Synthesis, characterization and antibacterial activity of 2-[1-(5-chloro-2-methoxy-phenyl)-5-methyl-1H-pyrazol-4-yl]-5-(substituted-phenyl)-[1,3,4]oxadiazoles

In the present investigation a series of novel 2-[1-(5-chloro-2-methoxy-phenyl)-5-methyl-1H-pyrazol-4-yl]-5-(substituted-phenyl)-[1,3,4]oxadiazoles (4a–j) were synthesized by cyclization of substituted-benzoic acid N′-[1-(5-chloro-2-methoxy-phenyl)-5-methyl-1H-pyrazole-4-carbonyl]-hydrazide by using phosphorousoxychloride at 120 °C. The chemical structure of the newly synthesized compounds was characterized by analytical and spectral (IR, ¹H NMR, ¹³C NMR and LC–MS) methods. The title compounds were screened for qualitative (zone of inhibition) and quantitative antibacterial activity (MIC) by agar cup plate and microtitration methods, respectively. Among the synthesized compounds in this series compound 2-[1-(5-chloro-2-methoxyphenyl)-5-methyl-1H-pyrazol-4-yl]-5-(4-fluorophenyl)-1,3,4-oxadiazole (4b) was found to exhibit significant antibacterial activity with MICs of 22.4, 29.8, 29.6 and 30.0 μg/mL against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae, respectively. The other compounds exhibited moderate activity when compared to standard substance Ampicillin.     

5H-[1,2,4]Oxadiazolo[5,4-d][1,5]benzothiazepines as anticonvulsant agents in DBA/2 mice

A series of 3a,4-dihydro-5H-[1,2,4]oxadiazolo[5,4-d][1,5]benzothiazepines have been synthesized by 1,3-dipolar cycloaddition reaction of benzonitriloxide to the CN double bond of 1,5-benzothiazepine derivatives, and the stereochemical features of compounds obtained have been determined by NMR spectroscopy. The results of evaluation of their activity in preventing seizures induced by audiogenic stimulation in DBA/2 mice are also reported and discussed. The 5-(4-bromophenyl)-1,3-diphenyl derivative 3b, the most active compound of the series, is over 20 times more active than the parent benzothiazepine 1b and shows an activity comparable to clobazam and better than desmethylclobazam.     

Synthesis and anticonvulsant activity of 8-alkoxy-5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1]benzazepin-1-one derivatives

A series of novel 8-alkoxy-5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1]benzazepin-1-one derivatives were synthesized and screened for their anticonvulsant activities by the maximal electroshock (MES) test, subcutaneous pentylenetetrazol (scPTZ) test, and their neurotoxicity was evaluated by the rotarod neurotoxicity test (Tox). The results of these tests demonstrated that 8-heptyloxy-5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1]benzazepin-1-one (3f) and 8-hexyloxy -5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1]benzazepin-1-one (3e) were the most promising compounds, with median effective dose (ED₅₀) of 17.6 and 17.9 mg/kg, and protective index (PI) of greater than 63.4 and 62.4 in the MES test, respectively. These PI values were higher than the PI value of the prototype antiepileptic drug carbamazepine. The scPTZ test showed that 8-pentyloxy-5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1]benzazepin-1-one (3d) was the most potent with ED₅₀ value of 38.0 mg/kg and PI value of greater than 29.4, which is much safer than marketed drug carbamazepine. The possible structure-activity relationship was discussed.     

Synthesis and anticonvulsant activity of some new thiazolo[3,2-a][1,3]diazepine, benzo[d]thiazolo[5,2-a][12,6]diazepine and benzo[d]oxazolo[5,2-a][12,6]diazepine analogues

A new series of 6,7-dihydro-thiazolo[3,2-a][1,3]diazepines (9–12), benzo[d]thiazolo[5,2-a][12,6]diazepines (19–21) and benzo[d]oxazolo[5,2-a][12,6]diazepine (24) analogues were synthesized and evaluated for their anticonvulsant activity. Compounds (E)-2-bromo-6,7-dihydro-thiazolo[3,2-a][1,3]diazepine-8(5H)-thione (12), 3-chloro-benzo[d]thiazolo[5,2-a][12,6]diazepin-10-one (20), and 4-chloro-benzo[d]oxazolo[5,2-a][12,6] diazepin-10-one (24) showed 100% protection against PTZ- and bicuculline-induced seizures; 70%, 33%, 70% protection against MES-induced tonic extension; and 70%, 66%, 100% protection against picrotoxin-induced convulsions, respectively. Compounds 12, 20, and 24 proved to act as GABA_A receptor agonists, with ED₅₀ values of 252, 380, 251 mg/kg; TD₅₀ values of 398, 417, 355 mg/kg; PI values of 1.58, 1.09, 1.41; LD₅₀ values of 380, 617, 537 mg/kg and TI values of 1.51, 1.62, 2.14, respectively.     

Synthesis and CNS activity of tricyclic theophylline derivatives. 8-substituted imidazo[2,1-f]theophyllines

Based on previously described results of pharmacological in vitro and in vivo tests of some series of pyrimido- and diazepino-[2,1-f]theophylline derivatives, N8-unsubstituted, N8-benzyl and N8-arylpiperazino-alkyl derivatives of imidazo[2,1-f]theophyllines were synthesized and tested for their CNS activity. It has been shown that tricyclic [2,1-f]theophyllines possess sedative and analgesic activity. N8-Phenylpiperazinopropyl-1,3,6,7-tetrahydro-(8H)-imidazo[2,1-f]theophylline 6 showed significant anti-serotonin and long-lasting hypothermic effects. N8-Benzyl-1,3,6,8-tetrahydroimidazo-7-on[2,1-f]theophylline 8 possess anticonvulsant properties.     

Synthesis of some novel pyrazolo[3,4-b]pyridine and pyrazolo[3,4-d]pyrimidine derivatives bearing 5,6-diphenyl-1,2,4-triazine moiety as potential antimicrobial agents

The reaction of 5,6-diphenyl-3-hydrazino-1,2,4-triazine (1) with bis(methylthio)methylene]malononitrile (2) afforded 5-amino-1-(5,6-diphenyl-1,2,4-triazin-3-yl)-3-(methylthio)-1H-pyrazole-4-carbonitrile (3). Compound 3 reacted with thiourea to give 3,4-diaminopyrazolo[3,4-d]pyrimidine 5, which was treated with benzoyl chloride to give pyrazolo[5,4,3-kl]pyrimido[4,3-d]pyrimidine 6. Treatment of 3 with acetic anhydride produced 3-methylthio-pyrazolo[3,4-d]pyrimidine derivative 7, which was allowed to react with hydrazine hydrate to give the corresponding hydrazino derivative 8. Heterocyclization of 8 with benzoyl chloride and sodium pyruvate afforded the polyfused heterocycles 9 and 10, respectively. Reaction of 3 with benzoylacetone yielded pyrazolo[3,4-b]pyridine 12, which was allowed to react with malononitrile and acetanilide to get heterocyclic systems 13 and 14, respectively. Interaction of 3 with cyanoacetone gave pyrazolo[3,4-b]pyridine 15, which was refluxed in formic acid to yield pyrazolo[4′,3′:5,6]pyrido[4,3-d]pyrimidine 16. Reaction of 3 with 2 afforded the triazinylpyrazole derivative 17, which was reacted with hydrazine hydrate to give dipyrazolo[1,5-a:3′,4′-d]pyrimidine 19. Furthermore, treatment of the latter compound with methyl anthranilate furnished tetraheterocyclic compound 21. Structures of the products have been determined by elemental analysis and spectral studies. All compounds have been screened for their antibacterial and antifungal activities. Compounds 9, 10, 13, 19 and 21 showed maximum activity comparable to the standard drugs with lower toxicity in the case of 9 and 10.     

Synthesis and biological activity of 7H-benzo[4,5]indolo[2,3-b]-quinoxaline derivatives

New 7-(2-aminoethyl)-7H-benzo[4,5]indolo[2,3-b]quinoxalines (13-20) were synthesized with high yields starting from 3H-benzo[e]indole-1,2-dione. These compounds were screened for the cytotoxicity, anti-viral activity, interferon inducing ability and DNA affinity compared with the corresponding 6-(2-aminoethyl)-6H-indolo[2,3-b]quinoxaline derivatives (1-12). It was shown, that compounds 13-20 bind to DNA stronger (lg К_a = 6.23-6.87) than compounds 1-12 (lg К_a = 5.57-5.89). Anti-viral activity is significantly reduced with annulations of benzene ring in Indoloquinoxaline moiety 13-20.     

Synthesis and antitubercular evaluation of novel dibenzo[b,d]furan and 9-methyl-9H-carbazole derived hexahydro-2H-pyrano[3,2-c]quinolines via Povarov reaction

A series of novel hexahydro-2H-pyrano[3,2-c]quinoline analogues derived from dibenzo[b,d]furan and 9-methyl-9H-carbazole has been synthesized in very good yields through SnCl₂·2H₂O catalyzed one-pot Povarov reaction (imino-Diels-Alder reaction). The imines generated in situ from dibenzo[b,d]furan-2-carbaldehyde or 9-methyl-9H-carbazole-3-carbaldehyde and aromatic amines, were reacted with 3,4-dihydro-2H-pyran in a diasteroselective manner in acetonitrile at RT. These synthesized isomeric pyranoquinoline analogues have been evaluated for their in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv (MTB) by agar dilution method. Among the 23 compounds screened, 5-(dibenzo[b,d]furan-2-yl)-9-fluoro-3,4,4a,5,6,10b-hexahydro-2H-pyrano[3,2-c]quinoline 4f, 5-(dibenzo[b,d]furan-2-yl)-9-fluoro-3,4,4a,5,6,10b-hexahydro-2H-pyrano[3,2-c]quinoline 5f and 9-fluoro-5-(9-methyl-9H-carbazol-3-yl)-3,4,4a,5,6,10b-hexa hydro-2H-pyrano[3,2-c]quinoline 7f (MIC 3.13 μg/mL) were resulted as most active antitubercular agents.     

Synthesis and biological evaluation of dihydroindeno and indeno [1,2-e] [1,2,4]triazolo [3,4-b] [1,3,4]thiadiazines as antimicrobial agents

Two series of compounds namely, dihydroindeno and indeno [1,2-e] [1,2,4]triazolo [3,4-b] [1,3,4]thiadizines (9a-l & 11a-l) were synthesized by cyclocondensation between α-bromoindanones (7a-b) or/and α,α-dibromoindanones (8a-b) and various 3-alkyl/aryl-4-amino-5-mercapto-1,2,4-s-triazoles (3a-f) in methanol with an aim to explore their effect on in vitro growth of microorganism causing microbial infection. In vitro antibacterial activity was performed against four strains namely, Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and antifungal activity against three fungal strains namely, Aspergillus niger, Aspergillus flavus, Penicillium species. Of all the compounds screened for activity some of the compounds were associated with considerably higher antibacterial and antifungal activity than commercial antibiotics.     

Drug-induced modifications of the immune response 8. N-(Substituted phenyl)-2,5-dihydro-2-oxo-4-[(substituted phenyl) amino]-3-furancarboxamide derivatives

The synthesis and anti-allergic activity of a series of novel N-(substituted phenyl)-2,5-dihydro-2-oxo-4-[(substituted phenyl)amino]-3-furancarboxamide derivatives (12) are described. The latter were obtained through a novel, and heretofore unknown rearrangement of 2-(N-phenylamino)-4,5-dihydro-4-oxo-3-furancarboxylic acids 8a to the 2(5H)-furanone amides 12.     

Synthesis and antitumor activity of new sulfonamide derivatives of thiadiazolo[3,2-a]pyrimidines

New series of sulfonamide derivatives of [1,3,4]thiadiazolo[3,2-a]pyrimidine were synthesized and investigated as antitumor agents. Some of the newly prepared compounds were tested for their in vitro and in vivo antitumor activities. Preliminary biological studies revealed that compounds 4c, 4f, and 4j exhibited the highest affinity to DNA, while compounds 4h,i, 6a-c, 8 and 12-14 exhibited moderate activity. Also, compounds 4j, 4f and 4c showed the highest percentage increase in lifespan of mice inoculated with Ehrlich ascites cells over 5-flurouracil (positive control). The detailed synthesis, spectroscopic and biological data are reported.     

Design, synthesis and pharmacological evaluation of new 1-[3-(4-arylpiperazin-1-yl)-2-hydroxy-propyl]-3,3-diphenylpyrrolidin-2-one derivatives with antiarrhythmic, antihypertensive, and α-adrenolytic activity

A series of novel arylpiperazines bearing a 3,3-diphenylpyrrolidin-2-one fragment were synthesized and evaluated for their binding affinity for α₁- and α₂-adrenoceptors (ARs), as well as their antiarrhythmic, and antihypertensive activities. The highest affinity for the α₁-AR was displayed by 1-{3-[4-(2-ethoxy-phenyl)-piperazin-1-yl]-2-hydroxy-propyl}-3,3-diphenylpyrrolidin-2-one (7), which binds with a pK_i = 7.28. The highest affinity for the α₂-AR was shown by 1-{3-[4-(2-methoxy-phenyl)-piperazin-1-yl]-2-hydroxy-propyl}-3,3-diphenylpyrrolidin-2-one (5), which binds with a pK_i = 6.68. Compound 7 was additionally evaluated in in vitro functional tests for its affinity for α_1B- and α_1D-AR, which gave pA₂ α_1B = 6.55 and pA₂ α_1D = 7.26. Among the compounds tested, compound 7 also had the highest prophylactic antiarrhythmic activity in adrenaline-induced arrhythmia in anaesthetized rats. Its ED₅₀ value was 1.1 mg/kg (i.v.). The compounds significantly decreased systolic and diastolic pressure in normotensive anaesthetized rats at doses of 2.5–5.0 mg/kg (i.v.) and their hypotensive effects lasted for longer than 1 h. It was found that the introduction of two phenyl ring substituents into the 3rd position of the pyrrolidin-2-one fragment gave compounds with affinity for both α₁- and α₂-AR. The substitution of the 2nd position in the phenyl piperazinyl fragment of the molecule was crucial for activity. To determine detailed information concerning the structure–activity relationship, a preliminary molecular modeling study was undertaken.     

Pyridine and reduced pyridine analogues of 10H-pyrido[3,4-b][1,4]benzothiazines with analgesic activity

Several classes of pyrido 6, 3-methyl-1,2,3,4-tetrahydropyrido 8 and 3-methyl-1,1a,2,3,4,4a-hexahydropyrido 9 analogues of 10H-pyrido[3,4-b][1,4]benzothiazine were synthesized. These compounds all exhibited significant analgesic activity relative to acetylsalicylic acid and dextropropoxyphene. An isosteric relationship between the halophenyl and pyridinyl ring systems is described.     

Synthesis of indolo[3,2-c]quinolines and indolo[3,2-d]benzazepines and their interaction with DNA

A number of indolo[3,2-c]quinolines and tetrahydroindolo[3,2-d]-1-benzazepines were synthesised by Fischer indolisation of ketones including 7-chloro-1,2,3,4-tetrahydroquinol-4-one and 8-chloro-2,3,4,5-tetrahydro-1-benzazepin-5-one with several hydrazines. Some of the planar indolo[3,2-c]quinoline derivatives were shown by their effects on DNA supercoiling to form intercalation complexes with DNA and to inhibit the synthesis of macromolecules in cultured KB cells. Non-planar tetrahydroindolo[3,2-d]-1-benzazepines did not form intercalation complexes with DNA under the same conditions. 3a, b, d inhibited the synthesis of macromolecules in cultured KB cells, 3a being the most effective. No significant anti-tumor activity was detected for 3a, b, 4a, e in the NIH screening program.     

Synthesis and antimicrobial activity of some new 4-hetarylpyrazole and furo[2,3-c]pyrazole derivatives

In continuation of our efforts to find a new class of antimicrobial agents, a series of 4-hetarylpyrazoles and furo[2,3-c]pyrazoles were prepared via the reaction of 2-chloro-1-(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)ethanone (1) with an appropriate nucleophilic reagents. These compounds were screened for their antibacterial activity against Gram-positive bacteria (Bacillus subtilis and Bacillus thuringiensis), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and antifungal activity against Fusarium oxysporum and Botrytis fabae. Among the synthesized compounds, 1-(5-(5-hydroxy-3-methyl-1-phenyl-1H-pyrazole-4-yl)-2-methylfuran-3-yl)ethanone (12) showed equal activity with chloramphenicol against B. subtilis (MIC 3.125 μg/mL), while its activity was 50% lower than of chloramphenicol against B. thuringiensis. N-[(4Z)-3-Methyl-1-phenyl-1H-furo[2,3-c]pyrazol-4(5H)-ylidene]-1H-benzimidazol-2-amine (7) and 2-(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-4H-furo[3,2-c]chromen-4-one (13) were found to exhibit the most potent in vitro antifungal activity with MICs (6.25 μg/mL) against B. fabae and F. oxysporum.     

Novel 4-aryl-pyrido[1,2-c]pyrimidines with dual SSRI and 5-HT(1A) activity. part 3

A number of 4-aryl-5,6,7,8-tetrahydropyrido[1,2-c]pyrimidine with 3-(1,2,3,6-tetrahydro-pyridin-4-yl)-1H-indole or 2-methyl-3-(1,2,3,6-tetrahydro-pyridin-4-yl)-1H-indole residues were synthesized for further investigation of SAR in a group of pyrido[1,2-c]pyrimidine derivatives with dual 5-HT_1A/SERT activity. Compounds 8a-8p were found to be potent ligands for both 5-HT_1A and SERT with K_i ranging from 28,3 to 642 nM and 42,4 nM-1,8 μM, respectively. Moreover compounds 8a, 8b, 8c, 8d, 8e and 8g were found to be selective agonists, while 8i as an antagonist of 5-HT_1A presynaptic receptors in the inducible hypothermia test in mice.     

Synthesis and biological activity of novel N-cycloalkyl-(cycloalkylaryl)-2-[(3-R-2-oxo-2H-[1,2,4]triazino[2,3-c]quinazoline-6-yl)thio]acetamides

In this paper the novel N-cycloalkyl-(cycloalkylaryl)-2-[(3-R-2-oxo-2H-[1,2,4]triazino[2,3-c]quinazoline-6-yl)thio]acetamides synthesis by aminolysis of activated by thionyl chloride or carbonyldiimidazole [(3-R-2-oxo-2H-[1,2,4]triazino[2,3-c]quinazolin-6-yl)-thio]acetic acids and alkylation of the 3-R-6-thio-6,7-dihydro-2H-[1,2,4]triazino[2,3-c]quinazoline-2-ones potassium salts with N-cycloalkyl-(cycloalkylaryl)-2-chloroacetamides are proposed. The structures of compounds are determined by ¹H, ¹³C NMR, LC-MS and EI-MS analysis. The in vitro anticancer, antibacterial activity and Photobacterium leiognathi Sh1 bioluminescence inhibition of synthesized compounds were revealed. SAR results were discussed. Compound 4.10 was found to be the most anticancer active one, selectively influenced on the non-small cell lung and CNS cancer cell lines, especially on the HOP-92 (log GI₅₀ = −6.01) and U251 (log GI₅₀ = −6.00).     

Design, synthesis and antimicrobial activity of chiral 2-(substituted-hydroxyl)-3-(benzo[d]oxazol-5-yl)propanoic acid derivatives

Chiral 2-(substituted-hydroxyl)-3-(benzo[d]oxazol-5-yl)propanoic acid derivatives were synthesized and their antibacterial activities were evaluated against fungus, Gram-negative and Gram-positive bacteria. In general, these compounds showed in vitro activities against all screened Gram-negative and Gram-positive bacteria, but poor MIC values for fungus Candida albicans. Remarkably, the (S)-configuration-substituted phenoxyl side chain on position 2 of propanoic acid exerted excellent antibacterial activity against all screened bacteria. Preliminary structure-activity studies revealed that the hydrophobic substitutes, para-tert-butyl (11r), para-phenyl (11s) and para-benzyloxy (11t) on the phenoxyl side chain displayed best activities against all Gram-negative and Gram-positive bacteria with MIC values between 1.56 and 6.25 μg/mL.     

Synthesis and in vitro antitumour activity evaluation of 1-aryl-1H,3H-thiazolo[4,3-b]quinazolines

A series of 1H,3H-thiazolo[4,3-b]quinazolines (2a–i) were synthesized and evaluated for their in vitro antitumour activity against ca. 60 human tumour cell lines. They exhibited moderate (2c, 2d, 2f and 2g) to strong (2a, 2b, 2e, 2h and 2i) cell-growth inhibition at a concentration of 10⁻⁴ M, but weak activity at lower concentrations. Only 1-(2,6-dichlorophenyl)-1H,3H-thiazolo[4,3-b]quinazoline (2h) possesses a significant growth inhibitory activity on 22 cell lines at a concentration of 10⁻⁵ M.     

Synthesis and inhibition study of monoamine oxidase, indoleamine 2,3-dioxygenase and tryptophan 2,3-dioxygenase by 3,8-substituted 5H-indeno[1,2-c]pyridazin-5-one derivatives

Previous studies on 5H-indeno[1,2-c]pyridazin-5-one derivatives as inhibitors of MAO-B revealed that it was possible to increase the MAO-B inhibitory potency of 5H-indeno[1,2-c]pyridazin-5-ones by substituting the central heterocycle in the 3-position or C-8 with lipophilic groups which occupy the substrate cavity or the entrance of the binding site, respectively. Here, four new 5H-indeno[1,2-c]pyridazin-5-one derivatives containing lipophilic groups at both positions were synthesized and their inhibitory potency against human monoamine oxidase A and B were evaluated. Selectivity of these compounds against IDO and TDO, two enzymes sharing substrate similarity with MAO and involved in the serotonergic and kynurenine pathways was also studied. All compounds showed higher activity and selectivity against MAO-B, the most effective one being 3-methyl-8-meta-chlorobenzyloxy-5H-indeno[1,2-c]pyridazin-5-one (9a) which was shown to be a competitive inhibitor with a K_i value of 0.11 μM. Replacing the methyl group in the 3-position with a meta–CF₃–phenyl group (7a, 7b and 7c) abolished the inhibitory potency against MAO-B. Indeed, the substitution of the 5H-indeno[1,2-c]pyridazin-5-one core in the 3-position dramatically influences the MAO-inhibiting properties of these compounds. Molecular docking studies of 9a within MAO-B suggest that the 5H-indeno[1,2-c]pyridazin-5-one scaffold is well stabilized into the substrate cavity with the meta-chlorobenzyloxy side chain extending towards a rather hydrophobic pocket at the entrance cavity.