On reduction of alpha,beta-unstaurated ketones and the respective allylic alcohols, bearing a phenylsulfonyl or phenylsulfanyl group in the alpha position. Hydroxy group-controlled stereoselective reduction of 3 alpha- and 3beta-hydroxy-4-(phenylsulfonyl)cholest-4-ene

Reduction reactions of cholest-4-en-3-one derivatives bearing the phenylsul fonyl or phenylsulfanyl group at C-4 with various metal hydrides are studie d. Lithium aluminohydride reduction of 4-(phenylsulfonyl)cholest-4-en-3 bet a-ol 13a and 4-(phenylsulfonyl)cholest-4-en-3 alpha-ol 15a occurs with satu ration of the double bond and deoxygenation to give 4 beta-phenylsulfonyl-5 beta-cholestane 8 and 4 alpha-phenylsulfonyl-5 alpha-cholestane 7a, respec tively. Reduction of 4-(phenylsulfonyl)cholest-4-en-3-one 2 with lithium al uminohydride yields compound 8. Reduction of compounds 2, 13a and 15a with other metal hydrides affords mixtures of diastereomeric products. Metal hyd ride reductions of 4-(phenylsulfanyl)cholest-4-en-3-one 1 affect the carbon yl group only. Catalytic hydrogenation of compound 2 gives a mixture of 5 a lpha- and 5 beta- dihydro derivatives. Mechanistic and stereochemical aspec ts of the reduction reactions are discussed.