Diastereo- and enantioselective alkaloid syntheses

Abstract

Enantiomerically pure cyclic nitrones, readily available via electrophilic hydroxyaminations of N-acylsultams, serve as key intermediates in the syntheses of optically pure (−)-allosedamine, (−)-pinidine, (−)-coniine, (−)-solenopsin-A, (−)-2-heptylpyrrolidine, (−)-solenopsis fugax venom and (−)-xenovenine. This work also features a new deoxygenative decarboxylation of N-hydroxylamines carrying an acyl substituent at C(α). N-4-Alkenylhydroxylamine cyclizations proceed in a suprafacial manner, consistent with a retro-Cope elimination pathway. This reaction is strategically employed in short and efficient syntheses of (±)-α-lycorane and the enantiomerically pure alkaloid (+)-trianthine. © 1994 IUPAC