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 chenodeoxycholate (5c) (0.5 g, 1.2 mmol) in dry THF (30 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 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 0.27 g from dichloromethane afforded pure 3α,7α,24-trihydroxy-50-cholane (7c)3 (0.16 g, 59%): m.p. 116°-118° C. [Lit. 9a 150° C.; also reported as an amorphous solid9b ]; 1H nmr (90 MHz; CDCl3 /DMSO d 6) δ0.64 (3H, s, 18-CH3), 0.88 (3H, s, 19-CH3), 2.9-3.2 (2H, s (exchanges on adding D2O], OH's, 3.1-3.6 (1H, m, 3β-H), 3.4-3.6 (2H, t[broadened), 24-CH2), 3.6-4.0 (1H, m[exchanges on adding D2O], OH), 3.7-3.9 (1H, m, 7β-H); IR (KBr) 3420 (OH's) cm-1 ; MS: Found m/z 378.3130; C24H42O3 (M) requires m/z 378.3134.

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
7. customto give a white foam (0.47 g. 100%)
8. customRecrystallisation of 0.27 g from dichloromethane afforded pure 3α,7α,24-trihydroxy-50-cholane (7c)3 (0.16 g, 59%)
9. customLit. 9a 150° C.
10. addition1H nmr (90 MHz; CDCl3 /DMSO d 6) δ0.64 (3H, s, 18-CH3), 0.88 (3H, s, 19-CH3), 2.9-3.2 (2H, s (exchanges on adding D2O], OH's, 3.1-3.6 (1H, m, 3β-H), 3.4-3.6 (2H
11. additiont[broadened), 24-CH2), 3.6-4.0 (1H, m[exchanges on adding D2O], OH), 3.7-3.9 (1H, m, 7β-H)