Ring contraction of glycopyranosyl enamines: an easy route to furanoid thioglycosides of 5-aminosugars

The reaction of glycohexapyranosyl enamines, having 2- and 3-hydroxyl groups in a cis-relationship with 2,2-dimethoxypropane, induces ring contraction of the sugar ring with formation of 2,3-O-isopropylidene furanoid glycosylenamines. 5-O-Mesylation of these compounds, followed by formation of anhydroazasugars and nucleophilic ring opening, with thiols, produces alkyl and aryl thiofuranosides of 5-aminosugars [Copyright &y& Elsevier]