C-26-ANALOGS OF NATURALLY OCCURRING BILE ALCOHOLS .2. PREPARATION OF 24-NOR-5-BETA-CHOLESTANE-3-ALPHA, 7-ALPHA, 12-ALPHA, 23-TETROLS (23R AND 23S) AND 24-NOR-5-BETA-CHOLESTANE-3-ALPHA, 7-ALPHA, 12-ALPHA, 26-TETROLS (25R AND 25S) BY A HYDROBORATION PROCEDURE

A convenient procedure for the synthesis of 24-nor-5.beta.-cholestane-3.alpha.,7.alpha.-12.alpha.,23-tetrol (23R and 23S) and 24-nor-5.beta.-cholestane-3.alpha.,7.alpha.,12.alpha., 26-tetrol (25R and 25S) starting from 24-nor-5.beta.-cholestane-3.alpha.,7.alpha.,12.alpha.,25-tetrol was developed. Dehydration of 24-nor-5.beta.-cholestane-3.alpha.,7.alpha.,12.alpha.,25-tetrol with glacial acetic acid and acetic anhydride yielded a mixture of 24-nor-5.beta.-cholest-23-ene-3.alpha.,7.alpha.,12.alpha.-triol and the corresponding .DELTA.25 compound. Hydroboration and oxidation of the mixture of unsaturated nor-triols resulted in the formation of 24-nor-5.beta.-cholestane-3.alpha.,7.alpha.,12.alpha.,23-tetrols (23R and 23S) and 24-nor-5.beta.-cholestane-3.alpha.,7.alpha.,12.alpha.,26-tetrols (25R and 25S). Smaller amounts of 24-nor-5.beta.-cholestane-3.alpha.,7.alpha.,12.alpha.,22.epsilon.-tetrol and 24-nor-5.beta.-cholestane-3.alpha.,7.alpha.,12.alpha.-triol were also obtained. The C26 bile alcohols epimeric at C-23 and C-25 were resolved by analytical and preparative TLC and characterized by GLC and mass spectrometry. Provisional assignment of the configurations of the C-23 and C-25 hydroxyl groups were made on the basis of molecular rotation differences. These C26 alcohols will be used to test the stereospecificity of the hepatic enzymes that promote oxidation of the cholesterol side chain.