Transition-Metal-Free beta-Selective C-Glycosylation of beta-Glycosyl Boronates via Stereoretentive 1,2-Migration

C-Glycoside analogues of native glycans are useful molecular tools for medicinal chemistry and chemical biology due to their resistance to cellular glycoside hydrolases. We previously reported an ?-se-lective direct C-glycosylation of 2-deoxy-13-glycosyl boronate through a Ni/photoredox-catalyzed stereoinvertive cross-coupling reaction. Here we report a complementary stereoretentive synthetic method for the preparation of 13-C-glycosides from a similar boronate precursor through the addition of a C(sp2) anion followed by 1,2-migration of the glycosyl donor.