Insights into the Activation of Alkyne-Installed Glycosyl Donors with Dual Acidic Metal Catalysts: Reaction Pathway, Influencing Factors, and Enlightenment for Glycosylation

The activation of alkyne-installed glycosyl donors with dual acidic metal catalysts were studied. Lewis and/or π acidity-activated pathways were observed for alkynyl carbonate-, ester-, and ether-type donors, and π acidity-promoted reaction mode afforded higher efficiency and yields. The activation mode for a certain metal catalyst is determined by the nature of catalysts itself, protecting groups on sugar rings, type of sugars, and structure of aglycones. The discovery gives us valuable insights into the glycosylation of alkyne-containing donors.