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

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 α-(1→4)-GalpNAc repeat, and a branching β-Glcp residue. In this paper, we describe a strategy for the stereoselective construction of the α-(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 α-GalpNAc-(1→4)-α-GalpNAc-(1→4)-[β-Glcp-(1→3)]-α-GalpNAc(1→4)-α-GalpNAc-(1→4)-GalpNAc.