Highly Diastereoselective Synthesis of C -Glycosides from Glycal Anomers.

This Letter presents a highly diastereoselective synthesis of C -hydroxymethine glycosides from glycal anomers using a chiral N -heterocyclic carbene-copper catalyst. The high diastereoselectivity was synergistically controlled by the stereocenter of the substrate and chirality of the N -heterocyclic carbene-copper complex without being interrupted by the stereochemistry of C5 and the anomeric position. This approach enables the production of a diverse array of C -hydroxymethine glycosides using synthetically versatile glycals and various functionalized aldehydes.