2-Substituted thienotetrahydropyridine derivatives: Allosteric ectonucleotidase inhibitors.

The antithrombotic prodrugs ticlopidine and clopidogrel are thienotetrahydro-pyridine derivatives that are metabolized in the liver to produce thiols that irreversibly block adenosine diphosphate (ADP)-activated P2Y12 receptors on thrombocytes. In their native, nonmetabolized form, both drugs were reported to act as inhibitors of ectonucleoside triphosphate diphosphohydrolase-1 (NTPDase1, CD39). CD39 catalyzes the extracellular hydrolysis of nucleoside tri- and diphosphates, mainly adenosine 5'-triphosphate (ATP) and ADP, yielding adenosine monophosphate, which is further hydrolyzed by ecto-5'-nucleotidase (CD73) to produce adenosine. While ATP has proinflammatory effects, adenosine is a potent anti-inflammatory, immunosuppressive agent. Inhibitors of CD39 and CD73 have potential as novel checkpoint inhibitors for the immunotherapy of cancer and infection. In the present study, we investigated 2-substituted thienotetrahydropyridine derivatives, structurally related to ticlopidine, as CD39 inhibitors. Due to their substituent on the 2-position, they will not be metabolically transformed into reactive thiols and can, therefore, be expected to be devoid of P2Y12 receptor-antagonistic activity in vivo. Several of the investigated 2-substituted thienotetrahydropyridine derivatives showed concentration-dependent inhibition of CD39. The most potent derivative, 32, showed similar CD39-inhibitory potency to ticlopidine, both acting as allosteric inhibitors. Compound 32 showed an improved selectivity profile: While ticlopidine blocked several NTPDase isoenzymes, 32 was characterized as a novel dual inhibitor of CD39 and CD73.

Synthesis of Novel Methyl 3-(hetero)arylthieno[3,2-b]pyridine-2-carboxylates and Antitumor Activity Evaluation: Studies In Vitro and In Ovo Grafts of Chick Chorioallantoic Membrane (CAM) with a Triple Negative Breast Cancer Cell Line.

A series of novel functionalized methyl 3-(hetero)arylthieno[3,2-b]pyridine-2-carboxylates 2a-2h were synthesized by C-C Pd-catalyzed Suzuki-Miyaura cross-coupling of methyl 3-bromothieno[3,2-b]pyridine-2-carboxylate with (hetero)aryl pinacol boranes, trifluoro potassium boronate salts or boronic acids. Their antitumoral potential was evaluated in two triple negative breast cancer (TNBC) cell lines-MDA-MB-231 and MDA-MB-468, by sulforhodamine B assay. Their effects on the non-tumorigenic MCF-12A cells were also evaluated. The results demonstrated that three compounds caused growth inhibition in both TNBC cell lines, with little or no effect against the non-tumorigenic cells. The most promising compound was further studied concerning possible effects on cell viability (by trypan blue exclusion assay), cell proliferation (by bromodeoxyuridine assay) and cell cycle profile (by flow cytometry). The results demonstrated that the GI50 concentration of compound 2e (13 µM) caused a decreased in MDA-MB-231 cell number, which was correlated with a decreased in the % of proliferating cells. Moreover, this compound increased G0/G1 phase and decreased S phases, when compared to control cells (although was not statistic significant). Interestingly, compound 2e also reduced tumor size using an in ovo CAM (chick chorioallantoic membrane) model. This work highlights the potential antitumor effect of a novel methyl 3-arylthieno[3,2-b]pyridine-2-carboxylate derivative.

A thienopyridine, CB-20, exerts diuretic activity by inhibiting urea transporters.

Urea transporters (UTs) are transmembrane proteins selectively permeable to urea and play an important role in urine concentration. UT-knockout mice exhibit the urea-selective urine-concentrating defect, without affecting electrolyte balance, suggesting that UT-B inhibitors have the potential to be developed as novel diuretics. In this study, we characterized a novel compound 5-ethyl-2-methyl-3-amino-6-methylthieno[2,3-b]pyridine-2,5-dicarboxylate (CB-20) with UT inhibitory activity as novel diuretics with excellent pharmacological properties. This compound was discovered based on high-throughput virtual screening combined with the erythrocyte osmotic lysis assay. Selectivity of UT inhibitors was assayed using transwell chambers. Diuretic activity of the compound was examined in rats and mice using metabolic cages. Pharmacokinetic parameters were detected in rats using LC-MS/MS. Molecular docking was employed to predict the potential binding modes for the CB-20 with human UT-B. This compound dose-dependently inhibited UT-facilitated urea transport with IC50 values at low micromolar levels. It exhibited nearly equal inhibitory activity on both UT-A1 and UT-B. After subcutaneous administration of CB-20, the animals showed polyuria, without electrolyte imbalance and abnormal metabolism. CB-20 possessed a good absorption and rapid clearance in rat plasma. Administration of CB-20 for 5 days did not cause significant morphological abnormality in kidney or liver tissues of rats. Molecular docking showed that CB-20 was positioned near several residues in human UT-B, including Leu364, Val367, and so on. This study provides proof of evidence for the prominent diuretic activity of CB-20 by specifically inhibiting UTs. CB-20 or thienopyridine analogs may be developed as novel diuretics.

4-Arylthieno[2,3-b]pyridine-2-carboxamides Are a New Class of Antiplasmodial Agents.

Malaria causes hundreds of thousands of deaths every year, making it one of the most dangerous infectious diseases worldwide. Because the pathogens have developed resistance against most of the established anti-malarial drugs, new antiplasmodial agents are urgently needed. In analogy to similar antiplasmodial ketones, 4-arylthieno[2,3-b]pyridine-2-carboxamides were synthesized by Thorpe-Ziegler reactions. In contrast to the related ketones, these carboxamides are only weak inhibitors of the plasmodial enzyme PfGSK-3 but the compounds nevertheless show strong antiparasitic activity. The most potent representatives inhibit the pathogens with IC50 values in the two-digit nanomolar range and exhibit high selectivity indices (>100).

In-flow photooxygenation of aminothienopyridinones generates iminopyridinedione PTP4A3 phosphatase inhibitors.

A continuous flow photooxygenation of 7-aminothieno[3,2-c]pyridin-4(5H)-ones to produce 7-iminothieno[3,2-c]pyridine-4,6(5H,7H)-diones has been developed, utilizing ambient air as the sole reactant. N-H Imines are formed as the major products, and excellent functional group tolerance and conversion on gram-scale without the need for chromatographic purification allow for facile late-stage diversification of the aminothienopyridinone scaffold. Several analogs exhibit potent in vitro inhibition of the cancer-associated protein tyrosine phosphatase PTP4A3, and the SAR supports an exploratory docking model.

Synthesis, Docking Studies, and In Vitro Evaluation of Some Novel Thienopyridines and Fused Thienopyridine-Quinolines as Antibacterial Agents and DNA Gyrase Inhibitors.

A series of novel thienopyridines and pyridothienoquinolines (3a,b-14) was synthesized, starting with 2-thioxo-1,2-dihydropyridine-3-carbonitriles 1a and 1b. All compounds were evaluated for their in vitro antimicrobial activity against six bacterial strains. Compounds 3a,b, 4a, 5b, 6a,b, 7a, 9b, 12b, and 14 showed significant growth inhibition activity against both Gram-positive and Gram-negative bacteria compared with the reference drug. The most active compounds (4a, 7a, 9b, and 12b) against Staphylococcus aureus were also tested for their in vitro inhibitory action on methicillin-resistant Staphylococcus aureus (MRSA). The tested compounds showed promising inhibition activity, with the performance of 12b being equal to gentamicin and that of 7a exceeding it. Moreover, the most promising compounds were also screened for their Escherichia coli DNA gyrase inhibitory activity, compared with novobiocin as a reference DNA gyrase inhibitor. The results revealed that compounds (3a, 3b, 4a, 9b, and 12b) had the highest inhibitory capacity, with IC50 values of 2.26-5.87 µM (that of novobiocin is equal to 4.17 µM). Docking studies were performed to identify the mode of binding of the tested compounds to the active site of E. coli DNA gyrase B.

Identification of thienopyridine carboxamides as selective binders of HIV-1 trans Activation Response (TAR) and Rev Response Element (RRE) RNAs.

Small organic molecules that can selectively bind to RNA with specificity are relatively rare. Here we report the synthesis, biochemical and structural studies of thienopyridine carboxamide derivatives with the capacity of selectively recognizing and binding with HIV-1 TAR and RRE RNAs that are essential elements for viral replication.

Design, synthesis and docking study of pyridine and thieno[2,3-b] pyridine derivatives as anticancer PIM-1 kinase inhibitors.

A series of pyridine and thieno[2,3-b]pyridine derivatives have been designed and synthesized as anticancer PIM-1 kinase inhibitors. Thirty-seven compounds were selected by NCI to be tested initially at a single dose (10 µM) in the full NCI 60 cell line panel. Compound 5b showed potent anticancer activity and was tested twice in the five-dose assay which confirmed its potent antitumor activity (GI50 values 0.302-3.57 µM) against all tested tumor cell lines except six cell lines where they showed moderate sensitivity. This compound was sent to NCI biological evaluation committee and still under consideration for further testing. In addition, the most active anticancer compounds in each series, 5b, 8d, 10c, 13h, and 15e, were evaluated for their PIM-1 kinase inhibitory activity. Compound 8d was the most potent one with IC50 = 0.019 µM followed by 5b, 15e, 10c and 13h with IC50 values 0.044, 0.083, 0.128 and 0.479 µM respectively. Moreover, docking study of the most active compounds in PIM-1 kinase active site was consistent with the in vitro activity.

Synthesis of a Novel Series of Amino Acid Prodrugs Based on Thienopyridine Scaffolds and Evaluation of Their Antiplatelet Activity.

The thienopyridines class of drugs used as P2Y12 receptor antagonists plays a vital role in antiplatelet therapy. To further optimized this compound class, we designed and synthesized a series of amino acid prodrugs of 2-hydroxytetrahydrothienopyridine. All compounds were then evaluated for their inhibitory effect on ADP-induced platelet aggregation in rats and then ED50 and bleeding time of the most potent compounds were compared with commercial drugs. The results showed compound 5c could be a potent and safe candidate for further research.

Efficient OLEDs Fabricated by Solution Process Based on Carbazole and Thienopyrrolediones Derivatives.

Four low molecular weight compounds-three of them new, two of them with carbazole (Cz) as functional group and the other two with thienopyrroledione (TPD) group-were used as emitting materials in organic light emitting diodes (OLEDs). Devices were fabricated with the configuration ITO/PEDOT:PSS/emitting material/LiF/Al. The hole injector layer (HIL) and the emitting sheet were deposited by spin coating; LiF and Al were thermally evaporated. OLEDs based on carbazole derivatives show luminances up to 4130 cd/m², large current efficiencies about 20 cd/A and, cautiously, a very impressive External Quantum Efficiency (EQE) up to 9.5%, with electroluminescence peaks located around 490 nm (greenish blue region). Whereas, devices manufactured with TPD derivatives, present luminance up to 1729 cd/m², current efficiencies about 4.5 cd/A and EQE of 1.5%. These results are very competitive regarding previous reported materials/devices.

Selective inhibitors of Plasmodium falciparum glycogen synthase-3 (PfGSK-3): New antimalarial agents?

Plasmodium falciparum glycogen synthase kinase-3 (PfGSK-3) is one of the eukaryotic protein kinases that were identified as essential for the parasite causing malaria tropica. Although the physiological functions of PfGSK-3 are still unknown, it had been suggested as a putative target for novel antimalarial drugs. The high structural similarity of PfGSK-3 and its human orthologue HsGSK-3 makes the development of selective PfGSK-3 inhibitors a challenging task. Actually, established GSK-3 inhibitors are either unselective or are more potent for inhibition of the mammalian GSK-3. A high throughput screening campaign identified thieno[2,3-b]pyridines as a new class of PfGSK-3 inhibitors. Systematic variation of the substitution pattern at the parent scaffold led to compounds which selectively inhibited the plasmodial enzyme. These compounds also exhibited activity against erythrocyte stages of the parasites. A hypothetical explanation for the selectivity of the new antimalarial compounds was enunciated based on the results of docking a selective inhibitor into a PfGSK-3 homology model and by comparison of the results with an X-ray structure of HsGSK-3 co-crystallized with a similar but unselective compound. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases.

Donor-Acceptor-Donor Thienopyrazines via Pd-Catalyzed C-H Activation as NIR Fluorescent Materials.

A series of thienopyrazine-based donor-acceptor-donor (D-A-D) near-infrared (NIR) fluorescent compounds were synthesized through a rapid, palladium-catalyzed C-H activation route. The dyes were studied through computational analysis, electrochemical properties analysis, and characterization of their photophysical properties. Large Stokes shifts of approximately 175 nm were observed, which led to near-infrared emission. Computational evaluation shows that the origin of this large Stokes shift is a significant molecular reorganization particularly about the D-A bond. The series exhibits quantum yields of up to φ = >4%, with emission maxima ranging from 725 to 820 nm. The emission is strong in solution, in thin films, and also in isolation at the single-molecule level. Their stable emission at the single-molecule level makes these compounds good candidates for single-molecule photon sources in the near-infrared.

Synthesis and cytotoxicity of thieno[2,3-b]quinoline-2-carboxamide and cycloalkyl[b]thieno[3,2-e]pyridine-2-carboxamide derivatives.

Seventy nine derivatives of thieno[2,3-b]quinolines, tetrahydrothieno[2,3-b]quinoline, dihydrocyclopenta[b]thieno[3,2-e]pyridine, cyclohepta[b]thieno[3,2-e]pyridine and hexahydrocycloocta[b]thieno[3,2-e]pyridine were either synthesized or obtained commercially and tested for their antiproliferative activity against HCT116, MDA-MB-468 and MDA-MB-231 human cancer cell lines. The most potent eight compounds were active against all cell lines with IC50 values in the 80-250nM range. In general hexahydrocycloocta[b]thieno[3,2-e]pyridines were most active with increasing activity observed as larger cycloalkyl rings were fused to the pyridine ring.

A new antitumoral Heteroarylaminothieno[3,2-b]pyridine derivative: its incorporation into liposomes and interaction with proteins monitored by fluorescence.

The fluorescence properties of the new potent antitumoral methyl 3-amino-6-(benzo[d]thiazol-2-ylamino)thieno[3,2-b]pyridine-2-carboxylate in solution and when encapsulated in several different nanoliposome formulations were investigated. The compound exhibits very reasonable fluorescence quantum yields and a solvent sensitive emission in several polar and non-polar media, despite not being fluorescent in protic solvents. Fluorescence anisotropy measurements of the compound incorporated into liposomes revealed that this thienopyridine derivative can be carried in the hydrophobic region of the lipid membrane. Liposome formulations including this antitumor compound are nanometric in size, with a diameter lower than 130 nm and generally low polydispersity, and are promising for future drug delivery developments. The interaction of the compound with bovine serum albumin (BSA) and the multidrug resistance protein MDR1 was monitored by FRET, the compound acting as an energy acceptor. It was observed that the drug had a lower interaction with the MDR1 protein than with the native form of BSA, which is an important result regarding applications of this antitumoral drug.

Thieno[2,3-b]pyridines as negative allosteric modulators of metabotropic GluR5 receptors: hit-to-lead optimization.

An HTS campaign of our corporate compound library resulted in thieno[2,3-b]pyridines derivative hits with mGluR5 negative allosteric modulator effects. During the hit-to-lead development our objective was to improve affinity, and to keep the ligand efficiency values at an acceptable level. After different modifications of the linker resulted in a 2-sulfonyl-thieno[2,3-b]pyridines derivative, which fulfilled the lead criteria.

Stereoselective tandem synthesis of thiazolo fused naphthyridines and thienopyridines from o-alkynylaldehydes via Au(III)-catalyzed regioselective 6-endo-dig ring closure.

An operationally simple approach for the stereoselective tandem synthesis of novel thiazolo fused naphthyridines and thienopyridines by the reaction of o-alkynylaldehydes with L-cystine methyl ester hydrochloride via Au(III)-catalyzed regioselective 6-endo-dig ring closure under mild reaction conditions is described. It is noteworthy that alkynes bearing an alkyl and a strong electron-withdrawing nitro group successfully afforded the desired products in good yields.

Thieno[2,3-b]pyridines--a new class of multidrug resistance (MDR) modulators.

To identify new potent multidrug resistance modulators, we have synthesized a series of novel thieno[2,3-b]pyridines and furo[2,3-b]pyridines, and examined their structure-activity relationships. All synthesized compounds were tested to determine BCRP1, P-gp, and MRP1 inhibitor activity, and most potent MDR modulators were also screened for their toxicity, cytotoxicity and Ca(2+) channel antagonist activity. Among these compounds, thieno[2,3-b]pyridine (6r) was found to exhibit a potent P-gp inhibitory action with EC50 = 0.3 ± 0.2 µM, MRP1 inhibitory action with EC50 = 1.1 ± 0.1 µM and BCRP1 inhibitory action with EC50 = 0.2 ± 0.05 µM and may represent suitable candidate for further pharmacological studies.

Primary amines as directing groups in the Ru-catalyzed synthesis of isoquinolines, benzoisoquinolines, and thienopyridines.

Isoquinolines, benzoisoquinolines, thieno[3,2-c]pyridines and fused heteroaryl[2,3-c] pyridines, with a wide variety of substituents at different positions of the aromatic or heteroaromatic rings, have been synthesized by Ru-catalyzed oxidative coupling of a broad range of benzylamines or heterocycles with internal alkynes. All benzylamines and heterocycles have unprotected primary amines as efficient directing groups.

Silver-catalyzed tandem synthesis of naphthyridines and thienopyridines via three-component reaction.

An efficient approach for the silver-catalyzed regioselective tandem synthesis of highly functionalized 1,2-dihydrobenzo[1,6]naphthyridines 6a-z and 7a-e by the reaction of ortho-alkynylaldehydes 3a-n with amines 4a-d and ketones 5a-c/active methylene compounds 5d-g, under mild reaction conditions, is described. The scope of the developed chemistry was successfully extended for the direct synthesis of 1,2-dihydrobenzo[4,5]thieno[2,3-c]pyridines 8a-e, which is known as the sulfur analogue of ß-carbolines. Naphthyridines 6a-z and thienopyridines 8a-e were obtained via dual activation concept using l-proline as organocatalyst; however, naphthyridines 7a-e were synthesized without using organocatalyst. The reaction shows selective N-C bond formation on the more electrophilic alkynyl carbon, resulting in the regioselective 6-endo-dig-cyclized products. Reactivity behavior of electron-deficient and electron-rich ortho-alkynylaldehydes in the synthesis of naphthyridines and thienopyridine by three-component reaction is supported by the control experiment.

Synthesis, preliminary structure-activity relationships, and in vitro biological evaluation of 6-aryl-3-amino-thieno[2,3-b]pyridine derivatives as potential anti-inflammatory agents.

In our previous study, a series of 6-aryl-3-amino-thieno[2,3-b]pyridine derivatives exhibited potent antiproliferative activities and an unique hepatocellular carcinoma (HCC)-specific anticancer activity was also observed. In further anti-inflammatory research, thienopyridine derivative 1a showed potent inhibition of nitric oxide (NO) production. So a series of thienopyridine analogues of 1a were synthesized and evaluated for anti-inflammatory activities. The structure-activity relationships (SARs) revealed that the most potent analogues 1f and 1o were identified as potent inhibitors of NO production with IC50 values of 3.30 and 3.24 µM, respectively. These results suggest that these 6-aryl-3-amino-thieno[2,3-b]pyridine derivatives might potentially constitute a novel class of anti-inflammatory agents, which require further studies.