Navin B. Patel

Pharmacological evaluation and characterizations of newly synthesized 1,2,4-triazoles

The triazole analogs were obtained via. multistep synthesis sequence beginning with ethyl nicotinoate 3 which on treatment with hydrazine hydrate yields nicotinoyl hydrazide 4. Intermolecular cyclisation of 4 with 4-methylbenzoic acid in presence of phosphorous oxy chloride affords 2-(3-pyridyl)-5-(4-methylphenyl)-1,3,4-oxadiazole 5. Condensation of 5 with various substituted 2-hydrazino benzothiazole 2a-j results in 3-(3-pyridyl)-5-(4-methylphenyl)-4-(N-substituted-1,3-benzothiazol-2-amino)-4H-1,2,4-triazole 6a-j analogs. All the compounds have been characterized by elemental analysis, IR, (1)H NMR, (13)C NMR and mass spectral data. In vitro antitubercular activity was carried out against Mycobacterium tuberculosis H(37)Rv strain using Lowenstein-Jensen medium and antimicrobial activity against various bacteria and fungi using broth microdilution method. Compounds 2e, 6a, 6b, 6c, 6d, 6g, 6h and 6i emerged as promising antimicrobials. It was also observed that the promising antimicrobials have proved to be better antituberculars. Compound 6j showed better antitubercular activity compared to rifampicin.

Synthesis and Antimicrobial Activity of 3-(1,3,4-Oxadiazol-2-yl)quinazolin-4(3H)-ones

In attempt to find new pharmacologically active molecules, we report here the synthesis and in vitro antimicrobial activity of various 3-(1,3,4-oxadiazol-2-yl)-quinazolin-4(3H)-ones. The antimicrobial activity of title compounds were examined against two gram positive bacteria (S. aureus, S. pyogenes), two gram negative bacteria (E. coli, P. aeruginosa) and three fungi (C. albicans, A. niger, A. clavatus) using the broth microdilution method. Some derivatives bearing a bromo or iodo group exhibited very good antimicrobial activity.

Synthesis and antimicrobial activity of new pyridine derivatives-I

Abstract2-Amino substituted benzothiazoles 2a–l and 2-chloropyridine-3-carboxylic acid 3 were used to prepare 2-[N-(substitutedbenzothiazolyl)amino]pyridine-3-carboxylic acids (4a–l) in 2-ethoxy ethanol. Acid chlorides (5a–l) were condensed with 2-hydroxyethyl piperazine (6) and 2,3-dichloropiperazine (7) to prepare amide derivatives 2-[N-(substituted benzothiazolyl)amino]pyridin-3-yl(4-(2-hydroxyethyl)piperazin-1-yl)methanones (8a–l) and 2-[N-(substituted benzothiazolyl) amino]pyridin-3-yl(2,3-dichloropiperazine-1-yl)methanones (9a–l), respectively. The structures of new compounds have been established on the basis of elemental analysis and spectral (IR, 1H NMR, and Mass spectra) studies. The in vitro antimicrobial activity was screened for all the synthesized compounds. Variable and modest activity were observed against the investigated strains of bacteria and fungi.

Synthesis and biological evaluation of some thiazolidinones as antimicrobial agents.

A novel series of thiazolidinone derivatives namely 4-(4-dimethylamino-6-{4-[5-(4-ethylpiperazin-1-ylmethyl)-4-oxo-2-phenylthiazolidin-3-yl]-phenylamino}-[1,3,5]triazin-2-yloxy)-1-methyl-1H-quinolin-2-one have been synthesized from the key intermediate 4-[4-(4-aminophenylamino)-6-dimethylamino-[1,3,5]triazin-2-yloxy]-1-methyl-1H-quinolin-2-one (7). Condensation reaction of compound 7 with different aldehyde derivatives were performed to obtain Schiff base derivatives, which after cyclization gave thiazolidinones and finally they were reacted with N-ethylpiperazine to get target compounds. The newly synthesized compounds were evaluated for their antimicrobial activity against eight bacterial strains (Staphylococcus aureus, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella typhi, Proteus vulgaris, Shigella flexneri) and four fungal strains (Aspergillus niger, Candida albicans, Aspergillus fumigatus, Aspergillus clavatus).

New 4-Thiazolidinones of Nicotinic Acid with 2-Amino-6-methylbenzothiazole and their Biological Activity

The title compounds 6a–j, 2-[(6-methyl-1,3-benzothiazol-2-yl)amino]-N-[2-(substituted phenyl/furan-2-yl)-4-oxo-1,3-thiazolidin-3-yl]nicotinamides, were prepared from 2-chloropyridine-3-carboxylic acid (1) and 2-amino-6-methyl-benzothiazole (2) by known methods. All the compounds have been established by IR, 1H NMR, 13C NMR and elemental analyses. The in vitro antimicrobial screening of the compounds were carried out against two Gram positive (S. aureus, S. pyogenes), two Gram negative (E. coli, P. aeruginosa) bacteria and three fungal species (C. albicans, A. niger, A. clavatus) using the broth microdilution method. Some of the compounds are comparable with standard drugs.

New 2-benzylsulfanyl-nicotinic acid based 1,3,4-oxadiazoles: Their synthesis and biological evaluation

A novel series of 5-(2-benzylsulfanyl-pyridin-3-yl)-2-(substituted)-sulfanyl-1,3,4-oxadiazoles 6a-j were synthesized from key intermediate 5-(2-benzylsulfanyl-pyridin-3-yl)-3H-[1,3,4]oxadiazole-2-thione 5. Nucleophilic substitution reactions with different electrophiles (E+), such as haloacetate and haloalkyl groups, were performed to get target compounds 6a-j. Compounds were characterized by NMR, mass, IR spectra and C, H, N analyses. All compounds were evaluated for their antimicrobial and antimycobacterial activities; selected analogs were screened for their anticancer activity on 60 tumor cell lines at single dose 1.00(-5) M. Unfortunately, none of the compounds showed a significant antitumor activity on 60 human tumor cell lines. However, compounds 6g and 6f with benzothiazole moiety (12.5 and 25 μg/ml) showed promising activity against Escherichia coli compared to ampicillin; compounds 6d, 6j bearing triazole and morpholine, respectively, showed promising antitubercular activity (25 μg/ml) compared to rifampicin.

Antimycobacterial and antimicrobial study of new 1,2,4-triazoles with benzothiazoles

In this study, we report the antimycobacterial and antimicrobial evaluation of newly synthesized 3‐(3‐pyridyl)‐5‐(4‐methoxyphenyl)‐4‐(N‐substituted‐1,3‐benzothiazol‐2‐amino)‐4H‐1,2,4‐triazole 6a–j in good yields. All the synthesized compounds have been established by elemental analysis, IR, 1H NMR, 13C‐NMR and Mass spectral data. In‐vitro antimycobacterial activity was carried out against (Mycobacterium tuberculosis) H37Rv strain using Lowenstein‐Jensen medium and antimicrobial activity against two Gram positive bacteria (Staphylococcus aureus, Streptococcus pyogenes), two Gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa) and three fungal species (Candida albicans, Aspergillus niger, Aspergillus clavatus) using the broth microdilution method. Compounds 2e, 6a, 6g, 6h, and 6j exhibited promising antimicrobial activity whereas compound 6j showed very good antimycobacterial activity.

Synthesis of 1,2,4-triazole derivatives containing benzothiazoles as pharmacologically active molecule

In attempt to make significant pharmacologically active molecule, we report here the synthesis and in vitro antimicrobial and antitubercular activity of various series of 3-(3-pyridyl)-5-(4-nitrophenyl)-4-(N-substituted-1,3-benzothiazol-2-amino)-4H-1,2,4-triazole. The antimicrobial activity of title compounds were examined 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 the broth microdilution method and antitubercular activity H37Rv using Lowenstein-Jensen agar method.

Synthesis and antimicrobial study of fluoroquinolone-based 4-thiazolidinones

The title compounds 2-substituted phenyl-3-{1-cyclopropyl-6-fluoro-7-[4-(4-methoxyphenylpiperazin-1-yl]-4-oxo-1,4-dihydroquinoline} carboxamido-1,3-thiazolidin-4-ones 6a–j have been synthesized from lead molecule 7-chloro-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid 1; this reacted with thionyl chloride to give acid chloride 2 and with hydrazine hydrate to afford hydrazide 3. The hydrazide 3 on condensation with substituted aromatic aldehydes a–j gave Schiff base; these on reaction with N-(4-methoxyphenyl) piperazine and thioglycolic acid furnished title compounds 6a–j. All of the synthesized compounds have been established by elemental analysis. IR and NMR spectral data and have been screened for antifungal and antibacterial activities.

In vitro antimicrobial assessment of coumarin-based s -triazinyl piperazines

A series of 1,3,5-triazine derivatives that contain aniline, coumarins (4-hydroxy coumarin and 7-hydroxy-4-methyl coumarin) and different piperazine moieties as substituent on the carbon atoms of the triazine ring have been synthesized by a simple and efficient synthetic protocol. Comparative studies were performed on above series, which were synthesized with conventional and microwave heating methods. The microwave method was observed to be more beneficial as it provides an increase in yield and 90–95% reduction time. All the synthesized compounds were then examined for their efficacy against two Gram −ve bacteria (Escherichia coli and Pseudomonas aeruginosa), two Gram +ve bacteria (Staphylococcus aureus and Bacillus subtilis) and two fungal species (Candida albicans and Aspergillus niger) with an intent to overcome multiple drug resistance to the pathogenic strains. All the synthesized compounds were structurally elucidated by IR, 1H NMR, 13C NMR and elemental analysis.