Carboline Regioisomers Based on Unified Synthetic Approaches.

Carbolines are a prominent class of tricyclic alkaloids omnipresent in natural products and bioactive compounds. Four different carboline regioisomers are known (α‐, β‐, γ‐, and δ‐carbolines), which can be classified according to the nitrogen atom position inside the pyridine ring. As an emerging structural motif in drug discovery, a multitude of synthetic methods have been established for the construction of carboline frameworks, which in general requires customized approaches for the assembly of each regioisomer. Distinguishingly, their frameworks are also accessible from unified approaches, which are capable of generating multiple regioisomers, thus suitable for introducing diversity in isomeric carbolines. In this review, the construction of isomeric carbolines based on unified synthetic approaches is summarized. [ABSTRACT FROM AUTHOR]