Insight into gold-catalyzed glycosylation of glycosyl ynenoates

Gold-catalyzed glycosylation using alkyne donors is a versatile approach for the efficient assembly of diverse types of glycosides due to its catalytic and mild glycosylation properties. Minor structural alterations might significantly affect the glycosylation reaction when the alkyne-based leaving groups are simplified. By mapping the glycosylation reactivities of a series of structurally simplified alkyne donors, herein we demonstrate the role of each characteristic functional group of glycosyl ynenoates. Based on the isolation and the X-ray diffraction characterization of the pyran-5-ylgold(I) complex generated from the leaving group, a plausible mechanism of the gold(I)-catalyzed glycosylation with glycosyl ynenoates as donors was proposed.