De-epimerization of Monosaccharides by Dynamic Kinetic Resolution: Ligand-Controlled Synthesis of O-Aryl-Glycosides through Copper-Catalyzed Cross-Coupling

We report a strategy for stereoselective O-aryl-glycoside synthesis by copper-catalyzed cross-coupling of a variety of anomeric sugars and (hetero)aromatic iodides. Stereocontrol of the alpha/beta selectivity can be successfully realized by slight structural modifications of the oxalic diamide ligands. Mechanistic studies indicated a dynamic kinetic resolution (DKR) reaction mechanism controlled by the ligand structures. This reaction could be performed on gram scale, and has also been applied to the synthesis of some natural products.