Photoinduced C-S Bond Cleavage of Thioglycosides and Glycosylation

A glycosyl coupling reaction via photoinduced direct activation of thioglycosides and subsequent O-glycosylation in the absence of photosensitizer was developed for the first time. This reaction underwent a selectively homolytic cleavage of a C-S bond to generate a glycosyl radical, which was oxidized to an oxacarbenium ion by Cu(OTf)(2), and a sequential O-glycosylation. A wide range of glycosides were synthesized in moderate to excellent yield using sugars, amino acids, or cholesterol as the acceptors.