The stereochemistry of anomeric carbon-oxygen bonds, which is the typical framework of carbohydrate molecules, can have implications for structure and biological function. Consequently, the development of methods that control stereoselective construction of anomeric C(sp3)-O bonds are of paramount importance, but challenging. In general, stereochemical outcomes in anomeric C(sp3)-O bond-forming processes are unpredictable and dependent on the steric and electronic nature of the protecting groups bound on carbohydrate coupling partners. In this symposium, we describe a strategy for stereocontrolled construction of the C(sp3)-O glycosidic bond, in which the anomeric sp3-hybridized carbon of an a-1-bromo glycoside is coupled with an alkyl alcohol, through the action of a visible light-activated copper catalyst. This cross-coupling protocol enables highly diastereoselective access to a-1,2-cis and a-2-deoxy-2-fluoro glycosides as well as bioactive a-glycan oligosaccharides. In contrast to nearly all catalytic glycosylation reactions which typically proceeds via SN1 or SN2 pathway, this method is the first example of using copper catalyst induced by visible light to effect diastereoselective sp3 C-O glycosidic bond formation.

Stereoselective glycosides via copper-catalyzed cross couplings of anomeric sp3 carbons with alkyl alcohols induced by visible light

2019 Fall National Meeting

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