β-Glucosides of steroidal unsaturated nitriles

Abstract

Reaction of 3β-methoxymethoxy-5-pregnen-20-one (Ia) with diethyl cyanomethylphosphonate and subsequent removal of the protecting group afforded (20E)-3β-hydroxy-24-norchola-5,20(22)-diene-23-nitrile (IIIa). Besides the analogous derivative IIIb with another double bond in position 14, the fully saturated compounds IIIc and IIId with configuration 5α and 5β, respectively, were prepared similarly. Silver silicate-catalyzed glycosylation of IIIa-IIId with tetra-O-acetyl-α-D-glucopyranosyl bromide gave β-D-glucopyranosides IVa-IVd in 77-89% yield. A parallel series of hemisuccinates VIa-VId was prepared in 64-81% yields by reaction of IIIa-IIId with 2-(trimethylsilyl)ethyl hydrogen butanedioate followed by deblocking with tetrabutylammonium fluoride. The glucoside IVa was prepared also by an alternative reaction pathway starting from 3β-hydroxy-5-pregnen-20-one (VIII). Compound VIII was converted in 80% yield into the glucoside IX which, after protection as the tetra-O-(trimethylsilyl)derivative XII, was treated with diethyl cyanomethylphosphonate.