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.     

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, characterization and evaluation of antibacterial activity of some thiazolo[3,2-b][1,2,4]triazole incorporating diphenylsulfone moieties

A series of thiazolo[3,2-b][1,2,4]triazole incorporating diphenylsulfone moieties were synthesized starting from 5-[4-(4-X-phenylsulfonyl)phenyl]-4H-1,2,4-triazole-3-thioles 3a–c, X = H, Cl, Br. Thus, alkylation of 1,2,4-triazoles 3 with phenacyl bromide or 4-bromophenacyl bromide afforded S-substituted 1,2,4-triazoles 4, 5. These new intermediates 4 and 5, in the presence of H₂SO₄ (c), were cyclized to 2-[4-(4-X-phenylsulfonyl)phenyl]-6-(4-Y-phenyl)[1,3]thiazolo[3,2-b]-[1,2,4]-triazoles 6, 7 (I) and not to isomeric thiazolo[2,3-c][1,2,4]-triazoles 6, 7 (II). The newly synthesized compounds were characterized by IR, ¹H, ¹³C NMR and elemental analysis. MS spectra confirmed the formation of thiazolo[3,2-b][1,2,4]triazole 6, 7 (forms I) in detriment of [2,3-c] isomeric compounds (forms II). The potential antibacterial effects of the synthesized compounds were investigated using standard bacterial strains: Acinetobacter baumannii ATCC 19606, Citrobacter freundii ATCC 8090, Escherichia coli ATCC 11775, Pseudomonas aeruginosa ATCC 9027, Enterococcus faecalis ATCC 19433, Staphylococcus aureus ATCC 12600, Staphylococcus epidermidis ATCC 14990, Bacillus cereus ATCC 14579.     

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 antimycobacterial evaluation of 3a,4-dihydro-3H-indeno [1,2-c] pyrazole-2-carboxamide analogues

In the present investigation, a series of 3a,4-dihydro-3H-indeno [1,2-c] pyrazole-2-carboxamide analogues were synthesized and were evaluated for antitubercular activity by two fold serial dilution technique. All the newly synthesized compounds showed low to good inhibitory activities against Mycobacterium tuberculosis H₃₇Rv and multi-drug resistant M. tuberculosis (MDR-TB). 3-(4-fluorophenyl)-N-(4-chlorophenyl)-6,7-dimethoxy-3a,4-dihydro-3H-indeno [1,2-c] pyrazole-2-carboxamide (4c) was found to be the most promising compound active against M. tuberculosis, H₃₇Rv and MDR-TB with minimum inhibitory concentrations 0.83 μM and 3.32 μM respectively.     

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.     

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, characterization and pharmacological activity of 4-{[1-substituted aminomethyl-4-arylideneamino-5-sulfanyl-4,5-dihydro-1H-1,2,4-triazol-3-yl]methyl}-2H-1,4-benzothiazin-3(4H)-ones

A new series of Schiff and Mannich bases derivatives (6) of 4-[(4-amino-5-sulfanyl-4H-1,2,4-triazol-3-yl)methyl]-2H-1,4-benzothiazin-3(4H)-one (4), derived from (3-oxo-2,3-dihydro-4H-1,4-benzothiazin-4-yl)acetic acid (3) were synthesized. The structures of all newly synthesized compounds were elucidated by elemental analysis, IR, ¹H NMR and mass spectral data. Synthesized compounds were evaluated for their anti-inflammatory and analgesic activity. Among the tested compounds, the (3-oxo-2,3-dihydro-4H-1,4-benzothiazin-4-yl)acetic acid (3) possess analgesic activity comparable to that of pentazocine; activity decreased on derivatization of the carboxylic acid group. However the anti-inflammatory activity of (3-oxo-2,3-dihydro-4H-1,4-benzothiazin-4-yl)acetic acid (3) increased by derivatization of the carboxylic acid group and some of the compounds showed anti-inflammatory activity comparable to that of indomethacin.     

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.     

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 anticancer activities of some novel 2-(benzo[d]thiazol-2-yl)-8-substituted-2H-pyrazolo[4,3-c]quinolin-3(5H)-ones

A series of 2-(benzo[d]thiazol-2-yl)-8-substituted-2H-pyrazolo[4,3-c]quinolin-3(5H)-ones (3a-g) have been synthesized and evaluated for their in vitro antiproliferative activities against four human cancer cell lines: MDA-MB-435 (breast), HL-60 (leukemia), HCT-8 (colon) and SF-295 (central nervous system). The results showed that the compounds 3b (2-(benzo[d]thiazol-2-yl)-8-methyl-2H-pyrazolo[4,3-c]quinolin-3(5H)-one) and 3c (2-(benzo[d]thiazol-2-yl)-8-bromo-2H-pyrazolo[4,3-c]quinolin-3(5H)-one) exhibited good cytotoxicity for three cell lines with IC₅₀ values lower than 5 μg/mL. Analysis of theoretical toxicity risks have shown medium tumorigenic and irritant risks related to 3b and 3c in contrast to doxorubicin, the positive control.     

Copper(II) chloride mediated synthesis and DNA photocleavage activity of 1-aryl/heteroaryl-4-substituted-1,2,4-triazolo[4,3-a]quinoxalines

A new class of photonucleases, 1-aryl/heteroaryl-4-substituted-1,2,4-triazolo[4,3-a]quinoxalines (4) was synthesized in a facile and efficient manner via copper(II) chloride mediated oxidative intramolecular cyclization of 2-(arylidenehydrazino)-3-substituted-quinoxalines (3). DNA cleavage potency of compounds 4a–d (40 μg each) was quantitatively evaluated on supercoiled plasmid ΦX174 under UV irradiation (312 nm, 15 W) without any additive. Compound 4c was found to be the most efficient DNA photocleaver which had converted supercoiled DNA (form I) into the relaxed DNA (form II) at 30 μg and the DNA photocleavage activity increases with increase in concentration of 4c.     

Design, synthesis and in vitro evaluation of bridgehead fluoromethyl analogs of N-{2-[4-(2-methoxyphenyl)piperazin-1-yl]ethyl}-N-(pyridin-2-yl)cyclohexanecarboxamide (WAY-100635) for the 5-HT(1A) receptor

Fluorinated analogs that are related to the 5-hydroxytryptamine (5-HT_1A) antagonist, N-{2-[4-(2-methoxyphenyl)piperazin-1-yl]ethyl}-N-(pyridin-2-yl)cyclohexanecarboxamide (WAY-100635), have been synthesized and their binding affinity for the 5-HT_1A receptor and other neurotransmitter receptors (adrenoceptors, sigma receptors, and dopamine receptors), and serotonin transporters was examined in vitro. These ligands were designed to provide a possible potential positron emission tomography (PET) ligand with high metabolic stability. To this end, the cyclohexyl moiety in WAY-100635 and in O-desmethyl WAY-100635 was replaced by a bridge-fused ring (BFR) such as adamantyl, cubyl, bicyclo[2.2.2]octyl and bicyclo[2.2.1]heptyl to reduce the metabolic rate of the amide bond hydrolysis, while a fluoromethyl group was introduced on the other bridgehead of the BFR to prevent defluorination by HF elimination. All synthesized analogs displayed high affinity in the (sub)nanomolar range for the 5-HT_1A receptor, comparable to WAY-100635. In addition, 6b, 6c and 6d were reasonably selective to the 5-HT_1A receptor over the above mentioned receptors. In human hepatocytes, 6b showed a suitable metabolic stability.In conclusion, the obtained data provides a promising starting point for the synthesis of the corresponding ¹⁸F-labeled PET analogs.     

Synthesis, anti-hypertensive and β-adrenoreceptor antagonist activities of 3-[4-[3-(4-aryl-1-piperazinyl)-isopropanoloxy]-phenyl]-4(3H quinazolones

The synthesis of seven 2-substituted 3-[4-[3-(4-aryl-1-piperazinyl)-isopropanoloxy]-phenyl]-4(3H)quinazolones is described. Pharmacological tests showed that some of the synthesized compounds (3a–c and 3e) possessed pronounced and sustained hypotensive effects, as tested in anesthetized normotensive rabbits, adrenoreceptor antagonist properties with respect to the α- and β-receptors and central nervous system depressant effect.     

Design and synthesis of 2-phenylimidazo[1,2-a]pyridines as a novel class of melatonin receptor ligands

A novel class of imidazo[1,2-a]pyridines as melatonin receptor ligands is designed and synthesized. The affinities of 3-(6-methoxy-2-phenylimidazo[1,2-a]pyridine-3-yl)-N-methyl-propionamide 8, N-[2-(6-methoxy-2-phenylimidazo[1,2-a]pyridine-3-yl)-ethyl]-acetamide 13 and N-(1-hydroxy-3-(5-methoxy-2-phenyl-1H-indol-3-yl)propan-2-yl)acetamide 18 are evaluated for binding on melatonin receptors. Compound 8 present good selectivity for MT₂ over MT₁ (MT₁/MT₂ = 19) and compound 13 have good affinities for both MT₁ (Ki :28 nM) and MT₂ (Ki : 8 nM).     

Design, synthesis and antiepileptic properties of novel 1-(substituted benzylidene)-3-(1-(morpholino/piperidino methyl)-2,3-dioxoindolin-5-yl)urea derivatives

Twenty new 1-(substituted benzylidene)-3-(1-(morpholino/piperidino methyl)-2,3-dioxoindolin-5-yl) urea derivatives were designed and synthesized. Antiepileptic screening was performed using MES and scPTZ seizures tests. The neurotoxicity was determined by rotorod test. In the preliminary screening, compounds 5c, 5g, 5j and 5n were found active in MES model, while 5o showed significant antiepileptic activity in scPTZ model. Further all these five compounds were administered orally to rats, 5c, 5g and 5n showed better activity than Phenytoin in oral route. Among these compounds 5c revealed protection in MES at a dose of 30 mg/kg and 100 mg/kg 0.5 h and 4 h after i.p. administration respectively. This molecule provided also protection in the scPTZ at a dose of 300 mg/kg in both time intervals.     

Synthesis and preliminary pharmacological evaluation of imidazo[2,1-f]purine-2,4-dione derivatives

A series of N-8-arylpiperazinylpropyl derivatives of 1,3-dimethyl-(1H,8H)-imidazo[2,1-f]purine-2,4-dione (2–10) and amide derivatives of 1,3-dimethyl-6,7-dihydroimidazo[2,1-f]purine-2,4-(1H,3H)-dione-7-carboxylic acid (11–13) were synthesized. Compounds (2–10) evaluated in vitro were potent 5-HT_1A receptor ligands. Preclinical studies indicated that 8-[3-(N4-phenyl)-piperazin-N1-yl-propyl]-1,3-dimethyl-(1H,8H)-imidazo[2,1-f]purine-2,4-dione (2) exerts anxiolytic-like activity in the four-plate test in mice; however its effect was weaker, than that produced by Diazepam. This compound and 8-[3-(N4-2′-metoxyphenyl)-piperazin-N1-yl-propyl]-1,3-dimethyl-(1H,8H)-imidazo[2,1-f]purine-2,4-dione (3) behaved like antidepressants in the forced swimming test in mice; and their activity in that model was comparable with the effect of Imipramine. The obtained results suggested that the long-chain arylpiperazines (LCAPs) linked to tricyclic derivatives of the theophylline remain a worthy of future research for obtaining new derivatives with potential anxiolytic/antidepressant activity.     

Synthesis of novel bioactive derivatives of 3-(4-chlorophenyl)-2-hydrazino-5,6,7,8-tetrahydrobenzo(b)thieno[2,3-d]pyrimidine-4(3H)-ones

A series of triazolo[4,3-a]tetrahydrobenzo(b)thieno[3,2-e]pyrimidine-5(4H)-ones (12a–n) were synthesized and evaluated for CNS depressant, skeletal muscle relaxant and anticonvulsant activities by photoactometer, Rotarod and pentylenetetrazole induced the convulsions method respectively in Swiss albino mice. Diazepam was used as standard drug. The five derivatives 12b, 12c, 12d, 12i and 12m showed the CNS depressant and skeletal muscle relaxant activities comparable to those of diazepam at a dose of 5 mg/kg. These derivatives also exhibited good activity when tested for anticonvulsant activity in mice at different dose levels. The ED₅₀ values for these derivatives are in the range of 4.40–9.33 mg/kg.     

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.