Stereoselective Construction of Difficult Glycosidic Linkages

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AbstractIn this project funded by the Chemical Synthesis Program of the Chemistry Division, Professor Jianglong Zhu of the Department of Chemistry and Biochemistry at University of Toledo and Professor Xiaohua Li of the Department of Natural Sciences at University of Michigan-Dearborn are collaborating to develop novel approaches for stereoselective construction of difficult glycosidic linkages. This research has potential in the synthesis of carbohydrates by investigating new approaches to the stereoselective synthesis of structurally challenging and biologically valuable glycosidic linkages. By carrying out this project, the PIs will provide education and training opportunities for high school students, K-12 science teachers, undergraduate and graduate students, as well as visiting assistant professors. The PIs are recruiting women, groups underrepresented in the chemical sciences, and those from financially disadvantaged families to participate in this research. In addition, The PIs are participating in various outreach activities to promote teaching, training, and learning in chemical sciences. The research is targeting the construction of difficult glycosidic linkages such as beta-mannopyranosides and alpha-thioglycosides. Specifically, stereoselective synthesis of beta-mannopyranosides is targeted via anomeric O-alkylation under dual control of kinetic anomeric and chelation effects. This umpolung-type beta-mannosylation is being used to synthesize N-linked glycans. The stereoselective synthesis of S-linked-thioglycosides uses umpolung S-glycosylation through sulfenylation of the axial glycosyl lithium species. Collectively, these synthetic approaches have the potential to add a significant new dimension to the set of available methodologies to make glycosides.