IsoCombretaQuinazolines: Potent Cytotoxic Agents with Antitubulin Activity

A series of novel isocombretaquinazolines (isoCoQ) 4 were quickly prepared by coupling N-toluenesulfonylhydrazones with 4-chloroquinazolines under palladium catalysis. These compounds, which can be regarded as isocombretastatin A-4 (isoCA-4) analogues that lack the 3,4,5-trimethoxyphenyl ring, displayed nanomolar-level cytotoxicity against various human cancer cell lines and were observed to effectively inhibit tubulin polymerization. The isoCoQ compounds 2-methoxy-5-(1-(2-methylquinazolin-4-yl)vinyl)phenol (4 b), 4-[1-(3-fluoro-4-methoxyphenyl)vinyl]-2-methylquinazoline (4 c), and 2-methoxy-5-(1-(2-methylquinazolin-4-yl)vinyl)aniline (4 d), which respectively bear the greatest resemblance to isoCA-4, isoFCA-4, and isoNH₂CA-4, are able to arrest HCT116 cancer cells in the G₂/M cell-cycle phase at very low concentrations. Preliminary in vitro antivascular assay results show that 4 d is able to disrupt a network of capillary-like structures formed by human umbilical vein endothelial cells on Matrigel. All these results clearly demonstrate that replacement of the 3,4,5-trimethoxyphenyl ring of isoCA-4 with a quinazoline nucleus is a feasible approach toward new and highly promising derivatives with the potential for further development as antitubulin agents.