Total syntheses of mersicarpine

Abstract

This review focuses on synthetic studies on mersicarpine that has a characteristic skeleton including seven-membered cyclic imine fused with indoline and δ-lactam. After a brief discussion of structural features and proposed biogenesis of this compound, several synthetic efforts toward construction of mersicarpine core are described. Total syntheses of mersicarpine are described including Kerr's racemic synthesis utilizing a formation of seven-membered cyclic imine from α-hydroxyketone prepared by oxidation of indole, racemic syntheses of the Kerr's synthetic intermediate by Zard and Han, the first enantiocontrolled total synthesis by Fukuyama based on the construction of seven-membered α-hydroxyimine by autoxidation of azepinoindole, and the second enantiocontrolled synthesis by Tokuyama employing a DIBALH-mediated ring-expansion reaction of cyclic ketoxime fused with indole.