Trifluoromethyl-promoted homocamptothecins: synthesis and biological activity

The homocamptothecin (hCPT) represents a new class of topoisomerase inhibitor which combines enhanced plasma stability and strong antitumor activity. Fluorine imparts desirable characteristics to drugs by modulating both the pharmacokinetics and pharmacodynamic properties of a drug. Therefore, in an attempt to improve the antitumor activity of homocamptothecins, seven new 7-trifluoromethylated homocamptothecin derivatives were prepared by proline-catalyzed Friedlander annulation. The antitumor activity in vitro and in vivo on cancer cell lines, and inhibitory properties of topoisomerase I-mediated DNA cleavage of compounds 6c and 8b were evaluated. Several of these trifluoromethylated hCPT derivatives (such as 6a, 6b and 6c) possessed higher in vitro antitumor activity than topotecan (TPT). Especially, the compound 6c showed effective in vivo antitumor activity comparable to that of TPT.