]A potentially versatile synthesis of glycosides

Phenyl 1-thio-D-glucopyranosides in the presence of mercury(II) salts are readily solvolysed to give alkyl D-glucopyranosides with inverted anomeric configuration. Methanolyses of the β and α anomers afford the methyl α and β-glycosides which were isolated in yields of 74 and 87%, respectively; n.m.r. examinations indicated that, whereas the β-glycoside was produced stereospecifically, the α-glycoside was formed together with ≈6% of its β isomer. The approach can be extended to the synthesis of complex glycosides (the α anomers of which are of special interest) as was illustrated by the preparation of cholestanyl and 1-naphthyl α-D-glucopyranoside and a disaccharide derivative.