Ugi Four-Component Reaction with Tandem Deprotection, Cyclization and Pictet–Spengler Reaction: A Concise Route to N-Fused Polycyclic Indoledi­ketopiperazine Alkaloid Analogues

Abstract

Aza-fused polycyclic indolediketopiperazine alkaloids are of potential interest due to their broad range of biological activities. Traditionally, a number of methods have been reported to generate N-fused polycyclic indolediketopiperazine skeletons, but the development of novel, concise methods to modify its substitution pattern are strongly required. Herein, we have described the two-step formation of N-fused polycyclic indolediketopiperazine alkaloid analogues by the application of the Ugi 4-CR with tandem deprotection-cyclization/Pictet-Spengler reaction