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

Abstract

AbstractChiral tetrahydro‐β‐carboline (THβC) is not only a prevailing structural feature of many natural alkaloids but also a versatile synthetic precursor for a vast array of monoterpenoid indole alkaloids. Asymmetric synthesis of C1‐alkynyl THβCs remains rarely explored and challenging. Herein, we describe the development of two complementary approaches for the catalytic asymmetric alkynylation of 3,4‐dihydro‐β‐carbolinium ions with up to 96 % yield and 99 % ee. The utility of chiral C1‐alkynyl THβCs was demonstrated by the collective total syntheses of seven indole alkaloids: harmicine, eburnamonine, desethyleburnamonine, larutensine, geissoschizol, geissochizine, and akuammicine.