Pyridine Acid Research Articles

N2H4 Derived Sulfonic Acids: Hydrazine Disulfonate, [(SO3)HNNH(SO3)]2-, and Hydrazine Iso-disulfonate, [H2NN(SO3)2]2.

The reaction of hydrazinium sulfate and chlorosulfonic acid in pyridine leads to the pyridinium salt of the hydrazine disulfonate anion, [(SO3)HNNH(SO3)]2-. The salt is the starting material for the preparation of further hydrazine disulfonates, for example of alkaline metals and barium. In all compounds, the [(SO3)HNNH(SO3)]2- anion adopts the gauche conformation. The conformer is chiral but all of the investigated compounds crystallize as racemates. The disulfonate anion can occur in another constitution with the two sulfonate groups attached to only one nitrogen atom. This so-called hydrazine iso-disulfonate, [H2NN(SO3)2]2-, has been prepared through a substitution reaction between potassium imidodisulfonate, K2[HN(SO3)2], and hydroxylamine-O-sulfonic acid, H2NOSO3H. The hydrazine iso-disulfonate anion has been crystallized as potassium and barium compound, respectively. The compounds were characterized by XRD, vibrational spectroscopy, DFT calculations and thermal analyses.

GPI anchoring controls cell wall integrity, immune evasion and surface localization of ChFEM1 for infection of Cochlibolus heterostrophus1

Glycosylphosphatidylinositol (GPI) anchoring is one of the common post-translational modifications in eukaryotic cells. In fungi, it exerts a wide range of biological functions by targeting proteins to the cell wall, but only few studies focus on the roles of GPI anchoring in plant pathogenic fungi. Here, we reveal a role of GPI anchoring in the maize fungal pathogen Cochlibolus heterostrophus. We found that GPI-anchored proteins were widely accumulated in hyphae, appressorium and infection hyphae of C. heterostrophus. Deletion of ChGPI7, which encodes a key enzyme involved in the biosynthesis of GPI anchors, resulted in significant reduction of vegetative growth and conidiation, as well as virulence due to impairment of appressorium formation and invasive growth. The ΔChgpi7 mutants also showed severe defects in cell wall integrity, resulting in a significant reduction of stress resistance. Deletion of ChGPI7 and hydrofluoric acid (HF) pyridine treatment both led to removal of cell wall GPI-anchored proteins and exposure of chitin, the results suggested that GPI anchored proteins could protect chitin from host immune recognition. A total of 124 proteins were predicted to be GPI anchored proteins in C. heterostrophus, including a putative cell wall glycoprotein ChFEM1. Deletion of ChFEM1 also resulted in significant reduction in virulence and defects in infection structures, as well as cell wall integrity. We further found that cell wall localization and protein abundance of ChFEM1 were affected by ChGPI7. Our results showed that GPI anchoring regulates cell wall integrity and immune evasion for infection of C. heterostrophus.

Impact of lanthanum ion exchange and steaming dealumination on middle distillate production using nanosized Y zeolite catalysts in hydrocracking reactions.

In the field of hydrocracking reactions, achieving optimal middle distillate yields remains a persistent challenge with commercially available zeolite Y catalysts. This limitation is attributed to challenges related to diffusion constraints within the catalyst. In response, we present a promising solution not only to these problems but also to the challenges encountered in nanosized Y zeolites when attempting to generate acidic sites within their structure and when analyzing their performance in vacuum gas oil hydrocracking. NiMo catalysts based on nanosized Y zeolites with different crystal sizes exchanged with lanthanum, effectively address diffusion issues and significantly enhance catalyst performance compared to dealuminated nanosized and commercial Y zeolite under the same reaction conditions. The catalysts were characterized by TGA, ICP-OES, XPS, N2 physisorption, FT-IR for pyridine acidity, TEM-mapping, and the 3-methyl thiophene reaction to test the hydrogenating capacity. Surface analysis and microscopy showed greater porosity in the catalysts with smaller zeolites and different arrangements of their components. The catalysts based on steamed protonated nanosized Y zeolites with a larger size and lanthanide nanosized Y zeolite with a smaller size yielded more middle distillates. Research provides a comprehensive analysis, providing a correlation between the catalytic performance and the size of the nanosized Y zeolite.

Metabolomic Profiling Reveals the Anti-Herbivore Mechanisms of Rice (Oryza sativa).

The use of secondary metabolites of rice to control pests has become a research hotspot, but little is known about the mechanism of rice self-resistance. In this study, metabolomics analysis was performed on two groups of rice (T1, with insect pests; T2, without pests), indicating that fatty acids, alkaloids, and phenolic acids were significantly up-regulated in T1. The up-regulated metabolites (p-value < 0.1) were enriched in linoleic acid metabolism, terpene, piperidine, and pyridine alkaloid biosynthesis, α-linolenic acid metabolism, and tryptophan metabolism. Six significantly up-regulated differential metabolites in T1 were screened out: N-trans-feruloyl-3-methoxytyramine (1), N-trans-feruloyltyramine (2), N-trans-p-coumaroyltyramine (3), N-cis-feruloyltyramine (4), N-phenylacetyl-L-glutamine (5), and benzamide (6). The insect growth inhibitory activities of these six different metabolites were determined, and the results show that compound 1 had the highest activity, which significantly inhibited the growth of Chilo suppressalis by 59.63%. Compounds 2-4 also showed a good inhibitory effect on the growth of Chilo suppressalis, while the other compounds had no significant effect. RNA-seq analyses showed that larval exposure to compound 1 up-regulated the genes that were significantly enriched in ribosome biogenesis in eukaryotes, the cell cycle, ribosomes, and other pathways. The down-regulated genes were significantly enriched in metabolic pathways, oxidative phosphorylation, the citrate cycle (TCA cycle), and other pathways. Eighteen up-regulated genes and fifteen down-regulated genes from the above significantly enriched pathways were screened out and verified by real-time quantitative PCR. The activities of detoxification enzymes (glutathione S-transferase (GST); UDP-glucuronosyltransferase (UGT); and carboxylesterase (CarE)) under larval exposure to compound 1 were measured, which indicated that the activity of GST was significantly inhibited by compound 1, while the activities of the UGT and CarE enzymes did not significantly change. As determined by UPLC-MS, the contents of compound 1 in the T1 and T2 groups were 8.55 ng/g and 0.53 ng/g, respectively, which indicated that pest insects significantly induced the synthesis of compound 1. Compound 1 may enhance rice insect resistance by inhibiting the detoxification enzyme activity and metabolism of Chilo suppressalis, as well as promoting cell proliferation to affect its normal growth and development process. The chemical-ecological mechanism of the insect resistance of rice is preliminarily clarified in this paper.

Pressurized liquid extraction and gas chromatography/mass spectrometry for determination of nitrated polycyclic aromatic hydrocarbons adsorbed on refractory diesel particles

A pressurized liquid extraction (PLE) technique was evaluated in this study and optimized using response surface methodology (RSM) for the determination of polycyclic aromatic hydrocarbons and their nitro derivatives from diesel particulate matter. A central composite design (CCD) was applied for the study of three parameters (temperature, nature of solvent and static time) and the optimal conditions were determined for a time of 9 min and a temperature of 145 °C and dichloromethane as extraction solvent. With the GC/MS analytical technique, the limits of detection (LOD) obtained range from 0.3 to 1.5 µg.L-1 for PAHs and from 4.6 to 8 µg.L-1 for nitrated PAHs. Also, this method allowed excellent recoveries of NPAH adsorbed on diesel soot particles (R ≥ 90%) using a mixture of solvents (1% acetic acid in pyridine). The PLE process developed in this research is quantitative and reproducible while using much less solvent than conventional extraction methods.

L-Aspartic acid pyridinium salts: In silico, synthesis and adjuvant vs antibiotic antibacterial evaluation

In the present study, a new series of chiral L-aspartic acid pyridinium salts have been designed, guided by molecular docking as antiemetics via TrySR or DNA GryB inhibitors, as well as an adjuvant to chloramphenicol via CAT-III inhibitor to continue with antibacterial in vitro study. Newly designed molecules have been synthesized by chemistry route and their characterization was done by using NMR & HRMS techniques. Biological evaluation of synthesized compounds has been done on Gram-negative bacteria, to E. coli The in vitro evaluation results have shown that pyridinium salts 3a, 3e, 3i, 3j, 3k and 3o as an antibacterial, in addition to 3o and 3i, as an adjuvant against E. coli resistant to chloramphenicol.

Leveraging the relative strengths of hydrogen and halogen bonds to control nanostructures

Halogen bonds (XBs) and hydrogen bonds (HBs) present a straightforward yet effective strategy for controlling nanostructure morphology. The self-assembled nanopattern, modulated by the relative strengths of XBs and HBs, has rarely been studied using analogous molecules. This research systematically evaluates the relationship between the strengths of Br···O hetero-XBs and N···H HBs in directing the formation of 2D supramolecular co-assembled structures. In this work, tetracarboxylic acid (PEDA), featuring four carboxyl substitutions, forms a stable hydrogen-bonded Rosette network that can function as a template for trapping guest molecules of complementary shape and size. The star-shaped bromine-substituted 1,3,5-tris(3,5-dibromophenyl)benzene (TDB) and 2,4,6-tri(4-pyridyl)-1,3,5-triazine (TPT) serve as XB donor and HB acceptor respectively, thus capable of acting as guest molecules co-assembly with the PEDA at the heptanoic acid/HOPG interface. Bimolecular co-assembly patterns resulting from these combinations were investigated using scanning tunneling microscopy (STM) and supported by density functional theory (DFT) calculations. The findings indicate that TDB molecules can be accommodated within the triangular cavities of the Rosette network due to the weaker Br···O hetero-XB. Concurrently, the similar star-shaped TPT can co-assemble with PEDA to form an acid–pyridine–acid Ladder-like network based on stronger N···H HBs. Therefore, Br···O hetero-XBs seemingly play no decisive role in the coassembly process of PEDA and TDB. Conversely, N···H HBs hold evident significance in the coassembly of PEDA and TPT. This work potentially holds substantial value for the future design and customization of devices employing the interplay of XBs and HBs.

Cobalt(II)-Catalyzed Enantioselective Propargyl Claisen Rearrangement: Access to Allenyl-Substituted Quaternary β-Ketoesters.

Highly enantioselective propargyl Claisen rearrangement of O-propargyl β-ketoesters was achieved under 2.5 mol % of the chiral cobalt complex as the catalyst under mild reaction conditions. With Co(OTf)2 as the Lewis acid and C1-symmetric imidazoline-pyrroloimidazolone pyridine as the ligand, diverse chiral allenyl-substituted all-carbon quaternary β-ketoesters were obtained in good yields (up to 97% yield) and high enantioselectivities (up to 98% ee).

Effect of lignin acetylation on the mechanical properties of lignin-poly-lactic acid biocomposites for advanced applications

Bioplastics that possess characteristics like durability and low cost are desired for versatile applications in industries such as automotive manufacturing, marine transport manufacturing, aerospace applications, and the building industry. The automotive industry is an example of an industry that is now shifting towards a more focused approach addressing the issue concerning sustainability and the development of sustainable material. To achieve a lightweight and sustainable construction, one of the methods used by the automotive original equipment manufacturers is by substituting conventional fossil-based, non-renewable composites, and metallic materials with a bio-based alternative. One of the drawbacks with biobased polymers can be the poor interfacial adhesion, leading to poor mechanical properties when compares to conventional material. The aim of this research is to investigate if a low-cost by-product could be used as a component in a composite matrix material in the automotive industry to reduce the final weight and increase the non-petrochemical material usage of composite material without compromising the thermal and mechanicals properties demanded. In this research, lignin was chemically altered by esterification the functional groups to increase the compatibility with polylactic acid. The esterification was performed with the use of acetic acid anhydride and pyridine. To evaluate and determine the esterification, Fourier transform Infrared Spectroscopy was used. By blending the modified lignin with polylactic acid the intention was to improve the thermomechanical properties and the interfacial linkage between the components. The effects of lignin acetylation on the tensile properties, impact strength, and thermal stability and moisture repellence behaviour were investigated. According to the experimental results the modification of lignin, increased the impact strength for all the blends containing acetylated lignin compares to pristine lignin. The largest increase observed was for blends containing 20 wt% acetylated lignin and polylactic acid, which resulted in a 74% improvement compared with the blend composed of pristine lignin and polylactic acid. Similarly, the thermal stability was improved significantly with acetylation of the lignin. Moreover, the moisture repellence behaviour was also increased. The reason for the improved properties can be explained by the better interfacial compatibility between lignin and polylactic acid matrix. An increased thermal stability and a moisture repellent behaviour of the blends containing chemically modified lignin could be observed when compared with neat polylactic acid which makes the acetylation treatment of lignin a possible approach for the future of biocomposite production.

Inter- vs. Intra-Molecular Hydrogen Bond in Complexes of Nitrophthalic Acids with Pyridine.

This study covers the analysis of isomeric forms of nitrophthalic acids with pyridine. This work dwells on the complementary experimental (X-ray, IR and Raman) and theoretical (Car-Parrinello Molecular Dynamics (CPMD) and Density Functional Theory (DFT)) studies of the obtained complexes. The conducted studies showed that steric repulsion between the nitro group in ortho-position and the carboxyl group causes significant isomeric changes. Modeling of the nitrophthalic acid-pyridine complex yielded a short strong intramolecular hydrogen bond (SSHB). The transition energy from the isomeric form with an intermolecular hydrogen bond to the isomeric form with an intramolecular hydrogen bond was estimated.

Diversifying Amino Acids and Peptides via Deaminative Reductive Cross-Couplings Leveraging High-Throughput Experimentation.

A deaminative reductive coupling of amino acid pyridinium salts with aryl bromides has been developed to enable efficient synthesis of noncanonical amino acids and diversification of peptides. This method transforms natural, commercially available lysine, ornithine, diaminobutanoic acid, and diaminopropanoic acid to aryl alanines and homologated derivatives with varying chain lengths. Attractive features include ability to transverse scales, tolerance of pharma-relevant (hetero)aryls and biorthogonal functional groups, and the applicability beyond monomeric amino acids to short and macrocyclic peptide substrates. The success of this work relied on high-throughput experimentation to identify complementary reaction conditions that proved critical for achieving the coupling of a broad scope of aryl bromides with a range of amino acid and peptide substrates including macrocyclic peptides.

In-vitro evaluation of immunomodulatory activity of sulphation-modified total ginsenosides derivative-3.

Ginseng has been used in biomedicine to prevent and treat decreased physical and mental capacities. Total ginsenosides (TG) from ginseng root which have antitumor and immune-enhancing properties, are the principal active components of Panax ginseng, while the sulphation-modified TG derivative-3 (SMTG-d3) was expected to enhance the anticancer activity in conventional medicinal treatments. The chlorosulphonic acid-pyridine technique, used for the sulfation modification of TG to improve their biological activity, and the infrared spectroscopic characteristics of TG and SMTG-d3 were investigated, and the effects of SMTG-d3 on immunocytes and cytokines relevant to tumor treatment were assessed. The MTT assay was used to assess the effect of TG and SMTG-d3 on the cytotoxicity and T-lymphocytic proliferation against mouse splenocytes. The LDH method was employed to evaluate NK activity induced by TG or SMTG-d3. The production levels of splenocytes-secreted IL-2 and IFN-γ and peritoneal macrophages-secreted TNF-α were determined using mouse ELISA kits. It showed that the ideal conditions for the sulfation modification of TG: the volume ratio of chlorosulfonic acid to pyridine lower than 1:2.5; controlled amount of chlorosulfonic acid; and a yield of 51.5% SMTG-d3 (2 h, < 45°C). SMTG-d3 showed two characteristic absorption peaks at 1,230 cm-1 and 810 cm-1, indicating the formation of sulfuric acid esters and the presence of sulfuric acid groups. SMTG-d3 exhibited higher antitumor immunological activity than TG by promoting the proliferation of T lymphocytes and the production of IFN-γ and TNF-α, thus enhancing NK cell activity, and reducing cytotoxicity. The findings imply sulfated modification represents an effective method of enhancing the immunomodulatory activities of TG and could be used as the basis for developing new drug target compounds; SMTG-d3 can serve as an antitumor immunomodulator and can be considered an effective and prospective herbal formulation in clinical applications.

Targeted degradation of refractory organic pollutants in wastewater based on molecularly imprinted catalytic materials: Adsorption process and degradation mechanism

In this study, the role of weak interactions in the targeted adsorption of refractory organic pollutants by imprinted catalysts (MIL100@MIP) was elucidated. Through the imprinting technique, the targeted adsorption capacity for sulfamethoxazole (SMX) was increased by 3 times. With the synergy of adsorption and degradation, the removal of SMX reached 49.03 mg/g in MIL100@MIP/PS system. Methacrylic acid (MAA), acrylamide (AM), and 4-vinyl pyridine (4-VP) were used to construct different imprinting recognition sites. UV–vis spectral analysis indicated that MIL100@MIP adsorbed SMX through weak interactions. Dynamic experiments showed that MIL100@MIP-4-VP exhibited the best adsorption performance. Density functional theory (DFT) calculations and wave function analysis indicated that π-π stacking played a dominant role in the SMX adsorption process. The solvent effect was investigated by dynamics simulation. Finally, three possible SMX degradation pathways and the catalytic mechanism of MIL100@MIP were proposed based on the EPR and intermediate product analysis. This study has valuable guidance for improving the targeted degradation performance of imprinted catalytic materials.

Abundant two-dimensional hydrogen-bonded co-assemblies of tetracarboxylic acid derivatives and pyridine derivatives studied by means of scanning tunneling microscopy

Through the introduction of different pyridine derivatives into carboxylic acid self-assembly structures, abundant co-assembly structures were constructed by converting the O–H⋯O hydrogen bond to O–H⋯N or C–H⋯N hydrogen bonds.

Fire retardant polyethylene terephthalate containing 4,4′-(hexafluoroisopropylidene)diphenol-substituted cyclotriphosphazene microspheres

Polyphosphazene derivatives are gaining popularity due to their eco-friendly character and high content of flame-retardant components. Herein, a polyphosphazene derivative (PZAF) microsphere was successfully synthesized utilizing an in-situ template approach, which was then employed as an additive flame retardant in polyethylene terephthalate (PET) to improve the fire safety. Thermogravimetric analysis revealed that PZAF promoted the pyrolysis of PET in advance to generate a stable char layer that protects the matrix from heat, consequently increasing char residues. With addition of 10 wt% PZAF, the PET nanocomposites obtained a V-0 grade in vertical combustion test and its LOI value increased from 24.2 vol% to 32.1 vol%. Moreover, the peak heat release and carbon monoxide production decreased by 46.6% and 50.6%, respectively. This was because the phosphonic acid fragments and pyridine ring compounds produced by the PZAF pyrolysis encouraged the development of a robust char layer. Meanwhile, the •PO radicals generated by the pyrolysis of PZAF could capture free radicals in the gas phase, ultimately ending the chain reaction of combustion. Also, mechanical properties of the PET nanocomposites were noticeably enhanced by the addition of 3 or 5 wt% PZAF.

Thrombin and Factor Xa Hydrolysis of Chromogenic Substrates in the Presence of Sulfated Derivatives of Galactomannan and Galactoglucomannan Natural Gels.

Polysaccharides are important structural components of all plant species. Gel-like polysaccharides have found wide application in various fields, including medicine, construction, and the food industry. In the present work, galactomannan and galactoglucomannan gel-like polysaccharides were modified with sulfate groups and their anticoagulant activity was studied. Sulfation with chlorosulfonic acid in pyridine and with sulfamic acid in pyridine and a sulfamic acid-urea deep eutectic solvent were used as synthesis routes. The resulting gel-like polysaccharide sulfates were studied by elemental analysis, Fourier-transform infrared spectroscopy, and gel permeation chromatography. It was established that the anticoagulant effect of sulfated galactoglucomannan (SGGM) and galactomannan (SGM-1 and SGM-2) is related to an independent antithrombin-independent decrease in the amidolytic activity of thrombin and factor Xa. It is shown that the inhibitory activity of SGGM and SGM-2 against the collagen-induced platelet aggregation can be an additional factor in selecting compounds that are most promising for modifying polymer surfaces to ensure resistance to blood clotting.

Sulfate Modification and Evaluation of in vitro Anti‐HIV Activity of Lycium Barbarum Polysaccharides

AbstractThis study investigated the feasibility of sulfate modification of Lycium barbarum polysaccharides (LBPs) and their potential anti‐HIV‐1 application. LBPs with different molecular weights were prepared by fractional precipitation from crude LBP via aqueous extraction, ethanol precipitation, and deproteinization. The purified LBPs (G1, G2, and G3) were sulfated using the chlorosulfonic acid pyridine method to obtain sulfated LBPs (G1S1–G1S4, G2S1–G2S4, and G3S1–G3S4) with different sulfur degrees of substitution. The anti‐HIV‐1 activity in vitro was evaluated via the TD50 from the cytotoxicity test and the IC50 inhibitory activity. The cytotoxicity and inhibitory activity in vitro were carried out using the CCK‐8 assay and MAGI test with Azidothymidine (AZT) as a positive control. The results show that the LBPs and the sulfated derivatives were not toxic towards CCK‐8 cells with TD50&gt;100 μg/mL and they had strong anti‐HIV‐1 activity with IC50 values of 0.02–0.12 μg/mL. Compared with the LBPs, the anti‐HIV‐1 activity of the sulfated LBPs increased with IC50 values from 0.0924–0.1206 μg/mL to 0.0206–0.0722 μg/mL. Sulfate modification of LBPs can increase their anti‐HIV pharmacological activity, the G1S4 (Mw=2.13×104 Da and DS=1.12) showed relatively good in vitro anti‐HIV‐1 activity with an IC50 value near that of AZT (0.0200 μg/mL). The results suggest further detailed in vivo studies are warranted for these promising candidates with anti‐HIV‐1 activity.

Energetics of carboxylic acid–pyridine heterosynthon revisited: A computational study of intermolecular hydrogen bond domination on phenylacetic acid–nicotinamide cocrystals

Abstract Carboxylic acid–pyridine heterosynthon (CPHS) is one of the most common synthons found in cocrystal packing. Phenylacetic acid (PYC)–nicotinamide (NIC) (PYCNIC) cocrystals were used as a computational model to assess the most important factor in the emergence of the synthon. Geometry optimization was carried out on every possible two molecules of PYC–NIC conformation based on B3LYP-D3BJ/6-311G (d,p). Various energetic parameters, including total energy, interaction energy, and hydrogen bond energy, were used to compare the existing conformation to the putative conformation. The conformation with CPHS has −53.87 kJ mol−1 of single intermolecular hydrogen bond energy (EHB), which is the strongest of all. It turns out that there is no other parameter better than EHB to describe the superiority of CPHS in PYCNIC.

Heteroleptic Zn(II)–Pentaiodobenzoate Complexes: Structures and Features of Halogen–Halogen Non-Covalent Interactions in Solid State

Reactions between Zn(II) nitrate, pentaiodobenzoic acid (HPIBA) and different pyridines in dimethylformamide (DMF) result in the formation of the heteroleptic neutral complexes [Zn(3,5-MePy)2PIBA2] (1) and [Zn(DMF)3(NO3)PIBA] (2). Both compounds were isolated in pure form, as shown by the PXRD data. The features of specific non-covalent interactions involving halogen atoms (halogen bonding) were examined by means of DFT calculations (QTAIM analysis and the estimation of corresponding energies).

Bi- or trinuclear 2-iodobenzoate complexes of Znii: crystal structures and luminescence

Reactions of zinc nitrate with 2-iodobenzoic acid (2-IBA) and different pyridines result in binuclear Znii carboxylate complexes [Zn2(2-IBA)4L2], where L = Py, 3-MePy and 3,5-Me2Py, while in the case of 2,4,6-Me3Py, trinuclear (2,4,6-Me3PyH)2[Zn3(2-IBA)6(OH)2] is formed.