Comprehensive construction of biologically active α‐carbolines from synthetic and natural origin

Abstract

α‐Carboline is an important scaffold present in various synthetic and naturally obtained bioactive compounds possessing a wide range of pharmacological properties. Hence, in the current comprehensive review, we intend to present the main routes to the synthesis of α‐carboline analogs based on various pathways such as pyrrole, benzene, and pyridine ring annulation. The pathways include either or combinations of transition metal‐catalyzed amination/arylation, Graebe‐Ullmann reaction (thermal pyrolysis, photochemical cyclization), Diels‐Alder cycloaddition and condensation reactions, N‐Heterocyclic carbene catalysed reactions, decarboxylative annulation, etc. of substituted benzene, pyridine, quinoline, and indole derivatives in order to compare the potential of synthetic routes of this series and consolidate the development, current status and perspectives for the design of α‐carboline analogs. Various pharmacological and spectroscopy functions of the compounds belonging to this class are summarized herewith. It also discusses the synthesis of functionalized bioactive naturally obtained hetero‐annulated α‐ carbolines.