POTENTIAL BILE-ACID METABOLITES .19. THE EPIMERIC 3-ALPHA,6,7-BETA-TRIHYDROXY-5-ALPHA-CHOLANOIC AND 3-ALPHA,6,7-BETA,12-ALPHA-TETRAHYDROXY-5-ALPHA-CHOLANOIC ACIDS

Syntheses by a new procedure of the known 3alpha,6alpha,7beta- and 3alpha,6beta,7beta-trihydroxy-5alpha-cholanoic acids, and of the once-reported analog 3alpha,6alpha,7beta,12alpha-, as well as the new 3alpha,6beta,7beta,12alpha-tetrahydroxy-5alpha-cholanoic acids, are described. Key intermediates of the syntheses are the 6-oxo-7beta-ols of the respective 5alpha-cholanoic acids (and their methyl esters) prepared by allomerization at C-5 of appropriate 6-bromo-7-oxo derivatives of the corresponding 5beta-acids. Successful reduction of the 6,7-ketols to the desired products depended on the proper choice of reagents, either Zn(BH4)2 or Li/NH3/MeOH.