On the synthesis and biological properties of isocombretastatins: a case of ketone homologation during Wittig reaction attempts
New isocombretastatins were synthesized by reacting the corresponding phenstatin analogs with CH3PPh3Br in presence of tBuOK. These new derivatives showed significant activities against cellular proliferation and tubulin polymerization. In particular, monomethoxylated derivatives of phenstatin and isoCA-4 exhibit similar activities to those of parent phenstatin. Attempts of the Wittig reaction on 2- (or 4-) methoxy-4′-nitrobenzophenones in the same conditions do not lead to the expected isocombretastatins but to methyleneketones with the exclusion of triphenylphosphine. A mechanism for this new ketone homologation was proposed.