Catalytic Asymmetric Alkynylation of 3,4‐Dihydro‐β‐carbolinium Ions Enables Collective Total Syntheses of Indole Alkaloids

Abstract

Chiral tetrahydro-b-carboline (THbC) is not only ap revailing structural feature of many natural alkaloids but also av ersatile synthetic precursor for av ast arrayo f monoterpenoid indole alkaloids.Asymmetric synthesis of C1alkynyl THbCs remains rarely explored and challenging. Herein, we describe the development of two complementary approaches for the catalytic asymmetric alkynylation of 3,4dihydro-b-carbolinium ions with up to 96 %yield and 99 %ee. The utility of chiral C1-alkynyl THbCs was demonstrated by the collective total syntheses of seven indole alkaloids: harmicine,eburnamonine,desethyleburnamonine,larutensine, geissoschizol, geissochizine,and akuammicine.