C-Glycosides are metabolically stable mimics of natural O-glycosides and are expected to be useful tools for investigation of the biological functions of glycans. Here, we describe the synthesis of a series of aryl and vinyl C-glycosides by stereoinvertive sp3–sp2 cross-coupling reactions of 2-deoxyglycosyl boronic acid derivatives with aryl or vinyl halide, mediated by a photoredox/nickel dual catalytic system. Hydrogenation of the vinyl C-glycosides afforded C-linked 2′-deoxydisaccharide analogues.

Seven mono- and dihydroxycholesterols were prepared by direct C–H oxidation of the cholestane skeleton with a recently developed Ru(Bpga) catalyst (Ru(Bpga) = [RuCl (bpga) (PPh3)] Cl; bpga = 2-(bis(pyridin-2-ylmethyl)amino)-N-(2,6-dimethylphenyl)acetamide)). Due to the high selectivity of the Ru(Bpga) complex for tertiary C–H, the reaction afforded a mixture of 25-, 20-, 17-, and 14-oxygenated cholesterols that could be easily separated by high-performance liquid chromatography. These results suggest that late-stage C–H oxidation could be a viable strategy for preparing candidate metabolites of biologically important molecules.

C-Glycoside analogues of native glycans are useful molecular tools for medicinal chemistry and chemical biology due to their resistance to cellular glycoside hydrolases. Previously we reported an α-selective direct C-glycosylation of 2-deoxy-β-glycosyl boronate via Ni/photoredox-catalyzed stereoinvertive cross-coupling reaction. Here we report a complementary stereoretentive synthetic methodology for preparation of β-C-glycosides from a similar boronate precursor via addition of Csp2 anion followed by 1,2-migration of the glycosyl donor.

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