All glycosylation reactions between nucleophilic alcoholic acceptors and electrophilic glycopyranosyl donors must involve proton transfer. Until recently proton transfer was considered to have little or no affect on either reactivity or stereoselectivity even though most proton transfers start from a hydrogen bonding interaction. Recent theoretical and experimental studies support a model that in some cases hydrogen bonding between the nucleophile and the donor can influence the stereochemical outcome of the reaction. Further, polar interactions of the hydroxylic oxygen with the promoter, and/or hydrogen bonding to the leaving group and/or polar additives like solvent have been proposed to improve reactivity and influence stereoselectivity. These factors will be reviewed in the context of developing suitable glycosylation conditions for donors derived from the nonulosonic acid, legionaminic acid.

Proton transfer and hydrogen bonding in glycosylation reactions

251st National Meeting (2016)

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