The crown ether influence on ligand exchange reactions of Na2PtCl6 with glycine and D-(+)-alanine; synthesis and characterization of platinum(IV) amino acid complexes

Effect of the aniline fragment in Pt(II) and Pt(IV) complexes as anti-proliferative agents. Standard reduction potential as a more reliable parameter for Pt(IV) compounds than peak reduction potential

The problems of resistance and side effects associated with cisplatin and other chemotherapeutic drugs have boosted research aimed at finding new compounds with improved properties. The use of platinum(IV) prodrugs is one alternative, although there is some controversy regarding the predictive ability of the peak reduction potentials. In the work described here a series of fourteen chloride Pt(II) and Pt(IV) compounds was synthesised and fully characterised. The compounds contain different bidentate arylazole heterocyclic ligands. Their cytotoxic properties against human lung carcinoma (A549), human breast carcinoma (MCF7) and human colon carcinoma (HCT116 and HT29) cell lines were studied. A clear relationship between the type of ligand and the anti-proliferative properties was found, with the best results obtained for the Pt(II) compound that contains an aniline fragment, (13), thus evidencing a positive effect of the NH₂ group. Stability and aquation studies in DMSO, DMF and DMSO/water mixtures were carried out on the active complexes and an in-depth analysis of the two aquation processes, including DFT analysis, of 13 was undertaken. It was verified that DNA was the target and that cell death occurred by apoptosis in the case of 13. Furthermore, the cytotoxic derivatives did not exhibit haemolytic activity. The reduction of the Pt(IV) compounds whose Pt(II) congeners were active was studied by several techniques. It was concluded that the peak reduction potential was not useful to predict the ability for reduction. However, a correlation between the cytotoxic activity and the standard reduction potential was found.

Compounds of glycine with halogen or metal halogenides: review and comparison

The large family of glycine halogenides and metal halogenides encompasses a high variety of different crystal structures. The role of the glycine molecule as a structural unit as a mono-, bi- or tridentate ligand, of the halogenide ions as well as the composition and condensation of the cationic polyhedra is discussed. With respect to the connectivity of the building units, five different structure families of glycine halogenides and glycine-metal halogenides can be distinguished. Parameters such as symmetry, ionic radii, electronegativity of cation and anion and their difference, charge, coordination number, hydration states, stoichiometric ratios and connectivity were weighed against each other in order to see if any correlations exist. The data suggest that cations with high electronegativities seem to promote formation of structures with a low grade of connectivity, i.e., isolated units, and vice versa.

Platinum(IV) complexes with dipeptide. X-ray crystal structure, 195Pt NMR spectra, and their inhibitory glucose metabolism activity in Candida albicans

Three dipeptide complexes of the form K[Pt(IV)(dipep)Cl3] and two complexes of the form K[Pt(IV)(Hdipep)Cl4] were newly prepared and isolated. The platinum(IV) complexes containing the dipeptide were obtained directly by adding KI to H2[PtCl6] solution. The reaction using KI was rapidly completed and provided analytically pure yellow products in the form of K[Pt(dipeptide)Cl3] for H2digly, H2gly(alpha)-ala, H2alpha-alagly and H2di(alpha)-ala. The K[Pt(IV)(digly)Cl3] complex crystallizes in the monoclinic space group P2(1)/c with unit cell dimensions a = 10.540(3) A, b = 13.835(3) A, c = 8.123(3) A, beta = 97.01(2) degrees, Z = 4. The crystal data represented the first report of a Pt(IV) complex with a deprotonated peptide, and this complex has the rare iminol type diglycine(2-) coordinating to Pt(IV) with the bond lengths of the C2-N1 (amide) bond (1.285(13) A). The 195Pt NMR peaks of the K[Pt(IV)(dipep)Cl3] and the K[Pt(IV)(Hdipep)Cl4] complexes appeared at about 270 ppm and at about -130 ppm, respectively, and were predicted for a given set of ligand atoms. While the K[Pt(IV)(x-gly)Cl3] complexes, where x denotes the glycine or alpha-alanine moieties, were easily reduced to the corresponding platinum(II) complexes, the K[Pt(IV)(x-alpha-ala)Cl3] complexes were not reduced, but the Cl- ion was substituted for OH- ion in the reaction solution. The K[Pt(digly)Cl3] and K[Pt(gly-L-alpha-ala)Cl3] complexes inhibited the growth of Candida albicans, and the antifungal activities were 3- to 4-fold higher than those of cisplatin. The metabolism of glucose in C. albicans was strongly inhibited by K[Pt(digly)Cl3] and K[Pt(gly-L-alpha-ala)Cl3] but not by the antifungal agent fluconazole.

The First Platinum(IV) Complexes with Glucopyranoside Ligands. A New Coordination Mode of Carbohydrates

[(PtMe(3)I)(4)] reacts with AgBF(4) in acetone to give fac-[PtMe(3)(Me(2)CO)(3)]BF(4) (2) which was isolated as strongly moisture and air sensitive, colorless crystals and characterized by microanalysis and NMR spectroscopy ((1)H, (13)C, (195)Pt). The X-ray structure analysis (orthorhombic, Pcab, a = 15.599(3) Å, b = 15.685(2) Å, c = 15.763(3) Å, Z = 8) reveals that 2 is monomeric and that the cation exhibits local C(3)(v)() symmetry. The reaction of 2 with glucopyranoses (1,6-anhydro-beta-D-glucopyranose (3a), 1-methyl-alpha-D-glucopyranoside (3b), and 1-phenyl-beta-D-glucopyranoside (3c)) yields carbohydrate complexes [PtMe(3)L]BF(4) (4a-4c, L = 3a-3c). The complexes were characterized by microanalysis, ESI mass spectrometry and by NMR spectroscopy ((1)H, (13)C, (195)Pt) displaying that the carbohydrates act as tridentate chelating ligands coordinated by the hydroxyl groups 2-OH and 4-OH and by the acetal oxygen atom of the pyranose ring. This structure was also confirmed by X-ray structure analysis of 4a (orthorhombic, P2(1)2(1)2(1), a = 6.404(1) Å, b = 8.636(2) Å, c = 27.161(5) Å, Z = 4). The cyclic system of the two five-membered and the one six-membered 1,3,2-dioxaplatina rings is not free from angle strain; two O-Pt-O angles are distinctly smaller than 90 degrees (O2-Pt-O5 73.6(2), O4-Pt-O5 75.6(2) degrees ). The Pt-O bond to the acetal oxygen atom in the pyranose ring is significantly longer (Pt-O5 2.288(5) Å) than the two Pt-OH bonds (Pt-O2 2.246(5), Pt-O4 2.248(4) and belongs to the longest Pt-O bonds at all.