Novel Regioselective Glycosylations for the Convergent and Chemoselective Assembly of Oligosaccharides

A novel convergent chemoselective glycosylation methodology based on differences in reactivity between hydroxyl groups of a glycosyl donor and an acceptor was established. A series of di- and trisaccharides were synthesised in good to excellent yields which can be employed as acceptors in a subsequent glycosylation without the need to perform protecting group interconversions. The effectiveness of this methodology has been demonstrated in a highly convergent one-pot multi-step glycosylation yielding 1-4 and 1-6 linked tetra- and hexasaccharide.