Syntheses of acetylated steroid glycosides and selective cleavage of O-acetyl groups in sugar moiety

Abstract

Acetylated 3β- O-β-glycosyl steroid derivatives were synthesized by the reaction of a new polyhydroxysteroid 3β,5α,6β-trihydroxypregn-16-en-20-one ( 2) with the peracetylated 1-bromo derivatives of d-glucose and d-galactose, respectively. Subsequent protection by excess acetic anhydride in pyridine selectively gave the 6β- O-acetylated steroid glycosides. Deprotection of the acetylated steroid glycosides separately with moderate catalysis dibutyltin oxide in methanol selectively removed all acetyl groups of sugar moiety, whereas the acetyl group of the steroid part was retained. The structures of the steroid glycosides were confirmed by mass spectrometry, NMR and IR. The complete protocol was shown to be non-destructive at all stages to the sugar moieties and the steroid nucleus. These regioselective reactions open a route to the synthesis of a series of closely related isomers of 2 and other widespread polyhydroxysteroids and steroid glycosides in marine organisms and some terrestrial species.