反应详情

A suspension of LiA1H4 (0.06 g, 3 mols. equiv.) in dry THF (25 ml) was stirred under nitrogen whilst standing in an ice/methanol bath. Methyl cholate (5a) (0.22 g, 0.52 mmol) in dry THF (10 ml) was then added dropwise and the resultant mixture stirred at ambient temperature overnight. Water was then introduced carefully to the mixture until all the excess LiA1H4 ad been destroyed. The resultant mixture was acidified with 2M HCl and extracted into EtOAc (3×). The combined organic extracts were washed with water (2×), dried and evaporated to give a white solid (0.17 g, 83%). Recrystallisation of 0.11 g from ethyl acetate afforded pure 3α,7α,12α,24-tetrahydroxy-5β-cholane (7a)7 (40 mg., 31%): m.p. 226°-227° and 231°-234° C. [Lit.7 226°-227° C.]; 1H nmr (90 MHz; CDCl 3 /DMSO d6) δ 0.64 (3H, s, 18-CH3), 0.85 (3H, s, 19-CH3), 3.0-3.6 (4H, m [exchanges on adding D2O], 3α-,7α-,12α- and 24- OH's), 3.0-3.6 (1H, m, 3β-H), 3.35-3.55 (2H, t[broadened], 24-CH2), 3.6-3.8 (1H, m, 7β-H), 3.8-4.0 (1H, 12β-H); IR (KBr) 3382 (OH's) cm-1.

1. customwhilst standing in an ice/methanol bath
2. custombeen destroyed
3. extractionextracted into EtOAc (3×)
4. washThe combined organic extracts were washed with water (2×)
5. customdried
6. customevaporated