Total synthesis of kopsine, fruticosine, and structurally related polycyclic caged Kopsia indole alkaloids

Abstract

Kopsine, fruticosine and related caged and polycyclic Kopsia indole alkaloids have been attractive synthetic targets since 1983. Besides their promising bioactivities, the multiple continuous stereogenetic centers including two all-carbon quaternary stereocenters embedded in a rigid and caged polycyclic skeleton poses significant challenges in synthetic chemistry. Due to the extrodinary complex structures, tremendous efforts have been devoted to these synthetic targets. In this review, we discuss reported strategies for the total synthesis of kopsine, fruticosine and related Kopsia indole alkaloids with an emphasis on tactics to construct the polycyclic skeleton and methodologies to install the C7/C20 stereocenters.