Potential bile acid metabolites. 20. A new synthetic route to stereoisomeric 3,6,-dihydroxy- and 6-hydroxy-5α-cholanoic acids

An improved procedure for the syntheses of stereoisomeric 3,6,-dihydroxy- and 6-hydroxy-5α-cholanoic acids (and their methyl esters) is described. The principal reactions emplyoed are those reported in the preceding paper of this series, with the commercially available hyodeoxycholic acid as starting material. The final step in the procedure is the reduction of the key 5α C-6 ketones with either the stereoselective equatorial reagent, Li/NH₃/MeOH, or the axial reagent, Zn(BH₄)₂). The results of analysis of the prepared 6-monohydroxylated and 3,6-dihydroxylated stereoisomers by thin-layer chromatographic, high performance liquid chromatographic and gas-liquid chromatographic mobilities, and ¹H and ¹³C nuclear magnetic resonance spectra are discussed along with the dat for the corresponding compounds in the 5β-series. (Steroids 58: 362-369, 1993).