Issue 21, 2010

Quinoxaline-2-carboxamide as a carrier ligand in two new platinum(ii) compounds: Synthesis, crystal structure, cytotoxic activity and DNA interaction

Abstract

The search for platinum compounds structurally different from cisplatin has led to two new platinum(II) compounds containing quinoxaline-2-carboxamide as a carrier ligand, i.e. cis-[Pt(qnxca)(MeCN)Cl2] (1) and the [Pt(qnxca−H)(dmso)Cl] (2). Both compounds have been synthesized and characterized using different spectroscopic methods. In addition, single-crystal structures have been determined by X-Ray diffraction for both compounds. In each case a square planar Pt(II) is present; in (1) the qnxca is monodentate and neutral, whereas in (2) the ligand has lost a hydrogen, to form the anionic chelating ligand abbreviated as qnxca−H. The biological activity of both compounds has been investigated in a panel of seven human tumour cells, displaying poor cytotoxic activity, compared to cisplatin. The interaction of the new compounds with 1 or 2 equiv. of 9-ethylguanine has been studied using 1H NMR, 195Pt NMR and ESI-MS spectroscopy, finding poor reactivity of 1 towards the model base, forming only the monosubstituted adduct. Surprisingly, compound 2, which is more sterically crowded, interacts more efficiently with the 9-EtG, forming a bifunctional adduct with two 9-EtG with substitution of the dmso and the chloride ligand. Unwinding studies of pUC19 plasmid DNA by compound 1 show similar unwinding properties to cisplatin.

Graphical abstract: Quinoxaline-2-carboxamide as a carrier ligand in two new platinum(ii) compounds: Synthesis, crystal structure, cytotoxic activity and DNA interaction

Supplementary files

Article information

Article type
Paper
Submitted
20 Jan 2010
Accepted
01 Apr 2010
First published
26 Apr 2010

Dalton Trans., 2010,39, 5152-5158

Quinoxaline-2-carboxamide as a carrier ligand in two new platinum(II) compounds: Synthesis, crystal structure, cytotoxic activity and DNA interaction

P. Marqués-Gallego, M. A. Gamiz-Gonzalez, F. R. Fortea-Pérez, M. Lutz, A. L. Spek, A. Pevec, B. Kozlevčar and J. Reedijk, Dalton Trans., 2010, 39, 5152 DOI: 10.1039/C001158D

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