A Novel Strategy for the Synthesis of Bromo-Substituted Cholestenone and its New Application to a Synthesis of 1α-Hydroxycholesterol

Abstract

A novel and efficient method was developed for the preparation of bromo-substituted cholestenone, including 6β-bromocholestenone and 2 α,6 β-dibromocholestenone. The key step in this synthesis is a very mild method for the transformation of 5 α,6 β-dibromocholesterol into the 6 β-bromocholestenone by treatment with NaClO/NaBr/TEMPO, followed by dehydro-bromination with Et3N. Bromination at C-2 with NBS/BPO (benzoyl peroxide) gave the 2 α,6 β-dibromo cholestenone. This was used in a synthesis of 1 α-hydroxycholesterol.