Reactions of harmaline (4,9-dihydro-7-methoxy-1-methyl-3H-pyrido[3,4-b]indole) and its derivatives. Part II. Reinvestigation of acetylharmaline

Abstract

A reinvestigation of the acidic hydrolysis of acetylharmaline (2-acetyl-2,3,4,9-tetrahydro-7-methoxy-1-methylene-1H-pyrido[3,4-b]indole)(I) has shown that the product is not that of simple hydration of the exocyclic double bond, but is the result of cleavage of ring C, i.e. 3-(2-acetamidoethyl)-2-acetyl-6-methoxyindole (V). Further acetylation of this results in the 3-(2-diacetylaminoethyl) derivative (VI); no acetylation of the indole nitrogen atom is observed, contrary to a previous report. 1,2,3,5,6,11-Hexahydro-3-oxoindolizino[8,7-b]indol-4-ium tetrafluoroborate (XIV) was synthesised by a novel cyclisation–elimination reaction involving the treatment of N-succinimidotryptamine with triethyloxonium tetrafluoborate.