Synthesis and Cytotoxicity of 1,2-Disubstituted Naphth[2,3-<i>d</i>]imidazole-4,9-diones and Related Compounds

As part of our continuing search for potential anticancer drug candidates that are selective against slowly growing solid tumors, we have synthesized several series of 1- and 2-substituted derivatives of the lead structure, 1-ethyl-2-methylnaphth[2,3-d]imidazole-4,9-dione (5). Their cytotoxic activity in the National Cancer Institute's in vitro cancer cell line panel is reported. In general, substitution of various alkyl, phenyl, or benzyl moieties did not improve activity, and compound 5 remains the most active naphth[2,3-d]imidazole-4,9-dione derivative. However, high levels of activity and selectivity were found with several related 2-(acylamino)-3-chloro-1,4-naphthoquinones (2f−j). Compound 2i, 2-[(2-fluorophenyl)acetamido]-3-chloro-1,4-naphthoquinone, has been selected for further in vivo testing and as an additional lead compound for further structural modification