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-GlcNAc2], an asialo complex-type [(Gal-GlcNAc-Man)2-Man-GlcNAc2], and a high-mannose type [Man6-GlcNAc2] 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.