Preparation of 24(R)- and 24(S)-5beta-cholestane-3alpha,7alpha,24-triols and 25(R)- and 25(S)-5beta-cholestane-3alpha,7alpha,26-triols by a hydroboration procedure.

This report describes a new and convenient method for the preparation of 5beta-cholestane-3alpha,7alpha,24-triol (24R and 24S) and 5beta-cholestane-3alpha,7alpha,26-triol (25R and 25S) starting from 5beta-cholestane-3alpha,7alpha,25-triol. Dehydration of the latter with acetic anhydride and glacial acetic acid yielded a mixture of 5beta-cholest-24ene-3alpha,7alpha-diol and the corresponding delta25 compound. Hydroboration and oxidation of the delta24 unsaturated bile alcohol resulted in the formation of 5beta-cholestane-3alpha,7alpha,24-triol. 5beta-Cholestane-3alpha,7alpha,26-triol and 5beta-cholestane-3alpha,7alpha-diol were obtained from the delta25 bile alcohol. In each case the bile alcohols epimeric at C-24 and C-25 were resolved by analytical and preparative thin-layer chromatography and characterized by gas-liquid chromatography, infrared-, proton magnetic resonance-, and mass spectrometry. Tentative assignment of the 24R, 24S and 25R, 25S configurations was made on the basis of molecular rotation differences. These epimeric bile alcohols will be useful for biological studies of chenodeoxycholic acid biosynthesis.