Synthesis, NMR spectral studies and antimicrobial evaluation of some 2-(benzothiazol-2-yl)-1-(alkyl-2r,6c-diarylpiperidin-4-ylidine)hydrazine derivatives

Substituted 2-(benzothiazol-2-yl)-1-(alkyl-2,6-diarylpiperidin-4-ylidine)hydrazines 10–17 were synthesized by the condensation of different 2r,6c-diarylpiperidin-4-ones 1–8 with 2-hydrazinobenzothiazole 9. All the synthesized compounds were investigated in solution and in the solid state by IR, ¹H, ¹³C and 2D NMR spectral techniques. The structure–activity relationships were studied by the screening of the antimicrobial activity over a representative panel of bacterial and fungal strains using two-fold serial dilution method.     

A search of novel antimicrobial based on benzimidazole and 2-pyridone heterocycles

The increasing incidence of bacterial drug resistance imposes a new search on existing antimicrobial drugs leading to the development of new bioactive molecules. In continuation to this, the present article deals with the synthesis and antimicrobial activity of 1-(1-(1H-benzo[d]imidazol-2-yl)ethylideneamino)-6-(arylideneamino)-4-(2-hydroxyphenyl)-2-oxo-1,2-dihydropyridine-3,5-dicarbonitriles (4a–k). All newly synthesized compounds have been evaluated against two gram positive bacteria (Staphylococcus aureus, Streptococcus pyogenes), two gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa), and three fungi (Candida albicans, Aspergillus niger, Aspergillus clavatus) using serial broth dilution method. Compounds reported in the present article bearing chloro and hydroxy groups exhibit very good to excellent antimicrobial activity. All the newly synthesized compounds have been characterized by IR, ¹H NMR, ¹³C NMR, and mass spectra.     

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.     

QSAR modeling of synthesized 3-(1,3-benzothiazol-2-yl) 2-phenyl quinazolin-4(3H)-ones as potent antibacterial agents

Present communication elicits the designing and synthesis of 3-(1,3-benzothiazol-2-yl) 2-phenyl quinazolin-4(3H)-ones as potential antibacterial agents. A number of substituted 2-amino benzothiazoles, 2-amino-5-[(E)-phenyl diazenyl] benzoic acid, and 2-phenyl-4H benzo[d] [1,3] oxazin-4-one were synthesized as the precursor substrates. The compounds were synthesized in excellent yields and the structures were corroborated on the basis of IR, ¹H NMR, Mass, and elemental analysis data. These compounds were screened in vitro for their antibacterial activity against a representative panel of Gram positive and Gram negative bacteria and models were generated through quantitative structure–activity relationship (QSAR).The activity contributions due to structural and substituent effects were determined using sequential regression procedure. The antimicrobial assay data show that the synthesized compounds are found to manifest profound antimicrobial activity.     

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, antimicrobial activity, and molecular modeling of novel 4-(3-(4-benzylpiperazin-1-yl)propoxy)-7-methoxy-3-substituted phenyl-2H-chromen-2-one

A series of novel 4-(3-(4-benzylpiperazin-1-yl)propoxy)-7-methoxy-3-substituted phenyl-2H-chromen-2-one (7a–7j) were synthesized by the reductive amination of 7-methoxy-3-phenyl-4-(3-piperizin-1-yl-propaxy)chromen-2-one (6) with different substituted aromatic aldehydes by using sodium cyanoborohydride in methanol. The newly synthesized compounds were purified and their structures were characterized by IR, ¹H NMR, ¹³C NMR, and mass spectroscopy. The representative analogs were screened for in vitro antimicrobial activity. The compounds exhibited significant antibacterial and antifungal activity as that of standards. The data was further compared with structure-based investigations using docking studies with the crystal structure of oxidoreductase (1XDQ and 3QLS) protein organisms. The estimated score by genetic algorithm was found to have a good correlation with the experimental inhibitory potency of the derivatives.     

Zn(OTf)2-catalyzed three component, one-pot cyclocondensation reaction of some new octahydroquinazolinone derivatives and access their bio-potential

An efficient synthesis of some new octahydroquinazolinone derivatives 4a–x by the cyclocondensation reaction of corresponding 2-thi(oxo)-1,2-dihydroquinoline-3-carbaldehyde 1a–e, 1,3-dicarbonyl compounds 2a–b, and substituted urea 3a–c using zinc triflate as a catalyst in refluxing ethanol in high yield is described. The structures of new compounds have been characterized on the basis of elemental analysis, FT- IR, ¹H NMR, ¹³C NMR, and mass spectral data. All the synthesized compounds were evaluated for their antimicrobial activities against various microbes. Minimum inhibitory concentration values of all the 24 synthesized compounds were also determined. Some of the synthesized compounds exhibited excellent antimicrobial activity.     

Synthesis, characterization, solvatochromic properties, and antimicrobial evaluation of 5-acetyl-2-thioxo-dihydro-pyrimidine-4,6-dione-based chalcones

A new series of chalcone analogs namely 5-(3-phenyl-acryloyl)-2-thioxo-dihydro-pyrimidine-4,6-dione have been synthesized from the key intermediate 5-acetyl-2-thioxo-dihydro-pyrimidine-4,6-dione 4′ with different aldehyde derivatives were performed to get the target compounds as thiobarbituric acid-based chalcones 5(a′–k′) and they were obtained in excellent yields. The newly synthesized compounds were characterized by spectral analysis (FT-IR, ¹H NMR, ¹³C NMR, and UV spectroscopy) and elemental analysis. The synthesized compounds were evaluated for their antimicrobial activity against five bacterial strains (S. aureus, S. pyogenes, E. coli, K. pneumoniae, and P. aeruginosa) and four fungal strains (C. albicans, A. clavatus, T. rubrum, and Penicillium wild strain). Among the screened compounds, 5e′ and f′ showed comparable activity (minimum inhibitory concentration = 500 μg/mL) nearly to that of standard antibiotics griseofulvin.     

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.     

Synthesis of 3-{4-[4-dimethylamino-6-(4-methyl-2-oxo-2H-chromen-7-yloxy)-[1,3,5]triazin-2-ylamino]-phenyl}-2-phenyl-5-(4-pyridin-2-yl-piperazin-1-ylmethyl)-thiazolidin-4-one and their biological evaluation

A novel series of thiazolidinone derivatives namely 3-{4-[4-dimethylamino-6-(4-methyl-2-oxo-2H-chromen-7-yloxy)-[1,3,5]triazin-2-ylamino]-phenyl}-2-phenyl-5-(4-pyridin-2-yl-piperazin-1-ylmethyl)-thiazolidin-4-one have been synthesized from the intermediate 7-[4-(4-amino-phenylamino)-6-dimethylamino-[1,3,5]triazin-2-yloxy]-4-methyl-chromen-2-one (7). Condensation reaction of compound 7 with different aldehyde derivatives were performed to give Schiff base derivatives, which after cyclization gave thiazolidinones and they were incorporated with 1-pyridin-2-yl-piperazine to get target compounds. The newly synthesized compounds were evaluated for their antimicrobial activity against eight bacteria (S. aureus, B. cereus, E. coli, P. aeruginosa, K. pneumoniae, S. typhi, P. vulgaris, and S. flexneria) and four fungi (A. niger, C. albicans, A. fumigatus, and A. clavatus).     

New N-arylamino biquinoline derivatives: microwave-assisted synthesis and their antimicrobial activities

A new series of N-arylamino biquinoline derivatives 5a–x were synthesized under microwave irradiation technique in good yields compared with conventional method and screened for their antimicrobial activity. All the synthesized compounds have been established by elemental analysis, IR, ¹H NMR, ¹³C NMR and mass spectral data. In vitro antimicrobial activity was carried out against three Gram-positive bacteria (Bacillus subtilis, Clostridium tetani, Streptococcus pneumoniae), three Gram-negative bacteria (Escherichia coli, Salmonella typhi, Vibrio cholerae) and two fungal species (Aspergillus fumigatus, Candida albicans) using broth microdilution method. Of the compounds studied, compound 5u exhibited promising antimicrobial activity against Streptococcus pneumoniae and Salmonella typhi.     

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.     

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,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, characterization, and pharmacological evaluation of 1-[2-(6-nitro-4-oxo-2-phenyl-4H-quinazolin-3-yl)-ethyl]-3-phenyl ureas

In the present communication, a series based on 1-[2-(6-nitro-4-oxo-2-phenyl-4H-quinazolin-3-yl)-ethyl]-3-phenyl-urea have been synthesized by an efficient synthetic protocol. The synthesized compounds were characterized by IR, ¹H NMR, ¹³C NMR spectroscopy, ESI Mass spectrometry, and elemental analysis. The antibacterial and antifungal activity of the compounds were studied against selected strains (Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 11774, and Candida albicans ATCC 66027) by using Kirby Bauer disk diffusion technique and broth dilution technique. All the synthesized compounds showed good antifungal potency against strain C. albicans.     

Synthesis and biological evaluation of 1-(3-chloro-2-oxo-4-phenylazetidin-1-yl)-3-(2-oxo-2-(10H-phenothiazin-10-yl)ethyl)urea derivatives

A new series of eleven novel 1-(3-chloro-2-oxo-4-phenylazetidin-1yl)-3-(2-oxo-2-(10H-phenothiazin-10-yl)ethyl)urea derivatives were synthesized by cyclocondensation of various Schiff bases of phenothiazine with chloroacetyl chloride in the presence of triethylamine. Various Schiff bases of phenothiazine were synthesized by condensation of 4-(2-oxo-2-(10H-phenothiazin-10-yl)ethyl semicarbazide with various aryl aldehydes. The synthesized compounds were characterized by IR, MASS and ¹H NMR spectral data and evaluated for in vitro antimicrobial, antitubercular, antioxidant and anticancer activities by disc diffusion method, MIC method, REMA, DPPH, FRAP and MTT assay method, respectively. All synthesized compounds showed moderate-to-significant anti-bacterial and anti-fungal activity and compound 4d, 4g, 4h and 4k showed good antioxidant activity with EC₅₀ value of 55, 57, 56 and 47 μg/ml tested by DPPH method. The compounds 4j at a concentration of 10 μg/ml showed inhibition against the growth of Mycobacterium tuberculosis and 4f showed significant activity against human cervical cancer cell line with IC₅₀ values of 18.26 μM.     

The synthesis and investigation of the antimicrobial activity of some new phenylselanyl-1-(toluene-4-sulfonyl)-1H-tetrazole derivatives

The sulfonamide functional group has aroused interest in both medicinal and bioorganic chemistry. In this study, some new phenylselanyl–1–(toluene-4-sulfonyl)-1H-tetrazole derivatives (2a–f) have been synthesized using dicyclohexylcarbodiimide/dimethylaminopyridine (DCC/DMAP). The structures of the presently synthesized compounds were elucidated by spectroscopic methods [Fourier-transform infrared (FTIR) spectroscopy, ¹H nuclear magnetic resonance (NMR), ¹³C nuclear magnetic resonance-attached proton test (¹³C NMR-APT), and mass spectrometry (MS)]. In addition, the antimicrobial activity of the synthesized compounds and two antibiotics [sulfamethoxazole (SMX) and sulfamerazine (SRZ)] were investigated against some microorganisms.     

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 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 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.