Synthetic access to diverse thiazetidines via a one-pot microwave assisted telescopic approach and their interaction with biomolecules

A one-pot microwave assisted telescopic approach is reported for the chemo-selective synthesis of substituted 1,3-thiazetidines using readily available 2-aminopyridines/pyrazines/pyrimidine, substituted isothiocyanates and 1,2-dihalomethanes. The procedure involves thiourea formation from 2-aminopyridines/pyrazines/pyrimidine with the substituted isothiocyanates followed by a base catalysed nucleophilic attack of the CS bond on the 1,2-dihalomethane. Subsequently, a cyclization reaction occurs to yield substituted 1,3-thiazetidines. These four membered strained ring systems are reported to possess broad substrate scope with high functional group tolerance. The above synthetic sequence for the formation of four membered heterocycles is proven to be a modular and straightforward approach. Further the mechanistic pathway for the formation of 1,3-thiazetidines was supported by computational evaluations and X-ray crystallography analyses. The relevance of these thiazetidines in biological applications is evaluated by studying their ability to bind bio-macromolecules like proteins and nucleic acids.

Discovery of Potent Antiallergic Agents Based on an o-Aminopyridinyl Alkynyl Scaffold

Effective therapeutic agents are highly desired for immune-mediated allergic diseases. Herein, we report the design, synthesis, and structure-activity relationship of an o-aminopyridinyl alkyne series as novel orally bioavailable antiallergic agents, which was identified through phenotypic screening. Compound optimization yielded a highly potent compound 36, which effectively suppressed mast cell degranulation in a dose-dependent manner (IC50, 2.54 nM for RBL-2H3 cells; 48.28 nM for peritoneal mast cells (PMCs)) with a good therapeutic index. It also regulated the activation of FcεRI-mediated downstream signaling proteins in IgE/Ag-stimulated RBL-2H3 cells. In addition, 36 exhibited excellent in vivo pharmacokinetic properties and antiallergic efficacy in both passive systemic anaphylaxis (PSA) and house dust mite (HDM)-induced murine models of pulmonary allergic inflammation. Furthermore, preliminary analysis of the kinases profile identified Src-family kinases as potential targets for 36. Compound 36 may serve as a new valuable lead compound for future antiallergic drug discovery.

Discovery and Toxicological Profiling of Aminopyridines as Orally Bioavailable Selective Inhibitors of PI3-Kinase γ

Using a novel physiologically relevant in vitro human whole blood neutrophil shape change assay, an aminopyrazine series of selective PI3Kγ inhibitors was identified and prioritized for further optimization. Severe solubility limitations associated with the series leading to low oral bioavailability and poor exposures, especially at higher doses, were overcome by moving to an aminopyridine core. Compound 33, with the optimal balance of on-target activity, selectivity, and pharmacokinetic parameters, progressed into in vivo studies and demonstrated good efficacy (10 mg/kg) in a rat model of airway inflammation. Sufficient exposures were achieved at high doses to support toxicological studies, where unexpected inflammatory cell infiltrates in cardiovascular tissue prevented further compound development.

Discovery of 5,6-Bis(4-methoxy-3-methylphenyl)pyridin-2-amine as a WSB1 Degrader to Inhibit Cancer Cell Metastasis

The gain of cell motility is an essential prerequisite for cancer metastasis. The ubiquitin ligase subunit WD repeat and SOCS box-containing 1 (WSB1) has been demonstrated to regulate hypoxia-driven tumor cell migration. However, there is still a lack of methods for discovering inhibitors targeting the WSB1 axis. Here, we employed phenotypic screening models and identified compound 4 that displayed migration inhibitory activity against WSB1-overexpressing cells. Further studies indicated that it may function as a WSB1 degrader, thus leading to the accumulation of the Rho guanosine diphosphate dissociation inhibitor 2 (RhoGDI2) protein, reversing the expression of downstream F-actin and formation of membrane ruffles, and disturbing the migration capacity of cancer cells. Moreover, compound 4 exhibited a promising in vivo anticancer metastatic effects. Our findings show the discovery of a new WSB1 degrader, providing a unique solution for the treatment of cancer metastasis.

Synthesis of multi-substituted pyridines from ylidenemalononitriles and their emission properties

Numerous methodologies to obtain pyridines from ylidenemalononitriles are described in the literature. Nevertheless, they are limited to the use of microwave or conventional heat and few lead to 2,3,4 or 2,3,4,5-substituted pyridines as multi-proposal molecular scaffolds or even universal pyridines. Herein, we present a mild and facile solvent-free methodology to obtain a scope of multi-substituted pyridines at room temperature. We also report an example where one of the resulting amino-nicotinonitriles exhibits a preliminary evidence of aggregation-induced emission (AIE).

Modulators of CFTR. Updates on clinical development and future directions

Cystic fibrosis (CF) is the most frequent life-limiting autosomal recessive disorder in the Caucasian population. It is due to mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. Current symptomatic CF therapies, which treat the downstream consequences of CFTR mutations, have increased survival. Better knowledge of the CFTR protein has enabled pharmacologic therapy aiming to restore mutated CFTR expression and function. These CFTR "modulators" have revolutionised the CF therapeutic landscape, with the potential to transform prognosis for a considerable number of patients. This review provides a brief summary of their mechanism of action and presents a thorough review of the results obtained from clinical trials of CFTR modulators.

First orally bioavailable prodrug of proteolysis targeting chimera (PROTAC) degrades cyclin-dependent kinases 2/4/6 in vivo

A growing number of reports suggested that the inhibitor targeting cyclin-dependent kinases (CDK) 2/4/6 can act as a more feasible chemotherapy strategy. In the present paper, a novel PROTAC molecule was developed based on the structure of Ribociclib's derivative. In malignant melanoma cells, the degrader can not only degrade CDK 2/4/6 simultaneously and effectively, but also remarkably induce cell cycle arrest and apoptosis of melanoma cells. Moreover, PROTAC molecules with CRBN ligands always have poor oral bioavailability. We developed the orally bioavailable prodrug for the first time. It would provide general solution for oral administration of the PROTAC molecules, derived from CRBN ligands, for animal test conveniently.

Novel dual inhibitors targeting CDK4 and VEGFR2 synergistically suppressed cancer progression and angiogenesis

Based on the significantly synergistic effects of CDK4 and VEGFR2 inhibitors on growth of cancer cells, a series of novel multi-kinase inhibitors targeting CDK4 and VEGFR2 were designed, synthesized and evaluated, among which Roxyl-ZV-5J exhibited potent and balanced activities against both CDK4 and VEGFR2 with half-maximal inhibitory concentration at the nanomolar level. It effectively induced breast and cervical cancer cell cycle arrest and cell apoptosis. Roxyl-ZV-5J also inhibited the proliferation, tube formation and VEGFR2 downstream signaling pathways of HUVECs. Oral administration of Roxyl-ZV-5J led to significant tumor regression and anti-angiogenesis without obvious toxicity in SiHa xenograft mouse model. In addition, this compound showed good pharmacokinetics. This study confirmed a new tool for dual CDK-VEGFR2 pathways inhibition achieved with a single molecule, which provided valuable leads for further structural optimization and anti-angiogenesis and anti-tumor mechanism study.

Synthesis and profiling of a 3-aminopyridin-2-one-based kinase targeted fragment library: Identification of 3-amino-5-(pyridin-4-yl)pyridin-2(1H)-one scaffold for monopolar spindle 1 (MPS1) and Aurora kinases inhibition

Screening a 3-aminopyridin-2-one based fragment library against a 26-kinase panel representative of the human kinome identified 3-amino-5-(1-methyl-1H-pyrazol-4-yl)pyridin-2(1H)-one (2) and 3-amino-5-(pyridin-4-yl)pyridin-2(1H)-one (3) as ligand efficient inhibitors of the mitotic kinase Monopolar Spindle 1 (MPS1) and the Aurora kinase family. These kinases are well recognised as attractive targets for therapeutic intervention for treating cancer. Elucidation of the binding mode of these fragments and their analogues has been carried out by X-ray crystallography. Structural studies have identified key interactions with a conserved lysine residue and have highlighted potential regions of MPS1 which could be targeted to improve activity and selectivity.

Synthesis and Evaluation of Curcuminoid Analogues as Antioxidant and Antibacterial Agents

Diazocoupling reaction of curcumin with different diazonium salts of p-toluidine, 2-aminopyridine, and 4-aminoantipyrine in pyridine yielded the arylhydrazones 2a-c. Arylhydrazone of p-toluidine reacted with urea, thiourea, and guanidine nitrate to produce 5,6-dihydropyrimidines. Further reaction of 2a with 2,3-diaminopyrdine in sodium ethoxide solution yielded 1H-pyrido[2,3-b][1,4]diazepine derivative. Bis(2,5-dihydroisoxazole) is obtained from the reaction of 2a with hydroxylamine hydrochloride, while its reactions with hydrazines afforded the respective 4,5-dihydro-1H-pyrazoles. The target compounds were evaluated as antioxidant and antibacterial agents. The tested compounds showed good to moderate activities compared to ascorbic acid and chloramphenicol, respectively.

Novel Pieces for the Emerging Picture of Sulfoximines in Drug Discovery: Synthesis and Evaluation of Sulfoximine Analogues of Marketed Drugs and Advanced Clinical Candidates

Sulfoximines have gained considerable recognition as an important structural motif in drug discovery of late. In particular, the clinical kinase inhibitors for the treatment of cancer, roniciclib (pan-CDK inhibitor), BAY 1143572 (P-TEFb inhibitor), and AZD 6738 (ATR inhibitor), have recently drawn considerable attention. Whilst the interest in this underrepresented functional group in drug discovery is clearly on the rise, there remains an incomplete understanding of the medicinal-chemistry-relevant properties of sulfoximines. Herein we report the synthesis and in vitro characterization of a variety of sulfoximine analogues of marketed drugs and advanced clinical candidates to gain a better understanding of this neglected functional group and its potential in drug discovery.

Solvent-free synthesis of novel steroidal 2-aminopyridines

The synthesis of novel steroidal 3-cyano-2-aminopyridines using enaminonitrile and various primary amines was established under solvent-free condition. Structures of the new compounds were characterized by MS, ¹H and ¹³C NMR data and the structure of 2-aminopyridine of the product 5b was further confirmed by X-ray analysis. The reaction mechanism was proposed on the basis of the key intermediate obtained. The adjacent amine and nitrile groups existed in the final products have the potential for late stage functionalization, which would provide efficient access to steroidal compound collections with structural diversity and complexity.

Synthesis of a Potent Aminopyridine-Based nNOS-Inhibitor by Two Recent No-Carrier-Added (18)F-Labelling Methods

Nitric oxide (NO), an important multifunctional signaling molecule, is produced by three isoforms of NO-synthase (NOS) and has been associated with neurodegenerative disorders. Selective inhibitors of the subtypes iNOS (inducible) or nNOS (neuronal) are of great interest for decoding neurodestructive key factors, and ¹⁸F-labelled analogues would allow investigating the NOS-function by molecular imaging with positron emission tomography. Especially, the highly selective nNOS inhibitor 6-((3-((3-fluorophenethylamino)methyl)phenoxy)methyl)-4-methylpyridin-2-amine (10) lends itself as suitable compound to be ¹⁸F-labelled in no-carrier-added (n.c.a.) form. For preparation of the ¹⁸F-labelled nNOS-Inhibitor [¹⁸F]10 a “build-up” radiosynthesis was developed based on a corresponding iodonium ylide as labelling precursor. The such activated phenethyl group of the compound was efficiently and regioselectively labelled with n.c.a. [¹⁸F]fluoride in 79% radiochemical yield (RCY). After conversion by reductive amination and microwave assisted displacement of the protecting groups, the desired nNOS-inhibitor was obtained in about 15% total RCY. Alternatively, for a simplified “late-stage” ¹⁸F-labelling procedure a corresponding boronic ester precursor was synthesized and successfully used in a newer, copper(II) mediated n.c.a. ¹⁸F-fluoro-deboroniation reaction, achieving the same total RCY. Thus, both methods proved comparatively suited to provide the highly selective NOS-inhibitor [¹⁸F]10 as probe for preclinical in vivo studies.

Synthesis of meta-substituted [(18)F]3-fluoro-4-aminopyridine via direct radiofluorination of pyridine N-oxides

Due to their electron-rich aromatic structure, nucleophilic (radio)fluorination of pyridines is challenging, especially at the meta position. In this paper, we describe the first example of direct fluorination of a pyridine N-oxide to produce a meta fluorinated pyridine. Specifically, fluorination of 3-bromo-4-nitropyridine N-oxide produced in several minutes 3-fluoro-4-nitropyridine N-oxide in moderate yield at room temperature. This intermediate compound was later converted to 3-fluoro-4-aminopyridine easily by catalytic hydrogenation. Furthermore, this approach was successfully applied for labeling with fluorine-18. The use of pyridine N-oxides for the preparation of fluoropyridines is unprecedented in the chemical literature and has the potential to offer a new way for the synthesis of these important structures in pharmaceuticals and radiopharmaceuticals.

BJ-1108, a 6-Amino-2,4,5-Trimethylpyridin-3-ol Analog, Inhibits Serotonin-Induced Angiogenesis and Tumor Growth through PI3K/NOX Pathway

5-Hydroxytryptamine (5-HT) induces proliferation of cancer cells and vascular cells. In addition to 5-HT production by several cancer cells including gastrointestinal and breast cancer, a significant level of 5-HT is released from activated platelets in the thrombotic environment of tumors, suggesting that inhibition of 5-HT signaling may constitute a new target for antiangiogenic anticancer drug discovery. In the current study we clearly demonstrate that 5-HT-induced angiogenesis was mediated through the 5-HT₁ receptor-linked Gβγ/Src/PI3K pathway, but not through the MAPK/ERK/p38 pathway. In addition, 5-HT induced production of NADPH oxidase (NOX)-derived reactive oxygen species (ROS). In an effort to develop new molecularly targeted anticancer agents against 5-HT action in tumor growth, we demonstrate that BJ-1108, a derivative of 6-amino-2,4,5-trimethylpyridin-3-ol, significantly inhibited 5-HT-induced angiogenesis. In addition, BJ-1108 induced a significant reduction in the size and weight of excised tumors in breast cancer cell-inoculated CAM assay, showing proportionate suppression of tumor growth along with inhibition of angiogenesis. In human umbilical vein endothelial cells (HUVECs), BJ-1108 significantly suppressed 5-HT-induced ROS generation and phosphorylation of PI3K/Akt but not of Src. Unlike NOX inhibitors, BJ-1108, which showed better antioxidant activity than vitamin C, barely suppressed superoxide anion induced by mevalonate or geranylgeranyl pyrophosphate which directly activates NOX without help from other signaling molecules in HUVECs, implying that the anti-angiogenic action of BJ-1108 was not mediated through direct action on NOX activation, or free radical scavenging activity. In conclusion, BJ-1108 inhibited 5-HT-induced angiogenesis through PI3K/NOX signaling but not through Src, ERK, or p38.

Self-assembled metallogels formed from N,N',N''-tris(4-pyridyl)trimesic amide in aqueous solution induced by Fe(III)/Fe(II) ions

In this work, we report self-assembled metallogels formed from a ligand of trimesic amide, N,N',N''-tris(4-pyridyl)trimesic amide (TPTA), induced by Fe(III)/Fe(II) ions. TPTA is difficult to dissolve in water even in the presence of some metal ions such as Cu(2+), Co(2+), Ni(2+), K(+), Na(+) and Mg(2+) under heating, and it exhibits no gelation ability. Interestingly, upon heating TPTA can be dissolved easily in aqueous solution containing Fe(3+)/Fe(2+), and subsequently self-assembled into metallogels after cooling. The metallogels could also be formed in aqueous solutions of mixed metal ions containing Fe(3+)/Fe(2+), indicating that the other metal ions do not affect the formation of Fe(III)-TPTA and Fe(II)-TPTA metallogels. The high selectivity of metallogel formation to Fe(3+)/Fe(2+) may be used for application in the test of Fe(3+)/Fe(2+). The metallogels obtained are characterized by scanning electron microscopy, Fourier transform infrared spectra, nuclear magnetic resonance spectra, rheological measurements and scanning tunneling microscopy. The results indicate that TPTA can self-assemble into fibrous aggregates in Fe(3+)/Fe(2+) aqueous solution through the metal-ligand interactions and intermolecular hydrogen bonding. This kind of metallogel also possesses good mechanical properties and thermoreversibility.

Two new zinc(II) acetates with 3- and 4-aminopyridine: syntheses and structural properties

The synthesis and characterization of two new zinc(II) coordination compounds with 3- and 4-aminopyridine are reported. They were obtained after adding a water solution of Zn(CH3COO)2·2H2O or dissolving solid Zn(CH3COO)2 ∙ 2H2O in methanol solutions of 3- and 4-aminopyridine. The products were characterized structurally by single-crystal X-ray diffraction analysis. Colourless crystals of the compound synthesized by the reaction of Zn(CH3COO)2·2H2O and 3-aminopyridine (3-apy), are built of trinuclear complex molecules with the formula [Zn3(O2CCH3)6(3-apy)2(H2O)2] (1). The molecules consists of two terminal Zn atoms, coordinated tetrahedrally, and one central Zn atom, coordinated octahedrally. Colourless crystals, obtained by the reaction of Zn(CH3COO)2·2H2O with 4-aminopyridine (4-apy), consist of a mononuclear complex [Zn(O2CCH3)2(4-apy)2] (2). Hydrogen‒bonding interactions in the crystal structures of both complexes are reported.

Synthesis, characterization and biological studies of a charge transfer complex: 2-aminopyridinium-4-methylbenzenesulfonate

A single crystal charge transfer (CT) complex, 2-aminopyridinium-4-methylbenzenesulfonate (APTS) was synthesized and recrystallized by slow solvent evaporation solution growth method at room temperature. The complex has been characterized with the elemental analysis, UV-visible, infrared (IR), (1)H and (13)C nuclear magnetic resonance (NMR) spectra. Thermogravimetric (TG) and differential thermal analysis (DTA) were reported the thermal behaviour of the complex. Single crystal XRD studies showed that the orthorhombic nature of the crystal with space group Pbca. The biological activities of CT complex, such as DNA binding and antioxidant activity has been carried out. The results indicated that the compound could interact with DNA through intercalation and show significant capacity of scavenging with 2,2-diphenyl-2-picryl-hydrazyl (DPPH).

Design, synthesis, and structure-activity relationship studies of novel thioether pleuromutilin derivatives as potent antibacterial agents

A series of novel thioether pleuromutilin derivatives incorporating various heteroaromatic substituents into the C14 side chain have been reported. Structure-activity relationship (SAR) studies resulted in compounds 52 and 55 with the most potent in vitro antibacterial activity among the series (MIC = 0.031-0.063 μg/mL). Further optimization to overcome the poor water solubility of compound 55 resulted in compounds 87, 91, 109, and 110 possessing good in vitro antibacterial activity with increased hydrophilicity. Compound 114, the water-soluble phosphate prodrug of compound 52, was also prepared and evaluated. Among the derivatives, compound 110 showed moderate pharmacokinetic profiles and good in vivo efficacy in both MSSA and MRSA systemic infection models. Compound 110 was further evaluated in CYP450 inhibition assay and displayed intermediate in vitro inhibition of CYP3A4.

Design and synthesis of novel thiophenes bearing biologically active aniline, aminopyridine, benzylamine, nicotinamide, pyrimidine and triazolopyrimidine moieties searching for cytotoxic agents

To discover new bioactive lead compounds for medicinal purposes, herein, (E)-3-(substituted amino)-1-thiophen-2-yl-prop-2-en-1-ones 3-8, aminopyridines 9-11, benzylamine 12, nicotinamide 13, pyrimidines 14, 15, hexanoic acid 16 and triazolopyrimidine 19 were prepared and tested for cytotoxic activity. Results showed that the tested compounds exhibited a remarkable activity, especially compounds 3 and 19 with IC50 values (55.2 and 50.49 microM, respectively) compared to doxorubicin (IC50 = 71.8 microM) as a reference drug.

Rational development of 4-aminopyridyl-based inhibitors targeting Trypanosoma cruzi CYP51 as anti-chagas agents

A new series of 4-aminopyridyl-based lead inhibitors targeting Trypanosoma cruzi CYP51 (TcCYP51) has been developed using structure-based drug design as well as structure-property relationship (SPR) analyses. The screening hit starting point, LP10 (KD ≤ 42 nM; EC50 = 0.65 μM), has been optimized to give the potential leads 14t, 27i, 27q, 27r, and 27t, which have low-nanomolar binding affinity to TcCYP51 and significant activity against T. cruzi amastigotes cultured in human myoblasts (EC50 = 14-18 nM for 27i and 27r). Many of the optimized compounds have improved microsome stability, and most are selective against human CYPs 1A2, 2D6, and 3A4 (<50% inhibition at 1 μM). A rationale for the improvement in microsome stability and selectivity of inhibitors against human metabolic CYP enzymes is presented. In addition, the binding mode of 14t with the Trypanosoma brucei CYP51 (TbCYP51) orthologue has been characterized by X-ray structure analysis.

Synthesis and characterization of binary and ternary complexes of Co(II), Ni(II), Cu(II) and Zn(II) ions based on 4-aminotoluene-3-sulfonic acid

Salicylidene (4-aminotoluene-3-sulfonic acid) Schiff base ligand H(2)L, and its binary and ternary Co(II), Ni(II), Cu(II) and Zn(II) complexes using 8-hydroxyquinoline (8-HOqu) and 2-aminopyridine (2-Ampy) as secondary ligands have been synthesised and characterized via elemental analysis, spectral data (IR, (1)H NMR, mass and solid reflectance), molar conductance, magnetic moment, TG-DSC measurements and XRPD analysis. Correlation of all spectroscopic data suggest that H(2)L ligand acts as monoanionic terdentate ligand with ONO sites coordinating to the metal ions via deprotonated phenolic-O, azomethine-N and sulfonate-O while 2-Ampy behaves as a neutral monodentate ligand via amino group-N and 8-HOqu behaves as a monoanionic bidentate ligand through the ring-N and deprotonated phenolic-O. The thermal behavior of these complexes shows that the coordinated water molecules were eliminated from the complexes at relatively higher temperatures than the hydrated water and there are two routes in removal of coordinated water molecules. All complexes have mononuclear structure and the tetrahedral, square planar or an octahedral geometry have been proposed. The ligand and its complexes have been screened for their antimicrobial activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Salmonella typhimurium, Candida albicans and Aspergillus fumigatus. Among the synthesised compounds, the binary and ternary Ni(II) complexes, (2, 8 and 10) and ternary Zn(II) complex, (12) were found to be very effective against Candida albicans and Bacillus subtilis than all other complexes with MICs of 2 and 8 μg/mL, respectively.

Pyridonepezils, new dual AChE inhibitors as potential drugs for the treatment of Alzheimer's disease: synthesis, biological assessment, and molecular modeling

The synthesis, biological assessment and molecular modeling of new pyridonepezils1-8, able to inhibit human acetylcholinesterase (hAChE) and human butyrylcholinesterase (hBuChE), are described. The new compounds have been designed as hybrids resulting from a conjunctive approach that combines the N-benzylpiperidine moiety, present in donepezil, and the 2-amino-6-chloropyridine heterocyclic ring system, connected by an appropriate polymethylene linker. Compounds 1-8 were prepared by reaction of 2-amino-6-chloro-4-phenylpyridine-3,5-dicarbonitrile (13) [or 2-amino-6-chloropyridine-3,5-dicarbonitrile (14)] with 2-(1-benzylpiperidin-4-yl)alkylamines (9-12). The biological evaluation of molecules 1-8 showed that compounds 1-6 are potent AChE inhibitors, in the submicromolar, while compounds 7 and 8 are on the nanomolar range, the most potent, 2-amino-6-((3-(1-benzylpiperidin-4-yl)propyl)amino)pyridine-3,5-dicarbonitrile (7), showing a IC(50) (hAChE) = 9.4 ± 0.4 nM. Inhibitors 2-8 are permeable as determined in the PAMPA assay. Compared to donepezil, compound 7 is in the same range of inhibitory activity for hAChE, and 703-fold more selective for hAChE than for hBuChE. Molecular modeling investigation on pyridonepezil7 supports its dual AChE inhibitory profile, binding simultaneously at the catalytic active and at peripheral anionic sites of the enzyme. The theoretical ADME analysis of pyridonepezils1-8 has been carried out. Overall, compound 7, a potent and selective dual AChEI, can be considered as a candidate with potential impact for further pharmacological development in Alzheimer's therapy.

Synthesis and CYP26A1 inhibitory activity of novel methyl 3-[4-(arylamino)phenyl]-3-(azole)-2,2-dimethylpropanoates

The role of all-trans-retinoic acid (ATRA) in the development and maintenance of many epithelial and neural tissues has raised great interest in the potential of ATRA and related compounds (retinoids) as pharmacological agents, particularly for the treatment of cancer, skin, neurodegenerative and autoimmune diseases. The use of ATRA or prodrugs as pharmacological agents is limited by a short half-life in vivo resulting from the activity of specific ATRA hydroxylases, CYP26 enzymes, induced by ATRA in liver and target tissues. For this reason retinoic acid metabolism blocking agents (RAMBAs) have been developed for treating cancer and a wide range of other diseases. The synthesis, CYP26A1 inhibitory activity and molecular modeling studies of novel methyl 3-[4-(arylamino)phenyl]-3-(azole)-2,2-dimethylpropanoates are presented. From this series of compounds clear SAR can be derived for 4-substitution of the phenyl ring with electron-donating groups more favourable for inhibitory activity. Both the methylenedioxyphenyl imidazole (17, IC(50) = 8 nM) and triazole (18, IC(50) = 6.7 nM) derivatives were potent inhibitors with additional binding interactions between the methylenedioxy moiety and the CYP26 active site likely to be the main factor. The 6-bromo-3-pyridine imidazole 15 (IC(50) = 5.7 nM) was the most active from this series compared with the standards liarozole (IC(50) = 540 nM) and R116010 (IC(50) = 10 nM).

Design of potent and selective hybrid inhibitors of the mitotic kinase Nek2: structure-activity relationship, structural biology, and cellular activity

We report herein a series of Nek2 inhibitors based on an aminopyridine scaffold. These compounds have been designed by combining key elements of two previously discovered chemical series. Structure based design led to aminopyridine (R)-21, a potent and selective inhibitor able to modulate Nek2 activity in cells.

Synthesis of 6-[¹⁸F]fluoro-PBR28, a novel radiotracer for imaging the TSPO 18 kDa with PET

6-Fluoro-PBR28 (N-(6-fluoro-4-phenoxypyridin-3-yl)-N-(2-methoxybenzyl)acetamide), a fluorinated analogue of the recently developed TSPO 18 kDa ligand PBR28, was synthesized and labelled with fluorine-18. 6-Fluoro-PBR28 and its 6-chloro/6-bromo counterparts were synthesized in six chemical steps and obtained in 16%, 10% and 19% overall yields, respectively. Labelling with fluorine-18 was performed in one single step (chlorine/bromine-for-fluorine heteroaromatic substitution) using a Zymate-XP robotic system affording HPLC-purified, ready-to-inject, 6-[(18)F]fluoro-PBR28 (>95% radiochemically pure). Non-decay-corrected overall yields were 9-10% and specific radioactivities ranged from 74 to 148 GBq/μmol. In vitro binding experiments, dynamic μPET studies performed in a rat model of acute neuroinflammation (unilaterally, AMPA-induced, striatum-lesioned rats) and ex vivo autoradiography on the same model demonstrated the potential of 6-[(18)F]fluoro-PBR28 to image the TSPO 18 kDa using PET.

Microwave assisted synthesis and solid-state characterization of lithocholyl amides of isomeric aminopyridines

Microwave (MW) assisted synthesis and solid state structural characterizations of novel lithocholyl amides of 2-, 3-, and 4-aminopyridine are reported. It is shown that the MW technique is a proper method in the preparation of N-lithocholyl amides of isomeric aminopyridines. It offers many advantages compared to conventional heating. The molecular and crystal structures as well as the polymorphic and hydrated forms of prepared conjugates with their thermodynamic stabilities have been characterized by means of high resolution liquid- and solid-state NMR spectroscopy, single crystal and powder X-ray diffraction, and thermogravimetric analysis. Owing to the many biological functions of bile acids and amino substituted nitrogen heterocycles, knowledge of the crystal packing of these novel conjugates may have relevance for potential pharmaceutical applications.

A novel histone deacetylase inhibitor Chidamide induces apoptosis of human colon cancer cells

Many studies have demonstrated that histone deacetylase (HDAC) inhibitors induce various tumor cells to undergo apoptosis, and such inhibitors have been used in different clinical trials against different human cancers. In this study, we designed and synthesized a novel HDAC inhibitor, Chidamide. We showed that Chidamide was able to increase the acetylation levels of histone H3 and to inhibit the PI3K/Akt and MAPK/Ras signaling pathways, which resulted in arresting colon cancer cells at the G1 phase of the cell cycle and promoting apoptosis. As a result, the proliferation of colon cancer cells was suppressed in vitro. Our data support the potential application of Chidamide as an anticancer agent in treating colon cancer. Future studies are needed to demonstrate its in vivo efficacy.

Investigation of aminopyridiopyrazinones as PDE5 inhibitors: Evaluation of modifications to the central ring system

Efforts to improve the potency and physical properties of the aminopyridiopyrazinone class of PDE5 inhibitors through modification of the core ring system are described. Five new ring systems are evaluated and features that impart improved potency and improved solubility are delineated.

Synthesis and biological evaluation of amino-pyridines as androgen receptor antagonists for stimulating hair growth and reducing sebum production

A series of amino-pyridines were synthesized and evaluated for androgen antagonist activities. Among these compounds, (R)-(+)-6-[methyl-(1-phenyl-ethyl)-amino]-4-trifluoromethyl-nicotinonitrile was the most active example of this class. This compound displayed potent androgen receptor antagonist activity as well as favorable pharmacokinetic characteristics for a potential topical agent. It also demonstrated remarkable potency for stimulating hair growth in a male C3H mouse model as well as reducing sebum production in the male Syrian hamster ear model.

Synthesis and Decomposition of an Ester Derivative of the Procarcinogen and Promutagen, PhIP, 2-Amino-1-methyl-6-phenyl-1H-imidazo[4,5-b]pyridine: Unusual Nitrenium Ion Chemistry

The food-derived heterocyclic amine (HCA) carcinogen 2-amino-1-methyl-6-phenyl-1H-imidazo[4,5-b]pyridine, PhIP, is often generated in the highest concentration of the HCAs formed during broiling and frying of meat and fish. Although it is considered to be an important contributor to human cancer risk from exposure to HCAs, the chemistry of PhIP metabolites that presumably react with DNA to initiate carcinogenesis has received only cursory attention. We have synthesized the ester derivative N-pivaloxy-2-amino-1-methyl-6-phenyl-1H-imidazo[4,5-b]pyridine, 1b, and investigated its chemistry in aqueous solution. Although 1b was too unstable to isolate, we could characterize it by NMR methods in DMF-d7, a solvent in which it is stable at -40 degrees C. It decomposed rapidly in aqueous solution, but its conjugate acid, 1bH+, is not reactive. The nitrenium ion, 2, was trapped by N(3)(-) to form the unusual tetrazole adduct, 16. In the absence of N3-, the expected hydration products of 2 were not detected, but the reduction product, 12, was detected. Although such products are often taken as evidence of triplet nitrenium ions, the efficient trapping of 2 by N(3)(-) indicates that it is a ground state singlet species. The product 12 appears to be generated by reduction of an initially formed hydration product of 2. An alternative addition-elimination mechanism for the formation of 12 does not fit the available kinetic data. The selectivity of 2, measured as kaz/ks, the ratio of the second-order rate constant for its reaction with N(3)(-) and the first-order rate constant for its reaction with the aqueous solvent, is (2.3 +/- 0.6) x 10(4) M(-1), a value that is in the middle of the range of k(az)/k(s) of 10-10(6) M(-1) observed for nitrenium ions derived from other HCAs. The mutagenicity of aromatic amines (AAs) and HCAs, measured as the log of histidine revertants per nanomole of amine, log m, in Salmonella typhimurium TA 98 and TA 100 correlates with log(k(az)/k(s)) for a wide variety of carbocyclic and heterocyclic amine mutagens including PhIP. Previously developed linear regression models for mutagenicity that include log(k(az)/k(s)) as an independent variable predict log m for PhIP with good accuracy in both TA 98 and TA 100. Quantitative carcinogenicity data are less strongly correlated with log(k(az)/k(s)), so prediction of the carcinogenicity of PhIP and other HCAs or AAs based primarily on log(k(az)/k(s)) is less successful.

Thiophene-anthranilamides as highly potent and orally available factor Xa inhibitors

There remains a high unmet medical need for a safe oral therapy for thrombotic disorders. The serine protease factor Xa (fXa), with its central role in the coagulation cascade, is among the more promising targets for anticoagulant therapy and has been the subject of intensive drug discovery efforts. Investigation of a hit from high-throughput screening identified a series of thiophene-substituted anthranilamides as potent nonamidine fXa inhibitors. Lead optimization by incorporation of hydrophilic groups led to the discovery of compounds with picomolar inhibitory potency and micromolar in vitro anticoagulant activity. Based on their high potency, selectivity, oral pharmacokinetics, and efficacy in a rat venous stasis model of thrombosis, compounds ZK 814048 (10b), ZK 810388 (13a), and ZK 813039 (17m) were advanced into development.

A General and Efficient 2-Amination of Pyridines and Quinolines

Pyridine N-oxides were converted to 2-aminopyridines in a one-pot fashion using Ts2O-t-BuNH2 followed by in situ deprotection with TFA. The amination proceeded in high yields, excellent 2-/4-selectivity, and with good functional group compatibility. 2-Amino (iso)quinolines were also obtained in the same manner. Combined with the simple oxidation of pyridines to pyridine N-oxides, this method provides a general and efficient way for amination of 2-unsubstituted pyridines.

Hemodynamic effects of potent and selective JNK inhibitors in anesthetized rats: Implication for targeting protein kinases in metabolic diseases

The hemodynamic effects of a series of potent and selective 4-aminopyridine carboxamide-based pan-JNK inhibitors were assessed in an anesthetized rat model. The effects of these agents on mean arterial pressure, heart rate, cardiac contractility, and peripheral vascular resistance are described, and the implication for targeting protein kinases in metabolic diseases is discussed.

N-Monocarbamoyl Derivatives of Symmetrical Diamines with Antiviral Activity

Some new N-monocarbamoyl symmetrical diamines have been prepared by the addition of symmetrical amines to isocyanates or isothiocyanates. 2,6-Diaminopyridine (1), (1R,2R)-1,2-diaminocyclohexane [(1R,2R)-2], meso-1,2-diaminocyclohexane (meso-2), or (1R,2R)-1,2-diphenylethylenediamine (3) were used as the starting symmetrical diamine frameworks. All of the newly synthesized compounds were subjected to an evaluation of antiviral activity with herpes simplex virus (HSV)-1. N-Monocarbamoyl 2,6-diaminopyridines (5a, b) showed significant antiviral activity (EC(50)=17.0, 6.2 microg/ml) comparable to that of N-monododecanoyl 2,6-diaminopyridine (A2). As a result, compound 5a showed a better selectivity index (CC(50)/EC(50) = ca. 10.0) than that of A2.

An efficient and chemoselective synthesis of N-substituted 2-aminopyridines via a microwave-assisted multicomponent reaction

A facile and selective synthesis of N-substituted 2-aminopyridines is accomplished via microwave-assisted multi-component reactions controlled by the basicity of amine and the nature of solvent. In addition, a possible mechanism accounting for the reaction was proposed.

Synthesis and Evaluation of 2-Nonylaminopyridine Derivatives as PPAR Ligands

To find novel PPAR ligands, we prepared several 3-{3 or 4-[2-(nonylpyridin-2-ylamino)ethoxy]phenyl}propanoic acid derivatives which were designed based on the structure of our previous PPARgamma ligand 1. In PPAR binding affinity assays, compound 4, which had an ethoxy group at the C-2 position of the propanoic acid of 1, showed selective binding affinity for PPARgamma. Compound 3, with an ethyl group at the C-2 position, was found to be a PPARalpha/gamma dual ligand. Compound 6, the meta isomer of 1, has been shown to be a PPARalpha ligand. The introduction of methyl (7) and ethyl (8) groups to the C-2 position of the propanoic acid of 6 further improved PPARalpha-binding potency. In cell-based transactivation assay, compounds 3 and 4 showed dual-agonist activity toward PPARalpha and PPARgamma. Compound 6 was found to be a triple agonist and compound 8 proved to be a selective PPARalpha agonist. In the human hypodermic preadipocyte differentiation test, it was demonstrated that the maximal activity of compounds 3 and 4 was higher than that of rosiglitazone.

Structure−Activity Relationship Study of Prion Inhibition by 2-Aminopyridine-3,5-dicarbonitrile-Based Compounds: Parallel Synthesis, Bioactivity, and in Vitro Pharmacokinetics

2-Aminopyridine-3,5-dicarbonitrile compounds were previously identified as mimetics of dominant-negative prion protein mutants and inhibit prion replication in cultured cells. Here, we report findings from a comprehensive structure-activity relationship study of the 6-aminopyridine-3,5-dicarbonitrile scaffold. We identify compounds with significantly improved bioactivity (approximately 40-fold) against replication of the infectious prion isoform (PrPSc) and suitable pharmacokinetic profiles to warrant evaluation in animal models of prion disease.

Novel 2-aminopyrimidine carbamates as potent and orally active inhibitors of Lck: synthesis, SAR, and in vivo antiinflammatory activity

The lymphocyte-specific kinase (Lck) is a cytoplasmic tyrosine kinase of the Src family expressed in T cells and NK cells. Genetic evidence in both mice and humans demonstrates that Lck kinase activity is critical for signaling mediated by the T cell receptor (TCR), which leads to normal T cell development and activation. A small molecule inhibitor of Lck is expected to be useful in the treatment of T cell-mediated autoimmune and inflammatory disorders and/or organ transplant rejection. In this paper, we describe the synthesis, structure-activity relationships, and pharmacological characterization of 2-aminopyrimidine carbamates, a new class of compounds with potent and selective inhibition of Lck. The most promising compound of this series, 2,6-dimethylphenyl 2-((3,5-bis(methyloxy)-4-((3-(4-methyl-1-piperazinyl)propyl)oxy)phenyl)amino)-4-pyrimidinyl(2,4-bis(methyloxy)phenyl)carbamate (43) exhibits good activity when evaluated in in vitro assays and in an in vivo model of T cell activation.

Analysis of 18F-labelled synthesis products on TLC plates: Comparison of radioactivity scanning, film autoradiography, and a phosphoimaging technique

We compared radioactivity scanning, film autoradiography, and digital photostimulated luminescence (PSL) autoradiography (phosphoimaging technique) in detection of radioactivity on thin-layer chromatography (TLC) plates. TLC combined with radioactivity detection is rapid, simple, and relatively flexible. Here, (18)F-labelled synthesis products were analyzed by TLC and the radioactivity distribution on the plates determined using the three techniques. Radioactivity scanning is appropriate only with good chromatographic resolution and previously validated scanning parameters. Film autoradiography exhibits poor linearity if radioactivity varies greatly. PSL provides high sensitivity and resolution and superior linearity compared with the other methods.

Discovery and pharmacological evaluation of growth hormone secretagogue receptor antagonists

The discovery and pharmacological evaluation of potent, selective, and orally bioavailable growth hormone secretagogue receptor (GHS-R) antagonists are reported. Previously, 2,4-diaminopyrimidine-based GHS-R antagonists reported from our laboratories have been shown to be dihydrofolate reductase (DHFR) inhibitors. By comparing the X-ray crystal structure of DHFR docked with our GHS-R antagonists and GHS-R modeling, we designed and synthesized a series of potent and DHFR selective GHS-R antagonists with good pharmacokinetic (PK) profiles. An amide derivative 13d (Ca2+ flux IC50 = 188 nM, [brain]/[plasma] = 0.97 @ 8 h in rat) showed a 10% decrease in 24 h food intake in rats, and over 5% body weight reduction after 14-day oral treatment in diet-induced obese (DIO) mice. In comparison, a urea derivative 14c (Ca2+ flux IC50 = 7 nM, [brain]/[plasma] = 0.0 in DIO) failed to show significant effect on food intake in the acute feeding DIO model. These observations demonstrated for the first time that peripheral GHS-R blockage with small molecule GHS-R antagonists might not be sufficient for suppressing appetite and inducing body weight reduction.

Discovery and evaluation of N-cyclopropyl- 2,4-difluoro-5-((2-(pyridin-2-ylamino)thiazol-5- ylmethyl)amino)benzamide (BMS-605541), a selective and orally efficacious inhibitor of vascular endothelial growth factor receptor-2

Substituted 3-((2-(pyridin-2-ylamino)thiazol-5-ylmethyl)amino)benzamides were identified as potent and selective inhibitors of vascular endothelial growth factor receptor-2 (VEGFR-2) kinase activity. The enzyme kinetics associated with the VEGFR-2 inhibition of 14 (Ki=49+/-9 nM) confirmed that the aminothiazole-based analogues are competitive with ATP. Analogue 14 demonstrated excellent kinase selectivity, favorable pharmacokinetic properties in multiple species, and robust in vivo efficacy in human lung and colon carcinoma xenograft models.

Design, synthesis, SAR, and biological evaluation of new 4-(phenylamino)thieno[2,3-b]pyridine derivatives

In this work, we performed the design, synthesis, and the structure-activity relationship studies of 13 new derivatives of thieno[2,3-b]pyridine. These derivatives were prepared in high yields (96-70%) and their structures were elucidated by IR, (1)H, (13)C NMR, and MS. The biological results showed some derivatives as antiparasitic agents against Giardia lamblia. Computational analysis of HOMO and LUMO energy, HOMO orbital coefficient distribution, electrostatic potential map, dipole moment, and density HOMO was performed to gain insight into the SAR aspects. This study pointed the p-methoxy substituted derivative as a leading compound for the development of new microbicidal medicines based on thieno[2,3-b]pyridine analogs.

Aminopyridine-based c-Jun N-terminal kinase inhibitors with cellular activity and minimal cross-kinase activity

The c-Jun N-terminal kinases (JNK-1, -2, and -3) are members of the mitogen activated protein (MAP) kinase family of enzymes. They are activated in response to certain cytokines, as well as by cellular stresses including chemotoxins, peroxides, and irradiation. They have been implicated in the pathology of a variety of different diseases with an inflammatory component including asthma, stroke, Alzheimer's disease, and type 2 diabetes mellitus. In this work, high-throughput screening identified a JNK inhibitor with an excellent kinase selectivity profile. Using X-ray crystallography and biochemical screening to guide our lead optimization, we prepared compounds with inhibitory potencies in the low-double-digit nanomolar range, activity in whole cells, and pharmacokinetics suitable for in vivo use. The new compounds were over 1,000-fold selective for JNK-1 and -2 over other MAP kinases including ERK2, p38alpha, and p38delta and showed little inhibitory activity against a panel of 74 kinases.

Synthesis and in vivo evaluation of [11C]SN003 as a PET ligand for CRF1 receptors

Synthesis and evaluation of [O-methyl-11C](4-methoxy-2-methylphenyl)[1-(1-methoxymethylpropyl)-6-methyl-1H-[1,2,3]triazolo[4,5-c]pyridin-4-yl]amine or [11C]SN003 ([11C]6), as a PET imaging agent for CRF1 receptors, in baboons is described. 4-[1-(1-Methoxymethylpropyl)-6-methyl-1H-[1,2,3]triazolo[4,5-c]pyridin-4-ylamino]-3-methylphenol (5), the precursor molecule for the radiolabeling, was synthesized from 2,4-dichloro-6-methyl-3-nitropyridine in seven steps with 20% overall yield. The total time required for the synthesis of [11C]SN003 is 30 min from EOB using [11C]methyl triflate in the presence of NaOH in acetone. The yield of the synthesis is 22% (EOS) with >99% chemical and radiochemical purities and a specific activity of >2000 Ci/mmol. PET studies in baboon show that [11C]6 penetrates the BBB and accumulates in brain. No detectable specific binding was observed, likely due to the rapid metabolism or low density of CRF1 receptors in primate brain.

Synthesis, a case of isostructural packing, and antimicrobial activity of silver(i)quinoxaline nitrate, silver(i)(2,5-dimethylpyrazine) nitrate and two related silver aminopyridine compounds

The synthesis and low temperature crystal structures of [Ag(quinoxaline)]n(NO3)n, 1, [Ag(2,5-dimethylpyrazine)(NO3)]n, 2 and [Ag4(3-aminopyridine)4(NO3)4]n 3 are presented. The quinoxaline compound forms a 1D coordination polymer with the characteristic linear 2-coordination figure of silver(I), the N-Ag-N angle being 164.2(1) degrees, and only weak silver-nitrate interactions. In addition there is an interaction giving pairs of parallel chains as the main structural theme. The 2,5-dimethylpyrazine compound has approximately trigonal-planar coordination, also binding one nitrate at the relatively short Ag-O distances 2.444(3) angstroms and 2.484(3) angstroms, respectively, for the two crystallographically different silver atoms. This also results in a 1D coordination polymer that, despite the large differences in the Ag(I) coordination environment, is isostructural with 1. [Ag4(3-aminopyridine)4(NO3)4]n 3 forms a 2D coordination polymer by bridging nitrate ions. The antimicrobial activity of 1-3, and also of [Ag3(2-aminopyridine)4](NO3)3, 4 was screened for 13 different pathogens and substantial activity was shown for 1 against Escherichia coli and Pseudomonas aeruginosa (MIC 4 microg cm(-3)) and somewhat lower activity was registered against Sarcina lutea and Salmonella typhi for 1, Bordetella bronchiseptica for 2, Salmonella typhi and Pseudomonas aeruginosa for 3, and Escherichia coli and Shigella sonnie for 3 (MIC 8 microg cm(-3)). Only low activity was shown against the yeast Candida albicans for 1, 2 and 4 whereas no activity against this pathogen was registered for 3.

Dialkylaminopyridine-Functionalized Mesoporous Silica Nanosphere as an Efficient and Highly Stable Heterogeneous Nucleophilic Catalyst

A new nucleophilic catalytic system comprised of dialkylaminopyridine-functionalized mesoporous silica nanosphere (DMAP-MSN) has been synthesized and characterized. We have demonstrated that this material is an efficient heterogeneous catalyst for Baylis-Hillman, acylation, and silylation reactions with good reactivity, product selectivity, and recyclability. We envision that this DMAP-functionalized mesoporous silica material can also serve as an effective heterogeneous catalyst for many other catalytic nucleophilic reactions.

Bradykinin B1 antagonists: SAR studies in the 2,3-diaminopyridine series

SAR study of the biphenyl region of 2,3-diaminopyridine bradykinin B1 antagonists was investigated with non-aromatic carbo- and heterocyclic rings. A piperidine ring was found to be a good replacement for the proximal phenyl ring while replacement of the distal phenyl was optimal with a cyclohexyl group leading to a dramatic improvement in affinity for the B1 receptor.

Synthesis and identification of [1,3,5]triazine-pyridine biheteroaryl as a novel series of potent cyclin-dependent kinase inhibitors

On the basis of previous studies, we identified pyrazine-pyridine A as a potent vascular endothelial growth factor inhibitor and pyrimidine-pyridine B as a moderately potent cyclin dependent kinase (CDK) inhibitor. A proposed combination of CGP-60474 and compound B led to the discovery of [1,3,5]triazine-pyridine as a new series of potent CDK inhibitors. Palladium-catalyzed C-C bond formation reactions, particularly the Negishi coupling reaction, were used to assemble various triazine-heteroaryl analogues effectively. Among them, compound 20 displayed high inhibitory potency at CDK1 (IC(50) = 0.021 microM), CDK2, and CDK5 and submicromolar potency at CDK4, CDK6, and CDK7. Compound 20 also displayed high potency at GSK-3beta. It demonstrated potent antiproliferative activity on various tumor cell lines, including HeLa, HCT-116, U937, and A375. When 20 was administered intraperitoneally at 150 and 125 mg/kg to nude mice bearing human A375 xenografts, the compound produced a significant survival increase. Molecular docking studies were conducted in an attempt to enhance the understanding of the observed structure-activity relationship.

Lewis acid-promoted transformation of 2-alkoxypyridines into 2-aminopyridines and their antibacterial activity. Part 2: Remarkably facile C–N bond formation

2-Alkoxy-3-cyano-4,6-diarylpyridines 1a,b which were synthesized by condensation of alpha,beta-unsaturated ketones with malononitrils were subjected to Lewis acid-catalyzed nucleophilic displacement reaction with various amines to afford the corresponding 2-aminopyridines 3-21. The potency of the results as antibacterial agents has been evaluated. The structure of the newly prepared compounds was assessed by microanalysis, IR, and NMR spectra. Molecular modeling and QSAR methods are used to study the antibacterial activity of the active compounds by means of the molecular mechanic method.