Total Synthesis of <i>e</i><i>nt</i>-Dihydrocorynantheol by Using a Proline-Catalyzed Asymmetric Addition Reaction

Abstract

[reaction: see text] 9-Tosyl-3,4-dihydro-beta-carboline reacted with 3-ethyl-3-buten-2-one in the presence of (S)-proline to give (3R,12bR)-3-ethyl-12-tosyl-3,4,6,7,8,9,10,11,12,12b-decahydro-1H-indolo[2,3-a]quinolizin-2-one in complete enantio- and diastereoselectivity. The compound thus obtained was readily transformed to ent-dihydrocorynantheol in three steps.