Synthesis and anticancer activity of fluorinated analogues of combretastatin A-4

The synthesis of a series of fluorinated benzaldehydes and their use in the Wittig synthesis of fluoro-substituted stilbenes is described. 3,5-Difluoro-4-hydroxybenzaldehyde (6) and 3-fluoro-4-methoxybenzaldehyde (11) are prepared by Duff formylation of 3,5-difluorophenol and 2-fluoroanisole, respectively. 2-Methoxy-3,4-difluorobenzaldehyde was obtained by Friedel–Crafts formylation of 2,3-difluoroanisole with α,α-dichloromethyl methyl ether. The aldehydes were used to make a series of fluorinated analogues of the anticancer combretastatins A-1, A-2 and A-4. The in vitro anticancer properties of the fluoro combretastatins are reported. The most active fluoro analogue 3-deoxy-3-fluoro-combretastatin A-4 (Z-2) retains the potent cell growth inhibitory properties of CA-4.