A new method for α-specific glucosylation and its application to the one-pot synthesis of a branched α-glucan

Abstract

A new, versatile, and highly efficient α-specific glucosylation method was developed based on the synergistic α-directing effects of a TolSCl/AgOTf promoter system to effect glycosylation at a low temperature using thioglycoside donors and the steric β-shielding or the remote participation of protecting groups at the donor 6-O-position. This novel method was examined with a diversity of glycosyl acceptors to show its broad applicability. It was then employed for the first time to achieve a one-pot, stereospecific assembly of a complex α-glucan heptasaccharide of a Pseudallescheria boydii polysaccharide containing both α-(1 → 4) and α-(1 → 6) glucosyl linkages.