Divergent Total Synthesis of (±)‐Mahanine and Other Carbazole Alkaloids

Abstract

AbstractWe represent here, a divergent approach for the total synthesis of (±)‐Mahanine and twelve other naturally occurring carbazole alkaloids. Remarkably, we have utilized a simplified scalable Suzuki coupling for C−C bond formation and a metal‐free C−N coupling sequence to synthesize the functionalized carbazole scaffold from a single intermediate. Subsequently, either functional group manipulations or late‐stage pyran ring annulation furnished a library of 13 carbazole alkaloids mostly isolated from a traditional medicinal plant Murraya koenigii. The construction of carbazole moiety at the initial‐stage followed by late‐stage pyran annulation under mild condition overcomes the decomposition problem of pyran‐ring under acidic or other harsh reaction conditions.