A novel method for stereospecific generation of natural C-17 stereochemistry and either C-20 epimer in steroid side chains by palladium-catalyzed hydrogenolysis of C-17 and C-20 allylic carbonates.
alcohol, obtained by the reaction of C-17-keto steroid with isopropenyllithium, was converted to carbonate. Its hydrogenolysis with triethylammonium formate affords C-17β-isopropenyl group. Steroid side chain units were introduced by the reaction of C-20 keto steroid with (E) and (Z) alkenyl lithiums. The natural epimer at C-20 in steroidside-chains was generated stereospecifically by the palladium-catalyzed