Carbohydrate effect of novel arene Ru(II) phenanthroline-glycoconjugates on metastatic biological processes.

Novel water-soluble half-sandwich ruthenium(II) polypyridyl-glycoconjugates [Ru(p-cymene)Cl{N-(1,10-phenanthroline-5-yl)-ß-glycopyranosylamine}][Cl] (glycopyranosyl = d-glucopyranosyl (1), D-mannopyranosyl (2), L-rhamnopyranosyl (3) and l-xylopyranosyl (4)) have been synthesized and fully characterized. Their behaviour in water under physiological conditions has been studied by nuclear magnetic resonance spectroscopy, revealing their hydrolytic stability. Interactions of the novel compounds with duplex-deoxiribonucleic acid (dsDNA) were investigated by different techniques and the results indicate that, under physiological pH and saline conditions, the metal glycoconjugates bind DNA in the minor groove and/or through external, electrostatic interactions, and by a non-classical, partial intercalation mechanism in non-saline phosphate buffered solution. Effects of compounds 1-4 on cell viability have been assessed in vitro against two human cell lines (androgen-independent prostate cancer PC-3 and non-tumorigenic prostate RWPE-1), showing moderate cytotoxicities, with IC50 values higher than those found for free ligands [N-(1,10-phenanthroline-5-yl)-ß-glycopyranosylamine] (glycopyranosyl = d-glucopyranosyl (a), D-mannopyranosyl (b), L-rhamnopyranosyl (c) and l-xylopyranosyl (d)) or corresponding metal-aglycone. Cell viability was assayed in the presence and absence of the glucose transporters (GLUTs) inhibitor [N4-{1-(4-cyanobenzyl)-5-methyl-3-(trifluoromethyl)-1H-pyrazol-4-yl}-7-fluoroquinoline-2,4-dicarboxamide] (BAY-876), and the results point to a negligible impact of the inhibition of GLUTs on the cytotoxicity caused by Ru(II) compounds 1-4. Remarkably, glycoconjugates 1-4 potently affect the migration pattern of PC-3 cells, and the wound healing assay evidence that the presence of the carbohydrate and the Ru(II) center is a requisite for the anti-migratory activity observed in these novel derivatives. In addition, derivatives 1-4 strongly affect the matrix metalloproteinase MMP-9 activities of PC-3 cells, while proMMP-2 and especially proMMP-9 were influenced to a much lesser extent.

Ring-Opening Polymerization of L-Lactide Catalyzed by Potassium-Based Complexes: Mechanistic Studies.

Two non-toxic potassium compounds, 1 and 2, with a commercial oximate ligand have been prepared and fully spectroscopically characterized. Their activity as catalysts for the ring-opening polymerization (ROP) process of LLA has been studied, showing that they are extremely active and able to polymerize the monomer in a few minutes. For derivative 2, the presence of a crown ether in the potassium coordination sphere affects the nuclearity of the compound and consequently its solubility, with both aspects having an influence in the polymerization process. Detailed studies of the polymerization mechanism have been performed, and an unusual anionic mechanism was observed in absence of a co-initiator. Indeed, the monomer deprotonation generates a lactide enolate, which initiates the polymerization propagation. On the contrary, when a 1:1 ratio of cat:BnOH is used, a mixture of mechanisms is observed, the anionic mechanism and the activated monomer one, while from a cat:BnOH ratio of 1:2 and over, only the activated monomer mechanism is observed.

Stereoselective synthesis of oxime containing Pd(II) compounds: highly effective, selective and stereo-regulated cytotoxicity against carcinogenic PC-3 cells.

New palladium compounds [Pd{(1S,4R)-NOH^NH(R)}Cl2] (R = Ph 1a or Bn 1b), [Pd{(1S,4R)-NOH^NH(R)}{(1S,4R)-NO^NH(R)}][Cl] (R = Ph 2a or Bn 2b) and corresponding [Pd{(1R,4S)-NOH^NH(R)}Cl2] (R = Ph 1a' or Bn 1b') and [Pd{(1R,4S)-NOH^NH(R)}{(1R,4S)-NO^NH(R)}][Cl] (R = Ph 2a' or Bn 2b') have been synthesized. Novel compounds 1a, 1b, and 2b (and 1a', 1b', and 2b') were obtained in solution as a mixture of diastereomers whose relative ratios depend on the solvent and the nature of the amino substituent. In contrast, the synthetic reactions of derivatives 2a and 2a' were stereospecific, and afforded single enantiomers of absolute configuration (SN,1SC,4RC)-(RN,1SC,4RC) and (RN,1RC,4SC)-(SN,1RC,4SC), respectively. All compounds have been fully characterized by NMR and IR spectroscopy, time-dependent UV-spectroscopy, ESI-HR-MS in water, and CHN elemental analysis. Absolute configurations of the major epimers of 1a and 1a', both epimers of 1b and enantiomer 2a', were determined by single crystal X-ray crystallography, and confirmed by 2D NOESY NMR experiments in solution. Additionally, the pH-dependent stability of 2b in water was assessed by 1H-NMR spectroscopy. Metal derivatives have been tested in vitro against three human cancer (prostate PC-3, cervical HeLa, and breast MCF-7) cell lines. The highest anticancer activities were shown by palladium compound 2a' in all cancer cells, with IC50 values up to 80 times lower than those found for cisplatin. The cytotoxicity of 2a and 2a'' is stereo-dependent, with IC50 values that differ significantly for each enantiomer in all the cell lines tested. The cytotoxic activity of 2a and 2a' was further evaluated against the non-tumorigenic human prostate RWPE-1 cell line, revealing a selectivity index (SI) of ca. 30 for derivative 2a'. DNA interactions have been investigated by equilibrium dialysis, fluorescence resonance energy transfer (FRET) DNA melting assays, and viscometric titrations, pointing to groove and/or external binding. Cell cycle assay on PC-3 cells after treatment with 2a or 2a' shows cell cycle arrest in the S and G2/M phases, especially when the cells are treated with compound 2a'.

Water soluble, optically active monofunctional Pd(ii) and Pt(ii) compounds: promising adhesive and antimigratory effects on human prostate PC-3 cancer cells.

New water soluble, enantiopure palladium and platinum compounds RN-[M{(1S,4R)-κNOH,κ2NH(2-pic)}Cl]Cl and SN-[M{(1R,4S)-κNOH,κ2NH(2-pic)}Cl]Cl (2-pic = 2-picolyl, M = Pd 1 and 1', Pt 2 and 2', respectively), and heterometallic Pd/Ti [(η5-C5H5)2Ti{(1S,4R)-κON,κ2NH(2-pic)}(PdCl)]Cl (3) have been synthesized. These novel compounds were fully characterized by NMR spectroscopy and CHN elemental analysis and 1, 1', 2 and 2' were further evaluated by polarimetry, ultra-violet and circular dichroism spectroscopy. The aqueous stability of novel compounds was studied by NMR spectroscopy under physiological conditions and the new species detected under such conditions have been characterized by NMR techniques and HR-ESI-MS (High-Resolution Electrospray Ionization Mass Spectrometry). Compound-DNA interactions have been investigated for the palladium and platinum compounds by equilibrium dialysis, Fluorescence Resonance Energy Transfer (FRET) DNA melting assays and viscometric titrations, revealing a better binding affinity and ability to affect duplex DNA of the palladium compounds. Metal derivatives have been tested in vitro against three cancer (prostate PC-3, cervical HeLa and breast MCF-7) and one non-tumorigenic (human prostate RWPE-1) cell lines. The highest anticancer activities were shown by palladium compounds 1 and 1' in all cancer lines, although their toxicity was lower than that found for cisplatin. Most importantly, the effect of the compounds on the cell adhesion and migration of the androgen-independent prostate cancer PC-3 cells has been assessed, and the efficacy of Pd enantiomers to affect the invasive phenotype of PC-3 cells has been demonstrated.

Heterobimetallic aluminate derivatives with bulky phenoxide ligands: a catalyst for selective vinyl polymerization.

New aluminium-alkali metal heterometallic compounds using the bulky ligand OAr = 2,6-bis(diphenylmethyl)-4-tert-butylphenoxide have been synthesized and characterized. The species obtained, [MAlMe3(OAr)] (M = Li(2a), Na(2b), K(2c)) and [MAlMe2(OAr)2] (M = Li(3a), Na(3b), K(3c)), include some of the few heterobimetallic examples of aluminate complexes with O-donor ligands described so far. Their activity in polymerization towards a difunctional monomer, such as Glycidyl Methacrylate (GMA), was evaluated. The compounds were revealed to be able to polymerize the acrylate groups via vinyl polymerization. Interestingly, the homometallic counterparts [AlXMe(OAr)] (X = Cl, Me), previously described by us, are very active in ROP processes of GMA. The combined polymerization process using both catalysts has also been explored to obtain a polymeric material with an exciting macromolecular architecture.

Aluminates with Fluorinated Schiff Bases: Influence of the Alkali Metal⁻Fluorine Interactions in Structure Stabilization.

New heterometallic aluminium-alkali metal compounds have been prepared using Schiff bases with electron withdrawing substituents as ligands. The synthesis of these new species was achieved via the reaction of AlMe3 with the freshly prepared alkali-metallated ligand. The derivatives formed were characterized by NMR in solution and by single crystal X-ray diffraction in the solid state. Aluminate derivatives with lithium and sodium were prepared and a clear influence of the alkali metal in the final outcome is observed. The presence of a Na···F interaction in the solid state has a stabilization effect and the species [NaAlMe3L]2 can de isolated for the first time, which was not possible when using Schiff bases without electron withdrawing substituents as ligands.

Interaction of an imidazolium-2-amidinate (NHC-CDI) zwitterion with zinc dichloride in dichloromethane: role as ligands and C-Cl activation promoters.

Adducts of imidazolium carbenes and carbodiimides (NHC-CDI) are emerging as a new class of thermally stable and modular zwitterions with many potential applications. Our study of the interaction of a representative NHC-CDI zwitterion with ZnCl2 in dichloromethane led to the serendipitous discovery of a highly selective, double activation of dichloromethane C-Cl bonds.

Schiff-base -ate derivatives with main group metals: generation of a tripodal aluminate metalloligand.

New heterobimetallic aluminates with well-defined structures bearing bidentate Schiff bases as ligands have been prepared. The ligands studied are PhO-CH[double bond, length as m-dash]N-Ar (Ar = C6H5 (La) and 2,6-iPr-C6H3 (Lb)), with and without donor substituents in the ortho position of the arene ring bonded to the iminic nitrogen. To prepare the heterometallic species, the HL proligands were treated with the appropriate alkali metal precursor and then AlMe3 was added. In these reactions the alkali metal size has a substantial influence on the outcome. For lithium, the formation of [LiAlMe3(L)]21(a-b) compounds was straightforward and their nuclearity in the solid state was confirmed by X-ray studies. When moving to sodium, the analogous species [NaAlMe3(L)]n initially formed, quickly evolved to [NaAlMe2(L)2]n3(a-b) in solution. As well, for potassium, the initial derivatives formed [KAlMe3L] progressed very rapidly to the generation of [KAlMe2L2] as evidenced from the isolation of [KAlMe2(Lb)2] 4b as a crystalline product. Furthermore, for potassium the unique species [KAlMe(Lb)3] 5b was isolated which shows, as a striking feature, the presence of an unusual tripodal metalloligand.

Biological evaluation of water soluble arene Ru(II) enantiomers with amino-oxime ligands.

New water soluble, enantiopure arene ruthenium compound SRuSN-(1R,4S)-[(η6-p-cymene)Ru{ĸNH(Bn),ĸNOH}Cl]Cl (Bn = benzyl, 1a') has been synthesized. The novel compound along with that previously described RRuRN-(1S,4R)-[(η6-p-cymene)Ru{ĸNH(Bn),ĸNOH}Cl]Cl (1a) was evaluated by polarimetry, ultra-violet and circular dichroism spectroscopy. The structure of novel ruthenium derivative 1a' was determined by single crystal X-ray crystallography. Both enantiomers have been tested against several cancer cell lines in vitro: prostate PC-3, lung A-549, pancreas MIA PaCa-2, colorectal HCT-116, leukemia Jurkat and cervical HeLa. Both enantiomers are active and versatile cytotoxic agents, showing IC50 values from 2 to 12 times lower than those found for cisplatin in the different cell lines evaluated. The mechanism of cell death induced by the metal compounds was analyzed in A-549 and Jurkat cell lines. Derivatives 1a and 1a' induced apoptotic cell death of A-549 cells while dose-dependent cell death mechanisms have been found in the Jurkat cell line. Compound-DNA interactions have been investigated by equilibrium dialysis, Fluorescence Resonance Energy Transfer (FRET) melting assays and viscometric titrations, revealing moderate binding affinity of 1a and 1a' towards duplex DNA. Finally, the efficacy of 1a in a preliminary in vivo assay of PC-3 xenografts in nude mice has been evaluated, resulting in a promising inhibition of tumor growth by 45%. Analysis of tumor tissue also showed a significant decrease of levels of crucial molecules in the invasive phenotype of PC-3 cells.

Synthesis of novel chiral heterometallic terpene oximates: unusual generation of an aluminium enolate by a cooperative effect.

Al-K heterometallic terpene oximate derivatives with uncommon structural features are reported. These species react with an aryl ketone leading to heterometallic enolates via an unusual route. Isolation of a remarkable heterometallic Al-K enolate confirms the cooperative mechanism proposed by DFT calculations, where the oximate ligand has a prominent role. From these enolates the formation of new C-C bonds is straightforward.

Novel enantiopure cyclopentadienyl Ti(IV) oximato compounds as potential anticancer agents.

The synthesis and characterization of new enantiopure cyclopentadienyl titanium oximato compounds (S,R)-[(η(5)-C5H5)Ti{к(2)NO,(R)NH·HCl}Cl2] (R=Ph (phenyl) 1a·HCl, Bn (benzyl) 1b·HCl, 2-pic (2-picolyl) 1c·HCl), (S,R)-[(η(5)-C5H5)TiCl2{к(2)NO,(Ph)NH}] (1a) and (S,R)-[(η(5)-C5H5)2TiCl{к(2)NO,(R)NH}] (R=Ph 2a, Bn 2b, 2-pic 2c), along with studies on their behavior in D2O at different pD values are reported. The structure of previously described ammonium-oxime (2S,5R)-{NOH,(Bn)NH·HCl} (b·HCl) and novel titanium derivative 1a have been determined by single crystal X-ray crystallography. The effect of the compounds on cytotoxicity, cell adhesion and migration of the androgen-independent prostate cancer PC-3 cells has been assessed. Compounds 2b and 2c are more cytotoxic than additive doses of titanocene dichloride and free oxime proligand, probing the synergistic effect of these novel compounds. The cytotoxicity of 2b and 2c has been further evaluated against human renal Caki-1, colon DLD-1 and triple negative breast MDA-MB-231 cancer cell lines. The activity found for 2c on PC-3 and Caki-1 is higher than that of highly active Titanocene Y (bis-[(p-methoxybenzyl)cyclopentadienyl]titanium(IV) dichloride), while showing selectivity against renal cancer when compared to a non-tumorigenic human renal (HEK-293T) cell line. Compounds 2b and especially 2c are apoptotic in Caki-1 cancer cell lines. Cell adhesion and wound-healing assays confirmed that derivatives 1c·HCl, 2b and 2c affect the adhesion and migration patterns of the PC-3 cell line. Interactions of the novel compounds with plasmid (pBR322) DNA have also been studied, showing that the oximato Ti(IV) derivatives have a weak or no interaction with DNA at physiological pH.

Hydrogen bonding and anticancer properties of water-soluble chiral p-cymene Ru(II) compounds with amino-oxime ligands.

The investigation of the hydrogen-bonding effect on the aggregation tendency of ruthenium compounds [(η6-p-cymene)Ru(κNHR,κNOH)Cl]Cl (R = Ph (1a), Bn (1b)) and [(η6-p-cymene)Ru(κ2NH(2-pic),κNOH)][PF6]2 (1c), [(η6-p-cymene)Ru(κNHBn,κNO)Cl] (2b) and [(η6-p-cymene)Ru(κNBn,κ2NO)] (3b), has been performed by means of concentration dependence 1H NMR chemical shifts and DOSY experiments. The synthesis and full characterization of new compounds 1c, [(η6-p-cymene)Ru(κNPh,κ2NO)] (3a) and 3b are also reported. The effect of the water soluble ruthenium complexes 1a-1c on cytotoxicity, cell adhesion and cell migration of the androgen-independent prostate cancer PC3 cells have been assessed by MTT, adhesion to type-I-collagen and recovery of monolayer wounds assays, respectively. Interactions of 1a-1c with DNA and human serum albumin have also been studied. Altogether, the properties reported herein suggest that ruthenium compounds 1a-1c have considerable potential as anticancer agents against advanced prostate cancer.

Heterometallic aluminates: alkali metals trapped by an aluminium aryloxide claw.

A series of heterometallic aluminium-alkali metal species [AlMMe2{2,6-(MeO)2C6H3O}2]n have been isolated for lithium, sodium and potassium. These compounds can be generated by the reaction of [AlMe2{2,6-(MeO)2C6H3O}]2 with the metallated phenol [M{2,6-(MeO)2C6H3O}]n or through the reaction of the mixture of AlMe3 and the appropriate alkali metal alkyl base with two equivalents of 2,6-dimethoxyphenol. In the heterometallic species obtained, the {AlMe2{2,6-(MeO)2C6H3O}2}(-) moiety is observed and could be described as a claw which fixes the alkali ion by the phenoxide oxygen atoms while the methoxy groups help to stabilize their coordination sphere. All compounds have been characterized by NMR spectroscopy and X-ray diffraction methods. Catalytic studies reveal that these compounds are active in ring-opening polymerization of L-lactide.

Cyclopentadienyl-silsesquioxane titanium complexes: highly active catalysts for epoxidation of alkenes with aqueous hydrogen peroxide.

Titanium complexes bearing an unprecedented tridentate cyclopentadienyl-silsesquioxanate ligand provide a new class of efficient and selective catalysts for epoxidation of olefins with aqueous hydrogen peroxide under homogeneous conditions.

Lewis acid fragmentation of a lithium aryloxide cage: generation of new heterometallic aluminium-lithium species.

Heterometallic aluminium-lithium species were prepared by the fragmentation reaction of the hexametallic cage compound [Li{2,6-(MeO)(2)C(6)H(3)O}](6) (1) with alkyl aluminium derivatives. Depending on the aluminium precursor, the species formed present different nuclearities in the solid state as shown by single crystal X-ray analysis. Spectroscopic and computational studies have been performed to study the nuclearity of the synthesized compounds in solution.

Synthesis and structural characterization of novel tetranuclear organotitanoxane derivatives.

Synthesis of the novel titanoxane compounds, [(TiCl)(TiOH){(Ti)[µ-(η(5)-C(5)Me(4)SiMe(2)O-κO)](2)(µ-O)}(2)(µ-O)] (4) and [{Ti[µ-(η(5)-C(5)Me(4)SiMe(2)O-κO)](µ-O)}(4)] (5) by controlled reaction of the dinuclear titanium oxo complex [{Ti{µ-(η(5)-C(5)Me(4)SiMe(2)O-κO)}Cl](2)(µ-O)] (1) with 2 equiv of LiOH is reported. Complex 4 is innovative and remarkable. It is one of the rare known examples of tetranuclear stable terminal hydroxo titanium complexes, with an open-chained structure, which coincides with the transient metal monohydroxo proposed in the stepwise pathway employed to justify the formation of the hexanuclear complex [{Ti[µ-(η(5)-C(5)Me(4)SiMe(2)O-κO)](µ-O)}(6)] (3) from 1. (1)H DOSY experiments were used to characterize complex 4. In addition, the structures of compound 5 and of precursor 1 were determined by single-crystal X-ray diffraction studies.

Novel dinuclear dimethylamido-3,5-dimethylpyrazolato and tetranuclear dimethylamido-3,5-dimethylpyrazolato-polyoxo zirconium(IV) complexes. Synthesis and structural characterisation.

The dinuclear dimethylamido-tris(3,5-dimethylpyrazolato)-zirconium(IV) complex [Zr(3,5-Me2Pz)3(NMe2)]2 1 is prepared by treatment of [Zr(NMe2)4] with 3 equivalents of 3,5-dimethylpyrazole (3,5-Me2PzH) with elimination of dimethylamine. When [Zr(NMe2)4] reacted with 2 equivalents of 3,5-Me2PzH, the bis(dimethylamido)-bis(3,5-dimethylpyrazolato)zirconium(IV) compound [Zr(3,5-Me2Pz)2(NMe2)2]2 2 is obtained. Hydrolysis of [Zr(3,5-Me2Pz)3(NMe2)]2 in wet toluene affords the tetranuclear oxo compound [Zr4(eta2-3,5-Me2Pz)4(NMe2)2(mu3-O)2(mu2-3,5-Me2Pz)4(mu2-NMe2)2] . All synthesised compounds are characterised by NMR spectroscopic and analytical methods. Single crystal X-ray diffraction analysis has established the molecular structures of 1 and 4.

Olefin isomerisation versus hydrozirconation: a case of a stable beta-hydrogen-containing Zr-alkyl derivative.

Details of the olefin isomerisation mechanism followed by monohydride constrained-geometry zirconium complexes have been clarified using the allyldimethylsilylcyclopentadienyl zirconium hydride model compound. DFT calculations on the model systems agree with the experimental results.

Organotitanoxanes with unique structure among transition-element organometallic oxide derivatives.

The synthesis of novel titanoxane compounds, [{(TiCl)(Ti)[mu-(eta(5)-C5Me4SiMe2O-kappaO)]2(mu-O)}2(mu-O)] (4) and [{Ti[mu-(eta(5)-C5Me4SiMe2O-kappaO)](mu-O)}6] (5), by controlled hydrolysis of a dinuclear titanium/oxo complex is described. Complexes 4 and 5 show unprecedented structural features for organometallic oxide derivatives of transition elements and represent unique fully characterized examples of tetra- and hexanuclear organo-transition-metal oxide compounds with an open-chain and a monocyclic structure, respectively.