Stereochemistry of the reduction of 3β-benzoyloxycholest-5-en-4-one with sodium borohydride

Abstract

Reduction of 3β-benzoyloxycholest-5-en-4-one (3) with sodium borohydride under various conditions affords only minor amounts of 3β-benzoyloxycholest-5-en-4β-ol (2a). The major product is the 4α-isomer (6). Using sodium borodeuteride it has been shown that the 3β-benzoyloxycholest-5-en-4β-ol obtained is deuteriated at the 3α-position in relatively alkaline conditions, but at 4α- under conditions near neutrality. A plausible mechanism has been proposed for this interesting result.