Stereoretentive Conversion to C-Glycosides from S-Glycosides via Ligand-Coupling on Sulfur(IV)

A novel strategy is reported for the stereoselective synthesis of C(sp2)-C(sp3) C-glycosides, which converts heteroaryl S-glycosides into heteroaryl C-glycosides with retention of configuration through a sequential process involving oxidation and Grignard reagent attack. The new method involves the generation of a S(IV) intermediate, followed by ligand coupling of the glycosyl and heteroaryl groups to yield heteroaryl C-glycosides. The diverse heteroaryl C-glycosides were achieved with good efficiency.