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<strong>Saurashtra</strong> <strong>University</strong><br />
Re – Accredited Grade ‘B’ by NAAC<br />
(CGPA 2.93)<br />
Savaia, Bharat S., 2011, “Synthesis and Characterization of New Heterocyclic<br />
Compounds & Their Application”, thesis PhD, <strong>Saurashtra</strong> <strong>University</strong><br />
http://etheses.saurashtrauniversity.edu/id/eprint/457<br />
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© The Author
Synthesis and Characterization of New<br />
heterocyclic compounds & their<br />
applications<br />
A THESIS SUBMITTED TO<br />
THE SAURASHTRA UNIVERSITY<br />
IN THE FACULTY OF SCIENCE<br />
FOR THE DEGREE OF<br />
Doctor of Philosophy<br />
UNDER THE GUIDANCE OF<br />
PROF. ANAMIK SHAH<br />
DEPARTMENT OF CHEMISTRY<br />
(DST-FIST FUNDED AND UGC-SAP<br />
SPONSORED)<br />
SAURASHTRA UNIVERSITY<br />
RAJKOT – 360 005<br />
GUJARAT (INDIA)<br />
IN<br />
CHEMISTRY<br />
BY<br />
Bharat S. Savalia<br />
UNDER THE CO-GUIDANCE OF<br />
PROF. ERIK VAN DER EYCKEN<br />
LABORATORY FOR ORGANIC &<br />
MICROWAVE-ASSISTED CHEMISTRY<br />
(LOMAC).<br />
DEPARTMENT OF CHEMISTRY,<br />
UNIVERSITY OF LEUVEN<br />
(K.U.LEUVEN), BELGIUM
JANUARY-2011<br />
Statement under O. Ph. D. 7 of <strong>Saurashtra</strong> <strong>University</strong><br />
The work included in the thesis is done by me under the supervision of<br />
Prof. Anamik K. Shah and Co-supervision of Prof. Erik Van der Eycken<br />
and the contribution made thereof is my own work. The work was carried<br />
out at Department of Chemistry, <strong>Saurashtra</strong> <strong>University</strong>, Rajkot under<br />
UGC meritorious Fellowship and at Laboratory for Organic &<br />
Microwave-Assisted Chemistry (LOMAC), Department of Chemistry,<br />
<strong>University</strong> of Leuven (K.U.Leuven), Belgium under Erasmus Mundus<br />
Scholarship.<br />
Date:<br />
Place: Bharat S. Savalia
The Blessed Lord said: Fearlessness, purification of one's existence, cultivation of<br />
spiritual knowledge, charity, self-control, performance of sacrifice, study of the<br />
Vedas, austerity and simplicity; non-violence, truthfulness, freedom from anger;<br />
renunciation, tranquillity, aversion to faultfinding, compassion and freedom from<br />
covetousness; gentleness, modesty and steady determination; vigour, forgiveness,<br />
fortitude, cleanliness, freedom from envy and the passion for honour--these<br />
transcendental qualities, O son of Bharata, belong to godly men endowed with<br />
divine nature.<br />
Bhagvad Gita, Chapter-16, Verses-1-3.<br />
To my Family,<br />
With Love
Acknowledgment<br />
This thesis arose in part out of years of research that has been done since I came to Prof.<br />
Anamik Shah’s group. By that time, I have worked with a great number of people whose<br />
contribution in assorted ways to the research and the making of the thesis deserved special<br />
mention. It is a pleasure to convey my gratitude to them all in my humble acknowledgment.<br />
In the first place I would like to record my gratitude to Prof. ANAMIK SHAH for his<br />
supervision, advice, and guidance from the very early stage of this research as well as giving me<br />
extraordinary experiences through out the work. Above all and the most needed, he provided<br />
me unflinching encouragement and support in various ways. His truly scientific intuition has<br />
made him as a constant oasis of ideas and passions in science, which has exceptionally, inspire<br />
and enrich my growth as a student, a researcher and a scientist want to be. I am indebted to<br />
him for more than he knows.<br />
I gratefully acknowledge My Co-Supervisor Prof. ERIK VAN DER EYCKEN Laboratory<br />
for Organic & Microwave-Assisted Chemistry (LOMAC), Department of Chemistry,<br />
<strong>University</strong> of Leuven (K.U.Leuven), Belgium, for his advice, supervision, and crucial<br />
contribution, which made him a backbone of this research and so to this thesis. His<br />
involvement with his originality has triggered and nourished my intellectual maturity that I<br />
will benefit from, for a long time to come. Erik, I am grateful in every possible way and hope<br />
to keep up our collaboration in the future.<br />
I am very thankful to the faculties of Department of Chemistry namely, Professor and Head<br />
Dr. P.H. Parasaniya, Prof. V. H. Shah, Dr. H. S. Joshi, Dr. Shipra Baluja, Dr. M. K. Shah,<br />
Dr. Yogesh Naliapara, Dr.U.C.Bhoya and Dr. R. C. Khunt for their encouragement and ever<br />
green support.<br />
The Department of Chemistry and LOMAC has provided the support and equipment I have<br />
needed to produce and complete my thesis and the UGC and Erasmus Mundus has funded my<br />
studies. Many Thanks.
Many thanks go in particular to Dr.Denis Ermolet’v. I am much indebted to Denis for his<br />
valuable advice in scientific discussion and synthetic part of this thesis.<br />
To the role model for hard workers in the lab, Dr. Vaibhav Mehta, I would like to thank him<br />
for many reasons. I would also acknowledge Sachin, Rupesh, Ripula, Dipak, Punit, Bari, Jigo,<br />
Nigam, Nick, Prof. BK, and Claudia (Lab Mummy) for their advice and their willingness to<br />
share their bright thoughts with me, which was very fruitful for shaping up my ideas and<br />
research. Thanks to each and every members of LOMAC.<br />
Collective and individual acknowledgments are also owed to my colleagues at <strong>Saurashtra</strong><br />
<strong>University</strong> whose presence somehow perpetually refreshed, helpful, and memorable. Many<br />
thanks go in particular to Vaibhav, Bunty, Ravi, Sailesh, Shrey, Dhiru, Abhay, Bapu, Nilay,<br />
Manisha, Harshad, Ronny, Mrunal, Rakshit, Ashish, Priti, Fatema, Ketaki, Dilip, Pratik,<br />
Vishwa and Paresh. I was extraordinarily fortunate in having Rahul, Matre, Jigo, Bharat,<br />
Suresh, Pankaj, Atul, Raju, Naval, Naimish, Dodia, Ghetiya Satish and Mahesh as my<br />
friends. Thank s to all dear.<br />
To Prashant Shah, thank for giving me the opportunity to work on your O2h in Ahmedabad.<br />
To Cnp, Tusharbhai, Jigo, Pradip, Hemal, Nileshwari, Shabu, PP, Hiral, Tejas, Pareshbhai<br />
and Vikas thank for your technical assistances and fun during the work we had in O2h. It is<br />
also a pleasure to mention.<br />
I am tempted to individually thank all of my friends which, from my childhood until graduate<br />
school, have joined me in the discovery of what is life about and how to make the best of it.<br />
However, because the list might be too long and by fear of leaving someone out, I will simply<br />
say thank you very much to you all.<br />
It is a pleasure to express my gratitude wholeheartedly to Anamik Shah’s family for their kind<br />
hospitality during my stay in Rajkot for Ph.D. Specially thanks to Ranjanmam and Aditya.<br />
Where would I be without my family? My parents deserve special mention for their<br />
inseparable support and prayers. My Father Savdasbhai, in the first place is the person who<br />
put the fundament of my learning character, showing me the joy of intellectual pursuit ever
since I was a child. My Mother Hansaben, is the one who sincerely raised me with her caring<br />
and gently love. My special gratitude is due to my dadi, my brother Kalpesh, Bhabhi<br />
Jayshreeben, my sisters Manisha, Jiju Rajnibhai, Sweet Miral, Mahek, Nancy, & Man, my<br />
uncle Manshukhbhai and his family for their loving support.<br />
Words fail me to express my appreciation to my wife Trupti whose dedication, love and<br />
persistent confidence in me, has taken the load off my shoulder. I owe her for being unselfishly<br />
let her intelligence, passions, and ambitions collide with mine. Therefore, I would also thank<br />
Tupi’s family for letting me take her hand in marriage, and accepting me as a member of the<br />
family, warmly. Furthermore, to Sorathiya family with their thoughtful support, thank you.<br />
I would like to thank everybody who was important to the successful realization of thesis, as<br />
well as expressing my apology to those whose name I could not mention individually.<br />
Finally, I bow my head before almighty GOD, who has inspired ME in each and every stage<br />
of my life.<br />
BHARAT SAVALIA
CONTENTS<br />
CHAPTER – 1<br />
Microwave Assisted Organic Synthesis<br />
1. Microwave Assisted Organic Synthesis 1<br />
1.1 Introduction 1<br />
1.2 Microwave Frequency 2<br />
1.3 Principle 2<br />
1.4 Heating Mechanism 3<br />
1.4.1 Dipolar Polarisation 3<br />
1.4.2. Conduction Mechanism 4<br />
1.5 Effects of solvents 5<br />
1.6 Conventional vs Microwave Heating 6<br />
1.7 Application of microwave in organic synthesis 7<br />
1.8 Studies on 2-Aminoimidazoles 8<br />
1.9 2-Aminoimidazole Alkaloids 11<br />
1.10 Methods for the preparation of 2-aminoimidazoles 15<br />
1.11 The 2-Aminoimidazole as a Pharmacophore 21<br />
1.11.1 Antibiotics Activity 21<br />
1.11.2 Sodium Hydrogen Exchanger-1 (NHE-1) Antagonists. 22<br />
1.11.3 Anti HIV Activity 22<br />
1.11.4 α-adrenoreceptor agonists. 24<br />
1.11.5 Anti Cancer Activity 24<br />
1.11.6 BACE-1 Inhibitors 25<br />
1.11.7 Anti Biofilm Activity 26<br />
1.12 Introduction to Biofilm 29<br />
1.12.1 Properties of biofilms 30<br />
1.12.2 Biofilm Growth Cycle 31<br />
1.12.3 Biofilm Drug Resistance 31<br />
1.13 Recent Publications on 2-aminoimidazoles 33<br />
1.14 Conclusion 33<br />
1.15 References 34
CHAPTER – 2<br />
Microwave Assisted Synthesis & Structure Activity Relationship of 2-Hydroxy-2phenyl-2,3-dihydro-imidazo[1,2-a]pyrimidinium<br />
Salts and 2N-Substituted 4(5)-<br />
Phenyl-2-Amino-1H-imidazoles as Inhibitors of the Biofilm Formation by<br />
Salmonella Typhimurium and Pseudomonas aeruginosa<br />
2.1 Introduction 40<br />
2.2 Reaction scheme 41<br />
2.3 Proposed Mechanism 42<br />
2.4 Results and discussion 43<br />
2.5 Biofilm activity 50<br />
2.5.1 2N-substituted 2-aminopyrimidines 48<br />
2.5.2 2-hydroxy-2,3-dihydro-imidazopyrimidinium salts 48<br />
2.5.2.1 n-Alkyl or iso-alkyl substituents at 1-position 48<br />
2.5.2.2 Further Modification in the most active core structure 51<br />
2.5.2.3 Cyclo-alkyl substituents at 1-position 53<br />
2.5.3 2N-substituted 2-aminoimidazoles 54<br />
2.6 Conclusion 56<br />
2.7 Experimental 57<br />
2.8 Biological Assays 58<br />
2.9 Experimental Protocols 60<br />
2.10 Spectral Characterization 62<br />
2.11 Representative NMR spectra 87<br />
2.12 References 90<br />
CHAPTER – 3<br />
Structure Activity Relationship of N1-Substituted 2-Aminoimidazoles as<br />
Inhibitors of Biofilm Formation by Salmonella Typhimurium and Pseudomonas<br />
aeruginosa<br />
3.1 Introduction 93<br />
3.2 Reaction scheme 94<br />
3.3 Proposed Mechanism 95<br />
3.4 Results and discussion 96
3.5 Biofilm activity 98<br />
3.5.1 N1-alkyl 2-aminoimidazoles 99<br />
3.5.2 Further Modification in the most active core structure 102<br />
3.5.3 Cyclo-alkyl 2-aminoimidazoles 104<br />
3.6 Conclusion 106<br />
3.7 Experimental 107<br />
3.8 Experimental protocols 108<br />
3.9 Spectral Characterization 109<br />
3.10 Representative NMR spectra 122<br />
3.11 References 124<br />
CHAPTER – 4<br />
Copper Catalyzed Microwave Assisted One Pot Synthesis of 2-Aminoimidazole-<br />
Triazole Framework via Dimorth Rearrangement and Click Reaction.<br />
4.1 Introduction 127<br />
4.2 Optimization Study 128<br />
4.3 Results and discussion 130<br />
4.4 Possible Mechanism 133<br />
4.5 Conclusion 134<br />
4.6 Experimental 134<br />
4.7 Experimental Protocols 135<br />
4.8 Spectral Characterization 136<br />
4.9 Representative NMR spectra 149<br />
4.10 References 151<br />
CHAPTER – 5<br />
Synthesis, Characterization, Crystal and molecular structure analysis of DP-7: A<br />
new Multi Drug Resistance Reverter Lead Molecule<br />
5.1 Introduction 154<br />
5.2 Reaction Scheme 155<br />
5.3 Method of crystallization 155<br />
5.4 Crystal structure determination 155
5.5 Results and discussion 156<br />
5.6 Conclusion 160<br />
5.7 Experimental 161<br />
5.8 Spectral Characterization 161<br />
5.9 Representative NMR spectra 163<br />
5.10 References 165<br />
SUMMARY<br />
CONFERENCES/SEMINARS/WORKSHOPS ATTENDED<br />
LIST OF PUBLICATIONS
Abbreviations<br />
Ac Acetyl<br />
2-AI 2-aminoimidazole<br />
aq Aqueous<br />
Boc tert-butyloxycarbonyl<br />
n-BuLi n-butyllithium<br />
t-BuOK potassium tert-butoxide<br />
Cbz Benzyloxycarbonyl<br />
CI chemical ionization<br />
m-CPBA m-chloroperoxybenzoic acid<br />
DAST diethylaminosulfur trifluoride<br />
DBBA 5,5-dibromobarbituric acid<br />
DCM Dichloromethane<br />
DIBAL diisobutylaluminium hydride<br />
DIEA Diisopropylethylamine<br />
DIPA Diisopropanolamine<br />
DMAP 4-dimethylaminopyridine<br />
DMF Dimethylformamide<br />
DMSO dimethyl sulfoxide<br />
EDCI 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide<br />
ESI electrospray ionization<br />
equiv Equivalent<br />
h Hour<br />
HMBC heteronuclear multiple bond correlation<br />
HRMS high resolution mass spectrometry<br />
LAH lithium aluminium hydride<br />
MAOS microwave-assisted organic synthesis<br />
MeCN Acetonitrile<br />
min Minute<br />
MS mass spectrometry
Ms Mesyl<br />
MW Microwave<br />
NBS N-bromosuccinimide<br />
NCS N-chlorosuccinimide<br />
NMM N-methylmorpholine<br />
NOESY nuclear Overhauser effect spectroscopy<br />
PCC pyridinium chlorochromate<br />
Pd Palladium<br />
Pd2(dba)3<br />
tris(dibenzylideneacetone)dipalladium<br />
PDC pyridinium dichromate<br />
PPA polyphosphoric acid<br />
rt room temperature<br />
SPOS solid-phase organic synthesis<br />
TBDMS tert-butyldimethylsilyl<br />
TBDPS tert-butyldiphenylsilyl<br />
TEA Triethylamine<br />
TFA trifluoroacetic acid<br />
THF Tetrahydrofuran<br />
TLC thin layer chromatography<br />
TMS Tetramethylsilane<br />
Ts Tosyl<br />
W Watt
Microwave Assisted Organic<br />
Synthesis
1. Microwave Assisted Organic Synthesis:<br />
1.1 Introduction<br />
Synthesis of new chemical entities is major bottleneck in drug discovery.<br />
Conventional methods for various chemical synthesis is very well documented and<br />
practiced. 1 The methods for synthesis (Heating process) of organic compounds has<br />
continuously modified from the decade. In 1855, Robert Bunsen invented the burner<br />
which acts as energy source for heating a reaction vessel, this was latter superseded<br />
by isomental, oil bath or hot plate, but the drawback of heating, though method<br />
remain the same. Microwave Assisted Organic Synthesis (MAOS), which has<br />
developed in recent years, has been considered superior to traditional heating.<br />
Microwave assisted organic synthesis 2 (MAOS) has emerged as a new “lead” in<br />
organic synthesis. The technique offers simple, clean, fast, efficient, and economic for<br />
the synthesis of a large number of organic molecules. In the recent year microwave<br />
assisted organic reaction has emerged as new tool in organic synthesis. Important<br />
advantage of this technology include highly accelerated rate of the reaction,<br />
Reduction in reaction time with an improvement in the yield and quality of the<br />
product. Now day’s technique is considered as an important approach toward green<br />
chemistry, because this technique is more environmentally friendly. This technology<br />
is still under-used in the laboratory and has the potential to have a large impact on the<br />
fields of screening, combinatorial chemistry, medicinal chemistry and drug<br />
development. Conventional method of organic synthesis usually need longer heating<br />
time, tedious apparatus setup, which result in higher cost of process and the excessive<br />
use of solvents/ reagents lead to environmental pollution. This growth of green<br />
chemistry holds significant potential for a reduction of the by product, a reduction in<br />
waste production and a lowering of the energy costs. Due to its ability to couple<br />
directly with the reaction molecule and by passing thermal conductivity leading to a<br />
rapid rise in the temperature, microwave irradiation has been used to improve many<br />
organic syntheses.
1.2 Microwave frequency<br />
Microwave heating refers the use of electromagnetic waves ranges from 0.01m to 1m<br />
wave length of certain frequency to generate heat in the material. These microwaves<br />
lie in the region of the electromagnetic spectrum between millimeter wave and radio<br />
wave i.e. between I.R and radio wave. They are defined as those waves with<br />
wavelengths between 0.01metre to 1meter, corresponding to frequency of 30GHz to<br />
0.3GHz.<br />
1.3 Principle<br />
The basic principle behind the heating in microwave oven is due to the interaction of<br />
charged particle of the reaction material with electro magnetic wavelength of<br />
particular frequency. The phenomena of producing heat by electromagnetic<br />
irradiation are ether by collision or by conduction, some time by both.<br />
All the wave energy changes its polarity from positive to negative with each cycle of<br />
the wave. This cause rapid orientation and reorientation of molecule, which cause<br />
heating by collision. If the charge particles of material are free to travel through the<br />
material (e.g. Electron in a sample of carbon), a current will induce which will travel<br />
in phase with the field. If charge particle are bound within regions of the material, the<br />
electric field component will cause them to move until opposing force balancing the<br />
electric force. 3-9
1.4 Heating Mechanism<br />
In microwave oven, material may be heated with use of high frequency<br />
electromagnetic waves. The heating arises from the interaction of electric field<br />
component of the wave with charge particle in the material. Two basic principal<br />
mechanisms involve in the heating of material<br />
1.4.1 Dipolar Polarisation<br />
Dipolar polarisation is a process by which heat is generated in polar molecules. On<br />
exposure to an oscillating electromagnetic field of appropriate frequency, polar<br />
molecules try to follow the field and align themselves in phase with the field.<br />
However, owing to inter-molecular forces, polar molecules experience inertia and are<br />
unable to follow the field. This results in the random motion of particles, and this<br />
random interaction generates heat. Dipolar polarisation can generate heat by either<br />
one or both the following mechanisms:<br />
1. Interaction between polar solvent molecules such as water, methanol and ethanol<br />
2. Interaction between polar solute molecules such as ammonia and formic acid<br />
The key requirement for dipolar polarisation is that the frequency range of the<br />
oscillating field should be appropriate to enable adequate inter -particle interaction. If<br />
the frequency range is very high, inter-molecular forces will stop the motion of a<br />
polar molecule before it tries to follow the field, resulting in inadequate inter-particle<br />
interaction. On the other hand, if the frequency range is low, the polar molecule gets<br />
sufficient time to align itself in phase with the field. Hence, no random interaction<br />
takes place between the adjoining particles. Microwave radiation has the appropriate<br />
frequency (0.3-30 GHz) to oscillate polar particles and enable enough inter-particle<br />
interaction. This makes it an ideal choice for heating polar solutions.<br />
In addition, the energy in a microwave photon (0.037 kcal/mol) is very low, relative<br />
to the typical energy required to break a molecular bond (80-120 kcal/mol).<br />
Therefore, microwave excitation of molecules does not affect the structure of an<br />
organic molecule, and the interaction is purely kinetic.
1.4.1. a Interfacial Polarization<br />
Interfacial polarization is an effect, which is very difficult to treat in a simple manner,<br />
and easily viewed as combination of the conduction and dipolar polarization effects.<br />
This mechanism is important for system where a dielectric material is not<br />
homogenous, but consists of conducting inclusion of one dielectric in other.<br />
1.4.2. Conduction mechanism<br />
The conduction mechanism generates heat through resistance to an electric current.<br />
The oscillating electromagnetic field generates an oscillation of electrons or ions in a<br />
conductor, resulting in an electric current. This current faces internal resistance, which<br />
heats the conductor.<br />
The main limitation of this method is that it is not applicable for materials that have<br />
high conductivity, since such materials reflect most of the energy that falls on them.
1.5. Effects of solvents<br />
Every solvent and reagent will absorb microwave energy differently. They each have<br />
a different degree of polarity within the molecule, and therefore, will be affected<br />
either more or less by the changing microwave field. A solvent that is more polar, for<br />
example, will have a stronger dipole to cause more rotational movement in an effort<br />
to align with the changing field. A compound that is less polar, however, will not be<br />
as disturbed by the changes of the field and, therefore, will not absorb as much<br />
microwave energy. Unfortunately, the polarity of the solvent is not the only factor in<br />
determining the true absorbance of microwave energy, but it does provide a good<br />
frame of reference. Most organic solvents can be broken into three different<br />
categories: low, medium, or high absorber, as shown in Figure 6. The low absorbers<br />
are generally hydrocarbons while the high absorbers are more polar compounds, such<br />
as most alcohols.<br />
Absorbance level Solvents<br />
High<br />
Medium<br />
Low<br />
DMSO, EtOH, MeOH, Propanols,<br />
Nitobenzen,<br />
Glycol<br />
Formic Acid, Ethylene<br />
Water, DMF, NMP, Butanol,<br />
Acetonitrile, HMPA, Methy Ethyl<br />
Ketone, Acetone, Nitromethane,<br />
Dichlorobenzene, 1,2-Dichloroethane,<br />
Acetic Acid, trifluoroacetic Acid,<br />
Chloroform, DCM, Carbon tetrachloride,<br />
1,4-Dioxane, Ethy Acetate, Pyridine,<br />
Triethyamine, Toluene, Benzene,<br />
Chlorobenzene, Pentane, Nexane and<br />
other hydrocarbons
1.6 Conventional vs Microwave Heating<br />
Microwave heating is different from conventional heating in many respects. The<br />
mechanism behind microwave Synthesis is quite different from conventional<br />
synthesis. Points enlisted in Table 1, differ the microwave heating from conventional<br />
heating. 10-26<br />
No CONVENTIONAL MICROWAVE<br />
1<br />
2<br />
3<br />
4<br />
5<br />
6<br />
7<br />
Reaction mixture heating proceeds<br />
from a surface usually inside surface of<br />
reaction vessels<br />
The vessel should be in physical<br />
contact with surface source that is at a<br />
higher temperature source (e.g. mental,<br />
oil bath, steam bath etc.)<br />
By thermal or electric source heating<br />
take place.<br />
Heating<br />
conduction<br />
mechanism involve-<br />
Transfer of energy occur from the wall,<br />
surface of vessel, to the mixture and<br />
eventually to reacting species<br />
In conventional heating, the highest<br />
temperature (for a open vessels) that<br />
can be achieved is limited by boiling<br />
point of particular mixture.<br />
In the conventional heating all the<br />
compound<br />
equally<br />
in mixture are heated<br />
Reaction mixture heating proceeds<br />
directly inside mixture<br />
No need of physical contact of<br />
reaction with the higher temperature<br />
source. While vessel is kept in<br />
microwave cavities.<br />
By electromagnetic wave heating take<br />
place.<br />
Heating mechanism involvedielectric<br />
polarization and conduction<br />
The core mixture is heated directly<br />
while surface (vessel wall) is source<br />
of loss of heat<br />
In microwave, the temperature of<br />
mixture can be raised more than its<br />
boiling point i.e. superheating take<br />
place<br />
In microwave, specific component<br />
can be heated specifically.<br />
8 Heating rate is less Heating rate is several fold high
1.7 Application of microwave in organic synthesis<br />
Following reactions have been performed through microwave heating.<br />
Sr. Reaction Ref. Sr Reaction Ref.<br />
1 Acetylation reaction 27 18 Diel’s-Alder reaction 44<br />
2 Addition reaction 28 19 Dimerization reaction 45<br />
3 Alkylation reaction 29 20 Elimination reaction 28<br />
4 Alkynes metathesis 30 21 Estrification reaction 46<br />
5 Allylation reaction 31 22 Enantioselective reaction 47<br />
6 Amination reaction 32 23 Halogenation reaction 48<br />
7<br />
Aromatic nucleophillic<br />
substitution reaction<br />
33 24 Hydrolysis reaction 59<br />
8 Arylation reaction 34 25 Mannich reaction 50<br />
9 Carbonylation reaction 35 26 Oxidation reaction 51<br />
10 Combinatorial reaction 36 27 Phosphorylation synthesis 52<br />
11 Condensation reaction 37 28 Polymerization reaction 53<br />
12 Coupling reaction 38 29 Rearrangement reaction 54<br />
13 Cyanation reaction 39 30 Reduction reaction 55<br />
14 Cyclization reaction 40 31 Ring closing synthesis 56<br />
15 Cyclo-addition reaction 41 32 Solvent free reaction 57<br />
16 Deacetylation reaction 42 33 Transestrification reaction 46<br />
17 Dehalogenation reaction 43 34 Transformation reaction 58<br />
Figure 1.2: General View of Monomode CEM Discover (left) and Multimode<br />
MILESTONE Start (right) Systems
1.8 Studies on 2-Aminoimidazoles<br />
Much effort has been dedicated to the study of molecular architecture and its<br />
relationship to biological activity. From decades of high throughput screening of both<br />
natural and synthetic small molecules we have clued in on structural features that<br />
impart a high probability of biological efficacy. 59 Recently natural products have<br />
enjoyed a renaissance in lead generation for discovery based research. This realization<br />
has further been folded into the concept of Biology-oriented synthesis (BIOS) which<br />
relies on the core structures of natural products as valuable pre-validated scaffolds. 60<br />
These so-called “privileged” pharmacophores are often the basis of synthetic<br />
collections aimed at increasing the success rate of small molecule screening ventures.<br />
In particular, marine natural products derived from sponges have provided valuable<br />
leads for therapeutic small molecules. 61-62 Surprisingly the large majority of these<br />
compounds have been isolated from organisms of the class Dermospongiae. In the<br />
mid 1980’s chemists noted that the other major sponge class, Calcarea, had rarely<br />
been subject to chemical investigations. A flurry of efforts through the mid-1990’s<br />
helped to establish biogenetic relationships among these sponges. Isolated to explore<br />
these interconnections and not necessarily for specific biological responses the<br />
activities of these natural products have remained largely uncovered. Since these<br />
initial investigations, an emerging structural class has recurrently been identified<br />
through bioassay guided isolation which contains the 2-aminoimidazole core. From<br />
the viewpoint of small molecule discovery this review will highlight alkaloids isolated<br />
from Leucetta sp. This small skeletal family has been shown to interrogate an<br />
incredibly diverse range of biological processes and thus represents an important<br />
discovery scaffold for both medicinal and discovery based research.<br />
In 1958, a nitrogen rich antibiotic, consequently named azomycin, was isolated from a<br />
presumptive Streptomyces sp. 63 This new antibiotic displayed good antimicrobial<br />
activity against B. subtilis (6 μg/mL) and E. coli (25 μg/mL) and was relatively well<br />
tolerated in mice (LD50 = 80 mg/kg). Eventually the structure of azomycin was<br />
revealed to be 2-nitroimidazole (2) 64 , which along with its synthetic derivative<br />
metronidiazole (3) have become clinically relevant antiprotozoal therapeutics (Fig.<br />
1.8.1). 65 With the parallel observation that several microbes were able to oxidize
aromatic amines, Lancini’s group showed some Streptomyces species are able to<br />
oxidize 2-aminoimidazole itself, along with a series of 4-alkyl-2-aminoimidazoles, to<br />
their corresponding 2-nitroimidazoles. 66 This suggested that the 2-aminoimidazole<br />
might be the direct biosynthetic precursor to azomycin and in 1970 Okami’s group<br />
isolated the parent heterocycle (1) from Streptomyces eurocidicus. 67 This study also<br />
showed that supplementing the growth medium with L-Arg substantially increased the<br />
production of 1, suggesting that arginine catabolism is critical to its biosynthesis. It is<br />
unknown whether a similar pathway exists in marine organisms that produce more<br />
complex 2-aminoimidazoles, however 1 has been discovered in sponges of the family<br />
Halicondriidae. 68<br />
L-Arg<br />
N<br />
NH<br />
NH 2<br />
N<br />
NH<br />
NO 2<br />
N<br />
NO 2<br />
1 2<br />
Me<br />
3<br />
2-Aminoimidazole Azomycin Metronidazole<br />
Fig.1.8.1 Biosynthetic transformations of 2-aminoimidazole.<br />
Studies on azomycin’s (2) and metronidazole’s (3) mechanism of action have<br />
revealed that the nitro group is reduced in vivo to the nitroso radical which is<br />
responsible for its selective anaerobic antiprotozoal activity. 69 Subsequent studies<br />
have shown that hypoxic conditions in tumors are also capable of reducing the 2nitorimidazole,<br />
prompting it to serve as an important prodrug for 2-aminoimidazoles<br />
in hypoxic environments. 70-72<br />
The ambivalent reactivity of the key structural motif 2-amino-1H-imidazole (4) is<br />
responsible for the molecular diversity observed in this group of alkaloids. The<br />
electrophilic or nucleophilic reactivity at the same position C-4(5) is dependent on the<br />
tautomeric isomer involved (Scheme 1.8.1). 73<br />
NH 2<br />
HN N<br />
5<br />
nucleophilic<br />
position<br />
NH<br />
2<br />
3 1<br />
H N N H<br />
4 5<br />
4<br />
NH 2<br />
N N<br />
5<br />
electrophilic<br />
position<br />
Scheme-1.8.1 The Tautomerism and Ambivalent Reactivity of 2-<br />
Aminoimidazole<br />
N<br />
OH
It is understood that the 2-aminoimidazole occupies an important region of chemical<br />
space as its hydrogen bond donor-acceptor pattern is capable of recreating that of the<br />
guanidine. 74 More importantly, it occupies a unique pKa range between the more<br />
acidic 2-aminopyridinium ion 75 and less acidic guanidinium ion 76 (Fig.1.8.2).<br />
Furthermore, the pKa’s of 2-aminoimidazolium ions show a predictable trend with<br />
substitution, allowing it to be finely tuned for medicinal applications as illustrated in<br />
the examples below. 77<br />
2-Aminopyridine 2-aminobenzimidazole<br />
H<br />
N<br />
N NH 2 N<br />
pK a = 6.71 7.18<br />
N<br />
NH 2<br />
NH<br />
2-aminoimidazole<br />
Me<br />
N<br />
NH 2<br />
NH<br />
Me<br />
N<br />
NH 2<br />
pK a = 8.46 8.65 9.21<br />
HN NH 2 HN<br />
NH 2<br />
Me<br />
NH<br />
amidine guanidine<br />
NH 2<br />
pK a = 12.4 13.4<br />
NH 2<br />
Fig.1.8.2 pKa’s of common guanidine mimetics<br />
This dramatic difference in the pKa of 2-aminoimidazoles (~4 pKa units) with that of<br />
guanidine has led to some debate concerning the ability of the 2-aminoimidazole to<br />
directly mimic a guanidine. These arguments, based on a lowered pKa and electronic<br />
dissimilarity are, however, precisely what makes the 2-aminoimidazole a unique<br />
guanidine mimic for medicinal chemistry.- 77-78 Most importantly, their pKa range<br />
(pKa ~7-9) allows a significant fraction of compound to be uncharged at<br />
physiological pH thus increasing the likelihood of cellular penetration. It also permits<br />
this unique heterocycle to cross the blood brain barrier and may decrease the<br />
susceptibility of these compounds to Pgp mediated efflux vide infra. 79
1.9 2-Aminoimidazole Alkaloids<br />
The 2-aminoimidazole framework is emerging as an important pharmacophore, 80 and<br />
is widely found in numerous biologically active marine alkaloids. Over the last 25<br />
years, several hundreds of diverse 1-unsubstituted and 1-substituted 2aminoimidazoles<br />
have been characterized. 1-Unsubstituted 2-aminoimidazole<br />
alkaloids (Fig. 1.9.1) have been isolated essentially from various species of marine<br />
sponges (Phylum Porifera) of Caribbean and South Atlantic regions. 81 Oroidin (1) and<br />
the dimeric sceptrin (3) are the most abundant members of the pyrrole-imidazole<br />
family.<br />
H 2N<br />
H 2N<br />
H 2N<br />
N<br />
N<br />
H<br />
H<br />
N<br />
N<br />
N<br />
Oroidin (1)<br />
HN<br />
O<br />
HN<br />
N<br />
H<br />
O<br />
Sceptrin (3)<br />
H N<br />
HN<br />
H2N HO<br />
N<br />
N<br />
H<br />
HN<br />
N<br />
H<br />
H2N Cl<br />
Palau'amine<br />
(5)<br />
H<br />
N<br />
HN<br />
O<br />
NH 2<br />
O<br />
N<br />
H<br />
N<br />
H<br />
Br<br />
Br<br />
Br<br />
Br<br />
H 2N<br />
N<br />
H<br />
N<br />
HO<br />
O<br />
H 2N<br />
H 2N<br />
Me<br />
HN<br />
H<br />
N<br />
N<br />
N<br />
H<br />
HN<br />
N<br />
N<br />
H<br />
Cl<br />
N<br />
H<br />
OH<br />
Girolline (2)<br />
N<br />
Br<br />
Br<br />
Ageladine A (4)<br />
O<br />
NH 2<br />
NH<br />
Dragmacidin E (6)<br />
Fig.1.9.1 Some representative 1-unsubstituted 2-aminoimidazoles from marine<br />
sponges.<br />
Br
In turn, most of the 1-substituted 2-aminoimidazole alkaloids (Figure 1.9.2) have been<br />
isolated from the Calcarea group of the genera Leucetta and Clathrina from the Red<br />
Sea and the Indo-Pacific regions. 82<br />
N<br />
H2N N<br />
Me<br />
HO<br />
OH<br />
Naamine A (7)<br />
OMe<br />
OMe<br />
OMe<br />
N<br />
H2N N O OMe<br />
Me<br />
Calcaridine A (9)<br />
N<br />
OH<br />
H2N N<br />
OMe<br />
Me<br />
Kealiinine A (11)<br />
H 2N<br />
N<br />
N<br />
OH<br />
Isonaamine A (8)<br />
N<br />
H2N N<br />
Me O<br />
O<br />
O<br />
OH<br />
O<br />
Leucettamine A (10)<br />
N<br />
H2N N<br />
Me O<br />
O<br />
Preclathridine A (12)<br />
Fig.1.9.2 Some representative 1-substituted 2-aminoimidazoles from<br />
marine sponges.<br />
Both classes of 1-substituted and 1-unsubstituted 2-aminoimidazoles possess<br />
interesting biological properties. Due to their high cytotoxicity many polysubstituted<br />
2-aminoimidazole alkaloids are involved in chemical defense of marine sponges<br />
against predators, in the prevention of the settlement of fouling and pathogenic<br />
microorganisms or in the suppression of epibiotic bacteria and spatial competition.
Recently group of Erik 83 described a novel, short and efficient synthesis of diverse 2aminoimidazoles<br />
from readily available polysubstituted secondary propargylamines<br />
and thioureas (Scheme-1.9.1). Both the guanylation and the cyclization steps can be<br />
carried out either in a stepwise manner with a carbodiimide activator and an AgI<br />
catalyst or in a one-pot process with a recoverable AgI salt as a promoter and catalyst.<br />
This protocol was successfully applied to the total synthesis of all trisubstituted 2aminoimidazole<br />
naamine alkaloids. Furthermore, we demonstrated the potential of<br />
polysubstituted 2-aminoimidazoles as inhibitors of bacterial biofilm formation.<br />
R 1<br />
R 2<br />
R 3<br />
R 4<br />
Me<br />
CHO<br />
N<br />
H<br />
Boc<br />
N<br />
N<br />
Boc N<br />
Me<br />
N<br />
H2N N<br />
Me<br />
R 1<br />
R 1<br />
allyl<br />
R 5<br />
R 2<br />
R 4<br />
R 3<br />
1) TFA/DCM<br />
RT, 3h<br />
2) H2-Pd/C<br />
MeOH, RT<br />
R 5<br />
R 2<br />
R 4<br />
R 3<br />
R 5<br />
CuBr (10 mol %)<br />
100 oC, MW<br />
Toluene, 25 min<br />
6a<br />
AgNO3 (1.4 equiv)<br />
Et3N (2 equiv)<br />
MeCN, RT, 5 min<br />
Scheme 1.9.1 Short total synthesis of alkaloid of the naamine family<br />
R 1<br />
R 2<br />
R 1<br />
R 2<br />
R 3<br />
R 3<br />
R 4<br />
R 5<br />
N(Me)Allyl<br />
[Pd(PPh3) 4] (5 mol%)<br />
DMBA (3.5 equiv)<br />
DCM, Reflux, 25 min<br />
R 4<br />
NH(Me)<br />
R 5
Pierre Potier proposed biogenetic scheme, various hypothetical constituents can be<br />
predicted. It is clear that the above chemical pathway suggests that these compounds<br />
may be more widespread than presently known. The isolation and characterisation of<br />
new pyrrole-imidazole metabolites will certainly allow us to explore additional<br />
transformations which could support this hypothesis. As chemical diversity,<br />
enzymatic catalysis variation and mutagenesis are closely related, the ‘‘prebiotic<br />
chemistry’’ presented here can also provide strong evidence for a multifunctional<br />
enzyme-mediated biosynthesis. Such multiprotein systems would be particularly<br />
needed by the living fixed sponges for their adaptation to environmental influences,<br />
and for self-defence.<br />
Fig.1.9.3 Arrangement of all known oroidin alkaloids in structural groups.
1.10 Methods for the preparation of 2-aminoimidazoles<br />
Several methods for the formation of 2-aminoimidazoles are known with widely<br />
differing degrees of synthetic utility, but no current method as of yet has a broad<br />
range of applicability in complex molecule synthesis. Harsh reaction conditions<br />
and/or synthetically difficult and labile precursors are often required for such task.<br />
The methods to prepare 2-aminoimidizoles may be categorized into four main classes:<br />
1) Condensation reactions,<br />
2) Ambivalent addition of 2-aminoimidazole,<br />
3) Direct formation of C-N bond.<br />
4) Heterocyclic exchange reactions.<br />
Functionalized 2-aminoimidazoles can show a wide range of stability issues, the free<br />
base of many substrates is susceptible to nucleophilic or base mediated degredation.<br />
This instability has thus far precluded a unified strategy to access this heterocycle, but<br />
the variety of methods can often lead to success in a complex molecule setting.<br />
1.10.1 Condensations<br />
By far the most common way to prepare the 2-aminoimidazoles originates with the<br />
condensation of α-amino or α -haloketone with cyanamide or a guanidine derivative,<br />
respectively. This strategy was first disclosed by Norris and McKee who explored the<br />
condensation of α -aminoacetophenones with N-cyanoguanidines (scheme-1.10.1). 84<br />
Cl<br />
O<br />
NH 2.HCl<br />
NC<br />
N<br />
H<br />
NH<br />
Scheme-1.10.1 Norris and McKee‘s condensation.<br />
N<br />
R 2<br />
R 1<br />
150-200 o C<br />
Subsequently Lawson was able to show that aminoacetaldehyde diethylacetal can<br />
undergo acid catalyzed addition to cyanamide giving the masked guanidine<br />
acetaldehyde (Scheme-1.10.2). 85<br />
Cl<br />
N<br />
NH<br />
HN<br />
NH<br />
N<br />
R 1<br />
R 2
EtO<br />
OEt<br />
NH 2CN<br />
NH 2<br />
AcOH<br />
EtO<br />
OEt<br />
Scheme-1.10.2 Lawson’s synthesis.<br />
H<br />
N<br />
NH<br />
NH 2<br />
HCl<br />
H 2O<br />
N<br />
H<br />
N<br />
NH 2.HCl<br />
Kruetzberger found that condensation of 1,2-hydrazinedicarboxamidine with benzoin<br />
derivatives in alkali media will yield symmetrically substituted azoimidazoles after<br />
spontaneous oxidation of the bis-imidazolhydrazine (Scheme-1.10.3). 86 Reductive<br />
cleavage of the azo group by hydrogenolysis gives two mole equivalents of the 2aminoimidazole.<br />
This methodology is useful but limited to the preparation of 4,5diaryl<br />
substituted 2-aminoimidazoles.<br />
H 2N<br />
HN<br />
HN NH<br />
NH<br />
NH 2<br />
Ar<br />
O<br />
OH<br />
Ar<br />
NaOH<br />
Scheme-1.10.3 Kruetzberger’s condensation.<br />
Ar<br />
In 1966, Lancini and Lazzari successfully expanded Lawson’s strategy to include α -<br />
aminoketones, including the use of N-alkylamines (Scheme-1.10.4). 87-88 They were<br />
the first to observe the strict pH dependence of this condensation. At very low pH the<br />
cyanamide is quickly converted to urea. At high pH, dimerization of the aminoketone<br />
to the piperazine competes with cyanamide condensation. Having established the<br />
optimum pH of the reaction to be ~4.5, these conditions are now routinely adopted. In<br />
1925 Pyman and Burtles had reported the reaction of α-bromoacetone and guanidine<br />
to give a mixture of uncharacterizable compounds, leading them to abandon this<br />
approach and develop their diazonium coupling described below. 89 Seventy years<br />
later, Weber discovered that N-acetylguanidine smoothly undergoes displacement and<br />
condensation with α -haloketones and aldehydes. 90<br />
O<br />
H<br />
N<br />
NH 2CN<br />
pH = 4.5<br />
N<br />
N<br />
N<br />
NH<br />
Ar<br />
HN<br />
N<br />
N<br />
Ar<br />
N<br />
Ar<br />
NH 2<br />
H 2<br />
Pd/C<br />
Scheme-1.10.4 Lancini and Lazzari’s expanded strategy<br />
Ph<br />
Ar<br />
HN<br />
Ar<br />
N<br />
NH 2
R 1<br />
O<br />
X<br />
R 2<br />
NH 2<br />
H 2N NAc<br />
R 1<br />
HN<br />
R 2<br />
N<br />
NHAc<br />
NH 2NH 2<br />
OR<br />
H 2SO 4<br />
Scheme-1.10.5 Weber’s condensation with N-acetylguanidine.<br />
In the late 1970’s Nishimura reported the condensation of substituted α-diketones<br />
with guanidine to yield a variety of useful products (Scheme-1.10.6). 91 This report<br />
illuminates the variety of chemistry that is possible around this heterocyclic core.<br />
Treatment of a diketone with guanidine in dioxane and methanol yields the substituted<br />
bicyclic bis-guanidine . Alternatively, aprotic reaction conditions can selectively<br />
deliver the 2-aminoimidizo-4-ol. This intermediate can undergo a base catalyzed<br />
pinacol-type rearrangement to form the 2-aminoimidizo-4-one. This same<br />
intermediate can give rise to the 4,5-diol upon exposure to aqueous hydrochloric acid.<br />
A similar hydration reaction with anhydrous HCl affords the di-methoxylated<br />
derivative. Hydrogenolysis of 2-aminoimidizo-4-ol cleanly gives the 4,5-dialkyl-2aminoimidazole.<br />
These laboratory transformations foreshadow potential biosynthetic<br />
relationships between the 2-aminoimidazole natural products isolated from marine<br />
sponges.<br />
R 2<br />
O<br />
R1 R2 NH 2<br />
HN N<br />
HN N<br />
NH 2<br />
N<br />
N<br />
H<br />
R 1<br />
NaOH<br />
MeOH<br />
NH 2<br />
dioxane<br />
MeOH<br />
R1 R2 HO<br />
HO<br />
conc.HCl<br />
N<br />
N<br />
H<br />
R 1<br />
R 2<br />
NH 2<br />
Scheme-1.10.6 Nishimura’s diketone condensation<br />
O<br />
O<br />
H 2N<br />
HN<br />
MeO<br />
R 1<br />
NH 2<br />
MeOH<br />
HCl<br />
N<br />
NH 2<br />
R 1<br />
R 2<br />
R 1<br />
R 1<br />
HN<br />
OH<br />
N<br />
R2 N<br />
R N<br />
MeO H<br />
2 H<br />
N<br />
N<br />
R 2<br />
N<br />
NH 2<br />
NH 2<br />
H2/Pd-C<br />
MeOH<br />
NH 2
1.10.2 Ambi-valent Addition of 2-Aminoimidazole<br />
Depending on reaction conditions, the parent heterocycle, 2-aminoimidazole, can be<br />
influenced to react either at N-2 or C-4. In Potier’s synthesis of girolline, 2aminoimidizole<br />
was added directly to the α-chloroaldehyde. Under the influence of<br />
sodium carbonate, the imidazole adds preferentially through the 4-position (Scheme-<br />
1.10.7 ). 92 As revealed in Horne’s synthesis of stevensine, methanesulfonic acid was<br />
used to add the 2-aminoimidazole across an olefin. 93-94 Horne has also shown that<br />
Friedel-Crafts type alkylation of the activated ethers can proceed with attack by C-4<br />
in the presence of methanesulfonic acid to give stevensine (Scheme-1.10.7).<br />
Alternatively, triflouroacetic acid persuades N-2 addition to give the N-alkylated 2aminoimidazole.<br />
H 2N<br />
H<br />
N<br />
N<br />
O<br />
Cl<br />
N<br />
O<br />
O<br />
Na2CO3 HCl<br />
HCl, H 2O<br />
H 2N<br />
Scheme-1.10.7 Potier’s Ambi-valent additions of 2-aminoimidazole<br />
Br<br />
HN<br />
HN<br />
N<br />
Br<br />
TFA rt.<br />
Br<br />
N<br />
H<br />
NH<br />
O<br />
H2N H<br />
N<br />
N<br />
Br<br />
Scheme-1.10.8 Horne’s Ambi-valent additions of 2-aminoimidazole.<br />
1.10.3 Formation of C-N bond.<br />
Br<br />
Br<br />
MeO<br />
N<br />
H<br />
Br<br />
NH<br />
O<br />
MsOH<br />
90 o C<br />
H<br />
N<br />
N<br />
HO<br />
NH 2<br />
Cl<br />
Girroline<br />
Br<br />
H 2N<br />
HN<br />
N<br />
NH<br />
N<br />
H O<br />
Stevensine<br />
It is now clear that, condensation reactions are applicable to the preparation of monoand<br />
di-substituted 2-aminoimidazoles. To generate more highly substituted 2-amino<br />
imidazole cores, the direct introduction of N-2 on an appropriately substituted<br />
imidazole is frequently applied. The first method for forming 2-aminoimidazoles, in
this manifold, was reported in 1925 by Burtles and Pyman who showed that azobromoaniline<br />
and dimethylimidazole underwent aromatic substitution to form the<br />
hydrazone (Scheme-1.10.9).The aryl hydrazone was then readily reduced by Zn dust<br />
and aqueous acetic acid or stannous chloride and hydrochloric acid.<br />
N 2<br />
HN<br />
N<br />
Br<br />
NaHCO 3<br />
H2O<br />
HN<br />
N<br />
N N<br />
Scheme-1.10.9 Pyman’s synthesis.<br />
Br<br />
SnCl 2<br />
100 o C<br />
HN<br />
N<br />
NH 2.HCl<br />
Hassner was the first to report the reaction of imidazole lithium with a vinyl azide,<br />
hydrolysis of the intermediate triazine gives the aminoimidazole. 95 Since that report,<br />
Potier has popularized the use of lithiated imidazoles. 96 Potier reported that lithiation<br />
with LDA followed by azide transfer from TsN3 efficiently generated the 2azidoimidazoles<br />
(Scheme-1.10.10). Hydrogenolysis of the azide proceeds smoothly to<br />
give the 2-aminoimidazole, exemplified in his synthesis of keramidine. 97<br />
N<br />
N<br />
Tr<br />
HN<br />
O<br />
H<br />
N<br />
Br<br />
LDA, TsN 3<br />
-70 o C<br />
N 3<br />
N<br />
N<br />
Tr<br />
HN<br />
Scheme-1.10.10 Potier’s method via lithiation.<br />
O<br />
H<br />
N<br />
Br<br />
10 % Pd/C<br />
Lithiated imidazoles can also be trapped by disulfides to give the 2-thioimidazoles.<br />
Oxidation to either the sulfone or sulfoxide creates a leaving group capable of<br />
displacement with azide (Scheme-1.10.11). 98 This strategy has been utilized by<br />
Weinreb in the synthesis of ageladine A. 99-100<br />
COOEt<br />
EtOOC<br />
N<br />
N<br />
Me SO2Me NaN 3, DMF<br />
87 o C, 13 h<br />
H 2<br />
COOEt<br />
EtOOC<br />
N<br />
N<br />
Me N3 Scheme-1.10.11 Anderson’s method of synthesis.<br />
H 2N<br />
N<br />
N<br />
Tr<br />
HN<br />
O<br />
H<br />
N<br />
Br
To avoid lithiation, Ohta has shown that 2-bromoimidazoles can undergo palladium<br />
catalyzed coupling with trimethylsilylazide (Scheme-1.10.12). Reduction again<br />
provides the 2-aminoimidazole. This strategy has been implemented by Ohta’s group<br />
to access several Leucetta alkaloids discussed below. Also, noteworthy, Ohta has<br />
shown that during reduction of the azide it can be directly protected as its<br />
benzylidenimine. 101-102<br />
N<br />
N<br />
Br<br />
TMSN 3<br />
PdCl 2(PPH 3) 2<br />
80 o C N<br />
N<br />
N 3<br />
H2, Pd-C<br />
Scheme-1.10.12 Ohta’s palladium catalyzed synthesis.<br />
1.10.4 Heterocyclic Exchange Reactions<br />
The transformation of 3-amino-1,2,4-oxadiazoles to 2-aminoimidazoles can be carried<br />
out by reaction with fluorinated ß-dicarbonyls to give the ß-hemiaminal (Scheme-<br />
1.10.13). 103 This can undergo subsequent conversion to the 2-amidoimidazole through<br />
a Boulton-Katritzky Rearrangement. This intermediate can then be reduced to give<br />
Intermediate. The benzamide can also be removed via acid catalyzed hydrolysis to<br />
give the trifluoromethyl amino-imidazole. An interesting reaction, however the<br />
synthesis of the intermediate ß-enaminocarbonyl is low yielding and initial results<br />
suggest limited substituent scope, as the initial condensation requires the presence of<br />
the trifluoromethyl ketone.<br />
Ph<br />
O<br />
O<br />
N<br />
NH 2<br />
N<br />
O<br />
CF 3<br />
R<br />
Montmorillonite K-10,<br />
PhMe, 100 o C;<br />
Ph<br />
F3C HN<br />
OH O<br />
N<br />
N<br />
O<br />
R<br />
Ph<br />
O<br />
N<br />
H<br />
Ph<br />
N<br />
F3C HN<br />
OH OH<br />
N<br />
N<br />
O<br />
R<br />
NaBH 4<br />
THF<br />
reflux<br />
Scheme-1.10.13 Boulton-Katritzky rearrangment of aminooxadiazoles.<br />
N<br />
H<br />
CF 3<br />
OH<br />
R<br />
N<br />
N<br />
Ph<br />
NH 2<br />
O<br />
N<br />
H<br />
N<br />
N<br />
H N<br />
2N<br />
H<br />
N<br />
H<br />
CF 3<br />
HCl<br />
EtOH<br />
reflux<br />
CF 3<br />
O<br />
R<br />
O<br />
R
Another route to 4(5)-acyl-2-amino-1H-imidazoles is based on the recyclization of 5acyl-2-amino-1,3-oxazoles<br />
(Scheme-1.10.14). 104 For example, 5-acetyl-2-aminooxazole<br />
gave upon heating in water solution with ammonia or aliphatic amines 2amino-1H-imidazoles<br />
in 32% (R = H) and 43-62% (R = alkyl or cycloalkyl) yields.<br />
Me<br />
O<br />
N<br />
O<br />
NH 2<br />
NH 3 or Amine<br />
H 2O, heating<br />
Me<br />
O<br />
N<br />
N<br />
H<br />
NHR<br />
Scheme-1.10.14 Mularski’s recyclization method.<br />
Methodology to prepare 2-aminoimidzoles has greatly advanced due to the rising<br />
demand in natural product synthesis and medicinal chemistry. However, the<br />
development of methods to succinctly generate a highly functionalized 2aminoimidazole<br />
core from stable precursors is warranted.<br />
1.11 The 2-Aminoimidazole as a Pharmacophore<br />
The 2-aminoimidazole has been utilized as a building block has led to the<br />
development of several medicinally relevant small molecules.<br />
1.11.1 Antibiotics Activity<br />
Researchers at Zeneca delivered a series of broad spectrum antibiotics a-c, inspired by<br />
the well studied cephalosporins. 106-106 They were further able to show that substitution<br />
on N1 of the aminoimidazole led to inactive compounds, again suggesting that this<br />
motif may make an acid hydrogen bond contact (Fig. 1.11.1). Interestingly they were<br />
able to correlate the pKa of the 2-aminoimidazole with activity. Against Gram<br />
positive organisms they found that a slight elevation in the pKa led to a dramatic<br />
decrease in activity. For Gram-negative bacteria, there was little difference,<br />
suggesting pKa may alter the membrane permeability.
N N<br />
N<br />
N<br />
S<br />
S<br />
S<br />
H<br />
N<br />
NH<br />
S<br />
S<br />
S<br />
H<br />
N<br />
NH<br />
S<br />
S<br />
S<br />
H<br />
N<br />
NH<br />
HOOC<br />
N NH<br />
HOOC<br />
N NH<br />
HOOC<br />
N NH<br />
O a O b O<br />
c<br />
pKa = 7.1<br />
pKa = 7.4<br />
pKa = 8.05<br />
S.aureus = 8<br />
S.aureus = 16 S.aureus = 256<br />
E Coli = 0.03<br />
E Coli = 0.015 E Coli = 0.03<br />
Fig-1.11.1 2-aminoimidazole modified cephalosporins.<br />
1.11.2 Sodium Hydrogen Exchanger-1 (NHE-1) Antagonists.<br />
Scientists at Bristol-Meyers Squibb have noted the ability of the 2-aminoimidazole to<br />
function as a bioisostere of acylguanidines. 106 Looking to produce novel inhibitors of<br />
the sodium hydrogen exchanger-1 (NHE-1) they aimed at replacing the acylguanidine<br />
in their lead compounds (Fig. 1.11.2). They surveyed a number of heterocyclic<br />
analogues that would conserve the pKa of the acylguanidine as a cationic species,<br />
necessary for antagonism of the Na+ transporter.<br />
Cl<br />
HN N<br />
NH 2<br />
Cl<br />
HN N<br />
NH 2<br />
Cl<br />
HN N<br />
a b NH<br />
Cl<br />
c 2 Cl<br />
d<br />
0.75 0.039 0.18 0.008<br />
Fig.- 1.11.2 NHE-1 antagonists. (NHE-1 Inhibition IC50 (µm))<br />
1.11.3 Anti HIV Activity<br />
N<br />
N<br />
Cl<br />
HN N<br />
Much effort has been dedicated to the development of HIV protease (HIV PR)<br />
inhibitors for the treatment of AIDS. The protease is responsible for the processing of<br />
nascent polypeptides to mature proteins comprising the viral particle. Without the<br />
formation of the mature particle, viral replication of HIV has been shown to be<br />
inhibited. HIV PR has therefore been an active biochemical target for the<br />
development of small molecule therapeutics.<br />
Wilkerson and co-workers at DuPont-Merck had developed a cyclic urea-based HIV<br />
PR inhibitor scaffold which possessed an acceptable pharmacokinetic profile, but<br />
lacking the potency necessary to advance the candidate. 107 Biochemical evaluation of<br />
NH 2
this series of compounds against the HIV PR dimer revealed that a and b were<br />
extremely potent inhibitors Ki = 0.023 and 0.012 nM respectively. The compounds<br />
were also able to inhibit viral replication in vitro as measured by the ability of the<br />
compounds to inhibit RNA synthesis by 90% (a) IC90 = 13.2 nM; (b) IC90 = 26.2 nM).<br />
Interestingly, QSAR on this series of cyclic ureas suggested the optimum lipophilicity<br />
for protease inhibition (ClogP = 4.4) is different from the inhibition of viral<br />
replication (ClogP = 6.36) as revealed by the reversal of Ki and IC90 selectivities for<br />
(a) and (b). This makes it difficult to optimize both parameters within the same<br />
molecule, but suggests that while (a, b) display the same hydrogen bonding pattern at<br />
the terminal urea, the lipophilicity disparity between the 2-aminoimidazole and the<br />
benzimidazole has a significant effect on their pharmacokinetic profile. With these<br />
results, (a) and (b) were advanced for pharmacokinetic studies in female Beagles. As<br />
seen in the pharmacokinetic profiles (Fig. 1.11.3) the decreased lipohilicity of (b) had<br />
a significant impact on the clearance (CL) and half-life (t1/2) of the compound,<br />
advancing its candidacy based on this improved PK profile.<br />
N<br />
NH<br />
H<br />
N<br />
Ph HO OH Ph<br />
O<br />
N<br />
O<br />
N<br />
NH 2<br />
N<br />
NH<br />
H<br />
N<br />
a b<br />
Fig.- 1.11.3 Unsymmetrical HIV PR inhibitors.<br />
Parameter a b<br />
Ki (nM) 0.023 0.012<br />
IC90 (nM) 13.2 26.2<br />
Dose (mg/kg) 5.0 5.0<br />
CL, L/h/kg 0.8 0.5<br />
Vss (L/Kg) 1.0 4.0<br />
T1/2 (h,iv) 0.9 5.6<br />
Ph HO OH Ph<br />
Table-1.13.1: Pharmacokinetic profiles of HIV PR inhibitors<br />
O<br />
N<br />
O<br />
N<br />
NH 2
1.11.4 α-adrenoreceptor agonists.<br />
Agents that can stimulate α-andrenoceptors modulate a variety of physiological<br />
processes including the reduction of blood pressure, sedation and the inhibition of<br />
intestinal fluid secretion. 108 Scientists at Allergan Pharmaceuticals targeted the α –<br />
andrenoceptor to reduce intraocular pressure(IOP), a common condition in patients<br />
suffering from glaucoma. 109 The challenge in designing such agents stems from the<br />
ability of α –andrenoceptor subtypes to modulate different biological processes, most<br />
concerning are those in the central nervous system (CNS). One approach to<br />
minimizing CNS effect is topical application, minimizing access of the compound to<br />
the CNS. From the known α-andrenoceptor agonist clonidine, 110 modifications to<br />
minimize CNS access generated the lead compounds p-aminoclonidine and AGN-<br />
191103 (21) (Fig. 1.13.4). The The alternative approach is to discover compounds<br />
displaying enough selectivity between the α-andrenoceptor subtypes such that they<br />
exhibit an enhanced therapeutic index. This led to replacing the imidazolidin-imine<br />
with a 2-aminoimidazole. This compound (a) was selected for further evaluation.<br />
Binding assays demonstrated (a) bound to the α2A-receptor with a Ki = 1.7 nM and<br />
was 1200-fold selective for the α2A –receptor over the α1-receptor, 50-fold selective<br />
for the α2A –receptor over the α2B –receptor, and 10-fold selective for the α2A –<br />
receptor over the α2C –receptor. Compound (a) was found to be effective in vivo with<br />
an EC50 = 8.7 nM and importantly remained effective when administered<br />
intravenously, demonstrating its capability of crossing the blood-brain barrier.<br />
H<br />
N N<br />
NH<br />
Cl<br />
Cl<br />
H<br />
N N<br />
NH<br />
Cl<br />
Cl<br />
NH 2<br />
Clonidine p-aminoclonidine AGN-191103<br />
Fig.- 1.11.4 α-adrenoreceptor agonists.<br />
H<br />
N<br />
NH<br />
N<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
O<br />
O<br />
Compound (a)<br />
1.11.5 Anti Cancer Activity<br />
Cancer has been the leading cause of death worldwide. Chemotherapy remains one of<br />
the major treatment options available for cancer, andmost of the currently used<br />
anticancer drugs are administered to patients via a parenteral infusion or bolus<br />
injection. Clinical complications with the parenteral administrations have been
documented. Extra care is needed because of inappropriate patient compliances, and<br />
extra cost associated with hospitalization is necessary. Efforts in searching for orally<br />
active anticancer agents have been extensive, including the anticancer drug category<br />
of tubulin binding agents from which only injectable drugs are available such as<br />
taxanes and vinca alkaloids. Recently Chiung-Tong Chen 111 reported the synthesis<br />
and biological functions of 2-amino-1-arylidenaminoimidazoles as orally active<br />
anticancer agents. Selective compounds had shown potent effects in the interference<br />
on the colchicines binding to tubulins, inhibition of tumor cell proliferation, and<br />
induction of human cancer cell apoptosis.<br />
R 2<br />
H 2N<br />
R 1<br />
N<br />
N<br />
N<br />
R 3<br />
R 4<br />
IC 50 = 0.05- >10 (µM)<br />
1.11.6 BACE-1 Inhibitors<br />
Alzheimer’s disease (AD) is the largest unmet medical need in neurobiology and<br />
accounts for the majority of dementia diagnosed in the elderly. AD is characterized by<br />
a progressively slow decline in cognitive function that leaves the end-stage patient<br />
dependent on custodial care with death occurring on the average of 9 years after<br />
diagnosis. The lack of an effective treatment for AD has stirred an intense search for<br />
novel therapies based on the amyloid hypothesis. This hypothesis states that a gradual<br />
and chronic imbalance between the production and clearance of Aß peptides results in<br />
their accumulation in the brain. These secreted peptides polymerize into neurotoxic<br />
oligomers that disrupt neuronal function and lead to cell death and memory loss that is<br />
phenotypical of AD. ß-secretase (BACE-1) is an as partyl protease representing the<br />
ratelimiting step in the generation of these Aß peptide fragments. Given the central<br />
role of Aß in AD pathology, inhibition of BACE-1 has become an attractive target for<br />
the treatment of Alzheimer’s disease. Vacca 112 and Hills 113 developed a series of<br />
aromatic heterocycles as BACE-1 inhibitors. The potency of the weak initial lead<br />
structure was dramatically enhanced using traditional medicinal chemistry. These<br />
inhibitors were shown to bind in a unique fashion that allowed for potent binding in a<br />
non-traditional fashion.
H 2N<br />
N<br />
N<br />
H<br />
R 2<br />
R 1<br />
N<br />
H2N N<br />
Me<br />
Bace-1 IC 50 = 4-6 (µM) Bace-1 IC 50 = 0.47-2 (µM) Bace-1 IC 50 = 0.47-2 (µM)<br />
Fig. 1.11.5 BACE-1 inhibitors<br />
1.11.7 Anti Biofilm Activity<br />
Bacterial biofilms are defined as a surface attached community of ignalling sms<br />
that are protected by an extracellular matrix of biomolecules. Within a biofilm state,<br />
bacteria are more resistant to antibiotics and are inherently insensitive to antiseptics<br />
and basic host immune responses. The NIH has estimated that 65-80% of all<br />
microbial infections are biofilm-based. Biofilm infections of indwelling medical<br />
devices are also of major concern, as once the device is colonized, infection is<br />
virtually impossible to eradicate. Bacterial biofilms 114-116 underlie the persistent<br />
colonization of hospital facilities, which perpetuates nosocomial infections. Hospitalacquired<br />
infections place a $10 billion burden on the U.S. healthcare system annually.<br />
Given the prominence of biofilms in infectious diseases, there has been an increasing<br />
effort toward the development of small molecules that will modulate bacterial biofilm<br />
development and maintenance. This, coupled with the spread of multi-drug antibiotic<br />
resistance across many of these bacteria, has put a tremendous burden on the scientific<br />
and medical community to alleviate biofilm-related problems. In this review, we will<br />
highlight the development of small molecules that inhibit and/or disperse bacterial<br />
biofilms through non-microbicidal mechanisms. The review will be segmented into<br />
providing a general overview of how bacteria develop into biofilm communities, why<br />
they are important, and the difficulties associated with their control. This will be<br />
followed by a discussion of the numerous approaches that have been applied to the<br />
discovery of lead small molecules that mediate biofilm development. These<br />
approaches are grouped into: 1) discovery/synthesis of molecules based upon<br />
naturally occurring bacterial ignalling molecules, 2) chemical library screening, and<br />
3) discovery/synthesis of natural product and natural product analogues.<br />
R 2<br />
R 1<br />
H 2N<br />
N<br />
N<br />
N<br />
R 1<br />
R 2
Very recently the research group of Melander has been studying widely the ability of<br />
simple analogues of the marine natural products bromoageliferin and oroidin (Fig.<br />
1.11.6) to control biofilm development. Bromoageliferin is a sponge-derived alkaloid<br />
that was reported to inhibit the formation of bacterial biofilms from marine sources,<br />
presumably as a defense mechanism against biofouling. 117 They reasoned that core<br />
structures derived from this complex molecule could be used as structural inspiration<br />
for the development of potent and synthetically accessible anti-biofilm agents. One of<br />
these scaffolds developed was based upon an aryl framework. 118 From a medicinal<br />
chemistry stand point, this scaffold was deemed a promising platform to develop<br />
further functionalized 2-aminoimidazole (2-AI) derivatives as diversity could rapidly<br />
be introduced through manipulation of the benzene ring. They described the synthesis<br />
and anti-biofilm activity of these aryl 2-AI derivatives against three commonlystudied<br />
Gram-negative bacteria.<br />
H 2N<br />
H 2N<br />
N<br />
N<br />
H<br />
N<br />
Bromoageliferin<br />
NH<br />
HN<br />
Br<br />
N<br />
H<br />
O<br />
O<br />
NH<br />
H<br />
N<br />
Br<br />
Br<br />
H 2N<br />
N<br />
N<br />
H<br />
H 2N<br />
Fig. 1.11.6 2-Aminoimidazole-based anti-biofilm molecules.<br />
N<br />
H<br />
O<br />
Oroidin<br />
N<br />
N<br />
H<br />
H<br />
N<br />
Br<br />
R<br />
Aryl 2-AI scaffold<br />
The research group of melander has recently developed several novel libraries of 2-<br />
aminoimidazole small molecules inspired by the marine alkaloids bromoageliferin<br />
and oroidin. These natural products were reviously reported to inhibit biofilm<br />
formation of the marine arotobacterium Rhodospirillum salexigens. 119 TAGE and<br />
CAGE were the first documented 2-aminoimidazoles with anti-biofilm activity against<br />
Pseudomonas aeruginosa biofilms.<br />
Analogues of the structurally simpler alkaloid oroidin were also pursued to develop<br />
novel classes of small molecules with anti-biofilm activity. Recently, an oroidin<br />
Br
inspired library was constructed utilizing click chemistry to generate a diverse library<br />
of 2-aminoimidazole/triazole conjugates (2-AIT).These compounds displayed the<br />
widest spectrum of anti-biofilm activity observed within the 2-aminoimidazole class<br />
(Fig. 1.11.7). 120-121<br />
H 2N<br />
H 2N<br />
N<br />
N<br />
H<br />
N<br />
Bromoageliferin<br />
H 2N<br />
N<br />
N<br />
H<br />
NH<br />
HN<br />
Br<br />
N<br />
H<br />
N<br />
H<br />
O<br />
O<br />
NH<br />
O<br />
Oroidin<br />
H<br />
N<br />
H<br />
N<br />
Br<br />
Br<br />
Br<br />
Br<br />
H 2N<br />
N<br />
N<br />
H<br />
H 2N<br />
HN<br />
N<br />
N<br />
H<br />
O<br />
H<br />
N<br />
H<br />
N O<br />
Br<br />
NH<br />
Br Br<br />
Br<br />
H 2N<br />
H 2N<br />
N<br />
N N<br />
R<br />
2-AIT Library<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
TAGE<br />
CAGE<br />
Fig. 1.11.7 Representative 2-aminoimidazoles derived from the marine natural<br />
products bromoageliferin and oroidin.<br />
The synthetic approach to this 2-AIT derivatization is outlined in (Scheme 1.11.1). In<br />
their previous synthesis of 2-AIT conjugates, they employed the alkyne-derived 2-AI<br />
as a precursor for the CuI-mediated[3+2] alkyne/azide cycloaddition (click reaction).<br />
Although this reaction worked well, purification of the resulting product was<br />
cumbersome, due to the need for copious amounts of ammonia saturated methanol for<br />
column chromatography. Therefore, they decided to revise the route by employing a<br />
Boc-protected 2-AI alkyne that would allow more traditional means of purification<br />
(i.e. methanol/dichloromethane columns). The Boc-protected scaffold was<br />
synthesized from oct-7-ynoic acid by treatment with oxayl chloride followed by<br />
diazomethane and quenching of the resulting α-diazo ketone with HBr to generate the<br />
intermediate a-bromo ketone. Cyclization with Boc-guanidine then delivered the<br />
target 2-AI alkyne..<br />
NH 2<br />
NH 2<br />
NH 2<br />
NH 2
OH<br />
a,b<br />
O<br />
N<br />
H2N N<br />
Boc<br />
N 3<br />
H<br />
N R<br />
N<br />
N<br />
H2N N N<br />
N<br />
H<br />
a) i : (COCl) 2,CH 2Cl 2, DMF (cat.), ii : CH 2N 2,Et 2O/CH 2Cl 2, iii : HBr (82%) ; b) Boc-guanidine, DMF, RT<br />
(59%) ; c) azide, CuSO 4, Na ascorbate, EtOH, CH 2Cl 2,H 2O; d) TFA, CH 2Cl 2 (58-94 % over two steps)<br />
Scheme-1.11.1 Melander’s 2-AI-T conjugate synthesis.<br />
It was explained by earlier work that once target 2-AI alkyne had been synthesized,<br />
assembled a diverse array of azido amides to employ in the click reaction to create<br />
pilot collection of 2-AIT conjugates. Briefly, 2-bromo-ethylamine was treated with<br />
sodium azide to deliver 2-azido-ethylamine, which following acylation (via the<br />
respective acid chloride) generated the azido amides for elaboration into the 2-AIT<br />
collection. Each azido amide was then subjected to the click reaction with target 2-AI<br />
alkyne. Boc-deprotection (TFA/CH2Cl2) followed by counterion exchange<br />
(trifluoroacetate for chloride) delivered the target 2-AIT compounds for antibiofilm<br />
screening.<br />
1.12 Introduction to Biofilm<br />
Biofilms play a significant role in infection disease and account for up<br />
to 80% of microbial infections in the body.<br />
Bacterial biofilms are defined as a surface-attached community of bacteria<br />
that are surrounded by a protective extracellular matrix.<br />
On a global scale, biofilm related costs incur 6-10 billions of Euros to the<br />
agricultural, engineering, and medical sectors of economy.<br />
Despite the focus of modern microbiology research on pure culture,<br />
planktonic bacteria, it is now recognized that most bacteria found in<br />
natural, clinical, and industrial settings persist in biofilms.<br />
Within a biofilm, bacteria are upward of 1000-times more resistant to<br />
conventional antibiotic treatment<br />
Biofilms grow virtually everywhere, in almost any environment where<br />
there is a combination of moisture, nutrients, and a surface.<br />
c,d<br />
H N<br />
R
1.12.1 Properties of biofilms<br />
A biofilm community can be formed by a single bacterial species, but in nature<br />
biofilms almost always consist of rich mixtures of many species of bacteria, as well as<br />
fungi, algae, yeasts, protozoa, other microorganisms, debris and corrosion products.<br />
Biofilms are held together by sugary molecular strands, collectively termed<br />
"extracellular polymeric substances" or "EPS." The cells produce EPS and are held<br />
together by these strands, allowing them to develop complex, three-dimensional,<br />
resilient, attached communities. Biofilms cost the U.S. literally billions of dollars<br />
every year in energy losses, equipment damage, product contamination and medical<br />
infections. But biofilms also offer huge potential for bioremediating hazardous waste<br />
sites, biofiltering municipal and industrial water and wastewater, and forming<br />
biobarriers to protect soil and groundwater from contamination
1.12.2 Biofilm Growth Cycle<br />
1) Planktonic bacteria reversibly attach to a surface suitable for growth and<br />
Bacteria begin secretion of the extra cellular polymeric substances (EPS) and<br />
attachment becomes irreversible.<br />
2) The maturing biofilm begins to take on a 3-dimensional shape. Biofilm<br />
communities can develop within hours.<br />
3) The biofilm fully matures, and complex architecture is observed. Bacteria<br />
disperse from the biofilm to reinitiate biofilm colonization of a distal surface.<br />
1.12.3 Biofilm Drug Resistance
The figure below shows a model of biofilm resistance to killing based on persister<br />
survival.<br />
Initial treatment with antibiotic kills normal cells (coloured green) in both planktonic<br />
and biofilm populations.<br />
The immune system kills planktonic persisters (coloured green), but the biofilm<br />
persister cells (coloured pink) are protected from the host defences by the exopolymer<br />
matrix.<br />
After the antibiotic concentration is reduced, persisters resuscitate and repopulate the<br />
biofilm and the infection relapses.<br />
Biofilm infections are highly recalcitrant to antibiotic treatment. However, planktonic<br />
cells that are derived from these biofilms are, in most cases, fully susceptible to<br />
antibiotics. Importantly, biofilms do not actually grow in the presence of elevated<br />
concentrations of antibiotics, therefore biofilms do not have increased resistance<br />
compared with planktonic cells. 122 But if biofilms are not resistant to antibiotics, how<br />
do biofilm bacteria avoid being killed by antibiotic treatments? The resistance of<br />
biofilms to drug therapy has been one of the more elusive problems in microbiology,<br />
but the analysis of a simple dose-response experiment provided an unexpected insight<br />
into the puzzle. 122-124<br />
Most of the cells in a biofilm are highly susceptible to bactericidal agents such as<br />
fluoroquinolone antibiotics or metal oxyanions, which can kill both rapidly dividing<br />
and slow- or non-growing cells. 124-126 This is important, as cells in the biofilm are<br />
slow-growing, and many are probably in the stationary phase of growth. The<br />
experiment also revealed a small sub-population of cells that remain alive irrespective<br />
of the concentration of the antibiotic (persisters). The number of surviving persisters<br />
was greater in the non-growing stationary phase. In vitro, a stationary culture seems to<br />
be more tolerant than a biofilm to antibiotics. However, this situation is probably<br />
reversed in vivo. Antibiotic treatment will kill most biofilm and planktonic cells,<br />
leaving persisters alive. At this point, the similarity with an in vitro experiment<br />
probably ends. The immune system can mop up and kill remaining planktonic<br />
persisters, just as it eliminates nongrowing cells of a bacterial population that is<br />
treated with a bacteriostatic antibiotic. However, the biofilm exopolymer matrix<br />
protects against immune cells, 127-129 and persisters that are contained in the biofilm
can survive both the onslaught of antibiotic treatment and the immune system. When<br />
the concentration of antibiotic reduces, persisters can repopulate the biofilm, which<br />
will shed off new planktonic cells, producing the relapsing biofilm infection. The<br />
problem of biofilm resistance 72 to killing by most therapeutics probably defaults to<br />
persisters. Interestingly, yeast biofilms also form tolerant persisters.<br />
1.13 Recent publications on 2-aminoimidazoles.<br />
The core structure 2-aminoimidazole has assumed importance in various synthesis<br />
related to heterocyclic in drug synthesis as appeared in Sci-finder search results on the<br />
basis of number of publications in medicinal and synthetic chemistry journals.<br />
Fig.1.10 Sci-finder search results by heating term 2-aminoimidazole.<br />
1.14 Conclusion<br />
Bacterial biofilms pose a serious threat to the healthcare system of our society as they<br />
are responsible for the morbidity and mortality of a myriad of diseases. The<br />
development of antibiotic resistance among many bacterial strains has put a<br />
tremendous pressure on the medical community to find alternative approaches for the<br />
treatment of biofilm-mediated diseases. In this present work of thesis a microwave<br />
assisted synthesis of small molecules which shows ability to controlling bacterial<br />
antibiofilm has been reported.
1.15 References<br />
[1] (a) William A.S., Aleksel F.B., Ron C., Organic Synthesis: the science behind art. Royal<br />
Society of Chemistry (Great Britain). (b) Organic Synthesis Coll vol. and (c) Comprehensive<br />
organic Synthesis book volumes.<br />
[2] For recent reviews on microwave-assisted organic synthesis see: (a) Kappe, C. O. (2004)<br />
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Microwave Assisted Synthesis & Structure<br />
Activity Relationship of 2-Hydroxy-2-phenyl-<br />
2,3-dihydro-imidazo[1,2-a]pyrimidinium Salts<br />
and 2N-Substituted 4(5)-Phenyl-2-Amino-1H-<br />
imidazoles as Inhibitors of the Biofilm<br />
Formation by Salmonella Typhimurium and<br />
Pseudomonas aeruginosa
Chapter-2<br />
Microwave Assisted Synthesis & Structure Activity Relationship of 2-<br />
Hydroxy-2-phenyl-2,3-dihydro-imidazo[1,2-a]pyrimidinium Salts<br />
and 2N-Substituted 4(5)-Phenyl-2-Amino-1H-imidazoles as Inhibitors<br />
of the Biofilm Formation by Salmonella Typhimurium and<br />
Pseudomonas aeruginosa<br />
Br<br />
N<br />
N<br />
N R 1<br />
OH<br />
R 2<br />
In the current chapter a library of 1-substituted 2-hydroxy-2-phenyl-2,3-dihydro-<br />
imidazo[1,2-a]pyrimidinium salts and 2N-substituted 4(5)-phenyl-2-amino-1H-<br />
imidazoles was synthesized via microwave assisted protocol and tested for the<br />
antagonistic effect against biofilm formation by Salmonella Typhimurium and<br />
Pseudomonas aeruginosa.<br />
Publications:<br />
[1] One-pot microwave-assisted protocol for the synthesis of substituted 2-amino-<br />
R1 HN<br />
1H-imidazoles. Mol Divers. (2010) DOI 10.1007/s11030-010-9270-5<br />
[2] Structure Activity Relationship of 2-Hydroxy-2-phenyl-2,3-dihydro-<br />
imidazo[1,2-a]pyrimidinium Salts and 2N-Substituted 4(5)-Phenyl-2-Amino-<br />
1H-imidazoles as Inhibitors of the Biofilm Formation by Salmonella<br />
Typhimurium and Pseudomonas aeruginosa Bioorganic & Medicinal<br />
Chemistry. Submited (2010)<br />
N<br />
N<br />
H<br />
R 2
2.1 Introduction<br />
As described in chapter-1 the class of 2-aminoimidazoles has recently been given<br />
particular interest due to various biological properties of these compounds. 2-<br />
Aminoimidazole alkaloids and their metabolites, isolated from the marine sponges<br />
Hymeniacidon sp., have been described as potent antagonists of serotonergic 1 and<br />
histaminergic 2 receptors. Naamine and isonaamine alkaloids from the marine sponges<br />
Leucetta sp. exhibit antiviral and anticancer activity. 3,4 Because of these interesting<br />
biological activities, numerous synthetic routes to 1-substituted and 1-unsubstituted 2aminoimidazoles<br />
have been reported. Modern synthetic methods for accessing 1unsubstituted<br />
2-amino-1H-imidazoles can be roughly classified as heterocyclization<br />
of substituted or protected guanidines with 1,2-dielectrophiles, 5a-c heteroaromatic<br />
nucleophilic substitution 5c,6 and recyclization of 2-aminooxazoles. 7 Although different<br />
substituted guanidines are readily available and can be prepared in situ (e.g. from<br />
cyanamines 8 ), the high basicity of guanidines together with non-regioselectivity often<br />
leads to multiple products. 9 Protection by acetyl 5a and Boc-groups 5c requires, in turn,<br />
acidic deprotection conditions. Another procedure is the cyclocondensation of<br />
aldehydes and guanidine nitrate using sodium cyanide and supported aluminum oxide,<br />
which provides symmetric 2-aminoimidazoles. 10<br />
Recently, we described two new approaches to the synthesis of substituted 2-amino-<br />
1H-imidazoles. The first approach is based on the cleavage of imidazo[1,2a]pyrimidines<br />
11 with hydrazine 12 In the second approach we reported microwave<br />
assisted one pot synthesis.(scheme-3) 13
2.2 Reaction scheme:<br />
2.2.1 2-amino pyramidine: (Scheme-1)<br />
N<br />
TEA, EtOH N<br />
R NH2 R<br />
N Cl MW N N<br />
120 H<br />
o +<br />
C, 25 min<br />
2.2.2 Synthesis of substituted 2-amino 1 H-imidazole. (Scheme-2)<br />
N<br />
N N<br />
64% N2H4 100 °C, 10 min<br />
R N<br />
N<br />
+<br />
Br<br />
H<br />
R1 N<br />
MeCN<br />
H MW<br />
O 80 °C, 30 min Br<br />
1<br />
OH<br />
R2 MeCN<br />
MW<br />
R 2<br />
2.2.3 One-Pot approach: (Scheme-3)<br />
N<br />
R1 N N<br />
H<br />
+<br />
Br O<br />
H<br />
R 2<br />
1.MW, 80 °C<br />
MeCN, 30 min<br />
2. N2H4, MW 90 °C<br />
MeCN, 10 min<br />
R 1<br />
HN<br />
N<br />
N<br />
H<br />
R 2<br />
R 1<br />
HN<br />
N<br />
N<br />
H<br />
R 2
2.3 Proposed Mechanism:<br />
Regarding the mechanism of the transformation of 2-hydroxy-2,3-dihydro-1Himidazo[1,2-a]pyrimidinium<br />
salts into 2-amino-1H-imidazoles, we presume that the<br />
reaction proceeds via an unusual Dimroth-type rearrangement 14-16 (Scheme-4).<br />
Scheme-4: Proposed Mechanism for the Dimroth-type Rearrangement of 2-<br />
Hydroxy-2,3-dihydro-1H-imidazo[1,2-a]pyrimidinium Salts III-12<br />
N<br />
N N R1 Br OH<br />
R 2 R3<br />
N N<br />
R 2<br />
NH 2<br />
R1 OH<br />
R 3<br />
N2H4 fast<br />
HN NH R 1<br />
HN<br />
R 2<br />
H 2NHN<br />
O<br />
R 3<br />
N<br />
N<br />
N R1 OH<br />
R 2 R3<br />
R 1HN<br />
N<br />
N<br />
H<br />
H 2NHN<br />
R 2<br />
OH<br />
R 3<br />
N<br />
N<br />
N R1 OH<br />
R 2 R3<br />
1 A B<br />
- H 2O<br />
slow<br />
R 1HN<br />
C D E 2<br />
In the first step, the 2-hydroxy-2,3-dihydroimidazo[1,2-a]pyrimidinium salt (1)<br />
undergoes cleavage of the pyrimidine ring, resulting in the generation of pyrazole and<br />
2-amino-5-hydroxyimidazolidine (C), which is in equilibrium with the open form (D).<br />
This can cyclize again leading to the isomeric 2-amino-5(4)-hydroxyimidazolidines<br />
(E). Both isomers (C) and (E) were detected by mass-spectrometry. Final<br />
dehydratation upon microwave irradiation, results in the rearranged 2-amino-1Himidazoles<br />
2. This dehydratation step, as judged by mass-spectrometry, was found to<br />
be the slowest step of the transformation. While some 2-amino-5(4)hydroxyimidazolidines<br />
(E) lost water spontaneously at room temperature, other<br />
required higher temperature upon microwave irradiation. Therefore all reactions were<br />
run at 100 °C, preventing the sequence from stopping after the first step.<br />
-<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
R 2<br />
R 3
2.4 Results and discussion:<br />
Initially careful investigation of the formation and dehydratation of salt (3) resulting<br />
in the formation of salt (4) under conventional heating conditions as well as upon<br />
microwave irradiation has been studied. As a proof of concept, the condensation of 2methylaminopyrimidine<br />
(1, R1 = Me) and α-phenacylbromide (2, R2 = Ph) was<br />
studied (Table 1). A sealed vial containing a solution of the starting compounds in<br />
acetonitrile was conventionally heated with an oil bath (Table 1, No-1-6) or irradiated<br />
with microwaves (Table 1, No-7-12) at different temperatures for 30−60 min. The<br />
formation of the 2-hydroxy salt (3) was faster under microwave irradiation and this<br />
compound was obtained in 88% yield within 30 min. Further increase of the<br />
temperature up to 120 °C using conventional heating or microwave irradiation led to a<br />
mixture of salts (3) and (4) (Table 1). Interestingly, using microwave irradiation at<br />
120 °C for 60 min, we were able to drive the reaction completely to the formation of<br />
the imidazo[1,2-a]pyrimidinium salt (4) (Table 1, No-12).<br />
N<br />
N N R N<br />
N<br />
Br O<br />
R1 N N +<br />
1 + N<br />
H H R Br<br />
N<br />
2<br />
OH<br />
1 2 3 R2 R Conditions<br />
Br<br />
1<br />
(R1 = Me, R2 = Ph)<br />
4 R2 No. Conditions Time (min) T (°C) 3 (yield %) b 4 (yield %) b<br />
1<br />
30 80 64 0<br />
2 60 80 77 0<br />
3 30 100 81 Traces<br />
Conventional<br />
4 60 100 85 Traces<br />
5 30 120 68 17<br />
6 60 120 53 28<br />
7<br />
30 80 88 0<br />
8 60 80 85 0<br />
9 Microwave 30 100 48 33<br />
10 60 100 45 35<br />
11 30 120 12 79
No.<br />
12 60 120 traces 84<br />
a<br />
All reactions were carried out on a 1 mmol scale of 2-methylaminopyrimidine (1, R1 = Me) with<br />
1.35 equiv of α-phenacylbromide (2, R2 = Ph) in MeCN (5 Ml); b isolated yield after recrystallization<br />
from MeCN.<br />
Table-1: Investigation of the condensation under conventional heating and<br />
microwave irradiation a<br />
As the transformation of salts (3) into salts (4) is relatively rapid at the temperatures<br />
above 100 °C, the synthesis of salts 3 was conducted at 80 °C. Treatment of<br />
substituted 2-aminopyrimidines (1) with 15 mol % excess of α-bromoketones (2) in<br />
MeCN under microwave irradiation for 30 min generated the intermediate salts (3)<br />
which, in most cases, precipitated from the reaction mixture upon cooling (Table-2).<br />
Reaction progress was monitored by mass-spectrometry. In all cases examined, the<br />
reaction appeared to be complete after 30 min. The cleavage step was performed<br />
under microwave irradiation at 90 °C, using 7 equivalents of hydrazine hydrate. Based<br />
on the data given in (Table-2), the reaction appears to be compatible with both aryl<br />
and alkyl substitutions. All the reactions were clean, smooth, and provided the<br />
products in good and high yields. The compounds were purified by column<br />
chromatography using 5−10% MeOH in CH2Cl2 as the eluent. All the final 2-amino-<br />
1H-imidazoles were characterized by 1 H and 13 C NMR spectroscopy. Their<br />
composition was also confirmed by HRMS.<br />
R1 HN<br />
N<br />
N<br />
H<br />
R 2<br />
Compound<br />
Code<br />
R1 R2 Yield<br />
1 BS-136* CH3 2,4-(di-OCH3) 48<br />
2 BS-137* (benzo[d][1,3]dioxol-6- naphthalen-1-yl 72
yl)methyl<br />
3 BS-140* C3H7 3,4-(di-Cl) 70<br />
4 BS-141* cyclohexane 4-SO2Me 43<br />
5 BS-143* C8H17 4-Cl 43<br />
6 BS-146* C5H11 4-Cl 57<br />
7 BS-147* C6H13 4-F 61<br />
8 BS-148* 4-methoxyphenethyl 3-Br 44<br />
9 BS-154* cyclooctane 4-SO2Me 53<br />
10 BS-139* 2-methoxyethyl 4-CN 55<br />
11 BS-258 C8H17 4-OCH3 78<br />
12 BS-259 C8H17 4-F 69<br />
13 BS-260 C8H17 3,4-(di-Cl) 72<br />
14 BS-261 C8H17 3-Br 79<br />
15 BS-262 C8H17 naphthalen-1-yl 68<br />
16 BS-263 C8H17 4-NO2 66<br />
17 BS-264 C8H17 4-(4-NO2Ph) 75<br />
18 BS-265 C8H17 SO2Me 54<br />
19 BS-292 i-Bu 4-NO2 70<br />
20 BS-293 i-Bu H 71<br />
21 BS-294 i-Bu 4-Br 69<br />
22 BS-295 i-Bu 4-Cl 73<br />
*Compounds have been synthesized via One-pot protocol (Scheme-3).<br />
All compounds are either oily or amorphous solid.<br />
Table-2: Microwave assisted synthesis of substituted 2-amino-1H-imidazoles.<br />
2.5 Biofilm activity:<br />
Bacteria are able to switch between a planktonic life style and a biofilm mode of<br />
growth, in which they live as structured communities of bacterial cells enclosed in a<br />
self-produced polymeric matrix and adherent to an inert or living surface. 17 As<br />
bacteria in biofilms are more resistant to challenges from predators, antibiotics,<br />
disinfectants and host immune systems, 18-21 serious problems and high costs have<br />
been associated with biofilms, both in medicine and industrial settings. According to<br />
the National Institutes of Health, more than 80% of microbial infections are related to<br />
biofilms. 22 Especially the use of indwelling medical devices comprises a high risk for
the development of biofilm related infections. 19 This high prevalence of biofilm<br />
related infections is particularly problematic given the fact that bacteria in biofilms<br />
can be up to 1000-fold more resistant to antibiotics. 23 In industry, biofilms have been<br />
implicated e.g. in the contamination of installations in food industry, mild steel<br />
corrosion, decreased passage through pipelines by colonization of the interior of the<br />
pipes, and enhanced resistance of vessels by initiation of “biofouling” on the vessel<br />
hulls. The yearly economic loss caused by ‘biofouling’ in the marine industry is<br />
estimated at $ 6.5 billion. 24<br />
One way to deal with this problem is the development of small molecules that are able<br />
to prevent or destroy biofilm formation 25 . Only a few molecular scaffolds have been<br />
identified to date, among which the best-studied examples are (1) the halogenated<br />
furanones, which were originally isolated from the seaweed Delisea pulchra, 26-27 (2)<br />
analogues of the homoserine lactone signalling molecules 28 and (3) analogues of the<br />
sponge-derived marine natural alkaloids oroidin and bromoageliferin. 29-36 A<br />
particularly valuable approach is the development of small molecules that specifically<br />
target the biofilm formation in a non-toxic manner, as it is expected that resistance<br />
against these compounds will emerge much slower than against classical<br />
microbiocidal compounds. As a consequence, non-toxic biofilm inhibitors have the<br />
potential to be used in a preventive treatment of a wide diversity of industrial and<br />
medical surfaces. Furthermore, the potential to co-dose biofilm inhibitors and<br />
classical antibiotics for the treatment of biofilm infections is also an attractive<br />
option. 27<br />
Salmonella enterica serovar Typhimurium and Pseudomonas aeruginosa are two well<br />
studied organisms in terms of biofilm formation. Salmonella enterica is worldwide<br />
one of the most important causes of foodborne infections. Salmonella is able to form<br />
biofilms on a variety of both biotic surfaces (such as gallstones, 37 plant surfaces, 38-39<br />
and epithelial cell layers 40 ) and abiotic surfaces (such as concrete, plastics, glass,<br />
polystyrene, … ) 41-42 . These biofilms are an important survival strategy in all stages<br />
of infection, from transmission to chronic infection. Severe non-typhoid Salmonella<br />
infections are commonly treated with fluoroquinolones and third-generation<br />
cephalosporins. Unfortunately, there are alarming reports concerning the development<br />
of resistance against these antibiotics 43 , underlining the urgent need of alternative<br />
anti-Salmonella strategies. Given the importance of biofilms in the spread of<br />
Salmonella, the development of Salmonella biofilm inhibitors seems a promising
approach. P. aeruginosa is an opportunistic pathogen implicated in a myriad of<br />
infections. Patients with compromised host defenses, such as burn patients, HIV<br />
patients and cystic fibrosis patients (80% colonization rate of P. aeruginosa 44 ) are<br />
particularly susceptible to P. aeruginosa infections. 45 P. aeruginosa biofilms have<br />
been related to recurrent ear infections, chronical bacterial prostatitis and lung<br />
infections in CF patients, the latter being extremely harmful as P. aeruginosa<br />
colonization and chronic lung infection is the major causative agent of morbidity and<br />
mortality in CF patients. 46 Moreover, P. aeruginosa can colonize as biofilms a<br />
variety of medical devices such as intravascular catheters and urinary catheters.<br />
Obviously there is an urgent need of agents that can prevent or eradicate P.<br />
aeruginosa biofilms on infected tissues and on medical devices.<br />
2.5.1 2N-substituted 2-aminopyrimidines<br />
Some members of the 2-aminopyrimidine class of compounds have previously been<br />
shown to possess antibacterial and antifungal activity. 47-48 These molecules are the<br />
precursors of the N1-substituted diazo[1,2-a]pyrimidinium salts in our synthesis<br />
pathway (scheme-2). The availability of a broad array of 2-aminopyrimidines,<br />
substituted with n-alkyl, cyclo-alkyl and aromatic groups at the N2-position prompted<br />
us to investigate the potential of this class of compounds as biofilm inhibitors. The<br />
influence of compounds on the biofilm formation of S. Typhimurium was tested at<br />
25°C. Remarkably, none of the compounds does have an effect on the biofilm<br />
formation at 400 µM, which was the highest concentration tested.<br />
2.5.2 2-hydroxy-2,3-dihydro-imidazopyrimidinium salts<br />
A broad array of 1-substituted 2-hydroxy-2-phenyl-2,3-dihydro-imidazopyrimidinium<br />
salts were synthesized via previously established chemistry from our laboratory and<br />
their ability to prevent the biofilm formation of S. Typhimurium and P. aeruginosa<br />
was tested. These molecules differ in the substitution pattern of the 2-phenyl ring and<br />
in the nature of the substituent at the 1-position i.e. n-alkyl, iso-alkyl, cyclo-alkyl.<br />
2.5.2.1 n-Alkyl or iso-alkyl substituents at 1-position
In first instance, a series of 2-hydroxy-2-phenyl-2,3-dihydro-imidazopyrimidinium<br />
salts with a broad variety of n-alkyl or iso-alkyl substituents at the 1-position, with<br />
lengths ranging from 1 carbon atom to 14 carbon atoms was synthesized. The 2phenyl<br />
group of these salts is either unsubstituted, para-substituted with a chlorine<br />
atom, a nitro group, a fluorine atom, a bromine atom or a methoxy group, or 3,4disubstituted<br />
with chlorine atoms. Each compound was assayed for the ability to<br />
inhibit S. Typhimurium ATCC14028 biofilm formation at 25 °C. As depicted in<br />
figure 1A, a clear correlation was found between the length of the alkyl substituent<br />
and the biofilm inhibitory activity. In general the activity of the molecules with a<br />
short alkyl chain was found to be very low (IC50 > 400 µM). Within a series of<br />
molecules with the same substitution of the 2-phenyl ring, in general a gradual<br />
increase in biofilm inhibitory activity was observed by raising the length of the alkyl<br />
chain from 1 to 8 carbon atoms. The compounds with an octyl substituent show a<br />
maximal activity with IC50 values in the range of 6-11 µM. By further raising the<br />
alkyl chain length from 8 to 14 carbon atoms, a gradual decrease in biofilm inhibitory<br />
activity was observed. For the molecules with a heptyl, octyl, nonyl and decyl side<br />
chain (which are the most active molecules), the nature of the substituent of the 2phenyl<br />
group does not have a substantial effect on the biofilm inhibitory activity.<br />
Next the influence of a subset of the 2-hydroxy-2-phenyl-2,3-dihydroimidazopyrimidinium<br />
salts for their ability to prevent the biofilm formation of P.<br />
aeruginosa was studied. As represented in table-4 and figure-1B, a similar structure<br />
activity relationship was found as in the case of Salmonella biofilm inhibition.<br />
Compounds with short alkyl substituents (C1-6) in general only have a slight effect on<br />
the biofilm formation (IC50’s >80 µM), while compounds with medium length side<br />
chains (C7-C10) have IC50 values between 20-40 µM and compounds with long side<br />
chains (C11-C14) have IC50 values higher than 800 µM. However, it should be<br />
mentioned that some of the compounds with long side chain do reduce the biofilm<br />
formation to a certain extent, but their dose response curves reach a steady state level<br />
of 25 to 45 % biofilm inhibition starting from concentrations between 25 and 50 µM.
Br<br />
N<br />
N<br />
N R 1<br />
OH<br />
R 2<br />
No. Code R2 R1<br />
S. Typhimurium<br />
IC50<br />
P. aeruginosa<br />
IC50<br />
1 BS-289 H i-Bu 131.2 289.4<br />
2 BS-083 H n-Pen 278.2 565.4<br />
3 BS-058 H n-Hex 102.0 405.8<br />
4 BS-049 H n-Hep 23.4 25.5<br />
5 BS-052 H n-Oct 9.8 14.4<br />
6 BS-061 H n-Non 8.3 26.8<br />
7 BS-055 H n-Dec 15.0 29.9<br />
8 BS-064 H n-Und 24.6 >800<br />
9 BS-067 H n-Dod 27.5 >800<br />
10 BS-070 H n-Trd 81.6 >800<br />
11 BS-073 H n-Tet 179.6 >800<br />
12 BS-291 4-Cl i-Bu 31.4 83.4<br />
13 BS-099 4-Cl n-Pen 32.6 163.9<br />
14 BS-092 4-Cl n-Hex 13.7 79.8<br />
15 BS-089 4-Cl n-Hep 6.7 36.9<br />
16 BS-090 4-Cl n-Oct 7.0 15.7<br />
17 BS-093 4-Cl n-Non 18.3 20.2<br />
18 BS-091 4-Cl n-Dec 51.3 83.3<br />
19 BS-094 4-Cl n-Und 61.9 >800<br />
20 BS-095 4-Cl n-Dod 122.1 >800<br />
21 BS-096 4-Cl n-Trd 316.1 >800<br />
22 BS-097 4-Cl n-Tet >800 >800<br />
23 BS-288 4-NO2 i-Bu 322.5 191.7<br />
24 BS-290 4-Br i-Bu 5.2 6.3<br />
IC50: Concentration of inhibitor needed to inhibit biofilm formation by 50%.<br />
Table-4: Influence of 1-alkylated 2-hydroxy-2,3-dihydro-imidazo[1,2a]pyrimidinium<br />
salts on the biofilm formation of S. Typhimurium ATCC14028 and P.<br />
aeruginosa PA14 at 25°C.
Br<br />
N<br />
N<br />
N R 1<br />
OH<br />
Br<br />
N<br />
N<br />
N R 1<br />
OH<br />
Figure-1A: Effect of the length of the n-alkyl chain at the 1-position of 2-hydroxy-2-<br />
phenyl-2,3-dihydro-imidazo[1,2-a]pyrimidinium salts, substituted with Cl and H at<br />
the para-position of the 2-phenyl ring, on the IC50 (µM) for inhibition of biofilm<br />
formation of S. Typhimurium ATCC14028.<br />
2.5.2.2 Further Modification in the most active core structure<br />
Since the compounds with a n-octyl chain substituted at the 1-position have the<br />
highest activity against Salmonella biofilms and also have a high activity against<br />
Pseudomonas biofilms, we decided to synthesize the additional 1-octyl-2-hydroxy-2phenyl-2,3-dihydro-imidazopyrimidinium<br />
salts with more variation in the substitution<br />
pattern of the 2-phenyl ring. As depicted in Table 5 these compounds generally inhibit<br />
biofilm formation of S. Typhimurium at low concentrations. However, no improved<br />
activity was observed in comparison with the previously described compounds (Table<br />
2). The effect of the n-octyl substituted compounds on the biofilm formation of P.<br />
aeruginosa strongly depends on the substitution pattern of the 2-phenyl ring, as some<br />
Cl
of the compounds have low IC50 values (10-40 µM), while the other compounds only<br />
have a moderate activity (IC50 = 100-400 µM).<br />
Br<br />
N<br />
N<br />
N C 8H 17<br />
OH<br />
R<br />
SR CODE R<br />
S. Typhimurium<br />
IC50<br />
P. aeruginosa<br />
IC50<br />
1 BS-180 4-NO2 6.6 12.1<br />
2 BS-176 4-F 7.6 nd<br />
3 BS-175 4-OMe 10.5 nd<br />
4 BS-177 3,4-diCl 7.1 nd<br />
5 BS-187 4-SMe 13.2 36.5<br />
6 BS-179 Naphtyl 14.7 15.1<br />
7 BS-185 4-(4-NO2Ph) 31 215.2<br />
8 BS-186 4-SO2Me 60.3 99.9<br />
9 BS-188 4-([1,1’-biphenylyl]-4-yl) 52.8 336.1<br />
10 BS-178 3-Br 7.1 29<br />
Table-5: Influence of N1-octyl 2-hydroxy-2, 3-dihydro-imidazo[1,2-a]pyrimidinium<br />
salts on the biofilm formation of S. Typhimurium ATCC14028 and P. aeruginosa<br />
PA14 at 25°C.<br />
2.5.2.3 Cyclo-alkyl substituents at 1-position<br />
A series of 2-hydroxy-2-phenyl-2,3-dihydro-imidazopyrimidinium salts with a broad<br />
variety of cyclo-alkyl substituents at the 1-position was synthesized with lengths<br />
ranging from 3 to 12 carbon atoms (Table 6). The 2-phenyl group of these salts was<br />
either unsubstantiated or para-substituted with a chlorine atom. Similarly to the<br />
structure-activity relationship delineated for the n-alkyl substituted salts, a gradual<br />
increase in the inhibitory activity against Salmonella biofilms was observed by rising<br />
the length of the cyclo-alkyl chain from 3 to 8 carbon atoms. However, in contrast to<br />
the salts with n-dodecyl chain at the 1-position, the salts with a cyclo-dodecyl chain
do have a very strong effect against Salmonella biofilms (IC50 values < 6.25 µM). By<br />
analogy with (1) the effect on Salmonella biofilms and (2) the activity of the n-alkyl<br />
substituted salts, we found that all the cyclo-alkyl substituted salts with a short side<br />
chain do only have a slight effect on the biofilm formation of P. aeruginosa (IC50’s<br />
>150 µM), while the compounds with a medium length side chain have a stronger<br />
biofilm inhibitory activity. The salts with a cyclo-dodecyl chain do drastically reduce<br />
the Pseudomonas biofilm formation (IC50’s ~7 µM), in sharp contrast to the<br />
compounds with n-dodecyl side chain.<br />
Br<br />
N<br />
N<br />
N R 1<br />
OH<br />
R 2<br />
SR CODE R2 R1<br />
S. Typhimurium<br />
IC50<br />
P. aeruginosa<br />
IC50<br />
1 BS-079 H c-Bu 493.0 >400<br />
2 BS-076 H c-Hex 139.0 22.4<br />
3 BS-046 H c-Hep 84.2 191.3<br />
4 BS-043 H c-Oct 58.4 48.6<br />
5 BS-100 4-Cl c-Bu 120.8 371.5<br />
6 BS- 4-Cl c-Pen 41.8 41.9<br />
7 BS-098 4-Cl c- Hex 33.0 16.4<br />
8 BS-088 4-Cl c- Hep 27.9 76.2<br />
9 BS-087 4-Cl c-Oct 12.6 22.7<br />
10 BS-086 4-Cl c-Doc 5.6 6.8<br />
Table-6: Influence of 1-cyclo-alkyl-2-hydroxy-2,3-dihydro-imidazo[1,2-a]<br />
pyrimidinium salts on the biofilm formation of S. Typhimurium ATCC14028 and P.<br />
aeruginosa PA14 at 25°C.<br />
2.5.3 2N-substituted 2-aminoimidazoles<br />
In the present it was interesting to investigate whether introduction of n-alkyl, isoalkyl,<br />
cyclo-alkyl or aromatic group at the 2N-position of the 4(5)-phenyl-2-amino-
1H-imidazoles could also enhance their biofilm inhibitory activity. Therefore a broad<br />
range of 2N-substituted 4(5)-phenyl-2-amino-1H-imidazoles were synthesized.<br />
An array of 4(5)-phenyl-2-aminoimidazoles 2N-substituted with either a short n- or<br />
iso-alkyl chain (C1-C5) or n-octyl chain was synthesized. As depicted in table7, a<br />
broad diversity of (substituted) 4(5)-phenyl groups were included. The compounds<br />
with a iso-butyl substitution at the 2N-position were found to be in general more<br />
active than their 2N-unsubstituted counterparts, with respect to both the Salmonella<br />
and Pseudomonas biofilm formation.<br />
SR R1<br />
R1 HN<br />
R2<br />
N<br />
N<br />
H<br />
R 2<br />
S. Typhimurium<br />
IC50<br />
P. aeruginosa<br />
IC50<br />
1 CH3 2,4-(di-OCH3) Nd Nd<br />
2<br />
(benzo[d][1,3]dioxol-<br />
6-yl)methyl<br />
naphthalen-1-yl 261.0 10.5<br />
3 C3H7 3,4-(di-Cl) 10.9 27.7<br />
4 Cyclohexane 4-SO2Me Nd Nd<br />
5 C8H17 4-Cl >400 Nd<br />
6 C5H11 4-Cl >400 Nd<br />
7 C6H13 4-F >400 12.5<br />
8 C8H17 4-OCH3 >400 >800<br />
9 C8H17 4-F >400 Nd<br />
10 C8H17 3,4-(di-Cl) 118.3 >800<br />
11 C8H17 3-Br 44.6 >800<br />
12 C8H17 naphthalen-1-yl 238.4 >800<br />
13 C8H17 4-NO2 10.9 25.0<br />
14 C8H17 4-(4-NO2Ph) Nd Nd<br />
15 C8H17 SO2Me 41.8 Nd<br />
16 i-Bu 4-NO2 3.8 22.9<br />
17 i-Bu H 4.9 1.2<br />
18 i-Bu 4-Br 2.9 1.2<br />
19 i-Bu 4-Cl 2.0 0.9<br />
Table-7: Influence of 2N-alkylated 2-aminoimidazoles on the biofilm formation and<br />
the planktonic growth of S. Typhimurium ATCC14028 and P. aeruginosa PA14 at<br />
25°C.
2.6 Conclusion<br />
In the present study, the potential of these 1-substituted 2-hydroxy-2,3-dihydroimidazopyrimidinium<br />
salts and 2N-subsituted 2-amino-1H-imidazoles as inhibitors of<br />
the biofilm formation by S. Typhimurium and P. aeruginosa was thoroughly<br />
investigated. We found that 2-hydroxy-2,3-dihydro-imidazopyrimidinium salts with<br />
intermediate length n-alkyl chains (C7-C10) substituted at the 1-position in general<br />
prevent the biofilm formation of both species at low micromolar concentrations (IC50<br />
= 5-50 µM). For these molecules, the nature of the substituent of the 2-phenyl group<br />
does not have a substantial effect on the biofilm inhibitory activity. Salts with a<br />
shorter (C1-C5) or longer (C11-C14) n-alkyl chain at the 1-position were found to be<br />
much less potent. Consistent with this, we observed that salts with an intermediate<br />
length cyclo-alkyl chain are much more active against biofilm formation of both<br />
species as compared to the salts with a short cyclo-alkyl chain. However, remarkably<br />
salts with a long cyclo-dodecyl side chain were found to have even better activities<br />
than salts with an intermediate length cyclo-alkyl side chain.<br />
In the framework of the 2-aminoimidazoles, be the introduction of a butyl, pentyl or<br />
hexyl side chain at the 2N-position of the 2-aminoimdazoles results in an enhanced<br />
biofilm inhibitory activity against both species, while introduction of a shorter n-alkyl<br />
chain reduces the biofilm inhibitory activity. The effect of introduction of longer nalkyl<br />
chains however seems to be strongly dependent on the substitution pattern of the<br />
5-phenyl ring and the bacterial species studied.<br />
In conclusion, the 2N-substituted 2-aminoimidazoles and 2-hydroxy-2-phenyl-2,3dihydro-imidazopyrimidinium<br />
salts of the present study are valuable candidates in the<br />
development of therapeutics and sanitizers for the combat of biofilm formation by S.<br />
Typhimurium, P. aeruginosa and possibly other pathogenic bacteria.
2.7 Experimental<br />
2.7.1 General Methods<br />
All chemical reagents were used without further purification. Solvents for column<br />
chromatography and TLC were laboratory grade and distilled before use. For thinlayer<br />
chromatography (TLC), analytical TLC plates (Alugram SIL G/UV254 (E. M.<br />
Merk) were used. Column chromatography was performed with flash silica gel (100-<br />
200 mesh) or neutral alumina oxide (50-200 micron). 1 H and 13 C NMR spectra were<br />
recorded on a Bruker Avance 300 (300 MHz) or a Bruker AMX-400 (400 MHz)<br />
spectrometers. NMR samples were run in the indicated solvents and were referenced<br />
internally. Chemical shift values were quoted in ppm and coupling constants were<br />
quoted in Hz. Chemical shift multiplicities were reported as s = singlet, d = doublet, t<br />
= triplet, q = quartet, m = multiplet and br = broad. Low-resolution mass spectra were<br />
recorded on a HEWLETT-PACKARD instrument (CI or EI) and LCQ Advantage<br />
instrument (ESI). High-resolution mass spectra (EI) were recorded on a KRATOS<br />
MS50TC instrument. Melting points were determined using Reichert-Jung Thermovar<br />
apparatus and were uncorrected.<br />
2.7.2 Microwave Irradiation Experiments<br />
Microwave irradiation experiments were carried out in a dedicated CEM-Discover<br />
mono-mode microwave apparatus or Milestone MicroSYNTH multi-mode microwave<br />
reactor (Laboratory Microwave Systems). Microwave apparatuses were used in the<br />
standard configuration as delivered, operating at a frequency 2.45 GHz with<br />
continuous irradiation power from 0 to 400 W. The reactions were carried out in 10,<br />
20, 30 and 50 mL glass tubes. The temperature was measured with an IR sensor on<br />
the outer surface of the process vial or fibre optic sensor inside the process vial. After<br />
the irradiation period, the reaction vessel was cooled rapidly (2-5 min) to ambient<br />
temperature by air jet cooling.
2.8 Biological assays<br />
2.8.1 Static peg assay for prevention of Salmonella Typhimurium and<br />
Pseudomonas aeruginosa biofilm formation<br />
The device used for biofilm formation is a platform carrying 96 polystyrene pegs<br />
(Nunc no. 445497) that fits as a microtiter plate lid with a peg hanging into each<br />
microtiter plate well (Nunc no. 269789). Two-fold serial dilutions of the compounds<br />
in 100 µl liquid broth (Tryptic Soy Broth diluted 1/20 (TSB 1/20)) per well were<br />
prepared in the microtiter plate (2 or 3 repeats per compound). Subsequently, an<br />
overnight culture of S. Typhimurium ATCC14028 (grown in Luria-Bertani medium)<br />
or P. aeruginosa (grown in TSB) was diluted 1:100 into the respective liquid broth<br />
and 100 µl (~10 6 cells) was added to each well of the microtiter plate, resulting in a<br />
total amount of 200 µl medium per well. The pegged lid was placed on the microtiter<br />
plate and the plate was incubated for 24 h at 25°C without shaking. During this<br />
incubation period biofilms were formed on the surface of the pegs. After 24 h, the<br />
optical density at 600 nm (OD600) was measured for the planktonic cells in the<br />
microtiter plate using a VERSAmax microtiter plate reader (Molecular Devices). This<br />
gives a first indication of the effect of the compounds on the planktonic growth. For<br />
quantification of biofilm formation, the pegs were washed once in 200 µl phosphate<br />
buffered saline (PBS). The remaining attached bacteria were stained for 30 min with<br />
200 μl 0.1% (w/v) crystal violet in an isopropanol/methanol/PBS solution (v/v<br />
1:1:18). Excess stain was rinsed off by placing the pegs in a 96-well plate filled with<br />
200 μl distilled water per well. After the pegs were air dried (30 min), the dye bound<br />
to the adherent cells was extracted with 30% glacial acetic acid (200 µl). The OD570 of<br />
each well was measured using a VERSAmax microtiter plate reader (Molecular<br />
Devices). The IC50 value for each compound was determined from the concentration<br />
gradient by using the GraphPad software of Prism.
2.8.2 Bioscreen assay for measuring Salmonella Typhimurium and P.<br />
aeruginosa growth inhibition<br />
The Bioscreen device (Oy Growth Curves Ab Ltd) was used for measuring the<br />
influence of the chemical compounds on the planktonic growth of Salmonella<br />
Typhimurium and P. aeruginosa. The Bioscreen is a computer controlled<br />
incubator/reader/shaker that uses 10x10 well microtiter plates and measures light<br />
absorbance of each well at a specified wave length in function of time. An overnight<br />
culture of S. Typhimurium ATCC14028 (grown up in LB medium) or P. aeruginosa<br />
(grown up in TSB) was diluted 1:200 in liquid broth (TSB 1/20). 300 µl of the diluted<br />
overnight culture was added to each well of the 10x10 well microtiter plate.<br />
Subsequently, serial dilutions of the chemical compounds were prepared in DMSO or<br />
EtOH. 3 µl of each diluted stock solution was added to the wells (containing the 300<br />
µl bacterial culture) in 3-fold. As a control 3 µl of the appropriate solvent was also<br />
added to the plate in 3- or 4-fold. The microtiter plate was incubated in the Bioscreen<br />
device at 25°C for at least 24 h, with continuous medium shaking. The absorbance of<br />
each well was measured at 600 nm each 15 min. Excel was used to generate the<br />
growth curves for the treated wells and the untreated control wells.<br />
The effect of each compound concentration on the planktonic growth was classified<br />
into one of the following categories:<br />
1) The planktonic growth is not or only slightly affected, indicated by the symbol<br />
‘-‘.<br />
2) The planktonic growth is retarded, indicated by the symbol ‘+’.<br />
3) The planktonic growth is completely or almost completely inhibited, indicated<br />
by the symbol ‘o’.<br />
The following criterium was used to decide between the first and the second category:<br />
If the absorbance (measured at 600 nm) of the bacterial culture treated with the<br />
compound is at least 0.5 (for Salmonella) or 0.8 (for Pseudomonas) units lower<br />
than the absorbance of the untreated culture during 4 consecutive hours, then the<br />
effect on the planktonic growth is classified in category 2.
2.9 Experimental protocol:<br />
2.9.1 General Procedure for the Preparation of Substituted 2-<br />
Aminopyrimidines<br />
In a 50 mL microwave vial were successively dissolved in EtOH (20 mL) 2chloropyrimidine<br />
(3.43 g, 30 mmol), amine (39 mmol, 1.3 equiv) and triethylamine<br />
(6.2 mL, 45 mmol, 1.5 equiv). The reaction tube was sealed, and irradiated in the<br />
cavity of a Milestone MicroSYNTH microwave reactor at a ceiling temperature of<br />
120 °C at 100 W maximum power for 25 min. After the reaction mixture was cooled<br />
with an air flow for 15 min, it was diluted with water (100 mL), extracted with DCM<br />
(2×150 mL) and dried over Na2SO4. The solvent was evaporated in vacuo, and the<br />
crude mixture was purified by silica gel flash chromatography using 0-5%<br />
MeOH−DCM as the eluent.<br />
13 new substituted 2-aminopyrimidine derivatives were synthesized in similar<br />
manner. (Table-1)<br />
Table-1 Compound synthesized<br />
N<br />
N<br />
N<br />
H R<br />
ENTRY CODE R Yield<br />
1 BS-021 cyclododecane 66<br />
2 BS -024 cyclooctane 60<br />
3 BS -025 cycloheptane 64<br />
4 BS -030 cyclobutane 61<br />
5 BS-029 C6H13 88<br />
6 BS -026 C7H15 87<br />
7 BS -027 C8H17 86<br />
8 BS -033 C9H19 86<br />
9 BS -028 C10H21 87<br />
10 BS -034 C11H23 88<br />
11 BS -035 C12H25 89<br />
12 BS -036 C13H27 88<br />
13 BS -037 C14H19 88
2.9.2 General Procedure for the Preparation of Salts.<br />
To a solution of 2-substituted aminopyrimidine (6 mmol) and α-bromoacetophenone<br />
(7.2 mmol, 1.2 equiv) in acetonitrile (12 mL) was added 4-dimethylaminopyridine (6<br />
mg, 0.05 mmol). After being stirred at 85 °C for 5 h, the reaction mixture was diluted<br />
with acetone (20 mL) and the precipitate was filtered and washed with acetone (2×20<br />
mL), ether (2×20 mL) and dried over P2O5 to give salt as a white solid.<br />
10 new compounds were synthesized in similar manner.<br />
2.9.3 General Procedure for the Preparation of Salts. (Microwave)<br />
In a 50 mL microwave vial were successively dissolved 2-substituted<br />
aminopyrimidine (6 mmol) and α-bromoacetophenone (7.2 mmol, 1.2 equiv) in<br />
acetonitrile (12 mL) was added 4-dimethylaminopyridine (6 mg, 0.05 mmol). The<br />
reaction tube was sealed, and irradiated in the cavity of a Milestone MicroSYNTH<br />
microwave reactor at a ceiling temperature of 80 °C at 100 W maximum power for 30<br />
min. After the reaction mixture was cooled with an air flow for 15 min, the reaction<br />
mixture was diluted with acetone (20 mL) and the precipitate was filtered and washed<br />
with acetone (2×20 mL), ether (2×20 mL) and dried over P2O5 to give salt as a white<br />
solid. 34 new compounds were synthesized in similar manner.<br />
2.9.4 General Procedure for the Preparation of 2-Amino-1H-imidazoles.<br />
To a suspension of salt (2 mmol) in MeCN (5 mL) hydrazine hydrate (0.7 mL, 14<br />
mmol of a 64% solution, 7 equiv) was added, and the mixture was irradiated in the<br />
sealed Milestone MicroSYNTH microwave reactor for 10 min at a ceiling<br />
temperature of 100 °C at 150 W maximum power. After cooling down hydrazine<br />
hydrate was evaporated with toluene (3×20 mL). The resulting residue was purified<br />
by column chromatography (silica gel; MeOH−DCM 1:4 v/v with 5% of 6M NH3 in<br />
MeOH) to afford 2-amino-1H-imidazole as an amorphous material.<br />
12 new compounds were synthesized in similar manner.<br />
2.9.5 General procedure for the one-pot two-step microwave-assisted synthesis<br />
of 2-amino-1H-imidazoles.<br />
In a microwave vial (10 mL) were successively dissolved in dry MeCN (3 mL) the<br />
corresponding 2-aminopyrimidine (4 mmol) and α-bromoketone (4.6 mmol). The<br />
reaction tube was sealed and irradiated in a microwave reactor at a ceiling
temperature of 80 °C and a maximum power of 50 W for 30 min. After the reaction<br />
mixture was cooled with an air flow for 15 min, hydrazine hydrate (0.9 mL, 28 mmol<br />
of a 64% solution, 7 equiv) was added, and the mixture was irradiated at a ceiling<br />
temperature of 90 °C and a maximum power of 50 W for another 10 min. After the<br />
reaction mixture was cooled, hydrazine hydrate was removed by distillation with<br />
toluene (3×20 mL). The resulting residue was purified by column chromatography<br />
(silica gel; MeOH-DCM 1:9 v/v with 0.5 % of 6N ammonia in MeOH) to afford 2amino-1H-imidazole<br />
as amorphous solid.<br />
10 new compounds were synthesized in similar manner.<br />
2.10 Spectral Characterization<br />
N-Cyclooctylpyrimidin-2-amine (BS-024)<br />
N<br />
N<br />
N<br />
H<br />
Yield: 60%. 1 H NMR (300 MHz, CDCl3): δ = 8.25 (d, J = 4.77 Hz, 2H), 6.46 (t, J =<br />
4.8 Hz, 1H), 5.07 (br s, 1H), 4.04 (m, 1H), 1.93 (m, 2H), 1.63 (m, 12H). 13 C NMR<br />
(75.5 MHz, CDCl3): δ =161.6, 158.0 (×2), 110.0, 50.6, 31.7 (×2), 27.5 (×2), 25.3,<br />
23.5 (×2). HRMS (EI): C12H19N3, calcd 205.2994, found: 205.2982.<br />
N –Cycloheptylpyrimidin-2-amine (BS-025)<br />
N<br />
N<br />
N<br />
H<br />
Yield: 64%. 1 H NMR (300 MHz, CDCl3): δ = 8.26 (d, J = 4.77 Hz, 2H), 6.47 (t, J =<br />
4.77 Hz, 1H), 5.09 (br s, 1H), 4.01 (m, 1H), 2.02 (m, 2H), 1.55 (m, 10H). 13 C NMR<br />
(75.5 MHz, CDCl3): δ =161.6, 158.0 (×2), 110.0, 51.6, 35.0 (×2), 28.2 (×2), 23.9<br />
(×2). HRMS (EI): C11H17N3, calcd 191.2728, found: 191.2742.<br />
N –Heptylpyrimidin-2-amine (BS-026)<br />
N<br />
N<br />
N<br />
H<br />
C 7H 15<br />
Yield: 87%. 1 H NMR (300 MHz, CDCl3): δ = 8.27 (d, J = 4.8 Hz, 2H), 6.50 (t, J = 4.8<br />
Hz, 1H), 5.07 (br s, 1H), 3.40 (m, 2H), 1.61 (m, 2H), 1.31 (m, 8H), 0.85 (m 3H). 13 C
NMR (75.5 MHz, CDCl3): δ =162.5, 157.9 (×2), 110.1, 41.5, 31.8, 29.6, 29.0, 26.9,<br />
22.6, 14.0. HRMS (EI): C11H19N3, calcd 193.2887, found: 193.2894.<br />
N –Octylpyrimidin-2-amine (BS-027)<br />
N<br />
N<br />
N<br />
H<br />
C 8H 17<br />
Yield: 86%. 1 H NMR (300 MHz, CDCl3): δ = 8.27 (d, J = 4.74 Hz, 2H), 6.49 (t, J =<br />
4.77 Hz, 1H), 5.11 (br s, 1H), 3.40 (m, 2H), 1.60 (m, 2H), 1.27 (m, 10H), 0.87 (m<br />
3H). 13 C NMR (75.5 MHz, CDCl3): δ =162.4, 158.0 (×2), 110.1, 41.5, 31.8, 29.6,<br />
29.3, 29.2, 26.9, 22.6, 14.1. HRMS (EI): C12H21N3, calcd 207.3152, found: 207.3131.<br />
N –Decylpyrimidin-2-amine (BS-028)<br />
N<br />
N<br />
N<br />
H<br />
C 10H 21<br />
Yield: 87%. 1 H NMR (300 MHz, CDCl3): δ = 8.27 (d, J = 4.8 Hz, 2H), 6.50 (t, J = 4.8<br />
Hz, 1H), 5.07 (br s, 1H), 3.38 (m, 2H), 1.60 (m, 2H), 1.26 (m, 14H), 0.87 (t, J = 6.93,<br />
3H). 13 C NMR (75.5 MHz, CDCl3): δ =162.4, 158.0 (×2), 110.1, 41.5, 31.8, 29.6 (×2),<br />
29.5, 29.3 (×2), 26.9, 22.6, 14.1. HRMS (EI): C14H25N3, calcd 235.3684, found:<br />
235.3670.<br />
N –Cyclobutylpyrimidin-2-amine (BS-030)<br />
N<br />
N<br />
N<br />
H<br />
Yield: 61%. 1 H NMR (300 MHz, CDCl3): δ = 8.27 (m, 2H), 6.51 (t, J = 4.77 Hz, 1H),<br />
5.29 (br s, 1H), 4.46 (m, 1H), 2.42 (m, 2H), 1.89 (m, 2H), 1.76 (m, 2H). 13 C NMR<br />
(75.5 MHz, CDCl3): δ =161.6, 158.0 (×2), 110.4, 46.3, 31.5 (×2), 15.0. HRMS (EI):<br />
C8H11N3, calcd 149.1930, found: 149.1917<br />
N –Nonylpyrimidin-2-amine (BS-033)<br />
N<br />
N<br />
N<br />
H<br />
C 9H 19<br />
Yield: 86%. 1 H NMR (300 MHz, CDCl3): δ = 8.27 (d, J = 4.71 Hz, 2H), 6.50 (t, J =<br />
4.77 Hz, 1H), 5.07 (br s, 1H), 3.40 (m, 2H), 1.61 (m, 2H), 1.26 (m, 12H), 0.87 (t, J =<br />
6.9, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =162.5, 158.0 (×2), 110.1, 41.5, 31.8, 29.6,
29.5,29.4, 29.2, 27.0, 22.6, 14.1. HRMS (EI): C13H23N3, calcd 221.3418, found:<br />
221.3400.<br />
N –Undecylpyrimidin-2-amine (BS-034)<br />
N<br />
N<br />
N<br />
H<br />
C 11H 23<br />
Yield: 88%. 1 H NMR (300 MHz, CDCl3): δ = 8.27 (d, J = 4.62 Hz, 2H), 6.50 (t, J =<br />
4.77 Hz, 1H), 5.07 (br s, 1H), 3.40 (m, 2H), 1.60 (m, 2H), 1.25 (m, 16H), 0.87 (t, J =<br />
6.87, 3H). 13 C NMR (75.5 MHz, CDCl3): δ = 162.5, 158.0 (×2), 110.2, 41.5, 31.9,<br />
29.6 (×4), 29.3 (×2), 26.9, 22.6, 14.1. HRMS (EI): C15H27N3, calcd 249.3950, found:<br />
249.3938.<br />
N –Dodecylpyrimidin-2-amine (BS-035)<br />
N<br />
N<br />
N<br />
H<br />
C 12H 25<br />
Yield: 89%. 1 H NMR (300 MHz, CDCl3): δ = 8.27 (d, J = 4.41 Hz, 2H), 6.50 (t, J =<br />
4.74 Hz, 1H), 5.07 (br s, 1H), 3.40 (m, 2H), 1.61 (m, 2H), 1.25 (m, 18H), 0.88 (t, J =<br />
6.84, 3H). 13 C NMR (75.5 MHz, CDCl3): δ = 162.4, 158.0 (×2), 110.2, 41.5, 31.9,<br />
29.6 (×5), 29.3 (×2), 26.9, 22.6, 14.1. HRMS (EI): C16H29N3, calcd 263.4216, found:<br />
263.4202.<br />
N –Tridecylpyrimidin-2-amine (BS-036)<br />
N<br />
N<br />
N<br />
H<br />
C 13H 27<br />
Yield: 88%. 1 H NMR (300 MHz, CDCl3): δ = 8.27 (d, J = 4.77 Hz, 2H), 6.50 (t, J =<br />
4.8 Hz, 1H), 5.07 (br s, 1H), 3.38 (m, 2H), 1.60 (m, 2H), 1.25 (m, 20H), 0.88 (t, J =<br />
6.9, 3H). 13 C NMR (75.5 MHz, CDCl3): δ = 162.4, 158.0 (×2), 110.1, 41.5, 31.9, 29.6<br />
(×6), 29.3 (×2), 27.0, 22.7, 14.1. HRMS (EI): C17H31N3, calcd 277.4481, found:<br />
277.4491.<br />
N –Tetradecylpyrimidin-2-amine (BS-037)<br />
N<br />
N<br />
N<br />
H<br />
C 14H 29
Yield: 88%. 1 H NMR (300 MHz, CDCl3): δ = 8.27 (d, J = 4.77 Hz, 2H), 6.50 (t, J =<br />
4.8 Hz, 1H), 5.07 (br s, 1H), 3.38 (m, 2H), 1.60 (m, 2H), 1.25 (m, 22H), 0.88 (t, J =<br />
6.9, 3H). 13 C NMR (75.5 MHz, CDCl3): δ = 162.4, 158.0 (×2), 110.2, 41.5, 31.9, 29.6<br />
(×7), 29.3 (×2), 26.9, 22.7, 14.1. HRMS (EI): C18H33N3, calcd 291.4747, found:<br />
291.4723.<br />
1-Heptyl-2-hydroxy-2-phenyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-4-ium<br />
bromide amine (BS-049)<br />
N<br />
Br<br />
N<br />
N C 7H 15<br />
OH<br />
Yield: 75 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (m, 1H), 8.85 (m, 1H), 7.80 (s,<br />
1H), 7.77 (m, 2H), 7.49 (m, 3H), 7.31 (m, 1H), 4.82 (s, 2H). 3.17 (m, 2H), 1.36 (m,<br />
2H), 1.09 (m, 8H), 0.80 (t, J = 6.84 Hz, 3H).<br />
2-Hydroxy-1-octyl-2-phenyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-4-ium<br />
bromide (BS-052)<br />
N<br />
Br<br />
N<br />
N C 8H 17<br />
OH<br />
Yield: 73 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (m, 1H), 8.86 (m, 1H), 7.80 (s,<br />
1H), 7.75 (m, 2H), 7.47 (m, 3H), 7.31 (t, J = 5.49 Hz, 1H), 4.83 (s, 2H). 3.17 (m, 2H),<br />
1.36 (m, 2H), 1.09 (m, 10H), 0.83 (t, J = 6.72 Hz, 3H).<br />
1-Decyl-2-hydroxy-2-phenyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-4-ium<br />
bromide (BS-055)<br />
N<br />
Br<br />
N<br />
N C 10H 21<br />
OH
Yield: 78 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (d, J = 4.62 Hz, 1H), 8.87 (d, J =<br />
6.18 Hz, 1H), 7.81 (s, 1H), 7.74 (m, 2H), 7.47 (m, 3H), 7.31 (m, 1H), 4.83 (s, 2H).<br />
3.17 (m, 2H), 1.09 (m, 16H), 0.85 (t, J = 6.51 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3):<br />
δ =167.5, 154.5, 148.2, 138.2, 129.2, 128.3 (×2), 126.9 (×2), 111.1, 90.6, 62.6, 40.7,<br />
31.2, 28.7, 28.6, 28.5, 28.2, 27.3, 25.8, 22.0, 13.9.<br />
1-Hexyl-2-hydroxy-2-phenyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-4-ium<br />
bromide (BS-058)<br />
N<br />
Br<br />
N<br />
N C 6H 13<br />
OH<br />
Yield: 80 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (m, 1H), 8.87 (m, 1H), 7.81 (s,<br />
1H), 7.74 (m, 2H), 7.47 (m, 3H), 7.31 (m 1H), 4.83 (s, 2H). 3.17 (m, 2H), 1.34 (m,<br />
2H), 1.09 (m, 6H), 0.78 (t, J = 6.48 Hz, 3H).<br />
2-Hydroxy-1-nonyl-2-phenyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-4-ium<br />
bromide (BS-061)<br />
N<br />
Br<br />
N<br />
N C 9H 19<br />
OH<br />
Yield: 75 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (m, 1H), 8.87 (m, 1H), 7.80 (s,<br />
1H), 7.74 (m, 2H), 7.47 (m, 3H), 7.31 (t, J = 6.21 Hz, 1H), 4.83 (s, 2H). 3.17 (m, 2H),<br />
1.09 (m, 14H), 0.84 (t, J = 6.63 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =167.5,<br />
154.5, 148.2, 138.2, 129.2, 128.3 (×2), 126.9 (×2), 111.1, 90.6, 62.6, 40.7, 31.1, 28.5,<br />
28.4, 28.2, 27.3, 25.8, 22.0, 13.9.<br />
2-Hydroxy-2-phenyl-1-undecyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-4-ium<br />
bromide (BS-064)<br />
N<br />
Br<br />
N<br />
N C 11H 23<br />
OH
Yield: 80 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (d of d, J = 1.89, 4.68 Hz, 1H),<br />
8.87 (d, J = 6.06 Hz, 1H), 7.80 (s, 1H), 7.75 (m, 2H), 7.47 (m, 3H), 7.31 (m 1H), 4.83<br />
(s, 2H). 3.17 (m, 2H), 1.09 (m, 18H), 0.85 (t, J = 6.42 Hz, 3H).<br />
1-Dodecyl-2-hydroxy-2-phenyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-4-ium<br />
bromide (BS-067)<br />
N<br />
Br<br />
N<br />
N C 12H 25<br />
OH<br />
Yield: 78 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (m, 1H), 8.87 (m, 1H), 7.81 (s,<br />
1H), 7.74 (m, 2H), 7.46 (m, 3H), 7.31 (m, 1H), 4.84 (s, 2H). 3.17 (m, 2H), 1.22 (m,<br />
20H), 0.85 (t, J = 6.24 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =167.5, 154.5,<br />
148.2, 138.2, 129.2, 128.3 (×2), 126.9 (×2), 111.1, 90.6, 62.6, 40.7, 31.2, 28.9 (×2),<br />
28.8, 28.6 (×2), 28.2, 27.3, 25.8, 22.0, 13.9.<br />
2-Hydroxy-2-phenyl-1-tridecyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-4-ium<br />
bromide (BS-070)<br />
N<br />
Br<br />
N<br />
N C 13H 27<br />
OH<br />
Yield: 79 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (m, 1H), 8.87 (m, 1H), 7.80 (s,<br />
1H), 7.76 (m, 2H), 7.46 (m, 3H), 7.31 (m 1H), 4.83 (s, 2H). 3.17 (m, 2H), 1.22 (m,<br />
22H), 0.85 (m, 3H).<br />
2-Hydroxy-2-phenyl-1-tetradecyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-4-ium<br />
bromide (BS-073)
N<br />
Br<br />
N<br />
N C 14H 29<br />
OH<br />
Yield: 72 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (d, J = 4.65 Hz, 1H), 8.87 (d, J =<br />
6.27 Hz, 1H), 7.81 (s, 1H), 7.77 (m, 2H), 7.46 (m, 3H), 7.32 (m 1H), 4.84 (s, 2H).<br />
3.17 (m, 2H), 1.23 (m, 24H), 0.85 (m, 3H).<br />
1-Cyclobutyl-2-hydroxy-2-phenyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-4ium<br />
bromide (BS-079)<br />
N<br />
Br<br />
N<br />
N<br />
OH<br />
Yield: 77 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (m, 1H), 8.83 (m, 1H), 7.86 (s,<br />
1H), 7.65(m, 2H), 7.46(m, 3H), 7.34 (m 1H), 4.76 (s, 2H). 3.90 (m, 1H), 2.76 (m,<br />
2H), 1.88 (m, 2H), 1.69 (m, 2H).<br />
2-Hydroxy-1-pentyl-2-phenyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-4-ium<br />
bromide (BS-083)<br />
N<br />
Br<br />
N<br />
N C 5H 11<br />
OH<br />
Yield: 74 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (m, 1H), 8.86 (m, 1H), 7.82 (s,<br />
1H), 7.77 (m, 2H), 7.47 (m, 3H), 7.31 (m 1H), 4.83 (s, 2H). 3.17 (m, 2H), 1.36, (m,<br />
2H), 1.09 (m, 4H), 0.73 (t, J = 6.72 Hz, 3H).<br />
2-(4-Chlorophenyl)-1-cycloheptyl-2-hydroxy-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-088)<br />
N<br />
Br<br />
N<br />
N<br />
OH<br />
Cl
Yield: 90 %. 1 H NMR (300 MHz, CDCl3): δ = 9.00 (d of d, J = 1.92, 4.65 Hz, 1H),<br />
8.85 (m, 1H), 7.92 (s, 1H), 7.79 (d, J = 8.64 Hz, 2H), 7.56 (d, J = 8.58 Hz, 2H), 7.28<br />
(m, 1H), 4.74 (m, 2H). 3.10 (m, 1H), 2.19 (m, 2H), 1.40 (m, 10H).<br />
2-(4-Chlorophenyl)-1-heptyl-2-hydroxy-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-089)<br />
N<br />
Br<br />
N<br />
N C 7H 15<br />
OH<br />
Cl<br />
Yield: 91 %. 1 H NMR (300 MHz, CDCl3): δ = 9.04 (d, J = 4.65 Hz, 1H), 8.87 (d, J =<br />
5.85 Hz, 1H), 7.90 (s, 1H), 7.78 (d, J = 8.61 Hz, 2H), 7.55 (d, J = 8.58 Hz, 2H), 7.32<br />
(m, 1H), 4.82 (s, 2H). 3.17 (m, 2H), 1.09 (m, 10H), 0.81 (t, J = 7.17 Hz, 3H).<br />
2-(4-Chlorophenyl)-2-hydroxy-1-octyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-<br />
4-ium bromide (BS-090)<br />
N<br />
Br<br />
N<br />
N C 8H 17<br />
OH<br />
Cl<br />
Yield: 71 %. 1 H NMR (300 MHz, CDCl3): δ = 9.05 (d, J = 6.51 Hz, 1H), 8.90 (d, J =<br />
6.24 Hz, 1H), 7.90 (s, 1H), 7.78 (d, J = 8.61 Hz, 2H), 7.55 (d, J = 8.58 Hz, 2H), 7.32<br />
(m, 1H), 4.82 (m, 2H). 3.17 (m, 2H), 1.09 (m, 12H), 0.83 (t, J = 6.75 Hz, 3H).<br />
2-(4-Chlorophenyl)-1-decyl-2-hydroxy-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-<br />
4-ium bromide (BS-091)<br />
N<br />
Br<br />
N<br />
N C 10H 21<br />
OH<br />
Cl<br />
Yield: 86 %. 1 H NMR (300 MHz, CDCl3): δ = 9.04 (d, J = 3.33 Hz, 1H), 8.86 (d, J =<br />
6.0 Hz, 1H), 7.89 (s, 1H), 7.81 (d, J = 8.37 Hz, 2H), 7.55 (d, J = 8.4 Hz, 2H), 7.32 (m,<br />
1H), 4.82 (m, 2H). 3.17 (m, 2H), 1.09 (m, 16H), 0.85 (t, J = 6.51 Hz, 3H). 13 C NMR
(75.5 MHz, CDCl3): δ = 167.7, 154.6, 148.2, 137.3, 134.1, 129.0 (×2), 126.3 (×2),<br />
111.1, 90.2, 62.5, 40.7, 31.2, 28.8, 28.6 (×2), 28.2, 27.2, 25.8, 22.0, 13.9.<br />
2-(4-Chlorophenyl)-1-hexyl-2-hydroxy-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-<br />
4-ium bromide (BS-092)<br />
N<br />
Br<br />
N<br />
N C 6H 13<br />
OH<br />
Cl<br />
Yield: 83 %. 1 H NMR (300 MHz, CDCl3): δ = 9.04 (d, J = 4.47 Hz, 1H), 8.87 (d, J =<br />
6.3 Hz, 1H), 7.90 (s, 1H), 7.78 (d, J = 8.55 Hz, 2H), 7.56 (m, 2H), 7.33 (t, J = 5.0 Hz,<br />
1H), 4.82 (m, 2H). 3.17 (m, 2H), 1.05 (m, 8H), 0.79 (t, J = 6.30 Hz, 3H).<br />
2-(4-Chlorophenyl)-2-hydroxy-1-nonyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-<br />
4-ium bromide (BS-093)<br />
N<br />
Br<br />
N<br />
N C 9H 19<br />
OH<br />
Cl<br />
Yield: 82 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (d of d, J = 1.86, 4.62 Hz, 1H),<br />
8.86 (m, 1H), 7.89 (s, 1H), 7.78 (d, J = 8.64 Hz, 2H), 7.55 (d, J = 8.58 Hz, 2H), 7.32<br />
(m, 1H), 4.82 (m, 2H). 3.17 (m, 2H), 1.09 (m, 14H), 0.84 (t, J = 6.63 Hz, 3H).<br />
2-(4-Chlorophenyl)-2-hydroxy-1-undecyl-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-094)<br />
N<br />
Br<br />
N<br />
N C 11H 23<br />
OH<br />
Cl
Yield: 83 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (d, J = 4.56 Hz, 1H), 8.87 (d, J =<br />
6.3 Hz, 1H), 7.89 (s, 1H), 7.78 (d, J = 8.49 Hz, 2H), 7.55 (d, J = 8.49 Hz, 2H), 7.32<br />
(m, 1H), 4.82 (m, 2H). 3.17 (m, 2H), 1.22 (m, 18H), 0.85 (t, J = 6. 3 Hz, 3H). 13 C<br />
NMR (75.5 MHz, CDCl3): δ = 167.5, 154.6, 148.2, 137.3, 134.1, 129.0 (×2), 128.3<br />
(×2), 111.1, 90.2, 62.5, 40.7, 31.2, 28.9, 28.8, 28.6 (×2), 28.2, 27.2, 25.8, 22.0, 13.9.<br />
2-(4-Chlorophenyl)-1-dodecyl-2-hydroxy-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-095)<br />
N<br />
Br<br />
N<br />
N C 12H 25<br />
OH<br />
Cl<br />
Yield: 90 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (d of d, J = 1.83, 4.59 Hz, 1H),<br />
8.87 (d, J = 6.06 Hz, 1H), 7.90 (s, 1H), 7.78 (d, J = 8.64 Hz, 2H), 7.55 (d, J = 8.61<br />
Hz, 2H), 7.32 (m, 1H), 4.82 (m, 2H). 3.17 (m, 2H), 1.22 (m, 20H), 0.85 (t, J = 6. 33<br />
Hz, 3H).<br />
2-(4-Chlorophenyl)-2-hydroxy-1-tridecyl-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-096)<br />
N<br />
Br<br />
N<br />
N C 13H 27<br />
OH<br />
Cl<br />
Yield: 95 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (d of d, J = 1.83, 4.65 Hz, 1H),<br />
8.87 (d of d, J = 1.77, 6.27 Hz, 1H), 7.90 (s, 1H), 7.78 (d, J = 8.61 Hz, 2H), 7.55 (d, J<br />
= 8.61 Hz, 2H), 7.32 (m, 1H), 4.82 (m, 2H). 3.17 (m, 2H), 1.23 (m, 22H), 0.85 (t, J =<br />
6. 33 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ = 167.5, 154.6, 148.2, 137.2, 134.1,<br />
129.0 (×2), 128.3 (×2), 111.2, 90.2, 62.5, 40.7, 31.2, 28.9 (×3), 28.8, 28.6 (×2), 28.2,<br />
27.2, 25.8, 22.0, 13.9.<br />
2-(4-Chlorophenyl)-2-hydroxy-1-tetradecyl-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-097)
N<br />
Br<br />
N<br />
N C 14H 29<br />
OH<br />
Cl<br />
Yield: 90 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (d, J = 4.56 Hz, 1H), 8.87 (d J =<br />
6.12 Hz, 1H), 7.90 (s, 1H), 7.78 (d, J = 8.55 Hz, 2H), 7.55 (d, J = 8.55 Hz, 2H), 7.32<br />
(t, J = 4.95 Hz, 1H), 4.82 (m, 2H). 3.17 (m, 2H), 1.23 (m, 24H), 0.85 (t, J = 6. 09 Hz,<br />
3H).<br />
2-(4-Chlorophenyl)-1-cyclohexyl-2-hydroxy-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-098)<br />
N<br />
Br<br />
N<br />
N<br />
OH<br />
Cl<br />
Yield: 84 %. 1 H NMR (300 MHz, CDCl3): δ = 9.01 (d of d, J = 1.86, 4.68 Hz, 1H),<br />
8.84 (d of d, J = 1.83, 6.39 Hz, 1H), 7.96 (s, 1H), 7.78 (d, J = 8.64 Hz, 2H), 7.56 (d, J<br />
= 8.58 Hz, 2H), 7.30 (m, 1H), 4.72 (m, 2H). 3.02 (m, 1H), 2.13 (m, 2H), 0.75 (m, 8H).<br />
2-(4-Chlorophenyl)-2-hydroxy-1-pentyl-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-099)<br />
N<br />
Br<br />
N<br />
N C 5H 11<br />
OH<br />
Cl<br />
Yield: 78 %. 1 H NMR (300 MHz, CDCl3): δ = 9.04 (d of d, J = 1.8, 4.56 Hz, 1H),<br />
8.87 (d of d, J = 1.65, 6.27 Hz, 1H), 7.90 (s, 1H), 7.78 (d, J = 8.64 Hz, 2H), 7.56 (d, J<br />
= 8.61 Hz, 2H), 7.32 (m, 1H), 4.81 (m, 2H). 3.17 (m, 2H), 1.10 (m, 6H), 0.75 (t, J = 6.<br />
81 Hz, 3H).<br />
2-(4-Chlorophenyl)-1-cyclobutyl-2-hydroxy-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
(BS-100)
N<br />
Br<br />
N<br />
N<br />
OH<br />
Cl<br />
Yield: 81 %. 1 H NMR (300 MHz, CDCl3): δ = 9.06 (d, J = 4.11 Hz, 1H), 8.84 (d, J =<br />
6.21 Hz, 1H), 7.95 (s, 1H), 7.69 (d, J = 8.58 Hz, 2H), 7.55 (d, J = 8.55 Hz, 2H), 7.35<br />
(t, J = 5.22 Hz, 1H), 4.64 (m, 2H), 3.89 (m, 1H), 2.73 (m, 2H), 1.91 (m, 2H), 1.66 (m,<br />
2H).<br />
2-Hydroxy-2-(4-methoxyphenyl)-1-octyl-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-175)<br />
N<br />
Br<br />
N<br />
N C 8H 17<br />
OH<br />
OMe<br />
Yield: 77 %. 1 H NMR (300 MHz, CDCl3): δ = 9.02 (m, 1H), 8.84 (d, J = 6.3 Hz, 1H),<br />
7.71 (s, 1H), 7.65 (d, J = 8.79 Hz, 2H), 7.30 (m, 2H), 7.01 (d, J = 8.79 Hz, 1H), 4.79<br />
(s, 2H). 3.79 (s, 3H), 3.17 (m, 2H), 1.10 (m, 12H), 0.83 (t, J = 6.66 Hz, 3H). 13 C NMR<br />
(75.5 MHz, CDCl3): δ = 167.4, 159.7, 154.4, 148.2, 129.8, 128.4 (×2), 113.5 (×2),<br />
111.0, 90.5, 62.5, 55.2, 40.5, 31.0, 28.2 (×2), 27.3, 25.8, 22.0, 13.8.<br />
2-(4-Fluorophenyl)-2-hydroxy-1-octyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-<br />
4-ium bromide (BS-176)<br />
N<br />
Br<br />
N<br />
N C 8H 17<br />
OH<br />
F<br />
Yield: 68 %. 1 H NMR (300 MHz, CDCl3): δ = 9.03 (d of d, J = 1.92, 4.71 Hz, 1H),<br />
8.84 (d of d, J = 1.65, 6.3 Hz, 1H), 7.86 (s, 1H), 7.82 (m, 2H), 7.33 (m, 3H), 4.82 (s,<br />
2H). 3.17 (m, 2H), 1.10 (m, 12H), 0.83 (t, J = 6.72 Hz, 3H). 13 C NMR (75.5 MHz,<br />
CDCl3): δ = 167.4, 164.1, 160.8, 154.5, 134.5 (×2), 129.5 (d), 115.3 (d), 111.2, 90.2,<br />
62.5, 40.6, 31.0, 28.2 (×2), 27.3, 25.8, 21.9, 13.8.
2-(3,4-Dichlorophenyl)-2-hydroxy-1-octyl-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-177)<br />
N<br />
Br<br />
N<br />
N C 8H 17<br />
OH<br />
Cl<br />
Cl<br />
Yield: 82 %. 1 H NMR (300 MHz, CDCl3): δ = 9.05 (d of d, J = 1.86, 4.62 Hz, 1H),<br />
8.88 (d of d, J = 1.74, 6.27 Hz, 1H), 8.07 (s, 1H), 8.02 (s, 1H), 7.78 (s, 2H), 7.33 (m,<br />
1H), 4.83 (m, 2H). 3.23 (m, 2H), 1.11 (m, 12H), 0.83 (t, J = 6.75 Hz, 3H). 13 C NMR<br />
(75.5 MHz, CDCl3): δ = 167.4, 154.6, 148.0, 139.4, 132.1, 131.2, 130.4, 129.4, 127.3,<br />
111.3, 89.6, 62.3, 40.6, 31.0, 28.2 (×2), 27.2, 25.7, 21.9, 13.8.<br />
2-(3-Bromophenyl)-2-hydroxy-1-octyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-<br />
4-ium bromide (BS-178)<br />
N<br />
Br<br />
N<br />
N C 8H 17<br />
OH<br />
Br<br />
Yield: 53 %. 1 H NMR (300 MHz, CDCl3): δ = 9.04 (d of d, J = 1.86, 4.68 Hz, 1H),<br />
8.87 (d of d, J = 1.62, 6.27 Hz, 1H), 8.01 (s, 1H), 7.93 (s, 1H), 7.77 (d, J = 7.86 Hz,<br />
1H), 7.66 (d, J = 8.4 Hz, 1H), 7.46 (t, J = 7.92 Hz, 1H) 7.33 (m, 1H), 4.82 (m, 2H).<br />
3.22 (m, 2H), 1.36 (m, 2H), 1.11 (m, 10H), 0.83 (t, J = 6.72 Hz, 3H). 13 C NMR (75.5<br />
MHz, CDCl3): δ = 167.4, 154.6, 148.1, 140.9, 132.1, 130.4, 129.9, 126.0, 121.7,<br />
111.2, 89.8, 62.5, 40.6, 31.0, 28.2 (×2), 27.2, 25.7, 21.9, 13.8.<br />
2-Hydroxy-2-(naphthalen-1-yl)-1-octyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-<br />
4-ium bromide (BS-179)
N<br />
Br<br />
N<br />
N C 8H 17<br />
OH<br />
Yield: 82 %. 1 H NMR (300 MHz, CDCl3): δ = 9.08 (d, J = 4.11 Hz, 1H), 9.00 (d, J =<br />
5.25 Hz, 1H), 8.38 (s, 1H), 8.02 (m, 4H), 7.86 (d, J = 7. 61 Hz, 1H), 7.60 (m, 2H),<br />
7.38 (t, J = 5.64 Hz, 1H), 4.99 (s, 2H). 3.26 (m, 2H), 1.39 (m, 2H), 1.00 (m, 10H),<br />
0.76 (t, J = 6.6 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ = 167.4, 154.7, 148.3,<br />
135.4, 132.9, 132.1, 128.4, 128.1, 127.5, 127.0, 126.6 (×2), 124.2, 111.2, 90.8, 62.5,<br />
40.7, 30.9, 28.2 (×2), 27.3, 25.8, 21.9, 13.8.<br />
2-Hydroxy-2-(4-nitrophenyl)-1-octyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-4ium<br />
bromide (BS-180)<br />
N<br />
Br<br />
N<br />
N C 8H 17<br />
OH<br />
NO 2<br />
Yield: 75 %. 1 H NMR (300 MHz, CDCl3): δ = 9.06 (m, 1H), 8.89 (m, 1H), 8.37 (d, J<br />
= 8.7 Hz, 2H), 8.12 (s, 1H), 8.05 (d, J = 8.76 Hz, 2H), 7.36 (m, 1H), 4.86 (m, 2H).<br />
3.22 (m, 2H), 1.39 (m, 2H), 1.09 (m 10H), 0.81 (t, J = 6.66 Hz, 3H). 13 C NMR (75.5<br />
MHz, CDCl3): δ = 167.5, 154.7, 148.2, 147.9, 145.2, 128.7 (×2), 123.0 (×2), 111.4,<br />
90.0, 62.3, 40.8, 30.9, 28.2 (×2), 27.2, 25.7, 21.9, 13.8.<br />
2-Hydroxy-2-(4’-nitrobiphenyl-4-yl)-1-octyl-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-185)
N<br />
Br<br />
N<br />
N C 8H 17<br />
OH<br />
NO 2<br />
Yield: 49 %. 1 H NMR (300 MHz, CDCl3): δ = 9.05 (d, J = 4.11 Hz, 1H), 8.88 (d, J =<br />
6.2 Hz, 1H), 8.32 (d, J = 8.7 Hz, 2H), 8.03 (d, J = 8.76 Hz, 2H), 7.94 (m, 5H), 7.34 (t,<br />
J = 4.98 Hz, 1H), 4.87 (s, 2H). 3.24 (m, 2H), 1.43 (m, 2H), 1.10 (m 10H), 0.76 (t, J =<br />
6.45 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ = 167.5, 154.6, 148.2, 146.9, 145.5,<br />
138.9, 138.4, 127.9 (×3), 127.2 (×2), 124.1 (×3), 111.2, 90.5, 62.6, 40.8, 31.0, 28.2<br />
(×2), 27.3, 25.8, 21.9, 13.8.<br />
2-Hydroxy-2-(4-(methylsulfonyl)phenyl)-1-octyl-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-186)<br />
N<br />
Br<br />
N<br />
N C 8H 17<br />
OH<br />
SO 2Me<br />
Yield: 48 %. 1 H NMR (300 MHz, CDCl3): δ = 9.06 (d of d J = 1.65, 4.47 Hz, 1H),<br />
8.94 (d of d, J = 1.56, 6.21 Hz, 1H), 8.08 (s, 1H), 8.05 (s, 4H), 7.36 (m, 1H), 4.87 (m,<br />
2H). 3.27 (s, 3H), 3.24 (m, 2H), 1.40 (m, 2H), 1.11 (m, 10H), 0.82 (t, J = 6.66 Hz,<br />
3H). 13 C NMR (75.5 MHz, CDCl3): δ = 167.4, 154.7, 148.2, 143.7 (×2), 141.6, 128.1<br />
(×2), 127.0, 111.4, 90.3, 62.5, 43.3, 40.9, 31.0, 28.2 (×2), 27.4, 25.9, 21.9, 13.8.<br />
2-Hydroxy-2-(4-(methylthio)phenyl)-1-octyl-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-187)
N<br />
Br<br />
N<br />
N C 8H 17<br />
OH<br />
SMe<br />
Yield: 49 %. 1 H NMR (300 MHz, CDCl3): δ = 9.02 (m, 1H), 8.85 (m, 1H), 7.78 (s,<br />
1H), 7.66 (d, J = 8.52 Hz, 2H), 7.33 (m, 3H), 4.79 (m, 2H). 3.33 (s, 3H), 3.22 (m,<br />
2H), 1.39 (m, 2H), 1.10 (m, 10H), 0.83 (t, J = 6.66 Hz, 3H). 13 C NMR (75.5 MHz,<br />
CDCl3): δ = 167.4, 154.7, 148.2, 143.7 (×2), 141.6, 128.1 (×2), 127.0, 111.4, 90.3,<br />
62.5, 43.3, 40.9, 31.0, 28.2 (×2), 27.4, 25.9, 21.9, 13.8.<br />
5-(2,4-Dimethoxyphenyl)-N-methy-1H-imidazol-2-amine (BS-136)<br />
HN<br />
N<br />
N<br />
H<br />
O<br />
O<br />
Yield : 48 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.63 (br, 1H), 7.43 (d, J = 3.0<br />
Hz, 1H), 7.07 (s, 1H), 6.90 (d, J = 8.8 Hz, 1H), 6.63 (d of d, J = 3.1, 3.1 Hz, 1H), 5.73<br />
(q, J = 5.1 Hz, 1H), 3.80 (s, 3H). 3.71 (s, 3H), 2.77 (d, J= 5.1 Hz, 3H). 13 C NMR<br />
(75.5 MHz, DMSO-d6): δ =153.1, 151.0, 149.5, 129.3, 123.4, 114.8, 111.8, 111.2,<br />
110.1, 55.5, 55.2, 29.8. HRMS (EI) C12H15N3O2, calcd 233.1164, found : 233.1173.<br />
N-((Benzol[d][1,3]dioxol-6-yl)-5-(naphthalene-3-yl)-1H-imidazol-2-amine (BS-<br />
137)<br />
O<br />
O<br />
HN<br />
N<br />
N<br />
H<br />
Yield : 72 %. 1 H NMR (300 MHz, DMSO-d6) δ = 10.61 (br, 1H), 8.06 (s, 1H), 7.83-<br />
7.79 (m, 4H), 7.44-7.37 (m, 2H), 7.19 (s, 1H), 6.99 (s, 1H), 6.87-6.86 (m, 2H), 6.32 (t,<br />
J = 6.4 Hz, 1H), 5.96 (s, 2H), 4.34 (d, J = 6.4 Hz, 2H). 13 C NMR (75.5 MHz,<br />
DMSO-d6) δ =151.2, 147.0, 145.8, 134.6, 133.5, 131.3, 127.5 (x 2), 127.4, 127.3,<br />
126.0,125.6, 124.6, 123.2, 120.4, 108.0 (x 2),107.8, 100.6 (x 2), 46.1. HRMS EI<br />
C21H17N3O2, calcd 343.1321 , found : 343.1340.<br />
5-(3,4-Dichlorophenyl)-N-propyl-1H-imidazol-2-amine(BS-140)
C3H7 HN<br />
N<br />
N<br />
H<br />
Cl<br />
Cl<br />
Yield : 70 %. 1 H NMR (300 MHz, DMSO-d6) δ = 10.55 (br, 1H), 7.82 (s, 1H), 7.58<br />
(s, 1H), 7.50 (d, J = 8.2 Hz, 1H), 7.22 (s, 1H), 5.83 (t, J = 6.0 Hz, 1H), 3.10 (q, J = 8.2<br />
Hz, 2H), 1.54 (m, 2H), 0.90 (t, J = 7.35 Hz, 3H). 13 C NMR (75.5 MHz, DMSO-d6) δ<br />
=151.6, 130.9 (x 2), 130.3 (x 2), 126.3, 124.6, 123.4, 104.2, 44.7, 22.6, 11.4. HRMS<br />
EI C12H13Cl2N3, calcd 269.0487, found : 269.0480.<br />
N-Cyclohexyl-5-(4-(methylsulfonyl)phenyl)-1H-imidazol-2-amine (BS-141)<br />
HN<br />
N<br />
N<br />
H<br />
S O<br />
O<br />
Yield : 43 %. 1 H NMR (300 MHz, DMSO-d6) δ = 10.54 (br, 1H), 7.83-7.76 (m, 4H),<br />
7.31 (s, 1H), 5.75 (d, J = 8.4 Hz, 1H), 3.16 (s, 3H), 2.49 (s, 1H), 1.90 (s, 2H), 1.70 (m,<br />
2H), 1.20 (m, 6H). 13 C NMR (75.5 MHz, DMSO-d6) δ =151.1, 140.1, 136.1, 127.2(x<br />
4), 123.4 (x 2), 104.2, 51.1, 43.7, 33.0(x 2), 25.4, 24.6(x 2). HRMS EI C16H21N3O2S,<br />
calcd 319.1354. , found : 319.1337.<br />
5-(4-Chlorophenyl)-N-octyl-1H-imidazol-2-amine (BS-143)<br />
C8H17 HN<br />
N<br />
N<br />
H<br />
Cl<br />
Yield : 43%. 1 H NMR (300 MHz, DMSO-d6) δ = 10.43 (br, 1H), 7.63 (d, J = 8.3 Hz,<br />
2H), 7.31 (d, J = 8.4 Hz, 2H), 7.09 (s, 1H), 5.71 (t, J = 4.9 Hz, 1H), 3.12 (m, 2H),<br />
1.48-1.51 (m, 2H), 1.25 (m, 10H), 0.85 (t, J = 4.2 Hz, 3H). 13 C NMR (75.5 MHz,<br />
DMSO-d6) δ =151.5, 128.8 (x 2), 128.1 (x 3), 124.9 (x 2), 100.7, 42.9, 31.2, 29.4,<br />
28.8, 28.7, 26.4, 22.0, 13.9. HRMS EI C17H24ClN3, calcd 305.1659, found : 305.1646.<br />
5-(4-Chlorophenyl)-N-pentyl-1H-imidazol-2-amine (BS-146)<br />
C5H11 HN<br />
N<br />
N<br />
H<br />
Cl
Yield: 57 %. 1 H NMR (300 MHz, DMSO-d6) δ = 10.44 (br, 1H), 7.65 (d, J = 7.3 Hz,<br />
2H), 7.31 (d, J = 8.3 Hz, 2H), 7.09 (s, 1H), 5.71 (t, J = 5.1 Hz, 1H), 3.12 (m, 2H),<br />
1.51 (t, J = 1.7 Hz, 2H), 1.30 (m, 4H), 0.88 (t, J = 6.7 Hz, 3H). 13 C NMR (75.5 MHz,<br />
DMSO-d6) δ =151.5, 128.9 (x 2), 128.1 (x 3), 124.9 (x 2), 104.1, 42.8, 29.1, 28.6,<br />
21.9, 13.9.HRMS EI C14H18ClN3, calcd 263.1189. , found: 263.1180.<br />
5-(4-Fluorophenyl)-N-hexyl-1H-imidazol-2-amine (BS-147)<br />
C6H13 HN<br />
N<br />
N<br />
H<br />
F<br />
Yield: 61 %. 1 H NMR (300 MHz, DMSO-d6) δ = 10.38 (br, 1H), 7.62 (m, 2H), 7.09<br />
(t, J = 8.8 Hz, 2H), 6.99 (s, 1H), 5.66 (m, 1H), 3.13-3.10 (m, 2H), 1.51 (m, 2H), 1.28<br />
(m, 6H), 0.87 (t, J = 6.4 Hz, 3H). 13 C NMR (75.5 MHz, DMSO-d6) δ =161.6, 158.5,<br />
151.4, 125.0, 124.9, 115.0, 114.7, 104.1 (x 2), 42.9, 31.0, 29.4, 26.1, 22.1, 13.8.,<br />
HRMS EI C15H20FN3, calcd 261.1641. , found: 261.1631.<br />
N-(4-Methoxyphenethyl)-5-(3-bromophenyl)-1H-imidazol-2-amine(BS-148)<br />
O<br />
HN<br />
N<br />
N<br />
H<br />
Br<br />
Yield : 44 %. 1 H NMR (300 MHz, DMSO-d6) δ = 10.56 (br, 1H), 7.82 (s, 1H), 7.65<br />
(d, J = 6.5 Hz, 2H), 7.24-7.16 (m, 5H), 6.88 (d, J = 8.4 Hz, 2H), 5.77 (m, 1H), 3.72 (s,<br />
3H), 3.35 (s, 2H), 2.77 (t, J = 7.6 Hz, 2H). 13 C NMR (75.5 MHz, DMSO-d6) δ<br />
=157.5, 151.3, 131.6 (x 2), 130.3, 129.6 (x 3), 127.3, 125.7, 122.1, 121.9, 113.6 (x 3),<br />
54.9, 44.8, 34.6.,HRMS EI C18H18BrN3O, calcd 371.0633. , found : 371.0658.<br />
N-Cyclooctyl-5-(4-(methylsulfonyl)phenyl)-1H-imidazol-2-amine (BS-154)<br />
HN<br />
N<br />
N<br />
H<br />
SO 2Me<br />
Yield : 53 %. 1 H NMR (300 MHz, DMSO-d6) δ = 10.49 (br, 1H), 7.86 (d, J = 8.5 Hz,<br />
2H), 7.79 (d, J = 8.5 Hz, 2H), 7.31 (d, J = 1.5 Hz, 1H), 5.74 (d, J = 8.4 Hz, 1H), 3.64
(s, 1H), 3.16 (s, 3H), 1.80 (m, 2H), 1.53 (m, 12H). 13 C NMR (75.5 MHz, CDCl3) δ =<br />
151.5, 138.8, 136.2, 127.7 (x 3), 124.0 (x 2), 105.1, 53.7, 44.6, 32.3 (x 2), 27.2 (x 2),<br />
25.2, 23.4 ( x 2). HRMS EI C18H25N3O2S, calcd 344.1667. , found : 344.1644.<br />
4-(2-(2-Methoxyethylamino)-1H-imidazole-5-yl)benzonitrile(BS-139)<br />
O<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
Yield 85 %. 1 H NMR (300 MHz, DMSO d6) δ = 10.6 (br, 1H), 7.7 (m 4H), 7.3 (s 1H),<br />
5.8 (s 1H), 3.5 (t 2H), 3.4 (m 2H), 3.2 (s 3H). 13 C NMR (300 MHz, DMSO d6) δ<br />
=151.3, 140.1, 134.2, 132.2(x 2), 123.8, 119.5, 110.8, 106.4, 104.1, 70.9, 57.9, 54.8,<br />
43.3. HRMS EI C13H14N4O, calcd 242.1168 , found : 242.1167.<br />
5-(4-Methoxyphenyl)-N-octyl-1H-imidazol-2-amine (BS-258 )<br />
C 8H 17<br />
N<br />
H<br />
N<br />
N<br />
H<br />
O<br />
Yield : 78 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.91 (br s, 1H), 7.51 (d, J = 8.57<br />
Hz, 2H), 6.95 (s, 1H), 6.87 (d, J = 8.75 Hz, 2H), 6.05 (m, 1H), 3.74 (s, 3H), 3.16 (m,<br />
2H), 1.51 (m, 2H), 1.28 (m, 10H), 0.85 (t, J = 6.75 Hz, 3H). 13 C NMR (75.5 MHz,<br />
CDCl3): δ =149.2, 131.1, 129.5, 129.3 (×2), 128.8 (×2), 128.2, 123.4, 43.1, 31.6, 29.5,<br />
29.0, 28.9, 26.4, 22.2, 14.0. HRMS (EI): C18H27N3O, calcd 301.2154, found:<br />
301.2142.<br />
5-(4-Fluorophenyl)-N-octyl-1H-imidazol-2-amine (BS-259)<br />
C 8H 17<br />
N<br />
H<br />
N<br />
N<br />
H<br />
F<br />
Yield : 69% . 1 H NMR (300 MHz, DMSO-d6): δ = 10.44 (br s, 1H), 7.61 (t, J = 5.85<br />
Hz, 2H), 7.08 (t, J = 8.78 Hz, 2H), 6.99 (s, 1H), 5.67 (t, J = 6.03 Hz, 1H), 3.10 (m,<br />
2H), 1.51 (m, 2H), 1.25 (m, 10H), 0.83 (m, 3H). 13 C NMR (75.5 MHz, CDCl3): δ<br />
=163.8, 160.5, 148.7, 130.2, 128.4, 127.0, 122.9, 115.5, 104.7, 43.0, 31.6, 29.5, 29.0,<br />
28.9, 26.4, 22.5, 14.0. HRMS (EI): C17H24FN3, calcd 289.1954, found:. 289.1964.<br />
5-(3,4-Dichlorophenyl)-N-octyl-1H-imidazol-2-amine (BS-260)<br />
C 8H 17<br />
N<br />
H<br />
N<br />
N<br />
H<br />
Cl<br />
Cl
Yield : 72 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.52 (br s, 1H), 7.82 (s, 1H),<br />
7.58 (m, 1H), 7.50 (d, J = 8.13 Hz, 1H), 7.22 (s, 1H), 5.78 (m, 1H), 3.11 (m, 2H), 1.51<br />
(m, 2H), 1.28 (m, 10H), 0.85 (t, J = 6.94 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ<br />
=149.6, 132.8, 131.1, 131.0, 130.6, 129.5, 127.1, 127.0, 124.2, 43.3, 31.6, 29.5, 29.0,<br />
28.9, 26.4, 22.5, 14.0. HRMS (EI): C17H23Cl2N3, calcd 339.1269, found:. 339.1279.<br />
5-(3-Bromophenyl)-N-octyl-1H-imidazol-2-amine (BS-261)<br />
C 8H 17<br />
N<br />
H<br />
N<br />
N<br />
H<br />
Br<br />
Yield : 79 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.49 (br s, 1H), 7.79 (s, 1H),<br />
7.59 (s, 1H), 7.22 (m, 1H), 7.14 (s, 1H), 5.73 (t, J = 5.66 Hz, 1H), 3.11 (m, 2H), 1.51<br />
(m, 2H), 1.25 (m, 10H), 0.84 (t, J = 6.69 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ<br />
=149.2, 133.0, 130.8, 130.1 (×2), 128.0, 126.5, 123.8, 122.6, 43.2, 31.6, 29.5, 29.0,<br />
28.9, 26.4, 22.5, 14.0. HRMS (EI): C17H24BrN3, calcd 349.1154, found:. 249.1138.<br />
5-(Naphthalen-1-yl)-N-octyl-1H-imidazol-2-amine (BS-262)<br />
C 8H 17<br />
N<br />
H<br />
N<br />
N<br />
H<br />
Yield : 68 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.53 (br s, 1H), 8.05 (s, 1H),<br />
7.80 (m, 3H), 7.39 (m, 3H), 7.17 (s, 1H), 5.73 (m, 1H), 3.16 (m, 2H), 1.54 (m, 2H),<br />
1.26 (m, 10H), 0.83 (t, J = 6.86 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =149.1,<br />
133.4, 132.4, 129.5, 128.3, 128.2, 127.9, 127.7, 126.6, 126.4 (×2), 126.0, 123.0, 43.3,<br />
31.6, 29.5, 29.0, 28.9, 26.4, 22.5, 14.0. HRMS (EI): C21H27N3, calcd 321.4592,<br />
found:. 321.4578.<br />
5-(4-Nitrophenyl)-N-octyl-1H-imidazol-2-amine (BS-263)<br />
C 8H 17<br />
N<br />
H<br />
N<br />
N<br />
H<br />
NO 2<br />
Yield : 66 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.74 (br s, 1H), 8.12 (d, J = 8.92<br />
Hz, 2H), 7.84 (d, J = 8.92 Hz, 2H), 7.43 (s.1H), 5.91 (t, J = 5.54 Hz, 1H), 3.16 (m,<br />
2H), 1.52 (m, 2H), 1.25 (m, 10H), 0.85 (t, J = 6.75 Hz, 3H). 13 C NMR (75.5 MHz,<br />
CDCl3): δ =163.8, 160.5, 148.7, 130.2, 128.4, 127.0, 122.9, 115.5, 104.7, 43.0, 31.6,<br />
29.5, 29.0, 28.9, 26.4, 22.5, 14.0. HRMS (EI): C17H24N4O2, calcd 316.1899,<br />
found:.316.1909.
5-(4’-Nitrobiphenyl-4-yl)-N-octyl-1H-imidazol-2-amine (BS-264)<br />
C 8H 17<br />
N<br />
H<br />
N<br />
N<br />
H<br />
NO 2<br />
Yield : 75 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.53 (br s, 1H), 8.27 (d, J = 8.71<br />
Hz, 2H), 7.96 (d, J = 8.71 Hz, 2H), 7.75 (s.4H), 7.18 (s. 1H), 5.76 (t, J = 5.88 Hz,<br />
1H), 3.16 (m, 2H), 1.53 (m, 2H), 1.26 (m, 10H), 0.86 (t, J = 6.75 Hz, 3H). 13 C NMR<br />
(75.5 MHz, CDCl3): δ =163.8, 160.5, 148.7, 130.2, 128.4, 127.0, 122.9, 115.5, 104.7,<br />
43.0, 31.6, 29.5, 29.0, 28.9, 26.4, 22.5, 14.0. HRMS (EI): C23H28N4O2, calcd<br />
392.2212, found:.392.2201.<br />
5-(4-(Methylsulfonyl)phenyl)-N-octyl-1H-imidazol-2-amine (BS-265)<br />
C 8H 17<br />
N<br />
H<br />
N<br />
N<br />
H<br />
O<br />
S<br />
O<br />
Yield : 54 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.62 (br s, 1H), 7.84 (d, J = 8.55<br />
Hz, 2H), 7.76 (d, J = 8.35 Hz, 2H), 7.32 (s.1H), 5.83 (t, J = 5.97 Hz, 1H), 3.16 (m,<br />
5H), 1.52 (m, 2H), 1.25 (m, 10H), 0.85 (t, J = 6. 56 Hz, 3H). 13 C NMR (75.5 MHz,<br />
CDCl3): δ =150.7, 138.1, 136.6, 127.9 (×2), 127.6, 127.4 (×2), 126.0, 44.5, 43.6, 31.6,<br />
29.6, 29.0, 28.9, 26.5, 22.5, 14.0. HRMS (EI): C18H27N3O2S, calcd 349.4909,<br />
found:.249.4918.<br />
N-Isobutyl-5-(4-nitrophenyl)-1H-imidazol-2-amine (BS-292)<br />
N<br />
H<br />
N<br />
N<br />
H<br />
NO 2<br />
Yield : 70 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.69 (br s, 1H), 8.12 (d, J = 9.02<br />
Hz, 2H), 7.84 (d, J = 8.50 Hz, 2H), 7.42 (s, 1H), 5.99 (t, J = 5.93 Hz, 1H), 2.99 (t, J =<br />
6.44 Hz, 2H), 1.83 (m, 1H), 0.89 (d, J = 6.70 Hz, 6H). 13 C NMR (75.5 MHz, DMSOd6):<br />
δ =152.2 (×2), 143.8, 141.6, 123.9 (×2), 123.3, 104.1 (×2), 50.4, 27.9, 20.1 (×2).<br />
HRMS (EI): C13H16N4O2, calcd 260.1273, found: 260.1287<br />
N-Isobutyl-5-phenyl-1H-imidazol-2-amine (BS-293)<br />
N<br />
H<br />
N<br />
N<br />
H
Yield : 71 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.52 (br s, 1H), 7.59 (d, J = 7.47<br />
Hz, 2H), 7.28 (t, J = 7.47 Hz, 2H), 7.09 (t, J = 7.25 Hz,1H), 7.04 (s,1H), 5.92 (t, J =<br />
5.71 Hz, 1H), 2.98 (t, J = 6.37 Hz, 2H), 1.82 (m, 1H), 0.89 (d, J = 6.59 Hz, 6H). 13 C<br />
NMR (75.5 MHz, DMSO-d6): δ =151.2, 134.0, 133.1, 128.2 (×2), 125.1, 123.4(×2),<br />
104.1, 50.5, 27.9, 20.1 (×2). HRMS (EI): C13H17N3, calcd 215.1422, found:215.1411.<br />
5-(4-Bromophenyl)-N-isobutyl-1H-imidazol-2-amine (BS-294)<br />
N<br />
H<br />
N<br />
N<br />
H<br />
Br<br />
Yield : 69 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.46 (br s, 1H), 7.55 (d, J = 8.25<br />
Hz, 2H), 7.42 (d, J = 8.25 Hz, 2H), 7.08 (s, 1H), 5.80 (t, J = 5.75 Hz, 1H), 2.97 (t, J =<br />
6.25 Hz, 2H), 1.82 (m, 1H), 0.89 (d, J = 6.50 Hz, 6H). 13 C NMR (75.5 MHz, DMSOd6):<br />
δ =151.6, 134.1, 133.0 (×3), 125.3 (×2), 117.2, 104.1, 50.6, 27.9, 20.1 (×2).<br />
HRMS (EI): C13H16BrN3, calcd 293.0528, found:293.0529.<br />
5-(4-Chlorophenyl)-N-isobutyl-1H-imidazol-2-amine (BS-295)<br />
N<br />
H<br />
N<br />
N<br />
H<br />
Cl<br />
Yield : 73 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.46 (br s, 1H), 7.60 (d, J = 8.35<br />
Hz, 2H), 7.29 (d, J = 8.35 Hz, 2H), 7.07 (s, 1H), 5.81 (t, J = 5.96 Hz, 1H), 2.97 (t, J =<br />
6.20 Hz, 2H), 1.82 (m, 1H), 0.89 (d, J = 6.68 Hz, 6H). 13 C NMR (75.5 MHz, DMSOd6):<br />
δ =151.5, 133.6, 133.2, 128.9, 128.0 (×2), 124.9 (×2), 104.1, 50.5, 27.9, 20.1<br />
(×2). HRMS (EI): C13H16ClN3, calcd 249.1033, found:249.1047.
2.11 Representative NMR spectra<br />
2.11.1 1 H and 13 C NMR spectra of bs-026<br />
Integral<br />
9.5<br />
9.0<br />
170<br />
8.5<br />
8.2747<br />
8.2590<br />
1.8547<br />
162.5113<br />
157.9984<br />
160<br />
8.0<br />
150<br />
7.5<br />
7.2629<br />
140<br />
7.0<br />
6.5166<br />
6.5003<br />
6.4846<br />
0.9485<br />
6.5<br />
N<br />
130<br />
6.0<br />
N<br />
5.5<br />
5.0793<br />
N<br />
C7H15 N<br />
H<br />
110.1675<br />
N<br />
C7H15 N<br />
H<br />
120<br />
110<br />
0.8893<br />
5.0 4.5<br />
(ppm)<br />
100<br />
3.4260<br />
3.4028<br />
3.3834<br />
3.3790<br />
3.3595<br />
4.0<br />
77.5117<br />
77.0862<br />
76.6644<br />
90 80<br />
(ppm)<br />
1.9702<br />
3.5<br />
70<br />
3.0<br />
60<br />
2.5<br />
2.0<br />
50<br />
1.6316<br />
1.6102<br />
1.5870<br />
1.3698<br />
1.3522<br />
1.3403<br />
1.3058<br />
1.2876<br />
0.9035<br />
0.8959<br />
0.8815<br />
0.8583<br />
0.0003<br />
2.6079<br />
1.5<br />
41.5103<br />
40<br />
8.3061<br />
1.0<br />
3.0000<br />
0.5<br />
31.8118<br />
29.6081<br />
29.0662<br />
26.9680<br />
22.6114<br />
30<br />
20<br />
0.0<br />
14.0875<br />
10<br />
0
2.11.2 1 H and 13 C NMR spectra of bs-091<br />
Integral<br />
170<br />
167.5253<br />
9.5<br />
9.0476<br />
9.0376<br />
8.8882<br />
8.8687<br />
0.9779<br />
0.9465<br />
160<br />
9.0<br />
154.6121<br />
8.5<br />
148.2155<br />
150<br />
7.8977<br />
7.8105<br />
7.7816<br />
7.5826<br />
7.5544<br />
7.3454<br />
7.3284<br />
7.3084<br />
0.9515<br />
1.9910<br />
1.9242<br />
0.9636<br />
8.0<br />
140<br />
7.5<br />
137.3205<br />
134.1059<br />
129.0584<br />
128.3529<br />
N<br />
Br<br />
7.0<br />
N<br />
Br<br />
130<br />
N<br />
120<br />
N<br />
6.5<br />
N C 10H 21<br />
OH<br />
111.2795<br />
6.0<br />
Cl<br />
N C 10H 21<br />
OH<br />
110<br />
Cl<br />
100<br />
5.5<br />
4.8203<br />
1.9070<br />
5.0 4.5<br />
(ppm)<br />
90.2424<br />
90 80<br />
(ppm)<br />
4.0<br />
70<br />
3.5<br />
62.5177<br />
3.3309<br />
3.2179<br />
3.1959<br />
3.1689<br />
3.1520<br />
60<br />
1.7611<br />
3.0<br />
50<br />
2.5024<br />
2.5<br />
40.7023<br />
40<br />
2.0<br />
1.5<br />
1.2025<br />
1.0976<br />
0.8748<br />
0.8535<br />
0.8309<br />
16.214<br />
1.0<br />
31.2220<br />
28.6219<br />
28.2364<br />
27.2800<br />
25.8145<br />
22.0544<br />
30<br />
20<br />
3.0000<br />
13.9231<br />
0.5<br />
10<br />
0.0<br />
0
2.11.3<br />
10.4329<br />
0.7429<br />
151.5720<br />
10.0<br />
150<br />
1 H and 13 C NMR spectra of bs-143<br />
C8H17 HN<br />
C8H17 HN<br />
140<br />
9.0<br />
N<br />
N<br />
H<br />
128.8948<br />
128.1056<br />
124.9601<br />
N<br />
N<br />
H<br />
130<br />
8.0<br />
120<br />
7.6549<br />
7.6273<br />
7.3122<br />
7.2845<br />
7.0969<br />
1.7133<br />
2.0012<br />
0.7988<br />
110<br />
7.0<br />
Cl<br />
100.7882<br />
Cl<br />
100<br />
6.0<br />
90<br />
5.7173<br />
1.3479<br />
5.0<br />
(ppm)<br />
80<br />
(ppm)<br />
70<br />
4.0<br />
60<br />
3.1288<br />
3.1068<br />
50<br />
2.0669<br />
3.0<br />
42.9279<br />
40<br />
2.5024<br />
2.0863<br />
2.0<br />
1.5113<br />
1.4893<br />
1.2584<br />
1.9883<br />
10.174<br />
31.2511<br />
29.4365<br />
28.8183<br />
28.7164<br />
26.4691<br />
22.0835<br />
30<br />
20<br />
1.0<br />
0.8579<br />
0.8353<br />
3.0000<br />
13.9304<br />
10<br />
-0.0001<br />
0.0<br />
0
2.12 References<br />
[1] Cafieri F, Fattorusso E, Mangoni A, Taglialatela Scafati O. (1996) Tetrahedron Lett. 3, 3587-<br />
3590.<br />
[2] Kobayashi J, Ohizumi Y, Nakamura H, Hirata Y, (1986) Tetrahedron 42, 1176-1177.<br />
[3] (a) Bedoya Zurita M, Ahond A, Poupat C, Potier P (1989) Tetrahedron. 45, 6713-6720. (b)<br />
Gross H, Kehraus S, Koenig GM, Woerheide G, Wright AD. (2002) J. Nat. Prod. 65, 1190-<br />
1193 (c) Hassan W, Edrada R, Ebel R, Wray V, Berg A, Van Soest R, Wiryowidagdo S,<br />
Proksch P. (2004) J. Nat. Prod. 67, 817-822.<br />
[4] (a) Copp BR, Fairchild CR, Cornell L, Casazza AM, Robinson S, Ireland CM. (1998) J. Med.<br />
Chem. 41, 3909-3911. (b) Colson G, Raboult L, Lavelle F, Zeaial A. (1992) Biochem.<br />
Pharmacol. 43, 1717-1723. (c) Pitts WJ, Wityak J, Smallheer JM, Tobin AE, Jetter JW,<br />
Buynitsky JS, Harlow PP, Solomon KA, Corjay MH, Mousa SA, Wexler R, Jadhav PK.<br />
(2000) J. Med. Chem. 43, 27-40. (d) Batt DG, Petraitis JJ, Houghton GC, Modi DP, Cain GA,<br />
Corjay MH, Mousa SA, Bouchard PJ, Forsythe MS, Harlow PP, Barbera FA, Spitz SM,<br />
Wexler RR, Jadhav. (2000) J. Med. Chem. 43, 41-58.<br />
[5] (a) Little TL, Webber SE. (1994) J. Org. Chem. 59, 7299-7305. (b) Abou Jneid R, Ghoulami<br />
S, Martin MT, Dau ETH, Travert N, Al-Mourabit A. (2004) Org. Lett. 6, 3933-3936. (c) Gore<br />
VK, Ma VV, Norman MH, Ognyanov VI, Xi N. (2006) US Patent, US 2006/0084640<br />
[6] Stamford AW, Craig CD, Huang Y. (2001) Int. Pat. WO 01/44201<br />
[7] (a) Lamattina JL, Mularski CJ (1984)Tetrahedron Lett. 25, 2957-2960 (b) Lamattina JL.<br />
(1985) Eur. Pat. Appl. EP 138464 A2.<br />
[8] Katritzky AR, Rogovoy B (2005) Arkivoc. Part Iv, 49-87 and references herein.<br />
[9] Beyer H, Pyl T, Lahmer H. (1961) Chem. Ber. 94, 3217.<br />
[10] Thangavel N, Murgesh K. (2005) Asian J. Chem. 17, 2769.<br />
[11] Ermolat’ev DS, Giménez V N, Babaev EV, Van der Eycken E. (2006) J. Comb. Chem. 8, 659-<br />
663.<br />
[12] Ermolat’ev DS, Svidritsky EP, Babaev EV, Van der Eycken E. (2009) Tetrahedron Lett. 50,<br />
5218-5220.<br />
[13] Ermolat’ev D. S., Savaliya B, Shah A, Van der Eycken E, (2010) Molecular Diversity.<br />
accepted.<br />
[14] Ashry EI, Kilany Y, Rashed N, Assafi H. (1999) Adv. Heterocycl. Chem. 75, 79;<br />
[15] Brown D. J. “Mechanisms of Molecular Migrations”, Vol. 1, Thyagarajan, B. S. (1968) (Ed.),<br />
Wiley-Interscience, New York, pp. 209.<br />
[16] Ermolat’ev, D. S. and Van der Eycken, E. (2008) J. Org. Chem. 73, 6691.<br />
[17] Costerton, J. W, Stewart P. S, Greenberg,E. P. (1999) Science 284, 1318-22.<br />
[18] Stewart P. S, Costerton J. W. (2001) Lancet. 358, 135-8.<br />
[19] Donlan R. M, Costerton J. W. (2002) Clin Microbiol Rev. 15, 167-93.<br />
[20] Mah T. F, Pitts B, Walker G. C, Stewart P. S, O'Toole G. A. (2003) Nature 426, 306-10.
[21] Matz C, McDougald D, Moreno A. M, Yung P. Y, Yildiz F. H, Kjelleberg S. B. (2005) Proc<br />
Nat. Acad. Sci. USA. 102, 16819-24.<br />
[22] Davies D. U. (2003) Nat Rev Drug Discov. 2, 114-22.<br />
[23] Olson M. E, Ceri H, Morck D. W, Read R. R. (2002) J. Vet. Res. 66, 86-92.<br />
[24] Blanke S. R, Yang R. (2002) Enviromental Institute of Houston<br />
[25] Musk D. J, Hergenrother P. (2006) J. Curr. Med. Chem. 13, 2163-77.<br />
[26] De Nys R, Kumar N, Kjelleberg S, Steinberg P. D. (2006) Prog Mol Subcell Biol. 42.<br />
[27] Janssens J. C, Steenackers H, Robijns S, Gellens E, Levin J, Zhao H, Hermans K, De Coster<br />
D, Verhoeven T. L, Marchal K, Vanderleyden J, De Vos D. E, De Keersmaecker S. C. (2008)<br />
Appl Environ Microbio. 74, 6639-48.<br />
[28] Geske G. D, Siegel A. P, Blackwell H. E. (2005) J. Am. Chem. Soc. 127, 12762-3.<br />
[29] Huigens R. W, Richards J. J, Parise G, Ballard T. E, Zeng W, Deora R, Melander C. (2007) J.<br />
Am. Chem. Soc. 129, 6966-7.<br />
[30] Richards J. J, Ballard T. E, Melander C. (2008) Org. Biomol. Chem. 6, 1356-63.<br />
[31] Richards J. J, Huigens Iii R. W, Ballard T. E, Basso A, Cavanagh J, Melander C. (2008)<br />
Chem. Commun. (Camb). 1698-700.<br />
[32] Huigens R. W, Ma L, Gambino C, Moeller P. D, Basso A, Cavanagh J, Wozniak D. J,<br />
Melander C. (2008) Mol. Biosyst. 4, 614-21.<br />
[33] Richards J. J, Ballard T. E, Huigens R. W, Melander C. (2008) Chem. bio. chem. 9, 1267-79.<br />
[34] Rogers S. A, Melander C. (2008) Angew. Chem. Int. Ed. 47, 5229-31.<br />
[35] Ballard T. E, Richards J, Wolfe A. L, Melander C. (2008) Chemistry. 14, 10745-61.<br />
[36] Sullivan J. D, Giles R. L. (2009) Current Bioactive Compounds. 5, 39-78.<br />
[37] Prouty A. M, Schwesinger W. H, Gunn J. S. (2002) Infect Immun. 70, 2640-9.<br />
[38] Barak J. D, Charkowski A. O. (2002) Appl. Environ Microbiol. 68, 4758-63.<br />
[39] Brandl M. T, Mandrell R. E. (2002) Appl. Environ Microbiol. 68, 3614-21.<br />
[40] Boddicker J. D, Ledeboer N. A, Jagnow J, Jones B. D, Clegg S. (2002) Mol Microbiol. 45,<br />
1255-65.<br />
[41] Romling U, Sierralta W. D, Eriksson K, Normark S. (1998) Mol Microbiol. 28, 249-64.<br />
[42] Latasa C, Roux A, Toledo-Arana A, Ghigo J. M, Gamazo, C, Penades J. R, Lasa I. (2005)<br />
Mol. Microbiol. 58, 1322-39.<br />
[43] Parry C. M, Threlfall E. J. (2008) Curr. Opin. Infect. Dis. 21, 531-8.<br />
[44] Govan J. R, Deretic V. (1996) Microbiol Rev. 60, 539-74.<br />
[45] Wagner V. E, Iglewski B. H. P. (2008) Clin. Rev. Allergy Immunol. 35, 124-34.<br />
[46] Gomez M. I, Prince A. (2007) Curr. Opin. Pharmacol. 7, 244-51.<br />
[47] Ghannoum M, Abu Elteen K, el-Rayyes N. R. (1989) Microbios. 60, 23-33.<br />
[48] Fioravanti R, Biava M, Porretta G. C, Landolfi C, simonetti N, Villa A, Conte E, Porta-Puglia<br />
(1995) Eur. J. Med. Chem. 30, 123-132.
Structure Activity Relationship of N1-<br />
Substituted 2-Aminoimidazoles as Inhibitors of<br />
Biofilm Formation by Salmonella Typhimurium<br />
and Pseudomonas aeruginosa
Chapter-3<br />
Structure Activity Relationship of N1-Substituted 2-Aminoimidazoles<br />
as Inhibitors of Biofilm Formation by Salmonella Typhimurium and<br />
Pseudomonas aeruginosa<br />
H 2N<br />
N<br />
N<br />
R 1<br />
A library of N1-substituted 4(5)-phenyl-2-aminoimidazoles was synthesized and<br />
tested for the antagonistic effect against biofilm formation by Salmonella<br />
Typhimurium and Pseudomonas aeruginosa. The substitution pattern of the 4(5)-<br />
phenyl group and the nature of the N1-substituent were found to have a major effect<br />
on the biofilm inhibitory activity. The most active compounds of this series were<br />
shown to inhibit the biofilm formation at low micromolar concentrations.<br />
Publication:<br />
[1] Structure Activity Relationship of 4(5)-Phenyl-2-amino-1H-imidazoles, N1-<br />
Substituted 2-Aminoimidazoles and Imidazo[1,2-a]pyrimidinium Salts as<br />
Inhibitors of Biofilm Formation by Salmonella Typhimurium and<br />
Pseudomonas aeruginosa. J. Med.Chem. (2010) DOI: 10.1021/jm1011148<br />
R 2
3.1 Introduction<br />
In previous chapter-2 the dimorth rearrangement was performed to generate<br />
substituted 2-aminoimidazoles. The 2-aminoimidazole (2-AI) ring structure is of<br />
particular interest especially within the realms of medicinal chemistry. For example,<br />
several classes of marine natural products possessing this structure were recently<br />
discovered and identified. l Many of these compounds display a broad range of<br />
biological properties including antibacterial, anti-inflammatory, anticancer, and<br />
antiviral activity. Synthetic 2-AI derivatives, including 2-amino-histamine have been<br />
shown to have HI- and H2-receptor agonist and antagonist activity. 2 Other unrelated<br />
2-AI derivatives are selective 5-HT3 receptor antagonists, which may be<br />
potentially useful in the treatment of chemotherapy induced emesis 3 . Novel<br />
cephalosporins with incorporated 2-AI rings display both Gram-positive and Gramnegative<br />
antibacterial activity as well as good ß-lactamase stability 4 . In addition, 2-AI<br />
can serve as an important starting material in the preparation of 2-nitroimidazole<br />
(azomycin) a naturally occurring antibiotic 5 . Other synthetic analogs of 2nitroimidazole<br />
have been found to be cytotoxic toward hypoxic tumor cells and act as<br />
hypoxic cell radiosensitizers. 6<br />
The methods reported to prepare imidazoles are numerous, although only a limited<br />
number describe the direct synthesis of the corresponding 2-amino derivatives. The<br />
preparation of 2-AI was accomplished by the intramolecular cyclization of N-(2,2diethoxyethyl)guanidine<br />
upon acid hydrolysis. 7,8 The reaction of α-amino aldehydes<br />
or ketones with cyanamide appears to be the most commonly used direct approach. 8,9<br />
However, this reaction is pH sensitive and can lead to different products. In one<br />
case the formation of lH-imidazo[l,2-a]imidazoles was observed. 8 The dimerization<br />
and cyclization of a-amino aldehydes or ketones to symmetrical pyrazines is also a<br />
common problem associated with this method. 9a,10 A classical, although indirect<br />
approach to 2-AI's relies upon the formation of 2-arylazo derivatives via diazonium<br />
coupling, followed by reduction. 2a,7,11 The synthesis of 2-amino-4,5-diarylimidazoles<br />
was accomplished by the reduction of symmetrical 2,2'-azoimidazoles. 13 A more<br />
recent procedure was reported where 2-AI's were formed by the reaction of α -<br />
diketones with guanidine, followed by catalytic hydrogenation. 14 Other indirect<br />
approaches to 2-AI's involve ipso type substitutions of appropriate C-2 substituted
imidazoles, where the addition of a suitable nitrogen nucleophile is followed by the<br />
elimination of an activated leaving group such as a halogen or alkyl sulfoxide or<br />
sulfone. This method has been applied with limited success to electron-poor<br />
imidazoles or when fluorine is the leaving group. 4,15 An interesting synthetic route to<br />
functionalized 2-AI's, which were difficult to obtain by other methods, has been<br />
achieved using a base catalyzed rearrangement of 3-amino-1,2,4-oxadiazoles. 16<br />
Another type of heterocyclic rearrangement involves the reaction of 2-aminooxazoles<br />
with ammonia or formamide. 17 Most recently, the synthesis of 2-amino-4(5)-(αhydroxyalkyl)imidazoles<br />
has been demonstrated where 2-AI was reacted with<br />
aldehydes under neutral conditions. 18<br />
The microwave-assisted procedure for the synthesis of 1,4,5-substituted 2aminoimidazoles<br />
(Scheme-1) is two-step protocol based on the cyclocondensation of<br />
2-aminopyrimidines and bromocarbonyl compounds at 130-150 °C, followed by the<br />
cleavage of the intermediary imidazo[1,2-a]pyrimidin-1-ium salts with an excess of<br />
hydrazine.<br />
3.2 Reaction Scheme<br />
Scheme-1<br />
N<br />
N<br />
+<br />
N<br />
H<br />
Br O<br />
H<br />
H 2N<br />
N<br />
N<br />
R 1<br />
R 2<br />
R 1<br />
R 2<br />
MeCN<br />
MW<br />
80 °C, 30 min<br />
MeCN<br />
64% N2H4 MW<br />
100 °C, 10 min<br />
Br<br />
N<br />
N<br />
N<br />
N<br />
N R1 OH<br />
R 2<br />
PPA, 150 °C<br />
aq. HClO4 N R 1<br />
R 2<br />
ClO 4
3.3 Proposed Mechanism<br />
A possible mechanism for the pyrimidine ring cleavage upon reaction of salts (1) with<br />
amines, which involves the formation of azabutadienes (Scheme 2), Initially, the<br />
imidazo[1,2-a]pyrimidinium salt (1) undergoes a nucleophilic attack at its C-5<br />
position by a first molecule of amine. After rearrangement of the intermediate (A) and<br />
isomerisation of the resulting (B), (E, E)-azabutadiene (2) is formed. Initiated by<br />
protonation, the azabutadiene intermediate (C) in turn undergoes 1,4-addition with a<br />
second molecule of amine, finally resulting in the formation of 2-aminoimidazole (3)<br />
together with diazapentadienium salt (4) (Scheme-2).<br />
Consistent with this mechanism, the corresponding imidazo[1,2-a]pyrimidinium salts<br />
(1) can directly be cleaved to 2-aminoimidazoles (3) upon stirring with a large excess<br />
of secondary amine (6 or more equiv) at room temperature, while the isolated<br />
azabutadienes (2) appeared to be stable to 20 and more equivalents of piperidine in<br />
refluxing acetonitrile for 1 h. In contrary, azabutadienes (2) were quantitatively<br />
cleaved to 2-aminoimidazoles (3) in the presence of 1.5 equiv triethylamine<br />
hydrochloride salt (Scheme-3.5).<br />
Scheme-2<br />
N<br />
N N R1 H<br />
1<br />
R' 2N<br />
R 2<br />
R' 2NH<br />
-H<br />
NH<br />
N<br />
N<br />
R1 R 2<br />
R' 2N<br />
N<br />
R' 2NH<br />
A<br />
N<br />
N R 1<br />
R 2<br />
R' 2N<br />
R' 2N<br />
H<br />
C D<br />
R' 2N<br />
NH<br />
N<br />
N<br />
R1 R 2<br />
N<br />
N<br />
N R 1<br />
R 2<br />
B<br />
H 2N<br />
N<br />
N<br />
R 1<br />
3<br />
R' 2N<br />
R 2<br />
N<br />
N<br />
2<br />
N R 1<br />
R 2<br />
NR' 2<br />
+ NR' 2<br />
4
3.4 Result and Discussion<br />
It was found that the cyclocondensation of 2-alkylaminopyrimidines with αbromoacetophenones<br />
at 80 °C first led to stable 2-hydroxy-2,3-dihydroimidazo[1,2a]pyrimidinium<br />
bromides. The bicyclic nature of the structures clearly followed from<br />
1 H NMR data, indicating the doublet of doublets of the methylene fragments, as well<br />
as from 13 C NMR spectra.<br />
The 2-hydroxy-2,3-dihydroimidazo[1,2-a]pyrimidinium salts were obtained in good<br />
yields, and only for sterically hindered 2-alkylaminopyrimidines the yields slightly<br />
decreased. Dehydration of the 2-hydroxy-2,3-dihydroimidazo[1,2-a]pyrimidinium<br />
salts was successfully achieved by short (15 min) heating in polyphosphoric acid<br />
(PPA) at 150 °C. The corresponding imidazo[1,2-a]pyrimidinium salts were isolated<br />
and characterized as perchlorates, and in most cases the yields were almost<br />
quantitative. The structures of aromatic salts were completely consistent with their 1 H,<br />
and 13 C NMR data.<br />
The cleavage step was performed under microwave irradiation at 100 °C, using 7<br />
equivalents of hydrazine hydrate. Resulting 2-amino-1H-imidazoles were obtained in<br />
high yields. Using this protocol we have synthesized library of substituted 2aminoimidazole<br />
(Table-1)<br />
No.<br />
Compound<br />
Code<br />
H 2N<br />
N<br />
N<br />
R 1<br />
R 2<br />
R1 R2 Yield % m.p. o C<br />
1 BS-042 cyclododecane H 53 228-230<br />
2 BS-045 cyclooctane H 53 152-154<br />
3 BS-048 cycloheptane H 54 180-182<br />
4 BS-078 cyclohexane H 64 153-155
5 BS-081 cyclobutane H 47 77-79<br />
6 BS-085 C5H11 H 53 123-125<br />
7 BS-060 C6H13 H 53 -<br />
8 BS-051 C7H15 H 61 -<br />
9 BS-054 C8H17 H 55 -<br />
10 BS-063 C9H19 H 58 -<br />
11 BS-057 C10H21 H 53 -<br />
12 BS-066 C11H23 H 52 -<br />
13 BS-069 C12H25 H 52 -<br />
14 BS-072 C13H27 H 58 44-46<br />
15 BS-075 C14H19 H 64 44-46<br />
16 BS-116 cyclododecane Cl 42 221-223<br />
17 BS-117 cyclooctane Cl 55 207-209<br />
18 BS-118 cycloheptane Cl 51 180-182<br />
19 BS-128 cyclohexane Cl 37 179-181<br />
20 BS-130 cyclobutane Cl 40 156-158<br />
21 BS-129 C5H11 Cl 38 96-98<br />
22 BS-122 C6H13 Cl 53 76-78<br />
23 BS-119 C7H15 Cl 54 80-82<br />
24 BS-120 C8H17 Cl 57 76-78<br />
25 BS-123 C9H19 Cl 50 76-78<br />
26 BS-121 C10H21 Cl 52 89-91<br />
27 BS-124 C11H23 Cl 57 78-80<br />
28 BS-125 C12H25 Cl 57 79-81<br />
29 BS-126 C13H27 Cl 56 83-85<br />
30 BS-127 C14H19 Cl 51 82-83<br />
Yields are isolated yields over 2 steps.<br />
Table-1: compound library of substituted 2-aminoimidazole
No.<br />
H 2N<br />
Compound<br />
Code<br />
N<br />
N<br />
C8H17 R1<br />
R 1<br />
Yield %<br />
1 BS-199 4-OCH3 56<br />
2 BS-200 4-F 71<br />
3 BS-201 3,4-di Cl 64<br />
4 BS-202 3-Br 68<br />
5 BS-203 Naphthalen-1-yl 59<br />
6 BS-204 4-NO2 66<br />
7 BS-205 4-(4-NO2-Ph) 52<br />
8 BS-206 4-SO2Me 61<br />
9 BS-207 4-SMe 40<br />
10 BS-208 4-(4-biphenyl)_ 31<br />
Yields are isolated yields over 2 steps.<br />
Table -2: 2-aminoimidazole with octyl substitution at N-1 position<br />
3.5 Biofilm Activity<br />
The preliminary results from our lab the basic compound (A) with a non-substituted<br />
phenyl group at the C(5) position of the imidazole ring shows a moderate biofilm<br />
inhibitory activity (IC50 = 130 µM). Interestingly, substitution of the para- position of<br />
the phenyl ring with a chlorine (B) atom enhances the biofilm inhibitory activity<br />
about ten times (IC50 = 16 µM).<br />
H 2N<br />
N<br />
N<br />
H<br />
N<br />
H2N N<br />
H<br />
A B<br />
In an attempt to improve their biofilm inhibitory activity, we substituted the N1position<br />
of some of the para-substituted 4(5)-phenyl-2-aminoimidazoles with n-alkyl<br />
and cyclo-alkyl groups by using our previously established chemistry.<br />
Cl
3.5.1 N1-alkyl 2-aminoimidazoles<br />
In first instance a broad variety of alkyl groups, with lengths ranging from one carbon<br />
atom to 14 carbon atoms, were introduced at the N1-position of the 4(5)monosubstituted<br />
2-aminoimidazoles (A) and (B) resulting in compounds A-1 to A-<br />
14, and B-1 to B-13 respectively (Table-3). Each compound was assayed for the<br />
ability to inhibit S. Typhimurium ATCC14028 biofilm formation at 25 °C. As<br />
depicted in figure 1, a clear correlation was found between the length of the alkyl<br />
substituent and the biofilm inhibitory activity. In general, compounds with a short<br />
alkyl chain substitution (C1, C2, C3) on the N1-position have a lower activity as<br />
compared to their respective unsubstituted counterparts. This effect is most<br />
pronounced for the methyl substituent, which causes a reduction in the activity of at<br />
least 4 times. To a lesser extent, ethyl and isopropyl substituents also cause a<br />
reduction in activity. Substitution with a butyl group does not have an unequivocal<br />
effect. In the case of compound A-4, the activity is enhanced three-fold, while in the<br />
other cases the activity is reduced. Remarkably, all the compounds substituted with<br />
an alkyl group with an intermediate length between 5 and 10 carbon atoms are very<br />
active biofilm inhibitors, with IC50 values in general below 12 µM. The effect of<br />
substitution with a longer alkyl chain drastically depends on the nature of the<br />
substituent on the C5-position of the ring (phenyl or p-chlorophenyl). Indeed,<br />
replacement of the N1-hydrogen of compound (A) (phenyl on C5 of the ring) by a<br />
long alkyl chain (C11-C14) raises the activity drastically, from an IC50 of 130 µM for<br />
compound (A) to values below 8 µM for the substituted compounds (A-11 to A-14).<br />
In the case of compound (B) (p-chlorophenyl on C5 of the ring), substitution with an<br />
undecyl (B-10) and dodecyl (B-11) group results in very active compounds IC50<br />
values below 5 µM), while introduction of a tridecyl group (B-12) does not have a<br />
clear effect on the biofilm inhibitory activity and introduction of a tetradecyl (B-13)<br />
group drastically reduces the activity (IC50 = 453 µM). Subsequently, we investigated<br />
the influence of some of the most active representatives of this class of compounds on<br />
the planktonic growth curve of S. Typhimurium at 25°C. Most compounds only show<br />
a very small concentration range with a specific effect on biofilm formation and no<br />
effect on the planktonic growth (Table-3). Therefore we cannot exclude the possibility<br />
that the biofilm inhibitory effect of these compounds (at the higher concentrations) is<br />
partially due to a reduction of the planktonic growth of the bacteria in the growth
medium used in the set-up to monitor biofilm formation. Interestingly, compound A-<br />
14 with a long alkyl chain, does not follow this general trend as no effect on the<br />
growth was observed at 80 µM while the biofilm formation was inhibited at 9 µM.<br />
As depicted in table-3 and figure 1, a similar structure activity relationship was found<br />
for the inhibition of P. aeruginosa biofilm formation at 25°C. Again, introduction of<br />
a short alkyl chain at the N1-position generally results in a decreased activity (except<br />
for compound (A-2), while all the compounds with an intermediate alkyl chain length<br />
show very strong activities. The effect of substitution with a long alkyl chain is in this<br />
case also dependent on the nature of the C5-subsitutent. In the case of compound (A),<br />
substitution with a long alkyl chain results in very active compounds (A-10 to A-14),<br />
The activity of compound (B) is also decreased after introduction of a long N1-alkyl<br />
chain, (compounds B-9 to B-13). Interestingly, growth curve analysis revealed that<br />
these compounds are much less toxic to P. aeruginosa than to S. Typhimurium. Most<br />
compounds show a broad concentration range with only biofilm inhibition and no<br />
effect on the planktonic growth (table -3).<br />
No. Compound<br />
Code<br />
R1<br />
H 2N<br />
N<br />
N<br />
R 1<br />
R2<br />
R 2<br />
S. Typhimurium<br />
IC50<br />
P. aeruginosa<br />
IC50<br />
1 A-1 Me H 431.5 95.1<br />
2 A-2 Et H 206.0 20.6<br />
3 A-3 i-pr H 175.5 4.5<br />
4 A-4 n-Bu H 51.9 2.1<br />
5 A-5 n-Pen H 48.3 2.0<br />
6 A-6 n-Hex H 39.6 19.1<br />
7 A-7 n-Hep H 12.2 6.8<br />
8 A-8 n-Oct H 11.8 18.5<br />
9 A-9 n-Non H 5.9 8.3<br />
10 A-10 n-Dec H 6.1 15.0<br />
11 A-11 n-Und H 7.1 16.2
12 A-12 n-Dod H 7.1 12.8<br />
13 A-13 n-Trd H 5.9 27.2<br />
14 A-14 n-Tet H 8.6 9.7<br />
15 B-1 Me Cl 108.1 111.8<br />
16 B-2 Et Cl 53.1 11.3<br />
17 B-3 n-Bu Cl 57.8 16.9<br />
18 B-4 n-Pen Cl 8.0 6.0<br />
19 B-5 n-Hex Cl 4.9 5.3<br />
20 B-6 n-Hep Cl 9.3 2.6<br />
21 B-7 n-Oct Cl 5.8 3.9<br />
22 B-8 n-Non Cl 3.9 8.0<br />
23 B-9 n-Dec Cl 4.0 22.3<br />
24 B-10 n-Und Cl 4.0 42.9<br />
25 B-11 n-Dod Cl 6.1 49.7<br />
26 B-12 n-Trd Cl 19.5 33.8<br />
27 B-13 n-Tet Cl 453.3 19.0<br />
IC50: concentration of inhibitor needed to inhibit biofilm formation by 50%.<br />
Explanation Note: Number of compound code is also corresponding to the number of<br />
carbon chain at R1 position. (ie. A-1 is Methyl substituted )<br />
Table-3: Influence of N1-alkylated 2-aminoimidazoles on the biofilm formation and<br />
the planktonic growth of S. Typhimurium ATCC14028 and P. aeruginosa PA14 at<br />
25°C.
H 2N<br />
N<br />
N<br />
N<br />
H2N N<br />
R R<br />
Figure-1 Effect of introduction of alkyl chains with different lengths (1-14 C-<br />
atoms; at the N1-postion of compound A (Blue) and B (Red) on the IC50 (µM) for<br />
inhibition of the biofilm formation of S. Typhimurium ATCC14028 at 25°C in TSB<br />
1/20.<br />
3.5.2 Further Modification in the most active core structure<br />
The introduction of a n-octyl side chain at the N1-position of compounds (A) and (B)<br />
does result in very active inhibitors of both the Salmonella and Pseudomonas biofilm<br />
formation, we also decided to introduce an n-octyl chain at the N1-position of some<br />
other 4(5)-phenyl-2-amino-1H-imidazoles and evaluate the biofilm inhibitory activity<br />
of the substituted compounds (table 4). All the compounds (C8-1 to C8-10) are<br />
active inhibitors of both the S. Typhimurium and P. aeruginosa biofilm formation at<br />
25°C, except for compounds C8-7 and C8-10. These compounds have very bulky<br />
C5-substituents, which could diminish the solubility of the compounds in the growth<br />
medium, reduce the uptake into the cell or cause steric hindrance in the putative<br />
Cl
eceptor binding pocket. Growth curve analysis confirmed the previously described<br />
finding that the N1-alkylated 2-aminoimidazoles in general show a broad<br />
concentration range in which they specifically inhibit the biofilm formation of P.<br />
aeruginosa, without reducing the planktonic growth of the bacteria, while this<br />
concentration range is smaller in the case of S. Typhimurium. Compounds C8-7 and<br />
C8-10 are exceptions to this rule as we found them to slow down the planktonic<br />
growth of P. aeruginosa at the IC50 for biofilm inhibition.<br />
Sr.<br />
Compound<br />
Code<br />
H 2N<br />
N<br />
N<br />
C8H17 R1<br />
R 1<br />
S.<br />
Typhimurium<br />
IC50<br />
P. aeruginosa<br />
1 C8-1 4-OCH3 8.5 1.2<br />
2 C8-2 4-F 10.7 4.8<br />
3 C8-3 3,4-di Cl 3.7 -<br />
IC50<br />
4 C8-4 3-Br 11.1 40.6<br />
5 C8-5 Naphthalen-1-yl 6.5 17.6<br />
6 C8-6 4-NO2 35.4 -<br />
7 C8-7 4-(4-NO2-Ph) 116.6 >800<br />
8 C8-8 4-SO2Me 29.1 4.9<br />
9 C8-9 4-SMe 6.6 2.7<br />
10 C8-10 4-(4-biphenyl) >800 >800<br />
IC50: concentration of inhibitor needed to inhibit biofilm formation by 50%.<br />
Table-4: Influence of N1-octyl-2-aminoimidazoles on the biofilm formation and the<br />
planktonic growth of S. Typhimurium ATCC14028 and P. aeruginosa PA14 at 25°C.
3.5.3 Cyclo-alkyl 2-aminoimidazoles<br />
To determine whether the introduction of an intermediate or long cyclo-alkyl chain<br />
could also enhance the activity of the compounds, a broad variety of cyclo-alkyl<br />
groups, with lengths ranging from 4 to 12 carbon atoms, were introduced at the N1position<br />
of the 4(5)-monosubstituted 2-aminoimidazoles (A) and (B) (table 5). The<br />
compounds were tested against biofilm formation of S. Typhimurium and P.<br />
aeruginosa at 25°C. As depicted introduction of an intermediate cyclo-alkyl chain<br />
does improve the biofilm inhibitory activity of compound (A) against S. Typhimurium<br />
and even more drastically against P. aeruginosa. In the case of Salmonella,<br />
introduction of a cyclo-heptyl chain yields the most active compound (compound A-<br />
Cy-5) with an IC50 of 27 µM, as compared to 130 µM for compound (A). In the case<br />
of Pseudomonas, cyclo-hexyl and cyclo-octyl are the best substituents as introduction<br />
of these groups improves the activity drastically from an IC50 of 73 µM. All<br />
compounds derived from (B) by introduction of an intermediate length side chain are<br />
very strong inhibitors of the Salmonella and Pseudomonas biofilm formation (table<br />
5), although their activity is not markedly better than the activity of the unsubstituted<br />
compounds. Introduction of a dodecyl side chain abolishes the activity of all three<br />
compounds against P. aeruginosa biofilm formation, while the effect of a cyclododecyl<br />
substituent on the Salmonella biofilm inhibition depends on the nature of the<br />
C5-group. Indeed, compound A-Cy-7, derived from (A) by introduction of a cyclododecyl<br />
group, is a very strong biofilm inhibitor, while compound B-Cy-6, derived<br />
from (B), is a moderate biofilm inhibitor. As in the case of the n-alkyl substituents,<br />
growth curve analysis revealed that most compounds with cyclo-alkyl substituents<br />
only possess a very small concentration range with a selective effect on the<br />
Salmonella biofilm formation and no effect on the planktonic growth. An exception<br />
is compound A-Cy-7, with a cyclo-dodecyl side chain, which does not affect the<br />
planktonic growth of Salmonella at 80 µM (the highest concentration tested), while<br />
the IC50 for biofilm inhibition is 15 µM. Interestingly, the concentration range<br />
between biofilm inhibition and growth inhibition is much broader in the case of P.<br />
aeruginosa (table-5).
No.<br />
Compound<br />
Code<br />
R1<br />
H 2N<br />
N<br />
N<br />
R 1<br />
R2<br />
R 2<br />
S. Typhimurium<br />
IC50<br />
P. aeruginosa<br />
IC50<br />
1 A-Cy-1 c-Pr H 89.6 35.0<br />
2 A-Cy-2 c-Bu H 116.3 19.9<br />
3 A-Cy-3 c-Pen H 70.7 12.6<br />
4 A-Cy-4 c-Hex H 85.1 4.6<br />
5 A-Cy-5 c-Hep H 26.8 14.2<br />
6 A-Cy-6 c-Oct H 40.4 4.5<br />
7 A-Cy-7 c-Dod H 14.5 >800<br />
8 B-Cy-1 c-Pr Cl 54.8 13.0<br />
9 B-Cy-2 c-Bu Cl 11.5 6.0<br />
10 B-Cy-3 c-Hex Cl 33.2 11.2<br />
11 B-Cy-4 c-Hep Cl 15.6 4.0<br />
12 B-Cy-5 c-Oct Cl 12.8 48.6<br />
13 B-Cy-6 c-Dod Cl 120.2 >800<br />
IC50: concentration of inhibitor needed to inhibit biofilm formation by 50%.<br />
Explanation Note: Number of compound code is also corresponding to the ring size of<br />
cyclic substitution at R1 position. (ie. A-Cy-1 is Cyclopropyl substituted )<br />
Table-5: Influence of N1-cyclo-alkyl-2-aminoimidazoles on the biofilm formation<br />
and the planktonic growth of S. Typhimurium and P. aeruginosa PA14 at 25°C.
3.6. Conclusion<br />
In the present study, we investigated the effect of the different substitution on 2aminoimidazoles<br />
on the biofilm formation of S. Typhimurium and P. aeruginosa. We<br />
found that our simplest 2-aminoimidazole structure, 4(5)-phenyl-2-amino-1Himidazole<br />
(A), showed a moderate biofilm inhibitory activity both against S.<br />
Typhimurium and P. aeruginosa. Substitution of the para-position of the 4(5)-phenyl<br />
ring with a chlorine atom (B) enhanced the biofilm inhibitory activity about ten times.<br />
We were able to delineate a relationship between the length of the N1-alkyl or N1cyclo-alkyl<br />
chain of the N1-substituted 2-aminoimidazoles and their biofilm<br />
inhibitory activity. In general, introduction of a short alkyl chain at the N1-position<br />
resulted in a decreased activity against S. Typhimurium and P. aeruginosa biofilm<br />
formation, while all compounds with an intermediate alkyl or cyclo-alkyl chain length<br />
showed very strong activities in both test systems. The introduction of a long alkyl or<br />
cylco-alkyl chain could either drastically enhance the activity or totally abolish the<br />
activity, depending on the nature of the C5-subsitutent and the bacterial species tested.<br />
Growth curve analysis revealed that the N1-(cyclo-)alkylated 2-aminoimidazoles<br />
show a broad concentration range in which they specifically inhibit the biofilm<br />
formation of P. aeruginosa, without retarding the planktonic growth of the bacteria.<br />
However, these compounds were much more toxic to S. Typhimurium. Therefore, we<br />
cannot exclude the possibility that a part of the inhibitory effect against Salmonella<br />
biofilms (at the higher concentrations) is due to a reduction of the planktonic growth<br />
of the bacteria in the growth medium surrounding the surface on which the biofilms<br />
are formed.<br />
In conclusion, the 2-aminoimidazoles and the imidazopyrimidinium salts of the<br />
present study are valuable candidates in the development of therapeutics and<br />
sanitizers for the combat of biofilm formation by S. Typhimurium, P. aeruginosa and<br />
possibly other pathogenic bacteria.
3.7 Experimental<br />
3.7.1 General Methods<br />
All chemical reagents were used without further purification. Solvents for column<br />
chromatography and TLC were laboratory grade and distilled before use. For thinlayer<br />
chromatography (TLC), analytical TLC plates (Alugram SIL G/UV254 (E. M.<br />
Merk) were used. Column chromatography was performed with flash silica gel (100-<br />
200 mesh) or neutral alumina oxide (50-200 micron). 1 H and 13 C NMR spectra were<br />
recorded on a Bruker Avance 300 (300 MHz) or a Bruker AMX-400 (400 MHz)<br />
spectrometers. NMR samples were run in the indicated solvents and were referenced<br />
internally. Chemical shift values were quoted in ppm and coupling constants were<br />
quoted in Hz. Chemical shift multiplicities were reported as s = singlet, d = doublet, t<br />
= triplet, q = quartet, m = multiplet and br = broad. Low-resolution mass spectra were<br />
recorded on a HEWLETT-PACKARD instrument (CI or EI) and LCQ Advantage<br />
instrument (ESI). High-resolution mass spectra (EI) were recorded on a KRATOS<br />
MS50TC instrument. Melting points were determined using Reichert-Jung Thermovar<br />
apparatus and were uncorrected.<br />
3.7.2 Microwave Irradiation Experiments<br />
Microwave irradiation experiments were carried out in a dedicated CEM-Discover<br />
mono-mode microwave apparatus or Milestone MicroSYNTH multi-mode microwave<br />
reactor (Laboratory Microwave Systems). Microwave apparatuses were used in the<br />
standard configuration as delivered, operating at a frequency 2.45 GHz with<br />
continuous irradiation power from 0 to 400 W. The reactions were carried out in 10,<br />
20, 30 and 50 mL glass tubes. The temperature was measured with an IR sensor on<br />
the outer surface of the process vial or fibre optic sensor inside the process vial. After<br />
the irradiation period, the reaction vessel was cooled rapidly (2-5 min) to ambient<br />
temperature by air jet cooling.
3.8. Experimental protocols<br />
3.8.1 General Procedure for the Preparation of hydroxy Salts. (Microwave)<br />
According to process described in chapeter-2 40 new hydrocy salts were<br />
synthesized<br />
3.8.2 General Procedure for the Preparation of HClO4 Salts.<br />
A mixture of 84% polyphosphoric acid (3 g) and hydroxy salts (3 mmol) was heated<br />
in 50 ml beaker upon intensive stirring at 150 °C for 15 min. After cooling to the<br />
room temperature the resulting viscous mass was dissolved in 30 ml of water and 1 ml<br />
(10 mmol) of 70% HClO4 was added dropwise upon mild stirring. The white<br />
precipitate was washed with distilled water (3×10 mL), ether (2×10 mL) until a<br />
neutral reaction of the pH paper and then dried over P2O5 to give salt as fine white<br />
crystals.<br />
In similar manner 40 new compounds were synthesized.<br />
3.8.3 General Procedure for the Microwave-Assisted Synthesis of 2aminoimidazoles.<br />
To a suspension of HClO4 salt (2 mmol) in MeCN (5 mL) hydrazine hydrate (0.7 mL,<br />
14 mmol of a 64% solution, 7 equiv) was added, and the mixture was irradiated in the<br />
sealed Milestone MicroSYNTH microwave reactor for 10 min at a ceiling<br />
temperature of 100 °C at 150 W maximum power. After cooling down the reaction<br />
was worked up by diluting with DCM (300 mL), washing with sat. NH4Cl solution<br />
(150 mL), brine (150 mL) and water (2×150 mL) and drying over anhydrous Na2SO4.<br />
After filtration and concentration the resulting residue was purified by column<br />
chromatography (silica gel; DCM−MeOH, 9:1 v/v with 3% TEA) to afford the<br />
product as a colourless solid.<br />
40 new compounds were synthesized In similar manner.
3.9 Spectral Characterization<br />
1-Cyclododecyl-5-phenyl-1H-imidazol-2-amine (BS-042)<br />
H 2N<br />
N<br />
N<br />
Yield: 42 %. Mp: 228-230 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.38 (m, 5H), 6.59 (s,<br />
1H), 4.16 (m, 1H), 3.98 (br, 2H), 1.88 (m, 5H), 1.22(m, 14H), 0.90 (m, 3H). 13 C NMR<br />
(75.5 MHz, CDCl3): δ =148.4, 131.4, 131.2, 129.8 (× 2), 128.3 (×2), 127.5, 122.1,<br />
50.0, 29.1(×2), 24.0 (×2), 23.9 (×2), 22.6 (×2), 21.9 (×2), 21.5. HRMS (EI):C21H31N3,<br />
calcd 325.2518, found: 325.2511.<br />
1-Cyclooctyl-5-phenyl-1H-imidazol-2-amine (BS-045)<br />
H 2N<br />
N<br />
N<br />
Yield: 53 %. Mp: 152-154 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.43-7.28 (m, 5H),<br />
6.60 (s, 1H), 4.24 (m, 1H), 3.98 (br, 2H), 2.11 (m, 2H), 1.87 (m, 4H), 1.50 (m, 7H),<br />
1.25 (m, 1H). 13 C NMR (75.5 MHz, CDCl3): δ =148.1, 131.2, 129.5, 129.0 (×2),<br />
128.4 (×2), 127.3, 122.7, 54.5, 33.1(×2), 26.2, 25.8 (×2), 25.3 (×2). HRMS (EI):<br />
C17H23N3, calcd 269.1892, found: 269.1893.<br />
1-Cycloheptyl-5-phenyl-1H-imidazol-2-amine (BS-048)<br />
H 2N<br />
N<br />
N<br />
Yield: 54 %. Mp: 180-182 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.43-7.29 (m, 5H),<br />
6.59 (s, 1H), 4.09 (m, 3H), 2.13 (m, 2H), 1.95 (m, 2H), 1.73 (m, 2H), 1.54 (m, 6H).<br />
13 C NMR (75.5 MHz, CDCl3): δ =148.2, 131.1, 129.6, 128.9 (×2), 128.5 (×2), 127.3,
122.6, 54.6, 33.3(×2), 27.3 (×2), 25.7 (×2). HRMS (EI): C16H21N3, calcd 255.1735,<br />
found: 255.1759.<br />
1-Heptyl-5-phenyl-1H-imidazol-2-amine (BS-051)<br />
H 2N<br />
N<br />
N<br />
C7H15 Yield: 61 %. 1 H NMR (300 MHz, CDCl3): δ = 7.43-7.31 (m, 5H), 6.67 (s, 1H), 3.95<br />
(br, 2H), 3.75(t, J = 7.5 Hz, 2H), 1.59 (m, 2H), 1.17 (m, 8H), 0.84 (t, J = 6.5 Hz, 3H).<br />
13<br />
C NMR (75.5 MHz, CDCl3): δ =149.0, 131.0, 129.4, 128.6 (×2), 128.2 (×2), 127.2,<br />
122.6, 43.1, 31.5, 29.5, 28.6, 26.4, 22.4, 14.0. HRMS (EI): C16H23N3, calcd 257.1892,<br />
found: 257.1908.<br />
1-Octyl-5-phenyl-1H-imidazol-2-amine (BS-054)<br />
H 2N<br />
N<br />
N<br />
C8H17 Yield: 55 %. 1 H NMR (300 MHz, CDCl3): δ = 7.40-7.31 (m, 5H), 6.67 (s, 1H), 4.02<br />
(br, 2H), 3.75(t, J = 7.3 Hz, 2H), 1.59 (m, 2H), 1.17 (m, 10H), 0.85 (t, J = 6.6 Hz,<br />
3H). 13 C NMR (75.5 MHz, CDCl3): δ =149.1, 131.0, 129.4, 128.6 (×2), 128.2 (×2),<br />
127.2, 122.6, 43.1, 31.6, 29.5, 29.0, 28.9, 26.4, 22.2, 14.0. HRMS (EI): C17H25N3,<br />
calcd 271.2048, found: 271.2035.<br />
1-Decyl-5-phenyl-1H-imidazol-2-amine (BS-057)<br />
H 2N<br />
N<br />
N<br />
C 10H 21<br />
Yield: 53 %. 1 H NMR (300 MHz, CDCl3): δ = 7.41-7.29 (m, 5H), 6.67 (s, 1H), 4.15<br />
(br, 2H), 3.75(t, J = 7.3 Hz, 2H), 1.58 (m, 2H), 1.21 (m, 14H), 0.87 (t, J = 6.5 Hz,<br />
3H). 13 C NMR (75.5 MHz, CDCl3): δ =148.9, 131.0, 129.4, 128.6 (×2), 128.3 (×2),<br />
127.2, 122.6, 43.1, 31.8, 29.5, 29.4, 28.3, 29.2, 28.9, 26.4, 22.2, 14.1. HRMS (EI):<br />
C19H29N3, calcd 299.2361, found: 299.2365.
1-Hexyl-5-phenyl-1H-imidazol-2-amine (BS-060)<br />
H 2N<br />
N<br />
N<br />
C6H13 Yield: 53 %. 1 H NMR (300 MHz, CDCl3): δ = 7.41-7.30 (m, 5H), 6.67 (s, 1H), 3.98<br />
(br, 2H), 3.75(t, J = 7.4 Hz, 2H), 1.59 (m, 2H), 1.18 (m, 6H), 0.82 (t, J = 6.4 Hz, 3H).<br />
13<br />
C NMR (75.5 MHz, CDCl3): δ =149.0, 131.0, 129.4, 128.6 (×2), 128.2 (×2), 127.2,<br />
122.8, 43.1, 31.1, 29.5, 26.1, 22.4, 13.8. HRMS (EI): C15H21N3, calcd 243.1735,<br />
found: 243.1730.<br />
1-Nonyl-5-phenyl-1H-imidazol-2-amine (BS-063)<br />
H 2N<br />
N<br />
N<br />
C9H19 Yield: 58 %. 1 H NMR (300 MHz, CDCl3): δ = 7.31 (m, 5H), 6.67 (s, 1H), 3.95 (br,<br />
2H), 3.75(t, J = 7.5 Hz, 2H), 1.58 (m, 2H), 1.17 (m, 12H), 0.86 (t, J = 6.6 Hz, 3H).<br />
13<br />
C NMR (75.5 MHz, CDCl3): δ =152.6, 134.6, 132.9, 132.1 (× 2), 131.7 (× 2), 130.7,<br />
126.4, 46.6, 35.3, 33.0, 32.8, 32.6, 32.5, 30.0, 26.1, 17.6. HRMS (EI): C18H27N3, calcd<br />
285.2205, found: 285.2222.<br />
5-Phenyl-1-undecyl-1H-imidazol-2-amine (BS-066)<br />
H 2N<br />
N<br />
N<br />
C 11H 23<br />
Yield: 52 %. 1 H NMR (300 MHz, CDCl3): δ = 7.42-7.31 (m, 5H), 6.67 (s, 1H), 3.99<br />
(br, 2H), 3.75 (t, J = 7.0 Hz, 2H), 1.59 (m, 2H), 1.17 (m, 16H), 0.87 (t, J = 6.4 Hz,<br />
3H). 13 C NMR (75.5 MHz, CDCl3): δ =149.1, 131.0, 129.4, 128.6 (×2), 128.2 (×2),<br />
127.1, 122.9, 43.1, 31.8, 29.5 (× 2), 29.4, 29.3, 29.2, 28.9, 26.4, 22.6, 14.1. HRMS<br />
(EI): C20H31N3, calcd 313.2518, found: 313.2512.<br />
1-Dodecyl-5-phenyl-1H-imidazol-2-amine (BS-069)<br />
H 2N<br />
N<br />
N<br />
C 12H 25
Yield: 52 %. 1 H NMR (300 MHz, CDCl3): δ = 7.39-7.30 (m, 5H), 6.67 (s, 1H), 3.99<br />
(br, 2H), 3.75 (t, J = 7.2 Hz, 2H), 1.58 (m, 2H), 1.17 (m, 18H), 0.88 (t, J = 6.4 Hz,<br />
3H). 13 C NMR (75.5 MHz, CDCl3): δ =149.0, 131.1, 129.4, 128.6 (×2), 128.2 (×2),<br />
127.1, 123.0, 43.1, 31.9, 29.5 (× 3), 29.4, 29.3(× 2), 28.9, 26.4, 22.6, 14.1. HRMS<br />
(EI): C21H33N3, calcd 327.2674, found: 327.2663.<br />
5-Phenyl-1-tridecyl-1H-imidazol-2-amine (BS-072)<br />
H 2N<br />
N<br />
N<br />
C 13H 27<br />
Yield: 58 %. Mp: 44-46 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.40-7.31 (m, 5H), 6.67<br />
(s, 1H), 3.99 (br, 2H), 3.75 (t, J = 7.3 Hz, 2H), 1.58 (m, 2H), 1.17 (m, 20H), 0.88 (t, J<br />
= 6.4 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =148.9, 131.0, 129.4, 128.6 (×2),<br />
128.2 (×2), 127.1, 122.7, 43.1, 31.9, 29.5 (× 7), 28.9, 26.4, 22.6, 14.1. HRMS (EI):<br />
C22H35N3, calcd 341.2831, found: 341.2827.<br />
5-Phenyl-1-tetradecyl-1H-imidazol-2-amine (BS-075)<br />
H 2N<br />
N<br />
N<br />
C 14H 29<br />
Yield: 64 %. Mp: 44-46 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.41-7.30 (m, 5H), 6.67<br />
(s, 1H), 4.00 (br, 2H), 3.75 (t, J = 7.4 Hz, 2H), 1.58 (m, 2H), 1.17 (m, 22H), 0.88 (t, J<br />
= 6.3 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =148.8, 131.0, 129.5, 128.6 (×2),<br />
128.3 (×2), 127.2, 122.8, 43.1, 31.9, 29.6 (× 8), 28.9, 26.4, 22.6, 14.1. HRMS (EI):<br />
C23H37N3, calcd 355.2987, found: 355.3016.<br />
1-Cyclohexyl-5-phenyl-1H-imidazol-2-amine (BS-078)<br />
H 2N<br />
N<br />
N<br />
Yield: 64 %. Mp: 153-155 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.42-7.28 (m, 5H),<br />
6.60 (s, 1H), 3.89 (m, 3H), 1.88 (m, 6H), 1.64 (m, 1H), 1.18 (m, 3H). 13 C NMR (75.5
MHz, CDCl3): δ =148.4, 131.2, 130.0, 129.0 (×2), 128.5 (×2), 127.3, 122.6, 55.1,<br />
31.2(×2), 25.9 (×2), 25.1. HRMS (EI): C15H19N3, calcd 241.1579, found: 241.1589.<br />
1-Cyclobutyl-5-phenyl-1H-imidazol-2-amine (BS-081)<br />
H 2N<br />
N<br />
N<br />
Yield: 47%. Mp: 77-79 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.41-7.28 (m, 5H), 6.58<br />
(s, 1H), 4.61 (m, 1H), 4.07 (br, 2H), 2.51 (m, 2H), 2.27 (m, 2H), 1.75 (m, 2H). 13 C<br />
NMR (75.5 MHz, CDCl3): δ =149.1, 131.3, 129.7, 128.6 (×2), 128.3 (×2), 127.1,<br />
122.9, 49.2, 29.5 (×2), 15.0. HRMS (EI): C13H15N3, calcd 213.1266, found: 213.1268.<br />
1-Pentyl-5-phenyl-1H-imidazol-2-amine (BS-085)<br />
H 2N<br />
N<br />
N<br />
C5H11 Yield: 53 %. Mp: 123-125 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.46-7.29 (m, 5H),<br />
6.67 (s, 1H), 4.00 (br, 2H), 3.75 (t, J = 7.5 Hz, 2H), 1.59 (m, 2H), 1.19 (m, 4H), 0.81<br />
(t, J = 6.7 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =149.0, 131.0, 129.4, 128.6 (×2),<br />
128.2 (×2), 127.2, 122.8, 43.1, 29.2, 28.6, 22.0, 13.8. HRMS (EI): C14H19N3, calcd<br />
229.1579, found: 229.1594.<br />
5-(4-Chlorophenyl)-1-cyclododecyl-1H-imidazol-2-amine (BS-116)<br />
H 2N<br />
N<br />
N<br />
Yield: 42 %. Mp: 221-223 ° C 1 H NMR (300 MHz, CDCl3): δ = 7.38 (m, 5H), 6.59 (s,<br />
1H), 4.16 (m, 1H), 3.98 (br, 2H), 1.88 (m, 5H), 1.22(m, 14H), 0.90 (m, 3H). 13 C NMR<br />
(75.5 MHz, CDCl3): δ =148.4, 131.4, 131.2, 129.8 (×2), 128.3 (×2), 127.5, 122.1,<br />
50.0, 29.1(×2), 24.0 (×2), 23.9 (×2), 22.6 (×2), 21.9 (×2), 21.5. HRMS (EI):C21H31N3,<br />
calcd 325.2518, found: 325.2118.<br />
Cl
5-(4-Chlorophenyl)-1-cyclooctyl-1H-imidazol-2-amine (BS-117)<br />
H 2N<br />
N<br />
N<br />
Yield: 55 %. Mp: 207-209 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.37 (d, J = 8.4 Hz,<br />
2H), 7.20 (d, J = 8.4 Hz, 2H), 6.59 (s, 1H), 4.18 (m, 1H), 4.02 (br, 2H), 2.12 (m, 2H),<br />
1.85 (m, 4H), 1.50 (m, 7H), 1.25 (m, 1H). 13 C NMR (75.5 MHz, CDCl3): δ =148.6,<br />
131.1, 130.0 (× 2), 129.7, 128.7 (×2), 128.3, 123.4, 56.7, 33.3(×2), 27.2 (×3), 25.7<br />
(×2). HRMS (EI): C17H22ClN3, calcd 303.1502, found: 303.1519.<br />
5-(4-Chlorophenyl)-1-cycloheptyl-1H-imidazol-2-amine (BS-118)<br />
H 2N<br />
N<br />
N<br />
Yield: 51 %. Mp: 180-182 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.36 (d, J = 8.4 Hz,<br />
2H), 7.18 (d, J = 8.4 Hz, 2H), 6.59 (s, 1H), 4.00 (m, 3H), 2.12 (m, 2H), 1.92 (m, 2H),<br />
1.75 (m, 2H), 1.55 (m, 6H). 13 C NMR (75.5 MHz, CDCl3): δ =148.6, 131.1, 130.0<br />
(×2), 129.7, 128.7 (×2), 128.3, 123.4, 56.7, 33.3(×2), 27.2 (×2), 25.7 (×2). HRMS<br />
(EI): C16H20ClN3, calcd 289.1346, found: 289.1364.<br />
5-(4-Chlorophenyl)-1-heptyl-1H-imidazol-2-amine (BS-119)<br />
H 2N<br />
N<br />
N<br />
C7H15 Yield: 54 %. Mp: 80-82 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.35 (d, J = 8.4 Hz, 2H),<br />
7.23 (d, J = 8.4 Hz, 2H), 6.66 (s, 1H), 4.02 (br, 2H), 3.72(t, J = 7.5 Hz, 2H), 1.57 (m,<br />
2H), 1.18 (m, 8H), 0.84 (t, J = 6.5 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =149.4,<br />
133.0, 129.6, 129.3 (×2), 128.8 (×2), 128.1, 123.5, 43.1, 31.5, 29.5, 28.6, 26.4, 22.5,<br />
14.2. HRMS (EI): C16H22ClN3, calcd 291.1502, found: 291.1507.<br />
Cl<br />
Cl<br />
Cl
5-(4-Chlorophenyl)-1-octyl-1H-imidazol-2-amine (BS-120)<br />
H 2N<br />
N<br />
N<br />
C8H17 Yield: 57 %. Mp: 76-78 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.35 (d, J = 8.4 Hz, 2H),<br />
7.23 (d, J = 9.3 Hz, 2H), 6.67 (s, 1H), 3.95 (br, 2H), 3.73(t, J = 7.2 Hz, 2H), 1.57 (m,<br />
2H), 1.18 (m, 10H), 0.86 (t, J = 6.6 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =149.2,<br />
131.1, 129.5, 129.3 (×2), 128.8 (×2), 128.2, 123.4, 43.1, 31.6, 29.5, 29.0, 28.9, 26.4,<br />
22.2, 14.0. HRMS (EI): C17H24ClN3, calcd 305.1659, found: 305.1649.<br />
5-(4-Chlorophenyl)-1-decyl-1H-imidazol-2-amine (BS-121)<br />
H 2N<br />
N<br />
N<br />
C 10H 21<br />
Yield: 52 %. Mp: 89-91 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.35 (d, J = 8.4 Hz, 2H),<br />
7.33 (d, J = 9.0 Hz, 2H), 6.67 (s, 1H), 3.97 (br, 2H), 3.72 (t, J = 7.4 Hz, 2H), 1.57 (m,<br />
2H), 1.18 (m, 14H), 0.87 (t, J = 6.5 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =148.3,<br />
133.0, 129.5, 129.3 (×2), 128.8 (×2), 128.2, 123.5, 43.1, 31.8, 29.5, 29.4 (×2), 29.2,<br />
28.9, 26.4, 22.6, 14.1. HRMS (EI): C19H28ClN3, calcd 333.1972, found: 333.1999.<br />
5-(4-Chlorophenyl)-1-hexyl-1H-imidazol-2-amine (BS-122)<br />
H 2N<br />
N<br />
N<br />
C6H13 Yield: 53 %. Mp: 76-78 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.35 (d, J = 8.4 Hz, 2H),<br />
7.23 (d, J = 8.4 Hz, 2H), 6.67 (s, 1H), 3.97 (br, 2H), 3.37 (t, J = 7.9 Hz, 2H), 1.57 (m,<br />
2H), 1.18 (m, 6H), 0.83 (t, J = 6.4 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =149.3,<br />
133.0, 129.5, 129.3 (×2), 128.8 (×2), 128.2, 123.5, 43.1, 31.1, 29.5, 26.1, 22.4, 13.9.<br />
HRMS (EI): C15H20N3, calcd 277.1346, found: 277.1353.<br />
5-(4-Chlorophenyl)-1-nonyl-1H-imidazol-2-amine (BS-123)<br />
H 2N<br />
N<br />
N<br />
C9H19 Cl<br />
Cl<br />
Cl<br />
Cl
Yield: 50 %. Mp: 76-78 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.35 (d, J = 8.5 Hz, 2H),<br />
7.23 (d, J = 8.9 Hz, 2H), 6.67 (s, 1H), 4.00 (br, 2H), 3.73 (t, J = 7.3 Hz, 2H), 1.57 (m,<br />
2H), 1.18 (m, 12H), 0.87 (t, J = 6.6 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =152.2,<br />
133.1, 129.5, 129.3 (× 2), 128.8 (× 2), 128.2, 123.6, 43.1, 31.7, 29.6, 29.3, 29.1, 28.9,<br />
26.4, 22.6, 14.0. HRMS (EI): C18H26ClN3, calcd 319.1815, found: 319.1808.<br />
5-(4-Chlorophenyl)-1-undecyl-1H-imidazol-2-amine (BS-124)<br />
H 2N<br />
N<br />
N<br />
C 11H 23<br />
Yield: 57 %. Mp: 78-80 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.35 (d, J = 8.4 Hz, 2H),<br />
7.23 (d, J = 9.1 Hz, 2H), 6.66 (s, 1H), 4.00 (br, 2H), 3.72 (t, J = 7.3 Hz, 2H), 1.57 (m,<br />
2H), 1.18 (m, 16H), 0.88 (t, J = 6.4 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =149.2,<br />
133.1, 129.5, 129.3 (×2), 128.8 (×2), 128.2, 123.6, 43.1, 31.8, 29.6, 29.5, 29.4 (×2),<br />
29.3, 28.9, 26.4, 22.6, 14.1. HRMS (EI): C20H30ClN3, calcd 347.2128, found:<br />
347.2136.<br />
5-(4-Chlorophenyl)-1-dodecyl-1H-imidazol-2-amine (BS-125)<br />
H 2N<br />
N<br />
N<br />
C 12H 25<br />
Yield: 57 %. Mp: 79-91 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.35 (d, J = 8.4 Hz, 2H),<br />
7.23 (d, J = 8.9 Hz, 2H), 6.67 (s, 1H), 3.99 (br, 2H), 3.72 (m, 2H), 1.58 (m, 2H), 1.17<br />
(m, 18H), 0.88 (m, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =149.1, 133.1, 129.5, 129.3<br />
(×2), 128.8 (×2), 128.2, 123.6, 43.1, 31.9, 29.6 (× 3), 29.4 (× 2), 29.3, 28.9, 26.4,<br />
22.6, 14.1. HRMS (EI): C21H32ClN3, calcd 361.2285, found: 361.2281.<br />
5-(4-Chlorophenyl)-1-tridecyl-1H-imidazol-2-amine (BS-126)<br />
H 2N<br />
N<br />
N<br />
C 13H 27<br />
Yield: 56 %. Mp: 83-85 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.35 (d, J = 8.5 Hz, 2H),<br />
7.23 (d, J = 9.3 Hz, 2H), 6.67 (s, 1H), 3.99 (br, 2H), 3.72 (t, J = 7.3 Hz, 2H), 1.57 (m,<br />
2H), 1.17 (m, 20H), 0.88 (t, J = 6.3 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =149.1,<br />
Cl<br />
Cl<br />
Cl
133.1, 129.5, 129.3 (×2), 128.8 (×2), 128.2, 123.6, 43.1, 31.9, 29.6 (×4), 29.5, 29.4,<br />
29.3, 28.9, 26.4, 22.6, 14.1. HRMS (EI): C22H34ClN3, calcd 375.2441, found:<br />
375.2446.<br />
5-(4-Chlorophenyl)-1-tetradecyl-1H-imidazol-2-amine (BS-127)<br />
H 2N<br />
N<br />
N<br />
C 14H 29<br />
Yield: 51 %. Mp: 82-83 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.35 (d, J = 8.5 Hz, 2H),<br />
7.23 (d, J = 8.7 Hz, 2H), 6.67 (s, 1H), 4.00 (br, 2H), 3.72 (t, J = 7.3 Hz, 2H), 1.55 (m,<br />
2H), 1.17 (m, 22H), 0.87 (m, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =149.1, 133.1,<br />
129.5, 129.3 (×2), 128.8 (×2), 128.2, 123.6, 43.1, 31.9, 29.6 (×5), 29.5, 29.4 (×2),<br />
29.0, 26.4, 22.7, 14.1. HRMS (EI): C23H36ClN3, calcd 389.2598, found: 389.2602.<br />
5-(4-Chlorophenyl)-1-cyclohexyl-1H-imidazol-2-amine (BS-128)<br />
H 2N<br />
N<br />
N<br />
Yield: 37 %. Mp: 179-181 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.35 (d, J = 8.4 Hz,<br />
2H), 7.18 (d, J = 8.4 Hz, 2H), 6.60 (s, 1H), 4.00 (br, 2H), 3.81 (m, 1H), 1.87 (m, 6H),<br />
1.66 (m, 1H), 1.23 (m, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =148.8, 133.2, 130.2<br />
(×2), 129.8, 128.9, 128.7 (×2), 123.7, 55.2, 31.2(×2), 25.9 (×2), 25.1. HRMS (EI):<br />
C15H18ClN3, calcd 275.1189, found: 275.1187.<br />
5-(4-Chlorophenyl)-1-pentyl-1H-imidazol-2-amine (BS-129)<br />
H 2N<br />
N<br />
N<br />
C5H11 Yield: 38 %. Mp: 96-98 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.35 (d, J = 8.4 Hz, 2H),<br />
7.23 (d, J = 8.8 Hz, 2H), 6.67 (s, 1H), 4.08 (br, 2H), 3.73 (t, J = 7.3 Hz, 2H), 1.58 (m,<br />
2H), 1.22 (m, 4H), 0.82 (t, J = 6.6 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =149.3,<br />
133.0, 129.5, 129.3 (×2), 128.8 (×2), 128.2, 123.4, 43.2, 29.3, 28.6, 22.1, 13.8. HRMS<br />
(EI): C14H18ClN3, calcd 263.1189, found: 263.1185.<br />
Cl<br />
Cl<br />
Cl
5-(4-Chlorophenyl)-1-cyclobutyl-1H-imidazol-2-amine (BS-130)<br />
H 2N<br />
N<br />
N<br />
Yield: 40%. Mp: 156-159 ° C. 1 H NMR (300 MHz, CDCl3): δ = 7.33 (d, J = 8.4 Hz,<br />
2H), 7.19 (d, J = 8.5 Hz, 2H), 6.57 (s, 1H), 4.55 (m, 1H), 4.00 (br, 2H), 2.47 (m, 2H),<br />
2.27 (m, 2H), 1.76 (m, 2H). 13 C NMR (75.5 MHz, CDCl3): δ =149.4, 133.0, 129.8,<br />
129.7 (×2), 128.6 (×2), 128.4, 123.5, 49.2, 29.5 (×2), 15.0. HRMS (EI): C13H14ClN3,<br />
calcd 247.0876, found: 247.0874.<br />
5-(4-Methoxyphenyl)-1-octyl-1H-imidazol-2-amine (BS-199)<br />
H 2N<br />
N<br />
N<br />
C8H17 Yield: 56 %. 1 H NMR (300 MHz, CDCl3): δ = 7.25 (m, 2H), 6.95 (d, J = 8.7 Hz, 2H),<br />
6.60 (s, 1H), 3.97 (br s, 2H), 3.84 (s, 3H), 3.70 (t, J = 7.8 Hz, 2H), 1.56 (m, 2H), 1.17<br />
(m, 10H), 0.86 (t, J = 7.05 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =149.2, 131.1,<br />
129.5, 129.3 (×2), 128.8 (×2), 128.2, 123.4, 43.1, 31.6, 29.5, 29.0, 28.9, 26.4, 22.2,<br />
14.0. HRMS (EI): C18H27N3O, calcd 301.4265, found: 301.4271.<br />
5-(4-Fluorophenyl)-1-octyl-1H-imidazol-2-amine (BS-200)<br />
H 2N<br />
N<br />
N<br />
C8H17 Yield: 71 %. 1 H NMR (300 MHz, CDCl3): δ = 7.27 (m, 2H), 7.09 (m, 2H), 6.63 (s,<br />
1H), 3.96 (br s, 2H), 3.70 (t, J = 6.8 Hz, 2H), 1.56 (m, 2H), 1.17 (m, 10H), 0.86 (t, J =<br />
7.05 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =163.8, 160.5, 148.7, 130.2, 128.4,<br />
127.0, 122.9, 115.5, 104.7, 43.0, 31.6, 29.5, 29.0, 28.9, 26.4, 22.5, 14.0. HRMS (EI):<br />
C17H24FN3, calcd 289.3910, found: 289.3901.<br />
5-(3,4-Dichlorophenyl)-1-octyl-1H-imidazol-2-amine (BS-201)<br />
Cl<br />
O<br />
F
H 2N<br />
N<br />
N<br />
C8H17 Yield: 64 %. 1 H NMR (300 MHz, CDCl3): δ = 7.47 (d, J = 8.3 Hz, 1H), 7.40 (d, J =<br />
7.98 Hz, 1H), 7.16 (d of d, J = 2.0, 6.2 Hz, 1H), 6.71 (s, 1H), 4.05 (br s, 2H), 3.73 (t, J<br />
= 7.68 Hz, 2H), 1.59 (m, 2H), 1.19 (m, 10H), 0.86 (t, J = 7.05 Hz, 3H). 13 C NMR<br />
(75.5 MHz, CDCl3): δ =149.6, 132.8, 131.1, 131.0, 130.6, 129.5, 127.1, 127.0, 124.2,<br />
43.3, 31.6, 29.5, 29.0, 28.9, 26.4, 22.5, 14.0. HRMS (EI): C17H23Cl2N3, calcd<br />
340.2906, found: 240.2918.<br />
5-(3-Bromophenyl)-1-octyl-1H-imidazol-2-amine (BS-202)<br />
H 2N<br />
N<br />
N<br />
C8H17 Yield: 68 %. 1 H NMR (300 MHz, CDCl3): δ = 7.45 (m, 2H), 7.25 (m, 2H), 6.70 (s,<br />
1H), 4.02 (br s, 2H), 3.74 (t, J = 7.71 Hz, 2H), 1.59 (m, 2H), 1.19 (m, 10H), 0.86 (t, J<br />
= 6.08 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =149.2, 133.0, 130.8, 130.1 (×2),<br />
128.0, 126.5, 123.8, 122.6, 43.2, 31.6, 29.5, 29.0, 28.9, 26.4, 22.5, 14.0. HRMS (EI):<br />
C17H24BrN3, calcd 350.2966, found:250.2978.<br />
5-(Naphthalen-1-yl)-1-octyl-1H-imidazol-2-amine (BS-202)<br />
H 2N<br />
N<br />
N<br />
C8H17 Yield: 68 %. 1 H NMR (300 MHz, CDCl3): δ = 7.85 (m, 4H), 7.46 (m, 3H), 6.78 (s,<br />
1H), 4.04 (br s, 2H), 3.83 (t, J = 7.62 Hz, 2H), 1.62 (m, 2H), 1.15 (m, 10H), 0.82 (t, J<br />
= 6.99 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =149.1, 133.4, 132.4, 129.5, 128.3,<br />
128.2, 127.9, 127.7, 126.6, 126.4 (×2), 126.0, 123.0, 43.3, 31.6, 29.5, 29.0, 28.9, 26.4,<br />
22.5, 14.0. HRMS (EI): C21H27N3, calcd 321.4592, found: 321.4576.<br />
5-(4-Nitrophenyl)-1-octyl-1H-imidazol-2-amine (BS-204)<br />
H 2N<br />
N<br />
N<br />
C8H17 Cl<br />
Cl<br />
Br<br />
NO 2
Yield: 66%. 1 H NMR (300 MHz, CDCl3): δ = 8.27 (d, J = 8.7 Hz, 2H), 7.47 (t, J = 8.7<br />
Hz, 2H), 6.89 (s, 1H), 4.13 (br s, 2H), 3.82 (t, J = 7.8 Hz, 2H), 1.63 (m, 2H), 1.21 (m,<br />
10H), 0.85 (t, J = 6.96 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =163.8, 160.5,<br />
148.7, 130.2, 128.4, 127.0, 122.9, 115.5, 104.7, 43.0, 31.6, 29.5, 29.0, 28.9, 26.4,<br />
22.5, 14.0. HRMS (EI): C17H24N4O2, calcd 316.3981, found: 316.3993.<br />
5-(4'-Nitrobiphenyl-4-yl)-1-octyl-1H-imidazol-2-amine (BS-205)<br />
H 2N<br />
N<br />
N<br />
C8H17 Yield: 52 %. 1 H NMR (300 MHz, CDCl3): δ = 8.33 (m, 1H), 7.78-7.35 (m, 6H), 7.13<br />
(m 1H), 6.77 (s, 1H), 4.07 (br s, 2H), 3.79 (m, 2H), 1.63 (m, 2H), 1.19 (m, 10H), 0.84<br />
(m, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =163.8, 160.5, 148.7, 130.2, 128.4, 127.0,<br />
122.9, 115.5, 104.7, 43.0, 31.6, 29.5, 29.0, 28.9, 26.4, 22.5, 14.0. HRMS (EI):<br />
C23H28N4O2, calcd 392.4940, found:392.4928.<br />
NO 2<br />
5-(4-(Methylsulfonyl)phenyl)-1-octyl-1H-imidazol-2-amine (BS-206)<br />
H 2N<br />
N<br />
N<br />
C8H17 SO 2Me<br />
Yield: 61 %. 1 H NMR (300 MHz, CDCl3): δ = 7.97 (d, J = 8.1 Hz, 2H), 7.51 (d, J =<br />
7.98 Hz, 2H), 6.83 (s, 1H), 4.09 (br s, 2H), 3.82 (t, J = 7.68 Hz, 2H), 3.09 (s 3H), 1.62<br />
(m, 2H), 1.21 (m, 10H), 0.86 (t, J = 7.05 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ<br />
=150.7, 138.1, 136.6, 127.9 (×2), 127.6, 127.4 (×2), 126.0, 44.5, 43.6, 31.6, 29.6,<br />
29.0, 28.9, 26.5, 22.5, 14.0. HRMS (EI): C18H27N3O2S, calcd 349.4909, found:<br />
349.4920.<br />
5-(4-(Methylthio)phenyl)-1-octyl-1H-imidazol-2-amine (BS-207)<br />
H 2N<br />
N<br />
N<br />
C8H17 Yield: 40 %. 1 H NMR (300 MHz, CDCl3): δ = 7.33-7.22 (m, 4H), 6.65 (s, 1H), 4.00<br />
(br s, 2H), 3.73 (t, J = 7.98 Hz, 2H), 2.51 (s, 3H), 1.58 (m, 2H), 1.18 (m, 10H), 0.86<br />
(t, J = 6.99 Hz, 3H). 13 C NMR (75.5 MHz, CDCl3): δ =163.8, 160.5, 148.7, 130.2,<br />
SMe
128.4, 127.0, 122.9, 115.5, 104.7, 43.0, 31.6, 29.5, 29.0, 28.9, 26.4, 22.5, 14.0. HRMS<br />
(EI): C18H27N3S, calcd 317.4921, found: 317.4935.<br />
5-(Triphenyl-4-yl)-1-octyl-1H-imidazol-2-amine (BS-208)<br />
H 2N<br />
N<br />
N<br />
C8H17 Yield: 31 %. 1 H NMR (300 MHz, CDCl3): δ = 7.70-7.64 (m, 7H), 7.46-7.40 (m 5H),<br />
6.74 (s, 1H), 4.03 (br s, 2H), 3.80 (m, 2H), 1.63 (m, 2H), 1.20 (m, 10H), 0.86 (m, 3H).<br />
13<br />
C NMR (75.5 MHz, CDCl3): δ =148.9, 140.5, 140.2, 139.2 (×2), 130.0, 129.2, 128.8<br />
(×2), 128.5, 127.5 (×2), 127.4, 127.3, 127.2 (×4), 127.0, 126.9, 123.1, 43.2, 31.7,<br />
29.6, 29.0, 28.9, 26.5, 22.5, 14.0. HRMS (EI): C29H33N3, calcd 423.5924, found:<br />
423.5941.
3.10 Representative NMR spectra<br />
3.10.1 1 H and 13 C NMR spectra of bs-063<br />
Integral<br />
7.4263<br />
7.3999<br />
7.3780<br />
7.3252<br />
7.3171<br />
7.3102<br />
7.2625<br />
8.0<br />
152.6248<br />
150<br />
7.5<br />
4.9005<br />
7.0<br />
134.6350<br />
132.9477<br />
132.1549<br />
131.8022<br />
130.7185<br />
140<br />
6.6762<br />
0.9360<br />
130<br />
6.5<br />
126.4311<br />
H 2N<br />
120<br />
H 2N<br />
6.0<br />
N<br />
N<br />
N<br />
C9H19 5.5<br />
N<br />
C9H19 110<br />
100<br />
5.0<br />
90<br />
4.5<br />
3.9905<br />
3.7821<br />
3.7570<br />
3.7312<br />
1.4513<br />
81.0402<br />
80.6220<br />
80.2038<br />
4.0<br />
(ppm)<br />
80<br />
(ppm)<br />
2.1067<br />
3.5<br />
70<br />
3.0<br />
60<br />
2.5<br />
50<br />
46.6571<br />
2.0<br />
40<br />
1.6110<br />
1.5890<br />
1.5658<br />
1.9669<br />
1.5<br />
12.326<br />
1.0<br />
35.3221<br />
33.0857<br />
32.8639<br />
32.6638<br />
32.5038<br />
30.0128<br />
26.1509<br />
30<br />
0.8917<br />
0.8691<br />
0.8465<br />
3.0000<br />
20<br />
17.6160<br />
0.5<br />
10<br />
-0.0002<br />
0.0<br />
0
3.10.2 1 H and 13 C NMR spectra of bs-125<br />
Integral<br />
9.0<br />
160<br />
8.5<br />
149.1738<br />
150<br />
8.0<br />
7.3853<br />
7.3570<br />
7.2629<br />
7.2334<br />
2.0207<br />
2.6488<br />
7.5<br />
7.0<br />
6.6722<br />
N<br />
H2N N<br />
C12H25 0.9125<br />
133.1114<br />
129.5949<br />
129.3876<br />
128.8857<br />
128.2966<br />
123.6310<br />
140<br />
130<br />
6.5<br />
6.0<br />
5.5<br />
N<br />
H2N N<br />
C12H25 120<br />
110<br />
100<br />
5.0<br />
Cl<br />
Cl<br />
3.9909<br />
3.7536<br />
3.7285<br />
3.7028<br />
1.4687<br />
1.9926<br />
4.5 4.0<br />
(ppm)<br />
77.4765<br />
77.0510<br />
76.6292<br />
90 80<br />
(ppm)<br />
70<br />
3.5<br />
3.0<br />
60<br />
2.5<br />
50<br />
2.0<br />
43.1952<br />
40<br />
1.5750<br />
1.9595<br />
1.5<br />
1.2492<br />
1.1802<br />
0.9021<br />
0.8808<br />
0.8576<br />
18.169<br />
3.0000<br />
1.0<br />
0.5<br />
31.9039<br />
29.6019<br />
29.4965<br />
29.4019<br />
29.3292<br />
28.9983<br />
26.4927<br />
22.6890<br />
14.1359<br />
30<br />
20<br />
10<br />
0.0002<br />
0.0<br />
0.0008<br />
0
3.11 References<br />
[1] (a) Alvi K. A, Peters B. M, Hunter L. M, Crews P. (1993) Tetrahedron. 49,329. (b) Chan G.<br />
W, Mong S, Hemling M. E, Freyer A. J, Offen P. H, DeBrosse C. W, Sarau H. M, Westley J.<br />
W. (1993) J. Nat. Prod. 56, 116. (c) Tsuda M, Shigemori H, Ishibashi M, Kobayashi J. (1992)<br />
Tetrahedron Lett. 33, 2597. (d) Ishibashi M, Tsuda M, Ohizumi Y, Sasaki T, Kobayashi<br />
(1991) J. Ezperientia, 47, 299. (e) Kobayashi J, Tsuda M, Ohizumi Y. (1991) Experientia 47,<br />
301. (f) Keifer P. A, Schwartz R. E, Koker M. E. S, Hughes R. J, Rittschof D, Rinehart K. L.<br />
(1991) J. Org. Chem. 56, 2965. (g) Morales J. J, Rodriguez A. D. (1991) J. Nat. Prod. 54,<br />
629. (h) Alvi K. A, Crews P, Loughhead D. G. (1991) J. Nat. Prod. 54, 1509. (i) Wright A. E,<br />
Chiles S, Cross S. (1991) J. Nat. Prod. 54, 1684. (j) Kobayashi J, Tsuda M, Murayama T,<br />
Nakamura H, Ohizumi Y, Ishibashi M, Iwamura M, Ohta T, Nozoe S. (1990) Tetrahedron<br />
46, 5579. (k) Bedoya-Zurita M, Ahond A Poupat C, Potier P. (1989) Tetrahedron 45, 6713.<br />
(l) Walker R. P, Faulkner D. J, Van Engen D, Clardy J. (1981) J. Am. Chem. SOC. 103,<br />
6772.<br />
[2] (a) Nagai W, Kirk K. L, Cohen L. A. (1973) J. Org. Chem. 38, 971. (b) Dismukes K, Rogers<br />
M, Daily J. W. (1976) J. Neurochem. 26, 785. (c) Lipinski C. A, LaMattina J. L, Hohnke L.<br />
A. (1986) J. Med. Chem. 28, 1628. (d) Impicciatore M, Morini G, Chiavarini M, Plazzi P. V,<br />
Bordi F, Vitali F. (1986) Agents Actions 18, 134. (e) Haaksma J, DonnB-Op den Kelder M,<br />
Timmerman H, Weinstein H, (1991) In New Perspectives in Histamine Research;<br />
BirkhEiuser Verlag: Basel, 315-324.<br />
[3] See Ann. Drug Data Rep. 1993,15, 513.<br />
[4] Jung F, Boucherot D, Delvare C, Olivier A, Davies G. M, Betts M. J, Brown R, Stevenson R,<br />
Joseph M, Kingston F, Pittam, (1993) J. Antibiot. 46, 992.<br />
[5] (a) Beaman A. G, Tautz W, Gabriel T, Duschinsky R. (1966) J. Am. Chem. SOC. 87, 389.<br />
(b) Lancini C, Lazzari E, Arioli V, Bellani P. (1969) J. Med. Chem. 12, 775.<br />
[6] For example see: Jenkins C, Naylor A, O'Neill, Threadgill D, Cole S, Stratford J, Adams<br />
G. E, Fielden M, Suto J, Stier A. J. Med. Chem. lSW, 33, 2603. Adams E, Stratford J.<br />
(1986) Biochem. Pharm. 35, 71.<br />
[7] Storey B. T, Sullivan W. W, Moyer C. L. (1986) J. Org. Chem. 29, 3118.<br />
[8] Lawson, A. (1956) J. Chem. SOC. 307.<br />
[9] (a) Lancini G. C, Lazzari E. (1966) J. Heterocycl. Chem. 3, 1 (b) Cavalleri B, Ballotta R,<br />
Lancini G. C. (1979) J. Heterocycl. Chem. 979.<br />
[10] See: Porter A. E. A. (1984) In Comprehensive Heterocyclic Chemistr Pyrazines and Their<br />
Benzo Derivatives; Boulton A. J, McKillop A Eds.; Pergamon Press: New York. 3, 184-185.<br />
[11] Fargher R. G, Pyman F. L. (1919) J. Chem. SOC. 217.<br />
[12] Kirk K. L. (1978) J. Org. Chem. 43, 4381.<br />
[13] Kreutzberger A. (1962) J. Org. Chem. 27, 886.<br />
[14] Nishimura T, Kitajima K. (1979) J. Org. Chem. 44, 818.
[15] Takahashi K, Kirk K. L, Cohen L. A. J. Org. Chem. 1984, 49, 1951. Jarosinski M. A,<br />
Anderson K. (1991) J. Org. Chem. 56, 4058.<br />
[16] (a) Ruccia M, Vivona N, Cusmano G. (1974) Tetrahedron 30, 3859. (b) Braun M, Buchi G,<br />
Bushey F. (1978) J. Am. Chem. SOC. 100, 4208. (c) Sehgal K, Agrawal C. (1982) J. Pharm.<br />
Sci. 71, 1203. (d) Berry A, Gilbertsen B, Cook D. (1986) J. Med. Chem. 29, 2034.<br />
[17] LaMattina L, Mularski C. J. (1984) Tetrahedron Lett. 25, 2957.<br />
[18] Xu Y, Yakushijin K, Horne A. (1993) Tetrahedron Lett. 34, 6981
Copper Catalyzed Microwave Assisted One Pot<br />
Synthesis of 2-Aminoimidazole-Triazole<br />
Framework via Dimorth Rearrangement and<br />
Click Reaction
Chapter-4<br />
Copper Catalyzed Microwave Assisted One Pot<br />
Synthesis of 2-Aminoimidazole-Triazole Framework<br />
via Dimorth Rearrangement and Click Reaction.<br />
Br<br />
R 2<br />
N<br />
N<br />
n<br />
N<br />
OH<br />
R 1<br />
n = 1,2<br />
N 3<br />
ABSTRACT<br />
One-pot Microwave-Assisted Synthesis<br />
Cu(OAc) 2 (5 mol %)<br />
N 2H 4 (2 equiv)<br />
R 3<br />
(1.2 equiv)<br />
MW, 100 o C, 2-5 min<br />
R 2<br />
N<br />
NH<br />
N<br />
H<br />
22 examples,<br />
upto 90% yield<br />
R 1<br />
N<br />
N<br />
n<br />
N<br />
R3 A microwave assisted one-pot Cu(II)-catalyzed protocol was developed for the<br />
construction of 2-AI-T framework. This process combining two consecutive steps of<br />
dimorth rearrangement and click reaction represents a useful protocol for the smooth<br />
synthesis of novel 2-aminoimidazole-triazole derivatives.<br />
Publication<br />
[1] Copper Catalyzed Microwave Assisted One Pot Synthesis of 2-<br />
Aminoimidazole-Triazole Framework Org.lett (manuscript in preparation)
4.1 Introduction<br />
There are only a few approaches that describe the direct synthesis of 2aminoimidazoles<br />
and their biological activity 1-5 . The earliest method involves<br />
condensation of α-aminocarbonyl compounds with cyanamide or their synthetic<br />
equivalents 6,7 . This method is most commonly used for the direct construction of the<br />
2-aminoimidazole ring. Other general applicable strategies are cyclocondensation of<br />
α-bromoketone with N-acetylguanidine in acetonitrile 8 , iminophosphorane-mediated<br />
cyclization of α –azido esters 9 , ammonolysis of 2-amino-1,3-oxazol-3-iumsalts 10 ,<br />
sequential functionalization of 1,2-diprotected imidazole ring with different<br />
electrophiles 11 . Most of them involve long experimental procedures, the use of<br />
unstable precursors and tiresome workup process. Accordingly, the development of<br />
straightforward and general procedures for the synthesis of diversely substituted 2aminoimidazoles<br />
from readily available precursors is highly warranted. Herein, we<br />
report a rapid and highly efficient Cu-mediated synthesis of 2-aminoimidazoletriazole<br />
framework via click reaction and dimorth rearrangement.<br />
“Click chemistry” has emerged as a fast and efficient approach to synthesis of novel<br />
compounds with desired function making use of selected “near perfect” reactions. 12<br />
(very fast, selective, high-yield, and wide scope).<br />
The Dimroth rearrangement 13 is an isomerization of heterocycles that consists in a<br />
translocation of endo- or exocyclic heteroatoms through a ring-opening-ring-closure<br />
sequence. It can be catalyzed by acids, bases, heat or light.<br />
Recently group of Erik 14 reported a new one pot microwave assisted synthesis of<br />
substituted 2-amino-1H- imidazoles from readily available 2-aminopyrimidine (1) and<br />
α-bromoketone (2). The first step was performed by heating N-(3azidopropyl)pyrimidin-2-amine<br />
(1) and 2-bromo-1-phenylethanone (2) at 75 o C for 3<br />
h resulting in the formation of hydroxyl salt (3) which undergoes dimorth type<br />
rearrangement by 7 equiv of NH2NH2.H2O resulting in the formation of N-(2-azido)-<br />
1H-imidazol-2-amine. Final step of click reaction was performed under microwaveirradiation<br />
using phenylacetylene (1.5.equiv), Cu(Oac)2 (10 mol %)as catalyst at 100<br />
o<br />
C 10 min with a maximum power of 40W to obtain 2-AI-T scaffold (5). (Scheme 1)
N<br />
N<br />
Br<br />
R 2<br />
N<br />
N<br />
3<br />
N<br />
H<br />
N<br />
OH<br />
R1 N 3<br />
n<br />
MeCN, 75 o C,<br />
3 Hrs<br />
N<br />
n 3<br />
+<br />
R 2<br />
1 2<br />
Br<br />
O<br />
R 1<br />
One Pot MW ?<br />
o MW. 100 C<br />
MeCN, 10 min<br />
N2H4 (7 equiv)<br />
Scheme-1 Sequential Synthesis of 2-AI-T Framework<br />
R 2<br />
R 1<br />
R 2<br />
R 1<br />
N<br />
N<br />
H<br />
H<br />
N<br />
N<br />
NH<br />
N<br />
N R3 N<br />
n<br />
MW. 100 o C<br />
Cu(OAc) 2<br />
10 min, 80 %<br />
In continuation of earlier work on two step synthesis of 2-AI-T scaffold with excellent<br />
yield. now an ameliorated and convenient one-pot protocol for the synthesis of 2-AI-T<br />
scaffold under microwave conditions has been reported.<br />
4.2 Optimization Study<br />
Looking to the current exploration in the synthesis and microwave-assisted decoration<br />
of the 2-aminoimidazole 14 and click reaction 15 and preliminary success of the<br />
sequence, it was very interesting to investigate whether one-pot protocol for the<br />
construction of 2-AI-T scaffold should be possible. The test reaction was performed<br />
with hydroxy salt {3} and phenyl acetylene as a model system. Different Cu catalyst,<br />
equiv of NH2NH2.H2O, temperature and reaction time were screened to derive an<br />
optimized protocol (Table 1).<br />
First, the application of Cu(OAc)2 as catalyst for click reaction and different<br />
equivalents of aqueous NH2NH2.H2O for simultaneous dimorth rearrangement (Table-<br />
1, No-1-3) was evaluated. However in case of 1 equiv. of hydrazine used, yield was<br />
only 51 %. (Table-1, No-1). Next study of different reaction time (Table-1, No-3-7)<br />
performed. It was observed that reaction could complete even in very short time<br />
4<br />
NH<br />
5<br />
R 3<br />
N 3<br />
n
(Table-1, No- 6). Next reaction temperature (Table-1, No-8-9) was investigated.<br />
Decrease of the reaction temperature resulted in lover yield (Table-1, No-9). Then the<br />
examination the catalyst effect on a reaction (Table-1, No-7-13) was done. However<br />
replacement of Cu(Oac)2 with CuSO4 resulted in lower yield (Table-1, No-11). While<br />
in case of Cu Powder (200 mesh) used only traces amount of desire product observed<br />
(Table-1, No-13). Moreover it was observed that the catalyst was mandatory for<br />
successfully performing the reaction, as no product was formed in the absence of the<br />
catalyst (Table-1, No-12). Finally optimum reaction conditions were achieved when a<br />
mixture of hydroxy salt, 1.2 equiv of phenyl acetylene, 5 mol % of Cu(Oac)2 in 1 ml<br />
of Ethenol : water (4: 1) was irradiated for 2 min at a ceiling temperature of 100 o C<br />
applying a maximum power of 36 W, affording the desired compound in 90 % yield<br />
(Table 1 No-8). The protocol was checked with conventional condition providing<br />
lower yield of 24 % of after 24 hrs.<br />
N<br />
N N<br />
Ph OH<br />
N3 One-Pot microwave-assisted<br />
Cu salt (mol %)<br />
Br<br />
3<br />
N2H4 (equiv.)<br />
Ph (1.2 equiv.)<br />
EtOH : Water (4:1, 1ml)<br />
Ph<br />
No.<br />
time<br />
(min)<br />
N<br />
N<br />
H<br />
NH<br />
5<br />
N N<br />
N<br />
temp ( o C) Cu salt (mol %) yield (%) b<br />
1 c 20 100 °C Cu(Oac)2, 10 51<br />
2 d 20 100 °C Cu(Oac)2, 10 84<br />
3 20 100 °C Cu(Oac)2, 10 86<br />
4 10 100 °C Cu(Oac)2, 10 80<br />
5 5 100 °C Cu(Oac)2, 10 90<br />
6 2 100 °C Cu(Oac)2, 10 90<br />
7 1 100 °C Cu(Oac)2, 10 53<br />
8 2 100 °C Cu(Oac)2, 5 90<br />
9 2 90 °C Cu(Oac)2, 5 73<br />
10 2 100 °C Cu(Oac)2, 2 57<br />
11 2 100 °C CuSO4.5H2O, 5 67<br />
Ph
12 2 100 °C - -<br />
13 2 100 °C Cu Powder (200 mesh) Traces<br />
14 e - f 25 °C Cu(Oac)2, 5 24<br />
a<br />
All reactions were run on a 0.7 mmol scale of 3, applying phenyl acetylene (1.2<br />
equiv) in ethanol: water (4:1, 1 mL) under microwave irradiation. The mixture was<br />
irradiated in a sealed tube (CEM Discover @ ) at a ceiling temperature of 100 o C and 35<br />
W maximum power for the stipulated time. b isolated yields. c 1.0 equiv of<br />
NH2NH2.H2O used. d 5.0 equiv of NH2NH2.H2O used. e reaction carried out at room<br />
temperature. f time 24 h.<br />
Table-1: Copper Catalyzed One-Pot protocol: Catalyst, equiv of hydrazine, reaction<br />
time and Temperature Effects on the model reaction to obtain 2-AI-T scaffold a .<br />
4.3 Results and Discussion<br />
Encouraged by these findings, the scope of this protocol was further explored. An<br />
array of hydroxy salts 3 (a-j) (Table-2) were reacted with various acetylene using our<br />
optimized conditions. In most cases, the reactions proceeded well affording the one<br />
pot product in good to excellent yield (Table-2)<br />
R 2<br />
N<br />
1<br />
+<br />
N<br />
Br<br />
2<br />
N<br />
H<br />
O<br />
R 1<br />
N 3<br />
n<br />
MeCN, 75 o C,<br />
3 Hrs<br />
R 3<br />
N N<br />
n<br />
3<br />
N<br />
Br N<br />
R OH<br />
2 R1 Cu(OAc) 2 (5 mol. %)<br />
MW. 100 o N2H4 C<br />
3 {a-j}<br />
2-5 min, 85-90 %<br />
One-pot Microwave-assisted<br />
R 2<br />
R 1<br />
N<br />
N<br />
H<br />
NH<br />
N<br />
N R3 N<br />
n<br />
4 {a-v}
No. Product, Yield b (%) No. Product, Yield b (%)<br />
1<br />
2<br />
3<br />
4<br />
5<br />
6<br />
7<br />
8<br />
9<br />
Cl<br />
Br<br />
Br<br />
Br<br />
Cl<br />
Br<br />
Br<br />
Cl<br />
Cl<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N H<br />
N<br />
N<br />
H<br />
N H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
H<br />
N<br />
N<br />
N<br />
4-a (66)<br />
N<br />
N<br />
N<br />
N<br />
H<br />
N<br />
N<br />
N<br />
4-c (73)<br />
N<br />
N<br />
N<br />
N<br />
N<br />
H<br />
N<br />
H<br />
4-e (73)<br />
NH<br />
4-f (80)<br />
N<br />
H<br />
N<br />
N<br />
N<br />
4-g (80)<br />
NH<br />
NH<br />
N N<br />
N<br />
OMe<br />
4-b (84)<br />
Bu<br />
Me<br />
4-d (64)<br />
N<br />
N Hep<br />
N<br />
N N<br />
N<br />
N N<br />
N<br />
H 2N<br />
H<br />
N<br />
Pen<br />
Hep<br />
4-h (81)<br />
4-I (75)<br />
12<br />
12<br />
14<br />
15<br />
16<br />
17<br />
18<br />
19<br />
20<br />
Cl<br />
N<br />
N<br />
H<br />
NH<br />
N N<br />
N<br />
Cl 4-l (90)<br />
N<br />
N<br />
H<br />
N H<br />
N<br />
N<br />
N<br />
Br 4-m (95)<br />
O<br />
Br<br />
N<br />
N<br />
N<br />
H<br />
NH<br />
N<br />
N<br />
H<br />
NH<br />
4-n (74)<br />
N N<br />
N<br />
N N<br />
N<br />
O 4-o (29)<br />
O<br />
N<br />
N<br />
N<br />
H<br />
N<br />
H<br />
N<br />
N<br />
N<br />
O 4-p (29)<br />
N<br />
N<br />
H<br />
N H<br />
N<br />
N<br />
N<br />
F 4-q (68)<br />
N<br />
N<br />
H<br />
N H<br />
N<br />
N<br />
N<br />
F 4-r (80)<br />
N<br />
N<br />
H<br />
N H<br />
N<br />
N<br />
N<br />
Cl 4-s (16)<br />
Cl<br />
Cl<br />
N<br />
N<br />
H<br />
NH<br />
4-t (85)<br />
N N<br />
N
10<br />
11<br />
Cl<br />
Cl<br />
N<br />
N<br />
H<br />
N<br />
H<br />
N<br />
N<br />
N<br />
Cl 4-j (85)<br />
N<br />
N<br />
H<br />
N<br />
H<br />
N<br />
N<br />
N<br />
Cl 4-k (80)<br />
21<br />
22<br />
Cl<br />
Cl<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
NH<br />
N H<br />
N N<br />
N<br />
N<br />
N<br />
N<br />
S<br />
4-u (91)<br />
Br 4-v (80)<br />
a<br />
All reactions were run on a 0.7 mmol scale of 3 {a-j} ethanol: water (4:1) (1 ml) with<br />
phenyl acetylene (1.2 equiv), Cu(OAc)2 (5 mol % ) and hydrazine hydride (2 equiv).<br />
The mixture was irradiated in a sealed tube (CEM Discover @ ) at a ceiling temperature<br />
of 100 o C and 35 maximum power for the stipulated time. b isolated yields. Yields are<br />
shown in ().<br />
Table-2: Microwave assisted one pot decoration of 2-AI-T Framework a .<br />
A diverse set of 2-AI-T scaffold were synthesized with these optimized conditions.<br />
Ten different hydroxy salt 3 {a-j} (n = 1 or 2) were reacted with different (hetero)<br />
aromatic or alkyl acetylenes (Table-2) to test the generality of this new microwaveassisted<br />
one pot method (Table 2). All reactions were completed within 5 min using<br />
microwave irradiation at ceiling temperature of 100 o C and 35W power. The yields<br />
varied from good to excellent, although in some cases lower yields were observed<br />
(Table 2, No-15,16 and 19). However in case of morpholine substitution (table-2, No-<br />
15-16) probably due to decomposition of starting hydroxy salt 3 {h} lower yields<br />
were observed. Interestingly when 4,5-disubstituted hydroxy salt react with acetylene<br />
only 16% of desired product 4{s} was observed due to steric hindrance of 4-Mephenyl<br />
substitution on dimorth rearrangement. Motivated by the importance of the<br />
final target to develop new general method toward widely functionalized 2-AI-T<br />
framework, we next examined the extension of this procedure to other acetylene. The<br />
reaction proceeded effectively with aliphatic and aromatic terminal acetylenes to give<br />
the corresponding 2-AI-T (Table 2). Thus, a variety of substituted 2-AI-T containing<br />
aromatic, aliphatic, cyclic and heterocyclic substitution at the C-4 position of the<br />
triazole ring were obtained.
4.4 Possible Mechanism<br />
Regarding the mechanism of transformation of 2-hydroxy 2,3-dihydro-1Himidazo[1,2-a]pyrimidin-4-ium<br />
salts 3 into 2-amino-1H-imidazole-triazole 4, we<br />
presume that the reaction proceeds via an unusual Dimroth type rearrangement<br />
(Scheme-3).<br />
Br<br />
Br<br />
R 2<br />
N<br />
NH 2NH 2<br />
R 2<br />
N<br />
N<br />
N<br />
N3 n<br />
R2 N<br />
H<br />
N<br />
OH<br />
R1 N<br />
H<br />
3<br />
N<br />
R 1<br />
Ring Opening<br />
N<br />
R 1<br />
OH<br />
25 o C<br />
n<br />
N 3<br />
NH 2NH 2<br />
MW<br />
R 2<br />
N<br />
Cu(OAc) 2<br />
CuNP<br />
NH 2<br />
N<br />
N<br />
H ·HBr<br />
a b<br />
N<br />
R 1<br />
OH<br />
Generation of<br />
"nano-Cu"<br />
R 3 "Click" Reaction<br />
N<br />
n<br />
N<br />
N<br />
R 3<br />
Dimroth Rearrangement<br />
Scheme-3: Proposed mechanism for One-pot reaction:<br />
In the first step the 2-hydroxy-2,3-dihydroimidazo[1,2-a]pyrimidinium salt (3)<br />
undergoes cleavage of the pyrimidine ring (a), resulting in the generation of pyrazole<br />
and 2-amino-5-hydroxyimidazolidine (b), meanwhile copper nanoparticle 16 generated<br />
by reduction of Cu(OAc)2 using 1 equiv of NH2NH2.H2O takes part in click reaction.<br />
This intermediate (b), which is in equilibrium with the open form c can cyclize again<br />
leading by dehydration upon microwave irradiation, results in the rearranged 2amino-1H-imidazoles<br />
triazole (4).<br />
R 2<br />
HN<br />
R 1<br />
NH 2<br />
O<br />
N<br />
H 2O<br />
N<br />
N<br />
n<br />
N<br />
n<br />
c<br />
4<br />
N<br />
N<br />
N<br />
R 3<br />
R 3
4.5 Conclusion<br />
In conclusion microwave-assisted Cu-catalyzed one pot protocol for the synthesis of<br />
2-aminoimidazole-triazole framework via two consecutive steps of dimorth<br />
rearrangement and click reaction was demonstrated. Library of 22 compounds have<br />
been synthesized and were subjected to test for antibiofilm activity. However the<br />
antibiofilm activities of these classes of compounds are under pipeline.<br />
4.6 Experimental<br />
4.6.1 General Methods<br />
All chemical reagents were used without further purification. Solvents for column<br />
chromatography and TLC were laboratory grade and distilled before use. For thinlayer<br />
chromatography (TLC), analytical TLC plates (Alugram SIL G/UV254 (E. M.<br />
Merk) were used. Column chromatography was performed with flash silica gel (100-<br />
200 mesh) or neutral alumina oxide (50-200 micron). 1 H and 13 C NMR spectra were<br />
recorded on a Bruker Avance 300 (300 MHz) or a Bruker AMX-400 (400 MHz)<br />
spectrometers. NMR samples were run in the indicated solvents and were referenced<br />
internally. Chemical shift values were quoted in ppm and coupling constants were<br />
quoted in Hz. Chemical shift multiplicities were reported as s = singlet, d = doublet, t<br />
= triplet, q = quartet, m = multiplet and br = broad. Low-resolution mass spectra were<br />
recorded on a HEWLETT-PACKARD instrument (CI or EI) and LCQ Advantage<br />
instrument (ESI). High-resolution mass spectra (EI) were recorded on a KRATOS<br />
MS50TC instrument. Melting points were determined using Reichert-Jung Thermovar<br />
apparatus and were uncorrected.<br />
4.6.2 Microwave Irradiation Experiments<br />
Microwave irradiation experiments were carried out in a dedicated CEM-Discover<br />
mono-mode microwave apparatus or Microwave apparatuses were used in the<br />
standard configuration as delivered, operating at a frequency 2.45 GHz with<br />
continuous irradiation power from 0 to 400 W. The reactions were carried out in 10,<br />
20, 30 and 50 mL glass tubes. The temperature was measured with an IR sensor on<br />
the outer surface of the process vial or fibre optic sensor inside the process vial. After<br />
the irradiation period, the reaction vessel was cooled rapidly (2-5 min) to ambient<br />
temperature by air jet cooling.
4.7 Experimental protocols<br />
4.7.1 General Procedure for the Preparation 3-Azido-propylamine<br />
To a solution of 3-chloropropan-1-amine hydrochloride (3.2 g, 14.6 mmol) in water<br />
(10 mL) was slowly added NaN3 (3.2 g, 49.2 mmol) as a solution in water (15 mL).<br />
The resulting solution was allowed to stir at reflux overnight. After cooling to room<br />
temperature, about 2/3 of the water was removed by evaporation and the remaining<br />
residue diluted with ether (50 mL). This biphasic mixture was cooled to 0 °C and<br />
KOH pellets (4.0 g) were slowly added. The phases separated and the aqueous layer<br />
extracted with ether (2 x 30 mL). All organics combined, dried over Na2SO4, and<br />
concentrated to afford 3-Azido-propylamine (1.17 g, 80%) as yellow oil<br />
4.7.2 General Procedure for the Preparation of N-(3-azidopropyl)pyrimidin-2amine:<br />
In a 50 mL microwave vial were successively dissolved in EtOH (20 mL) 2chloropyrimidine<br />
(3.43 g, 30 mmol), 3-Azido-propylamine (48 mmol, 1.6 equiv) and<br />
triethylamine (6.2 mL, 45 mmol, 1.5 equiv). The reaction tube was sealed, and<br />
irradiated in the cavity of a Milestone MicroSYNTH microwave reactor at a ceiling<br />
temperature of 120 °C at 100 W maximum power for 60 min. After the reaction<br />
mixture was cooled with an air flow for 15 min, it was diluted with water (100 mL),<br />
extracted with DCM (2×150 mL) and dried over Na2SO4. The solvent was evaporated<br />
in vaccuo, and the crude mixture was purified by silica gel flash chromatography<br />
using 0-5% MeOH−DCM as the eluent.<br />
4.7.3 General Procedure for the Preparation of Salts.<br />
To a solution of N-(3-azidopropyl)pyrimidin-2-amine (6 mmol) and αbromoacetophenone<br />
(7.2 mmol, 1.2 equiv) in acetonitrile (12 mL) was added 4dimethylaminopyridine<br />
(6 mg, 0.05 mmol). After being stirred at 85 °C for 5 h, the<br />
reaction mixture was diluted with acetone (20 mL) and the precipitate was filtered and<br />
washed with acetone (2×20 mL), ether (2×20 mL) and dried over P2O5 to give salt as<br />
a white solid.
4.7.4 General Procedure for the preparation of 2-AI-T.<br />
Cool the suspension of hydrazine hydride (2 equiv), in ethanol (0.8 ml.). To the<br />
suspension were added Cu(OAc)2 (5 mol %) in water (0.2 ml). and stirred it for 2 min<br />
at 0 o C. To this were added acetylene (1.5 eq) and hydroxyl salt (1 eq.) The reaction<br />
mixture was irradiated at 100 0 o C at the maximum power 35 W for 2-5 min. After<br />
completion of the reaction, the solvent was removed under reduce pressure. The crude<br />
product was purifier by column chromatography over silica gel using DCM /<br />
methanol / 7N methanolic NH3 (96:3:1) as the eluent.<br />
4.8 Spectral Characterization<br />
2-Azidoethanamine (BS-167)<br />
H 2N<br />
Yield: 41 %. 1 H NMR (300 MHz, CDCl3): δ = 3.37 (t, J = 5.61 Hz, 2H), 2.88 (t, J =<br />
5.50 Hz, 2H), 1.53 (Br s, 2H).<br />
3-Azidopropan-1-amine (BS-220)<br />
H 2N<br />
Yield: 45 %. 1 H NMR (300 MHz, CDCl3): δ = 3.38 (t, J = 6.93 Hz, 2H), 2.81 (t, J =<br />
6.84 Hz, 2H), 1.73 (m, 2H), 1.36 (Br s, 2H).<br />
N-(2-Azidoethyl)pyrimidin-2-amine (BS-168)<br />
N<br />
N<br />
N<br />
H<br />
Yield: 67 %. 1 H NMR (300 MHz, CDCl3): δ = 8.30 (d, J = 4.74 Hz, 2H), 6.58 (t, J =<br />
4.74 Hz, 1H), 5.44 (Br s, 1H), 3.64 (m, 2H), 3.54 (t, J = 5.58 Hz, 2H), 13 C NMR<br />
(75.5 MHz, CDCl3): δ =162.0, 158.1, 158.0, 111.1, 50.8, 40.7. HRMS (EI) C6H6N6,<br />
calcd 164.0810, found :.<br />
N-(3-Azidopropyl)pyrimidin-2-amine (BS-221)<br />
N<br />
N<br />
N<br />
H<br />
N 3<br />
N 3<br />
N 3<br />
N 3
Yield: 69 %. 1 H NMR (300 MHz, CDCl3): δ = 8.28 (d, J = 4.80 Hz, 2H), 6.54 (t, J =<br />
4.80 Hz, 1H), 5.30 (Br s, 1H), 3.52 (m, 2H), 3.42 (t, J = 6.57 Hz, 2H), 1.90 (m, 2H).<br />
1-(3-Azidopropyl)-2-hydroxy-2-phenyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-<br />
4-ium bromide (BS-230)<br />
N<br />
Br<br />
N<br />
N<br />
OH<br />
Yield: 72 %. 1 H NMR (300 MHz, DMSO-d6) : δ = 9.05 (m, 2H), 7.93 (s, 1H), 7.80<br />
(m, 2H), 7.48 (m, 3H), 7.37 (t, J = 4.86 Hz, 1H), 4.95 (m, 2H), 3.41 (m, 4H), 1.64 (m,<br />
2H). 13 C NMR (75.5 MHz, DMSO-d6): δ = 167.4, 154.6, 148.2, 138.1, 129.3, 128.4<br />
(×2), 126.9 (×2), 111.4, 90.6, 62.7, 47.9, 38.2, 27.0.<br />
1-(2-Azidoethyl)-2-hydroxy-2-phenyl-2,3-dihydro-1H-imidazo[1,2-a]pyrimidin-4ium<br />
bromide (BS-227)<br />
N<br />
Br<br />
N<br />
N<br />
OH<br />
Yield: 75 %. 1 H NMR (300 MHz, DMSO-d6) : δ = 9.02 (m, 2H), 7.99 (s, 1H), 7.80<br />
(m, 2H), 7.49 (m, 3H), 7.41 (t, J = 4.92 Hz, 1H), 4.95 (m, 2H), 3.38 (m, 4H). 13 C<br />
NMR (75.5 MHz, DMSO-d6): δ = 167.5, 154.7, 148.4, 137.8, 129.4, 128.4 (×2), 126.9<br />
(×2), 111.8, 90.6, 62.8, 48.1 (×2).<br />
1-(2-Azidoethyl)-2-hydroxy-2-(naphthalen-1-yl)-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-271)<br />
N<br />
Br<br />
N<br />
N<br />
OH<br />
N 3<br />
N 3<br />
N 3
Yield: 67 %. 1 H NMR (300 MHz, DMSO-d6) : δ = 9.10 (m, 2H), 8.38 (s, 1H), 8.16<br />
(s, 1H), 8.02 (m, 3H), 7.88 (m, 1H), 7.59 (m, 2H), 7.44 (m, 1H), 5.05 (s, 2H), 3.42 (m,<br />
4H). 13 C NMR (75.5 MHz, DMSO-d6): δ = 167.5, 154.9, 148.5, 135.0, 132.9, 132.1,<br />
128.4, 128.2, 127.5, 127.1, 126.7 (×2), 124.1, 111.9, 90.8, 62.6, 48.2 (×2).<br />
1-(3-Azidopropyl)-2-(4-bromophenyl)-2-hydroxy-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-272)<br />
N<br />
Br<br />
N<br />
N<br />
OH<br />
Yield: 76 %. 1 H NMR (300 MHz, DMSO-d6) : δ = 9.06 (d of d, J = 1.62, 4.60 Hz,<br />
1H), 8.98 (d of d, J = 1.62, 6.24 Hz,1H) 8.00 (s, 1H), 7.72 (m, 4H), 7.37 (m, 1H),<br />
4.85 (m, 2H), 3.37 (m, 4H), 1.66 (m, 2H). 13 C NMR (75.5 MHz, DMSO-d6): δ =<br />
167.5, 154.7, 148.2, 137.6, 131.4(×2), 129.3 (×2), 122.9, 111.5, 90.3, 62.5, 47.9, 38.2,<br />
27.0.<br />
1-(2-Azidoethyl)-2-(3,4-dichlorophenyl)-2-hydroxy-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-273)<br />
N<br />
Br<br />
N<br />
Br<br />
N<br />
OH<br />
Yield: 78 %. 1 H NMR (300 MHz, DMSO-d6) : δ = 9.12 (m, 2H), 8.20 (s, 1H), 8.09<br />
(s, 1H), 7.79 (m, 2H), 7.43 (m, 1H), 4.93 (m, 2H), 3.42 (m, 4H). 13 C NMR (75.5<br />
MHz, DMSO-d6): δ = 167.5, 154.9, 148.3, 139.0, 132.2, 131.3, 130.5, 129.5, 127.4,<br />
112.1, 89.8, 62.5, 48.0 (×2).<br />
Cl<br />
N 3<br />
N 3<br />
Cl
1-(3-Azidopropyl)-2-(3,4-dichlorophenyl)-2-hydroxy-2,3-dihydro-1Himidazo[1,2-a]pyrimidin-4-ium<br />
bromide (BS-274)<br />
N<br />
Br<br />
N<br />
N<br />
OH<br />
Yield: 81 %. 1 H NMR (300 MHz, DMSO-d6) : δ = 9.07 (m, 1H), 8.97 (m,1H) 8.12 (s,<br />
1H), 8.08 (Br s, 1H), 7.97 (m, 2H), 7.38 (t, J = 4.92 Hz, 1H), 4.86 (m, 2H), 3.37 (m,<br />
4H), 1.68 (m, 2H). 13 C NMR (75.5 MHz, DMSO-d6): δ = 167.5, 154.7, 148.1, 139.2,<br />
132.2, 131.3, 130.6, 129.3, 127.4, 111.6, 89.8, 62.4, 47.8, 38.3, 26.9.<br />
1-(2-Azidoethyl)-2-(4-chlorophenyl)-2-hydroxy-3-p-tolyl-2,3-dihydro-1Himidazo[1,2-a]pyrimidin-4-ium<br />
bromide (BS-299)<br />
N<br />
Br<br />
N<br />
Cl<br />
N<br />
OH<br />
Yield: 42 %. 1 H NMR (300 MHz, DMSO-d6) : δ = 9.19 (d, J = 3.06 Hz, 1H), 8.55 (d,<br />
J = 5.43 Hz, 1H), 7.71 (d, J = 8.52 Hz, 2H), 7.70 (s, 1H), 7.55 (d, J = 8.49 Hz, 2H),<br />
7.38 (m, 1H), 7.42 (d, J = 7.80 Hz, 2H), 7.08 (d, J = 7.80 Hz, 2H), 6.10 (s, 1H), 3.36<br />
(m, 4H), 2.33 (s, 3H) 13 C NMR (75.5 MHz, DMSO-d6): δ = 168.2, 156.1, 146.9,<br />
139.5, 135.9, 134.4, 129.4 (×6), 128.4 (×2), 124.4, 112.8, 93.5, 74.9, 47.9, 41.0, 20.7.<br />
1-(2-Azidoethyl)-2-(4-fluorophenyl)-2-hydroxy-2,3-dihydro-1H-imidazo[1,2a]pyrimidin-4-ium<br />
bromide (BS-300)<br />
N<br />
Br<br />
N<br />
N<br />
OH<br />
F<br />
Cl<br />
Cl<br />
N 3<br />
N 3<br />
N 3
Yield: 79 %. 1 H NMR (300 MHz, DMSO-d6) : δ = 9.09 (d, J = 4.53 Hz, 1H), 9.01 (d,<br />
J = 6.00 Hz, 1H), 8.04 (s, 1H), 7.85 (m, 2H), 7.37 (m, 3H), 4.92 (m, 2H), 3.38 (m,<br />
4H). 13 C NMR (75.5 MHz, DMSO-d6): δ = 167.5, 164.1, 160.9, 154.7, 148.4, 134.0<br />
(d), 129.4 (d), 115.4, 115.1, 111.9, 90.3, 62.7, 48.1 (×2).<br />
5-(4-Bromophenyl)-N-(2-(4-(4-methoxyphenyl)-1H-1,2,3-triazol-1-yl)ethyl)-1Himidazol-2-amine<br />
(BS-219)<br />
Br<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
N<br />
Yield: 66 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.62 (br s, 1H), 8.45 (s, 1H), 7.43<br />
(d, J = 8.8 Hz, 2H), 7.57 (d, J = 7.9 Hz, 2H), 7.43 (d, J = 8.8 Hz, 2H), 7.10 (s, 1H),<br />
6.98 (d, J = 8.8 Hz, 2H), 6.02 (m, 1H), 4.60 (t, J = 5.90 Hz, 2H), 3.78 (s, 3H), 3.68<br />
(m, 2H). 13 C NMR (75.5 MHz, DMSO-d6): δ =158.8, 150.0, 146.0, 131.0, 126.4<br />
(×4), 125.5 (×2), 123.4, 120.7, 117.5, 114.2 (×4), 55.0, 49.2. 42.8. HRMS (EI)<br />
C20H19BrN6O, calcd 438.0804, found :438.0811.<br />
5-Phenyl-N-(3-(4-phenyl-1H-1,2,3-triazol-1-yl)propyl)-1H-imidazol-2-amine (BS-<br />
238)<br />
N<br />
N<br />
H<br />
N<br />
H<br />
N<br />
N N<br />
Yield: 90 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.91 (br s, 1H), 8.63 (s, 1H), 7.88<br />
(d, J = 7.2 Hz, 2H), 7.59 (d, J = 7.2 Hz, 2H), 7.44 (t, J = 7.7 Hz, 2H), 7.27 (m, 3H),<br />
7.08 (m, 2H), 6.09 (br s, 1H), 4.50 (t, J = 7.1 Hz, 2H), 3.21 (m, 2H), 2.21 (m, 2H). 13 C<br />
NMR (75.5 MHz, DMSO-d6): δ = 150.3, 146.2, 133.0, 132.3, 130.8, 128.8 (×2),<br />
128.3, 127.7, 125.6, 125.0 (×2), 123.6 (×2), 121.4, 110.4, 104.1, 47.3, 28.8 (×2).<br />
HRMS (EI) C20H20N6, calcd 344.1749, found : 344.1734.<br />
5-Phenyl-N-(2-(4-phenyl-1H-1,2,3-triazol-1-yl)ethyl)-1H-imidazol-2-amine (BS-<br />
228)<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
N<br />
O
Yield: 84 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.68 (br s, 1H), 8.57 (s, 1H), 7.82<br />
(d, J = 7.3 Hz, 2H), 7.61 (m, 2H), 7.43 (t, J = 7.6 Hz, 2H), 7.28 (m, 3H), 7.06 (m,<br />
2H), 6.01 (br s, 1H), 4.63 (t, J = 6.1 Hz, 2H), 3.70 (m, 2H). 13 C NMR (75.5 MHz,<br />
DMSO-d6): δ = 150.3, 146.1, 130.4, 128.8 (×4), 128.2, 127.7, 125.1, 125.0 (×4),<br />
123.4, 121.7, 104.1, 49.3. 42.9. HRMS (EI) C19H18N6, calcd 330.1593, found :<br />
330.1582.<br />
5-(4-Bromophenyl)-N-(2-(4-p-tolyl-1H-1,2,3-triazol-1-yl)ethyl)-1H-imidazol-2amine<br />
(BS-231)<br />
Br<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
N<br />
Yield: 73 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.66 (br s, 1H), 8.50 (s, 1H), 7.70<br />
(d, J = 8.07 Hz, 2H), 7.57 (d, J = 8.31 Hz, 2H), 7.43 (d, J = 8.56 Hz, 2H), 7.22 (d, J =<br />
8.07 Hz, 2H), 7.13 (s, 1H), 6.03 (br s, 1H), 4.61 (t, J = 5.80 Hz, 2H), 3.68 (m, 2H),<br />
2.32 (s, 3H). 13 C NMR (75.5 MHz, DMSO-d6): δ = 150.4, 146.1, 136.9 (×2), 130.9<br />
(×2), 129.3 (×4), 128.0, 125.3, 124.9 (×3), 121.2, 117.4, 49.2, 42,8, 20.7. HRMS (EI)<br />
C20H19BrN6, calcd 422.0855, found : 422.0863.<br />
N-(2-(4-(4-Butylphenyl)-1H-1,2,3-triazol-1-yl)ethyl)-5-(naphthalen-1-yl)-1Himidazol-2-amine<br />
(BS-275)<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
N<br />
C4H9 Yield: 64 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.9 (br s, 1H), 8.54 (s, 1H), 8.14<br />
(s, 1H), 7.73 (m, 6H), 7.37 (m, 2H), 7.23 (m, 3H), 6.01 (m, 1H), 4.68 (m, 2H), 3.74<br />
(m, 2H), 2.58 (t, J = 7.4 Hz, 2H), 1.56 (m, 2H), 1.32 (m, 2H), 0.89 (t, J = 7.4 Hz, 3H).<br />
13<br />
C NMR (75.5 MHz, DMSO-d6): δ = 150.7, 146.2, 141.8, 133.5, 131.3, 128.7 (×3),<br />
128.3, 127.5, 127.3 (×3), 126.0, 125.0 (×3), 124.6, 123.2, 121.3, 120.2, 49.3, 42.9,<br />
34.5, 32.9, 21.7, 13.7. HRMS (EI) C27H28N6, calcd 436.2375, found : 436. 2349.
5-(4-Bromophenyl)-N-(2-(4-heptyl-1H-1,2,3-triazol-1-yl)ethyl)-1H-imidazol-2amine<br />
(BS-277)<br />
Br<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
N<br />
C 7H 15<br />
Yield: 73 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.56 (br s, 1H), 7.82 (s, 1H), 7.59<br />
(d, J = 8.2 Hz, 2H), 7.42 (d, J = 7.9 Hz, 2H), 7.13 (s, 1H), 5.93 (br s, 1H), 4.51 (t, J =<br />
5.90 Hz, 2H), 3.60 (m, 2H), 2.57 (d, J = 7.7 Hz, 2H), 1.57 (m, 2H), 1.25 (m, 8H), 0.85<br />
(t, J = 6.9 Hz, 3H). 13 C NMR (75.5 MHz, DMSO-d6): δ = 150.5, 146.7 (×2), 131.0<br />
(×3 ), 125.3, 121.9 (×2), 117.4, 104.1, 48.9, 42.9, 31.1, 28.9, 28.5, 28.4, 25.0, 22.0,<br />
13.9. HRMS (EI) C20H27BrN6, calcd 430.1481, found : 430.1488.<br />
5-(4-Bromophenyl)-N-(3-(4-(4-pentylphenyl)-1H-1,2,3-triazol-1-yl)propyl)-1Himidazol-2-amine<br />
(BS-278)<br />
Br<br />
N<br />
N<br />
H<br />
N<br />
H<br />
N<br />
N N<br />
C 5H 11<br />
Yield: 80 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.58 (br s, 1H), 8.55 (s, 1H), 7.72<br />
(d, J = 8.06 Hz, 2H), 7.53 (d, J = 8.06 Hz, 2H), 7.38 (d, J = 8.27 Hz, 2H), 7.23 (d, J =<br />
8.06 Hz, 2H), 7.11 (s, 1H), 5.96 (m, 1H), 4.47 (t, J = 6.57 Hz, 2H), 3.19 (m, 2H), 2.59<br />
(t, J = 7.63 Hz, 2H), 2.14 (m, 2H), 1.59 (m, 2H), 1.30 (m, 4H), 0.86 (t, J = 6.78 Hz,<br />
3H). 13 C NMR (75.5 MHz, DMSO-d6): δ = 146.3, 142.9, 131.0 (×2), 128.7 (×4),<br />
128.3, 125.4, 124.0 (×4), 121.0, 117.3 (×2), 47.3, 39.9, 34.8, 30.8, 30.5, 30.6, 21.9,<br />
13.8. HRMS (EI) C25H29BrN6. calcd.492.1637, found: 492. 1621.<br />
5-(3,4-Dichlorophenyl)-N-(2-(4-(4-heptylphenyl)-1H-1,2,3-triazol-1-yl)ethyl)-1Himidazol-2-amine<br />
( BS-279)<br />
Cl<br />
Cl<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
N<br />
C 7H 15
Yield: 80 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.66 (br s, 1H), 8.50 (s, 1H), 7.86<br />
(s, 1H), 7.71 (d, J = 8.3 Hz, 2H), 7.62 (m, 1H), 7.48 (d, J = 8.3 Hz, 1H), 7.22 (d, J =<br />
8.3 Hz, 3H), 6.06 (m, 1H), 4.61 (t, J = 5.77 Hz, 2H), 3.69 (m, 2H), 2.58 (t, J =<br />
7.58Hz, 2H), 1.57 (m, 2H), 1.28 (m, 8H), 0.86 (m, 3H). 13 C NMR (75.5 MHz,<br />
DMSO-d6): δ = 146.1, 141.8, 130.9 (×2), 130.3, 128.6 (×3), 128.2 (×2), 126.5,124.9<br />
(×3), 124.8, 124.7, 121.2, 49.2, 42.8, 34.8, 31.1, 30.7, 28.5, 28.4, 22.0, 13.8. HRMS<br />
(EI) C26H30Cl2N6, calcd 496.1909, found : 496.1919.<br />
5-(3,4-Dichlorophenyl)-N-(3-(4-((methylamino)methyl)-1H-1,2,3-triazol-1yl)propyl)-1H-imidazol-2-amine<br />
(BS-283)<br />
Cl<br />
Cl<br />
N<br />
N<br />
H<br />
N<br />
H<br />
N<br />
N N<br />
Yield: 81 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.70 (br s, 1H), 7.99 (s, 1H), 7.82<br />
(s, 1H), 7.58 (d, J = 8.7 Hz, 1H), 7.48 (d, J = 8.2 Hz, 1H), 7.23 (s, 1H), 6.01 (m, 1H),<br />
4.41 (t, J = 6.95 Hz, 2H), 3.67 (m, 2H), 3.14 (m, 2H), 2.26 (s, 3H), 2.07 (t, J = 6.5 Hz,<br />
2H), 1.86 (s,1H) 13 C NMR (75.5 MHz, DMSO-d6): δ = 151.4, 145.9, 135.9, 130.9<br />
(×2), 130.3, 126.4 (×2), 124.6, 123.4, 122.6, 47.0 (×2), 41.0, 35.4, 30.3. HRMS (EI)<br />
C16H19Cl2N7, calcd 389.1079, found: 389.1064.<br />
N-(3-(4-(2-Aminopropan-2-yl)-1H-1,2,3-triazol-1-yl)propyl)-5-(4-bromophenyl)-<br />
1H-imidazol-2-amine (BS-287)<br />
Br<br />
N<br />
N<br />
H<br />
N<br />
H<br />
N<br />
N N<br />
Yield: 75 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.57 (br s, 1H), 7.92 (s, 1H), 7.55<br />
(d, J = 8.3 Hz, 2H), 7.42 (d, J = 8.3 Hz, 2H), 7.11 (s, 1H), 5.94 (t, J = 5.6 Hz, 1H),<br />
4.38 (t, J = 7.0 Hz, 2H), 4.10 (m, 2H), 3.16 (m, 2H), 2.07 (m, 2H), 1.37 (s, 6H). 13 C<br />
NMR (75.5 MHz, DMSO-d6): δ = 156.0, 151.3, 134.0, 131.0 (×3), 125.3 (×2), 120.1<br />
(×2), 117.3, 54.8, 48.5, 47.1, 30.8 (×2), 30.1. HRMS (EI) C17H22BrN7, calcd<br />
403.1120, found: 403.1131.<br />
H 2N<br />
H<br />
N
5-(3,4-Dichlorophenyl)-N-(2-(4-cyclohexyl-1H-1,2,3-triazol-1-yl)ethyl)-1Himidazol-2-amine<br />
(BS-301)<br />
Cl<br />
Cl<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
N<br />
Yield: 85 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.64 (br s, 1H), 7.58 (s, 1H), 7.80<br />
(s, 1H), 7.60 (m, 1H), 7.48 (d, J = 8.3 Hz, 1H), 7.24 (s, 1H), 6.00 (m, 1H), 4.50 (t, J =<br />
5.76 Hz, 2H), 3.61 (m, 2H), 2.61 (m, 1H), 1.91 (m, 2H), 1.69 (m, 3H), 1.32 (m,5H).<br />
13<br />
C NMR (75.5 MHz, DMSO-d6): δ = 151.9, 150.6, 131.0 (×2), 130.3, 126.6 (×2),<br />
124.7, 123.4, 120.7, 104.1, 54.8, 49.0, 42.8, 34.5, 32.4 (×2), 25.5 (×2).HRMS (EI)<br />
C19H22Cl2N6, calcd 404.1283., found: 404.1278.<br />
5-(3,4-Dichlorophenyl)-N-(2-(4-propyl-1H-1,2,3-triazol-1-yl)ethyl)-1H-imidazol-<br />
2-amine (BS-302)<br />
Cl<br />
Cl<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
N<br />
C 3H 7<br />
Yield: 90 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.80 (br s, 1H), 7.84 (d, J = 1.7<br />
Hz, 1H), 7.82 (s, 1H), 7.59 (d of d, J = 8.4, 1.7 Hz, 1H), 7.53 (d, J = 8.4 Hz, 1H), 7.26<br />
(s, 1H), 6.14 (br s, 1H), 4.51 (t, J = 6.04 Hz, 2H), 3.62(m, 2H), 2.56 (t, J = 7.49 Hz,<br />
2H), 1.57 (m, 2H), 0.89 (t, J = 7.25 Hz, 3H). 13 C NMR (75.5 MHz, DMSO-d6): δ =<br />
150.4, 146.5, 135.0, 131.0 (×2), 130.4 126.8 (×2), 124.8, 123.5, 122.0, 48.8, 42.8,<br />
27.0, 22.0, 13.6. HRMS (EI) C16H18Cl2N6, calcd 364.0970., found: 364.0980.<br />
5-(3,4-Dichlorophenyl)-N-(3-(4-propyl-1H-1,2,3-triazol-1-yl)propyl)-1Himidazol-2-amine<br />
(BS-303)<br />
Cl<br />
Cl<br />
N<br />
N<br />
H<br />
N<br />
H<br />
N<br />
N N<br />
C 3H 7
Yield: 83 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.80 (br s, 1H), 7.88 (s, 1H), 7.83<br />
(d, J = 1.7 Hz 1H), 7.58 (d of d, J = 8.3, 1.7 Hz, 1H), 7.52 (s, 1H), 7.49 (s, 1H), 6.13<br />
(br s, 1H), 4.38 (t, J = 6.98 Hz, 2H), 3.15 (m, 2H), 2.57 (t, J = 7.51 Hz, 2H), 2.06 (m,<br />
2H), 1.58 (m, 2H), 0.89 (t, J = 7.51 Hz, 3H). 13 C NMR (75.5 MHz, DMSO-d6): δ =<br />
150.0, 146.6, 135.1, 131.0 (×2), 130.3 126.8 (×2), 124.8, 123.5, 121.7, 54.8, 46.9,<br />
30.0, 27.0, 22.2, 13.5. HRMS (EI) C17H20Cl2N6, calcd 378.1127., found : 378.1114.<br />
5-(4-Bromophenyl)-N-(2-(4-propyl-1H-1,2,3-triazol-1-yl)ethyl)-1H-imidazol-2amine<br />
(BS-304)<br />
Br<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
N<br />
C 3H 7<br />
Yield: 95 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.63 (br s, 1H), 7.87(s, 1H), 7.62<br />
(m, 2H), 7.48 (d , J = 8.6 Hz, 2H), 7.17 (s, 1H), 5.98 (t, J = 5.3 Hz, 1H), 4.59 (t, J =<br />
6.04 Hz, 2H), 3.66 (m, 2H), 2.61 (t, J = 7.44 Hz, 2H), 1.62 (m, 2H), 0.94 (t, J = 7.21<br />
Hz, 3H). 13 C NMR (75.5 MHz, DMSO-d6): δ = 150.5, 146.5, 134.6, 131.0 (×3),<br />
125.4 (×2), 122.0 (×2), 117.4, 48.9, 42.9, 27.0, 22.2, 13.6. HRMS (EI) C16H19BrN6,<br />
calcd 374.0855., found: 374.0844.<br />
5-(4-Bromophenyl)-N-(3-(4-propyl-1H-1,2,3-triazol-1-yl)propyl)-1H-imidazol-2amine<br />
(BS-305)<br />
Br<br />
N<br />
N<br />
H<br />
N<br />
H<br />
N<br />
N N<br />
C 3H 7<br />
Yield: 74 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.59 (br s, 1H), 7.89 (s, 1H), 7.55<br />
(d , J = 8.1 Hz, 2H), 7.42 (d , J = 8.4 Hz, 2H), 7.11 (s, 1H), 5.93 (t, J = 5.25 Hz, 1H),<br />
4.38 (t, J = 6.83 Hz, 2H), 3.14 (m, 2H), 2.48 (t, J = 7.62 Hz, 2H), 2.06 (m, 2H), 1.58<br />
(m, 2H), 0.90 (t, J = 7.35 Hz, 3H). 13 C NMR (75.5 MHz, DMSO-d6): δ = 151.1,<br />
146.6, 134.6, 131.0 (×3), 125.4 (×2), 121.7 (×2), 117.4, 47.9, 30.0, 27.0 (×2), 22.2,<br />
13.5. HRMS (EI) C17H21BrN6, calcd 388.1011., found: 388.1023.
(2-(3-(4-Propyl-1H-1,2,3-triazol-1-yl)propylamino)-1H-imidazol-5yl)(morpholino)methanone<br />
(BS-306)<br />
O<br />
O<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N N<br />
C 3H 7<br />
Yield: 29 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.02 (br s, 1H), 7.85 (s, 1H), 7.10<br />
(s, 1H), 6.05 (m, 1H), 4.35 (t, J = 6.8 Hz, 2H), 3.75 (m, 4H), 3.57 (t, J = 4.31 Hz, 4H),<br />
3.10 (m, 2H), 2.57 (t, J = 7.42 Hz, 2H), 2.05 (m, 2H), 1.60 (m, 2H), 0.90 (t, J = 7.42<br />
Hz, 3H). 13 C NMR (75.5 MHz, DMSO-d6): δ = 161.2, 150.1, 146.6, 122.8, 121.7<br />
(×2), 66.3 (×2), 54.8 (×2), 46.9, 44.4, 29.9, 27.0, 22.2, 13.5. HRMS (EI) C16H25N7O2,<br />
calcd 347.2070., found: 347.2085.<br />
(2-(2-(4-Propyl-1H-1,2,3-triazol-1-yl)ethylamino)-1H-imidazol-5yl)(morpholino)methanone<br />
(BS-307)<br />
O<br />
O<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
N<br />
C 3H 7<br />
Yield: 29 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.89 (br s, 1H), 7.78 (s, 1H), 7.08<br />
(s, 1H), 5.98 (m, 1H), 4.45 (m, 2H), 3.74 (m, 3H), 3.58 (m, 6H), 3.16 (m, 1H), 2.56<br />
(m, 2H), 1.57 (m, 2H), 0.89 (t, J = 7.25 Hz, 3H). 13 C NMR (75.5 MHz, DMSO-d6): δ<br />
= 161.4, 149.7, 146.5 (×2), 121.9 (×2), 66.3 (×2), 48.7 (×2), 44.4, 44.7, 27.0, 22.2,<br />
13.6. HRMS (EI) C15H23N7O2, calcd 333.1913., found: 333.1920.<br />
N-(2-(4-(Cyclopentylmethyl)-1H-1,2,3-triazol-1-yl)ethyl)-5-(4-fluorophenyl)-1Himidazol-2-amine<br />
(BS-308)<br />
F<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
N<br />
Yield: 68 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.63 (br s, 1H), 7.82 (s, 1H),<br />
7.63 (q, J = 2.9, 5.7 Hz, 2H), 7.11 (t , J = 8.7 Hz, 2H), 7.03 (s, 1H), 5.96 (t, J = 5.4<br />
Hz, 1H), 4.51 (t, J = 5.99 Hz, 2H), 3.61 (m, 2H), 2.59 (d, J = 7.08 Hz, 2H), 2.07 (m,
1H), 1.66 (m, 6H), 1.70 (m, 2H). 13 C NMR (75.5 MHz, DMSO-d6): δ = 161.8, 158.6,<br />
150.3, 146.2, 146.1, 130.9, 125.2, 125.1, 122.2, 115.1, 114.8, 48.9, 42.9, 31.8 (×3),<br />
31.0, 24.5 (×2). HRMS (EI) C19H23FN6, calcd 354.1968., found: 354.1974.<br />
N-(2-(4-Cyclopropyl-1H-1,2,3-triazol-1-yl)ethyl)-5-(4-fluorophenyl)-1H-imidazol-<br />
2-amine (BS-309)<br />
F<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
N<br />
Yield: 80 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.55 (br s, 1H), 7.79 (s, 1H),<br />
7.64 (m, 2H), 7.10 (t , J = 8.7 Hz, 2H), 7.02 (s, 1H), 5.90 (m, 1H), 4.99 (t, J = 5.85<br />
Hz, 2H), 3.61 (m, 2H), 1.91 (m, 1H), 0.85 (m, 2H), 0.69 (m, 2H). 13 C NMR (75.5<br />
MHz, DMSO-d6): δ = 161.8, 158.6, 150.4, 148.6 (×2), 131.1, 125.1, 125.0, 120.9,<br />
115.1, 114.8, 48.9, 42.9, 7.6(×2), 6.5. HRMS (EI) C16H17FN6, calcd 312.1499., found:<br />
312.1487.<br />
5-(4-Chlorophenyl)-N-(2-(4-cyclopentyl-1H-1,2,3-triazol-1-yl)ethyl)-4-p-tolyl-1Himidazol-2-amine(BS-310-B)<br />
Cl<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
N<br />
Yield: 16 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.89 (br s, 1H), 7.84 (s, 1H), 7.40<br />
(m, 2H), 7.29 (m, 4H), 7.14 (m, 2H), 5.87 (m, 1H), 4.52 (t, J = 5.87 Hz, 2H), 3.64 (m,<br />
2H), 3.06 (m, 1H), 2.29 (s, 3H), 1.95 (m, 2H), 1.60 (m, 6H). 13 C NMR (75.5 MHz,<br />
DMSO-d6): δ = 150.9, 150.1, 135.7, 130.0, 128.9 (×3), 128.1 (×3), 128.0 (×2), 127.2<br />
(×3), 121.1, 104.1, 49.0, 42.7, 36.1, 32.7 (×2), 24.6 (×2), 20.7. HRMS (EI)<br />
C25H27ClN6. calcd.446.1986, found: 446.1990.
N-(3-(4-(4-Tert-butylphenyl)-1H-1,2,3-triazol-1-yl)propyl)-5-(3,4dichlorophenyl)-1H-imidazol-2-amine<br />
(BS-340):<br />
Cl<br />
Cl<br />
N<br />
N<br />
H<br />
N<br />
H<br />
N<br />
N N<br />
Yield: 91 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.68 (br s, 1H), 8.53 (s, 1H), 7.82<br />
(s, 1H), 7.73 (d, J = 7.9 Hz, 2H), 7.57 (m, 1H), 7.43 (m, 3H), 7.25 (s, 1H) 6.02 (m,<br />
1H), 4.48 (t, J = 6.73 Hz, 2H), 3.20 (m, 2H), 2.14 (m, 2H), 1.30 (s, 9H). 13 C NMR<br />
(75.5 MHz, DMSO-d6): δ = 150.2, 146.2, 131.0, 130.3, 128.0, 126.6, 125.5 (×3),<br />
124.8 (×3), 124.7, 123.4, 121.0 (×2), 104.1, 47.3, 39.6, 34.2, 31.0 (×3), 29.9.HRMS<br />
(EI) C24H26Cl2N6, calcd 468.1596, found: 468.1602.<br />
5-(3,4-Dichlorophenyl)-N-(3-(4-(thiophen-3-yl)-1H-1,2,3-triazol-1-yl)propyl)-1Himidazol-2-amine<br />
(BS-341):<br />
Cl<br />
Cl<br />
N<br />
N<br />
H<br />
N<br />
H<br />
N<br />
N N<br />
Yield: 80 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.67 (br s, 1H), 8.46 (s, 1H), 7.82<br />
(m, 2H), 7.63 (m, 1H), 7.58 (m, 1H), 7.51 (m, 2H), 7.26 (s, 1H) 6.02 (m, 1H), 4.47 (t,<br />
J = 6.8 Hz, 2H), 3.19 (m, 2H), 2.14 (m, 2H). 13 C NMR (75.5 MHz, DMSO-d6): δ =<br />
151.3, 142.8, 132.1 (×2), 131.0, 130.0, 127.0, 126.5, 125.7, 124.7, 123.4, 121.1, 120.6<br />
(×2), 104.1, 47.3, 39.5, 29.9. HRMS (EI) C18H16Cl2N6S, calcd 418.0534, found:<br />
418.0522.<br />
5-(4-Bromophenyl)-N-(2-(4-cyclopropyl-1H-1,2,3-triazol-1-yl)ethyl)-1H-imidazol-<br />
2-amine(BS-342):<br />
Br<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
N<br />
Yield: 78 %. 1 H NMR (300 MHz, DMSO-d6): δ = 10.56 (br s, 1H), 7.80 (s, 1H), 7.60<br />
(d, J = 7.3 Hz, 2H), 7.43 (d, J = 7.3 Hz, 2H), 7.14 (s, 1H), 5.93 (m, 1H), 4.49 (t, J =<br />
S
5.48 Hz, 2H), 3.59 (m, 2H), 3.16 (d of d, J = 5.2, 1.4 Hz, 1 H), 0.87 (m, 2H), 0.69 (m,<br />
2H). 13 C NMR (75.5 MHz, DMSO-d6): δ = 150.4, 148.7 (×3), 131.0, 130.9, 125.3,<br />
120.9 (×3), 117.4, 48.9, 42.8, 7.5 (×2), 6.5. HRMS (EI) C16H17BrN6, calcd 372. 0698,<br />
found: 372.0689.<br />
4.9 Representative NMR spectra<br />
4.9.1 1 H and 13 C NMR spectra of bs-272<br />
170<br />
167.5180<br />
9.0686<br />
9.0591<br />
9.0535<br />
8.9901<br />
8.9844<br />
8.9694<br />
8.9637<br />
Integral<br />
160<br />
1.9907<br />
9.0<br />
154.7139<br />
148.2373<br />
150<br />
140<br />
137.6005<br />
8.0015<br />
7.7800<br />
7.7505<br />
7.7216<br />
7.6921<br />
7.3908<br />
7.3745<br />
7.3701<br />
7.3544<br />
1.0890<br />
8.0<br />
3.9124<br />
131.4039<br />
129.3129<br />
0.9792<br />
122.9491<br />
N<br />
Br<br />
130<br />
N<br />
Br<br />
7.0<br />
N<br />
120<br />
N<br />
111.5523<br />
N<br />
OH<br />
110<br />
N<br />
OH<br />
Br<br />
Br<br />
6.0<br />
N 3<br />
100<br />
N 3<br />
90.3697<br />
90<br />
(ppm)<br />
4.9593<br />
4.9109<br />
4.8569<br />
4.8086<br />
2.0000<br />
5.0<br />
(ppm)<br />
80<br />
4.0<br />
70<br />
62.5832<br />
8.6996<br />
60<br />
3.4617<br />
3.4378<br />
3.3788<br />
3.3437<br />
3.3217<br />
3.2991<br />
3.0<br />
50<br />
47.9135<br />
40.0332<br />
39.7568<br />
39.4768<br />
39.2005<br />
38.9205<br />
27.0036<br />
40<br />
2.0<br />
30<br />
1.6835<br />
1.6609<br />
1.6377<br />
1.9439<br />
20<br />
1.0<br />
10<br />
0.0<br />
0
4.9.2<br />
1 H and 13 C NMR spectra of bs-304<br />
Integral<br />
160<br />
11.0<br />
10.6535<br />
0.7987<br />
150.5865<br />
146.5318<br />
150<br />
10.0<br />
140<br />
134.0549<br />
131.0403<br />
130<br />
9.0<br />
125.4219<br />
122.0327<br />
120<br />
Br<br />
117.4725<br />
Br<br />
7.8767<br />
7.6231<br />
7.5139<br />
7.4857<br />
0.9951<br />
1.8738<br />
1.9716<br />
8.0<br />
110<br />
7.1731<br />
N<br />
H<br />
0.9264<br />
N<br />
7.0<br />
N<br />
N<br />
H<br />
100<br />
N<br />
H<br />
N<br />
H<br />
6.0069<br />
5.9887<br />
5.9705<br />
90<br />
N<br />
N<br />
N<br />
0.9433<br />
6.0<br />
(ppm)<br />
N<br />
N<br />
N<br />
C 3H7<br />
80<br />
(ppm)<br />
C 3H 7<br />
5.0<br />
4.5890<br />
4.5689<br />
4.5488<br />
70<br />
1.9449<br />
60<br />
3.6965<br />
3.6764<br />
3.6569<br />
3.6368<br />
4.0<br />
1.9690<br />
3.0<br />
2.6414<br />
2.6169<br />
2.5918<br />
1.9586<br />
48.9026<br />
42.9570<br />
40.3132<br />
39.7568<br />
39.4805<br />
39.2005<br />
38.6441<br />
50<br />
40<br />
2.0<br />
30<br />
27.0764<br />
1.6773<br />
1.6528<br />
1.6283<br />
1.6032<br />
0.9724<br />
0.9479<br />
0.9235<br />
1.9563<br />
22.2144<br />
20<br />
3.0000<br />
1.0<br />
13.6286<br />
10<br />
0.0<br />
0
4.10 References<br />
[1] For a general review of the synthesis and activity of 2-aminoimidazole alkaloids, see: (a) S.<br />
M. Weinreb, (2007) Nat. Prod. Rep. 24, 931–948. (b) H. Hoffmann, T. Lindel, (2003)<br />
Synthesis. 1753–1783. (c) J. D. Sullivan, R. L. Giles, R. E. Looper. (2009) Curr. Bioactive<br />
Cmpds. 5, 39-78.<br />
[2] For the anti-biofilm activity of 2-aminoimidazoles, see: (a) R. W. Huigens III, J. J. Richards,<br />
G. Parise, T. E. Ballard, W. Zeng, R. Deora, C. Melander, (2007) J. Am. Chem. Soc. 129,<br />
6966–6967. (b) S. A. Rogers, C.Melander, (2008) Angew. Chem. 120, 5307–5309., (2008)<br />
Angew. Chem. Int. Ed. 47, 5229–5231. (c) T. E. Ballard, J. J. Richards, A. L. Wolf, C.<br />
Melander, (2008) Chem. Eur. J. 14, 10745–10761.<br />
[3] (a) M. S. Malamas, J. Erdei, I. Gunawan, J. Turner, Y. Hu, E. Wagner, K. Fan, R.Chopra, A.<br />
Olland, J. Bard, S. Jacobsen, R. L. Magolda, M. Pangalos, A. J. Robi- chaud. (2010) J. Med.<br />
Chem. 53, 1146–1158. (b) M. S. Malamas, J. rdei, I. Gunawan, K. Barnes, M. Johnson, Y.<br />
Hui, J. Turner, Y.Hu, E. Wagner, K. Fan, A. Olland, J. Bard,A. J. Robichaud. (2009) J. Med.<br />
Chem. 52, 6314–6323.<br />
[4] (a) R. S. Coleman, E. L. Campbell, D. J. Carper. (2009) Org. Lett. 11, 2133–2136. (b) M.<br />
Nodwell, A. Pereira, J. L. Riffell, C. Zimmermann, B. O. Patrick, M. Roberge, R. J. Andersen.<br />
(2009) J. Org. Chem. 74, 995–1006.<br />
[5] (a) A. G. Beaman, W. Tautz, T. Gabriel, R. Duschinsky. (1966) J. Am. Chem. SOC. 87, 389.<br />
(b) G. C. Lancini, E. Lazzari, V. Arioli, P. Bellani. (1969) J. Med. Chem. 12, 775<br />
[6] (a) A. Lawson. (1956) J. Am. Chem. Soc. 307–310. (b) B. T. Storey, W. W. Sullivan, C. L.<br />
Moyer. (1964) J. Org. Chem. 29, 3118–3120. (c) G. C. Lencini,; E. Lazzari. (1966) J.<br />
Heterocycl. Chem. 3, 152–154.<br />
[7] (a) N. S. Aberle, L. Guillaume, K. G. Watson. (2006) Org. Lett. 8, 419–421. (b) N. Aberle, J.<br />
Catimel, E. C. Nice, K. G. Watson. (2007) Bioorg. Med. Chem. Lett. 17,3741–3744.<br />
[8] C. H. Soh, W. K. Chui, Y. Lam. (2008) J.Comb.Chem. 10,118.<br />
[9] P. Molina, P. Fresneda, M. Sanz. (1999) J. Org. Chem. 64, 2540–2544.<br />
[10] T. Moschny, H. Hartmann. (1999) Helv. Chim. Acta 82, 1981–1993.<br />
[11] S. Ohta, N. Tsuno, S. Nakamura, N. Taguchi, M. Yamashita, I. Kawasaki, M. Fujieda. (2000)<br />
Heterocycles. 53, 1939–1955.<br />
[12] (a) H. C. Kolb, M. G. Finn, K. B. Sharpless. (2001) Angew. Chem., Int. Ed. 40, 2004-2021.<br />
(b) H. C. Kolb, K. B. Sharpless. (2003) Drug Discovery Today. 8, 1128 1137. (c) C. W.<br />
Tornøe, C. Christensen, M. Meldal. (2002) J. Org. Chem., 67, 3057-3064.<br />
[13] (a) E. Lieber, T. S. Chao, C. N. R. Rao. (1963) Organic Syntheses. Coll. Vol. 4, 380., 1957.<br />
Vol. 37, 26. (b) El. Ashry, Y. El Kilany, N. Rashed, H. Assafir, (1999) Adv. Heterocycl.<br />
Chem. 75, 79. (c) D. J. Brown, Mechanisms of Molecular Migrations. Thyagarajan, B. S.,<br />
(1968) Wiley-Interscience: New York, Vol. 1, 209.<br />
[14] For synthesis and anti biofilm activity see (a) D. S. Ermolat’ev, J. B. Bariwal, H. P. L.<br />
Steenackers, S. C. J. De Keersmaecker, E. V. Van der Eycken, (2010) Angew. Chem. Int. Ed.
49, 9465–9468. (b) D. S. Ermolat'ev, E. V. Babaev, E. V. Van der Eycken. (2006) Org Lett. 8,<br />
5781-5784. (c) D. S. Ermolat'ev, E. V. Van der Eycken. (2008) J. Org Chem. 73, 6691-6697.<br />
(d) D. S. Ermolat’ev, B. Savaliya, A. Shah, E. Van der Eycken. (2010) Molecular Diversity.<br />
DOI 10.1007/s11030-010-9270-5 (e) H. P. L. Steenackers, D. S. Ermolat’ev, B. Savaliya, A.<br />
De Weerdt, D. De Coster, A. Shah, E. V. Van der Eycken, D. E. De Vos, J. Vanderleyden, S.<br />
C.J. De Keersmaecker. (2010) J. Med Chem. DOI: 10.1021/jm 1011148.<br />
[15] For microwave-assisted procedure see: P. Appukkuttan, W. Dehaen, V. V. Fokin, E. Van der<br />
Eycken. Org. Lett., 2004, 6, 4223-4225. (b) For click chemistry under non-classical conditions<br />
see: C. O. Kappe, E. Van der Eycken. Chem. Soc. Rev., 2010, 39, 1280–1290, and references<br />
cited therein.<br />
[16] (a) D. Raut, K. Wankhede, V. Vaidya, S. Bhilare, N. Darwatkar, A. Deorukhkar, G. Trivedi,<br />
M. Salunkhe. (2009) Catalysis Communications. 10 1240–1243. (b) A. Sarkar, T. Mukherjee,<br />
S. Kapoor. (2008) J. Phys. Chem. C 112, 3334 3340.
Crystal and Molecular Structure Analysis of<br />
DP-7: A New Multi Drug Resistance Reverter<br />
Lead Molecule
Chapter-5<br />
“Crystal and Molecular Structure Analysis of DP-7: A New<br />
Multi Drug Resistance Reverter Lead Molecule”<br />
O<br />
N<br />
H<br />
O<br />
O<br />
The synthesis of this 3,5-Dibenzoyl-4-(3-methoxyphenyl)-1,4-dihydro-2,6-dimethyl<br />
pyridine DP7, bearing dibenzoyl groups at C(3) and C(5), respectively, has been<br />
achieved by applying the modified Hantzsch-type condensation of 1,3-Diketone (2<br />
equiv) and aromatic aldehydes (1 equiv) using ammonium carbonate as nitrogen<br />
source. The product obtained was characterized by spectroscopic techniques & in<br />
order to correlate structure activity relationship, the X-ray crystallographic study of<br />
DP-7 has been carried out.<br />
Publication:<br />
[1] Synthesis, Characterization, Crystal and molecular structure analysis of DP-7:<br />
A new Multi Drug Resistance Reverter Lead Molecule Cryst. Res. Technol. (2010)<br />
Manuscript in preparation.
5.1 Introduction<br />
The membrane efflux protein P-glycoprotein, a member of the ATP binding cassette<br />
(ABC) family, recognizes and transports structurally, chemically, and<br />
armacologically diverse hydrophobic compounds, giving rise to a phenomenon known<br />
as multidrug resistance (MDR). Development of MDR is one of the main reasons of<br />
failure in cancer chemotherapy, as tumour cells, by increasing drug efflux, acquire<br />
cross-resistance to many structurally and functionally unrelated anticancer agents,<br />
which therefore never achieve effective intracellular concentrations 1 . In the past few<br />
years, extensive studies have been performed with the aim of developing effective<br />
chemo sensitizers to overcome MDR of human cancer cells. Potent P-glycoprotein<br />
inhibitors have been tested in clinical trials so far, including Ca2+ channel blockers<br />
such as verapamil and dihydropyridines 2,3 . However, clinical application of these<br />
agents has not been extensively pursued to date, owing to their unwanted and<br />
sometimes life threatening cardiovascular side effects such as atria-ventricular block<br />
and hypotension. As a consequence, in the last few years, much attention has been<br />
focused on congeners of these first generation-MDR inhibitors, in order to develop<br />
compounds characterized by appropriate potency and selectivity but also by reduced<br />
cardiovascular toxicity.<br />
Very recently, 3,5-Dibenzoyl-4-(3-phenoxyphenyl)-1,4-dihydro-2,6-dimethylpyridine<br />
(DP7) was proposed as a new MDR reverter. It was found that DP7, at a<br />
concentration two order of magnitude higher than its IC50 as a P-glycoprotein<br />
inhibitor, was devoid of cardiovascular effects in in vitro rat preparations 4,5 . These<br />
data were not considered sufficient evidence of DP7 safety before this drug could be<br />
subjected to clinical investigation. Several 1,4 dihydropyridine calcium antagonists<br />
are substrate of CYP enzymes. In particular, CYP3A4 metabolizes dihydropyridines<br />
into the corresponding pyridines 6 . The dihydropyridine can also inhibit the activity of<br />
CYP3A4. For example, Katoh 7 reported that nicardipine, benidipine, maidipine and<br />
barnidipine strongly inhibited human CYP3A4 activity, while nivaldipine, nifedipine,<br />
nitrendepine and amlodipine exhibited a weak inhibition.<br />
The DP-7 was very well explored for variety of biological activity 8 . It was very<br />
important to study the X-ray Crystal structure of this molecule which was not studied
so far and therefore development of single crystal was taken up in the current work.<br />
Thus the synthesis was optimized and studied.<br />
5.2 Reaction Scheme<br />
5.2.1 Scheme-1 1-phenylbutane-1,3-dione<br />
5.2.2 Scheme-2 DP-7<br />
Ph<br />
O<br />
O<br />
O<br />
(NH 4) 2CO 3<br />
Ph<br />
O<br />
Ph<br />
5.3 Method of Crystallization<br />
O<br />
O<br />
O<br />
O<br />
O<br />
Ph<br />
CH 3ONa<br />
0 o C<br />
Ph<br />
MeOH<br />
18 Hrs reflux<br />
O O<br />
Ph<br />
O<br />
N<br />
H<br />
O Ph<br />
0.1gm of DP-7 was taken in 25 ml of methanol into 50ml single neck RBF and<br />
Charcoal (2 g) was added. The solution was heated up to reflux temperature on a<br />
water bath for 45 min. The solution was filtered, while hot through Whatmann 42<br />
filter paper. The resulting solution was kept in a stopper conical flask slightly opened.<br />
After 10 days, crystals grew in cubic shape due to thin layer evaporation. They were<br />
filtered and washed with chilled methanol.<br />
5.4 Crystal structure determination:<br />
A single crystal of suitable size was chosen for X-ray diffraction studies. The data<br />
were collected at room temperature on a DIPLabo Image Plate system with graphite<br />
monochromated radiation MoKα. Each exposure of the image plate was set to a period<br />
of 400 s. Thirty-six frames of data were collected in the oscillation mode with an<br />
O<br />
Ph
oscillation range of 5˚ and processed using Denzo 9 . The reflections were merged with<br />
Scalepack. All the frames could be indexed using a primitive trilinic lattice. The<br />
structure was solved by direct methods using SHELXS-97 10 . Least-squares refinement<br />
using SHELXL-97 10 with isotropic displacement parameters for all the non-hydrogen<br />
atoms converged the residual to 0.1999. Subsequent refinements were carried out with<br />
anisotropic thermal parameters for the non-hydrogen atoms. After eight cycles of<br />
refinement the residuals converged to 0.0578. The hydrogen atoms were fixed at<br />
chemically acceptable positions, and were allowed to ride on their parent atoms.<br />
5.5 Results and discussion:<br />
The details of crystal data and refinement are given in Table 1. The bond lengths and<br />
bond angles of all the non-hydrogen atoms (Table 2 and 3.) and are in good agreement<br />
with the standard values 10 . Figure 1 represents the ORTEP 12 diagram of the molecule<br />
with thermal ellipsoids drawn at 50% probability.<br />
In the title compound C33H27NO3, the 1,4-dihydropyridine ring is in boat<br />
conformation, with atoms N1 and C4 deviating from the plane 13 (Cremer and Pople,<br />
1975) defined by the atoms N1/C2/C3/C4/C5/C6 by 0.1793(2)Å and 0.271(2)Å,<br />
respectively. The 1,4-dihydropyridine ring is puckered. The puckering parameters are<br />
Q = 0.406(2)Å, θ =106.0(3)˚ and Φ =2.4(3)˚. The dihedral angle between the least<br />
squares planes of the ring 1 and 2 is 87.70(1)˚, indicating that the ring 2 is nearly<br />
orthogonal to the dihydropyridine ring. The dihedral angles between the plane (1,3),<br />
(1,4) and (3,4) are 60.74(1)˚, 53.54˚ and 79.49˚, respectively. The structural<br />
conformation of carbomyl groups at C3 and C5 position is described by the torsion<br />
angle values of 50.09˚ and 161.10˚ and have -syn-periplanar and -anti-periplanr<br />
conformations. The structure exhibits coplanarity of the carbomyl group (C=O) with<br />
the conjugated double bond of the 1,4-dihydropyridine ring. The structure exhibit<br />
both inter and intramolecular hydrogen bonds of the type N–H. . .O and C–H. . .O, the<br />
hydrogen bonds bind the molecules into infinite one- dimensional chain. The<br />
observed hydrogen bonds are listed in Table 4. The packing of the molecules down b<br />
axis is shown in the Figure 2.
Empirical formula C33H27NO3<br />
Formula weight 485.56<br />
Temperature 293 k<br />
Wavelength 0.71073 Å<br />
Crystal system Triclinic<br />
Space group Pī<br />
a = 7.4310(6Å), b =12.2580(16)Å, c =<br />
Cell dimensions 14.4180(17)Å, α = 92.066(3)˚, β=95.319(7)˚, γ=<br />
96.235(7)˚<br />
Volume 1298.5(3)Å 3<br />
Z 2<br />
Density(calculated) 1.242Mg/m 3<br />
Absorption coefficient 0.079 mm -1<br />
F000<br />
Crystal size 0.30 x 0.27 x 0.25 mm<br />
Theta range for data collection 3.07˚ to 25.02˚<br />
Index ranges -8
C12-C13 1.372(4) C32-C37 1.390(3)<br />
C13-C14 1.383(4) C33-C34 1.382(3)<br />
C13-O15 1.392(3) C34-C35 1.372(4)<br />
O15-C16 1.387(3) C35-C36 1.379(4)<br />
C16-C17 1.353(4) C36-C37 1.378(3)<br />
C16-C21 1.362(5)<br />
Table-2: Bond lengths (Å)<br />
Atoms Angle(˚) Atoms Angle(˚)<br />
C2-N1-C6 122.62(2) C21-C16-O15 117.5(3)<br />
N1-C2-C3 118.10(2) C16-C17-C18 118.2(3)<br />
N1-C2-C8 113.33(2) C19-C18-C17 119.5(4)<br />
C3-C2-C8 128.53(2) C20-C19-C18 121.0(4)<br />
C2-C3-C30 126.66(2) C19-C20-C21 120.7(4)<br />
C2-C3-C4 118.06(2) C20-C21-C16 119.1(3)<br />
C30-C3-C4 115.09(2) O23-C22-C5 123.7(2)<br />
C3-C4-C5 108.93(1) O23-C22-C24 119.5(2)<br />
C3-C4-C9 114.15(2) C5-C22-C24 116.65(2)<br />
C5-C4-C9 109.54(2) C25-C24-C29 118.8(3)<br />
C6-C5-C22 122.16(2) C25-C24-C22 121.4(2)<br />
C6-C5-C4 118.62(2) C29-C24-C22 119.7(2)<br />
C22-C5-C4 119.04(2) C26-C25-C24 120.6(3)<br />
C5-C6-N1 117.99(2) C27-C26-C25 119.9(3)<br />
C5-C6-C7 127.0(2) C26-C27-C28 120.0(3)<br />
N1-C6-C7 114.96(2) C27-C28-C29 120.9(3)<br />
C10-C9-C14 117.8(2) C28-C29-C24 119.8(3)<br />
C10-C9-C4 123.18(2) O31-C30-C3 118.58(2)<br />
C14-C9-C4 118.97(2) O31-C30-C32 117.36(2)<br />
C9-C10-C11 120.7(2) C3-C30-C32 123.99(2)<br />
C12-C11-C10 121.3(3) C33-C32-C37 119.10(2)<br />
C11-C12-C13 118.6(2) C33-C32-C30 118.92(2)<br />
C12-C13-C14 121.0(2) C37-C32-C30 121.67(2)<br />
C12-C13-O15 116.8(2) C34-C33-C32 120.4(2)<br />
C14-C13-O15 122.0(3) C35-C34-C33 120.1(2)<br />
C13-C14-C9 120.5(2) C34-C35-C36 119.9(2)<br />
C16-O15-C13 119.0(2) C37-C36-C35 120.6(2)<br />
C17-C16-C21 121.5(3) C36-C37-C32 119.9(2)<br />
C17-C16-O15 120.8(3)<br />
Table-3: Bond angles (˚)<br />
Atoms Length (Å) Angle(˚) Symmetry codes<br />
N1–H1. . .O31 2.999(2) 156 1 + x, y, z<br />
Table-4: Hydrogen bonding geometry
Fig.-1: ORTEP of the molecule with thermal ellipsoids drawn at 50%<br />
probability.<br />
Fig.-2: Packing of the molecules when viewed down the a axis. The dashed line<br />
represents the hydrogen bond.
Fig.-3: Packing of the molecules when viewed down the b axis. The dashed line<br />
represents the hydrogen bond.<br />
Fig.-4: Packing of the molecules when viewed down the c axis. The dashed line<br />
represents the hydrogen bond.<br />
5.6 Conclusion:<br />
3,5-Dibenzoyl-4-(3-methoxyphenyl)-1,4-dihydro-2,6-dimethyl pyridine (DP-7) has<br />
been shown to be a powerful P-gp inhibitor, almost devoid of cardiovascular effects,<br />
but capable of inhibiting liver CYP3A, thus it can be conclude that DP-7 is a good<br />
lead compound for the synthesis of new dihydropyridines. As DP-7 shown promising<br />
MDR activity and looking to the scientific publications of DP-7, studied of X-ray<br />
crystal structure of DP-7 performed.
5.7 Experimental:<br />
5.7.1 Preparation of 1-phenylbutane-1,3-dione<br />
Cool peaces of freshly prepared sodium methoxide (6 gm) at 0 o C using ice cold<br />
water. To that added ethyl acetate (100 ml) slowly and stirred at 0 o C for 10 min. to<br />
that solution added acetophenone (30 ml) drop wise over 45 min and stirred for<br />
another 12 hrs. After completion of reaction filtered the reaction mass, washed with<br />
diethyl ether and dried in rotavap. After that dissolved the crude product in to water<br />
and filter it to removed unwanted crude material. To that filtrate added gl. acetic acid<br />
to set Ph 3. Solid formed was filtered and dried to give titled compound as white<br />
powder (mp. 61 o C).<br />
5.7.2 Synthesis of 3,5-Dibenzoyl-4-(3-methoxyphenyl)-1,4-dihydro-2,6-dimethyl<br />
pyridine(DP-7)<br />
To a solution of 1-phenylbutane-1,3-dione (20mmol) in dry methanol (25ml), 3phenoxybenzaldehyde<br />
(10mmol) and ammonium carbonate (1.5g) was added and the<br />
reaction mixture was refluxed for 18hrs with vigorous stirring. After completion of<br />
the reaction, reaction mixture was cooled to RT and was poured on to ice-water<br />
mixture (100ml) and extracted with dichloromethane (2 x 100ml). The organic<br />
extracts were combined and dried over sodium sulfate and the solvent was removed at<br />
reduced pressure. The residue was subjected to the column chromatography (silica<br />
gel; Hexane-Ethyl acetate, 5:5 v/v) to give titled compound as light yellow crystals<br />
(M.P. 190-192°C).<br />
5.8 Characterization<br />
3,5-Dibenzoyl-4-(3-methoxyphenyl)-1,4-dihydro-2,6-dimethyl pyridine(DP-7)<br />
Ph<br />
O<br />
N<br />
H<br />
O Ph<br />
O<br />
Ph
1<br />
H NMR (400 MHz CDCl3): δ = 7.57-7.53 (m 4H), 7.46-7.42 (m 2H), 7.36-7.31 (m<br />
4H), 7.28-7.24 (m 2H), 7.10-7.02 (m 2H), 6.86-6.84 (m 2H), 6.72-6.70 (d of d 2H, J =<br />
2,2), 6.67 (t 1H, J =2), 5.68 (s 1H), 5.15 (s 1H), 1.92 (s 6H). 13 C NMR (400 MHz<br />
CDCl3): δ = 197.8 (×2), 157.2 (×2), 147.8 (×2), 140.3 (×2), 131.5, 129.8 (×3), 129.2<br />
(×2), 128.4 (×4), 128.2 (×4), 122.8, 122.3, 118.5, 117.9 (×2), 117.1, 112.6 (×2), 43.7,<br />
19.0 (×2). MS (m/z): 485 (M+, 62%), 316 (100%). IR (KBr, cm-1): 3396(N–H<br />
stretching), 3030(C-H stretching, Asymmetric), 2930(C–H stretching, Symmetric),<br />
1703(C=O stretching, ester), 1670(C=O stretching, ketone), 1589(N–H deformation).
5.9 Representative NMR spectra<br />
5.9.1<br />
1 H NMR spectra of bs-DP-7
5.9.2 13 C spectra of bs-DP-7
5.10 References<br />
[1] Fusi F., Saponara S., Valoti M., Dragoni S., D'Elia P., Sgaragli T., Alderighi D., Kawase M.,<br />
Shah A., Motohashi N., Sgaragli G. (2006)Curr. Drug Targets. 8, 949–959.<br />
[2] Bates, S.E., Regis, J.I., Robey, R.W., Zhan, Z., Scala, S., Meadows, B.J. (1994)<br />
Chemoresistance in the clinic: overview. Bull. Cancer 81 (suppl 2), 55–61.<br />
[3] Bellamy, W.T. (1996) Annu. Rev. Pharmacol. Toxicol. 36, 161–183<br />
[4] Saponara S., Kawase M., Shah A., Motohashi N., Molnar J., Ugocsai K., Sgaragli G., Fusi F.<br />
(2004) Br. J. Pharm. 141, 415-422.<br />
[5] Saponara S., Ferrara A., Gorelli B., Shah A., Kawase M., Motohashi N., Molnar J., Sgaragli<br />
G., Fusi F. (2007) Eur. J. Pharmacol. 563, 160–163.<br />
[6] Guengerich, F.B., Brian, W.R., Iwasaki, M., Sari, M.A., Baarnhielm, C., Berntsson, P. (1991)<br />
J. Med. Chem. 34, 1838–1844.<br />
[7] Katoh, M., Nakajima, M., Shimada, N., Yamazaki, H., Yokoi, T. (2000) Eur. J. Clin.<br />
Pharmacol. 55, 843–852<br />
[8] For synthesis and biological activity see (a) Paolo D'Elia , Francesco De Matteis , Stefania<br />
Dragoni , Anamik Shah ,Giampietro Sgaragli, Massimo Valoti. (2009) European Journal of<br />
Pharmacology. 614, 7–13 (b) Masami Kawase, Anamik Shah, Harsukh Gaveriya, Noboru<br />
Motohashi, Hiroshi Sakagami, Andreas Vargae, Joseph Molnar. (2002) Bioorganic &<br />
Medicinal Chemistry. 10, 1051–1055. (c) Prashant S. Kharkar, Bhavik Desai, Harsukh<br />
Gaveria, Bharat Varu, Rajesh Loriya, Yogesh Naliapara, Anamik Shah, Vithal M. Kulkarni.<br />
(2002) J. Med. Chem. 45, 4858-4867<br />
[9] Otwinowski, Z. Minor, W. In: Methods in Enzymology, 276, Carter, C. W. Jr., Sweet, R. M.,<br />
(1997) New York: Academic Press, 307-326.<br />
[10] Sheldrick, G.M. (2008) Acta Cryst., A64, 112-122.<br />
[11] Allen, F.H., Kennard, O., Watson, D.G., Brummer, L., Orpen, A.G., Taylor, R. (1987) J.<br />
Chem. Soc. Perkin Trans, II:S1.<br />
[12] Spek, A.L. (2003) J. Appl. Cryst. 36, 7-13.<br />
[13] Cremer, D., and Pople, J.A. (1975) J. Am. Chem. Soc. 97, 1354-1358.
SUMMARY<br />
The work represented in the thesis entitled “Synthesis and Characterization of New<br />
heterocyclic compounds & their application” is divided into five chapters which can<br />
be summarized as under.<br />
Chapter-1 covers basic introduction to Microwave assisted organic synthesis<br />
including comparison of conventional vs microwave assisted reaction and<br />
introduction of 2-aminoimidazole and their presence as naturally occurring marine<br />
alkaloids described. In this part various synthetic approaches toward 2aminoimidazole<br />
and short review on 2-aminoimidazole as pharmacophores also<br />
presented. Finally basic concept of anti biofilm activity described.<br />
Chapter-2 deals with microwave assisted one pot synthesis and Structure Activity<br />
Relationship of 2-Hydroxy-2-phenyl-2,3-dihydro-imidazo[1,2-a] pyrimidinium Salts<br />
and 2N-Substituted 4(5)-Phenyl-2-Amino-1H-imidazoles as Inhibitors of the Biofilm<br />
Formation by Salmonella Typhimurium and Pseudomonas aeruginosa.<br />
Chapter-3 entitled “Structure Activity Relationship of N1-Substituted 2-<br />
Aminoimidazoles as Inhibitors of Biofilm Formation by Salmonella Typhimurium<br />
and Pseudomonas aeruginosa.” In this chapter a library of N1-substituted 4(5)-phenyl-<br />
2-aminoimidazoles was synthesized and tested for the antagonistic effect against<br />
biofilm formation by Salmonella Typhimurium and Pseudomonas aeruginosa. The<br />
substitution pattern of the 4(5)-phenyl group and the nature of the N1-substituent were<br />
found to have a major effect on the biofilm inhibitory activity. The most active<br />
compounds of this series were shown to inhibit the biofilm formation at low<br />
micromolar concentrations.<br />
Chapter-4 deals with microwave-assisted Cu-catalyzed one pot protocol for the<br />
synthesis of 2-aminoimidazole-triazole framework via two consecutive steps of<br />
dimorth rearrangement and click reaction was demonstrated. Library of 22<br />
compounds have been synthesized and were subjected to test for antibiofilm activity.<br />
However, the antibiofilm activities of these classes of compounds are under pipeline.
After careful study of Structure Activity Relationship, a fresh libraries of N1substituted<br />
2-aminoimidazoles and N1-unsubstituted 2-aminoimidazoles have been<br />
synthesized and tested for anti biofilm activity. In Chapter-4 microwave assisted one<br />
pot protocol for synthesis of 2-aminoimidazole-triazoel framework has been described<br />
and all newly synthesized compounds were tested for antibiofilm activity. However<br />
activities of these calls of compounds are under pipeline.<br />
Chapter-5 entitled “Crystal and molecular structure analysis of DP-7: A new Multi<br />
Drug Resistance Reverter Lead Molecule” deal with crystal and molecular structure<br />
analysis. 3,5-Dibenzoyl-4-(3-methoxyphenyl)-1,4-dihydro-2,6-dimethyl pyridine<br />
(DP-7) has been shown to be a powerful P-gp inhibitor, almost devoid of<br />
cardiovascular effects, but capable of inhibiting liver CYP3A, thus it can be conclude<br />
that DP-7 is a good lead compound for the synthesis of new dihydropyridines. As DP-<br />
7 demonstrated promising MDR activity, several scientific publications on this<br />
molecule appeared. However study of X-ray crystallography was done first time and<br />
presented in the current work.<br />
All newly synthesized compounds have been characterized by 1 H NMR, 13 C NMR<br />
and HRMS. Some representative copy of 1 H and 13 C NMR spectra also presented.
CONFERENCES/SEMINARS/WORKSHOPS ATTENDED<br />
“International Conference On The Interface of Chemistry-Biology In<br />
Biomedical Research” jointly organized by ISCBC and Birla Institute of<br />
Technology & Science, Pilani. February, 22-24, 2008<br />
“National Workshop On Management And Use Of Chemistry Database<br />
And Patent Literature” organized by GUJCOST & Dept. of Chemistry of<br />
<strong>Saurashtra</strong> <strong>University</strong>, Rajkot, (Gujarat), February, 27-29, 2008.<br />
“A National Workshop On Updates In Process And Medicinal Chemistry”<br />
jointly organized by National Facility for Drug Discovery through New<br />
Chemicals Entities Development & Instrumentation support to Small<br />
Manufacturing Pharma Enterprises and DST FIST, UGC-SAP & DST-DPRP<br />
Funded Department of Chemistry, <strong>Saurashtra</strong> <strong>University</strong>, Rajkot March, 3-4,<br />
2009.<br />
“National Conference On Selected Topics In Spectroscopy And<br />
Stereochemistry” organized by the Department of Chemistry, <strong>Saurashtra</strong><br />
<strong>University</strong>, Rajkot, March, 18-20, 2009.<br />
“12th Belgian Organic Synthesis Symposium” (BOSS XII) Namur, Belgium<br />
July 11-16, 2010.
Paper/Poster presented at the International Conference:<br />
“Microwave-Assisted One Pot Synthesis Of Anti-Biofilm Active 2-<br />
Aminoimidazole -Triazole Conjugates Using Copper Nanoparticles”<br />
Bharat S. Savalia, Denis S. Ermolat’ev, Anamik K. Shah and Erik V. Van der<br />
Eycken.“12th Belgian Organic Synthesis Symposium” (BOSS XII) Namur,<br />
Belgium (2010)<br />
“A General Approach To 2-Aminoimidazole Marine Sponge Alkaloids<br />
From Leucetta sp.”<br />
Denis S. Ermolat’ev, Bharat S. Savalia, Jitender B. Bariwal and Erik V. Van<br />
der Eycken,“12th Belgian Organic Synthesis Symposium” (BOSS XII)<br />
Namur, Belgium (2010)<br />
“Crystal Structure Of DP-7: A New MDR Reverting Agent Against<br />
Tumor Cells”<br />
Manisha Parmar, Bharat Savaliya, Harsukh Gaveriya, Lakshminarayana B.N.<br />
J. Shashidhara Prasad, M. A. Sridhar and Anamik Shah. ISCBC.<br />
Lucknow,India, 2010.<br />
“Rapid Synthesis Of Fused Bicyclic Thiazolo-Pyrimidine And Purimido-<br />
Thiazine Derivatives Devoid Of Use Of Catalyst By Microwave Assisted<br />
Method.”<br />
Bharat S.Savaliya, Vijay Virsodia, Punit Rasadia, Nikhil Vekaria, Rupesh<br />
Khunt And Anamik Shah.ISCBC., BITS-Pilani, India.2008
PUBLICATIONS<br />
[1] One-Pot Microwave-Assisted Protocol For The Synthesis Of Substituted 2-<br />
Amino-1H-Imidazoles. Denis S. Ermolat’ev, Bharat Savaliya, Anamik Shah<br />
and Erik V. Van der Eycken. Molecular Diversity. (2010) DOI<br />
10.1007/s11030-010-9270-5<br />
[2] Structure Activity Relationship of 2-Hydroxy-2-phenyl-2,3-dihydro-<br />
[3]<br />
imidazo[1,2-a]pyrimidinium Salts and 2N-Substituted 4(5)-Phenyl-2-Amino-<br />
1H-imidazoles as Inhibitors of the Biofilm Formation by Salmonella<br />
Typhimurium and Pseudomonas aeruginosa. P.L. Steenackers, Denis S.<br />
Ermolat’ev, Bharat Savaliya, Ami De Weerdt, David De Coster, Anamik<br />
Shah, Erik V. Van der Eycken, Dirk E. De Vos, Jozef Vanderleyden and<br />
Sigrid C.J. De Keersmaecker. Bio. & Med. Chem. Submitted (2010)<br />
Structure Activity Relationship of 4(5)-Phenyl-2-amino-1H-imidazoles, N1-<br />
Substituted 2-Aminoimidazoles and Imidazo[1,2-a]pyrimidinium Salts as<br />
Inhibitors of Biofilm Formation by Salmonella Typhimurium and<br />
Pseudomonas aeruginosa. Hans P.L. Steenackers, Denis S. Ermolat’ev,<br />
Bharat Savaliya, Ami De Weerdt, David De Coster, Anamik Shah, Erik V.<br />
Van der Eycken, Dirk E. De Vos, Jozef Vanderleyden and Sigrid C.J. De<br />
Keersmaecker. J. Med. Chem. (2010) DOI: 10.1021/jm1011148<br />
[4] Copper Catalyzed Microwave Assisted One Pot Synthesis of 2-<br />
Aminoimidazole-Triazole Framework. Bharat Savaliya, Denis S. Ermolat’ev,<br />
Anamik Shah and Erik V. Van der Eycken. (2010) Manuscript in preparation.<br />
Org. lett.<br />
[5] Crystal And Molecular Structure Analysis Of DP-7: A New Multi Drug<br />
Resistance Reverter Lead Molecule. Bharat Savaliya, Manisha Parmar,<br />
Vaibhav Ramani, Harsukh Gevariya, B.N. Lakshminarayana, J. Shashidhara<br />
Prashad, M. A. Sridhar and Anamik Shah. (2010) Manuscript in preparation.<br />
[6] Catalyst-Free, Rapid Synthesis of Fused Bicyclic Thiazolo-Pyrimidine and<br />
Pyrimido-Thiazine Derivatives by a Microwave-Assisted Method.<br />
Vijay R. Virsodia, Nikhil R. Vekariya, Atul T. Manvar,Rupesh C. Khunt,<br />
Bhavin R. Marvania, Bharat S.Savalia and Anamik K. Shah. Phosphorus,<br />
Sulfur, and Silicon, 184:34–44 (2009)
Mol Divers<br />
DOI 10.1007/s11030-010-9270-5<br />
FULL-LENGTH PAPER<br />
One-pot microwave-assisted protocol for the synthesis<br />
of substituted 2-amino-1H -imidazoles<br />
D. S. Ermolat’ev · B. Savaliya · A. Shah ·<br />
E. Van der Eycken<br />
Received: 19 May 2010 / Accepted: 7 August 2010<br />
© Springer Science+Business Media B.V. 2010<br />
Abstract An efficient microwave-assisted one-pot two-step<br />
protocol was developed for the construction of disubstituted<br />
2-amino-1H-imidazoles. This process involves the sequential<br />
formation of 2,3-dihydro-2-hydroxyimidazo[1,2-a]pyrimidinium<br />
salts from readily available 2-aminopyrimidines<br />
and α-bromoketones, followed by cleavage of the pyrimidine<br />
ring with hydrazine.<br />
Keywords Heterocycles · 2-Aminoimidazoles ·<br />
Microwave-assisted synthesis · Ring opening ·<br />
Rearrangement<br />
Introduction<br />
The class of 2-aminoimidazoles has recently attracted particular<br />
interest due to various biological properties of these compounds.<br />
2-Aminoimidazole alkaloids and their metabolites,<br />
isolated from the marine sponges Hymeniacidon sp., have<br />
been described as potent antagonists of serotonergic [1] and<br />
histaminergic receptors [2]. Naamine and isonaamine alkaloids<br />
from the marine sponges Leucetta sp. exhibit antiviral<br />
and anticancer activity [3–10]. Because of these interesting<br />
Electronic supplementary material The online version of this<br />
article (doi:10.1007/s11030-010-9270-5) contains supplementary<br />
material, which is available to authorized users.<br />
D. S. Ermolat’ev · B. Savaliya · E. Van der Eycken (B)<br />
Laboratory for Organic and Microwave-Assisted Chemistry<br />
(LOMAC), Department of Chemistry, Katholieke Universiteit<br />
Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium<br />
e-mail: erik.vandereycken@chem.kuleuven.be<br />
B. Savaliya · A. Shah<br />
Department of Chemistry, <strong>Saurashtra</strong> <strong>University</strong>,<br />
Rajkot 360 005, Gujarat, India<br />
N<br />
2<br />
N<br />
N<br />
R 2<br />
R 2<br />
A<br />
R1HN N<br />
B<br />
R1 = H<br />
N<br />
H<br />
1<br />
N<br />
Br<br />
Scheme 1 Synthesis of substituted 2-amino-1H-imidazoles<br />
3<br />
N<br />
N<br />
OH<br />
biological activities, numerous synthetic routes to 1-substituted<br />
and 1-unsubstituted 2-aminoimidazoles have been<br />
reported. Modern synthetic methods for accessing 1-unsubstituted<br />
2-amino-1H-imidazoles can be roughly classified<br />
as heterocyclization of substituted or protected guanidines<br />
with 1,2-dielectrophiles [11,12], heteroaromatic nucleophilic<br />
substitution, and recyclization of 2-aminooxazoles [13].<br />
Although different substituted guanidines are readily available<br />
and can be prepared in situ (e.g., from cyanamides [14]),<br />
the high basicity of guanidines together with non-regioselectivity<br />
often leads to multiple products. Protection by acetyl<br />
[11] and Boc-groups [12] requires, in turn, acidic deprotection<br />
conditions.<br />
Recently, we have described two new approaches to the<br />
synthesis of substituted 2-amino-1H-imidazoles 1. The first<br />
approach is based on the cleavage of imidazo[1,2-a]pyrimidines<br />
[15] 2 with hydrazine (Scheme 1, route A) [16]. In the<br />
second approach, the hydrazinolysis of 2-hydroxy-2,<br />
3-dihydroimidazo[1,2-a]pyrimidinium salts 3 followed<br />
by Dimroth-type rearrangement afforded trisubstituted<br />
2-amino-1H-imidazoles 1 (Scheme 1, route B) [17].<br />
2-Hydroxy-2,3-dihydroimidazo[1,2-a]pyrimidinium salts<br />
3 can be easily prepared from 2-aminopyrimidines 4 with<br />
α-bromoketones 5 under microwave irradiation (Scheme 2).<br />
We found that the outcome of this reaction strongly depends<br />
on the temperature [18]. The microwave-assisted reaction<br />
R 2<br />
R 1<br />
123
Scheme 2 Competitive<br />
formation of 1-unsubstituted<br />
and 1-substituted<br />
2-amino-1H-imidazoles upon<br />
microwave irradiation<br />
Table 1 Investigation of the<br />
condensation under<br />
conventional heating and<br />
microwave irradiation<br />
All reactions were carried out on<br />
a 1 mmol scale of<br />
2-methylaminopyrimidine<br />
(1, R1 = Me) with 1.35 equiv. of<br />
α-phenacylbromide (2, R2 =Ph)<br />
in MeCN (5 mL)<br />
a Isolated yield after<br />
recrystallization from MeCN<br />
N<br />
N<br />
NHMe<br />
N<br />
Br<br />
N<br />
4<br />
5<br />
+<br />
+ Br<br />
NHR 1<br />
O<br />
R 2<br />
MW<br />
O<br />
Ph<br />
4 (R 1 = Me) 5 (R 2 = Ph)<br />
between 2-aminopyrimidines 4 and α-bromoketones 5 performed<br />
at 80–100 ◦ C gave 2-hydroxy-2,3-dihydroimidazo<br />
[1,2-a]pyrimidinium salts 3, while irradiation of the<br />
reaction mixture at temperatures above 100 ◦ C provided<br />
aromatic 1-substituted imidazo[1,2-a ]pyrimidinium salts<br />
6 (Scheme 2). The hydrazinolysis of the salts 3 and 6 leads to<br />
the corresponding 1-unsubstituted and 1-substituted<br />
2-amino-1H-imidazoles 1 and 7. Thus, by performing the<br />
reaction at 130−150 ◦ C, we were able to prepare a library of<br />
1,4,5-trisubstituted 2-aminoimidazoles 7 via a one-pot twostep<br />
protocol [18].<br />
In continuation of our ongoing studies, herein we report<br />
a simple one-pot procedure for the synthesis of 1-unsubstituted<br />
2-amino-1H-imidazoles 1 from 2-aminopyrimidines 4<br />
and α-bromoketones 5 under microwave irradiation.<br />
123<br />
100 °C<br />
N<br />
Br<br />
Conditions<br />
N<br />
N<br />
3<br />
6<br />
N<br />
N<br />
OH<br />
R 2<br />
Br<br />
N<br />
Br<br />
R 2<br />
N<br />
R 1<br />
R 1<br />
3<br />
N<br />
N 2H 4<br />
MW<br />
N 2H 4<br />
MW<br />
N Me<br />
OH<br />
Ph<br />
+<br />
R 1HN<br />
H 2N<br />
N<br />
Mol Divers<br />
N<br />
N<br />
H<br />
N<br />
N<br />
R 1<br />
1<br />
7<br />
Ph<br />
R 2<br />
R 2<br />
N<br />
Br<br />
N Me<br />
Entry Conditions Time (min) T ( ◦ C) 3 (Yield %) a 6 (Yield %) a<br />
1 30 80 64 0<br />
2 60 80 77 0<br />
3 30 100 81 Traces<br />
4 60 100 85 Traces<br />
5 30 120 68 17<br />
6 60 120 53 28<br />
7 MW 30 80 88 0<br />
8 60 80 85 0<br />
9 30 100 48 33<br />
10 60 100 45 35<br />
11 30 120 12 79<br />
12 60 120 Traces 84<br />
Results and discussion<br />
We carefully investigated the formation and dehydratation of<br />
salt 3 resulting in the formation of salt 6 under conventional<br />
heating conditions as well as upon microwave irradiation.<br />
As a proof of concept, the condensation of 2-methylaminopyrimidine<br />
(4,R1 = Me) and α-phenacylbromide (5,R2 = Ph)<br />
was studied (Table 1). A sealed vial containing a solution of<br />
the starting compounds in acetonitrile was conventionally<br />
heated with an oil bath (Table 1, entries 1–6) or irradiated<br />
with microwaves (Table 1, entries 7–12) at different temperatures<br />
for 30–60 min. The formation of the 2-hydroxy<br />
salt 3 was faster under microwave irradiation, and this compound<br />
was obtained in 88% yield within 30 min. Further<br />
increase of the temperature up to 120 ◦ C using conventional<br />
6
Mol Divers<br />
Table 2 Microwave-assisted<br />
synthesis of substituted<br />
2-amino-1H-imidazoles 1<br />
N<br />
Br<br />
N<br />
+<br />
NHR 1<br />
O<br />
R 2<br />
1. MW 80 °C<br />
MeCN 30 min<br />
heating or microwave irradiation led to a mixture of salts 3<br />
and 6 (Table 1). Interestingly, using microwave irradiation at<br />
120 ◦ C for 60 min, we were able to drive the reaction completely<br />
to the formation of the imidazo[1,2-a]pyrimidinium<br />
salt 6 (Table 1, entry 12).<br />
As the transformation of salts 3 into salts 6 is relatively<br />
rapid at the temperatures above 100 ◦ C, the synthesis of<br />
salts 3 was conducted at 80 ◦ C. Treatment of substituted<br />
4<br />
5<br />
N<br />
Br<br />
3<br />
N<br />
N R1 OH<br />
R 2<br />
2. N 2H 4, MW 90 °C<br />
MeCN 10 min<br />
R 1HN<br />
entry 2-aminopyrymidine 4 α–bromoketone 5 product 1 yield<br />
1<br />
2<br />
3<br />
4<br />
5<br />
6<br />
N<br />
N<br />
N<br />
N<br />
N<br />
N<br />
N<br />
N<br />
N<br />
N<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
NH 2<br />
NH 2<br />
NH 2<br />
Me<br />
Piperonyl<br />
N<br />
H<br />
Pr<br />
Br<br />
Br<br />
Br<br />
Br<br />
Br<br />
Br<br />
O<br />
O<br />
O<br />
O<br />
O<br />
O<br />
OMe<br />
Ph<br />
F<br />
Cl<br />
OMe<br />
Cl<br />
Cl<br />
H 2N<br />
H 2N<br />
H 2N<br />
Me<br />
HN<br />
Piperonyl<br />
Pr<br />
HN<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
MeO<br />
N<br />
N<br />
H<br />
HN<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
1{1}<br />
1{2}<br />
1{3}<br />
1{4}<br />
1{5}<br />
1{6}<br />
Ph<br />
F<br />
Cl<br />
OMe<br />
N<br />
N<br />
H<br />
1<br />
R 2<br />
(%) a<br />
2-aminopyrimidines 4 with 15 mol% excess of α-bromoketones<br />
5 in MeCN under microwave irradiation for 30 min<br />
generated the intermediate salts 3 which, in most cases, precipitated<br />
from the reaction mixture upon cooling (Table 2).<br />
Reaction progress was monitored by mass-spectrometry.<br />
In all the cases examined, the reaction appeared to be complete<br />
after 30 min. The cleavage step was performed under<br />
microwave irradiation at 90 ◦ C, using seven equivalents of<br />
Cl<br />
Cl<br />
75<br />
79<br />
88<br />
48<br />
72<br />
70<br />
123
Table 2 continued<br />
9<br />
10<br />
11<br />
12 N<br />
hydrazine hydrate. Based on the data given in Table 2, the<br />
reaction appears to be compatible with both aryl and alkyl<br />
substitutions. All the reactions were clean, smooth, and provided<br />
the products 1{1–18} in good and high yields. The<br />
compounds were purified by column chromatography using<br />
5–10% MeOH in CH2Cl2 as the eluent. All the final 2-amino-<br />
1H-imidazoles 1{1–18} were characterized by 1 H and 13 C<br />
NMR spectroscopy. Their compositions were also confirmed<br />
by HRMS.<br />
123<br />
7<br />
8<br />
13<br />
14<br />
N<br />
N<br />
N<br />
N<br />
N<br />
N<br />
N<br />
N<br />
N<br />
N<br />
N<br />
N<br />
N<br />
N<br />
H<br />
N<br />
H<br />
N<br />
H<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
Octyl<br />
N<br />
H<br />
Pentyl<br />
Hexyl<br />
PMB<br />
Br<br />
Br<br />
Cyclooctyl Br<br />
N<br />
H<br />
N<br />
H<br />
Bu<br />
PMB<br />
Br<br />
Br<br />
Br<br />
Br<br />
Br<br />
O<br />
O<br />
O<br />
O<br />
O<br />
O<br />
O<br />
O<br />
SO 2Me<br />
Br<br />
Cl<br />
Cl<br />
F<br />
SO 2Me<br />
NO 2<br />
Mol Divers<br />
Cl<br />
Pentyl<br />
HN<br />
N<br />
61<br />
N<br />
H 1{9}<br />
Hexyl<br />
HN<br />
HN<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
1{7}<br />
SO 2Me<br />
1{10}<br />
Cl<br />
PMB N<br />
Br<br />
HN<br />
N<br />
H 1{11}<br />
F<br />
SO 2Me<br />
69<br />
44<br />
Cyclooctyl<br />
HN<br />
N<br />
66<br />
N<br />
H 1{12}<br />
Bu<br />
HN<br />
N<br />
83<br />
N<br />
H<br />
1{13}<br />
NO 2<br />
73<br />
Octyl<br />
HN<br />
N<br />
79<br />
N<br />
H<br />
1{8}<br />
PMB<br />
HN<br />
N<br />
89<br />
N<br />
H<br />
1{14}<br />
In conclusion, we have developed a simple and practical<br />
microwave-assisted procedure for the preparation of substituted<br />
2-amino-1H-imidazoles. We have investigated a onepot<br />
synthesis and cleavage of 2-hydroxy-2,3-dihydroimidazo<br />
[1,2-a]pyrimidinyl-4-ium bromides by hydrazine hydrate and<br />
found microwave irradiation to be very effective in this regard.<br />
A small library of 2-amino-1H-imidazoles was synthesized<br />
for screening for potential antiviral and antibacterial<br />
activities.
Mol Divers<br />
Table 2 continued<br />
All the reactions were carried<br />
out on a 4 mmol scale of<br />
2-alkylaminopyrimidine 4 with<br />
1.15 equiv of α-bromoketone 5<br />
in MeCN (3 mL)<br />
a Isolated yield after column<br />
chromatography<br />
Experimental section<br />
Microwave irradiation experiments<br />
15<br />
16<br />
17 N<br />
A monomode CEM-Discover microwave reactor (CEM Corporation,<br />
P.O. Box 200, Matthews, NC 28106) was used<br />
in the standard configuration as delivered, including proprietary<br />
software. All the experiments were carried out in sealed<br />
microwave process vials (10 mL) at the maximum power and<br />
temperature, as indicated in the tables. After completion of<br />
the reaction, the vial was cooled to 50 ◦ C via air-jet cooling<br />
before it was opened.<br />
General procedure for the one-pot two-step microwaveassisted<br />
synthesis of 2-amino-1H-imidazoles 1{1–18}<br />
In a microwave, vial (10 mL) was successively dissolved<br />
in dry MeCN (3 mL), the corresponding 2-aminopyrimidine<br />
(4 mmol) and α-bromoketone (4.6 mmol). The reaction tube<br />
was sealed and irradiated in a microwave reactor at a ceiling<br />
temperature of 80 ◦ C and a maximum power of 50 W for<br />
30 min. After the reaction mixture was cooled with an air<br />
flow for 15 min, hydrazine hydrate (0.9 mL, 28 mmol of a<br />
64% solution, 7 equiv.) was added, and the mixture was irradiated<br />
at a ceiling temperature of 90 ◦ C and a maximum<br />
power of 50 W for another 10 min. After the reaction mixture<br />
was cooled, hydrazine hydrate was removed by distillation<br />
with toluene (3 × 20 mL). The resulting residue was purified<br />
by column chromatography (silica gel; MeOH-DCM 1:9 v/v<br />
with 0.5% of 6 N ammonia in MeOH) to afford 1 as amorphous<br />
solid.<br />
18<br />
N<br />
N<br />
N<br />
N<br />
N<br />
H<br />
N<br />
N<br />
N<br />
N<br />
H<br />
N<br />
H<br />
N<br />
H<br />
Bu<br />
OMe<br />
Br<br />
Br<br />
Br<br />
Br<br />
O<br />
O<br />
O<br />
O<br />
SMe<br />
NO 2<br />
OMe<br />
Bu<br />
HN<br />
HN<br />
OMe<br />
HN<br />
HN<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
N<br />
N<br />
H<br />
1{15}<br />
1{16}<br />
1{17}<br />
1{18}<br />
SMe<br />
NO 2<br />
OMe<br />
Acknowledgments The support for this project was provided by the<br />
Research Fund of the <strong>University</strong> of Leuven and by the F.W.O. (Fund<br />
for Scientific Research—Flanders (Belgium)). E.D.S. is grateful to the<br />
<strong>University</strong> of Leuven for obtaining a postdoctoral fellowship, and S.B.<br />
to Erasmus Mundus External Cooperation Window Lot 15 India<br />
(EMECW15) for obtaining a scholarship. The authors thank Ir.<br />
B. Demarsin for HRMS measurements.<br />
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