Unsaturated steroids. Part 6. A route to cholesta-5,7-diene-1α,3β-diol; preparation of steroidal 4,6,8(14)-trienes

Abstract

Bromination of 5α-cholest-7-en-3-one to give the corresponding 2ζ,4ζ-dibromo-derivative followed by dehydro-bromination gives cholesta-1,4,7-trien-3-one (3). The corresponding cholesta-1,3,5,7-tetraen-3-yl acetate (4) was converted by the method of Kaneko et al. into the adduct of cholesta-1,5,7-trien-3β-ol with 4-phenyl-1,2,4-triazoline-3,5-dione. The corresponding dimethyl-t-butylsilyl ether was transformed into the 1α,2α-epoxide, which was readily converted into cholesta-5,7-diene-1α,3β-diol (8). Treatment of the adduct from a steroidal 5,7-dien-3-one and 4-phenyl-1,2,4-triazoline-3,5-dione with boron trifluoride–ether yields the corresponding 4,6,8(14)-trien-3-one (10).