Steroid analogues. Part 1. Preparation of intermediates containing rings C and D

Abstract

(±)-7β-Hydroxy-6β-methyl-trans-bicyclo[4.3.0]nonan-3-one (6) and (±)-rel-(1R,6R,7R)-7-[(1R)-1-hydroxyethyl]-6-methylbicyclo[4.3.0]nonan-3-one (10), key intermediates for the synthesis of 6,7-dinor-5,8-secoestr-9-enes, were prepared from (±)-6-methyl-trans-bicyclo[4.3.0]nonane-3,7-dione (4). Reduction of (4) with a modified Henbest reagent (hexachloroiridic acid–trimethyl phosphite–triethylamine–aqueous propan-2-ol) gave (±)-3α-hydroxy-6β-methyl-trans-bicyclo[4.3.0]nonan-7-one (13) as the major product; with Lalancette's reagent (sulphurated sodium borohydride) the (±)-3β-hydroxy-epimer (15) was formed. Surprisingly, reduction of (±)-6-methyl-cis-bicyclo[4.3.0]nonane-3,7-dione (19) with either the Henbest or the Lalancette reagent gave (±)-3α-hydroxy-6β-methyl-cis-bicyclo[4.3.0]nonan-7-one (20).