Reactions and synthetic applications of β-oxo-sulphoxides. Part VI. A new synthesis of the pyrido[4,3-b]carbazoles olivacine and ellipticine

Abstract

The acid-catalysed cyclization of β-oxo-sulphoxides was applied to a synthesis of olivacine and ellipticine. An oxo-sulphoxide derived from methyl N-benzylindole-3-propionate was cyclized with trifluoroacetic acid to give a 2-oxo-1,2,3,4-tetrahydrocarbazole derivative, and a side chain was introduced at the carbonyl group. Aromatization and construction of the pyridine ring proceeded efficiently to yield olivacine. In the same way, ellipticine was synthesized from methyl N-benzylindole-3-butyrate.