Synthesis and in-vitro anticancer evaluation of bis-tacrine congeners

In the search for potential new anticancer drugs, an efficient synthesis of bis-tetrahydroaminoacridine (bis-tacrine) and its congeners was accomplished by bis-amination of 9-chlorotetrahydroacridine and its congeners under heated conditions. The critical chlorides were efficiently prepared from o-aminoaromatic acids and cycloketones in-situ in the presence of phosphorus oxychloride. In-vitro cytotoxic evaluation of the compounds was carried out against a panel of 60 human cancer cell lines. Among them, butyl-linked bis-tacrine (5b) exhibited the strongest cytotoxic profile with GI50 (concentration causing 50% growth inhibition) values of approximately 0.04-0.08 microM against breast, colon, melanoma and non-small lung cancer cells. Congeners bearing a longer alkyl chain were on average 30- to 100-fold less cytotoxic against these cancer cells. Shorter connecting alkyl chains of bis-tacrine or its congeners dramatically decreased the cytotoxic effects. Compound 5b has been selected for further biological evaluation of its anticancer profile.