A novel (S,S)-R 2 eddip ester, O,O′-diisopentyl-(S,S)-ethylenediamine--N,N′-di-2-propanoate dihydrochloride (1) was synthesized and characterized by IR, 1 H-and 13 C-NMR spectroscopy, mass spectroscopy and elemental analysis. In vitro antitumor action of 1, and two more R 2 eddip esters, dialkyl (S,S)-ethylenediamine-N,N′-di-2-propanoate dihydrochlorides, obtained before (alkyl = n-Bu or n-Pe, 2 and 3, respectively), was determined against cervix adenocarcinoma (HeLa), human melanoma (Fem-x), human chronic myelogenous leukemia (K562) cells, and a non-cancerous cell line human embryonic lung fibroblast (MRC-5), using the microculture tetrazolium test MTT assay. Esters 1-3 showed higher cytotoxicity and better selectivity in comparison to cisplatin, used as reference compound. The highest activity was expressed by 1, with IC 50 (Fem-x) value of 1.51±0.09 µM.