We describe a novel chemoenzymatic synthesis of eel calcitonin (eCT) glycopeptide analogues having natural N-linked oligosaccharides, such as a disialo biantennary complex-type I(NeuAc-Gal-GlcNAc-Man)(2)-Man-GlcNAc(2)], an asialo complex-type [(Gal-GlcNAc-Man)(2)-Man-GlcNAc(2)], and a high-mannose type [MansGlcNAc(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-beta-N-acetylglucosaminidase (endo-beta-GlcNAc-ase) from Mucor hiemalis.