Development and Investigation of a Dehydrative Glycosylation With Activated Diphenyl Sulfonium Reagents

Mechanistic studies suggest that the glycosyl donor is initially activated via nucleophilic attack of the hemiacetal hydroxyl upon the sulfonium center of diphenylsulfide bis(trifluoromethanesulfonate), leading to formation of a glycosyl oxosulfonium. Low temperature NMR studies have revealed that a glycosyl pyridiniurn is subsequently formed in the latter stages of the glycosylation. Additional data suggests, however, that the reactive intermediate is likely a glycosyl oxocarbenium.