Glycosylation of steroids with silver silicate and 2-deoxy-2-fluoro-α-D-glucopyranosyl bromide triacetate

Abstract

Glycosylation with the title glycosyl bromide I in 1,2-dichloroethane in the presence of silver silicate and a molecular sieves afforded mixtures of 3,4,6-tri-O-acetyl-2-deoxy-2-fluoro-α- and β-D-glucopyranosides (V-X), derived from ethyl (20E)-3β-hydroxy-24-nor-5,20(22)-choladien-23-oate (II), (20E)-3β-hydroxy-5β-pregn-20-ene-21-carboxylate (III) and 3β, 14-dihydroxy-5β, 14β-card-20(22)-enolide (IV, digitoxigenin), in which the β-anomers predominated. Separation and deacetylation furnished the corresponding 2-deoxy-2-fluoroglucosides XI-XVI.