Chemical glycosylation methodologies for the preparation of the bioactive oligosaccharides and glycoconjugates promise reliable access to these compounds as homogeneous materials with welldefined structures in suffici...Chemical glycosylation methodologies for the preparation of the bioactive oligosaccharides and glycoconjugates promise reliable access to these compounds as homogeneous materials with welldefined structures in sufficient amounts.Here we report a novel activation method of thio(seleno)glycosides employing donor-acceptor cyclopropane(DAC)agents and Sc(OTf)_(3).The Lewis acid catalyst converts DAC into a formal 1,3-zwitterionic species that in turn activates thioglycosides to furnish a glycosyl 1,4-zwitterionic intermediate,interconverting with reactive glycosyl oxocarbenium in the solution with reversible leaving-group dissociation.This activation method effectively promotes glycosylation reactions between both armed and disarmed thioglycosides and structurally diverse acceptors,affording oligosaccharides with satisfactory yields.The usefulness of our activation method has been demonstrated by the mechanism-inspired 2,4-dinitrobenzenesulfonyl(DNs)group directed S_(N)2-like glycosylation and the facile preparation of both linear and branched trisaccharides in one pot via controlled sequential activation of thioglycoside donors.展开更多
基金the National Natural Science Foundation of China(grant no.22207092)the Natural Science Basic Research Plan of Shaanxi Province of China(grant no.2022JQ-091)+3 种基金the Fundamental Research Funds for the Central Universities(grant no.G2021KY05117)from Chinathe National Research Foundation(grant no.NRF-CRP22-2019-0002)the Ministry of Education(grant no.MOE-T2EP30120-0007)A*STAR(grant no.A20E5c0087)from Singapore for their financial support of this research.
文摘Chemical glycosylation methodologies for the preparation of the bioactive oligosaccharides and glycoconjugates promise reliable access to these compounds as homogeneous materials with welldefined structures in sufficient amounts.Here we report a novel activation method of thio(seleno)glycosides employing donor-acceptor cyclopropane(DAC)agents and Sc(OTf)_(3).The Lewis acid catalyst converts DAC into a formal 1,3-zwitterionic species that in turn activates thioglycosides to furnish a glycosyl 1,4-zwitterionic intermediate,interconverting with reactive glycosyl oxocarbenium in the solution with reversible leaving-group dissociation.This activation method effectively promotes glycosylation reactions between both armed and disarmed thioglycosides and structurally diverse acceptors,affording oligosaccharides with satisfactory yields.The usefulness of our activation method has been demonstrated by the mechanism-inspired 2,4-dinitrobenzenesulfonyl(DNs)group directed S_(N)2-like glycosylation and the facile preparation of both linear and branched trisaccharides in one pot via controlled sequential activation of thioglycoside donors.
