Chemoenzymatic syntheses of (25R)- and (25S)-25-hydroxy-27-nor-cholesterol, a steroid bearing a secondary hydroxy group in the side chain

(25R)- and (25S)-25-hydroxy-27-nor-cholesterol 1c, were prepared by enzymatic resolution of the stereogenic center in the side chain of compound 4a or by synthesis of the side chain using, as a chiral synthon, the enantiomerically pure phenylsulfonyl alkanol 6a prepared by different biocatalytic approaches. (C) 1999 Elsevier Science Ltd. All rights reserved.