Ternary Complexes of cis-(NH₃)₂PtCl₂ (cis-DDP) With Guanosine (guo), Cytidine (cyd) and the Aminoacids Glycine (gly), L-Alanine (ala), L-2-Aminobutyric Acid (2-aba), L-Norvaline (nval) and L-Norleucine (nleu)

Abstract

The ternary complexes of formulae cis-[(NH₃)₂Pt(nucl)(amac)]NO₃, where nucl = guo and cyd (guanosine and cytidine) and amac = the deprotonated aminoacids glycine (gly), L-alanine (ala), L-2-aminobutyric acid (2-aba), L-norvaline (nval) and L-norleucine (nleu), were prepared from the reactions of the binary chelated ones cis-[(NH₃)₂Pt(nucl)(amac)]NO₃ with the nucleosides.

They were characterized by ¹H, ¹³C and ¹⁹⁵Pt NMR and IR spectra, together with elemental analysis and conductivity measurements. The aminoacids coordinate with Pt(II) in the ternary complexes with their terminal -NH₂ groups, guo through N₇ and cyd through N₃. Ligand-ligand hydrophobic interactions were also observed in the ternary complexes and were stronger with longer aliphatic chains of the aminoacids. The ³E sugar conformation increased by 5-7% in the ternary systems, as compared to the free nucleosides, while the percentage of the gg conformation remained almost constant and the one of the anti conformation of the sugar increased also slightly. Finally, the h conformer around the C_α-C_β bonds of the aminoacids reached a maximum in the binary systems and decreased again considerably in the ternary ones.

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