Stereospecific ligands and their complexes. Part VII. Synthesis, characterization and in vitro antitumoral activity of platinum(II) complexes with O,O'-dialkyl esters of (S,S)-ethylenediamine-N,N'-di-2-(4-methyl)pentanoic acid.

Platinum(II) complexes (1-4) with bidentate N,N'-ligands, O,O'-dialkyl esters (alkyl = ethyl, n-propyl, n-butyl and n-pentyl), of (S,S)-ethylenediamine-N,N'-di-2-(4-methyl)pentanoic acid were synthesized and characterized by IR, (1)H NMR and (13)C NMR spectroscopy and elemental analysis. DFT calculations were performed for the complexes and it was found that only one diastereoisomer could be formed. Cytotoxic activity of complexes 1-4 was determined against chronic lymphocytic leukemia cells (CLL) and compared to the activity of ligand precursors L1 · 2HCl-L4·2HCl and corresponding palladium(II) complexes, [PdCl(2)L] (L = L1-L4). The complexes were found to exhibit significantly higher antitumor activities than cisplatin on CLL cells. Cytotoxic effect of platinum(II) complexes on CLL cells was higher compared to corresponding palladium(II) complexes. In addition the mode of cell death induced by platinum(II) complexes was determined.