Replacement of chlorides with dicarboxylate ligands in anticancer active Ru(II)-DMSO compounds: a new strategy that might lead to improved activity.

A series of new Ru(II)-DMSO complexes containing dicarboxylate ligands (dicarb), namely, oxalate (ox), malonate (mal), methylmalonate (mmal), dimethylmalonate (dmmal), and succinate (suc), have been synthesized and structurally characterized. These compounds were prepared from the known Ru(II)-Cl-DMSO anticancer complexes cis,fac-[RuCl2(DMSO-S)3(DMSO-O)] (1) and trans-[RuCl2(DMSO-S)4] (2) and from the chloride-free precursor fac-[Ru(DMSO-S)3(DMSO-O)3][CF3SO3]2 (3), with the aim of assessing how the nature of the anionic ligands influences the biological activity of these species. Basically, the investigated ligands can be divided into two groups.

The unprecedented bridging coordination mode of 1,1-cyclobutane dicarboxylate (mu-cbdc-O,O') stabilized by intramolecular hydrogen bonds in ruthenium(II) complexes.

The 1,1-cyclobutane dicarboxylate ligand (cbdc), that normally binds to metal centres as a chelate (eta(2)-cbdc-O,O'), prefers to bind in an unprecedented bridging fashion (micro-cbdc-O,O') on cationic Ru(ii) centres bearing ancillary ligands (e.g. H(2)O, NH(3)) capable of making intramolecular H-bonds with the non-coordinated oxygen atoms of the carboxylate groups.

Solution, solid state and biological characterization of ruthenium(III)-DMSO complexes with purine base derivatives.

Two new complexes of Ru(III) with purine base derivatives, [mer-RuCl(3)(acv)(DMSO-S)(C(2)H(5)OH)].C(2)H(5)OH (1) (acv=acyclovir, DMSO=dimethyl sulfoxide) and [trans-RuCl(4)(guaH)(DMSO-S)].2H(2)O (2) (guaH=protonated molecule of guanine), were prepared from the same Ru(III) precursor, [trans-RuCl(4)(DMSO-S)(2)](-), by substitution of one DMSO-S.

Reduction of in vivo lung metastases by dinuclear ruthenium complexes is coupled to inhibition of in vitro tumour invasion.

Mononuclear ruthenium-dmso compounds showed interesting antimetastatic properties on experimental models of solid tumours. In line with the interesting results with multinuclear platinum complexes, which proved to overcome cisplatin resistance, we thought it worthwhile to test the pharmacological properties of some dinuclear ruthenium complexes to ascertain the possible advantages due to the introduction of a second metal centre over NAMI-A and its mononuclear analogues. These compounds belong to the general formula X2[[RuCl4(dmso-S)]2(mu-L)] or [X][[RuCl4(dmso-S)](mu-L)[RuCl3(dmso-S)(dmso-O)]] where L is a nitrogen donor ligand (pyrazine; pyrimidine; 4,4'-bipyridine; 1,2-bis(4-pyridyl)ethane; 1,2-bis(4-pyridyl) ethylene; 1,3-bis(4-pyridyl)propane) and X a counterion.

Distinct effects of dinuclear ruthenium(III) complexes on cell proliferation and on cell cycle regulation in human and murine tumor cell lines.

We have examined the biological and antitumor activity of a series of dinuclear ruthenium complexes. The aim of this study was to compare the in vitro effects of these new compounds on cell proliferation, cell distribution among cell cycle phases, and the expression of some proteins involved in cell cycle regulation. Results obtained show a mild cytotoxic activity against human and murine cell lines, more evident after prolonged exposure of cell challenge.

Ruthenium-based NAMI-A type complexes with in vivo selective metastasis reduction and in vitro invasion inhibition unrelated to cell cytotoxicity.

A series of analogues of NAMI-A, a reference compound active on solid tumor metastases, were synthesized (NAMI-A type complexes). They share the same chemical structure of NAMI-A, and differ from it in the nature of the coordinated nitrogen ligand, such as pyrazole, thiazole and pyrazine, which are less basic than imidazole. This modification confers to the new NAMI-A type complexes a better stability in aqueous solution compared to the parent compound, a very important characteristic for a class of compounds that, with NAMI-A, is currently completing a phase I clinical trial at the Netherlands Cancer Institute of Amsterdam.

Synthesis and structural, spectroscopic, and electrochemical characterization of new ruthenium dimethyl sulfoxide nitrosyls.

The reactivity of ruthenium(II)- and ruthenium(III)-chloride-dimethyl sulfoxide precursors and of the antimetastatic drug [ImH][trans-RuCl(4)(dmso-S)(Im)] (NAMI-A, Im = imidazole, dmso = dimethyl sulfoxide) toward NO was investigated. Treatment of [(dmso)(2)H][trans-RuCl(4)(dmso-S)(2)] and mer-RuCl(3)(dmso)(3) with gaseous NO yielded [(dmso)(2)H][trans-RuCl(4)(dmso-O)(NO)] (1) and mer,cis-RuCl(3)(dmso-O)(2)(NO) (2), respectively. Thus, coordination of the strong pi-acceptor NO induces a S to O linkage isomerization of the dmso trans to it to avoid competition for pi-electrons.