Photoinduced Diastereoselective and Stereodivergent Synthesis of C-Styryl Glycosides

A novel and efficient method for the stereoselective and stereodivergent synthesis of both unprotected and protected styryl C-glycosides through the reaction of sodium glycosyl sulfinate and hypervalent styryl iodine reagents is described. Using 2-bromo-9-fluorenone as a photocatalyst, C-styryl glycosides with an E configuration were selectively obtained. Furthermore, the introduction of a newly designed iridium-based catalyst enabled the selective formation of glycosides predominantly in the Z configuration. Mechanistic studies reveal the glycosyl radical is involved in the transformation.