Analysis of Two Cycloplatinated Compounds Derived from N-(4-Methoxyphenyl)-α-benzoylbenzylidenamine. Comparison of the Activity of These Compounds with Other Isostructural Cyclopalladated Compounds

In the present paper we report the synthesis, structural characterization, biochemical properties, and antiproliferative activity of two organo-cis-platinum cyclometalated compounds of formula [M(4-OMeC₆H₄N═C(COC₆H₅)C₆H₄)X]₂, where M = Pt and X = Cl (4) or OAc (5). The IR and ¹H and ¹³C NMR data of the chloro-bridged compound 4 showed that it has a planar structure. As indicated by IR and ¹H and ¹³C NMR, the acetate-bridged compound 5 has an open-book shape structure. This structure was further confirmed by X-ray diffraction. The comparison of the biochemical properties and antiproliferative activity of these compounds relative to the isostructural palladium compounds [Pd(4-OMeC₆H₄N═C(COC₆H₆)C₆H₄)X]₂ [X = AcO (1) and (2) or Cl (3)] indicated that the activity of compounds 4 and 5 is higher than that of the corresponding isostructural compounds 3 and 1–2, respectively, since their ID₅₀ are 2-9-fold lower. It seems that there are not differences in the antiproliferative activity of all of these compounds against leukemic HL-60 cells or mammary cancer MDA-MB 468 cells. Compounds 4 and 5 modify also the DNA structure of the oc and ccc forms of plasmid DNA. The acetate-bridged compound 5 showed the highest antiproliferative activity which is even higher than that of cis-DPP. Our data indicate that the Pt(II) compounds are more active than those having Pd(II) as the metal center.