Synthesis of a Glycopeptide Containing Oligosaccharides: Chemoenzymatic Synthesis of Eel Calcitonin Analogues Having Natural N-Linked Oligosaccharides

We describe a novel chemoenzymatic synthesis of eel calcitonin (eCT) glycopeptide analogues having natural N-linked oligosaccharides, such as a disialo biantennary complex-type [(NeuAc-Gal-GlcNAc-Man) 2 -Man-GlcNAc 2 ], an asialo complex-type [(Gal-GlcNAc-Man) 2 -Man-GlcNAc 2 ], and a high-mannose type [Man 6 -GlcNAc 2 ] as model compounds for glycoprotein synthesis. First, a glycoprotein containing N -acetylglucosamine (GlcNAc) was prepared by a chemical synthesis. Next, natural oligosaccharides were added to the prepared glycopeptide containing GlcNAc by a transglycosylation reaction using endo-β- N -acetylglucosaminidase (endo-β-GlcNAc-ase) from Mucor hiemalis .