Efficient synthesis of polypeptide-α-thioester by the method combining polypeptide expression and chemical activation for the semi-synthesis of interferon-γ having oligosaccharides.

In order to synthesize interferon-γ glycoform having an oligosaccharide at the 97 position by a semi-synthetic method, interferon-γ-polypeptide-(1-94)-α-hydrazide was prepared by the specific Cys-cyanylation of polypeptide-(1-94)-Cys-His6 expressed from E. coli and subsequent hydrazinolysis in 22% yield (two steps). This polypeptide-α-hydrazide was then converted into corresponding polypeptide-α-thioester under NaNO2 /acid conditions followed by thiolysis in 83% yield.