Synthetic studies toward the marine alkaloid convolutindole A, a structurally remarkable derivative of the hallucinogen N,N-Dimethyltryptamine (DMT)

Abstract

Herein we report the results of a synthetic strategy toward the marine alkaloid convolutindole A, a structurally remarkable derivative of the hallucinogen N,N-dimethyltryptamine (DMT). While attempts to forge an advanced tryptamine intermediate using the Fischer reaction were unsuccessful, an iterative CH functionalisation strategy proved more fruitful. Subjecting 6-bromoindole to an iridium-catalysed triborylation gave a 2,4,7-triborylindole, which underwent selective protodeboronation at C2. The resulting 4,7-diborylindole underwent selective Chan-Evans-Lam and bromodeboronation reactions at C7 and C4 respectively, affording 4,6-dibromo-7-methoxyindole. Installation of the tryptamine side chain was achieved by reductive alkylation (presumably via a β-methoxytryptamine intermediate) to give an advanced tri-substituted tryptamine closely related to convolutindole A. This work showcases the utility of the iridium-catalysed CH borylation methodology to prepare densely functionalised indoles that would traditionally be accessed by heteroannulation, while providing an excellent foundation for ongoing synthetic efforts toward convolutindole A.