Stereoselective C-Glycosylation Reactions with Arylzinc Reagents

A general, transition-metal-free, highly stereoselective cross-coupling reaction between glycosyl bromides and various arylzinc reagents leading to β-arylated glycosides is reported. The stereoselectivity of the reaction is explained by invoking anchimeric assistance via a bicyclic intermediate. Stereochemical probes confirm the participation of the 2-pivaloyloxy group. Finally, this new method was applied to a short and efficient stereoselective synthesis of Dapagliflozin and Canagliflozin.