Synthesis and X-ray Structural Analysis of the Ruthenium(III) Complex Na[trans-RuCl4(DMSO) (PyrDiaz)], the Diazene Derivative of Antitumor NAMI-Pyr.

Novel tetrachloridoruthenium(III) complex Na[trans-RuCl4(DMSO)(PyrDiaz)] (3) with pyridine-tethered diazenedicarboxamide PyrDiaz ligand (PyrDiaz = N1-(4-isopropylphenyl)-N2-(pyridin-2-ylmethyl)diazene-1,2-dicarboxamide) was synthesized by direct coupling of PyrDiaz with sodium trans-bis(dimethyl sulfoxide)tetrachloridoruthenate(III) (Na-[trans-Ru(DMSO)2Cl4]). Compound 3 is the analogue of the antimetastatic Ru(III) complex NAMI-A and NAMI-Pyr. Single crystal X.

An axial chirality and disorder of positional isomers in a crystal of highly cytotoxic 3-acetyl-1,3-bis(2-chloro-4-nitrophenyl)-1E-triazene.

Biologically active 4-nitro-substituted 1,3-diaryltriazene, a chemical analogue of 1,3-bis(4'-amidinophenyl)-triazene-berenil®, belongs to the novel, chemically modified class of potent antitumor agents. Its structural characterization by X-ray analysis and 1H NMR spectroscopy is performed to determine molecular overall conformation in view of its possible interaction to DNA.

N-substituted 2-isonicotinoylhydrazinecarboxamides--new antimycobacterial active molecules.

This report presents a new modification of the isoniazid (INH) structure linked with different anilines via a carbonyl group obtained by two synthetic procedures and with N-substituted 5-(pyridine-4-yl)-1,3,4-oxadiazole-2-amines prepared by their cyclisation. All synthesised derivatives were characterised by IR, NMR, MS and elemental analyses and were evaluated in vitro for their antimycobacterial activity against Mycobacterium tuberculosis H37Rv, Mycobacterium avium 330/88, Mycobacterium kansasii 235/80 and one clinical isolated strain of M. kansasii 6509/96. 2-Isonicotinoyl-N-(4-octylphenyl)hydrazinecarboxamide displayed an in vitro efficacy comparable to that of INH for M. tuberculosis with minimum inhibitory concentrations (MICs) of 1-2 µM. Among the halogenated derivatives, the best anti-tuberculosis activity was found for 2-isonicotinoyl-N-(2,4,6-trichlorophenyl)hydrazinecarboxamide (MIC=4 µM). In silico modelling on the enoyl-acyl carrier protein reductase InhA confirmed that longer alkyl substituents are advantageous for the interactions and affinity to InhA. Most of the hydrazinecarboxamides, especially those derived from 4-alkylanilines, exhibited significant activity against INH-resistant nontuberculous mycobacteria.

Anti-mycobacterial activity of 1,3-diaryltriazenes.

The rapid generation and spread of the drug resistant tuberculosis has led to an ongoing demand for novel compounds for therapeutic use. Identification and study of compounds with the ability to inhibit Mycobacterium tuberculosis is of paramount importance. For this reason, a library of substituted 1,3-diaryltriazenes based on the acting component of the anti-trypanosomal drug, diminazene aceturate was created and evaluated for its potential as anti-tubercular agent. Several compounds were identified with sub-micro molar inhibitory concentrations against M. tuberculosis and other clinically relevant mycobacterial species such as Mycobacterium bovis, Mycobacterium avium and Mycobacterium ulcerans. Although the library of the compounds showed a considerable acute cytotoxicity, a genotoxicity could not be observed. Finally, the triazene 14 was selected with the best biological properties (IC50 = 3.26 µM, NI50 = 24.22 µM, SI = 7.44). The compound 14 showed the ability to inhibit the growth of intracellular replicating and multi-drug resistant M. tuberculosis. The results suggest the molecule to be an interesting scaffold for further study and optimization.

Biological evaluation of diazene derivatives as anti-tubercular compounds.

Despite efforts made in chemotherapeutic research in the past and present, Mycobacterium tuberculosis (M.tb), the etiological agent of tuberculosis, still causes more than a million deadly casualties each year, second only to HIV. The rapid generation and spread of drug resistant strains, a problem exacerbated by co-infection with HIV demands further efforts in the investigation of novel classes of anti-tubercular compounds. A library of eight substituted diazenecarboxamides, three carbamoyldiazenecarboxylates and four diazene-1,2-dicarboxamides was synthesized in a straightforward manner followed by a biological evaluation of the compounds. We observed minimal inhibitory concentrations below 10 µg/mL against the H37Rv lab strain of M.tb. Three compounds that showed a potency of 90% growth inhibition of M.tb at a concentration lower than 10 µg/mL were further evaluated and showed potency against other clinically relevant mycobacterial species such as Mycobacterium bovis, Mycobacterium avium and Mycobacterium ulcerans. The selected compounds were examined for acute cell toxicity on a murine macrophage like monocyte cell line J774 A.1 in which the cell viability was reduced by 50% at concentrations ranging from 7.4 µg/mL to 20.7 µg/mL. Neither of the three compounds showed signs of genotoxicity by VITOTOX or by Comet assay. The study was complemented by demonstration of the inhibition of intracellular replication of M.tb H37Rv inside J774 A.1 cells at 2 µg/mL concentration and the susceptibility of a MDR LAM-1 strain at concentrations between 5 and 1 µg/mL of the most active compound.

3-Acetyl-bis(2-chloro-4-nitrophenyl)triazene is a potent antitumor agent that induces oxidative stress and independently activates the stress-activated protein kinase/c-Jun NH2-terminal kinase pathway.

Previously, we described the synthesis and biological activity of a new class of anticancer molecules that preferentially target malignant cells and may serve as potential antitumor agents. Among several synthesized agents, we selected 3-acetyl-1,3-bis(2-chloro-4-nitrophenyl)-1-triazene (8b) as a representative of the group of 4-nitro-substituted 1,3-diaryltriazenes. The aim of this study was to further investigate the mechanism of cell response to the 8b compound. The HeLa human cervical carcinoma cell line was used as an experimental model to further investigate the mechanism of cell response to the 8b compound. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay was used to address cell survival, and western blot (immunoblotting) was used for the expression of relevant proteins after 8b drug exposure. The pretreatment of HeLa cells with salubrinal, a specific inhibitor of endoplasmic reticulum (ER) stress, confirmed the importance of ER stress in apoptosis induced by 8b. We also demonstrate that 8b triggers the activation of stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK) in a time-dependent and dose-dependent manner. Moreover, the inhibition of SAPK/JNK activity by JNK II before 8b treatment increased the survival rate of HeLa cells relative to survival in the presence of 8b alone, indicating the importance of this kinase in cell death. The simultaneous inhibition of ER stress induction and SAPK/JNK activation increased the survival of HeLa cells upon 8b treatment more than inhibition of both pathways independently, suggesting the separate triggering of both signaling pathways. Our data indicate that cytotoxic activity of the novel compound 8b is based on its ability to induce ER stress and SAPK/JNK signaling pathways independently, driving cells to cell death.

Synthesis and biological activity of new diazenedicarboxamides as potential anticancer agents.

To increase the effectiveness of cancer treatment, more effective anti-cancer drugs, as well as the new improved strategies of cancer treatment, are urgently needed. Our previous results have shown that various diazenes are cytotoxic to different tumor cells and can even revert the resistance to cisplatin and vincristine. We also demonstrated that unsymmetrical diazenedicarboxamides 1 and 2 exhibited promising cytotoxicity. The aim of the present study was to synthesize new diazenedicarboxamides with acceptable solubility and good cytotoxicity. Here we report the synthesis and biological evaluation of new N,N'-disubstituted diazenedicarboxamides. We found that a modification of either 1 or 2 led to the more active compounds. The most effective among them was diazenedicarboxamide 11, which can be considered as a new potential anticancer agent for the tumors of different origin, as well as for the drug resistant tumors.

2,3-Diarylpropenoic acids as selective non-steroidal inhibitors of type-5 17ß-hydroxysteroid dehydrogenase (AKR1C3).

The aldo-keto reductase AKR1C3 is an important target for the development of new drugs. Selective inhibitors of this enzyme are needed because they should not inhibit other, structurally closely related AKR1C isoforms. A comprehensive series of 2,3-diarylpropenoic acids was synthesized and evaluated for the inhibition of AKR1C1-AKR1C3. We found that the 4-methylsulfonylphenyl substituent at position 2 of these acids is required to exhibit the selective inhibition of AKR1C3. The best results were obtained for the compounds that fulfill the above requirement and possess a 4-bromophenyl, 4-methylthiophenyl, 4-methylphenyl or 4-ethylphenyl substituent at position 3 of the substituted propenoic acids (i.e., acids 28, 29, 37, and 39, respectively). These compounds represent an important step toward the development of drug candidates for a treatment of the hormone-dependent and hormone-independent forms of prostate and breast cancers.

A way to avoid using precious metals: the application of high-surface activated carbon for the synthesis of isoindoles via the Diels-Alder reaction of 2H-pyran-2-ones.

The application of activated carbon (Darco KB) for the acceleration and direction of the transformation of various 2H-pyran-2-ones with N-substituted maleimides toward isoindole derivatives through the reaction sequence cycloaddition/elimination/dehydrogenation is described. In this reaction, the catalyst mainly influences the dehydrogenation step, which is essential to avoid the formation of bicyclo[2.2.2]octenes as the other possible products. We found that the combination of Darco KB, as the metal-free catalyst, and decalin, as the solvent in a closed vessel, represents the most successful conditions. A comparison of the effect of various dehydrogenation catalysts and reaction conditions is also presented. In addition, we have proven that the aromatization occurs via a hydrogen transfer from the cyclohexadiene intermediate to the maleimide derivative (therefore producing succinimides). This transfer is facilitated by the active surface of the heterogeneous carbon-based catalyst.

Ring-opening reactions of 1,4-diazabicyclo[2.2.2]octane (DABCO) derived quaternary ammonium salts with phenols and related nucleophiles.

1,4-Diazabicyclo[2.2.2]octane (DABCO) has been evaluated as a starting material for the synthesis of 1-alkyl-4-(2-phenoxyethyl)piperazines and related derivatives. We found that 1-alkyl-1,4-diazabicyclo[2.2.2]octan-1-ium salts, resulting from the alkylation of DABCO, efficiently react with a variety of nucleophiles in polyethyleneglycol (PEG) or diglyme at high temperatures to give piperazine products resulting from the nucleophilic ring-opening reaction. The benzylation side reaction was found to be relevant with softer nucleophiles when using 1-benzyl-1,4-diazabicyclo[2.2.2]octan-1-ium salts, while other types of alkylations were not observed. One-pot methodologies allow for the synthesis of piperazines directly from primary alcohols, alkyl halides or sulfonates, using phenols, or other nucleophile sources, and DABCO.

New series of isoniazid hydrazones linked with electron-withdrawing substituents.

A series of new isoniazid hydrazones was synthesized by two procedures. In the first isoniazid was activated with diethoxymethyl acetate and condensed with the appropriate anilines. Alternatively, substituted anilines were activated by diethoxymethyl acetate and subsequently condensed with isoniazid. NMR study confirmed that both synthetic approaches gave the same tautomer. All compounds were screened for in vitro antimycobacterial activity. Most of them exhibited the same activity against Mycobacterium tuberculosis (MIC 1 µmol L(-1)) as isoniazid (INH), better activity against Mycobacterium kansasii 325/80 (MIC 0.125-0.250 µmol L(-1)), high value of selectivity index (SI) and IC(50) between 0.0218 and 0.326 mmol L(-1). Compound 2o with the best SI was used as a model compound for the stability test and was found to be stable at neutral pH, but under acidic conditions it slowly hydrolysed.

New fluorine-containing hydrazones active against MDR-tuberculosis.

Several new fluorine-containing hydrazones were synthesized and screened for their in vitro antimycobacterial activity. Nine of these derivatives have shown a remarkable activity against MDR-TB strain with MIC 0.5 µg/mL and high value of selectivity index (SI). Compound 3h with the highest SI (1268.58) was used for stability evaluation with putative metabolites (ciprofloxacin and formylciprofloxacin) detection. Compound 3h was stable at pH 7.4 of aqueous buffer and rat plasma, in acidic buffers (at pH 3 and 5) slow decomposition was observed. Interestingly, no formylciprofloxacin was detected in the solution, and only slightly increased concentration of ciprofloxacin was observed instead. Trifluoromethyl hydrazones 3f and 3g exhibited the best activity also against two strains of Mycobacterium kansasii (MIC 1-4 µmol/L). All evaluated compounds were found to be non-cytotoxic.

Synthesis and biological evaluation of 4-nitro-substituted 1,3-diaryltriazenes as a novel class of potent antitumor agents.

We describe the synthesis and biological activity of a new class of 1,3-diaryltriazenes, namely 4-nitro-substituted 1,3-diaryltriazenes. Structure-activity relationship analysis reveals that 1,3-diaryltriazenes can be modified from inactive to highly cytotoxic compounds by the introduction of two nitro groups at the para positions of benzene rings and two additional electron-withdrawing groups (bromo, chloro, trifluoromethyl or fluoro substituents) at their ortho position. In order to increase the solubility of the modified compounds, we introduced various acyl groups to their triazene nitrogen. The results of LC-MS/MS analysis showed that N-acyltriazenes can be considered as prodrugs of non-acylated triazenes. Selected 3-acetyl-1,3-bis(2-chloro-4-nitrophenyl)-1-triazene (8b) is highly cytotoxic against different tumor cell lines, including cisplatin-resistant laryngeal carcinoma cells. Notably, its antiproliferative activity is significantly higher against tumor cells than against normal cells. DNA binding analysis suggests that neither 8b nor its non-acylated derivative 8a bind into the minor groove of DNA. Instead, 8b induces reactive oxygen species that could provoke endoplasmic reticulum (ER(a)) stress finally leading to apoptosis. Our data suggest that 4-nitro-substituted 1,3-diaryltriazenes are a new class of anticancer molecules which preferentially target malignant cells and may serve as potential antitumor agents.

Pyrazolone-fused combretastatins and their precursors: synthesis, cytotoxicity, antitubulin activity and molecular modeling studies.

A series of pyrazolone-fused combretastatins and precursors were synthesized and their cytotoxicity as well as antitubulin potential was evaluated. The hydrazide 9f and the pyrazolone-fused combretastatins 12a, 12b and 12c were highly cytotoxic against various tumor cell lines including cisplatin resistant cells. The same compounds were also the best inhibitors of tubulin polymerization. Molecular modeling results showed that they bind the colchicine binding site at the tubulin heterodimer. The hydrazide 9f arrested HeLa cells in the G2/M phase of the cell cycle and strongly affected cell shape and microtubule network.

Synthesis of aryl alkyl ethers by alkylation of phenols with quaternary ammonium salts.

Phenolic compounds can be efficiently O-methylated with tetramethylammonium chloride in diglyme or polyethyleneglycol (PEG) at temperatures of 150-160 °C and in the presence of either K2CO3 or NaOH. When applying benzyltrimethylammonium chloride as a reagent, the benzylation and methylation of phenols occurs, with the benzylation product always predominating. With allyl-substituted phenols as substrates and using NaOH as a base it was possible to achieve both the alkylation and the double-bond isomerization of the allyl group to obtain (E/Z)-propenyl-substituted methyl and benzyl aryl ethers in a single preparative step.

Design and synthesis of new hydroxyethylamines as inhibitors of D-alanyl-D-lactate ligase (VanA) and D-alanyl-D-alanine ligase (DdlB).

The Van enzymes are ATP-dependant ligases responsible for resistance to vancomycin in Staphylococcus aureus and Enteroccoccus species. The de novo molecular design programme SPROUT was used in conjunction with the X-ray crystal structure of Enterococcus faeciumd-alanyl-d-lactate ligase (VanA) to design new putative inhibitors based on a hydroxyethylamine template. The two best ranked structures were selected and efficient syntheses developed. The inhibitory activities of these molecules were determined on E. faecium VanA, and due to structural similarity and a common reaction mechanism, also on d-Ala-d-Ala ligase (DdlB) from Escherichia coli. The phosphate group attached to the hydroxyl moiety of the hydroxyethylamine isostere within these systems is essential for their inhibitory activity against both VanA and DdlB.

Synthesis and self-assembly of thio derivatives of calix[4]arene on noble metal surfaces.

Self-assembled monolayers (SAMs) provide a simple route to functionalize electrode surfaces with organic molecules. Herein we use cavity-containing derivatives of calix[4]arenes in SAMs. Bound to noble metal surface, the assembled molecules are candidates to serve as molecular sieves for H 2 molecules and H (+) ions, which could have relevance for fuel cell applications. Tetra- O-alkylated calix[4]arenes with thiolacetate and thiolamide wide-rim anchoring groups in cone and partial-cone conformations were designed, synthesized and self-assembled onto Au, Pt, and Pd surfaces. The resulting SAMs were systematically examined. Single crystal X-ray diffraction of 5,11,17,23-tetrakis(thioacetyl)-25,26,27,28-tetra- i-propoxycalix[4]arene confirmed the cone conformation and revealed the cavity dimensions of the SAMs that were formed by immersing noble metal substrates (Au, Pt and Pd deposited on Si-wafers) in solutions of calix[4]arenes. Surface characterization techniques including ellipsometry, cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) were used, indicating that the metal surface is terminated with a monomolecular layer. Experimental thicknesses obtained from the ellipsometry are consistent with the calculated values. CV results showed 50 to 80% physical passivation against the Fe(CN) 6 (3-/4-) couple, implying an overall relatively low concentration of defects and pinholes in the films. The binding energies of the S2p core level in the XPS were consistent with the literature values and revealed that up to 3.2 out of four anchoring groups were bonded to the noble metal surface.

Diazenedicarboxamides as inhibitors of D-alanine-D-alanine ligase (Ddl).

D-Alanine-D-alanine ligase (Ddl) catalyzes the biosynthesis of an essential bacterial peptidoglycan precursor D-alanyl-D-alanine and it represents an important target for development of new antibacterial drugs. A series of semicarbazides, aminocarbonyldiazenecarboxylates, diazenedicarboxamides, and hydrazinedicarboxamides was synthesized and screened for inhibition of DdlB from Escherichia coli. Compounds with good inhibitory activity were identified, enabling us to deduce initial structure-activity relationships. Thirteen diazenedicarboxamides were better inhibitors than D-cycloserine and some of them also possess antibacterial activity, which makes them a promising starting point for further development.

A new modification of anti-tubercular active molecules.

The connection of two active molecules across an easily released bridge as a new type of potentially active molecule has been studied. The synthesis is based on derivatives that originate from isonicotinoyl hydrazide, pyrazinamide, p-aminosalicylic acid (PAS), ethambutol, and ciprofloxacin. The lipophilicity, hydrolysis (stability of the compounds), and antituberculotic activity as well as the structure-lipophilicity and structure-activity relationships are discussed.