(E)-2-Benzylidenebenzocyclanones: part XIII-(E)/(Z)-Isomerization of some cyclic chalcone analogues. Effect of ring size on lipophilicity of geometric isomers

Optimized isocratic reverse phase high-performance liquid chromatography (RP-HPLC) method was developed for separation of the respective (E) and (Z) isomers of the cyclic chalcone analogues (E)-2-(4'-X-benzylidene)-1-indanones, -tetralones, and -benzosuberones. The method has been applied to monitor progress of the light-induced (E)/(Z) isomerization process in the three series. Data indicate formation of equilibrium mixtures of the respective geometric isomers. Comparison of the HPLC retention factors of the respective geometric isomers showed the (Z) isomers less lipophilic in the benzosuberone and the tetralone but more lipophilic in the indanone series. Data provide experimental evidence of opposite effect of ring size and geometric isomerism on lipophilicity of conformationally restricted (cyclic) analogues of chalcone, an open chain pharmacophore.