Synthesis of novel triazole-linked mefloquine derivatives: Biological evaluation against Plasmodium falciparum

Using 2,8-bis(trifluoromethyl)quinoline, the pharmacophore of mefloquine, as scaffold, eleven novel triazole-linked compounds have been synthesised by the application of CuAAC chemistry. The in vitro biological activity of the compounds on the Plasmodium falciparum chloroquine-sensitive strain NF54 was then determined. The compounds all showed IC₅₀s in the lower μM range with (1R,3S,5R)-N-{[1-(2,8-bis(trifluoromethyl)quinoline-4-yl)-1H-1,2,3-triazol-4-yl]methyl}adamantan-2-amine (29) exhibiting the best activity of 1.00 μM.     

Synthesis of some novel pyrazolo[3,4-d]pyrimidine derivatives as potential antimicrobial agents

The reaction of 4-hydrazino-8-(trifluoromethyl)quinoline (2) with ethoxymethylenecyanoacetate afforded ethyl 5-amino-1-[8-(trifluoromethyl)quinolin-4-yl]-1H-pyrazole-4-carboxylate (3) and that with ethoxymethylenemalononitrile afforded 5-amino-1-[8-(trifluoromethyl)quinolin-4-yl]-1H-pyrazole-4-carbonitrile (5). Compounds 3 and 5 were hydrolyzed to get 5-amino-1-[8-(trifluoromethyl)quinolin-4-yl]-1H-pyrazole-4-carboxylic acid and then reacted with acetic anhydride to afford 6-methyl-1-[8-(trifluoromethyl)quinolin-4-yl]pyrazolo[3,4-d]oxazin-4-one (6), which was condensed with different aromatic amines to give a series of 5-substituted 6-methyl-1-[8-(trifluoromethyl)quinolin-4-yl]-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-ones (7). Compounds 3 and 5 also reacted with formamide, urea, and thiourea affording the corresponding pyrazolo[3,4-d]pyrimidines (8-13), respectively. Structures of the products have been determined by chemical reactions and spectral studies. All compounds of the series have been screened for their antibacterial and antifungal activity studies. The results are summarized in Tables 1 and 2.     

Synthesis and cytotoxic evaluation of certain 4-(phenylamino)furo[2,3-b]quinoline and 2-(furan-2-yl)-4-(phenylamino)quinoline derivatives

Certain 4-(phenylamino)furo[2,3-b]quinoline and 2-(furan-2-yl)-4-(phenylamino)quinoline derivatives were synthesized and evaluated in vitro against the full panel of NCIs 60 cancer cell lines. The preliminary results indicated these tricyclic 4-(phenylamino)furo[2,3-b]quinolines were more cytotoxic than their corresponding 2-(furan-2-yl)-4-(phenylamino)quinoline isomers. For the 4-(phenylamino)furo[2,3-b]quinolines, compounds 2a and 3d are two of the most potent with a mean GI50 value of 0.025 microM in each case. Inactivity of 2b and 2c (positional isomers of 2a) indicated that both electronic environment, and the distance between intercalating pharmacophore and H-bond-donating MeO group are important. For the 2-(furan-2-yl)-4-(phenylamino)quinoline isomers, compound 12 (a mean GI50 of 4.36 microM), which bears a para-COMe substituent, is more active than its meta-substituted counterpart 13 (10.5 microM). However, the electron-donating MeO substituent is preferred at the meta-position, and the cytotoxicity for the meta-substituted derivatives decreased in the order: MeO derivative 14b (3.05 microM) > oxime 16 (6.85 microM) > ketone 13 (10.5 microM) > methyl oxime 18 (20.6 microM).     

Synthesis, antimicrobial and antimycobacterial evaluation of [2-(substituted phenyl)-imidazol-1-yl]-pyridin-3-yl-methanones

A series of [2-(substituted phenyl)-imidazol-1-yl]-pyridin-3-yl-methanones (1-11) were synthesized and screened for their antimicrobial and antimycobacterial activities. Further, a series of [2-(substituted phenyl)-benzimidazol-1-yl]-pyridin-3-yl-methanones (12-20) reported in our earlier study was also screened for their antimycobacterial activity. The antimycobacterial activity results indicated that [2-(4-Nitro-phenyl)-imidazol-1-yl]-pyridin-3-yl-methanone (8, minimum inhibitory concentration [MIC]?=?3.13 μg) was equipotent as standard drug ciprofloxacin and [2-(4-Nitro-phenyl)-benzimidazol-1-yl]-pyridin-3-yl-methanone (16, MIC?=?1.56 μg) was equipotent as standard drug ethambutol. The results of antimicrobial screening demonstrated that 2-[1-(Pyridine-3-carbonyl)-1H-imidazol-2-yl]-benzoic acid (compound 11, MIC?=?0.002 μg) was two times more effective than standard drug ciprofloxacin (MIC?=?0.004 μg) against tested bacterial strains and [2-(2,5-Dimethyl-phenyl)-imidazol-1-yl]-pyridin-3-yl-methanone (compound 3, MIC?=?0.005 μg) was equipotent to the reference compound, fluconazole against tested fungal strains.     

Phosphodiesterase inhibitors. Part 3: Design, synthesis and structure-activity relationships of dual PDE3/4-inhibitory fused bicyclic heteroaromatic-dihydropyridazinones with anti-inflammatory and bronchodilatory activity

(-)-6-(7-Methoxy-2-trifluoromethylpyrazolo[1,5-a]pyridin-4-yl)-5-methyl-4,5-dihydro-3-(2H)-pyridazinone (KCA-1490) is a dual PDE3/4 inhibitor that exhibits potent combined bronchodilatory and anti-inflammatory activity. A survey of potential bicyclic heteroaromatic replacement subunits for the pyrazolo[1,5-a]pyridine core of KCA-1490 has identified the 4-methoxy-2-(trifluoromethyl)benzo[d]thiazol-7-yl and 8-methoxy-2-(trifluoromethyl)quinolin-5-yl analogues as dual PDE3/4-inhibitory compounds that potently suppress histamine-induced bronchoconstriction and exhibit anti-inflammatory activity in vivo.     

Design, synthesis, and evaluation of 3,4-disubstituted pyrazole analogues as anti-tumor CDK inhibitors

Two series of 3,4-disubstituted pyrazole analogues, 3-(benzimidazol-2-yl)-4-[2-(pyridin-3-yl)-vinyl]-pyrazoles (2) and 3-(imidazol-2-yl)-4-[2-(pyridin-3-yl)-vinyl]-pyrazoles (3), were synthesized as novel cyclin-dependent kinase (CDK) inhibitors. Representative compounds showed potent and selective CDK inhibitory activities and inhibited in vitro cellular proliferation in various human tumor cells. The design, synthesis, and preliminary biological evaluation of these pyrazole compounds are reported.     

Antimycobacterial activity of novel 1,2,4-oxadiazole-pyranopyridine/chromene hybrids generated by chemoselective 1,3-dipolar cycloadditions of nitrile oxides

The 1,3-dipolar cycloaddition of nitrile oxides generated in situ from benzohydroximinoyl chloride and triethylamine to 2-aminopyranopyridine-3-carbonitriles and 2-aminochromene-3-carbonitriles occurred chemoselectively furnishing novel 1,2,4-oxadiazole-pyranopyridine/chromene hybrid heterocycles in moderate yields. In vitro screening of these compounds against Mycobacterium tuberculosis H37Rv (MTB) disclosed that the 1,2,4-oxadiazole-pyranopyridine hybrids display enhanced activity relative to the 1,2,4-oxadiazole-chromene hybrids. Among the compounds screened, 3-[3-(4-chlorophenyl)-1,2,4-oxadiazol-5-yl]-4-(2,4-dichlorophenyl)-8-[(E)-(2,4-dichlorophenyl)-methylidene]-6-methyl-5,6,7,8-tetrahydro-4H-pyrano[3,2-c]pyridin-2-amine (MIC: 0.31 μM) is 1.2, 15.2 and 24.6 times more active than standard antitubercular drugs, viz. isoniazid, ciprofloxacin and ethambutol, respectively.     

Novel azolyl-(phenylmethyl)]aryl/heteroarylamines: potent CYP26 inhibitors and enhancers of all-trans retinoic acid activity in neuroblastoma cells

The synthesis and potent inhibitory activity of novel 4-[(imidazol-1-yl and triazol-1-yl)(phenyl)methyl]aryl-and heteroaryl amines versus a MCF-7 CYP26A1 cell assay is described. Biaryl imidazole ([4-(imidazol-1-yl-phenyl-methyl)-phenyl]-naphthalen-2-yl-amine (8), IC(50)=0.5 microM; [4-(imidazol-1-yl-phenyl-methyl)-phenyl]-indan-5-yl-amine (9), IC(50)=1.0 microM) and heteroaryl imidazole derivatives ((1H-benzoimidazol-2-yl)-{4-[(5H-imidazol-1-yl)-phenyl-methyl]-phenyl}-amine (15), IC(50)=2.5 microM; benzooxazol-2-yl-{4-[(5H-imidazol-1-yl)-phenyl-methyl]-phenyl}-amine (16), IC(50)=0.9 microM; benzothiazol-2-yl-{4-[(5H-imidazol-1-yl)-phenyl-methyl]-phenyl}-amine (17), IC(50)=1.5 microM) were the most potent CYP26 inhibitors. Using a CYP26A1 homology model differences in activity were investigated. Incubation of SH-SY5Y human neuroblastoma cells with the imidazole aryl derivative 8, and the imidazole heteroaryl derivatives 16 and 17 potentiated the atRA-induced expression of CYP26B1. These data suggest that further structure-function studies leading to clinical development are warranted.     

Dual neurokinin NK(1)/NK(2) antagonists: N-[(R,R)-(E)-1-arylmethyl-3-(2-oxo-azepan-3-yl)carbamoyl]allyl-N-methyl-3,5-bis(trifluoromethyl)benzamides and 3-[N'-3,5-bis(trifluoromethyl)benzoyl-N-arylmethyl-N'-methylhydrazino]-N-[(R)-2-oxo-azepan-3-yl]propionamides.

Based on the structure of N-[(R,R)-(E)-1-(4-chlorobenzyl)-3-(2-oxoazepan-3-yl)carbamoyl]allyl-N-methyl-3,5-bis(trifluoromethyl)benzamide (1), attempts to improve the NK(2) affinity have resulted in the discovery of N-[(R,R)-(E)-1-(3,4-dichlorobenzyl)-3-(2-oxoazepan-3-yl)carbamoyl]allyl-N-methyl-3,5-bis(trifluoromethyl)benzamide (9, DNK333) exhibiting a 5-fold improved affinity to the NK(2) receptor in comparison to 1. Simplification of the structure via elimination of a chiral centre led to 3-[N'-3,5-bis(trifluoromethyl)benzoyl-N-(3,4-dichlorobenzyl)-N'-methylhydrazino]-N-[(R)-2-oxo-azepan-3-yl]propionamide (22), a potent and fairly balanced NK(1)/NK(2) antagonist.     

N-aryl 2-aryloxyacetamides as a new class of fatty acid amide hydrolase (FAAH) inhibitors

Fatty acid amide hydrolase (FAAH) is a promising target for the development of drugs to treat neurological diseases. In search of new FAAH inhibitors, we identified 2-(4-cyclohexylphenoxy)-N-(3-(oxazolo[4,5-b]pyridin-2-yl)phenyl)acetamide, 4g, with an IC₅₀ of 2.6?µM as a chemical starting point for the development of potent FAAH inhibitors. Preliminary hit-to-lead optimisation resulted in 2-(4-phenylphenoxy)-N-(3-(oxazolo[4,5-b]pyridin-2-yl)phenyl)acetamide, 4i, with an IC₅₀ of 0.35?µM.     

Novel aryl and heteroaryl substituted N-[3-(4-phenylpiperazin-1-yl)propyl]-1,2,4-oxadiazole-5-carboxamides as selective GSK-3 inhibitors

Synthesis, biological evaluation, and SAR dependencies for a series of novel aryl and heteroaryl substituted N-[3-(4-phenylpiperazin-1-yl)propyl]-1,2,4-oxadiazole-5-carboxamide inhibitors of GSK-3beta kinase are described. The inhibitory activity of the synthesized compounds is highly dependent on the character of substituents in the phenyl ring and the nature of terminal heterocyclic fragment of the core molecular scaffold. The most potent compounds from this series contain 3,4-di-methyl or 2-methoxy substituents within the phenyl ring and 3-pyridine fragment connected to the 1,2,4-oxadiazole heterocycle. These compounds selectively inhibit GSK-3beta kinase with IC(50) value of 0.35 and 0.41 microM, respectively.     

Phosphodiesterase inhibitors. Part 4: Design, synthesis and structure-activity relationships of dual PDE3/4-inhibitory fused bicyclic heteroaromatic-4,4-dimethylpyrazolones

(-)-6-(7-Methoxy-2-trifluoromethylpyrazolo[1,5-a]pyridin-4-yl)-5-methyl-4,5-dihydro-3-(2H)-pyridazinone (KCA-1490) is a dual PDE3/4 inhibitor that exhibits potent combined bronchodilatory and anti-inflammatory activity. Here we show that a 4,4-dimethylpyrazolone subunit serves as an effective surrogate for the 5-methyl-4,5-dihydropyridazin-3(2H)-one ring of KCA-1490 whilst lacking a stereogenic centre. The 2- and 7-substituents in the pyrazolo[1,5-a]pyridine subunit markedly influence the PDE-inhibitory profile and can be adjusted to afford either potent PDE4-selective inhibitors or dual PDE3/4 inhibitors. A survey of bicyclic heteroaromatic replacements for the pyrazolo[1,5-a]pyridine allowed further refinement of the inhibitory profile and identified 3-(8-methoxy-2-(trifluoromethyl)imidazo[1,2-a]pyridin-5-yl)-4,4-dimethyl-1H-pyrazol-5(4H)-one as an orally active, achiral KCA-1490 analog with well-balanced dual PDE3/4-inhibitory activity.     

Antimycobacterial activity: a facile three-component [3+2]-cycloaddition for the regioselective synthesis of highly functionalised dispiropyrrolidines

A series of twelve dispiropyrrolidines were synthesized using [3+2]-cycloaddition reactions. The synthesized compounds were screened for their antimycobacterial activity against M. tuberculosis H(37)Rv and INH resistant M. tuberculosis strains using agar dilution method, four of them showed good activity with MIC of less than 1 μM. Compound 4'-[5-(4-fluorophenyl)pyridin-3-yl]-1'-methyldispiro[indan-2,2' pyrrolidine-3',2″-indan]-1,3,1″-trione (4b) was found to be the most active with MIC of 0.1215 and 5.121 μM, respectively.     

Synthesis of some new [1,2,4]triazolo[3,4-b][1,3,4]thiadiazines and [1,2,4]triazolo[3,4-b][1,3,4] thiadiazoles starting from 5-nitro-2-furoic acid and evaluation of their antimicrobial activity

New series of fused 1,2,4-triazoles such as, 6-(aryl)-3-(5-nitrofuran-2-yl)-5,6-dihydro-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles 4-8, 6-(alkyl/aryl amino)-3-(5-nitrofuran-2-yl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles 9-13 and 6-(4-substituted phenyl)-3-(5-nitrofuran-2-yl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines 14-18 have been synthesized via the reaction of 4-amino-5-(5-nitrofuran-2-yl)-4H-1,2,4-triazole-3-thiol 3 with various reagents such as hetero aromatic aldehydes, alkyl/aryl isothiocyanates and 4-substituted phenacyl bromides, respectively. The structures of the newly synthesized compounds have been confirmed on the basis of elemental analysis and spectral studies. The newly synthesized triazolo derivatives have been investigated for their in vitro antibacterial activity. Most of the tested compounds showed interesting antibacterial activity against Staphylococcus aureus. Furthermore, the most potent antibacterial compounds 11-13 were evaluated for their in vitro cytotoxic activity against human cancer cell lines. It was found that compounds 11 and 13 showed higher cytotoxicity against Hep-G2 cell line as compared to standard.     

Synthesis and evaluation of novel 2-butyl-4-chloro-1-methylimidazole embedded chalcones and pyrazoles as angiotensin converting enzyme (ACE) inhibitors

A series of novel 2-butyl-4-chloro-1-methylimidazole embedded aryl and heteroaryl derived chalcones and pyrazoles were synthesized and evaluated for their angiotensin converting enzyme (ACE) inhibitory activity. The condensation of 2-butyl-4-chloro-1-methylimidazole-5-carboxaldehyde with various aryl and heteroaryl methyl ketones in the presence of 10% aqueous NaOH in methanol proceeded efficiently to give the respective chalcones in very good yields. Further, the reaction of chalcones with hydrazine hydrate in acetic acid gave substituted pyrazole analogues. Screening all 36 new compounds using ACE inhibition assay, resulted chalcones with better ACE inhibitory activity compared to the respective pyrazole analogues. Among the chalcones 4a-r, three compounds, (E)-3-(2-butyl-4-chloro-1-methyl-1H-imidazol-5-yl)-1-(5-chlorothiophen-2-yl)prop-2-enone 4i, (E)-3-(2-butyl-4-chloro-1-methyl-1H-imidazol-5-yl)-1-(1H-pyrrol-2-yl)prop-2-enone 4l, (E)-3-(2-butyl-4-chloro-1-methyl-1H-imidazol-5-yl)-1-(dibenzo[b,d] thiophen-2-yl)prop-2-enone 4q were resulted as most active ACE inhibitors with IC(50) of 3.60 μM, 2.24 μM, and 2.68 μM, respectively.     

Novel spiropiperidine-based stearoyl-CoA desaturase-1 inhibitors: Identification of 1′-{6-[5-(pyridin-3-ylmethyl)-1,3,4-oxadiazol-2-yl]pyridazin-3-yl}-5-(trifluoromethyl)-3,4-dihydrospiro[chromene-2,4′-piperidine]

Cyclization of the benzoylpiperidine in lead compound 2 generated a series of novel and highly potent spiropiperidine-based stearoyl-CoA desaturase (SCD)-1 inhibitors. Among them, 1′-{6-[5-(pyridin-3-ylmethyl)-1,3,4-oxadiazol-2-yl]pyridazin-3-yl}-5-(trifluoromethyl)-3,4-dihydrospiro[chromene-2,4′-piperidine] (19) demonstrated the most powerful inhibitory activity against SCD-1, not only in vitro but also in vivo (C57BL/6 J mice). With regard to the pharmacological evaluation, 19 showed powerful reduction of the desaturation index in the plasma of C57BL/6 J mice on a non-fat diet after a 7-day oral administration (q.d.) without causing notable abnormalities in the eyes or skin up to the highest dose (3 mg/kg) in our preliminary analysis.     

Microwave-assisted synthesis of 4'-azaflavones and their N-alkyl derivatives with biological activities

4'-Azaflavone (=2-(pyridin-4-yl)-4H-1-benzopyran-4-one; 4) and 3-[(pyridin-4-yl)methyl]-4'-azaflavone (5) were synthesized by a simple environmentally friendly microwave-assisted one-pot method through the cyclization of 3-hydroxy-1-(2-hydroxyphenyl)-3-(pyridin-4-yl)propan-1-one (1), (E)-2'-hydroxy-4-azachalcone (2; chalcone=1,3-diphenylprop-2-en-1-one), and 2'-hydroxy-2-[(hydroxy)(pyridin-4-yl)methyl]-4'-azachalcone (3) under solventless conditions using silica-supported NaHSO(4), followed by treatment with base. In addition, N-alkyl-substituted 4'-azaflavonium bromides 6 and 7 were prepared from compounds 4 and 5, respectively. The antimicrobial and antioxidant activities of compounds 1-7 were tested. The N-alkyl-substituted 4'-azaflavonium bromides 6 and 7 showed high antimicrobial activity against the Gram-positive bacteria and the fungus tested, with MIC values close to those of reference antimicrobials ampicilline and fluconazole. The alkylated compounds 6 and 7 also showed a good antioxidant character in the two antioxidant methods, DPPH (=1,1-diphenyl-2-picrylhydrazyl) radical-scavenging and ferric reducing/antioxidant power (FRAP) tests.     

Syntheses, crystal structures and antimicrobial activities of thioether ligands containing quinoline and pyridine terminal groups and their transition metal complexes

Eleven transition metal complexes of three asymmetrical tridentate thioether ligands, 8-((pyridin-2-yl)methylthio) quinoline (TQMP2), 8-((pyridin-3-yl)methylthio) quinoline (TQMP3), 8-((pyridin-4-yl)methylthio) quinoline (TQMP4) and one symmetrical pentadentate ligand 2,6-bis (8-quinolinylthiomethyl) pyridine (DTQMP) were prepared. The structures of all these complexes were identified by means of elemental analysis (EA), infrared spectra (IR) and single-crystal diffraction, providing three different kinds of basic conformations, (1) discrete mononuclear structures, (2) dinuclear rings and (3) 1D polymer chains. The antibacterial, antifungal and pesticide activities of the four ligands and 11 complexes were also studied.     

Substituted indoles as potent and orally active 5-lipoxygenase activating protein (FLAP) inhibitors.

This paper reports on the SAR investigation of inhibitors of 5-lipoxygenase activating protein (FLAP) based on MK-0591. Emphasis was made on modifications to the nature of the link between the indole and the quinoline moieties, to the substitution pattern around the two heterocycles and to possible replacements of the quinoline moiety. Lead optimization culminated in (3-[1-(4-chlorobenzyl)-3-(t-butylthio)-5-(pyridin-2-ylmethoxy)-ind ol-2-yl]-2,2-dimethylpropanoic acid (18k), as a potent inhibitor of leukotriene biosynthesis that is well absorbed and active in functional models.     

New hybrid trifluoromethylquinolines as antiplasmodium agents

Malaria remains a major public health problem worldwide, and it is responsible for high rates of morbidity and mortality. Resistance to current antimalarial drugs has been identified, and new drugs are urgently needed. In this study, we designed and synthesized seventeen novel quinolines based on the structures of mefloquine ((2,8-bis(trifluoromethyl)quinolin-4-yl)(piperidin-2-yl)methanol) and amodiaquine (4-((7-chloroquinolin-4-yl)amino)-2-((diethylamino)methyl)phenol) using ring bioisosteric replacement and molecular hybridization of the functional groups. The compounds were evaluated in vitro against Plasmodium falciparum and in vivo in mice infected with P. berghei. All derivatives presented anti-P. falciparum activity with IC₅₀ values ranging from 0.083 to 33.0?µM. The compound with the best anti-P. falciparum activity was N-(5-methyl-4H-1,2,4-triazol-3-yl)-2,8-bis(trifluoromethyl)quinolin-4-amine (12) which showed an IC₅₀ of 0.083?µM. The three most active compounds were selected for antimalarial activity tests against P. berghei-infected mice. Compound 12 was the most active on the 5th day after infection, reducing parasitemia by 66%, which is consistent with its in vitro activity. This is an important result as 12, a simpler molecule than mefloquine, does not contain the stereogenic center, and consequently, its synthesis in the laboratory is easier and less expensive. This system proved promising for the design of potential antimalarial compounds.