Direct dehydrative pyridylthio-glycosidation of unprotected sugars in aqueous media using 2-chloro-1,3-dimethylimidazolinium chloride as a condensing agent

Various 2-pyridyl 1-thioglycosides, important synthetic intermediates and enzyme inhibitors in sugar chemistry, have been synthesized directly from the corresponding unprotected sugars in good yields by using 2-chloro-1,3- dimethylimidazolinium chloride (DMC) as dehydrative condensing agent. The reaction proceeds in aqueous media without using any protecting groups, affording 2-pyridyl 1-thioglycosides with β-configuration selectively. According to the present method, not only unprotected monosaccharides but also unprotected oligosaccharides, such as cello-oligosaccharides, chito-oligo-saccharides, malto-oligosaccharides, and glucosamine oligomers, can be converted to the corresponding 2-pyridylthio derivatives, which would greatly expand the utility of aryl 1-thioglycosides in sugar chemistry.