Microwave-assisted CAN-catalyzed solvent-free synthesis of N-allyl quinolone-based pyrano[4,3-b]chromene and benzopyrano[3,2-c]chromene derivatives and their antimicrobial activity

A new series of pyrano[4,3-b]chromene and benzopyrano[3,2-c]chromene derivatives have been synthesized via microwave-assisted one-pot, three-component reaction of N-allyl quinolones, cyclic β-diketones, and 4-hydroxy-6-methyl-2H-pyran-2-one/4-hydroxy coumarin in the presence of catalytic amount of ceric ammonium nitrate under solvent-free condition. The protocol offers expeditious and solvent-free synthesis with excellent yield to furnish fused chromenes for their antimicrobial activity. The chemical structures of the synthesized compounds were elucidated by ¹H NMR, ¹³C NMR, FT-IR, elemental analysis, and mass spectral data. All the compounds were screened against a representative panel of pathogenic strains by broth micro dilution minimum inhibitory concentration method. Among these derivatives, compounds 6i, 6k, 6l, and 6m were found to have admirable activity when compared to the standard drugs.     

Synthesis of halogen derivatives of benzo[h]chromene and benzo[a]anthracene with promising antimicrobial activities

The synthesis of novel 7-(4-halophenyl)-8,9-dihydro-7H-12-oxa-9,11-diaza-benzo[a]anthracene derivatives has been reported. The key intermediate 3-amino-9-chloro-1-(4-halophenyl)-1H-benzo[h]chromene-2-carbonitrile (3) was obtained by treating 4-halobenzylidenmalononitriles (1a-c) and ethyl 4-halobenzylidenmalonates (1d-f) with 4-chloro-1-naphthol (2) in ethanolic piperidine solution. Antimicrobial activity was shown for most of the synthesized compounds.     

Synthesis of 5-benzyl-4-aryl-octahydro-1H-benzo[b][1,5]diazepin-2-ones as potent antidepressant and antimicrobial agents

The present study describes the chemical synthesis and pharmacological evaluation of a new series of 11 compounds of aryloctahydrobenzo[b][1,5]-diazepin-2-one in the forced-swimming test in mice. Three compounds (3e, 3f and 3h) exhibited impressive antidepressant activity, measured in terms of percentage decrease in immobility duration. The potent compounds did not show any neurotoxicity in the rotarod test, and the preliminary results are promising enough to warrant further studies around this scaffold. All the compounds were also screened for antimicrobial activity against P. aeruginosa, E. coli, S. Aureus and B. subtilis strains. Some of the compounds possessed marked antimicrobial activities comparable to that of reference drug, Ciprofloxacin.     

Synthesis and molluscicidal activity of new chromene and pyrano[2,3-c]pyrazole derivatives

The chromene derivative 4 reacts with acetic anhydride, phenylisothiocyanate and ethyl orthoformate to afford the N-acetyl derivative 6, the chromenopyrimidine 8 and the formimidate 9, respectively. 2-(1H-Indol-3-ylmethylene)-malononitrile 10b reacts with 1,3-cyclohexanedione and dimedone 11a, b to afford the 4(3-indolyl)-chromene derivatives 12a, b respectively, and with the pyrazolone derivatives 13a-d to afford the arylidene exchange derivatives 14a-c and the pyranopyrazole derivative 15, respectively. The arylidene derivatives 10a, b react also with indane-1,3-dione 16 to afford the arylidene exchange derivatives 18a, b. The molluscicidal activity of the synthesized compounds towards Biomphalaria alexandrina snails, the intermediate host of Schistosoma mansoni, was investigated and most of them showed weak to moderate activity.     

Synthesis and microbiological activity of some 4-butyl-2H-benzo[1,4]thiazin-3-one derivatives.

The synthesis and physicochemical properties of 4-butyl-2H-benzo[1,4]thiazin-3-one derivatives are described. These new compounds were synthesised by alkylation in 4-N position and acylation and/or alkylation of 6-NH2 by phase transfer catalysis. Acid hydrolysis of 6-alkylacylamino group yielded 6-alkylamino-4-butyl-2H-benzo[1,4]thiazin-3-ones. The antimicrobial in vitro activity was determined on five compounds.     

3H-[1,2]Dithiolo[3,4-b]pyridine-3-thione and its derivatives synthesis and antimicrobial activity

A series of 2-substituted isothiazolo[5,4-b]pyridine-3(2H)-thiones, isothiazolo[5,4-b]pyridin-3(2H)-ones, N-substituted 2-sulfanylnicotinamides and the corresponding carbothioamide derivatives were synthesized and evaluated for their antimicrobial activity against several strains of Gram+ and Gram- bacteria and fungi. Chemical syntheses were resumed into a comprehensive cyclic route that enables the reversible conversion for each derivative of the series considered. Among the tested compounds the N-(aralkyl)-2-sulfanylnicotinamides show the highest fungitoxicity (MIC = 1.25-5 microg/ml). The best activity towards Gram-positive bacteria was in the range of 2.5-5 microg/ml. Activity against Gram-negative bacteria was generally very poor for all compounds.     

Synthesis and antimicrobial activity of derivatives of 1-aryl-2-vinylpyrido[2,3-d]pyrimidin-4-one

Translated from Khimiko-farmatsevticheskii Zhurnal, Vol. 28, No. 2, pp. 24–26, February, 1994.     

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

A novel series of 8-alkoxy-5,6-dihydro-4H-benzo[f][1,2,4]triazolo[4,3-a]azepine derivatives were synthesized and characterized by IR, ¹H NMR, ¹³C NMR, mass spectroscopy, and elemental analysis. The newly synthesized compounds were screened for their anticonvulsant activities by the maximal electroshock (MES) test and subcutaneous pentylenetetrazol (scPTZ) test, and their neurotoxic effects were determined by the rotarod neurotoxicity test. Compound 8-pentyloxy-5,6-dihydro-4H-benzo[f][1,2,4]triazolo[4,3-a]azepine (3d) besides being one of the most active compounds had the lowest toxicity. In the anti-MES potency test, it showed median effective dose (ED₅₀) of 17.5?mg/kg, and had protective index (PI) value of 6.5, which is slightly less than that of the prototype drug carbamazepine (PI?=?8.1). Its value of ED₅₀ and PI in the anti-scPTZ test were 21.2 and 5.4, respectively, the latter value (PI) of which is much greater than that of the prototype drug carbamazepine (ED₅₀?>100, PI?<0.72). Possible structure–activity relationship has been discussed.     

Microwave-assisted synthesis of novel 4H-chromene derivatives bearing 2-aryloxyquinoline and their antimicrobial activity assessment

A new series of 4H-chromene derivatives 6a–x bearing 2-aryloxyquinoline nucleus have been synthesized under microwave irradiation by reaction of 2-aryloxyquinoline-3-carbaldehyde 3a–l, malononitrile 4, and compounds (Cyclohexanedione, Dimidone) 5a–b in the presence of NaOH as the basic catalyst. All the compounds were screened against three Gram-positive bacteria (Streptococcus pneumoniae, Clostridium tetani, Bacillus subtilis), three Gram-negative bacteria (Salmonella typhi, Vibrio cholerae, Escherichia coli) and two fungi (Aspergillus fumigatus, Candida albicans) using the broth microdilution MIC (Minimum Inhibitory Concentration) method. Upon study of the antimicrobial screening, it has been observed that a majority of the compounds were found to be active against C. tetani and B. subtilis as well as against C. albicans as compared to the standard drugs.     

Microwave-assisted synthesis and antimicrobial activity of some imidazo[2,1-b][1,3,4]thiadiazole derivatives

A simple and efficient method was developed for the synthesis of 2,6-disubstituted-imidazo[2,1-b][1,3,4]thiadiazoles under microwave (MW) activation using 2-amino-5-substituted-1,3,4-thiadiazoles and appropriate bromo ketones as materials. All reactions demonstrated the benefits of MW reactions: convenient operation, short reaction time, and good yields. All derivatives were characterized by IR, NMR, and Mass spectroscopy. Antibacterial and antifungal activity was performed using cup plate method against Staphylococcus aureus, Klebsiella, and Candida albicans microorganisms. 2-(4-nitro benzyl)-6-(4-bromo phenyl)imidazo[2,1-b][1,3,4]thiadiazole (4Ce) was the only derivative which showed activity against Klebsiella at low micromolar concentration (5?μg/ml) with moderate zone of inhibition. And 2-(4-nitro benzyl)-6-(4-fluoro phenyl)imidazo[2,1-b][1,3,4]thiadiazole (4Cf) as the most potent antifungal active derivative at 50?μg/ml against C. albicans on comparison to standard fluconazole.     

Microwave-assisted synthesis of novel 1,2,3-triazole derivatives and their antimicrobial activity

An environmentally benign and economic synthesis of 1-[7-(1-benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl]-3-aryl-2-propen-1-ones and 1-[5-(1-benzyl-1H-[1,2,3]triazol-4-ylmethoxy)-2,2-dimethyl-chroman-6-yl]-3-aryl-propen-1-ones is described. The procedure takes place by the 1,3-dipolar cycloaddition (‘‘click-reaction’’) between azides and alkynes catalysed by copper (I) salts. The simplicity of this reaction and the ease of formation and purification of the resulting products have opened new opportunities in generating vast arrays of compounds with biological potential. The structures of the synthesized compounds have been established on the basis of physical and spectral data. All the synthesized compounds were tested in vitro for their antibacterial and antifungal activities. Compounds 8a (R₁=H, R₂=H, R₃=H), 8b (R₁=H, R₂=CH₃, R₃=H), 8d (R₁=OCH₃, R₂=OCH₃, R₃=H), 8e (R₁=OCH₃, R₂=OCH₃, R₃=OCH₃), 13a (R₁=H, R₂=H, R₃=H), 13d (R₁=OCH₃, R₂=OCH₃, R₃=H) and 13e (R₁=OCH₃, R₂=OCH₃, R₃=OCH₃) showed significant antimicrobial properties.     

Synthesis of some 3-arylamino-5-aryloxymethyl[1,2,4]triazole derivatives and their antimicrobial activity

In this study, some 3-arylamino-5-aryloxymethyl[1,2,4]triazole derivatives were synthesized by reacting S-methyl-N′-arylisothiouronium iodide and 2-(aryloxy)alkanoic acid hydrazide. The structural elucidation of the compounds was performed by IR, ¹H-NMR and MS spectroscopic data and elemental analyses results. Antibacterial and antifungal activities of the compounds were examined.     

Synthesis and antimicrobial evaluation of new pyrano[4,3-b]pyran and Pyrano[3,2-c]chromene derivatives bearing a 2-thiophenoxyquinoline nucleus

A new series of pyrano[4,3-b]pyran 4a-i and pyrano[3,2-c]chromene 6a-r derivatives bearing a 2-thiophenoxyquinoline nucleus were synthesized by reaction of 2-(4-(un)-substituted thiophenoxy)quinoline-3-carbaldehydes 2a-i with 6-methyl-4-hydroxypyran-2-one 3 and 4-hydroxy-6-(un)-substituted-2H-chromen-2-one 5a-b respectively and malononitrile at room temperature in the presence of KOH as a basic catalyst. All the compounds were screened against three Gram-positive bacteria (Streptococcus pneumoniae, Bacillus subtilis, Clostridium tetani), three Gram-negative bacteria (Salmonella typhi, Escherichia coli, Vibrio cholerae) and two fungi (Candida albicans, Aspergillus fumigatus) using the broth microdilution MIC (minimum inhibitory concentration) method. Upon antimicrobial screening, it was observed that the majority of the compounds were found to be active against Bacillus subtilis, Clostridium tetani and Candida albicans as compared to standard drugs.     

2-substituted 1H-pyrrolo [3,2-h] quinoline derivatives: synthesis and aspects of their biological activity.

Certain 2-substituted 1H-pyrrolo [3,2-h] quinolines have been prepared and their biological activity in mammalian cells and in some microorganisms have been studied. These compounds represent a simplified ellipticine heterocyclic moiety: in addition they have a different ring condensation, leading to an angular molecular structure instead of a linear one. In mammalian cells all compounds appeared to be able of inducing an antiproliferative effect and an extensive DNA fragmentation, similarly to ellipticine, even if to a reduced extent. The new derivatives behaved in a comparable way also on some microorganisms, such as T2 bacteriophage (which appears to be less sensitive than mammalian cells) and in mutagenesis tests carried out with E. coli WP2 TM9 and S. typhimurium TA 98, which are reverted by base substitution and frame-shift mutagens, respectively. Similarly to the reference compound, all ellipticine analogues appeared to be no mutagenic. The obtained results suggest that they induce the antiproliferative activity in mammalian cells mainly as topoisomerase inhibitors, similarly to ellipticine itself. Therefore, they represent an interesting model to design new potential anticancer drugs.     

GdCl3 promoted synthesis of novel pyrimidine fused indazole derivatives and their anticancer activity

The three component Grieco condensation of indazoles, aliphatic/aromatic aldehydes, and electron rich olefins in the presence of GdCl₃ resulted in a novel pyrimidine fused indazoles in single pot under mild conditions. Representative examples were screened for in vitro anti-cancer activity and some of the compounds exhibited promising cytotoxic activity against U937 cell lines in comparable with standard drug etoposide. The data were further compared with structure-based investigations using docking studies with the crystal structure of Rho-kinase (2F2U) protein. The fitness values estimated by genetic algorithm were found to have a good correlation with the experimental inhibitory potencies.     

Green approach towards the facile synthesis of dihydropyrano(c)chromene and pyrano[2,3-d]pyrimidine derivatives and their biological evaluation

A simple and efficient one-pot synthesis of heteroaryl-substituted dihydropyrano(c)chromenes and pyrano[2,3-d]pyrimidines has been developed. Reaction proceeds via initial Knoevenagel, subsequent Michael and final heterocyclization reactions of heteroaryl aldehyde, malononitrile, and barbituric acid/dimedone. Triethylammonium acetate acts as a green catalyst as well as reusable solvents for this reaction. Short reaction time, environment friendly procedure, reusability, and excellent yields are the main advantages of this procedure. All synthesized compounds have shown good antibacterial activity against different microbial stains but not active against cancer cell lines.     

Chromophore-modified bis-benzo[g]indole carboxamides: synthesis and antiproliferative activity of bis-benzo[g]indazole-3-carboxamides and related dimers

Tricyclic pyrazole dimers that comprise two kinds of CONH-(CH(2))(n)-N(CH(3))-(CH(2))(n)-NHCO bridges to which are linked potential DNA-intercalating groups such as 1H-benzo[g]indazole, 2H-benzo[g]indazole and 1,4-dihydroindeno[1,2-c]pyrazole were designed, synthesized and some of them evaluated in vitro by NCI (Bethesda, USA) against nine types of cancer cells. Compounds 2a, 2f-i and 2o-r demonstrated significant antiproliferative activity, all with GI(50) values in the low micromolar range. Preliminary analysis of the structure-activity relationship for dimers 2 indicated that: (i) in the ground terms (2a and 2k) antitumor activities were strongly related to the type of chromophore, (ii) in contrast, either 1H-benzo[g]indazole- or 1,4-dihydroindeno[1,2-c]pyrazole-dimers when bore a N(1)-aryl group (2g, 2h, 2i, 2o, 2p, 2q and 2r) generally showed a good level of antitumor potency and (iii) for the most representative compounds (pairs of compounds: 2g,2h; 2o,2p and 2q,2r) the length of the bridges did not significantly contribute to the variations in cytotoxicity. Two members of this series, 2f and 2q, were selected and tested in the hollow fiber cell assay to evaluate in a preliminary fashion their in vivo antitumor activity. Finally, viscosity measurement of 2f with poly(dA-dT)(2), confirmed that these promising compounds behaved as typical DNA-intercalating agents.     

Synthesis and antimicrobial activity of some thiazolinyl tetrahydrobenzo[b]thiophenes and thiazolinyl tetrahydrobenzothieno[2,3-d]pyrimidin-4-ones.

Two series of novel 3-carbethoxy-2-(3',4'-disubstituted-2',3'- dihydrothiazol-2'-ylidenamino)-4,5,6,7-tetrahydrobenzo[b] thiophenes (3a-o) and 2-methyl-3-(3',4'-disubstituted-2',3'-dihydrothiazol-2'-ylidena mino-5,6,7,8- tetrahydrobenzothieno[2,3-d]pyrimidin-4(3H) ones (8a-o) have been synthesized and tested for antimicrobial activity. All members of the series have been found to exhibit in vitro antibacterial and/or antifungal activities. Activity was optimized by cyclization to the thienopyrimidin-4-ones. In particular, compounds 8e and 8fd were the most active against the 3 tested microorganisms. Their antifungal activity was higher than that exhibited by nystatin while their MIC was found to be nearly equal to that of nystatin.     

Synthesis and antimicrobial activity of novel pyrazolo[3,4-b]quinoline derivatives

New pyrazolo[3,4-b]quinoline derivatives have been prepared by cyclization of the intermediate 2-chloroquinoline-3-carbonitrile 7, namely 3-amino-1H-pyrazolo[3,4-b]quinoline 8a, 3-amino-1-phenyl/(p-substituted)phenyl/-1H-pyrazolo[3,4-b]-quinoline 8b-f. Furthermore, 3-[(3-aryl-4-oxothiazolidin-2-ylidene)amino]-1H-pyrazolo[3,4-b]quinolines 11a,b; 3-[(3-aryl-4-oxothiazin-2-ylidene)amino]-1H-pyrazolo[3,4-b]quinolines 12a,b and 3-(2-aryl-4-oxothiazolidin-3-yl)-1H-pyrazolo[3,4-b]quinolines 13a,b were synthesized. The antimicrobial activity was evaluated for most of the prepared compounds.