Divergent total synthesis of (−)-aspidophytine and its congeners via Fischer indole synthesis

A total synthesis of (−)-aspidophytine and the first total syntheses of its congeners, (+)-cimicidine and (+)-cimicine, were accomplished in a divergent manner. Construction of the aspidosperma skeleton was executed by Fischer indole synthesis between substituted phenylhydrazines and tricyclic aminoketone. The regiochemistry of the Fischer indole synthesis was strongly dependent on the choice of acid, and a weak acid, such as acetic acid provided the desired indolenine isomer in high selectivity.