Highly Stereoselective Synthesis of β-Glycosyl Esters via N-Heterocyclic Carbene Catalysis under Aerobic Conditions.

We disclose an efficient N-heterocyclic carbene (NHC)-catalyzed glycosylation method employing glycosyl bromides as donors and aldehydes as acceptors, which enables facile access to structurally diverse β-glycosyl esters with high yields and excellent stereocontrol. This transformation proceeds under mild, metal-free, and open-air conditions and exhibits broad substrate scope with respect to both reaction partners (54 examples). Notably, the reaction displays broad functional-group compatibility and tolerates nucleophilic hydroxyl groups. Its synthetic utility is illustrated by the late-stage modification of bioactive molecules and a series of synthetic transformations. Overall, our method provides an efficient alternative for the synthesis of valuable β-glycosyl esters.