Solvent free, catalytic and diastereoselective preparation of aryl and alkyl thioglycosides as key components for oligosaccharide synthesis.

A new and environmentally friendly protocol for the conversion of sugar per-acetates into thioglycosides under solvent free and catalytic conditions is presented. The procedure involves heating in the presence of InCl 3 and various aryl thiols. For alkyl thioglycoside synthesis, cyclohexane thiol was found to give good results and yield a glycosyl donor with reactivity similar to a thioethyl congener. The established optimum reaction conditions were found to provide the desired thioglycoside products in an easy and highly diastereoselective manner even when conducted on a multigram scale.