Synthesis and biological properties of benzo-annulated rutaecarpines.

A series of benzo-annulated rutaecarpines were prepared from anthranilic acid and 3-aminonaphthalene-2-carboxylic acid by Fischer indole synthesis as key reaction. Cytotoxicity was somewhat increased by the introduction of benzo-annulation, which was not directly related to the inhibitory activity against topoisomerases (topo) I and II. Benzo-annulation on ring A led to significant increase of inhibitory activity against topo II while annulations on ring E increased inhibitory activity against topo I.