Installation of 12b-substituents onto indolo[2,3-a]quinolizidin-2-ones and application to pentacyclic alkaloid synthesis

Abstract 12b-Substituted indolo[2,3- a ]quinolizidin-2-ones 5 are synthesized by treatment of Grignard reagents with O -acetyl iminium salt 4 generated by treating cyclic enaminoketone 3 with acetyl chloride. Subsequent Robinson annulation employing the Stork enamine protocol provided rac -3-phenyl-15,16-dehydroreserpone.