Coupling of glycal derived thioethyl glycosyl donors with glycal acceptors. An advance in the scope of the glycal assembly

Glycals were converted into thioethyl glycosyl donors through 1,2-anhydrosugar intermediates. Various participating groups in the C-2 position were examined for formation of beta-glucosyl, beta-galactosyl, and alpha-mannosyl linkages. A number of disaccharides was prepared employing a novel coupling protocol involving thioethyl 2-pivaloyl glycosyl donors and glycal accepters. Using this methodology, a linear tetrasaccharide containing exclusively beta-glucosyl-(1-->4) linkages was prepared in high yields. Ready application to alpha-mannosylation and C2 branching are other hallmarks of the method.