Glycosylation of a Ketone with an O-Glycosyl Trichloroacetimidate Provides an Enol Glycoside.

An enol-type glycosylation reaction has been investigated. Enol glycosides can be obtained from the reaction between O-glycosyl trichloroacetimidates and the corresponding ketones promoted by an acid. The enol glycosides derived from cyclic ketones can be afforded efficiently and isolated in good yield, while those from acyclic ketones are prepared in low conversion or are too labile for isolation. Further studies on different glycosyl donor types indicate that only the O-glycosyl trichloroacetimidate works well as a donor for enol glycosylation.