Chemoenzymatic Synthesis of Asymmetric N-Glycans in Aqueous Solution via Sulfate and Phosphate Orthogonal Protection

Glycoproteins often exist in nature as heterogeneous glycoforms, making it difficult to obtain pure homogeneous samples for studying the roles of specific N-glycans within a glycoprotein. Despite various chemical and enzymatic methods developed for the synthesis of N-glycans, access to highly diverse N-glycans remains a challenge. Herein, we report a concise strategy for the synthesis of multiantennary N-glycans from designed common core structures with phosphate and sulfate protecting groups, which can be selectively deprotected by respective phosphatase and sulfatase, thereby enabling enzymatic elongation to install a desired glycan chain at a specific antenna. We also explored the directing effect of galactose sulfation for enzymatic fucosylation of the neighboring GlcNAc, further expanding the structural diversity of multiantennary N-glycans. Starting from sulfate and phosphate-terminated core structures, this synthetic strategy in aqueous solution provides an efficient and practical route for the enzymatic assembly of a diverse array of complex N-glycans for biological study.