A Route to Carbasugar Analogues - Jonathan Clayden - The ...

Experimental for chapter 4.1
Synthesis of (1R,2S,5S,6S)-5-((4R,5R)-4,5-diphenyloxazolin-2-yl)-6-isopropyl-5-
methylcyclohex-3-ene-1,2-diol (287)
Ph Ph
Ph Ph Ph Ph
O
N
O
N
O
N
O
OH
CeCl 3. 7H 2 O, NaBH 4
1
MeOH, 0 °C
OH
OH
213 287
6
5
2
3
4 OH
OH
Sodium borohydride (24 mg, 0.63 mmol) was added portion wise to a stirred solution
of enone 276 (100 mg, 0.26 mmol) and cerium trichloride heptahydrate (97 mg, 0.26
mmol) in methanol (0.6 cm 3 ) at 0 °C. When judged complete by TLC (PMA stain c.
20 min) ammonium chloride (sat. aqueous) was added to the cooled reaction mixture
until. The solvent was removed from the reaction mixture, which was partitioned
between water (3 cm 3 ) and CH 2 Cl 2 (10 cm 3 ) and the aqueous layer further washed (2 x
10 cm 3 CH 2 Cl 2 ) and the combined organic layers washed with brine before being dried
over sodium sulphate. Removal of solvent gave a mixture of diols 213 and 287 (100
mg, 99%, 10:1 mixture) which were separated by recrystallisation from Et 2 O and
forming the acetonide of 287.
213 – see page 250
287 R f : 0.23 (2:1, petrol:EtOAc); [α] 22 D : +216 (c = 0.5, CHCl 3 ); MS m/z (CI+) 410
(100%, MH + ), 411 (23%, (M+1)H + ); HRMS: found 432.2146, MNa requires
432.2145; IR ν max (film)/cm⎯¹ 3359 (br), 2923 (m), 1639, 1451 (m), 1382, 1258; ¹H-
NMR (CD 3 OD, 500 MHz) 7.43-7.30 (m, 8H, Ph), 7.27-7.23 (m, 2H, Ph), 5.92 (dd, 1H,
J 5.0, 10.0, H5), 5.72 (d, 1H, J 10.0, H6), 5.24 (d, 1H, J 10.5, CHOPh), 5.02 (d, 1H, J
10.5, CHNPh), 4.21 (dd, 1H, J 12.0, 4.5, H3), 4.06 (t, 1H, J 4.5, H4), 2.73 (sept, 1H, J
7.0, CHMe2), 1.84 (d, 1H, J 12.0, H2), 1.48 (s, 3H, Me), 1.19 (d, 3H, J 7.0,
CHMe A Me B ), 1.12 (d, 3H, J 7.0, CHMe A Me B ); ¹³C-NMR (CDCl 3 , 125 MHz) δ 169.5
(C=N), 140.9 (ipso-Ph), 138.9 (ipso-Ph), 137.5 (C5), 128.8 (C6), 128.7, 128.5, 127.7,
126.8 , 126.1, 125.7 (Ph), 90.0 (CHOPh), 78.0 (CHNPh), 69.0 (C3), 66.7 (C4), 48.7
(C2), 44.2 (C1), 26.7 (Me), 26.4 (CHMe 2 ), 26.0 (Me), 17.5 (CHMe a Me b ).
251