Pyridinium Residues Research Articles

Dynamic Approach to Synthetic Lectin for Glucose with Boosted Binding Affinity through C-H Hydrogen Bonds.

A biomimetic receptor for glucose has been developed with high affinity and selectivity. The receptor was efficiently synthesized in three steps through dynamic imine chemistry followed by imine-to-amide oxidation. The receptor features two parallel durene panels, forming a hydrophobic pocket for [CH⋅⋅⋅π] interactions, and two pyridinium residues directing four amide bonds towards the pocket. These pyridinium residues not only improve solubility but also provide polarized C-H bonds for hydrogen bonding. Experimental data and DFT calculations show that these polarized C-H bonds significantly enhance substrate binding. These findings demonstrate the power of dynamic covalent chemistry for creating molecular receptors and using polarized C-H bonds for boosted carbohydrate recognition in water, providing a foundation for developing glucose-responsive materials and sensors.

Uncommon reaction of 2-bromomethyl-1,3-thiaselenole with pyridine and its derivatives

Regioselective reaction of 2-bromomethyl-1,3-thiaselenole with pyridine and its derivatives is followed by rearrangement with ring expansion and the formation of a bond between a nitrogen atom and a carbon in the position 2. A set of derivatives of 2,3-dihydro-1,4-thiaselenine was obtained, substituted in the position 2 by a pyridinium residue functionalized by pharmacophoric groups.

Quadruple stacking of macrocyclic viologen radical-cations

The solid state structures of the di-cationic (1a) and radical mono-cationic (1b) redox forms of a 4,4′-bipyridinium (viologen) containing macrocycle have been established by single crystal X-ray analysis. Formation of the radical cation has a dramatic effect on the molecular structure of the macrocycle. Addition of an electron to 1a both decreases the diameter of the ring cavity (from 8.5 to 7.8 Å) and drastically flattens the torsion angle between the two pyridinium residues in the viologen, reducing it from 48° to either 3° or 9° (two independent molecules). Moreover, a close association of these near-planar radical cation units drives the formation of a tetrameric supramolecular structure in the solid state.

Cooperative Al(Salen)-Pyridinium Catalysts for the Asymmetric Synthesis of trans-Configured β-Lactones by [2+2]-Cyclocondensation of Acylbromides and Aldehydes: Investigation of Pyridinium Substituent Effects

The trans-selective catalytic asymmetric formation of β-lactones constitutes an attractive surrogate for anti-aldol additions. Recently, we have reported the first catalyst which is capable of forming trans-β-lactones with high enantioselectivity from aliphatic (and aromatic) aldehyde substrates by cyclocondensation with acyl bromides. In that previous study the concepts of Lewis acid and organic aprotic ion pair catalysis were combined in a salen-type catalyst molecule. Since a pyridinium residue on the salen periphery is essential for high trans- and enantioselectivity, we were interested in the question of whether substituents on the pyridinium rings could be used to further improve the catalyst efficiency, as they might have a significant impact on the effective charges within the heterocycles. In the present study we have thus compared a small library of aluminum salen/bispyridinium catalysts mainly differing in the substituents on the pyridinium residues. As one result of these studies a new catalyst was identified which offers slightly superior stereoselectivity as compared to the previously reported best catalyst. NBO calculations have revealed that the higher stereoselectivity can arguably not be explained by the variation of the effective charge.

Action of Reactive Oxygen Species in the Antifungal Mechanism of Gemini-pyridinium Salts Against Yeast

We previously found that the gemini quaternary salt (gemini-QUAT) containing two pyridinium residues per molecule, 3,3'- (2,7-dioxaoctane) bis (1-decylpyridinium bromide) (3DOBP-4,10) , exerted fungicidal activity against Saccharomyces cerevisiae and caused respiration inhibition and the cytoplasmic leakage of ATP, magnesium, and potassium ions. Here, we investigated how the gemini-QUAT, 3DOBP-4,10, exerts more powerful antimicrobial activity than the mono-QUAT N-cetylpyridinium chloride (CPC) and examined the association between reactive oxygen species (ROS) and the antimicrobial mechanism. Antifungal assays showed that the activity of 3DOBP-4,10 against two yeasts, S. cerevisiae and Candida albicans, was significantly elevated under aerobic conditions, and largely reduced under anaerobic conditions (nitrogen atmosphere) . Adding radical scavengers such as superoxide dismutase, catalase and potassium iodide (KI) also decreased the fungicidal activity of 3DOBP-4,10 but negligibly affected that of CPC. We measured survival under static conditions and found that the rapid fungicidal profile of 3DOBP-4,10 was lost, whereas that of CPC was slightly affected in the presence of KI. Our results suggest that 3DOBP-4,10 exerts powerful antimicrobial activity by penetrating the cell wall and membrane, which then allows oxygen to enter the cells, where it participates in the generation of intracellular ROS. The activity could thus be attributable to a synergic antimicrobial combination of the disruption of organelle membranes by the QUAT and oxidative stress imposed by ROS.

The Mode of the Antifungal Activity of Gemini-Pyridinium Salt against Yeast

The gemini quaternary salt (gemini-QUAT) containing two pyridinium residues per molecule, 3,3'-(2,7-dioxaoctane) bis (1-decylpyridinium bromide) (3DOBP-4,10), exerted fungicidal activity against Saccharomyces cerevisiae accompanied by respiration inhibition and the cytoplasmic material leakage of ATP, magnesium, and potassium ions. We previously found that gemini-QUAT exerted bacterioclastic action against Escherichia coli by causing the rapid and abundant leakage of turbid materials from the cells. In addition, the first stage of the bacterioclastic action was the leakage of magnesium ions, outer membrane protein E, ATP, and lipopolysaccharides. Here, we investigated how the gemini-QUAT 3DOBP-4,10 exerts fungicidal action against S. cerevislae. The results showed that that > or = 0.4 microM 3DOBP-4,10 stopped respiration and that > or = 3.0, 1.0 and 1.0 microM caused the leakage of cytoplasmic components ATP, magnesium and potassium ions, respectively. Scanning and transmission electron micrographs showed a preserved cell wall structure, whereas intracellular organelles were destroyed in cells incubated with 3DOBP-4,10. We postulated that 3DOBP-4,10 exerts its fungicidal action against S. cerevisiae not through cell wall destruction and protein leakage, but rather by penetrating the cell wall and disrupting the membranes of organelles.

2 + 2]-Photocycloaddition reaction of self-assembled crown-containing 2-styrylpyridinium perchlorate in a solid state

The dimer assembly of crown ether styrylpyridinium perchlorates (CSP) in solid state and MeCN solution were studied. The obtained data in solid state allowed us to conclude that molecules spontaneously form dimeric complexes. The dimeric complex is stable due to dipole interaction between crown ether donor substitutor of one molecule and the acceptor pyridinium residue of the other one. Irradiation of the dimer complex leads to regio- and stereoselective [2 + 2]-cycloaddition, giving only one cyclobutane isomer. The formation of dimers in solution has not been found. The irradiation of MeCN solution of CSP molecules resulted in the reversible E– Z isomerization.

Antibacterial Activity and Characteristics of Modified Ferrite Powder Coated with a Gemini Pyridinium Salt Molecule

This report describes the synthesis of an antibacterial material consisting of a gemini quaternary ammonium salt (gemini-QUAT) immobilized on ferrite powder, and its antibacterial activity. A gemini-QUAT containing two pyridinium residues per molecule, 4,4'-[1,3-(2,2-dihydroxylmethyl-1,3-dithiapropane)]bis (1-octylpyridinium bromide), was immobilized on ferrite powder by a reaction between the hydroxyl group of the QUAT and trimethoxysilane. Immobilization of the gemini-QUAT on ferrite (F-gemini-QUAT) was confirmed when the dye, bromophenol blue, was released from F-gemini-QUAT-dye after contact between ferrite and the dye. Elemental analysis of the QUAT-ferrite determined the molar amount of QUAT on the ferrite. The antibacterial effect of the ferrite was investigated using a batch treatment system, and this effect was compared with that of another QUAT-ferrite (F-mono-QUAT) binding a mono-QUAT, which possesses one pyridinium residue, prepared by the same immobilization method as F-gemini-QUAT. Results indicated the F-gemini QUAT possessed a higher bactericidal potency and broader antibacterial spectrum compared to F-mono-QUAT. In addition, this study suggested that gemini-QUATs possessed high bactericidal potency without being influenced by immobilization to materials, and the antibacterial activity and characteristics of F-gemini-QUAT could be attributed to the unique structure of the immobilized gemini-QUAT.

“Conjugate” Substitution of Hydrogen in the Methyl Group of Pentabromotoluene in the Presence of Strong Bases

The reactions of pentabromotoluene with i-PrONa or t-BuONa in pyridine give N-(pentabromobenzyl)pyridinium bromide and a mixture of isomeric tetrabromotoluenes. In the presence of bromine or carbon tetrabromide, the reductive debromination is blocked, and the reactions involve exclusively substitution of hydrogen in the methyl group of pentabromotoluene by the pyridinium residue.

Studies on the Spectral-Luminescent Properties of the Novel Homodimer Styryl Dyes in Complexes with DNA

Series of homodimer styryls containing on (p-dimethylaminostyryl) pyridinium residues that are connected with aliphatic linkage group was synthesized. Spectral luminescent properties of obtained dyes in free state and in nucleic acids presence were studied. It was shown that DNA binding affinity of the novel homodimers exceeds that of parent monomer (p-dimethylaminostyryl)pyridine iodide. For homodimers with the linkage 4-10 carbon atoms preference in binding to DNA than to RNA was observed. It could be concluded that parent monomer has different mechanisms of binding to nucleic acids than corresponding homodimer dye.

Fluorescent homodimer styrylcyanines: synthesis and spectral-luminescent studies in nucleic acids and protein complexes

A series of homodimer styrylcyanine dyes based on ( p-dimethylaminostyryl)pyridinium, ( p-dimethylaminostyryl)benzoxazolium, ( p-dimethylaminostyryl)benzothiazolium, ( p-dimethylaminostyryl)-1,3,3-trimethyl-3 H-indolium residues were synthesized. Spectral-luminescent properties of the obtained homodimers in free state and in the presence of nucleic acids and BSA were studied. Homodimer styrylcyanines with the length of linkage group of 2 or more carbon atoms demonstrated a DNA-binding preference. Significant long-wave shifts of fluorescence and emission maxima of dyes with short linkage group could be explained by the interaction between chromophores due to the short distance between them, as it is the case for molecular aggregates. Homodimer dyes based on the ( p-dimethylaminostyryl)pyridinium residue having linkage group of 5 or more carbon atoms interact with dsDNA with significant emission increase and could be used as DNA specific fluorescent probes.

Equilibrium Geometry of Symmetrical Polymethine Dyes in the Solitonic Excited State

The optimized geometry in the excited state of the ions of polymethine dyes R±—(CH=CH) n —CH=R with the pyridinium residue and its carbo- and heteroanalogs in the excited state was calculated by quantum-chemical methods in the AM1 approximation. It was found that in addition to the symmetrical solution of the Hamiltonian there is an unsymmetrical soliton state. Significant alternation of the CC bond lengths at one end of the chain in the solitonic state explains the marked decrease in the quantum yields of fluorescence in the long molecules as a result of the decreased barriers of the conformational transformations.

Lysyl oxidase expression and collagen cross-linking during chronic adriamycin nephropathy.

Collagen cross-linking induced by lysyl oxidase has been implicated in liver and lung fibrosis. To define the role of this process in kidney fibrosis, we investigated the renal expression of lysyl oxidase and the content in collagen cross-links at various stages of chronic Adriamycin nephropathy in Sprague-Dawley rats. Lysyl oxidase expression was determined by RT-PCR; collagen pyridinium residues, indicating lysyl oxidase induced cross-links, were evaluated by HPLC. These parameters followed a synergic albeit asynchronous outcome: (a) lysyl oxidase mRNA levels in total kidney, glomeruli and medulla from Adriamycin-treated rats increased up to 3 times compared to controls between week 8 and 12, then returning within the normal range; (b) the pyridinium residue content did not show any significant difference between Adriamycin-treated and control rats, until diffuse interstitial fibrosis developed (16 weeks), showing at this time a 2- to 3-fold increment. Lysyl oxidase was expressed by several renal cell lines and in tubular-epithelial cells it was up-regulated in vitro by TGF beta-1, a recognized fibrogenetic factor in Adriamycin nephropathy. Our observations demonstrated that an increased expression of lysyl oxidase in the kidney precedes the development of diffuse fibrotic lesions and that, at this stage, collagenic structures contain highly cross-linked components, the final product of lysyl oxidase activity. The evidence of lysyl oxidase up-regulation in tubular epithelial cells by the same factor implicated in Adriamycin toxicity in the kidney suggests a common pathogenetic mechanism. Collagen cross-link formation by lysyl oxidase may be implicated in the pathogenesis of irreversible, fibrotic renal lesions.

Pyrylocyanines. 34.* pyrylocarbocyanines of asymmetrical structure with bridge groups in the chromophore

Asymmetrical carbocyanines with bridge groups in the chromophore, containing pyrylium, benzothiazolium, and pyridinium residues, were produced. The electronic and steric influence of the bridge groups on the spectral properties of the dyes was analyzed. The structure of the compounds obtained was confirmed by the data of electron spectroscopy and PMR spectroscopy.

Herstellung konjugierter Polyene mit Anthryl- undN-Methylpyridinium- Endgruppen

The synthesis of terminally donor-acceptor substituted polyenes from the respective aldehydes via Horner reactions is described. As donor group the 9-anthryl and as acceptor moiety the 4-(N-methyl)pyridinium residue were chosen. A bicyclo[2.2.2]octane unit was incorporated into the chain to interrupt the conjugation. The separation and characterization of the mixtures of Z/E- isomers obtained in the syntheses was possible.

Pyrylocyanines. 14. Unsymmetrical pyrylocyanines based on 2,3-polymethylene-4,6-diphenylpyrylium salts

Unsymmetrical 4,6-diphenylpyrylo-2-carbo- and dicarbocyanines, as well as the analogous pyridocyanines, containing 3-ethylbenzothiazolium and 1,3,3-trimethyl-3H-indolium residues and an ethylene or trimethylene bridging grouping between the α position of the polymethine chain and the β position of the pyrylium or pyridinium residue were synthesized. The introduction of bridging groups is generally accompanied by a bathochromic effect and intensification (in the pyrylocyanine series) or weakening (in the pyridocyanine series) of the fine structure of the absorption bands. On the basis of the deviations calculated from the centers of the absorption bands and the dependences of the vinylene shifts and the absorption band widths on the structure of the dyes it was concluded that the trimethylene bridging groups in the examined cases increase the electron-donor character of the heterocyclic residues in the dyes more markedly than the ethylene bridging groups.

The reactivity of phosphomono-and phosphodiester groups in oligonucleotides

The rate constants were estimated by phosphorus NMR spectroscopy for the reactions of alcohols (Tr-dT, 2-cyanoethanol) in pyridine with the main types of the reactive phosphorylating intermediates formed by treatment of pdT-Ac, pdTpdT-Ac, Tr-dTpdT-Ac, Tr-dTpdTpdT-Ac with 2, 4, 6-triisopropylbenzene-sulfonyl chloride (TPS): 1) B type derivatives with phosphomono ester (PME) group converted to a phosphoryl pyridinium residue; 2) C type derivatives with PME and phosphodiester (PDE) groups converted to trisubstituted pyrophosphate; 3) D type derivatives with PDE groups converted to tetrasubstituted pyrophosphate. The two latter types are partially present as cyclic intramolecular pyrophosphates Ci and Di. The reactivity of the intermediates decrease in the series B greater than Ci approximately Di greater than C approximately D. The Ci derivative of pdTpdT-Ac when obtained in dimethylformamide was found to be rather stable to hydrolysis and could be separated from the other dinucleotide derivatives by ion-exchange chromatography. The Arrhenius parameters of all steps of the conversion of PME group of pdT-Ac to B derivative and of the reaction of TPS with PDE group of dinucleoside phosphate Tr-dTpdT-Ac were measured.

Vibrational spectra of protonated poly-4-vinylpyridine

The IR and Raman spectra (400-200 cm −1) of the protonated and deuterated forms of atactic poly-4-vinylpyridine have been obtained. From the results obtained the main bands have been assigned to the appropriate normal vibrations. The frequencies of the vibrations of the ring of the protonated (deuterated) polymer are altered considerably, because of change in the electron density of the pyridinium residues, but the vibrations of the polymer chain are practically unaffected.