Total Synthesis of (-)-Herbindoles A, B, and C via Transition-Metal-Catalyzed Intramolecular [2+2+2] Cyclization between Ynamide and Diynes

The total syntheses of (-)-herbindoles A, B, and C as naturally occurring forms were accomplished for the first time through transition-metal-catalyzed intramolecular [2 + 2 + 2] cyclization between ynamide and diynes. This strategy provided a highly efficient synthetic route to all three herbindoles from an identical indoline derivative as a common intermediate.