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Pure Appl. Chem., 2013, Vol. 85, No. 2, pp. 355-364

Published online 2012-12-29

Cisplatin-related drugs for nongenomic targets: Forcing the reactivity with nucleobases

Sandra Angelica De Pascali1, Antonella Muscella1, Santo Marsigliante1, Maria Grazia Bottone2, Graziella Bernocchi2 and Francesco Paolo Fanizzi3,1*

1 Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Universitá del Salento, via Lecce-Monteroni 73100 Lecce, Italy
2 Dipartimento di Biologia Animale, Laboratorio di Biologia Cellulare e Neurobiologia, Universitá di Pavia, Istituto di Genetica Molecolare CNR, Via Ferrata 1, 27100 Pavia, Italy
3 Consortium C.A.R.S.O., Cancer Research Center, I-70100, Valenzano-Bari, Italy

Abstract: The products obtained by forcing the reaction with nucleosides (guanosine, Guo, and adenosine, Ado) of potential anticancer drugs for nongenomic targets [PtCl(O,O'‑acac)(L)] (L = dimethyl sulfoxide, DMSO; dimethyl sulfide, DMS), closely related to their very powerful organometallic analogues [Pt(O,O'-acac)(γ-acac)(L)], have been studied. [PtCl(O,O'-acac)(L)] and [Pt(O,O'-acac)(γ-acac)(L)] complexes were reported unreactive toward nucleobases. Aquo species [Pt(O,O'-acac)H2O(L)]+, obtained from [PtCl(O,O'‑acac)(L)] by Ag+ driven coordinated Cl removal, gave access to [Pt(O,O'-acac)(L)(nucleoside)]+ ([Pt(O,O'-acac)(DMSO)(Guo)]+, [Pt(O,O'‑acac)(DMS)(Guo)]+, [Pt(O,O'-acac)(DMSO)(Ado)]+). The effect of the chelate oxygen donor acac (with respect to a chelate diammine), the role of the sulfur ligand (DMSO, DMS), and the influence of the purinic nucleoside itself on the coordinated Guo or Ado dynamic motions in [Pt(O,O'-acac)(L)(nucleoside)]+ complexes have been investigated by NMR spectroscopy. Interestingly, a slow rotation of nucleobase around the Pt–N(7) bond with formation of two rotamers was observed already at room temperature only in the case of [Pt(O,O'-acac)(DMSO)(Guo)]+. On the other hand, no hindered rotation at room temperature was detected in the analogous [Pt(O,O'-acac)(DMS)(Guo)]+ and [Pt(O,O'‑acac)(DMSO)(Ado)]+ complexes. Data suggest that rotation of the nucleoside in [Pt(O,O'-acac)(L)(nucleoside)]+ is very different with respect to the analogous [Pt(diammine)(L)(nucleoside)]2+ systems, due to specific interactions between the acac chelate ligand, the DMSO, and the nucleobase.