Repositioning of leishmanicidal [1,2,3]Triazolo[1,5-a]pyridinium salts for Chagas disease treatment: Trypanosoma cruzi cell death involving mitochondrial membrane depolarisation and Fe-SOD inhibition

Trypanosomatidae is a family of unicellular parasites belonging to the phylum Euglenozoa, which are causative agents in high impact human diseases such as Leishmaniasis, Chagas disease and African sleeping sickness. The impact on human health and local economies, together with a lack of satisfactory chemotherapeutic treatments and effective vaccines, justifies stringent research efforts to search for new disease therapies. Here, we present in vitro trypanocidal activity data and mode of action data, repositioning leishmanicidal [1,2,3]Triazolo[1,5-a]pyridinium salts against Trypanosoma cruzi, the aetiological agent of Chagas disease. This disease is one of the most neglected tropical diseases and is a major public health issue in Central and South America. The disease affects approximately 6-7 million people and is widespread due to increased migratory movements. We screened a suite of leishmanicidal [1,2,3]Triazolo[1,5-a]pyridinium salt compounds, of which compounds 13, 20 and 21 were identified as trypanocidal drugs. These compounds caused cell death in a mitochondrion-dependent manner through a bioenergetic collapse. Moreover, compounds 13 and 20 showed a remarkable inhibition of iron superoxide dismutase activity of T. cruzi, a key enzyme in the protection from the damage produced by oxidative stress.

Combining Amines and 3-(2-Pyridyl)-[1,2,3]Triazolo[1,5-a]pyridine: An Easy Access to New Functional Polynitrogenated Ligands

Triazolopyridine-pyridine amine ligands are easily obtained by means of either thermal- or copper(II)-mediated reactions. Starting from a readily accessible iodo derivative of triazolopyridine-pyridine and different amines, this new family of compounds combines aromatic and aliphatic nitrogen atoms with promising coordinating properties. Furthermore, chemical derivatization of a new triazolopyridine-pyridine diamine compound, N1-[6-([1,2,3]triazolo[1,5-a]pyridin-3-yl)pyridin-2-yl]ethan-1,2-diamine, allows the preparation of several remote-pyridine-containing ligands.

Empirical modeling of material composition and size in MOFs prepared with ligand mixtures

Mixed MOF-5/IRMOF-3 case study: from micrometers to millimeters.

Straight Access to Indoles from Anilines and Ethylene Glycol by Heterogeneous Acceptorless Dehydrogenative Condensation

The development of original strategies for the preparation of indole derivatives is a major goal in drug design. Herein, we report the first straight access to indoles from anilines and ethylene glycol by heterogeneous catalysis, based on an acceptorless dehydrogenative condensation, under noninert conditions. In order to achieve high selectivity, a combination of Pt/Al₂O₃ and ZnO have been found to slowly dehydrogenate ethylene glycol generating, after condensation with the amine and tautomeric equilibrium, the corresponding pyrrole-ring unsubstituted indoles.

Synthesis of new fluorescent amino acids with a triazolopyridine core: diacid sensors

A new family of amino acid containing pyridine–triazolopyridine cores has been prepared by means of a copper catalysed reaction.

Synthesis of Novel Polyazinyl-Substituted Triazolopyridines from [1,2,3]Triazolo[1,5-a]pyridines

A series of 7-azinyl-substituted triazolopyridines and 3-(6-azi­nyl-substituted 2-pyridyl)triazolopyridines were synthesized by addition of the corresponding 3-substituted 7-lithiotriazolopyridine to pyrimidine, pyrazine, pyridazine, and 1,3,5-triazine respectively, followed by hydrolysis and oxidation.

Bicyclo[2.2.2]octane-1,4-dicarboxylic acid: towards transparent metal–organic frameworks

The preparation of transparent porous materials can offer a different access towards the study of molecules under solid confined space.

Synthesis and in vitro leishmanicidal activity of novel [1,2,3]triazolo[1,5-a]pyridine salts

Leishmaniasis remains a significant worldwide problem; it is of great interest to develop new drugs to fight this disease.

Synthesis of new terpyridine-like ligands based on triazolopyridines and benzotriazoles

Herein, terpyridine triazole-based analogs bearing benzotriazoles or/and triazolopyridines are prepared via copper catalysis, where the arrangement of the nitrogen atoms is proven to be crucial to the spectroscopic properties of these ligands.

Spectroscopic studies of the interaction of 3-(2-thienyl)-[1,2,3]triazolo[1,5-a]pyridine with 2,6-dimethyl-β-cyclodextrin and ctDNA

The studied effect of the inclusion complex on the ctDNA interaction indicates that the TTP-DMβCD complex binds similarly to ctDNA compared to free TTP.

New structural motifs in Mn cluster chemistry from the ketone/gem-diol and bis(gem-diol) forms of 2,6-di-(2-pyridylcarbonyl)pyridine: {MnII4MnIII2} and {MnII4MnIII6} complexes

The ketone/gem-diol (L1H₂) and bis(gem-diol) (L2H₄) forms of the ligand 2,6-di-(2-pyridylcarbonyl)pyridine in Mn cluster chemistry have afforded the new complexes [MnII4MnIII2(N₃)₆Cl₄(L1)₂(DMF)₄] and [MnII4MnIII6O₂(N₃)₁₂(L1)₂(L2H)₂(DMF)₆].

Triazolopyridopyrimidines: an emerging family of effective DNA photocleavers. DNA binding. Antileishmanial activity

Triazolopyridopyrimidines 3-phenyl-6,8-di(2-pyridyl)-[1,2,3]triazolo[5',1':6,1]pyrido[2,3-d]pyrimidine (1a), 6,8-di(pyridin-2-yl)-[1,2,3]triazolo[1',5':1,6]pyrido[2,3-d]pyrimidine (1b) and 3-methyl-6,8-di(2-pyridyl)-[1,2,3]triazolo[5',1':6,1]pyrido[2,3-d]pyrimidine (1c) were prepared and their electrochemical and luminescence properties were studied in depth. The DNA binding ability of this series of compounds has been investigated by means of UV-vis absorption and fluorescence titrations, steady-state emission quenching with ferrocyanide as well as viscosity measurements. Results have shown that triazolopyridopyrimidine 1a interacts strongly at DNA grooves. This compound also displays preferential binding to GC-rich sequences and the ability to photooxidize guanine. Moreover, these studies have revealed the key role of the phenyl substituent at the triazole ring in the binding affinity of 1a-c. Compounds 1b and 1c did not show appreciable propensity for DNA binding, however these triazolopyridopyrimidines demonstrated to present photoinduced DNA cleavage activity, 1b being more active than 1c. DNA photocleavage mediated by these compounds takes place mainly through single strand scission events and, in a minor extent, through double strand cuts. Mechanistic investigations using radical scavengers showed that both 1b and 1c generate reactive oxygen species (singlet oxygen, superoxide and hydroxyl radicals) upon irradiation. Both type I and type II mechanisms are involved in the photocleavage process. Furthermore, compounds 1a-c were tested for their antiprotozoal activity against four different Leishmania spp. (L. infantum, L. braziliensis, L. guyanensis and L. amazonensis). Triazolopyridopyrimidines 1a and 1c resulted to be more active and selective than the reference drug (miltefosine) in vitro against L. infantum amastigotes. Compound 1a exhibited high leishmanicidal activity against L. infantum spleen forms in the in vivo test.

Unusual phosphine oxidation: new triazolopyridyl-quinolyl phosphine oxide fluorescent dyes

3-(2-Pyridyl)-[1,2,3]triazolo[1,5-a]quinolylphosphines suffer an unusual phosphine oxidation due to their special geometry that allows a σ-donation of the nitrogen (N1) lone pair to phosphorus.

ESR, electrochemical and cyclodextrin-inclusion studies of triazolopyridyl pyridyl ketones and dipyridyl ketones derivatives

The electron spin resonance (ESR) spectra of free radicals obtained by electrolytic reduction of triazolopyridyl pyridyl ketones and dipyridyl ketones derivatives were measured in dimethylsulfoxide (DMSO). The hyperfine patterns indicate that the spin density delocalization is dependent of the rings presented in the molecule. The electrochemistry of these compounds was characterized using cyclic voltammetry, in DMSO as solvent. When one carbonyl is present in the molecule one step in the reduction mechanism was observed while two carbonyl are present two steps were detected. The first wave was assigned to the generation of the correspondent free radical species, and the second wave was assigned to the dianion derivatives. The phase-solubility measurements indicated an interaction between molecules selected and cyclodextrins in water. These inclusion complexes are 1:1 with betaCD, and HP-betaCD. The values of Ks showed a different kind of complexes depending on which rings are included. AM1 and DFT calculations were performed to obtain the optimized geometries, theoretical hyperfine constants, and spin distributions, respectively. The theoretical results are in complete agreement with the experimental ones.

An “S”-shaped pentanuclear CuII cluster derived from the metal-assisted hydrolysis of pyCOpyCOpy: structural, magnetic and spectroscopic studies

Reaction of [Cu2(O2CMe)4(H2O)2] with 2,6-di-(2-pyridylcarbonyl)-pyridine (pyCOpyCOpy or dpcp) in MeCN-H2O 10:1, led to the pentanuclear copper(II) complex [Cu5(O2CMe)6{pyC(O)(OH)pyC(O)(OH)py}2] () which crystallizes in the triclinic P1 space group. The copper(II) atoms are arranged in an "S"-shaped configuration, and are bridged by the doubly deprotonated bis(gem-diol) form of the ligand, pyC(O)(OH)pyC(O)(OH)py2-. Magnetic susceptibility data indicate the interplay of both ferro- and antiferromagnetic intramolecular interactions stabilizing an S=3/2 ground state. Fitting of the data according to a next-nearest-neighbour model {H=-[J1(S1S2+S1'S2')+J2(S2S3+S3'S2')+J3(S1S3+S3'S1')+J4(S2S2')]} yields exchange coupling constants J1=+39.7 cm(-1), J2=-15.9 cm(-1), J3=-8.3 cm(-1) and J4=+4.3 cm(-1), leading to an S=3/2 ground state. X-Band EPR spectroscopy indicates a zero-field splitting of the ground state with |D3/2|=0.38 cm(-1).

Properties of a Triazolopyridine System as a Molecular Chemosensor for Metal Ions, Anions, and Amino Acids

The characteristics as a chemosensor of the compound 3-methyl-6,8-di(2-pyridyl)-[1,2,3]triazolo[5',1':6,1]pyrido[2,3-]pyrimidine (1) have been analyzed. Interaction with Cu(2+) produces a quenching of the fluorescence, while interaction with Zn(2+) leads to a quenching of the fluorescence followed by a bathochromic shift. The crystal structure of the Zn(1)(H(2)O)(3)(ClO(4))(2) x H(2)O complex shows the coordination of Zn(2+) through the terpyridine moiety. The octahedral site is completed by three water molecules. Interactions of the Zn(2+) complex with the anions sulfate, nitrate, nitrite, and dihydrogenphosphate in ethanol produce hypsochromic shifts and restoration of the fluorescence whose magnitude depends on the anion involved. The maximum interaction is observed for H(2)PO(4)(-). Interactions of the Zn(2+) complex with the amino acids l-aspartate and l-glutamate have also been explored showing a higher interaction with l-aspartate.

Deprotonation of benzoxazole and oxazole using lithium magnesates

The first deprotonations of oxazole and benzoxazole using lithium magnesates are described. The reactions occurred in tetrahydrofuran at room temperature using 1/3 equiv of lithium tributylmagnesate. As 2-lithiooxazole and 2-lithiobenzoxazole, lithium tri(2-oxazolyl)magnesate and lithium tri(2-benzoxazolyl)magnesate very rapidly and completely isomerized to the more stable 2-(isocyano)enolate and 2-(isocyano)phenolate type structures, respectively, a result shown by NMR analysis. The isolation of 2-substituted oxazoles and benzoxazoles in medium to good yields after electrophilic trapping was interpreted in two ways: (1) the equilibration between the open and closed structures is faster than the trapping of the open isomers, and the closed isomers are more reactive than the open ones, or (2) the open isomers react with electrophiles in a intramolecular Passerini type reaction. The nonreactivity of the 2-(isocyano)enolate type structure toward anisaldehyde in the absence of lithium bromide makes the intramolecular Passerini type reaction more plausible.

ESR and electrochemical studies of 2-acylpyridines and 6,6'-diacyl-2,2'-bipyridines

The ESR spectra of radicals obtained by electrolytic reduction of 2-acylpyridines and 6,6'-diacyl-2,2'-bipyridines were measured in dimethylsulfoxide (DMSO) and analyzed by quantum chemical calculations. The electrochemistry of these compounds was characterized using cyclic voltammetry, in DMSO solvent. The results showed a two step reduction mechanism, first wave was assigned to the generation of the correspondent free radical species, and the second wave was assigned to the dianion derivatives. AM1 and DFT calculations were performed to obtain the optimized geometries, theoretical hyperfine constants, and spin distributions, respectively. The theoretical results are in complete agreement with the experimental ones.