(1R)-2,3,4,6-Tetra-O-benzyl-1-C-allyl-1-deoxy-1-C-(2-thiazolyl)-D-galactopyranose

We have previously reported that thiazolylketol acetates, synthesized by the addition of 2-lithiothiazole to sugar lactones followed by acetylation, are efficient glycosyl donors affording O-, N-, P-, and C-glycosides. After the first example of C-glycosidation recently described by us, we report here on the unexpected outcome of the reaction of a thiazolylketol acetate with allyltrimethylsilane in the presence of trimethylsilyl triflate. The obtained intermediate, an intramolecular N-thiazolium salt, could be stereoselectively converted into the desired allyl C-thiazolylketoside.