2-Alkoxycarbonyl-3-arylamino-5-substituted thiophenes as a novel class of antimicrotubule agents: Design synthesis cell growth and tubulin polymerization inhibition

摘要

Microtubules are recognized as crucial components of the mitotic spindle during cell division, and, for this reason, the microtubule system is an attractive target for the development of anticancer agents. Continuing our search strategy for novel tubulin targeting-compounds, a new series of 2-alkoxycarbonyl-3-(3′,4′,5′-trimethoxyanilino)-5-aryl/heteroarylthiophene derivatives was designed, synthesized and demonstrated to act as tubulin polymerization inhibitors at the colchicine site. A structure-activity relationship study on the phenyl at the 5-position of the thiophene ring was performed by introducing a variety of substituents containing electron-releasing and electron-withdrawing groups, with the 2-alkoxycarbonyl-3-(3′,4′,5′-trimethoxyanilino)thiophene scaffold being the minimum structural requirement for activity. Of the tested compounds, derivatives >4a, >4c, >4i and >4k possessed the highest overall potency and displayed high antiproliferative activities at submicromolar concentrations, with IC50 values ranging from 0.13 to 0.84 μM against four different cancer cell lines. Three agents (>4a, >4c and >4i) in the present series had similar effects, and these were comparable to those of the reference compound combretastatin A-4 (CA-4) as inhibitors of tubulin assembly. The antitubulin effects correlated with the cytostatic activities and indicate that these compounds inhibit cell growth through inhibition of tubulin polymerization by binding at the colchicine site. Compound >4c, containing the 2′-thienyl ring at the 5-position of the 2-methoxycarbonyl-3-(3′,4′,5′-trimethoxyanilino)thiophene scaffold, exhibited substantial antiproliferative activity with a mean IC50 value of 140 nM, inhibited tubulin polymerization with an IC50 value of 1.2 μM, similar to that of CA-4 (IC50: 1.1 μM), and induced apoptosis in HeLa cells.