Enantioselectivity and stereoselectivity in the reactions of the enantiomers of the platinum complex [PtCl2(ahaz)] (ahaz = 3(R)- or 3(S)-aminohexahydroazepine) with DNA

The platinum–DNA adduct profile formed by the R- and S-enantiomers of [PtCl2(ahaz)] (ahaz = 3(R)-aminohexahydroazepine or 3(S)-aminohexahydroazepine) on reaction with salmon sperm DNA were characterised using HPLC and GFAAS (graphite furnace atomic absorption spectrometry) analyses. At a platinum to nucleotide ratio (Rt) equalling 0.05, the R-enantiomer forms a substantially larger amount (approximately 60%) of monofunctional adducts than the S-enantiomer (less than 35%). Fewer intrastrand GpG adducts are formed by the R-enantiomer (approximately 21%) than the S-enantiomer (approximately 37%). For both enantiomers, two isomeric GpG adducts, corresponding to the different orientations of the primary amine of ahaz ligand with respect to the O6 atom of the 5′ guanine, were observed in the ratios of 1:1.3 and 1:4.3 for the R- and S-enantiomers, respectively. The reasons for this enantioselectivity and stereoselectivity are discussed.