Synthesis,antimicrobial and cytotoxic activity of 2-azetidinone derivatives of pyridyl benzimidazoles

In the present study, a series of novel 6-(1H-benzo[d]imidazol-2-yl)-2-(3-chloro-2-oxo-4-phenylazetidin-1-yl)-4-(aryl)nicotinonitriles 6a–o were efficiently synthesized and evaluated for their in vitro antibacterial activity against Gram-positive (Staphylococcus aureus and Streptococcus pyogenes), Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria and fungal (Candida albicans, Aspergillus niger and Aspergillus clavatus) strains. The results of antimicrobial study revealed that compounds 6b, 6c, 6d, 6h and 6i exhibited substantial antibacterial activity while compounds 6c and 6h emerged as the most potent antifungal agents compared to the standard drugs chloramphenicol and ketoconazole, respectively. From the standpoint of SAR studies, it was observed that the presence of electron-withdrawing groups remarkably enhances the antibacterial activity of newly synthesized compounds. Further, the results of preliminary MTT cytotoxicity studies on HeLa cells suggested that potent antimicrobial activity of 6b, 6c, 6d, 6h and 6i is accompanied by low level of cytotoxic concentrations. All the newly synthesized analogues were characterized by IR, ¹H NMR, ¹³C NMR and mass spectral data.     

Synthesis of promising antimicrobial agents: a novel series of N-(4-(2,6-dichloroquinolin-3-yl)-6-(aryl)pyrimidin-2-yl)-2-morpholinoacetamides

A series of novel compounds N-(4-(2,6-dichloroquinolin-3-yl)-6-(aryl)pyrimidin-2-yl)-2-morpholinoacetamides (5a–l) were synthesized by a series of multistep reactions. Newly synthesized compounds have been characterized by IR, ¹H NMR, ¹³C NMR, and mass spectral data. Antimicrobial screening of title compounds 5a–l was examined against Gram-positive bacteria (Staphylococcus aureus and Streptococcus pyogenes), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and three fungi (Candida albicans, Aspergillus niger, and Aspergillus clavatus) by serial broth dilution method. Synthesized compounds showed potent inhibitory action against test organisms. Screened compounds 5e–g and 5i–l were associated with considerably higher antibacterial and antifungal activities than commercially used antibiotics.     

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 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 and antimicrobial screening of novel series of imidazo-[1,2-a]pyridine derivatives

In an attempt to find new bio-active molecules, a series of mannich bases N,N-dimethyl-1-(7-methyl-2-(aryl)imidazo[1,2-a]pyridin-3-yl)methanamines 4a–l were synthesized by mannich reaction of 7-methyl-2-(aryl)imidazo-[1,2-a]pyridines 3a–l with paraformaldehyde and N,N-dimethyl amine. Compounds 3a–l were prepared from reaction between different substituted 2-bromo-1-(aryl)ethanones 2a–l and 4-methylpyridin-2-amine 1. Structures of these compounds were confirmed by IR, ¹H NMR, ¹³C NMR, and mass spectral data. Antimicrobial screening of title compounds 3a–l was examined against Gram-positive bacteria (Staphylococcus aureus, Streptococcus pyogenes), Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa), and fungi (Candida albicans, Aspergillus niger, Aspergillus clavatus) using serial broth dilution method. Some derivatives bearing halogen group was found to be equipotent or more potent than commercial drugs, against most of the employed strains, as evident from the screening data.     

A clubbed quinazolinone and 4-thiazolidinone as potential antimicrobial agents

A series of N-{5-[(2-chlorophenyl)methylene]-2-(4-hydroxyphenyl]-4-oxo(1,3-thiazolidin-3-yl)}{4-[2-(4-methylphenyl)-4-oxo(3-hydroquinazolin-3-yl)]phenyl}carboxamides (6a–n) have been synthesized. All the synthesized compounds were screened for in vitro antibacterial and antifungal activities on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus pyogenes, Candida albicans, Aspergillus niger, and Aspergillus clavatus. The structures of the compounds were elucidated by IR, ¹H NMR, ¹³C NMR, and Mass spectra.     

Dimeric 2-(2-chlorophenyl)-quinazolin-4-ones as potential antimicrobial agents

3-(Aryl)-2-(2-chlorophenyl)-6-{2-[2-(2-chlorophenyl)-4-oxo(3-hydroquinazolin-3yl)]ethyl}-3-hydroquinazolin-4-ones had been selected as target bio-active molecules. Several quinazoline derivatives were prepared by using anthranilic acid, acid chloride, 2-amino-ethanol, and different amines. Newly synthesized compounds were screened for their antibacterial and antifungal activities on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Staphylococcus pyogenes, Candida albicans, Aspergillus niger, and Aspergillus clavatus. The compounds 5e, 5g, and 5h are shown to have excellent activity, while 5c, 5d, 5i, 5k, 5l are shown to have very good activity against several strains of bacteria. The structures of the synthesized compounds were firmly established by well-defined spectral analysis techniques like IR, ¹H-NMR, ¹³C-NMR, and Mass spectra.     

Solvent- and catalyst-free synthesis of bis-adducts of 3-formylchromone as potential antimicrobial agents

A facile and ecofriendly synthesis of new (chromon-3-yl)bis(heteroaryl)methanes 5a–d, from 3-formylchromone 1 and active methylene compounds 2–4 is reported under solvent-free, catalyst-free thermal heating condition in good yields. The synthesized compounds were characterized on the basis of elemental and spectral (IR, ¹H NMR, and mass spectrometry) analysis. All the target compounds were evaluated for their in vitro antimicrobial activity against Streptococcus pyogenes, Methicillin resistant Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli bacterial strains, and fungal cultures of Candida albicans, Aspergillus fumigatus, Trichophyton mentagrophytes, and Penicillium marneffei by disk diffusion assay with slight modifications. The minimum inhibitory concentration was determined for the test compounds as well as for reference standards. Among the tested compounds, 5b has shown the most potent antibacterial as well as antifungal activities.     

Antimicrobial and antiquorum-sensing studies. Part 2: synthesis, antimicrobial, antiquorum-sensing and cytotoxic activities of new series of fused [1,3,4]thiadiazole and [1,3]benzothiazole derivatives

New series of [1,3,4]thiadiazolo[3,2-a]pyrimidines, [1,3,4]thiadiazolo[2,3-b]quinazolines, and pyrimido[2,1-b][1,3]benzothiazoles have been synthesized and characterized by analytical and spectrometrical methods (IR, MS, ¹H, and ¹³C NMR). Sixteen of the synthesized compounds; namely, 3a, b, 5a–f, 8a, b, 10, 11a–c, and 13a, b were screened for antibacterial activity against Escherichia coli, Staphylococcus aureus, and Bacillus cereus. They were found to be either moderately active, slightly active or inactive against the selected microorganisms. The antifungal activity of these compounds were also tested against Candida albicans, Aspergillus fumigatus 293, and Aspergillus flavus 3375. Compound 11a showed potent antifungal activity against the three selected fungi; the rest of the tested compounds displayed either weaker activity or were completely inactive. The same compounds were examined for antiquorum-sensing activity against Chromobacterium violaceum ATCC 12472, where compounds 3a, 10, 11a, and 13a, b exhibited promising activity. The in vitro cytotoxic activity of these compounds was also studied by brine shrimp lethality bioassay, and results indicated that compounds 3a, 11a, and 13a have the highest cytotoxic activity.     

Synthesis of some new 3,5-diamino-4-(4′-fluorophenylazo)-1-aryl/heteroarylpyrazoles as antimicrobial agents

Synthesis of some new 3,5-diamino-4-(4′-fluorophenylazo)-1-aryl/heteroarylpyrazoles (5a–5i) was achieved by the treatment of aryl/heteroarylhydrazines 4a–4i with 2-[(4-fluorophenyl)hydrazono]malononitrile 3 in refluxing ethanol. The structure of the compounds was established on the basis of IR, NMR (¹H and ¹³C) and mass spectral studies. All the nine synthesized compounds were screened for their in vitro antimicrobial activity against two Gram-positive (Staphylococcus aureus, Bacillus subtilis), two Gram-negative bacteria (Escherichia coli, Klebesiella aerogenes) and three pathogenic fungi (Aspergillus niger, Candida albicans, and Saccharomyces cerevisiae).     

Synthesis, stereochemistry, and antimicrobial evaluation of t(3)-isopropyl-r(2), c(6)-di-2′-furanylpiperidin- 4-one and its derivatives

In a wide search program for new and efficient antimicrobial agents, a series of t(3)-isopropyl-r(2),r(6)-di-2′-furanylpiperidin-4-one 1 and its derivatives 2–7 were synthesized; characterized by IR, ¹H NMR, ¹H-¹H COSY, ¹³C NMR, and mass and elemental analysis; and their antibacterial activity against Streptococcus faecalis, Bacillus subtilis, Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa and antifungal activity against Candida-6, Candida albicans, Aspergillus niger, Candida-51 and Aspergillus flavus was evaluated. Compound 6 exerted potent in vitro antibacterial activity against B. subtilis while compound 6 exhibited in vitro antifungal activity against Candida-6.     

Synthesis and antimicrobial screening of 5-(benzylidene)-3-phenylthiazolidin-4-one derivatives incorporating thiazole ring

The present article deals with the synthesis and antimicrobial screening of a series of N-(5-(2-(5-(arylidene)-4-oxo-3-phenylthiazolidin-2-ylidene)hydrazinecarbonyl)-4-methylthiazol-2-yl)-4-methoxybenzamides (6a–o). The structures of these compounds have been elucidated by spectra (IR, ¹H NMR, ¹³C NMR, mass spectra). All the synthesized compounds were screened for in vitro antibacterial activity against Gram-positive (Staphylococcus aureus, Streptococcus pyogenes) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria. These compounds were also tested for their inhibitory action against three strains of fungi (Candida albicans, Aspergillus niger, Aspergillus clavatus). The thiazole derivatives discovered in this study may provide valuable therapeutic intervention for the treatment of microbial diseases, especially against bacterial and fungal infections.     

Novel indolyl-pyrimidine derivatives: synthesis,antimicrobial, and antioxidant evaluations

In the present study, a novel series of indolyl-pyrimidines (1–13) were synthesized starting from 4-hydrazinopyrimidine-5-carbonitrile 3. Elemental analysis, IR, ¹H-NMR, ¹³C-NMR, and mass spectral data elucidated structure of newly synthesized compounds. All compounds were screened for their in vitro antibacterial, antifungal, and some for antioxidant activities. Compounds 5, 9g, 9i, and 9j showed pronounced antimicrobial activity against Staphylococcus aureus, Bacillus cereus, Escherichia coli, Candida albicans, and Aspergillus flavus compared to the reference drugs, while compounds 3 and 9g displayed promising free radical scavenging activity and found to be more potent than standard, ascorbic acid (vitamin C). Further, some compounds were evaluated for cytotoxic activity by SRB assay method against human colon carcinoma (CaCo-2) and showed that compounds 4 and 9g were found to be the highly active compared to the reference drug doxorubicin. Their structure and activity relationship were discussed.     

Synthesis,antimicrobial, and cytotoxic activities of novel benzimidazole derivatives bearing cyanopyridine and 4-thiazolidinone motifs

A series of 6-(1H-benzo[d]imidazol-2-yl)-2-(2-(3-nitrophenyl)-4-oxothiazolidin-yl)-4-(aryl)nicotinonitriles 5a–l were synthesized and characterized by IR, ¹H NMR, ¹³C NMR, and mass spectrometry techniques. These novel compounds 5a–l were screened for their in vitro antimicrobial activity against different bacterial and fungal strains and in vitro cytotoxicity study (HeLa cell line) using MTT colorimetric assay. The results demonstrated that compounds 5c, 5e, and 5i–k exhibited excellent antibacterial activity, while compounds 5d, 5i, and 5k were found to be the most potent antifungal agents. From the standpoint of SAR studies, it was observed that the presence of electron donating groups remarkably enhanced the antimicrobial activity of newly synthesized compounds. Further, the results of preliminary MTT cytotoxicity studies on HeLa cells suggested that potent antimicrobial activity of 5c–e and 5i–k was accompanied by low cytotoxicity.     

Synthesis, characterization and biological activity of some new carbostyril bearing 1H-pyrazole moiety

In this study, 16 new 4-pyrazolyl-N-arylquinoline-2,5-dione 4 have been synthesized by the multicomponent reaction of pyrazole-4-carbaldehyde 1, Meldrum’s acid 2 and 3-aryl-5,5-disubstitutedcyclohex-2-enone 3. The structures of compounds 4 were established by the combined use of ¹H NMR, ¹³C NMR, FT-IR and mass spectra. All the 16 compounds were tested in vitro for their bacterial and fungal activity against a list of human pathogens, namely, Bacillus subtilis, Clostridium tetani, Streptococcus pneumoniae, Salmonella typhi, Vibrio cholerae, Escherichia coli, Aspergillus fumigatus and Candida albicans, using broth microdilution MIC (minimum inhibitory concentration) method. Some of the compounds were found to be the most effective analogs against the tested bacterial and fungal strains.     

Synthesis, antioxidant, and antibacterial studies of phenolic esters and amides of 2-(1-benzofuran-2-yl) quinoline-4-carboxylic acid

A new series of phenolic esters 2(a–j) and amides 3(a–c) of 2-(1-benzofuran-2-yl) quinoline-4-carboxylic acid were synthesized by the reaction of 2-(1-benzofuran-2-yl)-quinoline-4-carboxylic acid (1) with various substituted phenols and secondary amines using ethyl-(N′,N′-dimethylamino)propyl carbodiimide hydrochloride (EDC.HCl) as a coupling agent. The newly synthesized compounds were evaluated for in vitro antioxidant and antibacterial activity. Among all tested compounds 2a, 2c, 2e, and 2h showed good chelating ability with Fe⁺² ions, whereas compounds 2g and 2j exhibited good scavenging activity with DPPH free radicals. Concerning antibacterial activities compounds 2a, 2b, 2c, and 2h were found to be equipotent to ampicillin against Enterococcus sp and Staphylococcus aureus, while compound 2e is found to be as potent as ampicillin against Pantoea Dispersa and Ochrobactrum sp. amide derivatives 3(a–c) were found to be less potent when compared to standard.     

Discovery of 2-(4-cyano-3-trifluoromethylphenyl amino)-4-(4-quinazolinyloxy)-6-piperazinyl(piperidinyl)-s-triazines as potential antibacterial agents

A series of 2-(4-cyano-3-trifluoromethylphenyl amino)-4-(4-quinazolinyloxy)-6-piperazinyl(piperidinyl)-s-triazines have been synthesized in this study by a simple and efficient synthetic protocol. The synthetic route to final piperazinyl s-triazines involved two nucleophilic substitution reactions of 4-amino-2-trifluoromethyl-benzonitrile and 4-hydroxyquinazoline with 2,4,6-trichloro-1,3,5-triazine resulting in 2,4-disubstituted-6-chloro-1,3,5-triazine derivative to introduce the piperazinyl or piperidinyl functionality. The structures of the compounds were elucidated with the aid of IR, ¹H NMR, ¹³C NMR, ¹⁹F NMR spectroscopy, and elemental analysis. The antimicrobial activity of the compounds was tested against eight bacteria (Staphylococcus aureus MTCC 96, Bacillus cereus MTCC 619, Escherichia coli MTCC 739, Pseudomonas aeruginosa MTCC 741, Klebsiella pneumoniae MTCC 109, Salmonella typhi MTCC 733, Proteus vulgaris MTCC 1771, Shigella Flexneria MTCC 1457) and four fungi (Aspergillus niger MTCC 282, Aspergillus fumigatus MTCC 343, Aspergillus clavatus MTCC 1323, and Candida albicans MTCC 183). The title compounds were also investigated for their antituberculosis activity against MTB H37 R_V strain using BACTEC MGIT and L. J. agar dilution method. The bioassay results showed that compounds 5d, 5n, 5p, 5s, and 5t demonstrated 99% inhibition at the MIC of 6.25?μg/ml, equivalent to standard drug pyrazinamide.     

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.     

Synthesis, physicochemical properties, antimicrobial and antioxidant studies of pyrazoline derivatives bearing a pyridyl moiety

A series of new pyrazoline compounds bearing a pyridyl moiety (4a–i) were synthesized by condensing appropriate chalcones with hydrazine hydrate and tested for antimicrobial and antioxidant activities. According to in vitro antimicrobial activity against Bacillus subtilis, Staphylococcus epidermidis, Proteus vulgaris, Pseudomonas aeruginosa, Aspergillus niger and Penicillium chrysogenum and antioxidant activity by DPPH method, the compounds 4a, 4d, 4i and 4e, 4f, 4h showed maximum antimicrobial and antioxidant activities, respectively. Physiochemical properties and Lipinski’s ‘Rule of Five’ analysis predicted higher intrinsic quality of the synthesized compounds and revealed that these compounds have good bioavailability and druglikeness properties.     

Synthesis, characterization and antimicrobial activity of novel ethyl 1-(N-substituted)-5-phenyl-1H-pyrazole-4-carboxylate derivatives

In the present study, a novel series of Pyrazole derivatives (3a–m) were synthesized by condensing ethyl-3-(dimethylamino)-2-(phenylcarbonyl)prop-2-enoate with different aromatic and aliphatic hydrazines. These newly synthesized compounds were characterized by NMR, mass spectral, IR spectral studies as well as by C, H, and N analyses. All the newly synthesized compounds were screened for their antibacterial properties against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa. Among the screened samples, 3c, 3f, 3k, and 3l have showed excellent antibacterial activity against all the tested bacterial strains as compared to the standard drug Ceftriaxone. Few of the compounds were found to be biologically potent. Molecular structure of compound 3i was confirmed by single crystal X-ray analysis.