Use of Acyclic Glycosyl Donors for Furanoside Synthesis

Abstract

Treatment of the peracetylated ethyl dithioacetals of d-glucose, d-galactose, and d-mannose with acetyl chloride and boron trifluoride diethyl etherate at reflux yields the known acyclic 1-chloro-1-(ethylthio) derivatives. These compounds are shown to effectively glycosylate a variety of carbohydrate acceptors using silver trifluoromethanesulfonate as the promotor, affording stereospecifically the corresponding acyclic O,S-acetals in good to excellent yield. Furthermore, following deacetylation, treatment of these O,S-acetals with a mixture of mercuric salts in either methanol or dimethylformamide gives rise to disaccharides terminating in d-furanosyl residues.