Preparation of antitumor platinum(II) complexes of 1,2-diphenylethylenediamine isomers and their interactions with DNA and its purine moieties.

A series of Pt(II) complexes containing 1,2-diphenylethylenediamine (stien) isomers were synthesized and tested for their antitumor activity against leukemia L1210. Among the Pt(II) complexes examined water-soluble Pt(II) complexes with sulfate, nitrate and D-glucuronate ions as leaving groups exhibited relatively high antitumor activity. Furthermore, the interactions between calf-thymus DNA and Pt(SO4) (stein) complexes were investigated by means of circular dichroism spectrometry. Dichroism enhancements observed in the interaction between DNA and Pt(SO4) (stien) complexes were analysed to be contributable to two factors: (1) vicinal effects of DNA on the d-d transitions of Pt(II) ions and (2) conformational changes of DNA caused by the coordination of cis-configurational Pt(II) complexes.