A stereoselective 1,2-cis glycosylation toward the synthesis of a novel N-linked glycan from the Gram-negative bacterium, Campylobacter jejuni

Abstract

It has been shown that certain prokaryotes, such as Campylobacter jejuni, have asparagine (Asn)-linked glycoproteins. However, the structures of their glycans are distinct from those of eukaryotic origin. They consist of a bacillosamine residue linked to Asn, an alpha-(1-->4)-GalpNAc repeat, and a branching beta-Glcp residue. In this paper, we describe a strategy for the stereoselective construction of the alpha-(1-->4)-GalpNAc repeat of a C. jejuni N-glycan, utilizing a pentafluoropropionyl (PFP) group as a temporary protective group of the C-4 OH group of the GalpN donor. The strategy was applied to the synthesis of the hexasaccharide alpha-GalpNAc-(1-->4)-alpha-GalpNAc-(1-->4)-[beta-Glcp-(1-->3)]-alpha-GalpNAc(1-->4)-alpha-GalpNAc-(1-->4)-GalpNAc.