>r_gt 0.0574<br />

_refine_ls_wR_fac<strong>to</strong>r_ref 0.1223<br />

_refine_ls_wR_fac<strong>to</strong>r_gt 0.0998<br />

_refine_ls_goodness_of_fit_ref 0.718<br />

_refine_ls_restrained_S_all 0.718<br />

_refine_ls_shift/su_max 0.000<br />

_refine_ls_shift/su_mean 0.000<br />

loop_<br />

_a<strong>to</strong>m_site_label<br />

_a<strong>to</strong>m_site_type_symbol<br />

_a<strong>to</strong>m_site_fract_x<br />

_a<strong>to</strong>m_site_fract_y<br />

_a<strong>to</strong>m_site_fract_z<br />

_a<strong>to</strong>m_site_U_iso_or_equiv<br />

_a<strong>to</strong>m_site_adp_type<br />

_a<strong>to</strong>m_site_occupancy<br />

_a<strong>to</strong>m_site_symmetry_multiplicity<br />

_a<strong>to</strong>m_site_calc_flag<br />

_a<strong>to</strong>m_site_refinement_flags<br />

_a<strong>to</strong>m_site_disorder_assembly<br />

_a<strong>to</strong>m_site_disorder_group<br />

C1 C 0.8582(9) 0.1544(6) 0.0767(5) 0.0230(17) Uani 1 1 d . . .<br />

C2 C 0.7980(9) 0.3587(6) 0.0652(5) 0.0245(17) Uani 1 1 d . . .<br />

H2 H 0.6816 0.3882 0.0996 0.029 Uiso 1 1 calc R . .<br />

C3 C 0.9199(9) 0.3238(6) 0.1490(5) 0.0191(16) Uani 1 1 d . . .<br />

H3 H 1.0373 0.3467 0.1206 0.023 Uiso 1 1 calc R . .<br />

C4 C 0.8559(8) 0.0209(6) 0.0415(5) 0.0206(17) Uani 1 1 d . . .<br />

C5 C 0.6691(8) -0.0238(6) 0.0490(5) 0.0186(16) Uani 1 1 d . . .<br />

H5 H 0.6867 -0.1098 0.0221 0.022 Uiso 1 1 calc R . .<br />

C6 C 0.6003(8) -0.0398(6) 0.1629(5) 0.0160(15) Uani 1 1 d . . .<br />

H6 H 0.6043 0.0394 0.1998 0.019 Uiso 1 1 calc R . .<br />

C7 C 0.7098(8) -0.1406(6) 0.2145(5) 0.0184(16) Uani 1 1 d . . .<br />

H7 H 0.6778 -0.2224 0.1926 0.022 Uiso 1 1 calc R . .<br />

C8 C 0.8984(9) -0.1335(6) 0.1865(5) 0.0200(16) Uani 1 1 d . . .<br />

310


H8 H 0.9757 -0.1848 0.2244 0.024 Uiso 1 1 calc R . .<br />

C9 C 0.9635(9) -0.0603(6) 0.1125(5) 0.0229(17) Uani 1 1 d . . .<br />

H9 H 1.0853 -0.0579 0.1025 0.027 Uiso 1 1 calc R . .<br />

C10 C 0.9453(9) 0.0119(7) -0.0695(5) 0.0279(18) Uani 1 1 d . . .<br />

H10A H 1.0618 0.0393 -0.0712 0.042 Uiso 1 1 calc R . .<br />

H10B H 0.8791 0.0645 -0.1168 0.042 Uiso 1 1 calc R . .<br />

H10C H 0.9525 -0.0739 -0.0920 0.042 Uiso 1 1 calc R . .<br />

C11 C 0.5454(9) 0.0443(6) -0.0236(5) 0.0223(17) Uani 1 1 d . . .<br />

H11 H 0.6190 0.0828 -0.0822 0.027 Uiso 1 1 calc R . .<br />

C12 C 0.4243(9) 0.1496(6) 0.0289(5) 0.0264(18) Uani 1 1 d . . .<br />

H12A H 0.3248 0.1149 0.0686 0.040 Uiso 1 1 calc R . .<br />

H12B H 0.3842 0.2073 -0.0251 0.040 Uiso 1 1 calc R . .<br />

H12C H 0.4870 0.1934 0.0765 0.040 Uiso 1 1 calc R . .<br />

C13 C 0.4397(9) -0.0432(7) -0.0725(5) 0.0259(18) Uani 1 1 d . . .<br />

H13A H 0.5167 -0.1032 -0.1143 0.039 Uiso 1 1 calc R . .<br />

H13B H 0.3629 0.0033 -0.1178 0.039 Uiso 1 1 calc R . .<br />

H13C H 0.3707 -0.0868 -0.0173 0.039 Uiso 1 1 calc R . .<br />

C14 C 0.8597(9) 0.4533(6) -0.0172(5) 0.0249(17) Uani 1 1 d . . .<br />

C15 C 0.7715(9) 0.5669(6) -0.0271(5) 0.0305(19) Uani 1 1 d . . .<br />

H15 H 0.6688 0.5886 0.0173 0.037 Uiso 1 1 calc R . .<br />

C16 C 0.8362(11) 0.6506(7) -0.1041(6) 0.042(2) Uani 1 1 d . . .<br />

H16 H 0.7752 0.7291 -0.1119 0.051 Uiso 1 1 calc R . .<br />

C17 C 0.9843(11) 0.6218(7) -0.1680(6) 0.042(2) Uani 1 1 d . . .<br />

H17 H 1.0246 0.6798 -0.2198 0.051 Uiso 1 1 calc R . .<br />

C18 C 1.0751(11) 0.5093(7) -0.1576(6) 0.046(2) Uani 1 1 d . . .<br />

H18 H 1.1790 0.4889 -0.2012 0.055 Uiso 1 1 calc R . .<br />

C19 C 1.0103(10) 0.4241(7) -0.0804(5) 0.035(2) Uani 1 1 d . . .<br />

H19 H 1.0717 0.3459 -0.0722 0.042 Uiso 1 1 calc R . .<br />

C20 C 0.8762(8) 0.3833(6) 0.2535(5) 0.0191(16) Uani 1 1 d . . .<br />

C21 C 0.9035(8) 0.5081(6) 0.2635(5) 0.0257(18) Uani 1 1 d . . .<br />

H21 H 0.9387 0.5557 0.2029 0.031 Uiso 1 1 calc R . .<br />

C22 C 0.8799(9) 0.5617(6) 0.3595(5) 0.0262(18) Uani 1 1 d . . .<br />

H22 H 0.8978 0.6465 0.3647 0.031 Uiso 1 1 calc R . .<br />

C23 C 0.8302(9) 0.4941(7) 0.4495(6) 0.0283(19) Uani 1 1 d . . .<br />

H23 H 0.8204 0.5310 0.5163 0.034 Uiso 1 1 calc R . .<br />

C24 C 0.7947(9) 0.3712(6) 0.4406(5) 0.0270(18) Uani 1 1 d . . .<br />

H24 H 0.7539 0.3250 0.5008 0.032 Uiso 1 1 calc R . .<br />

C25 C 0.8199(8) 0.3175(6) 0.3424(5) 0.0234(17) Uani 1 1 d . . .<br />

311


H25 H 0.7979 0.2335 0.3365 0.028 Uiso 1 1 calc R . .<br />

C26 C 0.2928(9) 0.7886(6) 0.5233(5) 0.0224(17) Uani 1 1 d . . .<br />

C27 C 0.2850(9) 0.5816(6) 0.5312(5) 0.0236(17) Uani 1 1 d . . .<br />

H27 H 0.1826 0.5452 0.5079 0.028 Uiso 1 1 calc R . .<br />

C28 C 0.4031(9) 0.6214(6) 0.4357(5) 0.0210(17) Uani 1 1 d . . .<br />

H28 H 0.5243 0.5916 0.4473 0.025 Uiso 1 1 calc R . .<br />

C29 C 0.2556(8) 0.9190(6) 0.5639(5) 0.0180(16) Uani 1 1 d . . .<br />

C30 C 0.0682(8) 0.9745(6) 0.5535(5) 0.0140(14) Uani 1 1 d . . .<br />

H30 H 0.0647 1.0600 0.5807 0.017 Uiso 1 1 calc R . .<br />

C31 C 0.0448(9) 0.9934(6) 0.4366(5) 0.0225(17) Uani 1 1 d . . .<br />

H31 H 0.0790 0.9140 0.3996 0.027 Uiso 1 1 calc R . .<br />

C32 C 0.1555(9) 1.0903(6) 0.3893(5) 0.0225(17) Uani 1 1 d . . .<br />

H32 H 0.1010 1.1732 0.4115 0.027 Uiso 1 1 calc R . .<br />

C33 C 0.3330(9) 1.0742(6) 0.4230(5) 0.0201(16) Uani 1 1 d . . .<br />

H33 H 0.4182 1.1217 0.3870 0.024 Uiso 1 1 calc R . .<br />

C34 C 0.3810(8) 0.9986(6) 0.4995(5) 0.0198(16) Uani 1 1 d . . .<br />

H34 H 0.4976 0.9939 0.5147 0.024 Uiso 1 1 calc R . .<br />

C35 C 0.2973(9) 0.9194(6) 0.6791(5) 0.0254(18) Uani 1 1 d . . .<br />

H35A H 0.2327 0.8579 0.7203 0.038 Uiso 1 1 calc R . .<br />

H35B H 0.2642 1.0014 0.7081 0.038 Uiso 1 1 calc R . .<br />

H35C H 0.4213 0.8992 0.6818 0.038 Uiso 1 1 calc R . .<br />

C36 C -0.0775(8) 0.9141(6) 0.6224(5) 0.0227(17) Uani 1 1 d . . .<br />

H36 H -0.0242 0.8779 0.6851 0.027 Uiso 1 1 calc R . .<br />

C37 C -0.1550(9) 0.8070(6) 0.5732(6) 0.0305(19) Uani 1 1 d . . .<br />

H37A H -0.2353 0.8402 0.5238 0.046 Uiso 1 1 calc R . .<br />

H37B H -0.2169 0.7587 0.6285 0.046 Uiso 1 1 calc R . .<br />

H37C H -0.0622 0.7539 0.5360 0.046 Uiso 1 1 calc R . .<br />

C38 C -0.2183(8) 1.0112(6) 0.6644(5) 0.0266(18) Uani 1 1 d . . .<br />

H38A H -0.1674 1.0721 0.7038 0.040 Uiso 1 1 calc R . .<br />

H38B H -0.3062 0.9713 0.7106 0.040 Uiso 1 1 calc R . .<br />

H38C H -0.2716 1.0526 0.6056 0.040 Uiso 1 1 calc R . .<br />

C39 C 0.3716(9) 0.4925(6) 0.6067(5) 0.0237(18) Uani 1 1 d . . .<br />

C40 C 0.4876(9) 0.5309(7) 0.6681(5) 0.0303(19) Uani 1 1 d . . .<br />

H40 H 0.5105 0.6154 0.6660 0.036 Uiso 1 1 calc R . .<br />

C41 C 0.5743(10) 0.4474(8) 0.7348(6) 0.043(2) Uani 1 1 d . . .<br />

H41 H 0.6574 0.4743 0.7761 0.052 Uiso 1 1 calc R . .<br />

C42 C 0.5353(12) 0.3248(8) 0.7387(7) 0.053(3) Uani 1 1 d . . .<br />

H42 H 0.5905 0.2676 0.7842 0.064 Uiso 1 1 calc R . .<br />

312


C43 C 0.4196(12) 0.2863(7) 0.6783(6) 0.044(2) Uani 1 1 d . . .<br />

H43 H 0.3968 0.2018 0.6806 0.053 Uiso 1 1 calc R . .<br />

C44 C 0.3335(11) 0.3685(7) 0.6129(6) 0.042(2) Uani 1 1 d . . .<br />

H44 H 0.2495 0.3409 0.5726 0.050 Uiso 1 1 calc R . .<br />

C45 C 0.3663(9) 0.5719(6) 0.3329(5) 0.0224(17) Uani 1 1 d . . .<br />

C46 C 0.3683(8) 0.4458(6) 0.3219(6) 0.0251(18) Uani 1 1 d . . .<br />

H46 H 0.3852 0.3919 0.3802 0.030 Uiso 1 1 calc R . .<br />

C47 C 0.3459(9) 0.3984(7) 0.2269(6) 0.0287(19) Uani 1 1 d . . .<br />

H47 H 0.3464 0.3115 0.2211 0.034 Uiso 1 1 calc R . .<br />

C48 C 0.3228(9) 0.4721(7) 0.1401(6) 0.0309(19) Uani 1 1 d . . .<br />

H48 H 0.3096 0.4371 0.0747 0.037 Uiso 1 1 calc R . .<br />

C49 C 0.3193(9) 0.6005(7) 0.1504(5) 0.0275(18) Uani 1 1 d . . .<br />

H49 H 0.3049 0.6541 0.0916 0.033 Uiso 1 1 calc R . .<br />

C50 C 0.3370(8) 0.6482(6) 0.2479(5) 0.0248(17) Uani 1 1 d . . .<br />

H50 H 0.3289 0.7352 0.2560 0.030 Uiso 1 1 calc R . .<br />

N1 N 0.9268(7) 0.1878(5) 0.1565(4) 0.0210(14) Uani 1 1 d . . .<br />

N2 N 0.3884(7) 0.7580(5) 0.4393(4) 0.0218(14) Uani 1 1 d . . .<br />

O1 O 0.7871(6) 0.2416(4) 0.0124(3) 0.0259(12) Uani 1 1 d . . .<br />

O2 O 0.4253(6) -0.0749(4) 0.1738(4) 0.0214(11) Uani 1 1 d . . .<br />

H2A H 0.3566 -0.0113 0.1727 0.032 Uiso 1 1 calc R . .<br />

O3 O 0.6828(5) -0.1355(4) 0.3286(3) 0.0199(11) Uani 1 1 d . . .<br />

H3A H 0.5795 -0.1467 0.3490 0.030 Uiso 1 1 calc R . .<br />

O4 O 0.2293(6) 0.6976(4) 0.5865(3) 0.0245(12) Uani 1 1 d . . .<br />

O5 O -0.1323(5) 1.0327(4) 0.4216(3) 0.0223(12) Uani 1 1 d . . .<br />

H5A H -0.1509 1.0172 0.3602 0.033 Uiso 1 1 calc R . .<br />

O6 O 0.1779(5) 1.0876(4) 0.2767(3) 0.0213(11) Uani 1 1 d . . .<br />

H6A H 0.2834 1.0747 0.2560 0.032 Uiso 1 1 calc R . .<br />

loop_<br />

_a<strong>to</strong>m_site_aniso_label<br />

_a<strong>to</strong>m_site_aniso_U_11<br />

_a<strong>to</strong>m_site_aniso_U_22<br />

_a<strong>to</strong>m_site_aniso_U_33<br />

_a<strong>to</strong>m_site_aniso_U_23<br />

_a<strong>to</strong>m_site_aniso_U_13<br />

_a<strong>to</strong>m_site_aniso_U_12<br />

C1 0.020(4) 0.026(4) 0.023(4) 0.013(3) -0.003(3) -0.003(3)<br />

C2 0.027(4) 0.021(4) 0.027(4) 0.008(3) -0.007(3) -0.007(3)<br />

C3 0.018(4) 0.021(4) 0.019(4) -0.001(3) -0.003(3) -0.007(3)<br />

313


C4 0.025(4) 0.019(4) 0.018(4) 0.001(3) -0.004(3) -0.005(3)<br />

C5 0.025(4) 0.010(4) 0.023(4) -0.001(3) -0.007(3) -0.005(3)<br />

C6 0.018(4) 0.015(4) 0.015(4) -0.005(3) 0.000(3) -0.003(3)<br />

C7 0.029(4) 0.006(3) 0.021(4) -0.003(3) -0.003(3) 0.000(3)<br />

C8 0.022(4) 0.015(4) 0.024(4) -0.003(3) -0.008(3) 0.001(3)<br />

C9 0.018(4) 0.016(4) 0.035(5) -0.004(3) -0.008(4) 0.006(3)<br />

C10 0.024(4) 0.030(5) 0.029(4) 0.006(4) 0.000(3) -0.003(3)<br />

C11 0.030(4) 0.016(4) 0.022(4) 0.008(3) -0.008(3) -0.002(3)<br />

C12 0.031(4) 0.026(4) 0.021(4) 0.006(3) -0.003(3) 0.001(4)<br />

C13 0.022(4) 0.034(5) 0.021(4) -0.006(3) -0.001(3) 0.002(3)<br />

C14 0.032(5) 0.020(4) 0.024(4) 0.000(3) -0.003(4) -0.008(3)<br />

C15 0.037(5) 0.022(4) 0.030(4) 0.004(4) -0.001(4) 0.005(4)<br />

C16 0.067(7) 0.007(4) 0.050(6) 0.006(4) -0.006(5) 0.005(4)<br />

C17 0.056(6) 0.028(5) 0.038(5) 0.014(4) 0.016(5) -0.009(4)<br />

C18 0.048(6) 0.031(5) 0.054(6) 0.010(4) 0.012(5) -0.004(4)<br />

C19 0.052(6) 0.019(4) 0.027(4) 0.011(3) 0.013(4) 0.012(4)<br />

C20 0.017(4) 0.018(4) 0.023(4) 0.006(3) -0.006(3) -0.004(3)<br />

C21 0.023(4) 0.025(5) 0.028(5) 0.003(4) 0.003(3) -0.002(3)<br />

C22 0.028(5) 0.013(4) 0.036(5) 0.000(4) -0.002(4) 0.004(3)<br />

C23 0.022(4) 0.029(5) 0.035(5) -0.004(4) -0.010(4) 0.001(4)<br />

C24 0.028(5) 0.023(4) 0.027(4) 0.007(3) 0.002(4) 0.002(3)<br />

C25 0.028(4) 0.018(4) 0.025(4) 0.007(3) -0.004(3) -0.002(3)<br />

C26 0.025(4) 0.019(4) 0.023(4) 0.006(3) -0.002(3) -0.001(3)<br />

C27 0.029(4) 0.015(4) 0.026(4) 0.000(3) 0.002(3) -0.002(3)<br />

C28 0.027(4) 0.012(4) 0.023(4) 0.004(3) 0.000(3) 0.001(3)<br />

C29 0.030(4) 0.010(4) 0.014(4) 0.006(3) 0.005(3) -0.008(3)<br />

C30 0.015(4) 0.013(3) 0.015(4) 0.000(3) -0.005(3) -0.002(3)<br />

C31 0.028(4) 0.012(4) 0.028(4) -0.008(3) -0.002(3) 0.000(3)<br />

C32 0.025(4) 0.021(4) 0.022(4) -0.003(3) -0.002(3) -0.002(3)<br />

C33 0.024(4) 0.020(4) 0.017(4) -0.004(3) 0.002(3) -0.009(3)<br />

C34 0.021(4) 0.012(4) 0.028(4) -0.008(3) -0.013(3) 0.000(3)<br />

C35 0.028(5) 0.020(4) 0.029(4) 0.001(3) -0.006(4) -0.002(3)<br />

C36 0.025(4) 0.013(4) 0.030(4) 0.003(3) -0.004(3) 0.000(3)<br />

C37 0.034(5) 0.022(4) 0.036(5) 0.013(4) -0.007(4) -0.004(4)<br />

C38 0.019(4) 0.029(4) 0.034(4) -0.007(4) -0.006(3) -0.002(3)<br />

C39 0.038(5) 0.008(4) 0.023(4) 0.008(3) 0.002(4) -0.003(3)<br />

C40 0.037(5) 0.025(4) 0.030(5) 0.006(4) -0.011(4) 0.001(4)<br />

C41 0.045(6) 0.051(6) 0.031(5) 0.015(4) -0.004(4) 0.004(5)<br />

314


C42 0.072(7) 0.028(5) 0.057(6) 0.013(5) -0.011(5) 0.009(5)<br />

C43 0.071(7) 0.010(4) 0.050(6) 0.002(4) 0.001(5) 0.000(4)<br />

C44 0.065(6) 0.030(5) 0.031(5) 0.000(4) -0.003(4) -0.011(4)<br />

C45 0.023(4) 0.018(4) 0.024(4) -0.001(3) 0.003(3) -0.002(3)<br />

C46 0.021(4) 0.021(4) 0.033(5) 0.006(4) -0.004(4) -0.003(3)<br />

C47 0.034(5) 0.016(4) 0.037(5) -0.008(4) -0.003(4) -0.001(3)<br />

C48 0.020(4) 0.042(5) 0.031(5) -0.013(4) 0.003(4) -0.011(4)<br />

C49 0.029(5) 0.033(5) 0.020(4) 0.003(4) 0.006(3) -0.011(4)<br />

C50 0.018(4) 0.021(4) 0.034(4) 0.002(4) 0.004(3) -0.008(3)<br />

N1 0.026(4) 0.018(3) 0.019(3) 0.005(3) 0.001(3) -0.003(3)<br />

N2 0.029(4) 0.015(3) 0.021(3) 0.000(3) -0.003(3) -0.003(3)<br />

O1 0.038(3) 0.015(3) 0.027(3) 0.007(2) -0.011(2) -0.007(2)<br />

O2 0.020(3) 0.016(3) 0.029(3) -0.002(2) -0.004(2) -0.004(2)<br />

O3 0.021(3) 0.019(3) 0.020(3) 0.006(2) 0.000(2) -0.008(2)<br />

O4 0.026(3) 0.015(3) 0.031(3) 0.005(2) 0.003(2) 0.001(2)<br />

O5 0.018(3) 0.021(3) 0.028(3) 0.001(2) -0.008(2) 0.001(2)<br />

O6 0.018(3) 0.021(3) 0.024(3) 0.000(2) 0.002(2) -0.001(2) _geom_special_details<br />

All esds (except the esd in the dihedral angle between two l.s. planes)<br />

are estimated using the full covariance matrix. <strong>The</strong> cell esds are taken<br />

in<strong>to</strong> account individually in the estimation of esds in distances, angles<br />

and <strong>to</strong>rsion angles; correlations between esds in cell parameters are only<br />

used when they are defined by crystal symmetry. An approximate (isotropic)<br />

treatment of cell esds is used for estimating esds involving l.s. planes.<br />

315


loop_<br />

_geom_bond_a<strong>to</strong>m_site_label_1<br />

_geom_bond_a<strong>to</strong>m_site_label_2<br />

_geom_bond_distance<br />

_geom_bond_site_symmetry_2<br />

_geom_bond_publ_flag<br />

C1 N1 1.281(8) . ?<br />

C1 O1 1.361(7) . ?<br />

C1 C4 1.535(9) . ?<br />

C2 O1 1.474(7) . ?<br />

C2 C14 1.523(9) . ?<br />

C2 C3 1.530(8) . ?<br />

C2 H2 1.0000 . ?<br />

C3 N1 1.476(8) . ?<br />

C3 C20 1.501(9) . ?<br />

C3 H3 1.0000 . ?<br />

C4 C9 1.519(8) . ?<br />

C4 C10 1.521(9) . ?<br />

C4 C5 1.570(9) . ?<br />

C5 C6 1.513(8) . ?<br />

C5 C11 1.544(8) . ?<br />

C5 H5 1.0000 . ?<br />

C6 O2 1.443(7) . ?<br />

C6 C7 1.514(8) . ?<br />

C6 H6 1.0000 . ?<br />

C7 O3 1.459(6) . ?<br />

C7 C8 1.488(9) . ?<br />

C7 H7 1.0000 . ?<br />

C8 C9 1.310(9) . ?<br />

C8 H8 0.9500 . ?<br />

C9 H9 0.9500 . ?<br />

C10 H10A 0.9800 . ?<br />

C10 H10B 0.9800 . ?<br />

C10 H10C 0.9800 . ?<br />

C11 C13 1.504(9) . ?<br />

C11 C12 1.546(8) . ?<br />

C11 H11 1.0000 . ?<br />

C12 H12A 0.9800 . ?<br />

C12 H12B 0.9800 . ?<br />

C12 H12C 0.9800 . ?<br />

C13 H13A 0.9800 . ?<br />

C13 H13B 0.9800 . ?<br />

C13 H13C 0.9800 . ?<br />

C14 C15 1.373(9) . ?<br />

C14 C19 1.376(9) . ?<br />

C15 C16 1.407(10) . ?<br />

C15 H15 0.9500 . ?<br />

C16 C17 1.365(10) . ?<br />

C16 H16 0.9500 . ?<br />

C17 C18 1.372(10) . ?<br />

C17 H17 0.9500 . ?<br />

C18 C19 1.420(10) . ?<br />

C18 H18 0.9500 . ?<br />

C19 H19 0.9500 . ?<br />

C20 C25 1.381(8) . ?<br />

C20 C21 1.402(9) . ?<br />

C21 C22 1.367(9) . ?<br />

C21 H21 0.9500 . ?<br />

C22 C23 1.388(9) . ?<br />

C22 H22 0.9500 . ?<br />

C23 C24 1.398(9) . ?<br />

C23 H23 0.9500 . ?<br />

C24 C25 1.393(9) . ?<br />

C24 H24 0.9500 . ?<br />

C25 H25 0.9500 . ?<br />

C26 N2 1.280(8) . ?<br />

C26 O4 1.353(8) . ?<br />

C26 C29 1.520(9) . ?<br />

C27 O4 1.477(7) . ?<br />

C27 C39 1.519(9) . ?<br />

C27 C28 1.529(9) . ?<br />

C27 H27 1.0000 . ?<br />

C28 N2 1.482(8) . ?<br />

C28 C45 1.504(9) . ?<br />

C28 H28 1.0000 . ?<br />

C29 C34 1.523(9) . ?<br />

316


C29 C35 1.548(8) . ?<br />

C29 C30 1.554(8) . ?<br />

C30 C31 1.537(8) . ?<br />

C30 C36 1.546(9) . ?<br />

C30 H30 1.0000 . ?<br />

C31 O5 1.446(7) . ?<br />

C31 C32 1.494(9) . ?<br />

C31 H31 1.0000 . ?<br />

C32 O6 1.438(7) . ?<br />

C32 C33 1.493(9) . ?<br />

C32 H32 1.0000 . ?<br />

C33 C34 1.326(8) . ?<br />

C33 H33 0.9500 . ?<br />

C34 H34 0.9500 . ?<br />

C35 H35A 0.9800 . ?<br />

C35 H35B 0.9800 . ?<br />

C35 H35C 0.9800 . ?<br />

C36 C38 1.526(8) . ?<br />

C36 C37 1.538(9) . ?<br />

C36 H36 1.0000 . ?<br />

C37 H37A 0.9800 . ?<br />

C37 H37B 0.9800 . ?<br />

C37 H37C 0.9800 . ?<br />

C38 H38A 0.9800 . ?<br />

C38 H38B 0.9800 . ?<br />

C38 H38C 0.9800 . ?<br />

C39 C40 1.361(9) . ?<br />

C39 C44 1.404(10) . ?<br />

C40 C41 1.412(9) . ?<br />

C40 H40 0.9500 . ?<br />

C41 C42 1.391(11) . ?<br />

C41 H41 0.9500 . ?<br />

C42 C43 1.351(11) . ?<br />

C42 H42 0.9500 . ?<br />

C43 C44 1.391(10) . ?<br />

C43 H43 0.9500 . ?<br />

C44 H44 0.9500 . ?<br />

C45 C50 1.378(9) . ?<br />

C45 C46 1.381(9) . ?<br />

C46 C47 1.371(9) . ?<br />

C46 H46 0.9500 . ?<br />

C47 C48 1.372(10) . ?<br />

C47 H47 0.9500 . ?<br />

C48 C49 1.405(10) . ?<br />

C48 H48 0.9500 . ?<br />

C49 C50 1.394(9) . ?<br />

C49 H49 0.9500 . ?<br />

C50 H50 0.9500 . ?<br />

O2 H2A 0.8400 . ?<br />

O3 H3A 0.8400 . ?<br />

O5 H5A 0.8400 . ?<br />

O6 H6A 0.8400 . ?<br />

loop_<br />

_geom_angle_a<strong>to</strong>m_site_label_1<br />

_geom_angle_a<strong>to</strong>m_site_label_2<br />

_geom_angle_a<strong>to</strong>m_site_label_3<br />

_geom_angle<br />

_geom_angle_site_symmetry_1<br />

_geom_angle_site_symmetry_3<br />

_geom_angle_publ_flag<br />

N1 C1 O1 119.6(6) . . ?<br />

N1 C1 C4 125.5(6) . . ?<br />

O1 C1 C4 114.9(5) . . ?<br />

O1 C2 C14 108.1(5) . . ?<br />

O1 C2 C3 103.8(5) . . ?<br />

C14 C2 C3 115.7(6) . . ?<br />

O1 C2 H2 109.7 . . ?<br />

C14 C2 H2 109.7 . . ?<br />

C3 C2 H2 109.7 . . ?<br />

N1 C3 C20 112.7(5) . . ?<br />

N1 C3 C2 104.5(5) . . ?<br />

C20 C3 C2 116.8(5) . . ?<br />

N1 C3 H3 107.5 . . ?<br />

C20 C3 H3 107.5 . . ?<br />

C2 C3 H3 107.5 . . ?<br />

C9 C4 C10 107.8(5) . . ?<br />

317


C9 C4 C1 107.1(5) . . ?<br />

C10 C4 C1 107.9(6) . . ?<br />

C9 C4 C5 109.3(5) . . ?<br />

C10 C4 C5 111.5(5) . . ?<br />

C1 C4 C5 113.0(5) . . ?<br />

C6 C5 C11 116.7(5) . . ?<br />

C6 C5 C4 109.6(5) . . ?<br />

C11 C5 C4 116.0(5) . . ?<br />

C6 C5 H5 104.3 . . ?<br />

C11 C5 H5 104.3 . . ?<br />

C4 C5 H5 104.3 . . ?<br />

O2 C6 C5 111.7(5) . . ?<br />

O2 C6 C7 107.5(5) . . ?<br />

C5 C6 C7 109.9(5) . . ?<br />

O2 C6 H6 109.2 . . ?<br />

C5 C6 H6 109.2 . . ?<br />

C7 C6 H6 109.2 . . ?<br />

O3 C7 C8 105.6(5) . . ?<br />

O3 C7 C6 111.9(5) . . ?<br />

C8 C7 C6 113.4(5) . . ?<br />

O3 C7 H7 108.6 . . ?<br />

C8 C7 H7 108.6 . . ?<br />

C6 C7 H7 108.6 . . ?<br />

C9 C8 C7 123.5(6) . . ?<br />

C9 C8 H8 118.3 . . ?<br />

C7 C8 H8 118.3 . . ?<br />

C8 C9 C4 124.0(6) . . ?<br />

C8 C9 H9 118.0 . . ?<br />

C4 C9 H9 118.0 . . ?<br />

C4 C10 H10A 109.5 . . ?<br />

C4 C10 H10B 109.5 . . ?<br />

H10A C10 H10B 109.5 . . ?<br />

C4 C10 H10C 109.5 . . ?<br />

H10A C10 H10C 109.5 . . ?<br />

H10B C10 H10C 109.5 . . ?<br />

C13 C11 C5 111.9(5) . . ?<br />

C13 C11 C12 109.3(6) . . ?<br />

C5 C11 C12 114.6(5) . . ?<br />

C13 C11 H11 106.9 . . ?<br />

C5 C11 H11 106.9 . . ?<br />

C12 C11 H11 106.9 . . ?<br />

C11 C12 H12A 109.5 . . ?<br />

C11 C12 H12B 109.5 . . ?<br />

H12A C12 H12B 109.5 . . ?<br />

C11 C12 H12C 109.5 . . ?<br />

H12A C12 H12C 109.5 . . ?<br />

H12B C12 H12C 109.5 . . ?<br />

C11 C13 H13A 109.5 . . ?<br />

C11 C13 H13B 109.5 . . ?<br />

H13A C13 H13B 109.5 . . ?<br />

C11 C13 H13C 109.5 . . ?<br />

H13A C13 H13C 109.5 . . ?<br />

H13B C13 H13C 109.5 . . ?<br />

C15 C14 C19 120.0(7) . . ?<br />

C15 C14 C2 121.5(7) . . ?<br />

C19 C14 C2 118.5(6) . . ?<br />

C14 C15 C16 118.7(7) . . ?<br />

C14 C15 H15 120.7 . . ?<br />

C16 C15 H15 120.7 . . ?<br />

C17 C16 C15 121.7(7) . . ?<br />

C17 C16 H16 119.2 . . ?<br />

C15 C16 H16 119.2 . . ?<br />

C16 C17 C18 120.1(7) . . ?<br />

C16 C17 H17 119.9 . . ?<br />

C18 C17 H17 119.9 . . ?<br />

C17 C18 C19 118.6(7) . . ?<br />

C17 C18 H18 120.7 . . ?<br />

C19 C18 H18 120.7 . . ?<br />

C14 C19 C18 120.9(7) . . ?<br />

C14 C19 H19 119.5 . . ?<br />

C18 C19 H19 119.5 . . ?<br />

C25 C20 C21 118.3(6) . . ?<br />

C25 C20 C3 122.2(6) . . ?<br />

C21 C20 C3 119.4(6) . . ?<br />

C22 C21 C20 120.6(7) . . ?<br />

C22 C21 H21 119.7 . . ?<br />

318


C20 C21 H21 119.7 . . ?<br />

C21 C22 C23 121.1(7) . . ?<br />

C21 C22 H22 119.5 . . ?<br />

C23 C22 H22 119.5 . . ?<br />

C22 C23 C24 119.2(7) . . ?<br />

C22 C23 H23 120.4 . . ?<br />

C24 C23 H23 120.4 . . ?<br />

C25 C24 C23 119.1(7) . . ?<br />

C25 C24 H24 120.4 . . ?<br />

C23 C24 H24 120.4 . . ?<br />

C20 C25 C24 121.6(7) . . ?<br />

C20 C25 H25 119.2 . . ?<br />

C24 C25 H25 119.2 . . ?<br />

N2 C26 O4 118.2(6) . . ?<br />

N2 C26 C29 125.4(6) . . ?<br />

O4 C26 C29 116.1(6) . . ?<br />

O4 C27 C39 108.2(5) . . ?<br />

O4 C27 C28 104.2(5) . . ?<br />

C39 C27 C28 114.9(6) . . ?<br />

O4 C27 H27 109.8 . . ?<br />

C39 C27 H27 109.8 . . ?<br />

C28 C27 H27 109.8 . . ?<br />

N2 C28 C45 113.8(5) . . ?<br />

N2 C28 C27 104.3(5) . . ?<br />

C45 C28 C27 115.1(6) . . ?<br />

N2 C28 H28 107.8 . . ?<br />

C45 C28 H28 107.8 . . ?<br />

C27 C28 H28 107.8 . . ?<br />

C26 C29 C34 106.7(5) . . ?<br />

C26 C29 C35 108.7(5) . . ?<br />

C34 C29 C35 107.6(6) . . ?<br />

C26 C29 C30 113.7(6) . . ?<br />

C34 C29 C30 108.8(5) . . ?<br />

C35 C29 C30 111.1(5) . . ?<br />

C31 C30 C36 116.6(5) . . ?<br />

C31 C30 C29 108.8(5) . . ?<br />

C36 C30 C29 116.6(5) . . ?<br />

C31 C30 H30 104.4 . . ?<br />

C36 C30 H30 104.4 . . ?<br />

C29 C30 H30 104.4 . . ?<br />

O5 C31 C32 107.9(5) . . ?<br />

O5 C31 C30 111.3(5) . . ?<br />

C32 C31 C30 110.1(6) . . ?<br />

O5 C31 H31 109.2 . . ?<br />

C32 C31 H31 109.2 . . ?<br />

C30 C31 H31 109.2 . . ?<br />

O6 C32 C33 105.7(5) . . ?<br />

O6 C32 C31 112.5(6) . . ?<br />

C33 C32 C31 111.9(5) . . ?<br />

O6 C32 H32 108.9 . . ?<br />

C33 C32 H32 108.9 . . ?<br />

C31 C32 H32 108.9 . . ?<br />

C34 C33 C32 125.0(6) . . ?<br />

C34 C33 H33 117.5 . . ?<br />

C32 C33 H33 117.5 . . ?<br />

C33 C34 C29 122.3(6) . . ?<br />

C33 C34 H34 118.8 . . ?<br />

C29 C34 H34 118.8 . . ?<br />

C29 C35 H35A 109.5 . . ?<br />

C29 C35 H35B 109.5 . . ?<br />

H35A C35 H35B 109.5 . . ?<br />

C29 C35 H35C 109.5 . . ?<br />

H35A C35 H35C 109.5 . . ?<br />

H35B C35 H35C 109.5 . . ?<br />

C38 C36 C37 111.2(6) . . ?<br />

C38 C36 C30 111.0(6) . . ?<br />

C37 C36 C30 116.0(5) . . ?<br />

C38 C36 H36 106.0 . . ?<br />

C37 C36 H36 106.0 . . ?<br />

C30 C36 H36 106.0 . . ?<br />

C36 C37 H37A 109.5 . . ?<br />

C36 C37 H37B 109.5 . . ?<br />

H37A C37 H37B 109.5 . . ?<br />

C36 C37 H37C 109.5 . . ?<br />

H37A C37 H37C 109.5 . . ?<br />

H37B C37 H37C 109.5 . . ?<br />

319


C36 C38 H38A 109.5 . . ?<br />

C36 C38 H38B 109.5 . . ?<br />

H38A C38 H38B 109.5 . . ?<br />

C36 C38 H38C 109.5 . . ?<br />

H38A C38 H38C 109.5 . . ?<br />

H38B C38 H38C 109.5 . . ?<br />

C40 C39 C44 119.2(7) . . ?<br />

C40 C39 C27 120.9(6) . . ?<br />

C44 C39 C27 119.9(7) . . ?<br />

C39 C40 C41 121.2(7) . . ?<br />

C39 C40 H40 119.4 . . ?<br />

C41 C40 H40 119.4 . . ?<br />

C42 C41 C40 118.4(8) . . ?<br />

C42 C41 H41 120.8 . . ?<br />

C40 C41 H41 120.8 . . ?<br />

C43 C42 C41 120.7(8) . . ?<br />

C43 C42 H42 119.7 . . ?<br />

C41 C42 H42 119.7 . . ?<br />

C42 C43 C44 121.0(8) . . ?<br />

C42 C43 H43 119.5 . . ?<br />

C44 C43 H43 119.5 . . ?<br />

C43 C44 C39 119.5(8) . . ?<br />

C43 C44 H44 120.2 . . ?<br />

C39 C44 H44 120.2 . . ?<br />

C50 C45 C46 118.9(7) . . ?<br />

C50 C45 C28 122.0(6) . . ?<br />

C46 C45 C28 119.0(6) . . ?<br />

C47 C46 C45 120.0(7) . . ?<br />

C47 C46 H46 120.0 . . ?<br />

C45 C46 H46 120.0 . . ?<br />

C46 C47 C48 122.3(7) . . ?<br />

C46 C47 H47 118.8 . . ?<br />

C48 C47 H47 118.8 . . ?<br />

C47 C48 C49 118.2(7) . . ?<br />

C47 C48 H48 120.9 . . ?<br />

C49 C48 H48 120.9 . . ?<br />

C50 C49 C48 119.1(7) . . ?<br />

C50 C49 H49 120.4 . . ?<br />

C48 C49 H49 120.4 . . ?<br />

C45 C50 C49 121.3(7) . . ?<br />

C45 C50 H50 119.3 . . ?<br />

C49 C50 H50 119.3 . . ?<br />

C1 N1 C3 105.5(5) . . ?<br />

C26 N2 C28 107.3(6) . . ?<br />

C1 O1 C2 104.1(5) . . ?<br />

C6 O2 H2A 109.5 . . ?<br />

C7 O3 H3A 109.5 . . ?<br />

C26 O4 C27 105.7(5) . . ?<br />

C31 O5 H5A 109.5 . . ?<br />

C32 O6 H6A 109.5 . . ?<br />

loop_<br />

_geom_<strong>to</strong>rsion_a<strong>to</strong>m_site_label_1<br />

_geom_<strong>to</strong>rsion_a<strong>to</strong>m_site_label_2<br />

_geom_<strong>to</strong>rsion_a<strong>to</strong>m_site_label_3<br />

_geom_<strong>to</strong>rsion_a<strong>to</strong>m_site_label_4<br />

_geom_<strong>to</strong>rsion<br />

_geom_<strong>to</strong>rsion_site_symmetry_1<br />

_geom_<strong>to</strong>rsion_site_symmetry_2<br />

_geom_<strong>to</strong>rsion_site_symmetry_3<br />

_geom_<strong>to</strong>rsion_site_symmetry_4<br />

_geom_<strong>to</strong>rsion_publ_flag<br />

O1 C2 C3 N1 -15.7(6) . . . . ?<br />

C14 C2 C3 N1 -133.9(6) . . . . ?<br />

O1 C2 C3 C20 -140.9(6) . . . . ?<br />

C14 C2 C3 C20 100.9(7) . . . . ?<br />

N1 C1 C4 C9 -5.2(9) . . . . ?<br />

O1 C1 C4 C9 171.5(6) . . . . ?<br />

N1 C1 C4 C10 -121.1(7) . . . . ?<br />

O1 C1 C4 C10 55.7(7) . . . . ?<br />

N1 C1 C4 C5 115.1(7) . . . . ?<br />

O1 C1 C4 C5 -68.1(7) . . . . ?<br />

C9 C4 C5 C6 48.6(7) . . . . ?<br />

C10 C4 C5 C6 167.7(5) . . . . ?<br />

C1 C4 C5 C6 -70.5(6) . . . . ?<br />

C9 C4 C5 C11 -176.5(5) . . . . ?<br />

C10 C4 C5 C11 -57.4(7) . . . . ?<br />

320


C1 C4 C5 C11 64.4(7) . . . . ?<br />

C11 C5 C6 O2 42.6(7) . . . . ?<br />

C4 C5 C6 O2 177.1(5) . . . . ?<br />

C11 C5 C6 C7 161.8(5) . . . . ?<br />

C4 C5 C6 C7 -63.7(6) . . . . ?<br />

O2 C6 C7 O3 -75.2(6) . . . . ?<br />

C5 C6 C7 O3 163.1(5) . . . . ?<br />

O2 C6 C7 C8 165.4(5) . . . . ?<br />

C5 C6 C7 C8 43.7(7) . . . . ?<br />

O3 C7 C8 C9 -133.1(7) . . . . ?<br />

C6 C7 C8 C9 -10.2(9) . . . . ?<br />

C7 C8 C9 C4 -3.8(10) . . . . ?<br />

C10 C4 C9 C8 -137.2(7) . . . . ?<br />

C1 C4 C9 C8 106.9(8) . . . . ?<br />

C5 C4 C9 C8 -15.8(9) . . . . ?<br />

C6 C5 C11 C13 -90.0(7) . . . . ?<br />

C4 C5 C11 C13 138.3(6) . . . . ?<br />

C6 C5 C11 C12 35.1(8) . . . . ?<br />

C4 C5 C11 C12 -96.5(7) . . . . ?<br />

O1 C2 C14 C15 127.8(7) . . . . ?<br />

C3 C2 C14 C15 -116.5(7) . . . . ?<br />

O1 C2 C14 C19 -54.2(8) . . . . ?<br />

C3 C2 C14 C19 61.6(9) . . . . ?<br />

C19 C14 C15 C16 1.4(11) . . . . ?<br />

C2 C14 C15 C16 179.4(6) . . . . ?<br />

C14 C15 C16 C17 -0.6(12) . . . . ?<br />

C15 C16 C17 C18 -0.5(13) . . . . ?<br />

C16 C17 C18 C19 0.8(13) . . . . ?<br />

C15 C14 C19 C18 -1.1(12) . . . . ?<br />

C2 C14 C19 C18 -179.2(7) . . . . ?<br />

C17 C18 C19 C14 0.0(12) . . . . ?<br />

N1 C3 C20 C25 -10.5(9) . . . . ?<br />

C2 C3 C20 C25 110.5(7) . . . . ?<br />

N1 C3 C20 C21 165.3(6) . . . . ?<br />

C2 C3 C20 C21 -73.7(8) . . . . ?<br />

C25 C20 C21 C22 2.0(10) . . . . ?<br />

C3 C20 C21 C22 -174.0(6) . . . . ?<br />

C20 C21 C22 C23 0.6(10) . . . . ?<br />

C21 C22 C23 C24 -3.5(10) . . . . ?<br />

C22 C23 C24 C25 3.7(10) . . . . ?<br />

C21 C20 C25 C24 -1.7(10) . . . . ?<br />

C3 C20 C25 C24 174.1(6) . . . . ?<br />

C23 C24 C25 C20 -1.1(10) . . . . ?<br />

O4 C27 C28 N2 -6.0(6) . . . . ?<br />

C39 C27 C28 N2 -124.2(6) . . . . ?<br />

O4 C27 C28 C45 -131.4(6) . . . . ?<br />

C39 C27 C28 C45 110.4(7) . . . . ?<br />

N2 C26 C29 C34 -11.6(9) . . . . ?<br />

O4 C26 C29 C34 163.0(5) . . . . ?<br />

N2 C26 C29 C35 -127.3(7) . . . . ?<br />

O4 C26 C29 C35 47.3(8) . . . . ?<br />

N2 C26 C29 C30 108.4(7) . . . . ?<br />

O4 C26 C29 C30 -77.0(7) . . . . ?<br />

C26 C29 C30 C31 -67.1(7) . . . . ?<br />

C34 C29 C30 C31 51.7(7) . . . . ?<br />

C35 C29 C30 C31 169.9(5) . . . . ?<br />

C26 C29 C30 C36 67.2(7) . . . . ?<br />

C34 C29 C30 C36 -174.0(5) . . . . ?<br />

C35 C29 C30 C36 -55.8(7) . . . . ?<br />

C36 C30 C31 O5 39.7(7) . . . . ?<br />

C29 C30 C31 O5 174.0(5) . . . . ?<br />

C36 C30 C31 C32 159.3(5) . . . . ?<br />

C29 C30 C31 C32 -66.4(7) . . . . ?<br />

O5 C31 C32 O6 -75.2(6) . . . . ?<br />

C30 C31 C32 O6 163.2(5) . . . . ?<br />

O5 C31 C32 C33 166.0(5) . . . . ?<br />

C30 C31 C32 C33 44.4(7) . . . . ?<br />

O6 C32 C33 C34 -134.3(6) . . . . ?<br />

C31 C32 C33 C34 -11.6(9) . . . . ?<br />

C32 C33 C34 C29 -0.8(10) . . . . ?<br />

C26 C29 C34 C33 103.1(7) . . . . ?<br />

C35 C29 C34 C33 -140.4(6) . . . . ?<br />

C30 C29 C34 C33 -20.0(9) . . . . ?<br />

C31 C30 C36 C38 -87.8(7) . . . . ?<br />

C29 C30 C36 C38 141.4(6) . . . . ?<br />

C31 C30 C36 C37 40.3(8) . . . . ?<br />

321


C29 C30 C36 C37 -90.4(7) . . . . ?<br />

O4 C27 C39 C40 -44.7(9) . . . . ?<br />

C28 C27 C39 C40 71.2(8) . . . . ?<br />

O4 C27 C39 C44 136.0(7) . . . . ?<br />

C28 C27 C39 C44 -108.1(8) . . . . ?<br />

C44 C39 C40 C41 2.3(11) . . . . ?<br />

C27 C39 C40 C41 -177.1(7) . . . . ?<br />

C39 C40 C41 C42 -1.7(11) . . . . ?<br />

C40 C41 C42 C43 1.3(12) . . . . ?<br />

C41 C42 C43 C44 -1.6(13) . . . . ?<br />

C42 C43 C44 C39 2.2(13) . . . . ?<br />

C40 C39 C44 C43 -2.5(12) . . . . ?<br />

C27 C39 C44 C43 176.8(7) . . . . ?<br />

N2 C28 C45 C50 5.5(10) . . . . ?<br />

C27 C28 C45 C50 125.8(7) . . . . ?<br />

N2 C28 C45 C46 -177.1(6) . . . . ?<br />

C27 C28 C45 C46 -56.8(8) . . . . ?<br />

C50 C45 C46 C47 1.7(11) . . . . ?<br />

C28 C45 C46 C47 -175.9(6) . . . . ?<br />

C45 C46 C47 C48 0.7(11) . . . . ?<br />

C46 C47 C48 C49 -1.1(11) . . . . ?<br />

C47 C48 C49 C50 -0.8(11) . . . . ?<br />

C46 C45 C50 C49 -3.6(11) . . . . ?<br />

C28 C45 C50 C49 173.8(6) . . . . ?<br />

C48 C49 C50 C45 3.2(11) . . . . ?<br />

O1 C1 N1 C3 -4.9(9) . . . . ?<br />

C4 C1 N1 C3 171.7(6) . . . . ?<br />

C20 C3 N1 C1 140.6(6) . . . . ?<br />

C2 C3 N1 C1 12.8(7) . . . . ?<br />

O4 C26 N2 C28 -0.2(8) . . . . ?<br />

C29 C26 N2 C28 174.3(6) . . . . ?<br />

C45 C28 N2 C26 130.2(6) . . . . ?<br />

C27 C28 N2 C26 4.0(7) . . . . ?<br />

N1 C1 O1 C2 -5.6(8) . . . . ?<br />

C4 C1 O1 C2 177.5(5) . . . . ?<br />

C14 C2 O1 C1 136.2(6) . . . . ?<br />

C3 C2 O1 C1 12.9(6) . . . . ?<br />

N2 C26 O4 C27 -3.9(8) . . . . ?<br />

C29 C26 O4 C27 -178.9(5) . . . . ?<br />

C39 C27 O4 C26 128.6(6) . . . . ?<br />

C28 C27 O4 C26 5.9(6) . . . . ?<br />

loop_<br />

_geom_hbond_a<strong>to</strong>m_site_label_D<br />

_geom_hbond_a<strong>to</strong>m_site_label_H<br />

_geom_hbond_a<strong>to</strong>m_site_label_A<br />

_geom_hbond_distance_DH<br />

_geom_hbond_distance_HA<br />

_geom_hbond_distance_DA<br />

_geom_hbond_angle_DHA<br />

_geom_hbond_site_symmetry_A<br />

O2 H2A O6 0.84 2.08 2.761(6) 137.9 1_545<br />

O3 H3A N2 0.84 2.11 2.883(7) 152.0 1_545<br />

O6 H6A O2 0.84 2.13 2.761(6) 131.7 1_565<br />

O5 H5A O3 0.84 2.26 2.793(6) 121.1 1_465<br />

_diffrn_measured_fraction_theta_max 0.884<br />

_diffrn_reflns_theta_full 28.26<br />

_diffrn_measured_fraction_theta_full 0.884<br />

_refine_diff_density_max 0.242<br />

_refine_diff_density_min -0.242<br />

_refine_diff_density_rms 0.055<br />

322


d. Compound 278<br />

HO<br />

OH<br />

HO<br />

OH<br />

278<br />

OH<br />

Identification code s2760m<br />

Empirical formula C11 H24 O6<br />

Formula weight 252.30<br />

Temperature<br />

100(2) K<br />

Wavelength<br />

0.71073 A<br />

Crystal system, space group Monoclinic, P21<br />

Unit cell dimensions a = 11.603(2) A alpha = 90 deg.<br />

b = 8.0007(16) A beta = 106.896(4) deg.<br />

c = 14.488(3) A gamma = 90 deg.<br />

Volume<br />

1286.9(4) A^3<br />

Z, Calculated density 4, 1.302 Mg/m^3<br />

Absorption coefficient 0.105 mm^-1<br />

F(000) 552<br />

Crystal size<br />

0.20 x 0.10 x 0.04 mm<br />

<strong>The</strong>ta range for data collection 1.83 <strong>to</strong> 25.02 deg.<br />

Limiting indices -13


<strong>The</strong> structure was solved by the direct methods<br />

and there are two molecules in the asymmetric unit.<br />

All non-H a<strong>to</strong>ms were refined anisotropically.<br />

H a<strong>to</strong>ms were included in calculated positions.<br />

<strong>The</strong> absolute configuration was input.<br />

_chemical_formula_sum<br />

'C11 H24 O6'<br />

_chemical_formula_weight 252.30<br />

loop_<br />

_a<strong>to</strong>m_type_symbol<br />

_a<strong>to</strong>m_type_description<br />

_a<strong>to</strong>m_type_scat_dispersion_real<br />

_a<strong>to</strong>m_type_scat_dispersion_imag<br />

_a<strong>to</strong>m_type_scat_source<br />

'C' 'C' 0.0033 0.0016<br />

'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'<br />

'H' 'H' 0.0000 0.0000<br />

'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'<br />

'O' 'O' 0.0106 0.0060<br />

'International Tables Vol C Tables 4.2.6.8 and 6.1.1.4'<br />

_symmetry_cell_setting Monoclinic<br />

_symmetry_space_group_name_H-M P21<br />

loop_<br />

_symmetry_equiv_pos_as_xyz<br />

'x, y, z'<br />

'-x, y+1/2, -z'<br />

_cell_length_a 11.603(2)<br />

_cell_length_b 8.0007(16)<br />

_cell_length_c 14.488(3)<br />

_cell_angle_alpha 90.00<br />

_cell_angle_beta 106.896(4)<br />

_cell_angle_gamma 90.00<br />

_cell_volume 1286.9(4)<br />

_cell_formula_units_Z 4<br />

_cell_measurement_temperature 100(2)<br />

_cell_measurement_reflns_used 673<br />

_cell_measurement_theta_min 2.94<br />

_cell_measurement_theta_max 23.62<br />

324


_exptl_crystal_description plate<br />

_exptl_crystal_colour colourless<br />

_exptl_crystal_size_max 0.20<br />

_exptl_crystal_size_mid 0.10<br />

_exptl_crystal_size_min 0.04<br />

_exptl_crystal_density_meas ?<br />

_exptl_crystal_density_diffrn 1.302<br />

_exptl_crystal_density_method 'not measured'<br />

_exptl_crystal_F_000 552<br />

_exptl_absorpt_coefficient_mu 0.105<br />

_exptl_absorpt_correction_type none<br />

_exptl_absorpt_correction_T_min ?<br />

_exptl_absorpt_correction_T_max ?<br />

_exptl_absorpt_process_details ?<br />

_exptl_special_details<br />

_diffrn_ambient_temperature 100(2)<br />

_diffrn_radiation_wavelength 0.71073<br />

_diffrn_radiation_type MoK\a<br />

_diffrn_radiation_source 'fine-focus sealed tube'<br />

_diffrn_radiation_monochroma<strong>to</strong>r graphite<br />

_diffrn_measurement_device_type 'CCD area detec<strong>to</strong>r'<br />

_diffrn_measurement_method 'phi and omega scans'<br />

_diffrn_detec<strong>to</strong>r_area_resol_mean ?<br />

_diffrn_standards_number ?<br />

_diffrn_standards_interval_count ?<br />

_diffrn_standards_interval_time ?<br />

_diffrn_standards_decay_% ?<br />

_diffrn_reflns_number 8740<br />

_diffrn_reflns_av_R_equivalents 0.0738<br />

_diffrn_reflns_av_sigmaI/netI 0.0742<br />

_diffrn_reflns_limit_h_min -13<br />

_diffrn_reflns_limit_h_max 13<br />

_diffrn_reflns_limit_k_min -9<br />

_diffrn_reflns_limit_k_max 9<br />

_diffrn_reflns_limit_l_min -17<br />

_diffrn_reflns_limit_l_max 16<br />

_diffrn_reflns_theta_min 1.83<br />

_diffrn_reflns_theta_max 25.02<br />

325


_reflns_number_<strong>to</strong>tal 2447<br />

_reflns_number_gt 2122<br />

_reflns_threshold_expression >2sigma(I)<br />

_computing_data_collection 'Bruker SMART'<br />

_computing_cell_refinement 'Bruker SMART'<br />

_computing_data_reduction 'Bruker SAINT'<br />

_computing_structure_solution 'SHELXS-97 (Sheldrick, 1990)'<br />

_computing_structure_refinement 'SHELXL-97 (Sheldrick, 1997)'<br />

_computing_molecular_graphics 'Bruker SHELXTL'<br />

_computing_publication_material 'Bruker SHELXTL'<br />

_refine_special_details<br />

Refinement of F^2^ against ALL reflections. <strong>The</strong> weighted R-fac<strong>to</strong>r wR and<br />

goodness of fit S are based on F^2^, conventional R-fac<strong>to</strong>rs R are based<br />

on F, with F set <strong>to</strong> zero for negative F^2^. <strong>The</strong> threshold expression of<br />

F^2^ > 2sigma(F^2^) is used only for calculating R-fac<strong>to</strong>rs(gt) etc. and is<br />

not relevant <strong>to</strong> the choice of reflections for refinement. R-fac<strong>to</strong>rs based<br />

on F^2^ are statistically about twice as large as those based on F, and R-<br />

fac<strong>to</strong>rs based on ALL data will be even larger.<br />

_refine_ls_structure_fac<strong>to</strong>r_coef Fsqd<br />

_refine_ls_matrix_type full<br />

_refine_ls_weighting_scheme calc<br />

_refine_ls_weighting_details<br />

'calc w=1/[\s^2^(Fo^2^)+(0.0259P)^2^+0.4529P] where P=(Fo^2^+2Fc^2^)/3'<br />

_a<strong>to</strong>m_sites_solution_primary direct<br />

_a<strong>to</strong>m_sites_solution_secondary difmap<br />

_a<strong>to</strong>m_sites_solution_hydrogens geom<br />

_chemical_absolute_configuration syn<br />

_refine_ls_hydrogen_treatment mixed<br />

_refine_ls_extinction_method none<br />

_refine_ls_extinction_coef ?<br />

_refine_ls_number_reflns 2447<br />

_refine_ls_number_parameters 339<br />

_refine_ls_number_restraints 1<br />

_refine_ls_R_fac<strong>to</strong>r_all 0.0721<br />

_refine_ls_R_fac<strong>to</strong>r_gt 0.0592<br />

_refine_ls_wR_fac<strong>to</strong>r_ref 0.1045<br />

_refine_ls_wR_fac<strong>to</strong>r_gt 0.1006<br />

_refine_ls_goodness_of_fit_ref 1.154<br />

326


_refine_ls_restrained_S_all 1.154<br />

_refine_ls_shift/su_max 0.000<br />

_refine_ls_shift/su_mean 0.000<br />

loop_<br />

_a<strong>to</strong>m_site_label<br />

_a<strong>to</strong>m_site_type_symbol<br />

_a<strong>to</strong>m_site_fract_x<br />

_a<strong>to</strong>m_site_fract_y<br />

_a<strong>to</strong>m_site_fract_z<br />

_a<strong>to</strong>m_site_U_iso_or_equiv<br />

_a<strong>to</strong>m_site_adp_type<br />

_a<strong>to</strong>m_site_occupancy<br />

_a<strong>to</strong>m_site_symmetry_multiplicity<br />

_a<strong>to</strong>m_site_calc_flag<br />

_a<strong>to</strong>m_site_refinement_flags<br />

_a<strong>to</strong>m_site_disorder_assembly<br />

_a<strong>to</strong>m_site_disorder_group<br />

O1 O 1.2534(3) 0.8414(5) 1.1873(2) 0.0274(9) Uani 1 1 d . . .<br />

H1 H 1.3159 0.8625 1.2323 0.041 Uiso 1 1 calc R . .<br />

O2 O 0.7867(3) 0.6097(4) 1.2036(3) 0.0189(8) Uani 1 1 d . . .<br />

H2 H 0.7921 0.5052 1.2085 0.028 Uiso 1 1 calc R . .<br />

O3 O 0.7790(3) 0.6641(4) 1.0083(2) 0.0198(8) Uani 1 1 d . . .<br />

H3 H 0.7053 0.6879 0.9927 0.030 Uiso 1 1 calc R . .<br />

O4 O 0.8975(3) 0.9572(4) 0.9708(2) 0.0228(8) Uani 1 1 d . . .<br />

H4 H 0.8385 0.9090 0.9325 0.034 Uiso 1 1 calc R . .<br />

O5 O 0.9383(3) 1.1074(4) 1.1463(2) 0.0181(8) Uani 1 1 d . . .<br />

H5 H 0.9076 1.1543 1.0930 0.027 Uiso 1 1 calc R . .<br />

C1 C 1.0655(4) 0.8838(6) 1.2325(3) 0.0150(11) Uani 1 1 d . . .<br />

C2 C 0.9646(4) 0.7839(6) 1.2604(3) 0.0169(11) Uani 1 1 d . . .<br />

H2A H 0.9076 0.8709 1.2707 0.020 Uiso 1 1 calc R . .<br />

C3 C 0.8888(4) 0.6744(6) 1.1774(3) 0.0160(11) Uani 1 1 d . . .<br />

H3A H 0.9391 0.5790 1.1668 0.019 Uiso 1 1 calc R . .<br />

C4 C 0.8435(4) 0.7719(6) 1.0851(3) 0.0152(11) Uani 1 1 d . . .<br />

H4A H 0.7867 0.8598 1.0947 0.018 Uiso 1 1 calc R . .<br />

C5 C 0.9429(4) 0.8564(6) 1.0555(3) 0.0189(12) Uani 1 1 d . . .<br />

H5A H 0.9979 0.7692 1.0424 0.023 Uiso 1 1 calc R . .<br />

C6 C 1.0152(4) 0.9726(6) 1.1341(3) 0.0159(10) Uani 1 1 d . . .<br />

H6 H 1.0839 1.0201 1.1139 0.019 Uiso 1 1 calc R . .<br />

327


C7 C 1.1671(4) 0.7629(7) 1.2254(4) 0.0242(12) Uani 1 1 d . . .<br />

H7A H 1.2084 0.7187 1.2905 0.029 Uiso 1 1 calc R . .<br />

H7B H 1.1309 0.6671 1.1838 0.029 Uiso 1 1 calc R . .<br />

C8 C 1.1195(4) 1.0188(6) 1.3087(3) 0.0199(12) Uani 1 1 d . . .<br />

H8A H 1.0544 1.0848 1.3210 0.030 Uiso 1 1 calc R . .<br />

H8B H 1.1722 1.0922 1.2848 0.030 Uiso 1 1 calc R . .<br />

H8C H 1.1664 0.9651 1.3686 0.030 Uiso 1 1 calc R . .<br />

C9 C 1.0102(5) 0.6905(6) 1.3590(3) 0.0200(12) Uani 1 1 d . . .<br />

H9 H 1.0862 0.7472 1.3965 0.024 Uiso 1 1 calc R . .<br />

C10 C 1.0415(4) 0.5043(7) 1.3499(3) 0.0231(12) Uani 1 1 d . . .<br />

H10A H 0.9672 0.4406 1.3230 0.035 Uiso 1 1 calc R . .<br />

H10B H 1.0842 0.4602 1.4138 0.035 Uiso 1 1 calc R . .<br />

H10C H 1.0930 0.4943 1.3072 0.035 Uiso 1 1 calc R . .<br />

C11 C 0.9215(5) 0.7050(7) 1.4181(3) 0.0289(14) Uani 1 1 d . . .<br />

H11A H 0.9549 0.6495 1.4805 0.043 Uiso 1 1 calc R . .<br />

H11B H 0.8452 0.6517 1.3833 0.043 Uiso 1 1 calc R . .<br />

H11C H 0.9073 0.8233 1.4287 0.043 Uiso 1 1 calc R . .<br />

O6 O 0.5233(3) 0.4657(4) 0.7296(2) 0.0178(8) Uani 1 1 d . . .<br />

H6A H 0.5004 0.3934 0.7625 0.027 Uiso 1 1 calc R . .<br />

O7 O 0.6153(3) 0.9803(4) 0.8264(2) 0.0183(8) Uani 1 1 d . . .<br />

H7 H 0.5740 1.0656 0.8285 0.027 Uiso 1 1 calc R . .<br />

O8 O 0.5623(3) 0.8147(4) 0.9779(2) 0.0154(7) Uani 1 1 d . . .<br />

H8 H 0.5943 0.9097 0.9890 0.023 Uiso 1 1 calc R . .<br />

O9 O 0.3635(3) 0.6085(4) 0.9470(2) 0.0147(8) Uani 1 1 d . . .<br />

H9A H 0.3120 0.6807 0.9497 0.022 Uiso 1 1 calc R . .<br />

O10 O 0.2212(3) 0.7613(4) 0.7757(2) 0.0151(7) Uani 1 1 d . . .<br />

H10 H 0.1677 0.7116 0.7937 0.023 Uiso 1 1 calc R . .<br />

C12 C 0.3608(4) 0.6857(6) 0.6852(3) 0.0164(11) Uani 1 1 d . . .<br />

C13 C 0.4427(4) 0.8464(6) 0.7063(3) 0.0152(11) Uani 1 1 d . . .<br />

H13 H 0.3883 0.9411 0.7107 0.018 Uiso 1 1 calc R . .<br />

C14 C 0.5389(4) 0.8370(6) 0.8059(3) 0.0172(11) Uani 1 1 d . . .<br />

H14 H 0.5903 0.7365 0.8063 0.021 Uiso 1 1 calc R . .<br />

C15 C 0.4759(4) 0.8137(6) 0.8835(3) 0.0130(10) Uani 1 1 d . . .<br />

H15 H 0.4162 0.9058 0.8790 0.016 Uiso 1 1 calc R . .<br />

C16 C 0.4122(4) 0.6481(6) 0.8703(3) 0.0148(11) Uani 1 1 d . . .<br />

H16 H 0.4728 0.5601 0.8690 0.018 Uiso 1 1 calc R . .<br />

C17 C 0.3148(4) 0.6441(6) 0.7724(3) 0.0132(11) Uani 1 1 d . . .<br />

H17 H 0.2789 0.5295 0.7628 0.016 Uiso 1 1 calc R . .<br />

328


C18 C 0.4218(4) 0.5303(6) 0.6578(3) 0.0154(11) Uani 1 1 d . . .<br />

H18A H 0.3607 0.4405 0.6392 0.018 Uiso 1 1 calc R . .<br />

H18B H 0.4474 0.5579 0.6001 0.018 Uiso 1 1 calc R . .<br />

C19 C 0.2507(4) 0.7174(7) 0.5978(3) 0.0194(12) Uani 1 1 d . . .<br />

H19A H 0.2749 0.7122 0.5385 0.029 Uiso 1 1 calc R . .<br />

H19B H 0.2174 0.8282 0.6035 0.029 Uiso 1 1 calc R . .<br />

H19C H 0.1894 0.6321 0.5957 0.029 Uiso 1 1 calc R . .<br />

C20 C 0.4964(5) 0.8919(6) 0.6218(3) 0.0174(11) Uani 1 1 d . . .<br />

H20 H 0.4419 0.8422 0.5615 0.021 Uiso 1 1 calc R . .<br />

C21 C 0.6229(4) 0.8220(7) 0.6336(3) 0.0223(12) Uani 1 1 d . . .<br />

H21A H 0.6798 0.8722 0.6905 0.033 Uiso 1 1 calc R . .<br />

H21B H 0.6477 0.8486 0.5761 0.033 Uiso 1 1 calc R . .<br />

H21C H 0.6222 0.7004 0.6418 0.033 Uiso 1 1 calc R . .<br />

C22 C 0.4955(5) 1.0817(6) 0.6070(4) 0.0247(13) Uani 1 1 d . . .<br />

H22A H 0.5219 1.1073 0.5501 0.037 Uiso 1 1 calc R . .<br />

H22B H 0.5504 1.1346 0.6639 0.037 Uiso 1 1 calc R . .<br />

H22C H 0.4138 1.1246 0.5974 0.037 Uiso 1 1 calc R . .<br />

O1S O 0.7845(3) 0.3209(5) 1.0057(3) 0.0216(8) Uani 1 1 d . . .<br />

H1S H 0.791(5) 0.416(7) 1.018(4) 0.03(2) Uiso 1 1 d . . .<br />

H2S H 0.763(4) 0.316(7) 0.940(4) 0.029(15) Uiso 1 1 d . . .<br />

O2S O 0.4449(3) 0.2330(4) 0.8381(2) 0.0173(8) Uani 1 1 d . . .<br />

H3S H 0.468(5) 0.250(8) 0.905(4) 0.046(18) Uiso 1 1 d . . .<br />

H4S H 0.365(7) 0.202(10) 0.827(5) 0.09(3) Uiso 1 1 d . . .<br />

loop_<br />

_a<strong>to</strong>m_site_aniso_label<br />

_a<strong>to</strong>m_site_aniso_U_11<br />

_a<strong>to</strong>m_site_aniso_U_22<br />

_a<strong>to</strong>m_site_aniso_U_33<br />

_a<strong>to</strong>m_site_aniso_U_23<br />

_a<strong>to</strong>m_site_aniso_U_13<br />

_a<strong>to</strong>m_site_aniso_U_12<br />

O1 0.0199(19) 0.039(2) 0.0234(19) -0.0002(19) 0.0067(16) -0.0021(19)<br />

O2 0.0159(18) 0.0124(18) 0.029(2) 0.0049(17) 0.0068(15) 0.0012(16)<br />

O3 0.0153(19) 0.020(2) 0.0212(19) -0.0045(15) 0.0004(16) 0.0009(16)<br />

O4 0.028(2) 0.024(2) 0.0145(17) -0.0005(16) 0.0029(15) -0.0070(17)<br />

O5 0.023(2) 0.0145(18) 0.0190(18) 0.0035(15) 0.0103(16) 0.0046(16)<br />

C1 0.013(2) 0.013(3) 0.018(3) -0.002(2) 0.003(2) -0.002(2)<br />

C2 0.014(3) 0.014(3) 0.021(3) 0.006(2) 0.004(2) 0.008(2)<br />

329


C3 0.015(3) 0.016(3) 0.021(3) -0.002(2) 0.012(2) -0.002(2)<br />

C4 0.015(2) 0.019(3) 0.011(2) -0.004(2) 0.003(2) 0.000(2)<br />

C5 0.028(3) 0.016(3) 0.017(3) 0.002(2) 0.012(2) -0.001(2)<br />

C6 0.017(3) 0.013(3) 0.020(3) -0.001(2) 0.009(2) -0.001(2)<br />

C7 0.016(3) 0.027(3) 0.030(3) 0.009(3) 0.008(2) 0.001(2)<br />

C8 0.022(3) 0.016(3) 0.021(3) -0.002(2) 0.006(2) -0.008(2)<br />

C9 0.021(3) 0.024(3) 0.016(3) 0.004(2) 0.006(2) 0.001(2)<br />

C10 0.019(3) 0.024(3) 0.024(3) 0.008(2) 0.002(2) 0.003(3)<br />

C11 0.036(3) 0.033(3) 0.020(3) 0.002(3) 0.011(3) -0.002(3)<br />

O6 0.0186(18) 0.0144(19) 0.0211(18) 0.0020(15) 0.0066(15) 0.0023(16)<br />

O7 0.0205(18) 0.0133(18) 0.0220(18) -0.0025(17) 0.0080(15) -0.0063(16)<br />

O8 0.0166(18) 0.0138(19) 0.0141(17) 0.0001(15) 0.0018(14) -0.0020(16)<br />

O9 0.0151(19) 0.0129(18) 0.0177(17) 0.0047(15) 0.0074(15) 0.0050(15)<br />

O10 0.0111(17) 0.0147(19) 0.0224(18) 0.0020(15) 0.0093(14) -0.0010(15)<br />

C12 0.015(3) 0.016(3) 0.018(3) -0.003(2) 0.006(2) -0.001(2)<br />

C13 0.023(3) 0.011(3) 0.013(2) -0.002(2) 0.008(2) 0.003(2)<br />

C14 0.014(2) 0.018(3) 0.020(3) -0.002(2) 0.006(2) -0.003(2)<br />

C15 0.013(2) 0.013(3) 0.011(2) 0.000(2) -0.0002(19) 0.007(2)<br />

C16 0.023(3) 0.006(3) 0.020(3) 0.000(2) 0.014(2) 0.003(2)<br />

C17 0.016(3) 0.003(2) 0.021(3) -0.001(2) 0.006(2) -0.001(2)<br />

C18 0.014(3) 0.019(3) 0.014(2) 0.001(2) 0.004(2) -0.001(2)<br />

C19 0.015(3) 0.022(3) 0.019(3) -0.004(2) 0.001(2) 0.000(2)<br />

C20 0.026(3) 0.014(3) 0.014(3) -0.001(2) 0.010(2) -0.005(2)<br />

C21 0.024(3) 0.024(3) 0.022(3) 0.002(2) 0.011(2) -0.002(3)<br />

C22 0.038(3) 0.019(3) 0.025(3) 0.001(2) 0.020(3) -0.004(3)<br />

O1S 0.033(2) 0.013(2) 0.022(2) -0.0036(17) 0.0114(17) -0.0030(19)<br />

O2S 0.023(2) 0.0147(19) 0.0155(19) 0.0006(16) 0.0068(16) -0.0009(17)<br />

_geom_special_details<br />

All esds (except the esd in the dihedral angle between two l.s. planes)<br />

are estimated using the full covariance matrix. <strong>The</strong> cell esds are taken<br />

in<strong>to</strong> account individually in the estimation of esds in distances, angles<br />

and <strong>to</strong>rsion angles; correlations between esds in cell parameters are only<br />

used when they are defined by crystal symmetry. An approximate (isotropic)<br />

treatment of cell esds is used for estimating esds involving l.s. planes.<br />

330


loop_<br />

_geom_bond_a<strong>to</strong>m_site_label_1<br />

_geom_bond_a<strong>to</strong>m_site_label_2<br />

_geom_bond_distance<br />

_geom_bond_site_symmetry_2<br />

_geom_bond_publ_flag<br />

O1 C7 1.423(5) . ?<br />

O1 H1 0.8400 . ?<br />

O2 C3 1.441(5) . ?<br />

O2 H2 0.8400 . ?<br />

O3 C4 1.434(5) . ?<br />

O3 H3 0.8400 . ?<br />

O4 C5 1.435(5) . ?<br />

O4 H4 0.8400 . ?<br />

O5 C6 1.443(6) . ?<br />

O5 H5 0.8400 . ?<br />

C1 C8 1.541(6) . ?<br />

C1 C6 1.547(6) . ?<br />

C1 C7 1.551(7) . ?<br />

C1 C2 1.564(6) . ?<br />

C2 C3 1.540(6) . ?<br />

C2 C9 1.562(6) . ?<br />

C2 H2A 1.0000 . ?<br />

C3 C4 1.505(6) . ?<br />

C3 H3A 1.0000 . ?<br />

C4 C5 1.503(6) . ?<br />

C4 H4A 1.0000 . ?<br />

C5 C6 1.520(6) . ?<br />

C5 H5A 1.0000 . ?<br />

C6 H6 1.0000 . ?<br />

C7 H7A 0.9900 . ?<br />

C7 H7B 0.9900 . ?<br />

C8 H8A 0.9800 . ?<br />

C8 H8B 0.9800 . ?<br />

C8 H8C 0.9800 . ?<br />

C9 C11 1.524(6) . ?<br />

C9 C10 1.547(7) . ?<br />

C9 H9 1.0000 . ?<br />

C10 H10A 0.9800 . ?<br />

C10 H10B 0.9800 . ?<br />

C10 H10C 0.9800 . ?<br />

C11 H11A 0.9800 . ?<br />

C11 H11B 0.9800 . ?<br />

C11 H11C 0.9800 . ?<br />

O6 C18 1.423(5) . ?<br />

O6 H6A 0.8400 . ?<br />

O7 C14 1.427(6) . ?<br />

O7 H7 0.8400 . ?<br />

O8 C15 1.443(5) . ?<br />

O8 H8 0.8400 . ?<br />

O9 C16 1.420(5) . ?<br />

O9 H9A 0.8400 . ?<br />

O10 C17 1.446(5) . ?<br />

O10 H10 0.8400 . ?<br />

C12 C19 1.536(6) . ?<br />

C12 C18 1.539(6) . ?<br />

C12 C17 1.544(6) . ?<br />

C12 C13 1.575(7) . ?<br />

C13 C14 1.549(6) . ?<br />

C13 C20 1.569(6) . ?<br />

C13 H13 1.0000 . ?<br />

C14 C15 1.520(6) . ?<br />

C14 H14 1.0000 . ?<br />

C15 C16 1.502(6) . ?<br />

C15 H15 1.0000 . ?<br />

C16 C17 1.535(6) . ?<br />

C16 H16 1.0000 . ?<br />

C17 H17 1.0000 . ?<br />

C18 H18A 0.9900 . ?<br />

C18 H18B 0.9900 . ?<br />

C19 H19A 0.9800 . ?<br />

C19 H19B 0.9800 . ?<br />

C19 H19C 0.9800 . ?<br />

C20 C21 1.533(7) . ?<br />

C20 C22 1.534(7) . ?<br />

C20 H20 1.0000 . ?<br />

331


C21 H21A 0.9800 . ?<br />

C21 H21B 0.9800 . ?<br />

C21 H21C 0.9800 . ?<br />

C22 H22A 0.9800 . ?<br />

C22 H22B 0.9800 . ?<br />

C22 H22C 0.9800 . ?<br />

O1S H1S 0.78(6) . ?<br />

O1S H2S 0.91(5) . ?<br />

O2S H3S 0.93(6) . ?<br />

O2S H4S 0.93(7) . ?<br />

loop_<br />

_geom_angle_a<strong>to</strong>m_site_label_1<br />

_geom_angle_a<strong>to</strong>m_site_label_2<br />

_geom_angle_a<strong>to</strong>m_site_label_3<br />

_geom_angle<br />

_geom_angle_site_symmetry_1<br />

_geom_angle_site_symmetry_3<br />

_geom_angle_publ_flag<br />

C7 O1 H1 109.5 . . ?<br />

C3 O2 H2 109.5 . . ?<br />

C4 O3 H3 109.5 . . ?<br />

C5 O4 H4 109.5 . . ?<br />

C6 O5 H5 109.5 . . ?<br />

C8 C1 C6 107.7(4) . . ?<br />

C8 C1 C7 109.0(4) . . ?<br />

C6 C1 C7 108.4(4) . . ?<br />

C8 C1 C2 110.7(4) . . ?<br />

C6 C1 C2 111.3(4) . . ?<br />

C7 C1 C2 109.8(4) . . ?<br />

C3 C2 C9 114.0(4) . . ?<br />

C3 C2 C1 112.9(4) . . ?<br />

C9 C2 C1 113.6(4) . . ?<br />

C3 C2 H2A 105.1 . . ?<br />

C9 C2 H2A 105.1 . . ?<br />

C1 C2 H2A 105.1 . . ?<br />

O2 C3 C4 108.6(4) . . ?<br />

O2 C3 C2 109.0(3) . . ?<br />

C4 C3 C2 111.8(4) . . ?<br />

O2 C3 H3A 109.1 . . ?<br />

C4 C3 H3A 109.1 . . ?<br />

C2 C3 H3A 109.1 . . ?<br />

O3 C4 C5 108.7(4) . . ?<br />

O3 C4 C3 110.3(4) . . ?<br />

C5 C4 C3 112.8(4) . . ?<br />

O3 C4 H4A 108.3 . . ?<br />

C5 C4 H4A 108.3 . . ?<br />

C3 C4 H4A 108.3 . . ?<br />

O4 C5 C4 112.0(4) . . ?<br />

O4 C5 C6 106.4(4) . . ?<br />

C4 C5 C6 111.3(4) . . ?<br />

O4 C5 H5A 109.0 . . ?<br />

C4 C5 H5A 109.0 . . ?<br />

C6 C5 H5A 109.0 . . ?<br />

O5 C6 C5 108.8(4) . . ?<br />

O5 C6 C1 108.1(4) . . ?<br />

C5 C6 C1 112.8(4) . . ?<br />

O5 C6 H6 109.0 . . ?<br />

C5 C6 H6 109.0 . . ?<br />

C1 C6 H6 109.0 . . ?<br />

O1 C7 C1 112.6(4) . . ?<br />

O1 C7 H7A 109.1 . . ?<br />

C1 C7 H7A 109.1 . . ?<br />

O1 C7 H7B 109.1 . . ?<br />

C1 C7 H7B 109.1 . . ?<br />

H7A C7 H7B 107.8 . . ?<br />

C1 C8 H8A 109.5 . . ?<br />

C1 C8 H8B 109.5 . . ?<br />

H8A C8 H8B 109.5 . . ?<br />

C1 C8 H8C 109.5 . . ?<br />

H8A C8 H8C 109.5 . . ?<br />

H8B C8 H8C 109.5 . . ?<br />

C11 C9 C10 109.6(4) . . ?<br />

C11 C9 C2 111.9(4) . . ?<br />

C10 C9 C2 114.1(4) . . ?<br />

C11 C9 H9 106.9 . . ?<br />

C10 C9 H9 106.9 . . ?<br />

332


C2 C9 H9 106.9 . . ?<br />

C9 C10 H10A 109.5 . . ?<br />

C9 C10 H10B 109.5 . . ?<br />

H10A C10 H10B 109.5 . . ?<br />

C9 C10 H10C 109.5 . . ?<br />

H10A C10 H10C 109.5 . . ?<br />

H10B C10 H10C 109.5 . . ?<br />

C9 C11 H11A 109.5 . . ?<br />

C9 C11 H11B 109.5 . . ?<br />

H11A C11 H11B 109.5 . . ?<br />

C9 C11 H11C 109.5 . . ?<br />

H11A C11 H11C 109.5 . . ?<br />

H11B C11 H11C 109.5 . . ?<br />

C18 O6 H6A 109.5 . . ?<br />

C14 O7 H7 109.5 . . ?<br />

C15 O8 H8 109.5 . . ?<br />

C16 O9 H9A 109.5 . . ?<br />

C17 O10 H10 109.5 . . ?<br />

C19 C12 C18 104.8(4) . . ?<br />

C19 C12 C17 107.9(4) . . ?<br />

C18 C12 C17 109.3(4) . . ?<br />

C19 C12 C13 109.6(4) . . ?<br />

C18 C12 C13 114.4(4) . . ?<br />

C17 C12 C13 110.5(4) . . ?<br />

C14 C13 C20 113.4(4) . . ?<br />

C14 C13 C12 111.8(4) . . ?<br />

C20 C13 C12 113.1(4) . . ?<br />

C14 C13 H13 105.9 . . ?<br />

C20 C13 H13 105.9 . . ?<br />

C12 C13 H13 105.9 . . ?<br />

O7 C14 C15 110.4(4) . . ?<br />

O7 C14 C13 113.0(4) . . ?<br />

C15 C14 C13 108.9(4) . . ?<br />

O7 C14 H14 108.1 . . ?<br />

C15 C14 H14 108.1 . . ?<br />

C13 C14 H14 108.1 . . ?<br />

O8 C15 C16 107.8(4) . . ?<br />

O8 C15 C14 110.4(4) . . ?<br />

C16 C15 C14 109.8(4) . . ?<br />

O8 C15 H15 109.6 . . ?<br />

C16 C15 H15 109.6 . . ?<br />

C14 C15 H15 109.6 . . ?<br />

O9 C16 C15 113.0(4) . . ?<br />

O9 C16 C17 111.4(4) . . ?<br />

C15 C16 C17 109.8(4) . . ?<br />

O9 C16 H16 107.5 . . ?<br />

C15 C16 H16 107.5 . . ?<br />

C17 C16 H16 107.5 . . ?<br />

O10 C17 C16 108.3(3) . . ?<br />

O10 C17 C12 109.2(4) . . ?<br />

C16 C17 C12 114.5(4) . . ?<br />

O10 C17 H17 108.2 . . ?<br />

C16 C17 H17 108.2 . . ?<br />

C12 C17 H17 108.2 . . ?<br />

O6 C18 C12 116.7(4) . . ?<br />

O6 C18 H18A 108.1 . . ?<br />

C12 C18 H18A 108.1 . . ?<br />

O6 C18 H18B 108.1 . . ?<br />

C12 C18 H18B 108.1 . . ?<br />

H18A C18 H18B 107.3 . . ?<br />

C12 C19 H19A 109.5 . . ?<br />

C12 C19 H19B 109.5 . . ?<br />

H19A C19 H19B 109.5 . . ?<br />

C12 C19 H19C 109.5 . . ?<br />

H19A C19 H19C 109.5 . . ?<br />

H19B C19 H19C 109.5 . . ?<br />

C21 C20 C22 110.1(4) . . ?<br />

C21 C20 C13 114.4(4) . . ?<br />

C22 C20 C13 110.6(4) . . ?<br />

C21 C20 H20 107.1 . . ?<br />

C22 C20 H20 107.1 . . ?<br />

C13 C20 H20 107.1 . . ?<br />

C20 C21 H21A 109.5 . . ?<br />

C20 C21 H21B 109.5 . . ?<br />

H21A C21 H21B 109.5 . . ?<br />

C20 C21 H21C 109.5 . . ?<br />

333


H21A C21 H21C 109.5 . . ?<br />

H21B C21 H21C 109.5 . . ?<br />

C20 C22 H22A 109.5 . . ?<br />

C20 C22 H22B 109.5 . . ?<br />

H22A C22 H22B 109.5 . . ?<br />

C20 C22 H22C 109.5 . . ?<br />

H22A C22 H22C 109.5 . . ?<br />

H22B C22 H22C 109.5 . . ?<br />

H1S O1S H2S 105(5) . . ?<br />

H3S O2S H4S 101(5) . . ?<br />

loop_<br />

_geom_<strong>to</strong>rsion_a<strong>to</strong>m_site_label_1<br />

_geom_<strong>to</strong>rsion_a<strong>to</strong>m_site_label_2<br />

_geom_<strong>to</strong>rsion_a<strong>to</strong>m_site_label_3<br />

_geom_<strong>to</strong>rsion_a<strong>to</strong>m_site_label_4<br />

_geom_<strong>to</strong>rsion<br />

_geom_<strong>to</strong>rsion_site_symmetry_1<br />

_geom_<strong>to</strong>rsion_site_symmetry_2<br />

_geom_<strong>to</strong>rsion_site_symmetry_3<br />

_geom_<strong>to</strong>rsion_site_symmetry_4<br />

_geom_<strong>to</strong>rsion_publ_flag<br />

C8 C1 C2 C3 167.5(4) . . . . ?<br />

C6 C1 C2 C3 47.9(5) . . . . ?<br />

C7 C1 C2 C3 -72.1(5) . . . . ?<br />

C8 C1 C2 C9 -60.7(5) . . . . ?<br />

C6 C1 C2 C9 179.6(4) . . . . ?<br />

C7 C1 C2 C9 59.6(5) . . . . ?<br />

C9 C2 C3 O2 57.9(5) . . . . ?<br />

C1 C2 C3 O2 -170.5(4) . . . . ?<br />

C9 C2 C3 C4 178.0(4) . . . . ?<br />

C1 C2 C3 C4 -50.4(5) . . . . ?<br />

O2 C3 C4 O3 -62.8(5) . . . . ?<br />

C2 C3 C4 O3 176.8(3) . . . . ?<br />

O2 C3 C4 C5 175.5(4) . . . . ?<br />

C2 C3 C4 C5 55.1(5) . . . . ?<br />

O3 C4 C5 O4 61.1(5) . . . . ?<br />

C3 C4 C5 O4 -176.3(4) . . . . ?<br />

O3 C4 C5 C6 -179.9(4) . . . . ?<br />

C3 C4 C5 C6 -57.3(5) . . . . ?<br />

O4 C5 C6 O5 57.1(5) . . . . ?<br />

C4 C5 C6 O5 -65.2(5) . . . . ?<br />

O4 C5 C6 C1 177.1(4) . . . . ?<br />

C4 C5 C6 C1 54.8(5) . . . . ?<br />

C8 C1 C6 O5 -51.1(5) . . . . ?<br />

C7 C1 C6 O5 -168.9(4) . . . . ?<br />

C2 C1 C6 O5 70.3(5) . . . . ?<br />

C8 C1 C6 C5 -171.5(4) . . . . ?<br />

C7 C1 C6 C5 70.7(5) . . . . ?<br />

C2 C1 C6 C5 -50.1(5) . . . . ?<br />

C8 C1 C7 O1 -66.9(5) . . . . ?<br />

C6 C1 C7 O1 50.0(5) . . . . ?<br />

C2 C1 C7 O1 171.7(4) . . . . ?<br />

C3 C2 C9 C11 -90.4(5) . . . . ?<br />

C1 C2 C9 C11 138.4(4) . . . . ?<br />

C3 C2 C9 C10 34.8(6) . . . . ?<br />

C1 C2 C9 C10 -96.5(5) . . . . ?<br />

C19 C12 C13 C14 167.2(4) . . . . ?<br />

C18 C12 C13 C14 -75.4(5) . . . . ?<br />

C17 C12 C13 C14 48.5(5) . . . . ?<br />

C19 C12 C13 C20 -63.3(5) . . . . ?<br />

C18 C12 C13 C20 54.0(5) . . . . ?<br />

C17 C12 C13 C20 177.9(4) . . . . ?<br />

C20 C13 C14 O7 50.0(5) . . . . ?<br />

C12 C13 C14 O7 179.3(4) . . . . ?<br />

C20 C13 C14 C15 173.1(4) . . . . ?<br />

C12 C13 C14 C15 -57.7(5) . . . . ?<br />

O7 C14 C15 O8 -51.9(5) . . . . ?<br />

C13 C14 C15 O8 -176.5(4) . . . . ?<br />

O7 C14 C15 C16 -170.7(4) . . . . ?<br />

C13 C14 C15 C16 64.7(5) . . . . ?<br />

O8 C15 C16 O9 52.4(5) . . . . ?<br />

C14 C15 C16 O9 172.8(4) . . . . ?<br />

O8 C15 C16 C17 177.4(3) . . . . ?<br />

C14 C15 C16 C17 -62.2(5) . . . . ?<br />

O9 C16 C17 O10 58.0(5) . . . . ?<br />

C15 C16 C17 O10 -67.9(4) . . . . ?<br />

334


O9 C16 C17 C12 -179.9(4) . . . . ?<br />

C15 C16 C17 C12 54.2(5) . . . . ?<br />

C19 C12 C17 O10 -45.1(5) . . . . ?<br />

C18 C12 C17 O10 -158.6(4) . . . . ?<br />

C13 C12 C17 O10 74.7(4) . . . . ?<br />

C19 C12 C17 C16 -166.8(4) . . . . ?<br />

C18 C12 C17 C16 79.8(5) . . . . ?<br />

C13 C12 C17 C16 -46.9(5) . . . . ?<br />

C19 C12 C18 O6 -175.9(4) . . . . ?<br />

C17 C12 C18 O6 -60.4(5) . . . . ?<br />

C13 C12 C18 O6 64.0(5) . . . . ?<br />

C14 C13 C20 C21 34.1(6) . . . . ?<br />

C12 C13 C20 C21 -94.5(5) . . . . ?<br />

C14 C13 C20 C22 -90.9(5) . . . . ?<br />

C12 C13 C20 C22 140.5(4) . . . . ?<br />

loop_<br />

_geom_hbond_a<strong>to</strong>m_site_label_D<br />

_geom_hbond_a<strong>to</strong>m_site_label_H<br />

_geom_hbond_a<strong>to</strong>m_site_label_A<br />

_geom_hbond_distance_DH<br />

_geom_hbond_distance_HA<br />

_geom_hbond_distance_DA<br />

_geom_hbond_angle_DHA<br />

_geom_hbond_site_symmetry_A<br />

O2S H4S O2 0.93(7) 1.84(8) 2.760(5) 171(7)<br />

2_647<br />

O2S H3S O8 0.93(6) 1.91(6) 2.770(4) 153(5)<br />

2_647<br />

O1S H2S O1 0.91(5) 1.81(5) 2.705(5) 167(5)<br />

2_747<br />

O1S H1S O3 0.78(6) 1.99(6) 2.748(5) 163(6) .<br />

O10 H10 O5 0.84 1.89 2.727(4) 171.3 2_647<br />

O9 H9A O1S 0.84 1.83 2.644(5) 162.6 2_657<br />

O8 H8 O9 0.84 1.83 2.628(4) 156.8 2_657<br />

O7 H7 O2S 0.84 2.04 2.867(5) 166.6 1_565<br />

O6 H6A O2S 0.84 1.92 2.756(5) 178.3 .<br />

O5 H5 O1S 0.84 2.09 2.854(5) 151.0 1_565<br />

O4 H4 O3 0.84 2.44 2.849(5) 110.7 .<br />

O3 H3 O8 0.84 1.90 2.705(4) 159.5 .<br />

O2 H2 O10 0.84 1.98 2.808(5) 170.5 2_647<br />

O1 H1 O6 0.84 1.97 2.709(5) 146.8 2_757<br />

_diffrn_measured_fraction_theta_max 0.998<br />

_diffrn_reflns_theta_full 25.02<br />

_diffrn_measured_fraction_theta_full 0.998<br />

_refine_diff_density_max 0.250<br />

_refine_diff_density_min -0.203<br />

_refine_diff_density_rms 0.<br />

335

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