Zinc tetrafluoroborate Catalyzed Stereo‐ and Regioselective O‐Glycosylation for the Direct Synthesis of β‐Glycosides from Armed O‑Glycosyl Trichloroacetimidates

Abstract Efficient stereo‐ and regioselective O ‐glycosylation methods remain essential to capacitate the studies of sugars and sugar derivatives in various disciplines. In this work, we demonstrated an operationally simple and cost‐effective strategy for the synthesis of 1,2‐ trans glycosides by the activation of armed O ‐glycosyl trichloroacetimidates donor using zinc tetrafluoroborate. This mild, transition metal‐free, and scalable approach allowed stereo‐ and regioselective synthesis of β ‐glycosides with a wide range of acceptors containing various protecting groups/functionalities. This method is exemplified by synthesizing a branched trisaccharide fragment related to the cell wall O ‐polysaccharide of E. Coli O27.