Synthesis and antiviral activity of new 3-methyl-1,5-diphenyl-1H-pyrazole derivatives

A new series of 4-substituted 3-methyl-1,5-diphenyl-1H-pyrazoles 4–11 has been synthesized and evaluated for its in vitro antiviral activity and cytotoxicity against herpes simplex virus type-1 grown on Vero African green monkey kidney cells through plaque-reduction assay method using acyclovir as a positive control. The synthesis was achieved through Claisen-Schmidt condensation reaction of 3-methyl-1,5-diphenyl-1H-pyrazole-4-carbaldehyde (3) with acetophenone derivatives to give various enones 4a–f which are considered an important synthon for the construction of different heterocyclic rings as isoxazoline, pyrazoline, pyrimidine, pyridine, and fused pyridine via several synthetic routes. Biological evaluation of the prepared compounds showed that 3-(4-methylphenyl)-5-(3-methyl-1,5-diphenyl-1H-pyrazol-4-yl)-4,5-dihydroisoxazole (5f), 6-(4-methylphenyl)-N-[(3-(methylsulfanyl)phenyl)]-4-(3-methyl-1,5-diphenyl-1H-pyrazol-4-yl)pyrimidin-2-amine (7), 6-(4-bromophenyl)-4-(3-methyl-1,5-diphenyl-1H-pyrazol-4-yl)-2-oxo-1,2-dihydropyridine-3-carbonitrile (8), and 2-amino-6-(4-bromophenyl)-4-(3-methyl-1,5-diphenyl-1H-pyrazol-4-yl) pyridine-3-carbonitrile (9) exhibited strong antiviral activity with IC₅₀ (0.02, 0.04, 0.03, 0.03), respectively, compared to the used reference drug. The synthesized compounds were characterized by physical constants and the structures of the title compounds were confirmed by IR, ¹H NMR, mass spectra, and elemental analyses.     

Synthesis of some novel C-5 and N-3 substituted 2-(2-hydroxyphenylimino)thiazolidin-4-one derivatives with broad-spectrum antimicrobial activity

In the present article, compounds 5-((substituted-2-chloroquinolin-3-yl)methylene)-2-(2-hydroxyphenylimino)thiazolidin-4-ones (3a–k), 1-(2-(2-(2-hydroxyphenylimino)-4-oxothiazolidin-3-yl)-2-oxoethyl)pyrimidine-2,4,6(1H,3H,5H)-trione (6) and 1-(2-(5-((substituted-2-chloroquinolin-3-yl)methylene)-2-(2-hydroxyphenylimino)-4-oxothiazolidin-3-yl)-2-oxoethyl)pyrimidine-2,4,6(1H,3H,5H)-triones (8a–k) have been synthesized by substituting C-5 and N-3 position of parent compound 2-(2-hydroxyphenylimino)thiazolidin-4-one (1). Structures of the newly synthesized compounds were assigned on the basis of elemental analyses, IR, ¹H NMR, ¹³C NMR, and mass spectra. In vitro antimicrobial activity of target compounds (3a–k, 6 and 8a–k) was investigated against two Gram-positive, two Gram-negative bacteria and three fungal strains. Among the tested compounds (3e), (3f), and (3h) showed very good antifungal activity, while compound (6) showed very good antibacterial activity. Compounds (8e), (8f), and (8h) showed excellent antifungal and antibacterial activities.     

In vitro antimicrobial and antimycobacterial activity of some chalcones and their derivatives

In this study, novel series of chalcone derivatives, namely, 4-[4-(3-phenyl-acryloyl)-phenylamino]-chromen-2-one (5a–k) have been synthesized from the intermediate 4-(4-acetyl-phenylamino)-chromen-2-one (4). Cyclization reaction of chalcone (5a–k) with hydrazine hydrate, guanidine nitrate, and malononitrile gives the corresponding 4-[4-(1-acetyl-5-phenyl-4,5-dihydro-1H-pyrazol-3-yl)-phenylamino]-chromen-2-one (6a–k), 4-[4-(2-amino-6-phenyl-pyrimidin-4-yl)-phenylamino]-chromen-2-one (7a–k), and 2-amino-6-[4-(2-oxo-2H-chromen-4-ylamino)-phenyl]-4-phenyl-nicotinonitrile (8a–k) derivatives were synthesized. The newly synthesized compounds were evaluated for their antimycobacterial activity and antimicrobial activity against eight bacteria (S. aureus, B. cereus, E. coli, P. aeruginosa, K. pneumoniae, S. typhi, P. vulgaris, and S. flexneri) and four fungi (A. niger, C. albicans, A. fumigatus, and A. clavatus).     

Synthesis of new 3-aryl-4-(3-aryl-4,5-dihydro-1H-pyrazol-5-yl)-1-phenyl-1H-pyrazole derivatives as potential antimicrobial agents

New (E)-1-aryl-3-(3-aryl-1-phenyl-1H-pyrazol-4-yl)prop-2-en-1-ones 6 (pyrazolic chalcones) were synthesized from Claisen–Schmidt reaction of 3-aryl-1-phenylpyrazol-4-carboxaldehydes 4 with several acetophenone derivatives 5. Subsequently, the cyclocondensation reaction of chalcones 6 with phenylhydrazine in acetic acid medium afforded the new 3-aryl-4-(3-aryl-4,5-dihydro-1H-pyrazol-5-yl)-1-phenyl-1H-pyrazoles 7. The synthesized compounds were characterized by spectral studies and evaluated for their in vitro antibacterial activity against three pathogenic bacterial strains, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, and in vitro antifungal activity against three pathogenic fungal strains Aspergillus flavus, Chrysosporium keratinophilum, and Candida albicans.     

Tribuli fructus constituents protect against tacrine-induced cytotoxicity in HepG2 cells

A new phenolic amide, tribulusimide D (4-hydroxy-N-[3-(4-hydroxy-3-methoxyphenyl)-1-oxo-2-propen-1-yl]-3-methoxybenzamide) (1), together with a known phenolic amide, terrestriamide ((E)-3-(4-hydroxy-3-methoxyphenyl)-N-[2-(4-hydroxyphenyl)-2-oxoethyl]-prop-2-enamide) (2) and a flavonol glycoside, quercetin-3-O-β-d-glucopyranosyl-(1→6)-β-d-glucopyranoside (3) were isolated from the H₂O extract of Tribuli Fructus. Compounds 1 and 3 showed significant hepatoprotective activities, with EC₅₀ values of 13.46 ± 0.2 and 7.06 ± 0.7 μM, respectively, against tacrine-induced cytotoxicity in HepG2 cells.     

Synthesis of new quinoline-2-pyrazoline-based thiazolinone derivatives as potential antimicrobial agents

A series of 2-(5-(2-chloro-6-methylquinolin-3-yl)-3-(aryl)-4,5-dihydro-1H-pyrazol-1-yl)thiazol-4(5H)ones (4a–l) were synthesized and characterized by IR, ¹H NMR, ¹³C NMR, and mass spectra. All the synthesized compounds were tested for their in vitro antimicrobial activity against Escherichia coli (MTCC 443), Pseudomonas aeruginosa (MTCC 1688), Staphylococcus aureus (MTCC 96), Streptococcus pyogenes (MTCC 442), Candida albicans (MTCC 227), Aspergillus niger (MTCC 282), and Aspergillus clavatus (MTCC 1323) by serial broth dilution. Compounds 4e, 4f, 4g, 4i, 4j, and 4l were the most distinctive derivatives identified in present study because of their remarkable in vitro antimicrobial potency.     

Synthesis, characterization, and biological evaluation of certain 1,3-thiazolone derivatives bearing pyrazoline moiety as potential anti-breast cancer agents

A series of 5-arylidene-2-(3,5-diaryl-4,5-dihydro-1H-pyrazol-1-yl)-1,3-thiazol-4(5H)-ones were synthesized and screened for their in vitro antitumor activity against human breast adenocarcinoma cell line (MCF-7). Five of the test compounds exhibited good antitumor activity superior to the reference drug, doxorubicin, with IC₅₀ range 1.4–2.3 μM. Among the test compounds, 2-[3,5-bis(4-chlorophenyl)-4,5-dihydro-1H-pyrazol-1-yl]-5-(2-methoxybenzylidene)-1,3-thiazol-4(5H)-one (3i) was found to show the most potent anticancer activity.     

Pyridoquinolones containing azetidinones: synthesis and their biological evaluation

A series of pyridoquinolone 4-oxo-1,4-dihydro(4′-methyl-6′-chloropyrido[2,3-h])quinoline-3-[N-(substituted phenyl methylidine)]carbohydrazide 3a–j and 4-oxo-1,4-dihydro(4′-methyl-6′-chloropyrido[2,3-h])-3-[N-{(3-chloro-2-oxo-4-(substituted phenyl) azetidine-1-yl)amino}carbonyl] quinoline 4a–j have been synthesized via 4-oxo-1,4-dihydro-(4′-methyl-6′-chloropyrido[2,3-h])quinoline carboxylate 1. All the compounds were proved by IR, ¹H-NMR, ¹³C-NMR spectral studies and elemental analysis. Antibacterial activities (MIC) against E. coli, P. aeruginosa, S. aureus and S. pyogenes, and antifungal activities against C. albicans, A. niger and A. clavatus were screened, whereas selected compounds were screened against Mycobacterium tuberculosis H ₃₇ Rv and compared with standard drugs.     

Synthesis, characterization and antimicrobial screening of hybrid molecules containing benzimidazole-pyrazole and pyridine nucleus

The rising prevalence of multi-drug resistant Gram-positive, Gram-negative bacteria and fungi continues to provide momentum for search and development of novel active antimicrobial agents against these pathogens. In continuation to this, the present article deals with the synthesis and antimicrobial activity of a novel series of (3-(1H-benzo[d]imidazol-2-yl)-5-(aryl)-4,5-dihydro-1H-pyrazol-1-yl)(pyridin-4-yl)methanones 4a–n, synthesized by the reaction of benzimidazolyl chalcones with isoniazide 3. The structures of synthesized compounds were elucidated on the basis of IR, NMR, and mass spectra. The newly synthesized compounds 4a–n were screened for their antimicrobial activity against different strains of bacteria and fungi using serial broth dilution method. Compounds 4d, 4f, 4h, and 4g were found to be most active with MIC of 25?μg/mL against selected bacterial strains. Compounds 4c, 4g, and 4n were found to be most active with MIC of 100?μg/mL against selected fungal strains.     

3 + 2] Cycloaddition reactions of thioisatin with thiazolidine-2-carboxylic acid: a versatile route to new heterocyclic scaffolds

Background

Fused heterocyclic 1,2,4-triazoles have acquired much importance because of their interesting biological properties. Although a number of methods have been reported in the literature which includes oxidation with phosphorus oxychloride, lead tetraacetate, bromine, etc., hypervalent iodine reagents have emerged as reagents of choice for various synthetically useful transformations due to their low toxicity, ready availability and ease of handling.

Results

A series of new 3-(3-aryl-1-phenyl-1H-pyrazol-4-yl)-[1,2,4]triazolo[4,3-a]pyridines 4 has been conveniently synthesized by oxidative cyclization of 2-(3-aryl-1-phenyl-1H-pyrazol-4-yl)methylene)-1-(pyridin-2-yl)hydrazines 3 promoted with iodobenzene diacetate under mild conditions (up to 90% isolated yields). All the new compounds were tested in vitro for their antimicrobial activity.

Conclusions

Iodine(III)-mediated oxidative approach has offered an easy access to new 3-(3-aryl-1-phenyl-1H-pyrazol-4-yl)-[1,2,4]triazolo[4,3-a]pyridines 4. The antibacterial and antifungal activities of newly synthesized compounds have proved them potent antimicrobial agents.     

Synthesis and characterization of novel benzimidazole bearing pyrazoline derivatives as potential antimicrobial agents

A new series of compounds N-(4-(2-(3-(1H-benzo[d]imidazol-2-yl)-5-(aryl)-4,5-dihydro-1H-pyrazol-1-yl)-2-oxoethoxy)phenyl)acetamides (5a–u) were synthesized and structures of these compounds were elucidated by spectral (IR, ¹H NMR, ¹³C NMR, and mass spectra) analysis. Antimicrobial activity was measured against Escherichia coli (MTCC 443), Pseudomonas aeruginosa (MTCC 1688), Staphylococcus aureus (MTCC 96), Streptococcus pyogenes (MTCC 442), Candida albicans (MTCC 227), Aspergillus niger (MTCC 282), and Aspergillus clavatus (MTCC 1323) by serial broth dilution method. Evaluation of antimicrobial activity revealed that compounds 5f, 5i, 5q, and 5t were the most active antibacterial, while compounds 5e, 5g, 5h, 5j, 5p, 5r, and 5u were the most potent antifungal agents as compared to standard drugs and thus could be promising new lead molecules.     

Synthesis, characterization, anticancer, and antioxidant activity of some new thiazolidin-4-ones in MCF-7 cells

There are limited studies centring on the potential of thiazolidin-4-ones as anticancer agents. In this study, a new series of 2-(3-substituted-1H-pyrazol-4-yl)-3-(3-substituted-5-sulfanyl-1,2,4-triazol-4-yl)-1,3-thiazolidin-4-one (4a–o) have been synthesized by cyclo-condensation reaction of 5-substituted-4-[(3-substituted-1H-pyrazol-4-ylmethylidene)amino]-2H-1,2,4-triazole-3-thione (3a–o) and thioglycolic acid. The structures of all the synthesized compounds were confirmed by elemental analysis, spectral techniques like IR, ¹H NMR, and mass spectroscopy. Few compounds exhibited dose-dependent cytotoxic effect in MTT assay in human breast cancer (MCF-7) cells. Apoptotic degradation of DNA due to action of potent thiazolidin-4-ones was analysed by agarose gel electrophoresis and visualized by ethidium bromide staining (comet assay). A concentration-dependent increase in tail length and olive tail moment was observed when treated with thiazolidin-4-ones. In vitro antioxidant studies like DPPH and ABTS-free radical scavenging assays-indicated moderate activity of thiazolidin-4-ones.     

Synthesis and antimicrobial activity of coumarin pyrazole pyrimidine 2,4,6(1H,3H,5H)triones and thioxopyrimidine4,6(1H,5H)diones

A series of 5-((3-(2-oxo-2H-chromen-3-yl)-1-phenyl-1H-pyrazol-4-yl)methylene)pyrimidine-2,4,6(1H,3H,5H)-trione (4a–f) and dihydro-5-((3-(2-oxo-2H-chromen-3-yl)-1-phenyl-1H-pyrazol-4-yl)methylene)-2-thioxopyrimidine-4,6(1H,5H)-dione (5a–f) derivatives were synthesized by the condensation of 3-(2-oxo2H-chromen-3-yl)-1-phenyl-1H-pyrazole-4-carbaldehyde (3a–f) with barbituric acid and thiobarbituric acid in acetic acid under microwave irradiation method. The newly synthesized compounds were evaluated for their antibacterial activity against Bcillus subtilis, Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeoginosa, and Klebsiella pneumoniae. All the compounds were found to be moderately active against used microorganisms, whereas compounds (4d) and (4e) exhibited good antifungal activity against Aspergillus niger.     

Novel 4(3H)-quinazolinone analogs: synthesis and anticonvulsant activity

A new series of quinazoline analogs was designed, synthesized, and evaluated for their anticonvulsant activity. Compounds 6, 12, 21, 36, 37, and 38 showed 70–100 % protection against PTZ-induced seizures acting as GABA_A receptor agonists. Compound N-(3,4,5,6-tetrachloro-phthalimido)-2-[(3-phenyl-4-oxo-6-methyl-3H-quinazolin-2-yl)-thio]acetamide (12) representing the moderate active compounds and 2-[6-iodo-4-oxo-2-(thiophen-2-yl)-quinazolin-3(4H)-yl]-isoindoline-1,3-dione (38) representing the remarkably active compounds in this stud, showed ED₅₀ values of 457 and 251 mg/kg; TD₅₀ values of 562 and 447 mg/kg; PI values of 1.22 and 1.78, LD₅₀ values of 1,288 and 1,380 mg/kg, and TI values of 2.82 and 5.50, respectively. Compound 38 proved to be almost twofold more active than the standard drug sodium valproate.     

Cobalt mediated ring contraction reaction of lapachol and initial antibacterial evaluation of naphthoquinones derived from lapachol

The synthesis of 2-hydroxy-2-(3-methylbut-2-enyl)-2H-indene-1,3-dione 3, from lapachol which involves a ring contraction via the Hooker intermediate 1,2-dihydroxy-2-(3-methylbut-2-en-1-yl)-3-oxo-2,3-dihydro-1H-indene-1-carboxylic acid 2 is described. Different pyranonaphthoquinone derivatives, obtained in our previous synthetic work, were screened for antimycobacterial (Mycobacterium tuberculosis) activity and against resistant strains of Gram-positive (Bacillus cereus and Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The results indicated significant activity of all the tested samples against M. tuberculosis and only moderate activity against the Gram-positive and Gram-negative bacteria.     

Synthesis and characterization of new types of 2-(6-methoxy-2-naphthyl)propionamide derivatives as potential antibacterial and antifungal agents

A series of novel 2-(6-methoxy-2-naphthyl)propionamide derivatives have been efficiently synthesized in excellent yields via the reaction of naproxenoyl chloride with different amino compounds. Most of the synthesized compounds were screened in vitro for their antibacterial and antifungal activities. Most of the compounds showed significant antibacterial and antifungal activities, reaching, in certain cases, the same level of antimicrobial activity as the standard antibacterial agent Ampicilline and antifungal agent Flucanazole. N-(4-(N-arylsulfamoyl)phenyl)-2-(6-methoxynaphthalen-2-yl)propanamide (4a–c), 4-(4-fluorobenzylidene)-2-(1-(6-methoxynaphthalen-2-yl)ethyl)oxazol-5(4H)-one (10b), 2-(6-methoxynaphthalen-2-yl)-N-((5-thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)methyl)propanamide (12), and N-((4-amino-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)methyl)-2-(6-methoxynaphthalen-2-yl)propanamide (13) were found to be the most potent compounds against most of the tested strains. The antimicrobial activity was further supported by using MIC technique. Structure activity relationship studies revealed several matching pairs.     

Synthesis and characterization of flurbiprofen hydrazide derivatives as potential anti-HCV, anticancer and antimicrobial agents

A novel series of new flurbiprofen hydrazide derivatives 2-(2-fluorobiphenyl-4-yl)-N′-[(substituted phenyl/5-nitro-2-furyl)methylene]propanehydrazide (3a–k), 2-(2-fluorobiphenyl-4-yl)-N-(2-substituted-4-oxo-1,3-thiazolidine-3-yl)propanamide (4a–b, 4d–k), 2-[2-(2-fluorobiphenyl-4-yl) propanoyl]-N-substituted hydrazinecarbothioamide (5a–h) and 2-(2-fluorobiphenyl-4-yl)-N′-[(3-methyl-4-oxo-1,3-thiazolidin-2-ylidene]propanehydrazide (6a–b, 6e and 6g) has been synthesized in this study. All synthesized compounds were screened for antimicrobial activity against various bacterial and fungal strains. Additionally, compounds were evaluated for the ability to inhibit Hepatitis C virus NS5B polymerase. The most active 4-thiazolidinone compound was 4k (SGK119) with 67.0 % and thiosemicarbazide compound was 5d (SGK123) with 69.50 % inhibition at 200 μM against hepatitis C virus NS5B RNA polymerase. Anticancer activity of the selected compounds (3i, 3j, 3h, 4d, 4i and 6b) was determined at a single dose towards the full panel of 60 human cancer cell lines by the National Cancer Institute (NCI). 2-(2-Fluoro-4-biphenylyl)-N-[2-[4-(trifluoromethyl)phenyl]-4-oxo-1,3-thiazolidine-3-yl]propanamide 4d, containing thiazolidinone ring, demonstrated the most marked effect with 20.80 % growth percent on leukaemia cancer cell line SR at 10^?5 M. The results demonstrated that none of the compounds tested have anticandidal and antifungal activities, but two of them (4a and 4i) showed antibacterial inhibition against Micrococcus luteus, and Staphylococcus cohnii and Staphylococcus aureus, respectively.     

Synthesis, pharmacological activity evaluation and molecular modeling of new polynuclear heterocyclic compounds containing benzimidazole derivatives

Novel heterocyclic compounds containing benzimidazole derivatives were synthesized from 2-(1Hbenzimidazol-2-yl) acetonitrile (1) and arylhydrazononitrile derivative 2 was obtained via coupling of 1 with 4-methyl phenyldiazonium salt, which was then reacted with hydroxylamine hydrochloride to give amidooxime derivative 3. This product was cyclized into the corresponding oxadiazole derivative 4 upon reflux in acetic anhydride. Compound 4 was refluxed in DMF in the presence of triethylamine to give the corresponding 5-(1H-benzimidazol-2-yl)-2-p-tolyl-2H-1,2,3-triazol-4-amine 6. Treatment of compound 6 with ethyl chloroformate afforded 2,6-dihydro-2-(4-methylphenyl)-1,2,3-triazolo[4″,5″-4′,5′]pyrimido[1,6-a]benzimidazole-5(4H)-one (8). 1,2-bis(2-cyanomethyl-1H-benzimidazol-1-yl)ethane-1,2-dione (10) was synthesized via the condensation reaction of 2-(1H-benzimidazol-2-yl) acetonitrile (1) and diethyloxalate. The reactivity of compound 10 towards some diamine reagents was studied. The in vitro antimicrobial activity of the synthesized compounds was investigated against several pathogenic bacterial strains such as Escherichia coli O157, Salmonella typhimurium, E. coli O119, S. paratyphi, Pseudomonas aeruginosa, Staphylococcus aureus, Listeria monocytogenes and Bacillus cereus. The results of MIC revealed that compounds 12a–c showed the most effective antimicrobial activity against tested strains. On the other hand, compounds 12a, b exhibited high activity against rotavirus Wa strain while compounds 12b, c exhibited high activity against adenovirus type 7. In silico target prediction, docking and validation of the compounds 12a–c were performed. The dialkylglycine decarboxylase bacterial enzyme was predicted as a potential bacterial target receptor using pharmacophorebased correspondence with previous leads; giving the highest normalized scores and a high correlation docking score with mean inhibition concentrations. A novel binding mechanism was predicted after docking using the MOE software and its validation.     

Synthesis and biological evaluation of benzo[d]imidazolyl chromeno[2,3-d]pyrimidinones

A series of benzo[d]imidazolyl chromeno[2,3-d]pyrimidnones were described. The key intermediate 2-cyano-N-(2-mercapto-1H-benzo[d]imidazol-5-yl)acetamide (3) is obtained by reacting 5-amino-2-mercaptobenzimidazole (1) with ethyl cyanoacetate (2). Compound 3 on reaction with substituted salicylaldehydes afforded 2-imino-N-(2-mercapto-1H-benzo[d]imidazol-5-yl)-2H-chromene-3-carboxamides (5) in good yields. Compounds 5 on condensation with formalin furnished the title compounds viz., 3-(2-mercapto-1H-benzo[d]imidazol-5-yl)-2H-chromeno[2,3-d]pyrimidin-4(3H)-ones (7). All the synthesized compounds were screened for their anti-microbial and anti-oxidant activities.     

Novel approach for synthesis of potent antimicrobial hybrid molecules containing pyrimidine-based imidazole scaffolds

This report describes the novel approach for the synthesis and exploration of hybrid molecules containing pyrimidine-based imidazole scaffolds as potent antimicrobial agents. The targeted compounds N-(4-arylidene-2-mercapto-5-oxo-4,5-dihydro-1H-imidazol-1-yl)-6-methyl-2-oxo-4-phenyl-1,2,3,4-tetrahydropyrimidine-5-carboxamides (5a–l) were achieved by the Knoevenagel condensation of a key precursor (4) with different aldehydes in good yields having moderate to excellent antimicrobial activity. The structural identification of final products was carried out by known classical spectral techniques like IR, ¹H NMR, ¹³C NMR, and mass spectra. The obtained data indicated that the majority of the tested compounds exhibited good antibacterial activity over antifungal activity, particularly compounds 5j and 5b (having MIC values 12.5 μg/mL) showed a comparable effect to a standard antibacterial and antifungal agents.