Synthesis of novel 3-(5-sulfanyl-1,3,4-oxadiazol-2-yl)-2H-chromen-2-one condensed s-triazinyl piperazines and piperidines as antimicrobial agents

Synthesis and antimicrobial activity of a new series of 3-(5-sulfanyl-1,3,4-oxadiazol-2-yl)-2H-chromen-2-ones based on various substituted piperazines and piperidines incorporating a 1,3,5-triazine moiety are reported in this article. 3-{5-[(4,6-dichloro-1,3,5-triazin-2-yl)sulfanyl]-1,3,4-oxadiazol-2-yl}-2H-chromen-2-one 3 was obtained by the reaction of 2,4,6-trichloro-1,3,5-triazine 1 with 3-(5-sulfanyl-1,3,4-oxadiazol-2-yl)-2H-chromen-2-one 2 which was obtained by following the method reported in the literature. Intermediate 3 was then condensed with 8-hydroxyquinoline 4 to form 3-(5-{[4-chloro-6-(quinolin-4-yloxy)-1,3,5-triazin-2-yl]sulfanyl}-1,3,4-oxadiazol-2-yl)-2H-chromen-2-one 5. This was further treated with various substituted piperazines and piperidines to obtain the title compounds 7a–u, which were then subjected to determine their in vitro biological efficacy against bacterial and fungal strains as two Gram-positive bacteria (S. aureus, B. cereus), six Gram-negative bacteria (E. coli, P. aeruginosa, K. pneumoniae, S. typhi, P. vulgaris, and S. flexneria) and two fungal species (A. niger, and C. albicans) with an intent to develop novel class of antimicrobial agents. The results indicate that some of the novel s-triazines have noteworthy activity in MIC (μg/ml) and zone of inhibition (mm) indicating potential leads for further drug discovery study. All the final compounds were structurally elucidated on the basis of IR, ¹H NMR, ¹³C NMR, ¹⁹F NMR spectroscopy, and elemental analysis.     

Synthesis and antimicrobial evaluation of 1,3,4-oxadiazole-based chalcone derivatives

A series of chalcones-bearing 1,3,4-oxadiazole derivatives was synthesized as novel bio-active antimicrobial agents against multidrug-resistant bacteria and fungi. The lead compounds (Z)-2-(5-(3-nitrophenyl)-1,3,4-oxadiazol-2-ylthio)-N-(4-(3-(aryl)acryloyl)phenyl)acetamides 5a–n were synthesized via acid-catalyzed aldol condensation (SOCl₂) by reacting N-(4-acetylphenyl)-2-(5-(3-nitrophenyl)-1,3,4-oxadiazol-2-ylthio)acetamide (4) with differently substituted aldehydes. Compound (4) was obtained by reacting 5-(3-nitrophenyl)-1,3,4-oxadiazole-2-thiol (2) with N-(4-acetylphenyl)-2-chloroacetamide (3) in the presence of K₂CO₃. The intermediates (2) and (3) were synthesized simultaneously from 3-nitrobenzohydrazide (1) and 4-aminoacetophenone, respectively. The formation of intermediates and targeted compounds were confirmed for their structure by means of various spectral–analytical techniques like IR, ¹H NMR, ¹³C NMR, elemental analysis, and mass spectra. Antimicrobial properties of all the synthesized compounds have been evaluated against broad panel of bacteria and fungi.     

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 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, evaluation of antimicrobial activity, and molecular modeling of novel 2-((4-(2H-benzo[d] [1,2,3] triazol-2-yl)piperidin-1-yl)methyl)-5-substituted phenyl-1,3,4-oxadiazoles

A new series of 2-((4-(2H-benzo[d][1,2,3]triazol-2-yl)piperidin-1-yl)methyl)-5-substituted-1-yl)-acetic acid hydrazide (3) with various substituted aromatic carboxylic acids phenyl-1,3,4-oxadiazoles (4a–j) were synthesized by cyclization of 4-benzotriazol-2-yl-piperidin in the presence of POCl₃. The structures were characterized by spectral data. The representative examples were screened invitro antibacterial activity and antifungal activity. The compounds showed significant antibacterial activity and showed moderate antifungal activity as that of standards, respectively. The data were further compared with structure-based investigations using docking studies with the crystal structure of oxidoreductase (1XDQ) protein organism: Escherichia coli for antibacterial activity and oxidoreductase (3QLS) protein, organism: Candida albicans for antifungal activity. The score values estimated by genetic algorithm were found to have a good correlation with the experimental inhibitory potencies.     

Synthesis and pharmacological evaluation of novel 4-isopropylthiazole-4-phenyl-1,2,4-triazole derivatives as potential antimicrobial and antitubercular agents

A series of novel 4-isopropylthiazol-4-phenyl-1,2,4-triazol derivatives, N′-(substituted benzylidene)-2-(5-(4-isopropylthiazol-2-yl)-4-phenyl-4H-1,2,4-triazol-3-ylthio)acetohydrazides 4a–e, 4-isopropylthiazol-2-yl-4′-phenyl-4′H-1′, 2′,4′-triazol-3′-ylthio (substituted methyl benzylidene) acetohydrazides 5a–f, 3-(4-isopropylthiazol-2-yl)-4-phenyl-5-(5-substituted-1,3,4-oxadiazol-2-ylthio)-4H-1,2,4-triazole derivatives 6a–f and N-acetyl-5′-(4-isopropylthiazol-2-yl)-4′-phenyl-4′H-1,2,4-triazol-3′-ylthio) acetohydrazide 7 were synthesized and characterized by spectroscopy, elemental, and mass spectral analysis. These compounds were evaluated for their preliminary in vitro antibacterial, antifungal, and antitubercular activity against Mycobacterium tuberculosis (M. tuberculosis) H37Rv strain by broth dilution assay method. All the compounds exhibited moderate to significant antibacterial and antifungal activities. Results of the antitubercular screening against Mycobacterium tuberculosis H37Rv showed that compounds 4c and 6c exhibited good antitubercular activity when compared with first line drug isoniazid.     

Mannich base derivatives of 1,3,4-oxadiazole: synthesis and screening against Entamoeba histolytica

Mannich base derivatives of 5-(pyridine-4-yl)-1,3,4-oxadiazole-2-(3H)-thione with substituted piperazine were synthesized and characterized. In vitro antiamoebic activity was performed against HM1: IMSS strain of Entamoeba histolytica and the cytotoxicity of the compounds having IC₅₀ value less than metronidazole was assessed by MTT assay on human breast cancer MCF-7 cell line. The results revealed that compounds 2, 3 and 5 were found to be better inhibitors of E. histolytica than the reference drug metronidazole and found low cytotoxic in the concentration range of 2.5–250 μM. This study suggests the possibility of developing 1,3,4-oxadiazole analogues as potential drug candidates.     

Microwave-assisted synthesis and antimicrobial screening of new imidazole derivatives bearing 4-thiazolidinone nucleus

A new series of compounds 2-((1-(4-(4-arylidene-2-methyl-5-oxo-4,5-dihydro-1H-imidazol-1-yl)phenyl)ethylidene)hydrazono)thiazolidin-4-ones (4a–o) have been synthesized under conventional and microwave irradiation method. All compounds were characterized by IR, ¹H NMR, ¹³C NMR and mass spectra. 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 by bioassays, namely serial broth dilution. The synthesized compounds showed potent antimicrobial activity against tested microorganisms. Compounds 4h, 4j, 4m and 4n were the most potent amongst tested compounds.     

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.     

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 antimicrobial evaluation of novel urea derivatives from chromene based oxadiazole amines

A series of novel aryl ureides were synthesized based on oxadiazoles and different substituted aromatic amines. The intermediate amine, (3-(2H-chromen-3-yl)-1,2,4-oxadiazol-5-yl)methanamines (6a) was reacted with aromatic amines in presence of triphosgene to obtain the urea derivatives 7a–d and 7e–i in high yields. The structures of all the intermediates and the final urea derivatives were established by IR, NMR and mass spectrometry data. The antibacterial activity of synthesized compounds was evaluated against two gram-negative bacteria namely Escherichia coli and Pseudomonas aeroginosa and it was observed that the urea derivatives 7a and 7i were promising antibacterial agents.     

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.     

An efficient synthesis,characterization, and antimicrobial screening of tetrahydropyrimidine derivatives

Several new substituted 1,2,3,4-tetrahydropyrimidine derivatives 2a–h have been synthesized by the modified Biginelli and Hantzsch reactions and compounds were characterized by spectral techniques. All compounds were evaluated for their in vitro antimicrobial activity against different strains of Gram-negative (E. coli and P. aeruginosa) and Gram-positive (S. aureus and S. pyogenus) bacteria and selected fungi C. albicans, A. niger, and A. clavatus using serial Broth dilution method (Mueller–Hinton broth dilution method). Compound 2e was found active against both Gram-negative and -positive bacterial strains used for present study, while compound 2b was good active against Gram-negative and S. pyogenus bacterial strains. Compounds 2a–h were not that much significant against (C. albicans, A. niger, and A. clavatus) selected fungal strains.     

Synthesis of new oxadiazole derivatives as anti-inflammatory, analgesic, and antimicrobial agents

In search of pharmalogically active molecules in the class of oxadiazoles, the present article deals with the synthesis of 5-(5′-fluoro-2′-methoxybiphenyl-3-yl)-1,3,4-oxadiazol-2(3H)-one 2 from its hydrazide analog 1. The compound 2 was regioselectively N-alkylated with alkyl halides and produced the compounds 3a–f. Compound 3f was further functionalized with substituted benzenesulfonyl chlorides to give compounds 3g–j. The synthesized compounds were characterized by elemental and spectral analysis. Newly synthesized compounds were tested for their in vivo anti-inflammatory, analgesic, and in vitro antimicrobial activities. The compounds 3a–c were found to have promising anti-inflammatory and analgesic activities. Compounds 3b, 3f, and 3g showed significant antibacterial and antifungal activities.     

Synthesis, antimycobacterial, antiviral, antimicrobial activities, and QSAR studies of isonicotinic acid-1-(substituted phenyl)-ethylidene/cycloheptylidene hydrazides

A series of isonicotinic acid-1-(substituted phenyl)-ethylidene/cycloheptylidene hydrazide derivatives (1–12) was tested for their, in vitro antimycobacterial activity against Mycobacterium tuberculosis, and compound 2 was found to be more active than isoniazid. The antiviral screening results indicated that none of the tested compounds was active against a broad variety of DNA and RNA viruses at subtoxic concentrations, except compounds 8 and 10 that proved to be active against DNA viruses at concentrations close to their cytostatic potential. The synthesized compounds were also screened for their antimicrobial potential against S. aureus, B. subtilis, E. coli, C. albicans and A. niger, and the results indicated that compounds having Br, OCH₃ and Cl groups were highly active. The multi-target QSAR models indicated the importance of lipophilic (log P) and topological parameters (³χ^v) in describing the antimicrobial activity.     

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.     

Microwave-assisted synthesis of some hybrid molecules containing penicillanic acid or cephalosporanic acid moieties and investigation of their biological activities

Ethyl 4-amino-2-fluorophenylpiperazin-1-carboxylates containing a 1,3-oxazol(idin)e, 5-thioxo-1,2,4-triazole, 1,3,4-thiadiazole, 5-thioxo-1,3,4-oxadiazole, or 1,3-thiazole nucleus were obtained starting from ethyl piperazine-1-carboxylate (1) by several steps. The treatment of amine, 3 or hydrazide, 9 with several aromatic aldehydes generated the corresponding arylmethyleneamino (3a–f) or arylidenehydrazino (12a–c) compounds. The Mannich reaction between the 1,2,4-triazole or 1,3,4-oxadiazole compounds and 7-aca produced cephalosporanic acid derivatives. Penicillanic acid derivatives were obtained when 6-apa was used in the Mannich reactions. The synthesized compounds were screened for their antimicrobial, antilipase, and antiurease activities. Some of them were found to possess good-moderate antimicrobial activity against the test microorganisms. Two compounds exhibited antiurease activity, and four of them displayed antilipase activity.