反应详情

A suspension of LiA1H4 (0.15 g, 3 mols. equiv.) in dry THF (25 ml) was stirred under nitrogen whilst standing in an ice/methanol bath. Methyl deoxycholate (5b) (0.5 g, 1.2 mmol) in dry THF (30 ml) was then added dropwise and the resultant mixture stirred at ambient temperature for 2.5 hours. Water was then introduced carefully to the mixture until all the excess LiA1H4 had 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 foam (0.47 g, 100%). Recrystallisation of 0.41 g from ethyl acetate afforded pure 3α,12α,24-trihydroxy-5β-cholane (7b)8 (0.30 g, 73%): m.p. 110°-116° C. [Lit8 107°-114° C.); 1H nmr (90 MHz; CDCl3 /DMSO d6) δ 0.67 (3H, s, 18-CH3), 0.90 (3H, s, 19-CH3), 3.2-3.7 (1H, m, 3β-H), 3.4-3.6 (2H, t(broadened), 24-CH2), 3.8-4.0 (1H, m, 12β-H); IR (KBr) 3366 (OH's) cm-1.

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