Synthesis, characterization, and properties of a group of platinum (IV) complexes

The synthesis, characterization, and antitumor properties of a group of platinum (IV) complexes is presented. The compounds, formed by oxidation of cis-dichlorodiammineplatinum (II) (1) or its cis-dihydroxo analogue, were characterized by elemental analysis and infrared and 195Pt NMR spectroscopies. EPR studies of aqueous solutions containing the spin trap phenyl-tert-butylnitrone and various platinum(IV) complexes revealed that the compounds are incapable of producing radical species which may in turn cause DNA breakage. It appears that the antitumor activity of the compounds is either due to Pt(IV) binding via ligand displacement to important cellular components or through the ability of the compounds to undergo in vivo reduction to platinum (II) species, which in turn exert their cytotoxic effects in a manner analogous to 1. As a group, the platinum(IV) compounds were found to be significantly less active against L-1210 leukemia than the parent platinum(II) complex, 1.