Synthesis of deuterated ent-beyeranes. Stereospecific reduction of a 4-axial aldehyde

Abstract

Reduction of the 4a-axial aldehyde group in ent-3,19-dioxobeyer-15-en-17-oic acid (1) by sodium borohydride is shown to occur by attack on the Si-face of the carbonyl group. The synthesis of some ent-beyerane derivatives stereospecifically labelled with deuterium at C19 is described.