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 β-glucosyl, β-galactosyl, and α-mannosyl linkages. A number of disaccharides was prepared employing a novel coupling protocol involving thioethyl 2-pivaloyl glycosyl donors and glycal acceptors. Using this methodology, a linear tetrasaccharide containing exclusively β-glucosyl-(1→4) linkages was prepared in high yields. Ready application to α-mannosylation and C2 branching are other hallmarks of the method.