Synthesis of pyrazole encompassing 2-pyridone derivatives as antibacterial agents

A novel bakuchiol aminoguanidine derivative induces apoptosis in human triple-negative breast cancer cells

OBJECTIVES

To synthesize new bakuchiol aminoguanidine derivatives and test their effect on viability and apoptosis of human triple-negative breast cancer (TNBC) cells.

METHODS

Two bakuchiol derivatives 1 and 2 were obtained by formylation and Shiff base reaction of bakuchol. The structures of derivatives 1 and 2 were identified by 1H-NMR, 13C-NMR, and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) analysis. Human TNBC MDA-MB-231 cells were treated with bakuchiol and its derivatives and cell viability was measured by MTT assay. Apoptosis was detected by fluorescence microscopy and flow cytometry with Annexin V-FITC/PI staining. The expressions of apoptosis-related proteins were analyzed with Western blotting. The JC-1 and reactive oxygen species (ROS) assay kits were used to determine the effect of new bakuchiol derivatives on mitochondrial function.

RESULTS

Based on spectroscopic analysis, a new bakuchiol schiff base derivative was elucidated as 2-{(E)-5-[(S, E)-3, 7-dimethyl-3-vinylocta-1, 6-dien-1-yl]-2-hydroxylbenzylidene} hydrazine-1-carboximidamide (derivative 2). Bakuchiol and its derivatives 1 and 2 all showed cytotoxic activity against the MDA-MB-231 cells. Derivative 2 exhibited the most potent cytotoxic activity to MDA-MB-231 cell with IC50 of (13.11±1.09), (6.91±1.78), and (2.23±1.32) μmol/L after 24, 48, and 72 h. It had low toxicity to normal mouse liver (AML-12) cells with IC50 of (31.23±1.58) μmol/L at 72 h. Fluorescence microscopy and flow cytometry demonstrated apoptosis in breast cancer cells after treating with derivative 2 in a concentration dependent manner. Western blotting showed that after derivative 2 treatment, the expression of apoptosis-related proteins cytochrome C, cleaving caspase-3 and Bax/Bcl-2 radio in MDA-MB-231 cells increased; in addition, apoptosis was associated with the decreased mitochondrial membrane potential and increased reactive oxygen species accumulation.

CONCLUSIONS

The novel bakuchiol aminoguanidine derivative (derivative 2) is capable of inducing apoptosis in MDA-MB-231 cells, but has low toxicity to normal liver cells, suggesting that it may be used as a lead compound for an anti-TNBC agent.

Regioselective Synthesis of Cycloalkane-fused Pyrazolo[4,3-e]pyridines through Tandem Reaction of 5-aminopyrazoles, Cyclic Ketones and Electron-rich Olefins

BACKGROUND

Pyrazolopyridines are interesting fused heterocyclic pharmacophores that combine pyrazole and pyridine; two privileged nuclei extensively studied and with a wide range of applications. They can be obtained by a broad variety of synthetic methods among which multicomponent reactions have gained importance, especially from 5-aminopyrazoles and dielectrophilic reagents. However, the search for new approaches more in tune with sustainable chemistry and the use of unconventional heating in three-component synthesis are open and highly relevant study fields.

METHODS

A novel, practical and efficient three-component synthesis of cycloalkane-fused pyrazolo[ 4,3-e]pyridines was developed through a tandem reaction of 5-aminopyrazoles, cyclic ketones and electron-rich olefins, using microwave induction in perfluorinated solvent and iodine as catalyst.

RESULTS

The microwave-induced three-component approach applied in this work promoted the construction of 10 new pyrazolopyridines with high speed and excellent control of regioselectivity, favoring the linear product with good yields; where the versatility of electron-rich olefins in iodine-catalyzed cascade heterocyclizations, granted the additional benefit of easy isolation and the possibility to reuse the fluorous phase.

CONCLUSION

Although pyrazolopyridines have been synthetically explored because of their structural and biological properties, most of the reported synthetic methods use common or even toxic organic solvents and conventional heating or multi-step processes. In contrast, this study applied a multicomponent methodology in a single step by microwave induction and with the versatility provided in this case by the use of perfluorinated solvent, which allowed easy isolation of the final product and recovery of the fluorous phase.

New Pyrazole-Clubbed Pyrimidine or Pyrazoline Hybrids as Anti-Methicillin-Resistant Staphylococcus aureus Agents: Design, Synthesis, In Vitro and In Vivo Evaluation, and Molecular Modeling Simulation

Two hybrid series of pyrazole-clubbed pyrimidines 5a-c and pyrazole-clubbed pyrazoline compounds 6a,b and 7 were designed as attractive scaffolds to be investigated in vitro and in vivo for antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. From the results of the in vitro antibacterial screening, compound 5c showed excellent activity (minimal inhibitory concentration, MIC = 521 μM) when compared with that of the reference antibiotic levofloxacin (MIC = 346 μM). The inhibition of the target dihydrofolate reductase (DHFR) enzyme by compounds 4 and 5a-c (IC50 = 5.00 ± 0.23, 4.20 ± 0.20, 4.10 ± 0.19, and 4.00 ± 0.18 μM, respectively) was found to be better than the reference drug trimethoprim (IC50 = 5.54 ± 0.28 μM). Molecular modeling simulation results have justified the order of activity of all the newly synthesized compounds as DHFR enzyme inhibitors, and compound 5c exhibited the best binding profile (-13.6169386 kcal/mol). Hence, the most potent inhibitor of the DHFR enzyme, 5c, was chosen to be evaluated in vivo for its activity in treating MRSA-induced keratitis in rats and that, in turn, significantly (P < 0.0001) reduced infection in rats when compared to MRSA-treated group results.

Amino-Pyrazoles in Medicinal Chemistry: A Review

A pyrazole nucleus is an easy-to-prepare scaffold with large therapeutic potential. Consequently, the search for new pyrazole-based compounds is of great interest to the academic community as well as industry. In the last ten years, a large number of papers and reviews on the design, synthesis, and biological evaluation of different classes of pyrazoles and many pyrazole-containing compounds have been published. However, an overview of pyrazole derivatives bearing a free amino group at the 3, 4, or 5 position (namely, 3-aminopyrazoles, 4-aminopyrazoles, and 5-aminopyrazoles, respectively) and their biological properties is still missing, despite the fact that aminopyrazoles are advantageous frameworks able to provide useful ligands for receptors or enzymes, such as p38MAPK, and different kinases, COX and others, as well as targets important for bacterial and virus infections. With the aim to fill this gap, the present review focuses on aminopyrazole-based compounds studied as active agents in different therapeutic areas, with particular attention on the design and structure-activity relationships defined by each class of compounds. In particular, the most relevant results have been obtained for anticancer/anti-inflammatory compounds, as the recent approval of Pirtobrutinib demonstrates. The data reported here are collected from different databases (Scifinder, Web of Science, Scopus, Google Scholar, and Pubmed) using "aminopyrazole" as the keyword.

Pyrazole scaffold-based derivatives: A glimpse of α-glucosidase inhibitory activity, SAR, and route of synthesis

The α-glucosidase is a validated target to develop drugs for treating type 2 diabetes mellitus. The existing α-glucosidase inhibitors have certain shortcomings related to side effects and route of synthesis. Accordingly, it is inevitable to develop new chemical templates as α-glucosidase inhibitors. Pyrazole derivatives have a special place in medicinal chemistry because of various biological activities. Recently, pyrazole-based heterocyclic compounds have emerged as a promising scaffold to develop α-glucosidase inhibitors. This study focuses on the recently reported pyrazole-based α-glucosidase inhibitors, including their biological activity (in vivo, in vitro, and in silico), structure-activity relationship, and ways of synthesis. The literature revealed the development of several promising pyrazole-based α-glucosidase inhibitors and new synthetic routes for their preparation. The encouraging α-glucosidase inhibitory results of the pyrazole-based heterocyclic compounds make them an attractive target for further research. The authors also foresee the arrival of the pyrazole-based α-glucosidase inhibitors in clinical practice.

Synthesis, Physicochemical Properties and Molecular Docking of New Benzothiazole Derivatives as Antimicrobial Agents Targeting DHPS Enzyme

The drug-resistance problem is widely spread and becoming more common in community-acquired and nosocomial strains of bacteria. Therefore, finding new antimicrobial agents remains an important drug target. From this perspective, new derivatives of benzothiazole were synthesized and evaluated for their antimicrobial activity and ability to inhibit the DHPS enzyme. The synthesis was carried out by the reaction of benzothiazole N-arylsulphonylhydrazone with N-aryl-2-cyano-3-(dimethylamino)acrylamide, N-aryl-3-(dimethylamino)prop-2-en-1-one, arylaldehydes or diazonium salt of arylamine derivatives, which led to the formation of N-arylsulfonylpyridones 6a-d (yield 60-70%) and 12a-c (yield 50-60%),N-(2-(benzo[d]thiazole-2-yl)-3-arylacryloyl-4-methylsulfonohydrazide 14a-c (yield 60-65%), 4-(benzo[d]thiazole-2-yl)-5-aryl-1H-pyrazol-3(2H)-one 16a-c (yield 65-75%), and N'-(2-(benzo[d]thiazol-2-yl)-2-(2-arylhydrazono)acetyl)-4-arylsulfonohydrazide 19a-e (yield 85-70%). The antimicrobial evaluations resulted into a variety of microbial activities against the tested strains. Most compounds showed antimicrobial activity against S. aureus with an MIC range of 0.025 to 2.609 mM. The most active compound, 16c, exhibited superior activity against the S. aureus strain with an of MIC 0.025 mM among all tested compounds, outperforming both standard drugs ampicillin and sulfadiazine. The physicochemical-pharmacokinetic properties of the synthesized compounds were studied, and it was discovered that some compounds do not violate rule of five and have good bioavailability and drug-likeness scores. The five antimicrobial potent compounds with good physicochemical-pharmacokinetic properties were then examined for their inhibition of DHPS enzyme. According to the finding, three compounds, 16a-c, had IC₅₀ values comparable to the standard drug and revealed that compound 16b was the most active compound with an IC₅₀ value of 7.85 μg/mL, which is comparable to that of sulfadiazine (standard drug) with an IC₅₀ value of 7.13 μg/mL. A docking study was performed to better understand the interaction of potent compounds with the binding sites of the DHPS enzyme, which revealed that compounds 16a-c are linked by two arene-H interactions with Lys220 within the PABA pocket.

Polysorbate 21 Can Modulate the Antibacterial Potential of Two Pyrazol Derivatives

The combination of two compounds with known antimicrobial activity may, in some cases, be an effective way to limit the resistance to antibiotics of specific pathogens. Molecules carrying pyrazole moiety are well known for their bioactive properties and have wide applicability in the medical and pharmaceutical field. Surfactants have, among other useful properties, the ability to affect the growth of microorganisms. The paper reports on the effect of the combination of two pyrazole derivatives, (1H-pyrazol-1-yl) methanol 1-hydroxymethylpyrazole (SAM1) and 1,1'methandiylbis (1H-pyrazol) (AM1), with sorbitan monolaurate (polysorbate 21, Tween 21, T21) on the growth of Gram-positive and Gram-negative bacteria. The results demonstrated a different ability of this combination to inhibit Staphylococcus aureus and Escherichia coli. T21 intensified the inhibitory activity of the pyrazoles to a greater extent in the Gram-negative bacteria compared to the Gram-positive ones, a fact confirmed by time-kill experiments. The experimental data showed that the association of T21 with the pyrazoles led to the increased release of intracellular material and a more intense uptake of crystal violet, which indicates that the potentiation of the antibacterial effect was based on the modification of the normal permeability of bacterial cells. T21 acted as a modulating factor and increased the permeability of the membrane, allowing the accelerated penetration of the pyrazoles inside the bacterial cells. This fact is important in controlling the global increase in microbial resistance to antibiotics and antimicrobials and finding viable solutions to overcome the antibiotic crisis. The paper highlights the possibility of using non-toxic surfactant molecules in antimicrobial combinations with practical applications. This could widen the range of adjuvants in applications which would be useful in the control of resistant microorganisms.

Synthesis, antitubercular, antimicrobial activities and molecular docking study of quinoline bearing dihydropyrimidines

In order to develop the antimicrobial and antitubercular agents, we have derived quinoline bearing dihydropyrimidine analogues 5a-o and structures of these compounds were determined by spectroscopic techniques. Further, we have calculated the molecular properties prediction and drug-likeness by Molinspiration property calculation toolkit and MolSoft software, respectively. The most active compound against Mycobacterium tuberculosis (5m, MIC = 0.20 µg/mL) also possessed a maximum drug-likeness model score (0.42). Compounds 5m, 5g and 5k were possessed promising antibacterial activity against tested bacterial species. Compound 5k was the only compound to have eye-catcher antifungal activity. Furthermore, the MTT cytotoxicity results on HeLa cells suggested lower cytotoxicity of biologically active compounds. Supramolecular interactions of the synthesized compounds has been assessed my means of molecular docking studies. Although all the synthesized compounds are showing preferably good interactions with their respective proteins, their binding free energies values suggest that these molecules are preferred for antitubercular activity rather than antimicrobial activity.

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

Microwave-assisted (MWA) multicomponent reactions (MCRs) have successfully emerged as one of the useful tools in the synthesis of biologically relevant heterocycles. These reactions are strategically employed for the generation of a variety of heterocycles along with multiple point diversifications. Over the last few decades classical MCRs such as Ugi, Biginelli, etc. have witnessed enhanced yield and efficiency with microwave assistance. The highlights of MWA-MCRs are high yields, reduced reaction time, selectivity, atom economy and simpler purification techniques, such an approach can accelerate the drug discovery process. The present review focuses on the recent advances in MWA-MCRs and their mechanistic insights over the past decade and shed light on its advantage over the conventional approach.

Synthesis of novel pyrazole tagged pyridine derivatives; their antimicrobial activity

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Novel pyrazole tagged pyridine derivatives 5a-n synthesized starting from 3-cyano-4-trifluoromethyl-6- thiophenyl 2(1H) pyridone 1. Compound 1 on hydrolysis followed by decarboxylation resulted in 4-trifluoro-methyl-6- thiophenyl 2(1H)pyridone 2. Compound 2 treated with POCl3 to get 2- chloro-4-trifluoromethyl-6- thiophenyl pyridine 3 further reaction with hydrazine hydrate, which resulted in the formation of compound 4. Compound 4 on reaction with different substituted 1,3-diketones in ethanol reflux condition to afford pyrazole substituted pyridine derivatives 5a-n. All derivatives were tested against Gram-positive and Gram-negative bacterial strains and different Candida strains by well diffusion method, compounds 5k and 5l showed significant activity. The binding mode of 5k and 5l also studied by molecular docking studies.

Pyrazole-based analogs as potential antibacterial agents against methicillin-resistance staphylococcus aureus (MRSA) and its SAR elucidation

Methicillin-resistant Staphylococcus aureus (MRSA) is becoming lethal to humanity due to easy transmission and difficult-to-treat skin and flimsy diseases. The most threatening aspect is the rapid resistance development of MRSA to any approved antibiotics, including vancomycin. The development of new, efficient, and nontoxic drug candidate to fight against MRSA isolates is the need of the hour. The intriguing molecular structure and versatile bioactive pyrazole core attracting to development required novel antibiotics. This review presents the decade developments of pyrazole-containing derivatives with a broad antibacterial movement against diverged bacterial strains. In specific, we correlated the efficacy of structurally diversified pyrazole analogs against MRSA and discussed different angles of structure-activity relationship (SAR). The current survey highlights pyrazole hybrids' present scenario on MRSA studies, covering articles published from 2011 to 2020. This collective information may become an excellent platform to plan and develop new pyrazole-based small MRSA growth inhibitors with minimal side effects.

Kuma Bamboo Grass (Sasa veitchii) Extracts Exhibit Protective Effects Against Atypical Aeromonas salmonicida Infection in Goldfish (Carassius auratus)

Atypical Aeromonas salmonicida ( i.e. subsp. achromogenes and subsp. masoucida) are one of the major opportunistic pathogens that cause ulcer diseases in a variety of fishes, in which this pathogen has become a worldwide economic threat in sectors that handle of particular high-priced ornamental fishes like varicolored carp and goldfish due to appearance damages. Here we reported that the kuma bamboo grass (Sasa veitchii) extracts (KBGE) that contained a variety of fatty acids, exhibited antibacterial activity against nine Aeromonas strains including 5 atypical A. salmonicida strains. Experimental challenges with four atypical A. salmonicida strains revealed that supplementation with 375 to 750 μg/ml of the KBGE restored the survival of goldfish in coincidence of inhibition of both bacterial replication and superoxide dismutase (SOD) activity upon infection, compared with those of untreated control. Together, our data demonstrating the antibacterial effects of the plant extracts proposes its possible implication for prevention of Aeromonas infection in the ornamental fish.

Design, synthesis, and apoptosis-promoting effect evaluation of novel pyrazole with benzo[d]thiazole derivatives containing aminoguanidine units

New pyrazole with benzo[d]thiazoles containing hydrazinecarboximidamide substituent was synthesised and evaluated for cytotoxicity and apoptotic activity using the MTT assay, flow cytometry, and Western blot analysis. Among the compounds studied, (E)-2-((1-(6-((4-fluorobenzyl)oxy)benzo[d]thiazol-2-yl)-3-phenyl-1H- pyrazol-4-yl)methylene) hydrazinecarboximidamide (8l) was potent, with IC₅₀ values of 2.41 µM, 2.23 µM, 3.75 µM and 2.31 µM in vitro anti-proliferative activity testing against triple-negative breast cancer cell line MDA-MB-231, non-triple-negative breast cancer MCF-7 cells, and human hepatocarcinoma HepG2 cells, and SMMC-7721 cells, respectively. Especially, the activity against MDA-MB-231 was similar to that of Doxorubicin, which was used as a positive control in this study. Next, the Annexin V/PI flow cytometry assay was used at different concentrations of compound 8l to demonstrate that compound 81 induced apoptosis of MDA-MB-231 cells in a concentration-dependent manner. Finally, these results were further verified by Western blot analysis. Taken together, the results of this study revealed that compound 8l may be a potential anticancer compound play a significant role in the subsequent researches.

Directed Zincation or Magnesiation of the 2-Pyridone and 2,7-Naphthyridone Scaffold Using TMP Bases

A regioselective zincation of the 2-pyridone and 2,7-naphthyridone scaffolds has been developed. Zincations of the methoxyethoxymethyl (MEM)-protected compounds using TMP₂Zn·2MgCl₂·2LiCl (TMP = 2,2,6,6-tetramethylpiperidyl) followed by trapping with electrophiles provided functionalized 2-pyridones and 2,7-naphthyridones. I/Mg exchange of iodinated 2-pyridone and 2,7-naphthyridone using i-PrMgCl·LiCl afforded magnesiated intermediates that reacted with electrophiles. A second magnesiation of the 2-pyridone scaffold was achieved by using TMPMgCl·LiCl. Additionally, we report CoCl₂-catalyzed cross-couplings of the 1-chloro-2,7-naphthyridines with arylzinc halides.

Synthesis and Pharmacological Activities of Pyrazole Derivatives: A Review

Pyrazole and its derivatives are considered a pharmacologically important active scaffold that possesses almost all types of pharmacological activities. The presence of this nucleus in pharmacological agents of diverse therapeutic categories such as celecoxib, a potent anti-inflammatory, the antipsychotic CDPPB, the anti-obesity drug rimonabant, difenamizole, an analgesic, betazole, a H2-receptor agonist and the antidepressant agent fezolamide have proved the pharmacological potential of the pyrazole moiety. Owing to this diversity in the biological field, this nucleus has attracted the attention of many researchers to study its skeleton chemically and biologically. This review highlights the different synthesis methods and the pharmacological properties of pyrazole derivatives. Studies on the synthesis and biological activity of pyrazole derivatives developed by many scientists around the globe are reported.

Synthesis and Pharmacological Activities of Pyrazole Derivatives: A Review

Pyrazole and its derivatives are considered a pharmacologically important active scaffold that possesses almost all types of pharmacological activities. The presence of this nucleus in pharmacological agents of diverse therapeutic categories such as celecoxib, a potent anti-inflammatory, the antipsychotic CDPPB, the anti-obesity drug rimonabant, difenamizole, an analgesic, betazole, a H2-receptor agonist and the antidepressant agent fezolamide have proved the pharmacological potential of the pyrazole moiety. Owing to this diversity in the biological field, this nucleus has attracted the attention of many researchers to study its skeleton chemically and biologically. This review highlights the different synthesis methods and the pharmacological properties of pyrazole derivatives. Studies on the synthesis and biological activity of pyrazole derivatives developed by many scientists around the globe are reported.

Synthesis and evaluation of the antibiotic and adjuvant antibiotic potential of organotin(IV) derivatives

A series of organotin(IV) derivatives was investigated in vitro for their antibiotic and adjuvant antibiotic properties (efflux pump inhibitors) against Staphylococcus aureus strains that overexpress efflux pump proteins for norfloxacin (SA-1199B), erythromycin (RN-4220) and tetracycline (IS-58). Most organotin(IV) compounds showed significant antibacterial activity with small Minimum Inhibitory Concentration (MIC) values, some of which were close to 1.0μg/mL (3.1μM), but this feature was also associated with substantial cytotoxicity. Nevertheless, the cytotoxicity of these organotin(IV) compounds can be overcome when they are used as antibiotic adjuvants. Their remarkable adjuvant antibiotic properties allow potentiation of the action of tetracycline (against IS-58 strain) by up to 128-fold. This likely indicates that they can act as putative inhibitors of bacterial efflux pumps. These results reinforce organotin(IV) complexes as promising antibacterial agents, and many of these complexes, if associated with antibiotics, can act as potential adjuvant antibiotic candidates.

Synthesis, characterization, and antimicrobial evaluation of novel 5-benzoyl-N-substituted amino- and 5-benzoyl-N-sulfonylamino-4-alkylsulfanyl-2-pyridones

The present research describes the synthesis of novel 5-benzoyl-N-substituted-amino- and 5-benzoyl-N-sulfonylamino-4-alkylsulfanyl-2-pyridones 5a–c and 6a–c via the reaction of 2-benzoyl-3,3-bis(alkylthio)acrylonitriles 2a–c with N-cyanoacetohydrazide 3 and cyanoaceto-N-phenylsulfonylhydrazide 4, respectively. Also, the reactivity of the compounds 5a–c toward hydrazine hydrate to give product 1H-pyrazolo[4,3-c]pyridine derivative 7 was studied. In addition, the reactivity of the 2a–c toward 1-cyanoacetyl-4 arylidenesemicarbazides 8a–c afforded 3,5-dihydro[1,2,4]triazolo[1,5-a]pyridine-6-carbonitrile derivatives (12–14)a–c, which reacted with hydrazine hydrate to give 3H-pyrazolo[4,3-c][1,2,4]triazolo[1,5-a]pyridine-6-carbonitrile derivatives 15a–c. The structures of the new products were characterized based on ¹H nuclear magnetic resonance, ¹³C nuclear magnetic resonance, infrared, mass-spectroscopy, and elemental analyses. The products were screened in vitro for their antibacterial and antifungal activity properties.

Crystal structure of 2-(4-methyl-3-phenylthiazol-2(3H)-ylidene)malononitrile, C13H9N3S

C13H9N3S, monoclinic, P21/m (no. 11), a = 8.5468(4) Å, b = 7.0166(4) Å, c = 10.3407(5) Å, β = 106.225(2)°, V = 595.43(5) Å3, Z = 2, R gt(F) = 0.062, wR ref(F 2) = 0.161, T = 150 K.

Facile one-pot four-component synthesis of 3,4-dihydro-2-pyridone derivatives: novel urease inhibitor scaffold

In the current study, a series of 3,4-dihydro-2-pyridone derivatives were synthesized in a one-pot fourcomponent reaction of Meldrum's acid, benzaldehyde derivatives, methyl acetoacetate, and ammonium acetate. SiO2-Pr-SO3H was used as an efficient catalyst for the synthesis of the target compounds under solvent-free conditions. The most probable mechanism for this reaction has been discussed. The advantages of this methodology are high product yields, being environmentally benign, short reaction times, and easy handling. Eight 2-pyridinone derivatives were evaluated for their inhibitory activities against Jack bean urease. Molecular docking study of the synthesized compounds was also evaluated. All compounds showed good activities against urease and among them, 4-(4-nitrophenyl)-5-methoxycarbonyl-6-methyl-3,4-dihydropyridone (5a) showed the most potent activity (IC₅₀ = 29.12 µM), more potent than hydroxyurea as the reference drug (IC₅₀ = 100.0 µM). Also, the results from docking studies were in good agreement with those obtained with in vitro assay. According to the docking studies methionine (Met) 637 and nitro phenyl ring cause n-π interaction between lone pair of sulfur atom and π aromatic ring. Moreover, hydrophobic interactions existed between compound 5a and alanine (ALA) 636, ALA 440, and isoleucine 411. The results indicated that the inhibitory activities increased with the increase of electron withdrawing ability of the groups despite a less important role of lipophilicity in increasing the inhibitory activity.

Novel iron doped calcium oxalates as promising heterogeneous catalysts for one-pot multi-component synthesis of pyranopyrazoles

The co-precipitation method using a surface modifier, glutamic acid was employed in the design of iron doped calcium oxalates (Fe-CaOx).

Oxyfunctionalization of pyridine derivatives using whole cells of Burkholderia sp. MAK1

Pyridinols and pyridinamines are important intermediates with many applications in chemical industry. The pyridine derivatives are in great demand as synthons for pharmaceutical products. Moreover, pyridines are used either as biologically active substances or as building blocks for polymers with unique physical properties. Application of enzymes or whole cells is an attractive strategy for preparation of hydroxylated pyridines since the methods for chemical synthesis of pyridinols, particularly aminopyridinols, are usually limited or inefficient. Burkholderia sp. MAK1 (DSM102049), capable of using pyridin-2-ol as the sole carbon and energy source, was isolated from soil. Whole cells of Burkholderia sp. MAK1 were confirmed to possess a good ability to convert different pyridin-2-amines and pyridin-2-ones into their 5-hydroxy derivatives. Moreover, several methylpyridines as well as methylated pyrazines were converted to appropriate N-oxides. In conclusion, regioselective oxyfunctionalization of pyridine derivatives using whole cells of Burkholderia sp. MAK1 is a promising method for the preparation of various pyridin-5-ols and pyridin-N-oxides.

Design, synthesis and herbicidal evaluation of novel 4-(1H-pyrazol-1-yl)pyrimidine derivatives

BACKGROUND

A series of novel pyrazolylpyrimidine derivatives were designed, synthesised and characterised by IR, (1) H NMR, (13) C NMR, mass spectroscopy and elemental analysis. The herbicidal activities of 30 pyrazolylpyrimidine derivatives were assessed.

RESULTS

Nine compounds caused good herbicidal activity for Pennisetum alopecuroides L. Among them, N-ethyl-6-[5-methyl-3-(trifluoromethyl)-1H-pyrazol-1-yl]-pyrimidin-4-amine exhibited the strongest inhibitory activity against the root growth of P. alopecuroides, with an IC50 of 1.90 mg L(-1) . 2-Methyl-4-[5-methyl-3-(trifluoromethyl)-1H-pyrazol-1-yl]-6-(prop-2-yn-1-yloxy)pyrimidine produced the highest inhibition of chlorophyll level in seedlings of P. alopecuroides (IC50  = 3.14 mg L(-1) ).

CONCLUSION

The structure-activity relationship indicated that the alkynyloxy group at the 6-position on the pyrimidine ring played a very important role for bleaching activities. When the alkynyloxy group was replaced by alkoxy, amino, alkylthio and alkylsulfonyl groups, the bleaching activities of the compounds were diminished. However, the compounds substituted by an amino at the 6-position of the pyrimidine ring exhibited excellent inhibition activities against weed root growth.

HOMO-LUMO, UV, NLO, NMR and vibrational analysis of 3-methyl-1-phenylpyrazole using FT-IR, FT-RAMAN FT-NMR spectra and HF-DFT computational methods

In this paper, the spectral analysis of 3-methyl-1-phenylpyrazole is carried out using the FT-IR, FT Raman, FT NMR and UV-Vis spectra with the help of quantum mechanical computations using HF and density functional theories. The different conformers of the compound and their minimum energies are studied using B3LYP functional with 6-311+G (d,p) basis set and the most stable conformer with minimum energy was identified and the same conformer was used for further computations. The computed wave numbers from different methods are scaled so as to agree with the experimental values and the scaling factors are reported. All the modes of vibrations are assigned and the structure the molecule is analyzed in terms of parameters like bond length, bond angle and dihedral angle predicted by both HF and B3LYP methods with 6-311+G (d,p) and 6-311++G (d,p) basis sets. The values of dipole moment (μ), polarizability (α) and hyperpolarizability (β) of the molecule are reported, using which the non-linear property of the molecule is discussed. The HOMO-LUMO mappings are reported which reveals the different charge transfer possibilities within the molecule. The isotropic chemical shifts predicted for (1)H and (13)C atoms using gauge invariant atomic orbital (GIAO) theory show good agreement with experimental shifts. NBO analysis is carried out to picture the charge transfer between the localized bonds and lone pairs. The thermodynamic properties (heat capacity, entropy and enthalpy) at different temperatures are also calculated.