Synthesis and QSAR studies of pyrimido[4,5-d]pyrimidine-2,5-dione derivatives as potential antimicrobial agents

Synthesis of novel spiro[chromeno[2,3-d][1,3,4]thiadiazolo[3,2-a] pyrimidines via an isatin-based three-component reaction

This study presents an efficient and sustainable method for the synthesis of novel spiro[chromeno[2,3-d][1,3,4]thiadiazolo[3,2-a]pyrimidine-10,3'-indoline]-2',9,11-trione derivatives via a three-component condensation reaction is introduced. The reaction involves dimedone, 5H-[1,3,4]thiadiazolo[3,2-a]pyrimidine-5,7(6 H)-dione, and isatin derivatives, catalyzed by the economical and highly effective Keggin heteropolyacid (H₃PW₁₂O₄₀). This protocol achieves (70-90%) yields within relatively short reaction times under mild and solvent-free conditions. Using a green, cost-effective catalyst highlights the method's practicality and potential for broader applications in synthetic organic chemistry, offering an attractive route for spiro oxindole derivative synthesis.

Recent developments in polymer chemistry, medicinal chemistry and electro-optics using Ni and Pd-based catalytic systems

Catalysis is the fastest and continuously growing field in chemistry. A key component of this process is catalytic systems, which result in increased reaction rates and yields, as well as the ability to tailor the properties of products to the final application. With the development of catalysis, the requirements for catalysts used in these processes have also grown rapidly. Modern catalytic materials should overcome the challenges posed by the modern world of chemistry. They should be durable, and stable, have good catalytic properties, and allow catalytic processes to be carried out under mild and environmentally friendly conditions. In this article, we provide an overview of recent reports on the use of catalytic systems based on nickel and palladium ions in catalytic reactions, leading to functional materials used in the fields of medicinal chemistry, polymer chemistry and electro-optical materials chemistry. Research on the optimization and modification of existing synthetic methods, reports on the synthesis of new functional materials, and articles on new, more efficient catalytic systems that overcome the drawbacks of existing catalysts are described. The presented article reviews current knowledge, providing the newest information from the world of catalysis and synthesis of advanced functional materials, presenting potential directions for further development in these fields.

Functional redundancy and niche specialization in honeybee and Varroa microbiomes

The honeybee (Apis mellifera) is a key pollinator critical to global agriculture, facing threats from various stressors, including the ectoparasitic Varroa mite (Varroa destructor). Previous studies have identified shared bacteria between Varroa mites and honeybees, yet it remains unclear if these bacteria assemble similarly in both species. This study builds on existing knowledge by investigating co-occurrence patterns in the microbiomes of both Varroa mites and honeybees, shedding light on potential interactions. Leveraging 16S rRNA datasets, we conducted co-occurrence network analyses, explored Core Association Networks (CAN) and assess network robustness. Comparative network analyses revealed structural differences between honeybee and mite microbiomes, along with shared core features and microbial motifs. The mite network exhibited lower robustness, suggesting less resistance to taxa extension compared to honeybees. Furthermore, analyses of predicted functional profiling and taxa contribution revealed that common central pathways in the metabolic networks have different taxa contributing to Varroa mites and honeybee microbiomes. The results show that while both microbial systems exhibit functional redundancy, in which different taxa contribute to the functional stability and resilience of the ecosystem, there is evidence for niche specialization resulting in unique contributions to specific pathways in each part of this host-parasite system. The specificity of taxa contribution to key pathways offers targeted approaches to Varroa microbiome management and preserving honeybee microbiome. Our findings provide valuable insights into microbial interactions, aiding farmers and beekeepers in maintaining healthy and resilient bee colonies amid increasing Varroa mite infestations.

A potential DES catalyst for the fast and green synthesis of benzochromenopyrimidines and pyranopyrimidines

A gentisic acid based-Deep Eutectic Solvent (MTPPBr/GA-DES) was synthesized by mixing one mole of methyl triphenylphosphonium bromide (MTPPBr) and one mole of gentisic acid (GA: 2,5-dihydroxy-benzoic acid) based on the eutectic point phase diagram. Then, it was characterized by FT-IR, NMR, densitometer, and TGA/DTA techniques and used as a potent and novel catalyst for the fast and green synthesis of: (i) Five new 2(a-e) and five known 2(f-j) benzo[6,7]chromeno[2,3-d]pyrimidines and (ii) One new (3a) and eleven known 3(b-l) pyrano[2,3-d]pyrimidines, in solvent-free conditions, short reaction times, and high yields. It is important to mention that for the synthesis of 2(a-j), there is only one reference which states that the reaction times are extremely long (720-2400 min), while these times are reduced to approximately 35-50 min in our proposed strategy, indicatinging that the rate of reactions will be 20-48 times faster, which is the clear and most obvious advantage of our approach.

Practice of green chemistry strategies in synthetic organic chemistry: a glimpse of our sincere efforts in green chemistry research

This feature article summarises our recent contributions (2019-2023) in designing and developing a handful of promising organic transformations for accessing several diversely functionalised biologically relevant organic scaffolds, following the green chemistry principles, particularly focusing on the application of low-energy visible light, electrochemistry, ball-milling, ultrasound, and catalyst- and additive-free synthetic strategies.

SERS analysis, DFT, and solution effects regarding the structural and optical characteristics of folic acid biomolecule adsorbed on a Cu3 metal cluster

The optical characteristics of folic acid (ABP) and metal clusters of copper (Cu3) at various locations were investigated by means of density functional theory (DFT) computations. Mulliken charge analysis and molecular electrostatic potential (MEP) surface show how charge moves from Cu3 to ABP through the various groups. The peak in the UV-Vis spectra of ABP-Cu3 is caused by bonding and anti-bonding orbitals. In both vacuum and aqueous conditions, the polarizability values of ABP-Cu3 cluster are significantly higher than those of pure ABP, indicating a possible enhancement of the nonlinear optical (NLO) effect. Our research investigates the possibility of using ABP adsorbed metal clusters for NLO materials. Surface enhanced Raman scattering (SERS) in the ABP adsorbed metal clusters enhances the vibrational modes of ABP. Adsorption energies are found to be in the range -17.08 to -58.52 kcal/mol in vacuum and -53.34 to -93.44 kcal/mol in aqueous medium for the different configurations for ABP-Cu3. It indicates that metal clusters adsorbed by ABP are stable in the aqueous media. Experimental IR and UV-Vis of ABP is in agreement with theoretically predicted ones.

The continuous flow synthesis of azos

Azo compounds find use in many areas of science, displaying crucial properties for important applications as photoconductive organic pigments, fluorescent quenchers, paints, cosmetics, inks, and in the large and valuable dye industry. Due to the unstable intermediates, and the exothermic and fast reactions used in their synthesis, high value azo compounds are excellent candidates for continuous flow manufacturing. This comprehensive review covers the progress made to date on developing continuous flow systems for azo synthesis and reflects on the main challenges still to be addressed, including scale up, conversion, product purity, and environmental impact. The further development of integrated continuous flow processes has the potential to help tackle these challenges and deliver improved methods for azo compound generation.

Design, Docking, Characterisation, and Synthesis of Pyrimidine Derivatives for Antidepressant Activity

BACKGROUND

According to the report, in 2022, the prevalence rate of depression in India was 4.50%, and the cases stood at 56,675,969. The development of antidepressant agents has reduced the number of depressant and suicidal cases. Many researchers have found that pyrimidine possesses antidepressant activity. With this background, we thought of synthesizing pyrimidine derivatives.

OBJECTIVE

The objective of this study is to carry out molecular docking, synthesis, characterization, and evaluation of 2-((4,6-diphenylpyrimidin-2-yl)oxy)-N-phenylacetamide derivatives (17-26) as in vivo antidepressant agent.

METHOD

The designed compounds were checked for their activity using Molegro virtual docker (MVD) and were further synthesized. Benzaldehyde reacted with acetophenone to give compound (3), which gave compound (4) upon reaction with urea. In another reaction, substituted anilines (5) were reacted with chloroacetyl chloride (6) to yield compounds (7-16), which upon further reaction with compound (4) yielded the final derivatives (17-26). The synthesized compounds were characterized by spectral analysis and checked for their antidepressant activity.

RESULT

The MolDock scores of the derivatives ranged from -147.097 to -182.095, whereas of active ligand IXX_801 was -115.566. All the synthesized pyrimidine derivatives showed better affinity towards the Cryo-EM structure of the wild-type human serotonin transporter complexed with vilazodone, imipramine, and 15B8 Fab protein (PDB ID: 7LWD) as compared to standard drug clomipramine (-101.064). All the synthesized derivatives were screened for antidepressant activity at a 100mg/kg dose level compared to the standard clomipramine HCl at a dose level of 20mg/kg. Among all the synthesized derivatives, compound 24 showed the most potent antidepressant activity, and Compound 20 showed moderate antidepressant activity, which reduced the duration of immobility times to 35.42% and 31.97% at 100mg/kg dose level when compared to the control, respectively.

CONCLUSION

Compound 24 showed the highest MolDock score as well as found to be the most potent antidepressant agent.

Biological Evaluation of Anti-Cholinesterase Activity, in Silico Molecular Docking Studies, and DFT Calculations of Green Synthesized Thiadiazolo[3,2-a]pyrimidine Derivatives

A series of [1,3,4] thiadiazolo[3,2-a]pyrimidine-6-carboxylate derivatives 4(a-n) have been designed and synthesized as inhibitors of acetylcholinesterase (AChE). Synthesizing of thiadiazolo[3,2-a] pyrimidines was carried out in a single step, one-pot reaction using aromatic aldehydes, ethyl acetoacetate and different derivatives of 1,3,4-thiadiazoles (with molar ratio of 1 : 2 : 1, respectively) in conjunction with the catalyst, anhydrous iron(III) chloride by a grinding method under solvent-free conditions at room temperature. The in-vitro studies exhibited good potency for inhibiting AChE comparable with donepezil as the reference drug. The best results were obtained by Ethyl 2-(4-nitroophenyl)-7-methyl-5-(pyridin-3-yl)-5H-[1,3,4]thiadiazolo[3,2-a]pyrimidine-6-carboxylate 4n with IC50 value of 0.082±0.001 μM which was comparable with AChE inhibitory effects of donepezil (IC50 =0.079 μM).

Synthesis, Antifungal Ergosterol Inhibition, Antibiofilm Activities, and Molecular Docking on β-Tubulin and Sterol 14-Alpha Demethylase along with DFT-Based Quantum Mechanical Calculation of Pyrazole Containing Fused Pyridine-Pyrimidine Derivatives

Multidrug-resistant fungal infections have become much more common in recent years, especially in immune-compromised patients. Therefore, researchers and pharmaceutical professionals have focused on the development of novel antifungal agents that can tackle the problem of resistance. In continuation to this, a novel series of pyrazole-bearing pyrido[2,3-d]pyrimidine-2,4(1H,3H)-dione derivatives (4a-4o) have been developed. These compounds have been screened against Candida albicans, Aspergillus niger, and Aspergillus clavatus. The synthesized compounds were characterized by well-known spectroscopic techniques, i.e., IR, 1H NMR, 13C NMR, and mass spectrometry. In vitro antifungal results revealed that compound 4n showed activity against C. albicans having MIC value of 200 μg/mL. To know the plausible mode of action, the active derivatives were screened for anti-biofilm and ergosterol biosynthesis inhibition activities. The compounds 4h, 4j, 4k, and 4n showed greater ergosterol biosynthesis inhibition than the control DMSO. To comprehend how molecules interact with the receptor, studies of molecular docking of 4k and 4n have been performed on the homology-modeled protein of β-tubulin. The molecular docking revealed that the active compounds 4h, 4j, 4k, 4l, and 4n interacting with the active site amino acid of sterol 14-alpha demethylase (PDB ID: 5v5z) indicate one of the possible modes of action of ergosterol inhibition activity. The synthesized compounds 4c, 4e, 4h, 4i, 4j, 4k, 4l, and 4n inhibited biofilm formation and possessed the potential for anti-biofilm activity. DFT-based quantum mechanical calculations were carried out to optimize, predict, and compare the vibration modes of the molecule 4a.

The synergy between electrochemical substrate oxidation and the oxygen reduction reaction to enable aerobic oxidation

Aerobic substrate oxidation reactions catalyzed by a heterogeneous catalyst can be looked upon as two independent half-cell reactions, viz. anodic substrate oxidation and the cathodic oxygen reduction reaction (ORR). In this context, Fe PANI/C, a well-known catalyst for the ORR, is chosen to validate this hypothesis, wherein the anodic reaction is hydrazine oxidation. Fe PANI/C shows excellent activity in terms of the electrochemical ORR and hydrazine oxidation in both alkaline aqueous and non-aqueous media and taken together the aerobic oxidation efficacy of hydrazine-like small organic molecules is correlated with the electrochemical outcomes.

Design, synthesis, and biological evaluation of morpholinopyrimidine derivatives as anti-inflammatory agents

Here, we outline the synthesis of a few 2-methoxy-6-((4-(6-morpholinopyrimidin-4-yl)piperazin-1-yl)(phenyl)methyl)phenol derivatives and assess their anti-inflammatory activity in macrophage cells that have been stimulated by LPS. Among these newly synthesized morpholinopyrimidine derivatives, 2-methoxy-6-((4-methoxyphenyl)(4-(6-morpholinopyrimidin-4-yl)piperazin-1-yl)methyl)phenol (V4) and 2-((4-fluorophenyl)(4-(6-morpholinopyrimidin-4-yl)piperazin-1-yl)methyl)-6-methoxyphenol (V8) are two of the most active compounds which can inhibit the production of NO at non-cytotoxic concentrations. Our findings also showed that compounds V4 and V8 dramatically reduced iNOS and cyclooxygenase mRNA expression (COX-2) in LPS-stimulated RAW 264.7 macrophage cells; western blot analysis showed that the test compounds decreased the amount of iNOS and COX-2 protein expression, hence inhibiting the inflammatory response. We find through molecular docking studies that the chemicals had a strong affinity for the iNOS and COX-2 active sites and formed hydrophobic interactions with them. Therefore, use of these compounds could be suggested as a novel therapeutic strategy for inflammation-associated disorders.

1,2,4‐Triazole and benzimidazole fused dihydropyrimidine derivatives: Design, green synthesis, antibacterial, antitubercular, and antimalarial activities

This study reports the design and synthesis of novel 1,2,4-triazolo/benzimidazolo-pyrimidine linked 1-benzyl-4-[(p-tolyloxy)methyl]-1,2,3-triazole derivatives as potent antimicrobial agents according to their in vitro antibacterial, antifungal, antitubercular as well as antimalarial activities. An efficient, ecologically benign, and facile multicomponent synthesis was employed to synthesize these derivatives. The synthesis is accelerated with the mild and eco-friendly organocatalyst tetrabutylammonium bromide, providing a yield of 82%-96% within the short reaction time of 0.5-1.5 h. Compared with the MIC values of ciprofloxacin and ampicillin on the respective strains, compound d2 showed better activity against Escherichia coli and Streptococcus pyogenes and compound d8 showed better MIC against Staphylococcus aureus. Additionally, compounds d3, d4, and d5 showed potent MIC values against Pseudomonas aeruginosa. All triazolo-pyrimidine derivatives d1-d8 showed potent inhibitory action against Gram-positive strains. Compound e3 showed good potency against Mycobacterium tuberculosis H37Rv. The IC₅₀ values of d3 and e2 indicated better activity against Plasmodium falciparum. Collectively, these derivatives depict potent multifaceted activity and provide promising access for further antimicrobial and antimalarial investigations.

Experimental and theoretical study on the regioselective bis- or polyalkylation of 6-amino-2-mercapto-3H-pyrimidin-4-one using zeolite nano-gold catalyst and a quantum hybrid computational method

The synthetic utility of 6-amino-2-mercapto-3H-pyrimidin-4-one 3 as building blocks for new poly (pyrimidine) by alkylation using the bis(halo) compounds and zeolite nano-gold as a catalyst was investigated. Furthermore, the experimental findings by the theoretical Density functional theory (DFT) computations at the DFT/B3LYP level of theory, utilizing the 6-311++G (d,p) basis set in the gas phase, were used to investigate the distinct phases for Regio isomer 11a & 12a and 11b & 12b compounds was fair and of good quality. The stability of the 12a and 12b phases is higher than the other Regio isomer 11a and 11b phases, according to DFT modelling. By computing HOMO and LUMO pictures, the electronic parameters: dipole moment of these compounds in the ground state were theoretically investigated. Non-linear optical (NLO) characteristics and quantum chemical parameters were examined using frontier molecular orbital (FMO) analysis. Natural bond orbital analysis was used to characterize the charge transfer of the electron density in the investigated compounds (NBO). The molecular electrostatic potential surfaces (MEPS) plots have been generated, and absorption spectral analysis in different solvents has been theoretically and experimentally examined to better understand the reactivity spots. At the B3LYP/6-311G (d,p) level of theory, thermodynamic properties were also calculated. Finally, DFT calculations were used to connect the structure-activity relationship (SAR) with real antibacterial results for compounds 12a and 12b.

Hantzsch-Like Synthesis, DNA Photocleavage, DNA/BSA Binding, and Molecular Docking Studies of Bis(sulfanediyl)bis(tetrahydro-5-deazaflavin) Analogs Linked to Naphthalene Core

The cyclocondensation reaction of aldehydes with dimedone and bis(6-aminopyrimidin-4-one) in acetic acid led to the formation of the corresponding bis(pyrimido[4,5-b]quinoline-4,6-diones) which are known as bis(sulfanediyl)bis(tetrahydro-5-deazaflavin) analogs in a single step. Also, bis(pyrimido[4,5-b]quinoline-4,6-diones) which are linked to naphthyl core via phenoxymethyl linkage is prepared. The interactions of the synthesized compounds with DNA and bovine serum albumin (BSA) were studied. Gel electrophoresis assay was used to show the capability of the compounds to photocleave the supercoiled pBR322 plasmid DNA in UV-A (365 nm). Besides, the most photocleavable compound, bis(tetrahydropyrimido[4,5-b]quinoline-4,6-dione) linked to pyridin-3-yl at position-5 exhibits good binding affinities toward CT-DNA and BSA as supported by UV/VIS spectral studies. In addition to the experimental findings, a molecular docking simulation was performed to collect detailed binding data for this compound to both biomolecules.

Catalyst- and Additive-Free C(sp3)-H Functionalization of (Thio)barbituric Acids via C-5 Dehydrogenative Aza-Coupling Under Ambient Conditions

A one-pot room-temperature-based three-component reaction strategy has been accomplished to access a new series of bio-relevant barbituric/2-thiobarbituric acid hydrazones from the reaction between barbituric/2-thiobarbituric acids, primary aromatic amines, and tert-butyl nitrite in an acetonitrile solvent, without the aid of any catalysts/additives. The ambient reaction conditions can efficiently implement the C(sp³)-H functionalization of barbituric/2-thiobarbituric acids via C-5 dehydrogenative aza-coupling. The process does not require column chromatographic purification; pure products are obtained by simple filtration of the resulting reaction mixture, followed by washing the crude residue with distilled water. The catalyst-free ambient reaction conditions, operational simplicity, broad substrate scope and tolerance for various functional groups, no need for chromatographic purification, good to excellent yields of products within reasonable reaction times in minutes, clean reaction profile, and gram-scale synthetic applicability make this procedure attractive, green, and cost-effective.

Experimental and DFT investigation on N-functionalized biochars for enhanced removal of Cr(VI)

In this study, N-functionalized biochars with varied structural characteristics were designed by loading poplar leaf with different amounts of urea at 1:1 and 1:3 ratios through pyrolysis method. The addition of urea significantly increased the N content of biochar and facilitated the formation of amine (-NH-, -NH₂), imine (-HCNH), benzimidazole (-C₇H₅N₂), imidazole (-C₃H₃N₂), and pyrimidine (-C₄H₃N₂) groups due to substitution reaction and Maillard reaction. The effect of pH on Cr(VI) removal suggested that decrease in solution pH favored the formation of electrostatic attraction between the protonated functional groups and HCrO₄^-. And, experimental and density functional theory study were used to probe adsorption behaviors and adsorption mechanism which N-functionalized biochars interacted with Cr(VI). The protonation energy calculations indicated that N atoms in newly formed N-containing groups were better proton acceptors. Adsorption kinetics and isotherm experiments exhibited that N-functionalized biochars had greater removal rate and removal capacity for Cr(VI). The removal rate of Cr(VI) on N-functionalized biochar was 10.5-15.5 times that of untreated biochar. Meanwhile, N-functionalized biochar of NB3 with the largest number of adsorption sites for -C₇H₅N₂, -NH₂, -OH, -C₃H₃N₂, and phthalic acid (-C₈H₅O₄) exhibited the supreme adsorption capacity for Cr(VI) through H bonds and the highest adsorption energy was -5.01 kcal/mol. These mechanistic findings on the protonation and adsorption capacity are useful for better understanding the functions of N-functionalized biochars, thereby providing a guide for their use in various environmental applications.

Innovative antimicrobial substances based on uracil S-derivatives

The problem of antimicrobial resistance is an important global public health challenge. We propose that a development of new antibiotic compounds around known natural substances is a solution to this problem. We investigate reengineer natural products into potent antibiotics. Uracil fragment is abundant in nature and significant to treat infectious diseases due to its affection to the replication of the bacterial chromosome. 12 new uracil S-derivatives were obtained and tested for their in vitro antimicrobial properties. N³ -(thietan-3-yl)- and N³ -(1,1-dioxothietan-3-yl)uracils derivatives were synthesized by thietanylation of 6-methyluracil with 2-chloromethylthiirane and subsequent oxidation of the thietan ring. A method of their alkylation with ethyl-2-chloroacetate was developed and acetohydrazides containing 3-(thietan-3-yl)- and 3-(1,1-dioxothietan-3-yl)uracilyls fragments in the acetyl group were obtained by hydrazinolysis of 2-(thietanyluracil-1-yl)acetic acid ethyl esters. Their interaction with β-dicarbonyl compounds, anhydride of mono- and dicarboxylic acids was studied. Antimicrobial activity was determined by the agar diffusion method on test organisms: S. aureus, E. coli, P. vulgaris, K. pneumoniae, C. diversus, E. aerogenes, P. aeruginosa, S. abosit. N-acyl-5-hydroxypyrazolines and N,N'-diacylhydrazines of 6-methyluracil thietanyl- and dioxothietanyl derivatives showed high antimicrobial activity, which is consistent with the results of structure activity relationship analysis (MIC 0.1-10 μg/ml).

Immobilized Palladium Nanoparticles on Phosphanamine-grafted Cellulose for Arylation of Uracil

Background:

The synthesis of 5-arylation uracil nucleosides is an imperative challenge, especially for the method of Suzuki reaction using N-unprotected uracil as materials, which holds the potential to enhance the yield.

Objective:

The objective of the study was to find a more efficient catalyst to increase the yield of aryluracils and aryluridines.

Methods:

We first constructed the phosphanamine-grafted cellulose (PAGC) from cellulose material. Then, we prepared the nanocatalyst PAGC/Pd(0) through heating and reducing the mixture of PAGC and Pa(OAc)2.

Results:

When using this nanocatalyst to catalyze the Suzuki reaction of 5-iodouracil or 5-iodouridine and aryl heterocyclic boronic acids, the arylation yields have been significantly improved.

Conclusion:

This means that the resultant nanocatalyst exhibits a remarkable catalytic efficacy for Suzuki arylation of 5-iodouracil and 5-iodouridine.

Substituent and Solvent Polarity on the Spectroscopic Properties in Azo Derivatives of 2-Hydroxynaphthalene and Their Difluoroboranes Complexes

Novel fluorescent dyes such as difluoroborane complexes of 1-phenylazonaphthalen-2-ol derivatives were successfully synthesized and characterized with a focus on the influence of a substituent and a solvent on the basic photophysical properties. ¹H, ¹¹B, ¹³C, ¹⁵N, and ¹⁹F nuclear magnetic resonance (NMR) spectra of substituted 1-phenylazonaphthalen-2-ol difluoroboranes and their parent azo dyes were recorded and discussed. The absorption and emission properties of synthesized compounds were investigated in solvents of varying polarity. They were found to be fluorescent despite the presence of the azo group. The azo group rotation was blocked by complexing with -BF₂ to get a red shift in absorption. Solvent-dependent spectral properties of compounds were investigated using Lipper-Mataga and Bakhshiev plot. The calculated DFT energies and Frontier Molecular Orbitals calculations of the studied compounds were proved to be consistent with the experimental observations.

Structural and theoretical studies of 4-chloro-2-methyl-6-oxo-3,6-dideuteropyrimidin-1-ium chloride (d 6)

The title compound, C5D6ClN2O+·Cl-, crystallizes in the ortho-rhom-bic space group, Pbcm, and consists of a 4-chloro-2-methyl-6-oxo-3,6-di-hydro-pyrimidin-1-ium cation and a chloride anion where both moieties lie on a crystallographic mirror. The cation is disordered and was refined as two equivalent forms with occupancies of 0.750 (4)/0.250 (4), while the chloride anion is triply disordered with occupancies of 0.774 (12), 0.12 (2), and 0.11 (2). Unusually, the bond angles around the C=O unit range from 127.2 (6) to 115.2 (3)° and similar angles have been found in other structures containing a 6-oxo-3,6-di-hydro-pyrimidin-1-ium cation, including the monclinic polymorph of the title compound, which crystallizes in the monoclinic space group P21/c [Kawai et al. (1973 ▸). Cryst. Struct. Comm. 2, 663-666]. The cations and anions pack into sheets in the ab plane linked by N-H⋯Cl hydrogen bonds as well as C-H⋯O and Cl⋯O inter-actions. In graph-set notation, these form R 3 3(11) and R 3 2(9) rings. Theoretical calculations seem to indicate that the reason for the unusual angles at the sp 2 C is the electrostatic inter-action between the oxygen atom and the adjacent N-H hydrogen.

Research developments in the syntheses, anti-inflammatory activities and structure-activity relationships of pyrimidines

Pyrimidines are aromatic heterocyclic compounds that contain two nitrogen atoms at positions 1 and 3 of the six-membered ring. Numerous natural and synthetic pyrimidines are known to exist. They display a range of pharmacological effects including antioxidants, antibacterial, antiviral, antifungal, antituberculosis, and anti-inflammatory. This review sums up recent developments in the synthesis, anti-inflammatory effects, and structure-activity relationships (SARs) of pyrimidine derivatives. Numerous methods for the synthesis of pyrimidines are described. Anti-inflammatory effects of pyrimidines are attributed to their inhibitory response versus the expression and activities of certain vital inflammatory mediators namely prostaglandin E2, inducible nitric oxide synthase, tumor necrosis factor-α, nuclear factor κB, leukotrienes, and some interleukins. Literature studies reveal that a large number of pyrimidines exhibit potent anti-inflammatory effects. SARs of numerous pyrimidines have been discussed in detail. Several possible research guidelines and suggestions for the development of new pyrimidines as anti-inflammatory agents are also given. Detailed SAR analysis and prospects together provide clues for the synthesis of novel pyrimidine analogs possessing enhanced anti-inflammatory activities with minimum toxicity.

Modified-amino acid/peptide pyrimidine analogs: synthesis, structural characterization and DFT studies of N-(pyrimidyl)gabapentine and N-(pyrimidyl)baclofen

H-Bonding networks and π–π and halogen bonding interactions in the crystal structures of N-modified amino acid pyrimidine analogs are investigated using DFT calculations and X-ray crystallography analysis.

Oxidative Dehydrogenation of Hydrazobenzenes toward Azo Compounds Catalyzed by tert-Butyl Nitrite in EtOH

We describe a tert-butyl nitrite-catalyzed oxidative dehydrogenation of hydrazobenzenes for producing azobenzenes. This method proceeds at ambient temperature and under an atmospheric environment by employing eco-friendly EtOH as the medium, representing a mild, general route to the synthesis of various symmetrical and nonsymmetrical azobenzenes in excellent yields with broad functional group tolerance.

One-pot synthesis of azo compounds in the absence of acidic or alkaline additives

A one-pot method for the synthesis of azo compounds by the reaction of β-naphthol with aryl amines using t-BuONO as the nitrosonium source in DCM at room temperature was developed. This method features mild reaction conditions, a simple experimental procedure, and is free of acidic or alkaline additives.

Multicomponent synthesis of dispiroheterocycles using a magnetically separable and reusable heterogeneous catalyst

Dispiroheterocycles have been synthesized by pseudo-four component reaction of 6-aminouracil/6-amino-2-thiouracil/2-amino-1,3,4-thiadiazole, p-toluidine and isatins in an ethanol-water mixture as solvent using β-cyclodextrin functionalized Fe₃O₄ nanoparticles as a magnetically separable and reusable heterogeneous catalyst. The nanocatalyst was synthesized and characterized by physicochemical characterization including Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD).

Quantitative structure-toxicity relationships of organic chemicals against Pseudokirchneriella subcapitata

Predicting the toxicity of organic toxicants to aquatic life through chemometric approach is challenging area. In this paper, a six-descriptor quantitative structure-activity/toxicity relationship (QSAR/QSTR) model was successfully developed for the toxicity pEC₁₀ of organic chemicals against Pseudokirchneriella subcapitata, by applying support vector machine (SVM) together with genetic algorithm. A sufficiently large data set consisting of 334 organic chemicals was randomly divided into a training set (167 compounds) and a test set (167 compounds) with a ratio of 1:1. The optimal SVM model possesses coefficient of determination R² of 0.76 and mean absolute error (MAE) of 0.60 for the training set and R² of 0.75 and MAE of 0.61 for the test set. Compared with other models reported in the literature, our SVM model for the toxicity pEC₁₀ shows significant statistical quality and satisfactory predictive ability, although it has fewer molecular descriptors and more samples in the test set. A QSTR model for pEC₅₀ of organic chemicals against Pseudokirchneriella subcapitata was also developed with the same subsets and molecular descriptors.

Efficient Synthesis, SC-XRD, and Theoretical Studies of O-Benzenesulfonylated Pyrimidines: Role of Noncovalent Interaction Influence in Their Supramolecular Network

Crystalline organic compounds, 2-amino-6-methylpyrimidin-4-yl benzenesulfonate (AMPBS) and 2,6-diaminopyrimidin-4-yl benzenesulfonate (DAPBS), were prepared via O-benzenesulfonylation of 2-amino-6-methylpyrimidin-4-ol 1 and 2,6-diaminopyrimidin-4-ol 2, respectively. The structural interpretations were achieved unambiguously by single-crystal X-ray diffraction (SC-XRD) analysis. The Hirshfeld surface study showed that C-H···O, N-H···N, and especially C-H···C hydrogen bond interactions are the key contributors to the intermolecular stabilization in the crystal. Density functional theory (DFT) studies were used to obtain a better understanding of natural bond orbitals (NBOs) and nonlinear optical (NLO) analysis for AMPBS and DAPBS at the B3LYP/6-311G(d,p) level. The time-dependent density functional theory (TD-DFT)/CAM-B3LYP/6-311G(d,p) level was employed for frontier molecular orbital analysis of both compounds. DFT-based vibrations for C-H, C=N, N-H, and stretching for C-C were found to be in good agreement with the experimental data. Overall, the theoretical findings were acquired in correspondence to the SC-XRD-based parameters. Intracharge transfer occurred in AMPBS and DAPBS compounds, which was evaluated through FMO activity. Global reactivity indices had been acquired utilizing energies of HOMO-LUMO orbitals. Overall, the theoretical findings related to AMPBS and DAPBS consist of promising correspondence to experimental findings. The theoretical-based study also exhibited that both AMPBS and DAPBS compounds contain promising NLO features.

Series of Functionalized 5-(2-Arylimidazo[1,2-a]pyridin-3-yl)pyrimidine-2,4(1H,3H)-diones: A Water-Mediated Three-Component Catalyst-Free Protocol Revisited

A water-mediated and catalyst-free practical method for the synthesis of a new series of pharmaceutically interesting functionalized 5-(2-arylimidazo[1,2-a]pyridin-3-yl)pyrimidine-2,4(1H,3H)-diones has been accomplished based on a one-pot multicomponent reaction between arylglyoxal monohydrates, 2-aminopyridines/2-aminopyrimidine, and barbituric/N,N-dimethylbarbituric acids under reflux conditions. The salient features of this protocol are avoidance of any additive/catalyst and toxic organic solvents, use of water as reaction medium, clean reaction profiles, operational simplicity, ease of product isolation/purification without the aid of tedious column chromatography, good to excellent yields, and high atom-economy and low E-factor.

DESIGN, In silico Modeling, Toxicity study and Synthesis of Novel Substituted Semicarbazide Derivatives of Pyrimidine: An Antitubercular Agent

Background:

A series of 1-(2-(2-amino-5-carbamoyl-6-(1-(substitutedphenyl) prop-1-enyl) pyrimidin-4-yloxy)acetyl) semicarbazide (4a-i) derivatives was synthesized from substituted aromatic aldehydes, ethyl cyanoacetate and guanidine hydrochloride and characterized by analytical and spectral data, FTIR, 1H-NMR and Mass spectroscopy data.

Methods:

The antiTB action of the synthesized compounds was screened in comparison with the standard drug Rifampicin using MABA assay method. The SAR of substituted aromatic aldehydes with modification at ortho, meta and para positions with electron withdrawing group.

Results:

The compounds 1-(2-(2-amino-5- carbamoyl-6-(1-(2-fluorophenyl) prop-1-enyl) pyrimidin-4- yloxy) acetyl) semicarbazide and 1-(2-(2-amino- 5-carbamoyl-6-(1-(3-chlorophenyl) prop-1-enyl) pyrimidin-4-yloxy) acetyl) semicarbazide showed equal MIC values against Mycobacterium tuberculosis H37Ra with the value of 3.90μg/ml.

Conclusion:

The SAR study revealed that the antiTB activity of the synthesized compounds were affected by lipophilicity of the substituent.