B-ring-modified isocombretastatin A-4 analogues endowed with interesting anticancer activities

A novel class of isocombretastatin A-4 (isoCA-4) analogues with modifications at the 3'-position of the B-ring by replacement with C-linked substituents was studied. Exploration of the structure-activity relationships of theses analogues led to the identification of several compounds that exhibit excellent antiproliferative activities in the nanomolar concentration range against H1299, MDA-MB231, HCT116, and K562 cancer cell lines; they also inhibit tubulin polymerization with potency similar to that of isoCA-4. 1,1-Diarylethylenes 8 and 17, respectively with (E)-propen-3-ol and propyn-3-ol substituents at the 3'-position of the B-ring, proved to be the most active in this series. Both compounds led to the arrest of various cancer cell lines at the G(2) /M phase of the cell cycle and strongly induced apoptosis. Docking of compounds 8 and 17 in the colchicine binding site indicated that their C3' substituents guide the positioning of the B-ring in a manner different from that observed for isoCA-4.