Synthesis of new 4-[2-(alkylamino) ethylthio]pyrrolo[1,2-a]quinoxaline and 5-[2-(alkylamino) ethylthio]pyrrolo[1,2-a]thieno[3,2-e]pyrazine derivatives, as potential bacterial multidrug resistance pump inhibitors

The synthesis of new 4-[2-(alkylamino)ethylthio]pyrrolo[1,2-a]quinoxaline derivatives la-1 is described in five or six steps starting from various substituted nitroanilines 2a-e. The bioisostere 5-[2-(alkylamino)ethylthio]pyrrolo[1,2- a]thieno[3,2-e]pyrazine 1m was also prepared. The new derivatives were evaluated as efflux pump inhibitors (EPIs) in a model targeting the NorA system of Staphylococcus aureus. The antibiotic susceptibility of two strains overproducing NorA, SA-1199B and SA-1, was determined alone and in combination with the neo-synthesised compounds by the agar diffusion method and MIC determination, in comparison with reserpine and omeprazole taken as reference EPIs. A preliminary structure-activity relationship study firstly allowed to clarify the influence of the substituents at positions 7 and/or 8 of the pyrrolo[1,2-a]quinoxaline nucleus. Methoxy substituted compounds, 1b and 1g, were more potent EPIs than the unsubstituted compounds (1a and 1f), followed by chlorinated derivatives (1c-d and 1h). Moreover, the replacement of the N,N-diethylamino group (compounds 1a-e) by a bioisostere such as pyrrolidine (compounds 1f-h) enhanced the EPI activity, in contrast with the replacement by a piperidine moiety (compounds 1i-k). Finally, the pyrrolo[1,2-a]thieno[3,2-e]pyrazine compound 1m exhibited a higher EPI activity than its pyrrolo[1,2-a]quinoxaline analogue la, opening the way to further pharmacomodulation.     

Synthesis and antitumor activity of a new class of pyrazolo[4,3-e]pyrrolo[1,2-a][1,4]diazepinone analogs of pyrrolo[1,4]benzodiazepines (PBDs)

A new class of Pyrrolo[1,4]benzodiazepines (PBDs) analogs featuring a pyrazolo[4,3-e]pyrrolo[1,2-a][1,4]diazepinone ring system has been designed and synthesized. In these compounds the A-benzene ring, characteristic of PBDs, has been replaced by a dimethylpyrazole ring, a modification suggested by modelling studies performed on the PBD base structure. Biological evaluation releaved appreciable antitumor activity for compounds 14 and 15 (8.84–22.4 μM) which encourages further investigation of the N⁶ and N⁷ alkyl pyrazole analogs.     

Synthesis and evaluation of the antiproliferative activity of novel pyrrolo[1,2-a]quinoxaline derivatives,potential inhibitors of Akt kinase. Part II

Attenuation of protein kinases by selective inhibitors is an extremely active field of activity in anticancer drug development. Therefore, Akt, a serine/threonine protein kinase, also known as protein kinase B (PKB), represents an attractive potential target for therapeutic intervention. Recent efforts in the development and biological evaluation of small molecule inhibitors of Akt have led to the identification of novel inhibitors with various heterocycle scaffolds. Based on previous results obtained on the antiproliferative activities of new pyrrolo[1,2-a]quinoxalines, a novel series was designed and synthesized from various substituted phenyl-1H-pyrrole-2-carboxylic acid alkyl esters via a multistep heterocyclization process. These new compounds were tested for their in vitro ability to inhibit the proliferation of the human leukemic cell lines K562, U937, and HL60, and the breast cancer cell line MCF7. The first biological evaluation of our new substituted pyrrolo[1,2-a]quinoxalines showed antiproliferative activity against the tested cell lines. From a general SAR point of view, these preliminary biological results highlight the importance of substitution at the C-4 position of the pyrroloquinoxaline scaffold by a benzylpiperidinyl fluorobenzimidazole group, and also the need for a functionalization on the pyrrole ring.     

Design,synthesis and molecular docking of new fused 1H-pyrroles,pyrrolo[3,2-d]pyrimidines and pyrrolo[3,2-e][1, 4]diazepine derivatives as potent EGFR/CDK2 inhibitors

A new series of 1H-pyrrole (6a–c, 8a–c), pyrrolo[3,2-d]pyrimidines (9a–c) and pyrrolo[3,2-e][1, 4]diazepines (11a–c) were designed and synthesised. These compounds were designed to have the essential pharmacophoric features of EGFR Inhibitors, they have shown anticancer activities against HCT116, MCF-7 and Hep3B cancer cells with IC₅₀ values ranging from 0.009 to 2.195 µM. IC₅₀ value of doxorubicin is 0.008 µM, compounds 9a and 9c showed IC₅₀ values of 0.011 and 0.009 µM respectively against HCT-116 cells. Compound 8b exerted broad-spectrum activity against all tested cell lines with an IC₅₀ value less than 0.05 µM. Compound 8b was evaluated against a panel of kinases. This compound potently inhibited CDK2/Cyclin A1, DYRK3 and GSK3 alpha kinases with 10–23% compared to imatinib (1–10%). It has also arrested the cell cycle of MCF-7 cells at the S phase. Its antiproliferative activity was further augmented by molecular docking into the active sites of EGFR and CDK2 cyclin A1.     

Synthesis of new 4-(E)-alkenylpyrrolo[1,2-a]quinoxalines as antileishmanial agents by Suzuki-Miyaura cross-coupling reactions

A series of new 4-(E)-alkenylpyrrolo[1,2-a]quinoxaline derivatives, structural analogues of alkaloid chimanine B, was synthesized in good yields using efficient palladium(0)-catalyzed Suzuki-Miyaura cross-coupling reactions. These new compounds were tested for in vitro antiparasitic activity upon Leishmania amazonensis and Leishmania infantum strains. Biological results showed activity against the promastigote forms of L. amazonensis and L. infantum with IC₅₀ ranging from 0.5 to 7 μM. From a Structure-Activity Relationships point of view, these pharmacological results mainly enlightened the importance of the 4-lateral C₆, C₇ or C₈ α-unsaturated trans-alkenyl chain of unsubstituted pyrrolo[1,2-a]quinoxaline moiety.     

Design,synthesis and antimalarial activity of novel bis{N-[(pyrrolo[1,2-a]quinoxalin-4-yl)benzyl]-3-aminopropyl}amine derivatives

Novel series of bis- and tris-pyrrolo[1,2-a]quinoxaline derivatives 1 were synthesized and tested for in vitro activity upon the intraerythrocytic stage of W2 and 3D7 Plasmodium falciparum strains. Biological results showed good antimalarial activity with IC₅₀ in the μM range. In attempting to investigate the large broad-spectrum antiprotozoal activities of these new derivatives, their properties toward Leishmania donovani were also investigated and revealed their selective antiplasmodial profile. In parallel, the in vitro cytotoxicity of these molecules was assessed on the human HepG2 cell line. Structure–activity relationships of these new synthetic compounds are discussed here. The bis-pyrrolo[1,2-a]quinoxalines 1n and 1p were identified as the most potent antimalarial candidates with selectivity index (SI) of 40.6 on W2 strain, and 39.25 on 3D7 strain, respectively. As the telomeres of the parasite could constitute an attractive target, we investigated the possibility of targeting Plasmodium telomeres by stabilizing the Plasmodium telomeric G-quadruplexes through a FRET melting assay by our new compounds.     

Determination of 6,4′-bis-(2-imidazolinylhydrazone)-2-phenylimidazo[1,2-a]pyridine in plasma and whole blood by high-performance liquid chromatography

A selective and sensitive HPLC assay for the quantitative determination of a new antifilarial drug, 6,4′-bis-(2-imidazolinylhydrazone)-2-phenylimidazo[1,2-a]pyridine (CDR 101) is described. After extraction from plasma and blood, CDR 101 was analysed using a C₁₈ Nucleosil ODS column (250×4.6 mm, 5 μm particle size) and mobile phase of acetonitrile-0.05 M ammonium acetate adjusted to pH 3.0, with UV detection at 318 nm. The mean recoveries of CDR 101 in plasma and blood over a concentration range of 25–500 ng/ml were 95.5±2.01% and 83.3±1.87%, respectively. The within-day and day-to-day coefficient of variations for plasma were 3.23-6.21% and 2.59-9.90%, respectively, those for blood were 2.59-5.92% and 2.89-6.82%, respectively. The minimum detectable concentration for CDR 101 was 1 ng/ml in plasma and 2.5 ng/ml in whole blood. This method was found to be suitable for clinical pharmacokinetic studies.     

Reactions of hybrid organotellurium ligands 1-(4-methoxyphenyl telluro)-2-[3-(6-methyl-2-pyridyl)propoxy]ethane (L) and 1-ethylthio-2-[2-thienyltelluro]ethane (L) with mercury (II) bromide: formation of complexes and their decomposition

Two tellurium ligands 1-(4-methoxyphenyltelluro)-2-[3-(6-methyl-2-pyridyl)propoxy]ethane (L¹) and 1-ethylthio-2-[2-thienyltelluro]ethane (L²) have been synthesized by reacting nucleophiles [4-MeO-C₆H₄Te⁻] and [C₄H₃S-2-Te⁻] with 2-[3-(6-methyl-2-pyridyl)propoxy]ethylchloride and chloroethyl ethyl sulfide, respectively. Both the ligands react with HgBr₂ resulting in complexes of stoichiometry [HgBr₂ · L¹/L²] (1/4), which show characteristic NMR (¹H and ¹³C{¹H}). On crystallization of 1 from acetone-hexane (2:1) mixture, the cleavage of L¹ occurs resulting in 4-MeOC₆H₄HgBr (2) and [RTe⁺→HgBr₂]Br⁻ (3) (where R = -CH₂CH₂OCH₂CH₂CH₂-(2-(6-CH₃-C₅H₃N))). The 2 is characterized by X-ray diffraction on its single crystal. It is a linear molecule and is the first such system which is fully characterized structurally. The Hg-C and Hg-Br bond lengths are 2.085(6) and2.4700(7) Å. The distance of four bromine atoms (3.4041(7)-3.546(7) Å) around Hg (cis to C) is greater than the sum of van der Waal’s radii 3.30 Å. This mercury promoted cleavage is observed for an acyclic ligand of RArTe type for the first time and is unique, as there appears to be no strong intramolecular interaction to stabilize the cleavage products. The 4 on crystallization shows the cleavage of organotellurium ligand L² and formation of a unique complex [(EtS(CH₂)₂SEt)HgBr(μ-Br)Hg(Br)(μ-Br)₂Hg(Br)(μ-Br)BrHg(EtS(CH₂)₂SEt)] · 2HgBr₂ (5), which has been characterized by single crystal structure determination and ¹H and ¹³C{¹H} NMR spectra. The elemental tellurium and [C₄H₃SCH₂]₂ are the other products of dissociation as identified by NMR (proton and carbon-13). The cleavage appears to be without any transmetalation and probably first of its kind. The centrosymmetric structure of 5 is unique as it has [HgBr₃]⁻ unit, one Hg in distorted tetrahedral geometry and one in pseudo-trigonal bipyramidal one. The molecule of 5 may also be described as having [(EtSCH₂CH₂SEt)HgBr]⁺ [HgBr₃]⁻ units, which dimerize and co-crystallize with two HgBr₂ moieties. There are very weak Hg?Br interactions between co-crystallized HgBr₂ units and rest of the molecule. [Hg(3)-Br(1)/Hg(3)-Br(4) = 3.148(1)/3.216(1) Å]. The bridging Hg?Br distances, Hg(2)-Br(4)′, Hg(2)′-Br(4) and Hg(1)-Br(2), are from 2.914(1) to 3.008(1) Å.     

Discovery of new VEGFR-2 inhibitors based on bis([1, 2, 4]triazolo)[4,3-a:3',4'-c]quinoxaline derivatives as anticancer agents and apoptosis inducers

Herein, a new wave of bis([1, 2, 4]triazolo)[4,3-a:3'',4''-c]quinoxaline derivatives have been successfully designed and synthesised. The synthesised derivatives were biologically investigated for their cytotoxic activities against HepG2 and MCF-7. Also, the tested compounds were further examined in vitro for their VEGFR-2 inhibitory activity. The most promising derivative 23j was further investigated for its apoptotic behaviour in HepG2 cell lines using flow cytometric and western-plot analyses. Additional in-silico studies were performed to predict how the synthesised compounds can bind to VEGFR-2 and to determine the drug-likeness profiling of these derivatives. The results revealed that compounds 23a, 23i, 23j, 23l, and 23n displayed the highest antiproliferative activities against the two cell lines with IC₅₀ values ranging from 6.4 to 19.4 µM. Furthermore, compounds 23a, 23d, 23h, 23i, 23j, 23l, 23 m, and 23n showed the highest VEGFR-2 inhibitory activities with IC₅₀ values ranging from 3.7 to 11.8 nM, comparing to sorafenib (IC₅₀ = 3.12 nM). Moreover, compound 23j arrested the HepG2 cell growth at the G2/M phase and induced apoptosis by 40.12% compared to the control cells (7.07%). As well, such compound showed a significant increase in the level of caspase-3 (1.36-fold), caspase-9 (2.80-fold), and BAX (1.65-fold), and exhibited a significant decrease in Bcl-2 level (2.63-fold).     

Absolute configuration of (+)-cis-2,3-dihydro-2-[(methylamino)methyl]-1- [4-(trifluoromethyl)phenoxy]-1H-indene hydrochloride,a chiral serotonin uptake inhibitor

The absolute configuration of (+)-cis-2,3-dihydro-2[(methylamino)methyl]-1-[4-(trifluoromethyl)pheno<y]-1H-indene hydrochloride, the more active enantiomer of a new serotonin inhibitor, was established as 1S,2S. This assignment was based on the application of the benzene sector and chirality rules to the interpretation of the inhibitor's circular dichroism spectrum and the spectra of other related chiral 1-substituted 2,3-dihydro-1H-indenes. © 1993 Wiley-Liss, Inc.     

[3H]N-[1-(2-Thienyl)cyclohexyl]-3,4-Piperidine ([3H]TCP) Binding in Human Frontal Cortex: Decreases in Alzheimer-Type Dementia

We studied [3H]N-[1-(2-thienyl)cyclohexyl]-3,4-piperidine [( 3H]TCP) binding to human frontal cortex obtained at autopsy from 10 histologically normal controls and eight histopathologically verified cases with Alzheimer-type dementia (ATD). Extensively washed membrane preparations were used to minimize the effects of endogenous substances. In ATD frontal cortex, the total concentration (Bmax) of [3H]TCP binding sites was significantly reduced by 40-50%. The apparent dissociation constant (KD) values showed no significant change. The reduction in binding capacity was also apparent in Triton X-100-treated membrane preparations, and there was a linear correlation between the number of [3H]TCP binding sites and that of N-methyl-D-aspartate (NMDA)-sensitive [3H]glutamate binding sites. [3H]TCP binding sites spared in ATD brains retained the affinity for the ligand and the reactivity to NMDA, L-glutamate, and glycine. These results suggest that the primary change in NMDA receptor-ion channel complex in ATD brains is the reduction of its number, possibly reflecting the loss of neurons bearing these receptor complexes, and that the functional linkage within the receptor complexes spared in ATD brains remains normal.     

Chemopreventive potential of 3-[2,6-bis(4-fluorophenyl)-3-methylpiperidin-4-ylideneamino]-2-thioxoimidazolidin-4-one on 7,12-dimethylbenz[a]anthracene (DMBA) induced hamster buccal pouch carcinogenesis

In the present work, a new bis heterocyclic compound comprising both the piperidone and thiohydantoin nuclei namely 3-[2,6-bis(4-fluorophenyl)-3-methylpiperidin-4-ylideneamino]-2-thioxoimidazolidin-4-one was synthesised and characterised with the help of mp, elemental analysis, FT-IR, MS and one-dimensional NMR (¹H and ¹³C) spectra. The inhibitory effect of 3-[2,6-bis(4-fluorophenyl)-3-methylpiperidin-4-ylideneamino]-2-thioxoimidazolidin-4-one on 7,12-dimethylbenz[a]anthracene (DMBA) induced buccal pouch carcinogenesis was investigated in Syrian male hamsters. All the hamsters that were painted with DMBA on their buccal pouches for 14 weeks developed squamous cell carcinoma. Administration of 3-[2,6-bis(4-fluorophenyl)-3-methylpiperidin-4-ylideneamino]-2-thioxoimidazolidin-4-one effectively suppressed the oral carcinogenesis initiated with the DMBA as revealed by a reduced incidence of neoplasms. Lipid peroxidation, glutathione (GSH) content and the activities of glutathione peroxidase (GPx), glutathione S-transferase (GST) were used to biomonitor the chemopreventive potential of 3-[2,6-bis(4-fluorophenyl)-3-methylpiperidin-4-ylideneamino]-2-thioxoimidazolidin-4-one. Lipid peroxidation was found to be significantly decreased, whereas GSH, GPx, GST and GGT were elevated in the oral mucosa of tumour bearing animals. Our data suggest that 3-[2,6-bis(4-fluorophenyl)-3-methylpiperidin-4-ylideneamino]-2-thioxoimidazolidin-4-one may exert its chemopreventive effects in the oral mucosa by modulation of lipid peroxidation, antioxidants and detoxification systems.     

Enantioselective degradation of the herbicide mecoprop [2-(2-methyl-4-chlorophenoxy) propionic acid] by mixed and pure bacterial cultures

Abstract A consortium of three bacteria was isolated from top soil through their capacity to utilise the chlorinated, aromatic herbicide mecoprop as a single growth substrate. The consortium constituted a tight association of Alcaligenes denitrificans, Pseudomonas glycinea and Pseudomonas marginalis . The culture exclusively degraded the ( R )-(+)-isomer of the herbicide while the ( S )-(−)-enantiomer remained unaffected. The mecoprop-degrading community could also degrade 2,4-dichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid and racemic 2-phenoxypropionic acid. Initially, no single member of the consortium was able to degrade mecoprop as a pure culture but after prolonged incubation, A. denitrificans was able to grow on the herbicide as the sole source of carbon and energy.     

Determination of 1-[5-(2-cyclopropyl-5,7-dimethyl-imidazo[4,5-b]pyridin-3-ylmethyl)thiophen-2-yl]cyclopent-3-enecarboxylic acid (CP-191,166), an angiotensin II antagonist, in dog and rat plasma by high-performance liquid chromatography

A simple and precise high-performance liquid chromatographic (HPLC) assay was developed and validated for the determination of a novel angiotensin II antagonist, 1-[5-(2-cyclopropyl-5,7-dimethyl-imidazo[4,5-b]pyridin-3-ylmethyl)thiopen-2-yl)cyclopent-3-enecarboxylic acid (CP-191,166, I), in dog and rat plasma. The internal standard (II, a saturated derivative of I) and analyte were extracted by liquid-liquid extraction using methyl tert.-butyl ether. Samples were analyzed by reversed-phase HPLC using a Zorbax C₈ narrow-bore column with ultraviolet detection at 289 nm. The quantitation limit of I was 10 ng/ml and the calibration curve was linear over the range of 0.01–10.0 μg/ml (r²>0.99). In dog and rat plasma, intra- and inter-assay precision ranged from 0.00 to 3.36% and 0.00 to 4.95%, respectively. The average recoveries were similar (73%) for both I and II and the upper limit of quantification of I can be as high as 500 μg/ml. The method described has been successfully applied to the quantification of I in about 2000 dog and rat plasma samples over a nine-month period.     

3-[2-Amino-2-imidazolin-4(5)-yl]alanine (enduracididine) and 2-[2-amino-2-imidazolin-4(5)-yl] acetic acid in seeds of Lonchocarpus sericeus

3-[2-Amino-2-imidazolin-4(5)-yl]alanine (enduracididine) and 2-[2-amino-2-imidazolin-4(5)-yl] acetic acid have been isolated from seeds of Lonchocarpus sericeus. The concentration of each compound was ca 0.5 % of the fresh seed weight.     

The 5-aromatic hydantoin-3-acetate derivatives as inhibitors of the tumour multidrug resistance efflux pump P-glycoprotein (ABCB1): Synthesis,crystallographic and biological studies

A series of arylpiperazine derivatives of hydantoin-3-acetate, including previously obtained 5,5-diphenylhydantoin (1–7) and new-synthesized spirofluorene-hydantoin derivatives (8–12), were investigated in the search for new inhibitors of the tumour multidrug resistance (MDR) efflux pump P-glycoprotein (P-gp, ABCB1) overexpressed in mouse T-lymphoma cells. Synthesis of new compounds (8–12) was performed. Crystal structures of two compounds (8 and 11) were determined by X-ray diffraction method. The conformations of the investigated molecules (8 and 11) in the crystalline samples are different. The bent conformation seems to be more favourable for biological activity than the extended one. The efflux pump inhibitory properties of the compounds 1–12 were evaluated in the fluorescence uptake assay using rhodamine 123 dye in mouse T-lymphoma model in vitro. Their cytotoxic action was examined, too. All compounds with methyl acetate moiety displayed high potency to inhibit the MDR efflux pump. The most active compound, methyl 2-(1-(4-(4-(2,3-dichlorophenyl)piperazin-1-yl)butyl)-5,5-diphenylhydantoin-3-yl)acetate (5), tested at 1/10 of verapamil concentration displayed the 9-fold higher P-gp inhibitory action.     

Synthesis of New Bis(pyrazolo[1,5-a]pyrimidines) Linked to Different Spacers as Potential MurB Inhibitors

An efficient protocol was adopted to efficiently prepare three new series of bis(pyrazolo[1,5-a]pyrimidines) linked to different spacers. The new bis(pyrazolo[1,5-a]pyrimidines) were prepared in 80–90 % yields by reacting the respective bis(enaminones) and 4-(4-substituted benzyl)-1H-pyrazole-3,5-diamines in pyridine at reflux temperature for 5–7 h. The new products showed a wide spectrum of antibacterial activity against six different bacterial strains. In general, propane- and butane-linked bis(pyrazolo[1,5-a]pyrimidines), which are attached to 3-(4-methyl- or 4-methoxybenzyl) units, had the best antibacterial activity with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values up to 2.5 and 5.1 μM, respectively. Additionally, the previous products demonstrated promising MurB inhibitory activity with IC₅₀ values up to 7.2 μM.     

Novel 4-(2-pyrimidinylamino)benzamide derivatives as potent hedgehog signaling pathway inhibitors

A series of novel hedgehog signaling pathway inhibitors have been designed and synthesized based on our previously reported scaffold of 4-(2-pyrimidinylamino)benzamide. The Hh signaling pathway inhibitory activities were evaluated by Gli-luciferase reporter method and most compounds showed more potent inhibitory activities than vismodegib. Three compounds were picked out to evaluated in vivo for their PK properties, and compound 23b bearing a 2-pyridyl A-ring and (morpholin-4-yl)methylene at 3-position of D-ring demonstrated satisfactory PK properties. This study suggested the 4-(2-pyrimidinylamino)benzamides were a series of potent Hh signaling pathway inhibitors, deserving to further structural optimization.