Synthesis, antitubercular and antimicrobial evaluation of 3-(4-chlorophenyl)-4-substituted pyrazole derivatives

As a part of our research to develop novel antitubercular and antimicrobial agents, a series of 3-(4-chlorophenyl)-4-substituted pyrazoles have been synthesised. These compounds were tested for antitubercular activity in vitro against Mycobacterium tuberculosis H37Rv strain using the BACTEC 460 radiometric system, antifungal activity against a pathogenic strain of fungi and antibacterial activity against gram-positive and gram-negative organisms. Among them tested, many compounds showed good to excellent antimicrobial and antitubercular activity. The results suggest that hydrazones, 2-azetidinones and 4-thiazolidinones bearing a core pyrazole scaffold would be potent antimicrobial and antitubercular agents.     

Discovery of (Z)-2-phenyl-3-(1H-pyrrol-2-yl)acrylonitrile derivatives active against Haemonchus contortus and Ctenocephalides felis (cat flea)

A series of 2-phenyl-3-(1H-pyrrol-2-yl)acrylonitrile derivatives were synthesized and evaluated for in vitro activity against the endoparasite Haemonchus contortus and the ectoparasite Ctenocephalides felis. Some compounds had significant in vitro activity against these parasites.     

Synthesis and antimycobacterial activity of 4-[5-(substituted phenyl)-4, 5-dihydro-3-isoxazolyl]-2-methylphenols

Compounds based on the isoxazoline moiety were screened for their antimycobacterial activity in vitro against Mycobacterium tuberculosis H37R (MTB), and INH (isoniazid) resistant Mycobacterium tuberculosis (INHR-MTB) using the agar dilution method and bactec 460. Among the synthesized compounds, 4-[5-(4-bromophenyl)-4,5-dihydro-3-isoxazolyl]-2-methylphenol (4l) was found to be the most active agent against MTB and INHR-MTB with minimum inhibitory concentration of 0.62 microM. When compared to INH, compound (4l) was 1.12 fold and 3.0 fold more active against MTB and INHR-MTB, respectively.     

Synthesis and pharmacological evaluation of some 3-phenyl-2-substituted-3H-quinazolin-4-one as analgesic, anti-inflammatory agents

A variety of novel 3-phenyl-2-substituted-3H-quinazolin-4-ones were synthesized by reacting the amino group of 2-hydrazino-3-phenyl-3H-quinazolin-4-one with different aldehydes and ketones. The starting material 2-hydrazino-3-phenyl-3H-quinazolin-4-one was synthesized from aniline. The title compounds were investigated for analgesic, anti-inflammatory and ulcerogenic index activities. While the test compounds exhibited significant activity, compounds, 2-(N'-2-butylidene-hydrazino)-3-phenyl-3H-quinazolin-4-one (AS1), 2-(N'-3-pentylidene-hydrazino)-3-phenyl-3H-quinazolin-4-one (AS2) and 2-(N'-2-pentylidene-hydrazino)-3-phenyl-3H-quinazolin-4-one (AS3), exhibited moderate analgesic activity. The compound 2-(N'-2-pentylidene-hydrazino)-3-phenyl-3H-quinazolin-4-one (AS3) showed more potent anti-inflammatory activity when compared to the reference standard diclofenac sodium. Interestingly, the test compounds showed only mild ulcerogenic side effect when compared to aspirin.     

Synthesis and bioassay evaluation of 1-(4-substitutedideneaminooxymethyl)-phenyl-3-(2,6-difluorobenzoyl)ureas

A variety of novel 1-(4-substitutedideneaminooxymethyl)-phenyl-3-(2,6-difluorobenzoyl)ureas were designed and synthesized by the reaction of 4-substitutedideneaminooxymethyl aniline with 2,6-difluorobenzoyl isocyanates in good yields. The title compounds were soluble in most organic solvents, which should make them easier to use. The preliminary bioassay showed that some of the title compounds show excellent insecticidal activity against Mythimna separata at the dosage of 25 mg kg(-1) and moderate insecticidal activity against Nephotettix cincticeps at the dosage of 500 mg kg(-1). Toxicity assays indicated that these title compounds cause in M. separata and N. cincticeps such symptoms of toxicity as discolouration, and weight loss, and cessation of feeding and lethal. One title compound exhibited acaricidal activity against Tetranychus urticae.     

Discovery of novel antitubercular 1,5-dimethyl-2-phenyl-4-([5-(arylamino)-1,3,4-oxadiazol-2-yl]methylamino)-1,2-dihydro-3H-pyrazol-3-one analogues

In search of potential therapeutics for tuberculosis, we describe herewith the synthesis, characterization and antimycobacterial activity of 1,5-dimethyl-2-phenyl-4-([5-(arylamino)-1,3,4-oxadiazol-2-yl]methylamino)-1,2-dihydro-3H-pyrazol-3-one analogues. Among the synthesized compounds, 4-[(5-[(4-fluorophenylamino]-1,3,4-oxadiazol-2-yl)methylamino]-1,2-dihydro-1,5-dimethyl-2-phenylpyrazol-3-one (4a) was found to be the most promising compound active against Mycobacterium tuberculosis H(37)Rv and isoniazid resistant M. tuberculosis with minimum inhibitory concentrations, 0.78 and 3.12μg/mL, respectively, free from any cytotoxicity (>62.5μg/mL).     

Synthesis and antimicrobial activity of novel 2-thiazolylimino-5-arylidene-4-thiazolidinones

New 2-thiazolylimino-5-arylidene-4-thiazolidinones (compounds 4a-j), unsubstituted or carrying hydroxy, methoxy, nitro and chloro groups on the benzene ring, were synthesized and assayed in vitro for their antimicrobial activity against Gram positive and Gram negative bacteria, yeasts and mould. The compounds were very potent towards all tested Gram positive microorganisms (MIC ranging from 0.03 to 6 microg/mL in most of the cases) and Gram negative Haemophilus influenzae (MIC 0.15-1.5 microg/mL), whereas no effectiveness was exhibited against Gram negative Escherichia coli and fungi up to the concentration of 100 microg/mL. The 5-arylidene derivatives showed an antibacterial efficacy considerably greater than that of the parent 2-(thiazol-2-ylimino)thiazolidin-4-one 3, suggesting that the substituted and unsubstituted 5-arylidene moiety plays an important role in enhancing the antimicrobial properties of this class of compounds. The remarkable inhibition of the growth of penicillin-resistant staphylococci makes these substances promising agents also for the treatment of infections caused by microorganisms resistant to currently available drugs.     

Synthesis, antimicrobial activity and molecular modeling studies of halogenated 4-[1H-imidazol-1-yl(phenyl)methyl]-1,5-diphenyl-1H-pyrazoles

During the course of our studies in the azole antifungals area, we synthesized a number of 1,5-disubstituted 4-[1H-imidazol-1-yl(phenyl)methyl]-1H-pyrazoles, analogues of bifonazole. 1,5-Diphenyl-1H-pyrazole 3 showed weak antimycotic and antibacterial activities in vitro against Candida albicans, Cryptococcus neoformans and Staphylococcus aureus. In order to increase these properties, given that the halo substitution was found to be capable of enhancing antifungal effects, we prepared a series of fluoro and chloro derivatives of 3. The microbiological evaluation carried out on newly synthesized compounds included in vitro assays for antifungal, antibacterial and antimycobacterial activities. Among the tested compounds, some dichloro and trichloro-derivatives showed interesting antimicrobial properties. In particular, compounds 10j,k,l produced inhibitory effects against pathogen representatives of yeast (C. albicans, C. neoformans) and Gram positive bacteria (S. aureus) similar or superior to those of bifonazole. In addition, their activity against Mycobacterium tuberculosis was superior to that of clotrimazole and econazole, which were used as reference drugs. The replacement, in these compounds, of chlorine with fluorine atoms led to inactive derivatives. Docking studies were carried out on the most active compounds, in order to rationalize the pharmacological results.     

Design and synthesis of novel 1-phenyl-3-(5-(pyrimidin-4-ylthio)-1,3,4-thiadiazol- 2-yl)urea derivatives with potent anti-CML activity throughout PI3K/AKT signaling pathway

In this investigation, a series of 1-phenyl-3-(5-(pyrimidin-4-ylthio)-1,3,4- thiadiazol-2-yl)urea receptor tyrosine kinase inhibitors were synthesized by a simple and efficient structure-based design. Structure-activity relationship (SAR) analysis of these compounds based on cellular assays led to the discovery of a number of compounds that showed potent activity against human chronic myeloid leukemia (CML) cell line K562, but very weak or no cellular toxicity through monitoring the growth kinetics of K562 cell during a period of 72 h using the real-time live-cell imaging. Among these compounds, 1-(5-((6-((3-morpholinopropyl) amino)pyrimidin-4-yl)thio)-1,3,4-thiadiazol-2-yl)-3-(4-(trifluoromethyl)phenyl)urea (7) exhibited the least cellular toxicity and better biological activity in cellular assays (K562, IC₅₀: 0.038 μM). Compound 7 also displayed very good induced-apoptosis effect for human CML cell line K562 and exerted its effect via a significantly reduced protein phosphorylation of PI3K/Akt signal pathway by Human phospho-kinase array analysis. In vitro results indicate that 1-phenyl-3-(5-(pyrimidin-4-ylthio)-1,3,4- thiadiazol-2-yl)urea derivatives are lead molecules for further development as treatment of chronic myeloid leukemia and cancer.     

Syntheses of novel antimycobacterial combinatorial libraries of structurally diverse substituted pyrimidines by three-component solid-phase reactions

A new pyrimidine based scaffold has been developed by three-component solid-phase syntheses. The utility of scaffolds was demonstrated by synthesizing libraries of 80 substituted pyrimidines (a-p), (a-p), 14(a-p), 15(a-p), 16(a-p). Among 80 compounds screened, six compounds, 12i, 13c, 14d, 14e, 14o, and 15d showed in vitro activity against Mycobacterium tuberculosis (MABA) at a concentration of 50 and 25 microg/mL     

Design and synthesis of positional isomers of 5 and 6-bromo-1-[(phenyl)sulfonyl]-2-[(4-nitrophenoxy)methyl]-1H-benzimidazoles as possible antimicrobial and antitubercular agents

In this Letter, we report the structure–activity relationship (SAR) studies on series of positional isomers of 5(6)-bromo-1-[(phenyl)sulfonyl]-2-[(4-nitrophenoxy)methyl]-1H-benzimidazoles derivatives 7(a–j) and 8(a–j) synthesized in good yields and characterized by ¹H NMR, ¹³C NMR and mass spectral analyses. The crystal structure of 7a was evidenced by X-ray diffraction study. The newly synthesized compounds were evaluated for their in vitro antibacterial activity against Staphylococcus aureus, (Gram-positive), Escherichia coli and Klebsiella pneumoniae (Gram-negative), antifungal activity against Candida albicans, Aspergillus flavus and Rhizopus sp. and antitubercular activity against Mycobacterium tuberculosis H37Rv, Mycobacterium smegmatis, Mycobacterium fortuitum and MDR-TB strains. The synthesized compounds displayed interesting antimicrobial activity. The compounds 7b, 7e and 7h displayed significant activity against Mycobacterium tuberculosis H37Rv strain.     

Synthesis, antibacterial activity, and quantitative structure-activity relationships of new (Z)-2-(nitroimidazolylmethylene)-3(2H)-benzofuranone derivatives

A new series of (Z)-2-(1-methyl-5-nitroimidazole-2-ylmethylene)-3(2H)-benzofuranones (11a-p) and (Z)-2-(1-methyl-4-nitroimidazole-5-ylmethylene)-3(2H)-benzofuranones (12a-m) were synthesized and assayed for their antibacterial activity against Gram-positive and Gram-negative bacteria. Most of the 5-nitroimidazole analogues (11a-p) showed a remarkable inhibition of a wide spectrum of Gram-positive bacteria (Staphylococcus aureus, Streptococcus epidermidis, MRSA, and Bacillus subtilis) and Gram-negative Klebsiella pneumoniae, whereas 4-nitroimidazole analogues (12a-m) were not effective against selected bacteria. The quantitative structure-activity relationship investigations were applied to find out the correlation between the experimentally evaluated activities with various parameters of the compounds studied. The QSAR models built in this work had reasonable predictive power and could be explained by the observed trends in activities.     

Synthesis and antibacterial activity of 1-[1,2,4-triazol-3-yl] and 1-[1,3,4-thiadiazol-2-yl]-3-methylthio-6,7-dihydrobenzo[c]thiophen-4(5H)ones

A series of 1-[1,2,4-triazol-3-yl] and 1-[1,3,4-thiadiazol-2-yl]-3-methylthio-6,7-dihydrobenzo[c]thiophen-4(5H)ones were synthesized and tested to demonstrate in vitro antimicrobial activity. Some of these compounds exhibited a good activity against Staphylococcus aureus, S. epidermidis and Bacillus subtilis.     

Synthesis and in vitro antimycobacterial activity of N1-nicotinoyl-3-(4'-hydroxy-3'-methyl phenyl)-5-[(sub)phenyl]-2-pyrazolines

A series of N1-nicotinoyl-3- (4'-hydroxy-3'-methyl phenyl)-5-(substituted phenyl)-2-pyrazolines were synthesized by the reaction between isoniazid (INH) and chalcones and were tested for their antimycobacterial activity in vitro against Mycobacterium tuberculosis H37Rv (MTB) and INH-resistant M. tuberculosis (INHR-MTB) using the agar dilution method. Among the synthesized compounds, compound (i) N1-nicotinyl-3-(4'-hydroxy-3'-methyl phenyl)-5-(1'-chlorophenyl)-2-pyrazoline was found to be the most active agent against MTB and INHR-MTB, with minimum inhibitory concentration of 0.26 microm. When compared to INH-compound i was found to be 2.8- and 43.7-fold more active against MTB and INHR-MTB, respectively.     

Design, synthesis, synergistic antimicrobial activity and cytotoxicity of 4-aryl substituted 3,4-dihydropyrimidinones of curcumin

3,4-Dihydropyrimidinones of curcumin were synthesized in excellent yield by multi-component one-pot condensation of curcumin, substituted aromatic aldehydes and urea/thiourea under solvent free conditions using SnCl(2)·2H(2)O catalyst. All the synthesized compounds have been characterized by IR, (1)H NMR, (13)C NMR, Mass spectra as well as elemental analyses. The synthesized compounds 4a-n were evaluated for their synergistic antimicrobial (antibacterial and antifungal) activity against bacteria and fungi. Zone of inhibition was measured by adopting disc diffusion method. In vitro minimum inhibitory concentrations were measured using broth microdilution and food poisoning method. In addition to this in vitro cytotoxicity of synthesized compounds against three human cancer lines Hep-G2, HCT-116 and QG-56 were also evaluated. Most of the compounds showed interesting antimicrobial and cytotoxic activity as compared to curcumin, that is, the compounds derived from 2-hydroxy benzaldehyde, 4-hydroxy benzaldehyde and 4-hydroxy-3-methoxy benzaldehyde showed the highest biological activity as compared to other compounds.     

Comparison of anti-aggregatory activities of 5-phenyl-3-(3-pyridyl)isoxazole and 5-phenyl-3-(3-pyridyl)-1,2,4-oxadiazole

Two bioisosteric analogs, 5-phenyl-3-(3-pyridyl)isoxazole and 5-phenyl-3-(3-pyridyl)-1,2,4-oxadiazole, were synthesized so as to compare their antiaggregatory activities, to determine a pharmacologically active fragment in molecules of this type, and to explore the mechanisms of action of potential antiag-gregatory compounds belonging to the class of 3,5-substituted isoxazoles. Antiaggregatory activities of these compounds were studied in vitro using three aggregation inducers, such as arachidonic acid, adenosine diphosphate, and adrenaline. It was shown that 5-phenyl-3-(3-pyridyl)-1,2,4-oxadiazole and 5-phenyl-3-(3-pyridyl)isoxazole completely suppressed platelet aggregation induced by arachidonic acid and the second wave of platelet aggregation induced by adrenaline or adenosine diphosphate. The antiaggregatory activity of substituted isoxasole was 1.1–1.5 times higher than that of substituted oxadiazole. In contrast to the isoxazole analog, 5-phenyl-3-(3-pyridyl)-1,2,4-oxadiazole in concentrations of 300–400 μM partially suppressed the first wave of aggregation induced by adenosine diphosphate. It was demonstrated that both compounds were not thrombin inhibitors in vitro at concentrations up to 250 μM. Thus, introduction of a nitrogen atom into the C4-position of the isoxazole ring changes the molecule properties. It suggests that the pharmacophoric fragment of the molecule should be the whole isoxazole or 1,2,4-oxadiazole ring but not a part of the ring as was supposed previously.     

Substituted 3-((Z)-2-(4-nitrophenyl)-2-(1H-tetrazol-5-yl) vinyl)-4H-chromen-4-ones as novel anti-MRSA agents: synthesis, SAR, and in-vitro assessment

In search for a new antibacterial agent with improved antimicrobial spectrum and potency, we designed and synthesized a series of novel 3-((Z)-2-(4-nitrophenyl)-2-(1H-tetrazol-5-yl) vinyl)-4H-chromen-4-ones 7a-h by convergent synthesis approach. All the synthesized compounds were assayed for their in-vitro antibacterial activities against gram-negative and gram-positive bacteria. The preliminary structure-activity relationship, to elucidate the essential structure requirements for the antimicrobial activity that results into anti-MRSA (methicillin-resistant S. aureus) potential, has been described. Amongst the synthesized compounds 7d, 7e, 7f and 7h were found to possess activity against methicillin-resistant S. aureus in addition to the activity against other bacterial strains such as E. faecalis, S. pneumoniae, and E. coli.     

Synthesis, stereochemistry and in vitro antimicrobial evaluation of novel 2-[(2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-ylidene)hydrazono]-4-phenyl-2,3-dihydrothiazoles

2-[(2,4-Diaryl-3-azabicyclo[3.3.1]nonan-9-ylidene)hydrazono]-4-phenyl-2,3-dihydrothiazoles (3a-3k) have been synthesized by the cyclization of 2-[(2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-one thiosemicarbazones with phenacyl bromide and characterized by analytical (melting point and elemental analysis) and spectral (IR, (1)H NMR, (13)C NMR, D(2)O exchange, NOESY and mass) techniques. The novel Hantzsch products (3a-3k) were screened for their in vitro antibacterial and antifungal activities against some selected microorganisms. Structure activity relationship (SAR) for the reported compounds was studied by comparing their MIC values with standard drugs (Streptomycin and Amphotericin B). The results show that 3e against Escherichia coli and Cryptococcus neoformans3i against Bacillus Subtilis, 3b against Aspergillus flavus, and 3k against Rhizopus sp. were found to show significant growth inhibition.     

Synthesis,identification and in vitro biological evaluation of some novel quinoline incorporated 1,3-thiazinan-4-one derivatives

The present study describes the synthesis of two new series of 3-hydroxy-N-(4-oxo-2-phenyl-1,3-thiazinan-3-yl)-8-(trifluoromethyl)quinoline-2-carboxamide derivatives (4a–j) and 3-((7-chloroquinolin-4-ylamino)methyl)-2-phenyl-1,3-thiazinan-4-one derivatives (5a–7j). All the compounds were synthesized in moderate to good yield by one-pot three component cyclo-condensation reaction. The newly synthesized compounds were characterized by FT-IR, ¹H, ¹³C NMR and elemental analysis. The compounds were screened for their in vitro antibacterial activity against a panel of pathogenic bacterial strains, antitubercular activity against Mycobacterium tuberculosis H₃₇Rv and also for their in vitro antimalarial activity against Plasmodium falciparum. Among the synthesized compounds two of them (4f and 5f) showed excellent antibacterial activity against C. tetani at 15.6 μg/mL. Some of them exhibited excellent antitubercular (4f & 5f) and good antimalarial (4f, 5f & 6f) activity compared with the first line drugs.     

Synthesis of thiosemicarbazone and 4-thiazolidinone derivatives and their in vitro anti-Toxoplasma gondii activity

Thiosemicarbazone and 4-thiazolidinone derivatives were synthesized in one and two step, respectively, from thiosemicarbazide, in satisfactory yields. Then, the synthesized compounds were submitted to evaluation against host cells infected with Toxoplasma gondii. The present studies showed that thiosemicarbazones 2 and 4-thiazolidinone derivatives 3 were effective against intracellular T. gondii.