Improved syntheses of aromatase inhibitors and neuroactive steroids efficient oxidations and reductions at key positions for bioactivity

An Henbest reduction, followed by the preparation of a silyl enol ether and oxidation in situ with m-CPBA has led to the neurosteroids 3 alpha-hydroxy - and 3 alpha,21-dihydroxy-5 alpha-pregnanolones. Using testosterone as sta rting material, a new short synthesis of an aromatase inhibitor, 4-OHA, has been achieved through hydroboration/oxidation followed by a Swern type oxi dation and epimerization. Another aromatase inhibitor, androst-4-ene-3,6,17 -trione, has been efficiently prepared using PCC on montmorillonite K10, un der ultrasonic irradiation. (C) 1999 Elsevier Science Ltd. All rights reser ved.