Cytotoxicity of Mannich bases of alpha-arylidene-beta-ketoesters and related compounds against EMT6 mammary carcinoma cells.

A number of Mannich bases 2 derived from alpha-arylidene-beta-ketoesters, some corresponding deaminated products 3, and a thiol adduct 5 were prepared. High resolution 1H NMR spectroscopy revealed that, in solution, most of the bases 2 existed principally in acyclic forms, but that all members of this series underwent some intramolecular cyclization. The compounds 2, 3 and 5 possessed activity against EMT6 mammary carcinoma cells. The Mannich bases 2a-e had the highest cytotoxicity. Topliss analysis of these compounds revealed an E4 parameter dependency, in which intramolecular cyclization was minimal. The Mannich base 2f--which existed principally in the cyclic forms 6 in deuterium oxide, the deamination products, and a thiol adduct had approximately one-sixth of the activity of 2a-e.