Synthesis, characterization, and antitumor activity of 1,2-bis(diphenylphosphino) ethane platinum(II) and palladium(II) complexes

Heteroleptic enantiopure Pd(ii)-complexes derived from halogen-substituted Schiff bases and 2-picolylamine: synthesis, experimental and computational characterization and investigation of the influence of chirality and halogen atoms on the anticancer activity

To investigate the effect of chirality and different halogen substituents on the anticancer activity, seven enantiomeric pairs of palladium complexes were synthesized and characterized.

Novel anticancer PdII complexes: The effect of the conjugation of transferrin binding peptide and the nature of halogen coordinated on antitumor activity

A series of Pd^II complexes with bis-(2-pyridylmethyl)glycine as a ligand of formula [PdX(bis-(2-pyridylmethyl)glycine)] where X = Cl, Br, I were prepared and the effect of the halogen nature in the antitumor activity of eight tumorigenic and one non-tumorigenic cell line was evaluated. The chloride derivative was further functionalized with a transferrin receptor binding peptide, generating the first Pd^II based metallopeptide. Its antitumor activity was also evaluated. However, among all the complexes, the chloride and iodine parent compounds showed the lowest GI₅₀ values in the panel evaluated, and lowest GI₅₀ than cisplatin in several cell lines. In contrast, the bromine derivative showed higher values of GI₅₀ than chloride and iodine (around 30 - 50 μM). The same trend was observed for the bovine serum albumin binding constant with higher values for iodine, chlorine, and bromine in this order. In aqueous solution, the chloride is exchanged by water while the bromine and iodine are not. DNA was evaluated as a target and showed no significative interaction for all the compounds. The results suggest sulfur-rich proteins and not DNA as a target. This report represents the first Pd^II metallopeptide reported, its evaluation in solution and antitumor activity. This work opens the possibilities for further functionalization of Pd^II complexes and the importance of the halogen coordination in the design of novel metallodrugs.

Synthesis, characterization and biological investigation of platinum(ii) complexes with asparagusic acid derivatives as ligands

After more than 50 years of platinum-based anticancer research only three compounds are in clinical use worldwide. The use of the well-known lead compound of this class of anticancer agents, cisplatin, is limited by its side effects and varying resistance mechanisms. Therefore, we report on platinum(ii) compounds with asparagusic acid derivatives as ligands which show interesting anticancer results on cisplatin resistant cell lines.

Palladium-Catalyzed Synthesis of Amidines via tert-Butyl isocyanide Insertion

Para-substituted iodobenzenes were reacted with tert-butyl isocyanide and piperidine as nucleophiles in the presence of palladium-diphosphine catalysts. Both single and double insertion of the isocyanide was observed and the corresponding amidines and ketimine-amidines were obtained in yields of practical interest. With the increase of the tert-butyl isocyanide/iodobenzene ratio, 100% chemoselectivity toward the ketimine-amidine was achieved. The formation of the products was rationalized on the basis of a catalytic cycle analogous to that of the aminocarbonylation reactions. Clear connection was found between the activity and the electronic structure of the proposed catalyst Pd(diphosphine) by computational studies, as the more negative partial charge on palladium resulted in higher conversion. Among five isocyanide substrates, only tert-butyl isocyanide was proved to be active.

Synthesis and antiproliferative activity of a series of new platinum and palladium diphosphane complexes

New organometallic complexes [M(dppe)(R)₂] {where M = Pt or Pd, dppe = 1,2-bis(diphenylphosphano)ethane, and R = C₆F₄H-x (x = 6,5,4), C₆F₃H₂-3,5, C₆F₃H₂-5,6, C₆F₃H₂-3,6, C₆F₄(OMe)-4, and C₆F₄(cyclo-C₅H₁₀N)-4, the numbers x refer to the positions of the protons in the polyfluoroaryl ligands} were synthesised either through transmetalation from the dichlorido complexes [M(dppe)Cl₂] or through ligand exchange using [M(diene)Cl₂] precursor complexes with diene = 1,5-cyclooctadiene (cod) or 1,5-hexadiene (hex). Alternatively, [M(dppX)Cl(R)] complexes with dppX = dppm (1,1-bis(diphenylphosphano)methane), dppe, dppp (1,3-bis(diphenylphosphano)propane), and dppb (1,4-bis(diphenylphosphano)butane) were prepared in decarboxylation reactions from thallium(i) carboxylates Tl(O₂CR). The different preparative methods were compared in terms of yield and purity. Structural and spectroscopic data are reported for the new dppX- and diene-M(R)₂ complexes. Antiproliferative activity was investigated for these new complexes against the HT-29 (colon carcinoma) and MCF-7 (breast adenocarcinoma) cell lines, and the active compounds of this first series together with organometallic dppX or hex Pt^II or Pd^II complexes were then included in cell tests using L1210 (leukaemia cells) and the cisplatin-resistant L1210/DDP cell line. Remarkably, promising antiproliferative results were found for a few Pt^II and Pd^II complexes, while structurally closely related compounds were essentially nontoxic.

Cytotoxic activity of platinum (II) complexes with tri-n-butylphosphine. Crystal structure of the dinuclear hydrazine-bridged complex, cis,cis-[PtCl(PBu3n)2(mu-N2H4)PtCl(PBu3n) 2] (ClO4)2.2CHCl3

A series of platinum(II) tri-n-butylphosphine complexes having the formulas cis-[PtCl2L2], NEt4[PtCl3L], [PtCl(en)L]Cl, [Pt(en)L2](ClO4)2, sym-trans-[Pt2Cl4L2], [Pt2Cl2L4](ClO4)2, trans,trans-[PtCl2L(mu-N2H4)PtCl2L] trans,trans-[PtCl2L(mu-en)PtCl2L], and cis,cis-[PtClL2(mu-N2H4)PtClL2](ClO4)2 (L = tri-n-butylphosphine; en = ethylenediamine) have been synthesized and their cytotoxic activity in vitro and in vivo has been studied. The solution behavior of the novel dinuclear diamine-bridged platinum(II) complexes has been investigated by means of UV and 31P NMR spectroscopy. For the ionic hydrazine compound cis,cis-[PtClL2(mu-N2H4)PtClL2](ClO4)2, an x-ray structure determination is reported. Crystal data: space group P2(1)/a, a = 17.803(1), b = 18.888(3), c = 12.506(3) A, beta = 107.97(2) degrees, Z = 2, R = 0.052, RW = 0.058. The platinum coordination is approximately square-planar, with the bond lengths Pt-Cl = 2.358(5), Pt-N = 2.15(1), Pt-P(trans to Cl) = 2.260(5), and Pt-P(trans to N) = 2.262(6) A. All investigated compounds were cytotoxic in vitro against L1210 cells and showed no cross-resistance to cisplatin. On the other hand, no antitumor activity was observed vs L1210 leucemia in DBA2 mice.