Hydrogen Bond Synchronized Dual Activation Enables the Unified β-Selective O-Glycosylation Inside a Molecular Capsule

Carbohydrates are of central importance in biology. The selective chemical synthesis of carbohydrates, however, still poses a challenge; particularly, the selective formation of the

thermodynamically labile b-glycosidic bond is difficult and depends on the substrate’s substitution pattern. We here demonstrate that a molecular capsule catalyzes the highly

challenging selective formation of b-glycosides independent of the substrate’s substitution pattern and configuration. We demonstrate the versatility of the catalyst by synthesizing small to medium sized 1,2-cis, 2-deoxy, and 1,2-trans b-glycosides in very high selectivity and good yield. The confined space inside the molecular capsule naturally limits the scope concerning the size of reactants. Interestingly, the proposed mechanism involves the synchronized activation of the glycosyl donor and acceptor inside the supramolecular capsule via a relay involving seven hydrogen bonds. Such an activation is known for enzymes, however, to our knowledge, is unprecedented for man-made catalysts.