A “Traceless” Directing Group Enables Catalytic S<sub><i>N</i></sub>2 Glycosylation toward 1,2-<i>cis</i>-Glycopyranosides
Xu Ma, Zhitong Zheng, Yue Fu, Xijun Zhu, Peng Liu, Liming Zhang
Abstract
Generally applicable and stereoselective formation of 1,2-cis-glycopyranosidic linkage remains a long sought after yet unmet goal in carbohydrate chemistry. This work advances a strategy to this challenge via stereoinversion at the anomeric position of 1,2-trans glycosyl ester donors. This SN2 glycosylation is enabled under gold catalysis by an oxazole-based directing group optimally tethered to a leaving group and achieved under mild catalytic conditions, in mostly excellent yields, and with good to outstanding selectivities. The strategy is also applied to the synthesis of oligosaccharides.
Topics & Concepts
ChemistryGlycosylationGlycosylAnomerSN2 reactionStereoselectivityCatalysisCarbohydrate chemistryStereochemistryOxazoleLeaving groupCombinatorial chemistryGroup (periodic table)Organic chemistryBiochemistryCarbohydrate Chemistry and SynthesisGlycosylation and Glycoproteins ResearchLegume Nitrogen Fixing Symbiosis