CHAPTER 6: Chemoenzymatic Synthesis of N-Glycans

A major post-translational modification of proteins on cell surfaces is asparagine N-linked glycosylation, which plays critical roles in various biological processes. Over the past decade, efficient strategies for the synthesis of N-glycans have become increasingly attractive because it is highly desired to obtain structurally defined N-glycans in sufficient amounts for structure–function studies. In this respect, chemical synthesis of N-glycans has been well developed and has become the most frequently used approach to generate well-defined N-glycans. However, when synthetic targets are complicated N-glycans and especially N-glycan libraries, the chemical approach still remains challenging, tedious, and time-consuming. More recently, a facile and practical strategy, core synthesis/enzymatic extension (CSEE), has been developed for efficient synthesis of N-glycan libraries with structural diversities, wherein an N-glycan core is first chemically synthesized and further elongated by glycosyltransferases (GTs) to rapidly produce a large number of complex N-glycans. Herein, we provide a concise summary of most recent advances in chemical and chemoenzymatic synthesis of N-glycans.