Synthesis and biological properties of C12,13-cyclopropylepothilone a and related epothilones

Background: The epothilones are natural substances that are potently cytotoxic, having an almost identical mode of action to Taxol(TM) as tubulin-polymerization and microtubule-stabilizing agents. The development of detailed structure-activity relationships for these compounds and the further elucidation of their mechanism of action is of high priority. Results: The chemical synthesis of the C12,13-cyclopropyl analog of epothilone A and its C12,13-trans-diastereoisomer has been accomplished. These compounds and several other epothilone analogs have been screened for their ability to induce tubulin polymerization and death of a number of tumor cells. Several interesting structure-activity trends within this family of compounds were identified. Conclusions: The results of the biological tests conducted in this study have demonstrated that, although a number of positions on the epothilone skeleton are amenable to modification without significant loss of biological activity, the replacement of the epoxide moiety of epothilone A with a cyclopropyl group leads to total loss of activity.