Stereospecific total synthesis of (−)-8- epi-hyperaspine

Abstract

Condensation of protected δ-hydroxy-β-amino ester 7 with a β-keto ester provides vinylogous urethane 8 , which is cyclized under the action of t-BuOK followed by decarboxylation to afford enone 12 . Hydrogenation of 12 or its N, O-diprotected derivative 13 gives 2,6- cis-disubstituted piperdines. Using these intermediates, (−)-8- epi-hyperaspine is synthesized.