Synthesis and antitumor activity of model cyclopentene-[g]annelated isoindigos.

A set of cyclopenten-[g]annelated isoindigos (5a-g) has been prepared and tested for their in vitro antiproliferative activities against MCF-7 and HL60 cells. Among, the N-1-methyl-5'-nitro derivative (5g) displayed the highest activity against HL60 cells (IC50 = 67 nM) and acted as the most potent Flt3 inhibitor. Compounds 5d-g exhibited moderate activity against MCF-7 (IC50 = 50-80 µM).

Thermodynamic control synthesis of spiro[oxindole-3,3'-pyrrolines] via 1,4-dipolar cycloaddition utilizing imidazo[1,5-a]quinoline.

A series of novel 2-(quinolin-2-yl)-spiro[oxindole-3,3'-pyrrolines] were synthesized by one-pot three-component reaction involving dimethyl acetylenedicarboxylate, 1-phenylimidazo[1,5-a]quinoline and N-alkylisatins in chloroform at ∼60 °C for 24 h. Structures of these new spiro derivatives were deduced from HRMS and NMR spectral data. A plausible mechanism for the observed thermodynamic control pathway is presented herewith. Interestingly, the spiro adduct, derived from 5-chloro-1-methylisatin, exhibited excellent antiproliferative activity on MCF7, A549 and Hela human cell lines (IC50 ≃ 7 µM).

8-Amino-7-(aryl/hetaryl)fluoroquinolones. An emerging set of synthetic antibacterial agents.

This study reports the synthesis of seven new 8-amino-7-(aryl/hetaryl)fluoroquinolones and their antibacterial activity against 10 bacteria associated with microbial infections and foodborne illnesses. These fluoroquinolones are prepared via the reactions of selected aryl(hetaryl)boronic acids with ethyl-7chloro-6-fluoro-8-nitroquinolone-3-carboxylate, under Suzuki-Miyaura cross-coupling conditions. Nitro group reduction of the latter resulted in the corresponding 8-aminoquinolone-3-esters which upon hydrolysis formed the respective 8-amino-7-(aryl/hetaryl)-quinolone-3-carboxylic acids. The latter compounds were tested against selected Gram-negative bacteria (Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumonia) and Gram-positive bacteria (Enterococcus feacalis, Listeria monocytogenes, Streptococcus agalactiae, Staphylococcus epidermidis, and Staphylococcus aureus). The tested fluoroquinolones showed a significant antimicrobial activity against most of the tested bacterial strains. The antimicrobial activity of some of the tested compounds were comparable to or higher than a wide range of standard antibiotics including ampicillin, ciprofloxacin, and imipenem. The results highlight the new synthesized 8-amino-7-(aryl/hetaryl)fluroquinolones as promising candidates for new antimicrobial drugs to treat bacterial infections. This study highlights that the newly synthetic 8-amino-7-(aryl/hetaryl)fluroquinolones are promising candidates for new antimicrobial drugs to treat human diseases including foodborne illnesses.

Thiophene ring-opening reactions VI. Attempted cyclization towards [fused]-tricyclic system involving a thiolate anion and suitably located electrophilic carbon.

Model α-chloro-ß-nitrothieno[2,3-c]pyridazines incorporating N1-(aryl) entity appended with ortho-methoxycarbonyl or trifluoromethyl group were prepared via intramolecular cyclization of their respective N-arylhydrazone precursors. Interaction of these substrates with N'-(p-fluorophenyl)benzothiohydrazide, in the presence of NEt3, furnished the respective 1,3,4-thiadiazoline-pyridazine thiolate hybrids that were S-methylated to produce the corresponding "sulfanyl" derivatives. Their structures were deduced from spectral data, and confirmed by single-crystal X-ray diffraction.

Thiophene Ring-opening Reactions III: One-Pot Synthesis and Antitumor Activity of 1,3,4-Thiadiazoline-Benzothiazolo[3,2-b]pyridazine Hybrids†.

INTRODUCTION: The preparation of model 6-chloro-5-nitrothieno[2,3-c]pyridazines incorporating (2'-halo-5'-nitrophenyl) entity is described. Interaction of these substrates with N'-(aryl)benzothiohydrazides, in the presence of triethylamine, followed a formal [4+1] annulation, furnishing the respective 1,3,4-thiadiazoline-benzothiazolo [3,2-b]pyridazine hybrids directly. This one-pot synthesis implies thiophene ring-opening and two consecutive intramolecular cyclizations. The structures of the synthesized new hybrids are supported by MS, NMR, and IR spectral data and further confirmed by single-crystal X-ray diffraction. These hybrids exhibit antiproliferative activity with notable selectivity against solid tumor cell lines (IC50: 4-18 µM). AIMS: This study aimed at exploring the scope and applicability of thiophene ring-opening reaction towards the synthesis of new thiadiazoline-[fused]tricyclic conjugates. BACKGROUND: α-Chloro-ß-nitrothienopyridazine underwent ring-opening upon reacting with N'-(aryl)benzothiohydrazides generating 1,3,4-thiadiazoline-benzothiazolo[3,2-b]pyridazines. OBJECTIVE: This new thiophene ring-opening reaction is applied to the one-pot synthesis of thiadiazoline-benzothiazolo[3,2-b]pyridazine couples. METHOD: A direct interaction of α-chloro-ß-nitrothienopyridazine with N'-(aryl)benzothio-hydrazide at room temperature for 1-2 h occurred. RESULT: a-Chloro-ß-nitrothieno[2,3-c]pyridazines are suitable substrates for the facile synthesis of thiadiazoline-benzothiazolo[3,2-b]pyridazine hybrids. CONCLUSION: This novel ring-opening reaction proceeds via formal [4+1] annulation and provides a versatile approach to various conjugated and/or fused five-membered heterocycles.

Synthesis and Cytotoxicity of Thieno[2,3-b]Pyridine Derivatives Toward Sensitive and Multidrug-Resistant Leukemia Cells.

A new series of substituted ethyl 7-cyclopropyl-2-(2-aryloxo)-3-nitro-4-oxo-4,7-dihydrothieno[2,3-b]pyridine-5-carboxylates 3a-e were prepared by utilizing ethyl 2-chloro-7-cyclopropyl-3-nitro-4-oxo-4,7-dihydrothieno[2,3-b]pyridine-5-carboxylate (1) and replacing of the 2-chlorine with anions obtained from phenol (2a), salicylaldehyde derivatives 2b-d or thiophenol (2e), leading to the respective ethyl 7-cyclopropyl-2-(2-aryloxo)-3-nitro-4-oxo-4,7-dihydrothieno[2,3-b]pyridine-5-carboxylates 3a-e. The new compounds were evaluated for their in vitro cytotoxicity towards sensitive CCRF-CEM and multidrug-resistant CEM/ADR5000 leukemia cells. The screening revealed that compounds 3a, 3b, and 3e inhibited the growth of both cell lines. Compound 3b, with a phenol moiety, exhibited the highest growth inhibitory activity against CEM/ADR5000 and CCRF-CEM cells with IC50 values 4.486 ± 0.286 and 2.580 ± 0.550 µM, respectively. Collectively, the presented results demonstrate that the synthesized thieno[2,3-b]pyridines warrant further exploration for potential use as anti-cancer agents.

Coumarin derivatives as acetyl- and butyrylcholinestrase inhibitors: An in vitro, molecular docking, and molecular dynamics simulations study.

Alzheimer's disease is an irreversible and progressive brain disease that can cause problems with memory and thinking skills. It is characterized by loss of cognitive ability and severe behavioral abnormalities, and could lead to death. Cholinesterases (ChEs) play a crucial role in the control of cholinergic transmission, and subsequently, the acetylcholine level in the brain is upgraded by inhibition of ChEs. Coumarins have been shown to display potential cholinesterase inhibitory action, where the aromatic moiety has led to the design of new candidates that could inhibit Aß aggregation. Accordingly, the present work is an in vitro activity, along with docking and molecular dynamics (MD) simulation studies of synthesized coumarin derivatives, to explore the plausible binding mode of these compounds inside the cholinesterase enzymes. For this purpose, a series of previously prepared N1-(coumarin-7-yl) derivatives were screened in vitro for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities. The assayed compounds exhibited moderate inhibitory activity against AChE, with IC50 values ranging from 42.5 ± 2.68 to 442 ± 3.30 µM. On the other hand, the studied compounds showed remarkable activity against BChE with IC50 values ranging from 2.0 ± 1.4 nM to 442 ± 3.30 µM. In order to better understand the ligand binding site interaction of compounds and the stability of protein-ligand complexes, a molecular docking with molecular dynamics simulation of 5000 ps in an explicit solvent system was carried out for both cholinesterases. We concluded that the tested coumarin derivatives are potential candidates as leads for potent and efficacious ChEs inhibitors.

Synthesis and Structure-Activity Relationship; Exploration of some Potent Anti-Cancer Phenyl Amidrazone Derivatives.

BACKGROUND: Amidrazones have been reported to have significant anti-tumor properties against several cancer cell lines. OBJECTIVES: The current project aims to profile the structure-anticancer activity relationship of phenyl-amidrazons. METHODS: Fifteen phenyl-amidrazone-piperazine derivatives were prepared and tested against four cancer cell lines (leukemia, prostate, breast and colon cancers). RESULTS: Six compounds illustrated low micromolar anticancer IC50 values, while the remaining compounds were either inactive or of moderate potencies. All compounds were virtually nontoxic against normal fibroblast cells. CONCLUSION: Docking into the oncogenic kinase bcr/abl illustrated the critical importance of (i) phalogen substituent on the ligand's phenyl ring and (ii) the presence of positive ionizable moiety at the ligand's piperazine fragment for anticancer activity.

The anticancer activity of the substituted pyridone-annelated isoindigo (5'-Cl) involves G0/G1 cell cycle arrest and inactivation of CDKs in the promyelocytic leukemia cell line HL-60.

BACKGROUND/AIMS: The antileukemic potential of isoindigos make them desired candidates for understanding their mechanism of action. We have recently synthesized a novel group of pyridone-annelated isoindigos and identified the derivative 5'-Cl that is cytotoxic to various cancer cell lines. In the present study, we analyzed the effect of this compound on cell cycle of the promyelocytic leukemia cell line HL-60. METHODS: HL-60 cells were treated with 5'-Cl and its effect on cell cycle stages were determined by flow cytometry. Expression of cyclins, cyclin dependent kinases (CDKs) and cyclin kinase inhibitors (CKIs) were determined by Western blotting, and activation of CDKs was studied using kinase assays. RESULTS: 5'-Cl remarkably arrested cell cycle in HL-60 cells at the G0/G1 phase in a dose and time-dependent manner. Furthermore, 5'-Cl treatment significantly inhibited expression of D-cyclins, CDK2 and CDK4 and suppressed phosphorylation of the retinoblastoma protein Rb, whereas it increased the level of CKI p21. Molecular modelling experiments show that 5'-Cl may compete with ATP for binding to the catalytic subunit of CDK2 and CDK4 that could lead to inhibition of these enzymes. Indeed, 5'-Cl inhibited the kinase activity of CDK2 and CDK4 both in cell free systems and in treated cells. 5'-Cl also inhibited cell cycle progression in several other tumor cell lines. CONCLUSION: We demonstrate the potent inhibitory effects of 5'-Cl on HL-60 cells could be mediated by arresting cells in the G0/G1 phase.

The pyridone-annelated isoindigo (5'-Cl) induces apoptosis, dysregulation of mitochondria and formation of ROS in leukemic HL-60 cells.

BACKGROUND/AIMS: In our quest to develop an isoindigo with improved efficacy and bioavailability, we recently synthesized a series of novel substituted pyridone-annelated isoindigo and evaluated their antiproliferative effects. We identified the compound [(E)-1-(5'-Chloro-2'-oxoindolin-3'-ylidene)-6-ethyl-2,3,6,9-tetrahydro-2,9-dioxo-1H-pyrrolo[3,2-f] quinoline-8-carboxylic acid], abbreviated as 5'-Cl, which shows selective antiproliferative activities against various cancer cell lines mediated through apoptosis. Here we have investigated the molecular mechanisms underlying the apoptotic activity of 5'-Cl in the human promyelocytic leukemia HL-60 cells. METHODS: We employed different methods to determine the apoptotic pathways triggered by 5'-Cl in HL-60 cells, using flow cytometry, nuclear staining, caspases activation, mitochondria functioning, generation of reactive oxygen species (ROS) and Western blotting techniques. RESULTS: Low concentrations (1-8 µM) of 5'-Cl inhibited the growth of HL-60 cells in a dose and time-dependent manner. Cytotoxicity of this compound is found to be mediated by a caspase-dependent apoptosis. Also, there were indications of caspase independent apoptosis as z-VAD-FMK failed to fully rescue the cells from 5'-Cl-induced apoptosis. In addition, the compound triggered generation of Reactive Oxygen Species (ROS), caused depolarization of the mitochondrial inner membrane, decreased the level of cellular ATP, modulated the expression and phosphorylation of Bcl-2 leading to loss of its association with Bax and increased the release of cytochrome c to the cytosol of treated cells. The effects of 5'-Cl on mitochondria and apoptosis were substantially blocked in the presence of a combination between z-VAD-FMK and either of the ROS scavenger N-acetyl-L-cysteine (NAC) or pyrrolidine dithiocarbamate (PDTC). CONCLUSION: We demonstrated that the growth inhibitory effects of 5'-Cl in HL-60 cells involve multiple pathways of apoptosis and dysregulation of mitochondrial functions.

Antiproliferative activity of the isoindigo 5'-Br in HL-60 cells is mediated by apoptosis, dysregulation of mitochondrial functions and arresting cell cycle at G0/G1 phase.

Our new compound, 5'-Br [(E)-1-(5'-bromo-2'-oxoindolin-3'-ylidene)-6-ethyl-2,3,6,9-tetrahydro-2,9-dioxo-1H-pyrrolo[3,2-f]quinoline-8-carboxylic acid], had shown strong, selective antiproliferative activity against different cancer cell lines. Here, we aim to comprehensively characterize the mechanisms associated with its cytotoxicity in the human promyelocytic leukemia HL-60 cells. We focused at studying the involvement of apoptotic pathway and cell cycle effects. 5'-Br significantly inhibited proliferation by inducing caspase-dependent apoptosis. Involvement of caspase independent mechanism is also possible due to observed inability of z-VAD-FMK to rescue apoptotic cells. 5'-Br was found to trigger intrinsic apoptotic pathway as indicated by depolarization of the mitochondrial inner membrane, decreased level of cellular ATP, modulated expression and phosphorylation of Bcl-2 leading to loss of its association with Bax, and increased release of cytochrome c. 5'-Br treated cells were found arrested at G0/G1 phase with modulation in protein levels of cyclins, dependent kinases and their inhibitors. Expression and enzymatic activity of CDK2 and CDK4 was found inhibited. Retinoblastoma protein (Rb) phosphorylation was also inhibited whereas p21 protein levels were increased. These results suggest that the antiproliferative mechanisms of action of 5'-Br could involve apoptotic pathways, dysregulation of mitochondrial functions and disruption of cell cycle checkpoint.

Synthesis and antibacterial activity of some novel 4-oxopyrido[2,3-a]phenothiazines.

A series of substituted 4-oxopyrido[2,3-a]phenothiazine-3-carboxylic acids (6a-d) were prepared via cyclization of the corresponding ethyl 7-(arylthioxy)-8-nitro(or azido)-4-oxoquinoline-3-carboxylates (3a-d/4a-d), followed by hydrolysis of the resultant esters (5a-d). Among these tetracyclics, compound 6a with unsubstituted terminal benzo-ring D was the most active against representative Gram-positive and Gram-negative bacterial strains. These compounds were also active against methicillin-resistant Staphylococcus aureus (MRSA), with very low toxicity to normal cells. Virtual screening using ligand-protein docking modeling predicted that the compounds 6a-d are potential inhibitors of the topoisomerase IV enzyme and that hydrophobic interactions and hydrogen bonds are the major molecular interactions between these compounds and the residues of the active site of topoisomerase IV.

A new efficient route to 7-aryl-6-fluoro-8-nitroquinolones as potent antibacterial agents.

A series of 7-aryl-6-fluoro-8-nitroquinolones (6a-e) were synthesized through a novel, simple and clean synthetic procedure, through a Suzuki-Miyaura reaction. The target compounds were evaluated in vitro for their antimicrobial properties against bacterial and fungal strains. All of them showed antibacterial activity higher than the activity of ciprofloxacin, both towards Gram positive Bacillus subtilis and Staphylococcus aureus, and Gram negative Haemophilus influenzae strains. Compound 6d, containing the trisubstituted 7-aryl moiety, emerged as the most active quinolone derivative with MIC values ranging from 0.00007 µg/mL to 0.015 µg/mL.

Synthesis and biological evaluation of new pyridone-annelated isoindigos as anti-proliferative agents.

A selected set of substituted pyridone-annelated isoindigos 3a-f has been synthesized via interaction of 5- and 6-substituted oxindoles 2a-f with 6-ethyl-1,2,9-trioxopyrrolo[3,2-f]quinoline-8-carboxylic acid (1) in acetic acid at reflux. Among these isoindigos, the 5'-chloro and 5'-bromo derivatives 3b and 3d show strong and selective antiproliferative activities against a panel of human hematological and solid tumor cell-lines, but not against noncancerous cells, suggesting their potential use as anticancer agents. In all the tested cell lines, compound 3b was a 25%-50% more potent inhibitor of cell growth than 3d, suggesting the critical role of the substitution at 5'-position of the benzo-ring E. The IC50 values after 48 hours incubation with the 5'-chloro compound 3b were 6.60 µM in K562, 8.21 µM in THP-1, 8.97 µM in HepG2, 11.94 µM in MCF-7 and 14.59 µM in Caco-2 cancer cells, while the IC50 values in noncancerous HEK-293 and L-929 were 30.65 µM and 40.40 µM, respectively. In addition, compound 3b induced higher levels apoptosis in K562 cells than 3d, as determined by annexin V/7-AAD flowcytometry analysis. Therefore, further characterization of the antitproliferative mechanisms of compounds 3b and 3d may provide a novel chemotherapeutic agents.

Synthesis and antitumor activities of some new N1-(flavon-6-yl)amidrazone derivatives.

A new series of N1-(flavon-6-yl)amidrazones were synthesized by reacting the hydrazonoyl chloride derived from 6-aminoflavone with the appropriate sec-cyclic amines. The antitumor activities of these compounds were evaluated on breast cancer (MCF-7) and leukemic (K562) cell lines. Among the compounds tested, the N-morpholine derivative was the most active against the MCF-7 and K562 cell lines, with IC50 values of 5.18 and 2.89 µM, respectively. Our docking studies showed that the N-morpholino derivative fits and blocks the oncogenic tyrosine kinases bcr/abl and epidermal growth factor receptor (EGFR) in a similar fashion to that of the potent anticancer agent imatinib.

Design synthesis and antibacterial activity studies of new thiadiazoloquinolone compounds.

Abstract New 9-(alkyl/aryl)-4-fluoro-6-oxo[1,2,5]thiadiazolo[3,4-h]quinoline-5-carboxylic acids and their esters were designed and synthesized. A detailed discussion of the reactions utilized in the preparation of the intermediate and target compounds is reported. All the newly synthesized compounds were fully characterized using all the physico-chemical means needed. All the intermediates and the final esters and acids were tested against bacterial and fungal strains. The acids 25a and 25c proved to be very active against Gram positive and Gram negative bacteria with MIC 0.15-3 µg/mL. The structure-activity relationship of antibacterial thiadiazoloquinolones shows that compounds 25a and 25c are twice less potent than the corresponding cyclopropyl derivative 16. Therefore, the cyclopropyl moiety on N-9 seems to be the most suitable substituent.

Synthesis and biological activity assays of some new N1-(flavon-7-yl)amidrazone derivatives and related congeners.

A series of new N1-(flavon-7-yl)amidrazones incorporating N-piperazines and related congeners were synthesized by reacting the hydrazonoyl chloride derived from 7-aminoflavone and 7-amino-2-methylchromen-4-one with the appropriate piperazine. The chemical structures of the newly prepared compounds were confirmed by elemental analyses, (1)H NMR, (13)C NMR, and ESI-HRMS spectral data. The antitumor activity of these compounds was evaluated on breast cancer (MCF-7 and T47D) and Leukemic (K562) cell lines by a cell viability assay utilizing the tetrazolium dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Although with varying degrees, a significant growth inhibitory and cytotoxic effect was observed on all three cancer cell lines. Among the compounds tested compounds, 5a, 15a, and 18b, were the most active against T47D cell line with IC(50) values of 1.42, 1.92, and 2.92 µM, respectively. By using other cancer cell lines and with further characterization of their biological mechanism of action, these compounds could prove to be useful candidates as anticancer drugs.

Synthesis and biological activity of some 3-(4-(substituted)-piperazin-1-yl)cinnolines.

A new series of 6-substituted-4-methyl-3-(4-arylpiperazin-1-yl)cinnolines 8-10 were synthesized as potential antifungal agents via intramolecular cyclization of the respective 1-(2-arylhydrazono)-1-(4-arylpiperazin-1-yl)propan-2-ones 5-7, mediated by polyphosphoric acid (PPA). The amidrazones themselves were synthesized via direct interaction of the appropriate hydrazonoyl chlorides 4a-d with the corresponding N-substituted piperazine in the presence of triethylamine. The structures of the new prepared compounds were confirmed by elemental analyses, (1)H-NMR, (13)C-NMR, and ESI-HRMS spectral data. The antitumor, antibacterial, and antifungal activity of the newly synthesized compounds was evaluated.

Synthesis, and antitumor activity of some N1-(coumarin-7-yl) amidrazones and related congeners.

A series of new N1-(coumarin-7-yl)amidrazones incorporating N-piperazines and related congeners were synthesized by reacting the hydrazonoyl chloride derived from 7-amino-4-methylcoumarin with the appropriate piperazines. The chemical structures of the newly prepared compounds were supported by elemental analyses, ¹H-NMR, ¹³C-NMR, and ESI-HRMS spectral data. The antitumor activity of the newly synthesized compounds was evaluated. Among all the compounds tested, 7-{2-[1-(4-(1-benzyl-2-ethyl-4-nitro-1H-imidazol-5-yl)piperazin-1-yl)-2-oxopropylidene]hydrazinyl}-4-methyl-2H-chromen-2-one (3n) was the most potent against MCF-7 and K562 cells, with IC50 values of 20.2 and 9.3 µM, respectively.

Synthesis and biological evaluation of tetracyclic thienopyridones as antibacterial and antitumor agents.

A facile synthesis of model 4-oxopyrido[3',2':4,5]thieno[3,2-b]indole-3-carboxylic acids 9a-e was achieved via Stille arylation of 2-chloro-3-nitro-4-oxothieno[2,3-b]pyridine-5-carboxylate and a subsequent microwave-assisted phosphite-mediated Cadogan reaction. The new compounds were tested for their in vitro antimicrobial and antiproliferative activity. Compounds 9a-c and 9e exhibited very high potency against Gram positive Bacillus subtilis and Bacillus megaterium at concentrations 0.000015-0.007 µg/mL. They also displayed excellent activity towards other Gram positive bacilli and staphylococci and Gram negative Haemophilus influenzae, being in most cases superior or equal to commercial fluoroquinolones. Both 9a and 9c were inhibitors of the DNA gyrase activity. As concerns antitumor properties, compounds 9b-e showed growth inhibition of MCF-7 breast tumor and A549 non-small cell lung cancer cells with IC(50) 1.6-2.8 µM and 2.6-6.9 µM, respectively, coupled with absence of cytotoxicity towards normal cells. These compounds are promising as dual acting chemotherapeutics.