Direct and highly stereoselective synthesis of quinolizidine iminosugars promoted by l-proline-Et3N

Mannich Reactions of Carbohydrate Derivatives with Ketones To Afford Polyoxy-Functionalized Piperidines

Mannich reactions of carbohydrate derivatives with ketones that afford polyoxy-functionalized piperidines are reported. Ketone nucleophiles (enamines/enolates) were generated in the presence of the amines used for the formation of the iminium ions of sugar derivatives with or without an additive. Conditions to preferentially generate piperidine derivatives rather than tetrahydrofurans were identified. Products from the reactions of allyl ketones were readily transformed to bicyclic piperidines.