CHARACTERIZATION OF (1,2-CYCLOHEXANEDIAMINE)PLATINUM(II) ISOMERS AND THEIR D(GPG) ADDUCTS BY MEANS OF H-1-NMR SPECTROSCOPY - A MINOR STRUCTURAL-CHANGE INDUCED BY THE ISOMERS

Diastereoisomers obtained from the reaction of d(GpG) with the three isomers of Pt(1,2-cyclohexanediamine)2+have been investigated by means of high-resolution 1H NMR spectroscopy. The reaction of d(GpG) with each Pt(R,R/S,S/R,S-dach)2+gave a G-N7, G-N7 adduct (dach = 1,2-cyclohexanediamine), abbreviated as Pt(R,R/S,S/R,S-dach)(d(GpG)-N7,N7), with an anti-anti configuration of the two guanines. Comparison of the NMR spectra of Pt(R,R-dach)(d(GpG)) and Pt(S,S-dach)(d(GpG)) indicates that a difference in the conformations (λ and δ) of the five-membered chelate ring (Pt(R,/S,S-dach) moiety) induces a minor change in the structure of the bound d(GpG) moiety. Two isomers produced from the reaction of d(GpG) with Pt(R,S-dach)2+could be separated by means of HPLC and were characterized by NMR spectral analysis. The structures were compared with those of earlier reported adducts with cis-Pt(NH3)22+. The steric effect of the cyclohexane and the chelate rings — being expected in the case of a reaction with the -GpG- sequence in DNA —will be discussed. © 1990, American Chemical Society. All rights reserved.