Decoration of proteins with sugar chains: recent advances in glycoprotein synthesis

• Glycoproteins can be obtained by chemical/chemoenzymatic synthesis as single glycoforms.
• Chemical synthesis can provide unnatural form as well as natural form of glycoproteins.
• Glycoprotein X-ray crystallography is now feasible structural analysis by using chemically synthesized quasi-racemic glycoprotein.

Chemical or chemoenzymatic synthesis is an emerging approach to produce homogeneous glycoproteins, which are hard to obtain by conventional biotechnology methods. Recent advances in the synthetic methodologies for the decoration of protein molecules with oligosaccharides provide several remarkable syntheses of homogeneous glycoproteins. This short review highlights several of the latest syntheses of glycoproteins including therapeutically important glycoproteins, a highly glycosylated protein, and unnatural glycoproteins in order to illustrate the power of the modern glycoprotein synthesis. Structurally defined glycoproteins are a novel material for understanding the molecular basis of glycoprotein functions and for the development of the next generation of biopharmaceuticals.