Stereoselective synthesis of chiral piperidine derivatives employing arabinopyranosylamine as the carbohydrate auxiliary

Abstract

Stereoselective synthesis of 2-substituted dehydropiperidinones and their further transformation to variously disubstituted piperidine derivatives was achieved employing D-arabinopyranosylamine as the stereodifferentiating carbohydrate auxiliary. A domino Mannich–Michael reaction of 1-methoxy-3-(trimethylsiloxy)butadiene (Danishefsky's diene) with O-pivaloylated arbinosylaldimines furnished N-arabinosyl dehydropiperidinones in high diastereoselectivity. Subsequent conjugate cuprate addition gave 2,6-cis-substituted piperidinones, while enolate alkylation furnished 2,3-trans-substituted dehydropiperidinones. Electrophilic substitution at the enamine structure afforded 5-nitro- and 5-halogen dehydropiperidinones of which the latter were applied in palladium-catalyzed coupling reactions. The absolute configuration of the obtained products was proven by NMR and X-ray structure analysis as well as by syntheses of the alkaloids (+)-coniine and (+)-dihydropinidine.Key words: piperidine alkaloids, carbohydrate auxiliary, domino Mannich–Michael reaction, conjugate cuprate and hydride addition, electrophilic substitution of enamines.