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

Abstract

Reduction reactions of cholest-4-en-3-one derivatives bearing the phenylsulfonyl or phenylsulfanyl group at C-4 with various metal hydrides are studied. Lithium aluminohydride reduction of 4-(phenylsulfonyl)cholest-4-en-3β-ol 13a and 4-(phenylsulfonyl)cholest-4-en-3α-ol 15a occurs with saturation of the double bond and deoxygenation to give 4β-phenylsulfonyl-5β-cholestane 8 and 4α-phenylsulfonyl-5α-cholestane 7a, respectively. Reduction of 4-(phenylsulfonyl)cholest-4-en-3-one 2 with lithium aluminohydride yields compound 8. Reduction of compounds 2, 13a and 15a with other metal hydrides affords mixtures of diastereomeric products. Metal hydride reductions of 4-(phenylsulfanyl)cholest-4-en-3-one 1 affect the carbonyl group only. Catalytic hydrogenation of compound 2 gives a mixture of 5α- and 5β- dihydro derivatives. Mechanistic and stereochemical aspects of the reduction reactions are discussed.