Chemoenzymatic Assembly of Mammalian O-Mannose Glycans.

O-Mannose glycans account up to 30 % of total O-glycans in the brain. Previous synthesis and functional studies have only focused on the core M3 O-mannose glycans of α-dystroglycan, which are a causative factor for various muscular diseases. In this study, a highly efficient chemoenzymatic strategy was developed that enabled the first collective synthesis of 63 core M1 and core M2 O-mannose glycans. This chemoenzymatic strategy features the gram-scale chemical synthesis of five judiciously designed core structures, and the diversity-oriented modification of the core structures with three enzyme modules to provide 58 complex O-mannose glycans in a linear sequence that does not exceed four steps. The binding profiles of synthetic O-mannose glycans with a panel of lectins, antibodies, and brain proteins were also explored by using a printed O-mannose glycan array.