Total Syntheses of Pleiocarpamine, Normavacurine, and C‑Mavacurine

The total syntheses of C-mavacurine-type indole alkaloids, (±)-pleiocarpamine, (±)-normavacurine, and (±)-C-mavacurine, were accomplished. The key step in the syntheses was the cyclization between the metal carbenoid at C 16 and the N 1 position in a Corynanthe-type compound that was equipped with a diazo function. For this cyclization, the N 4 modification of the substrate using an amine–borane complex was indispensable to fix the molecular conformation.