Facile triflic acid-catalyzed α-1,2--thio glycosylations: scope and application to the synthesis of -linked oligosaccharides, glycolipids, sublancin glycopeptides, and T/T antigens.

Studies of -linked glycoconjugates have attracted growing interest because of their enhanced chemical stability and enzymatic resistance over -glycoside counterparts. We here report a facile approach to access α-1,2--linked glycosides using triflic acid as a catalyst to promote the glycosylation of a series of thiols with d-glucosamine, galactosamine, glucose, and galactose electrophiles. This method is broadly applicable for the stereoselective synthesis of -linked glycopeptides, oligosaccharides and glycolipids in high yield and excellent α-selectivity. Many of the synthetic limitations associated with the preparation of these -linked products are overcome by this catalytic method.