Discovery of a new pyrido[2,3-d]pyridazine-2,8-dione derivative as a potential anti-inflammatory agent through COX-1/COX-2 dual inhibition

In this paper, we present the design and synthesis of a novel series of pyrido[2,3-d]pyridazine-2,8-dione derivatives via the annulation of the 2-pyridone pattern. The synthesized derivatives were evaluated for in vivo anti-inflammatory activity using an ear edema model. Compound 7c, which showed a greater inhibition of ear edema (82%), was further tested for its in vitro COX-1/COX-2 inhibitory activity. Compound 7c showed similar inhibitory activities against COX-1 and COX-2 isoenzymes. The structural features that ensure the dual inhibition of COX-1 and COX-2 were elucidated using molecular docking studies. Overall, the ring closing of 2-pyridone pattern I transformed this highly selective COX-2 inhibitor into a dual COX inhibitor (7c), which could serve as a model for determining selectivity for COX-2.

Regiodivergent Synthesis of 3,4- and 4,5-Disubstituted N-Methylpyrazoles from 4-Acyl-1H-pyrrole-2,3-dione and Methylhydrazine

A simple, efficient and highly regioselective method for the preparation of 3,4- and 4,5-disubstituted N-methylpyrazoles in a one-pot procedure is reported. The methodology developed was based on the regiochemical control of the reaction of 4-acyl-1H-pyrrole-2,3-diones and methylhydrazine with an influence of the addition or absence of acid and the substrate structure.

Efficient synthesis and antitumor evaluation of 4-aminomethyl-N-arylpyrazoles: Discovery of potent and selective agents for ovarian cancer

A new one-pot two-step sequential methodology for synthesis of novel 3-carboxyethyl 4-[(tert-butylamino)methyl]-N-arylpyrazole derivatives is reported. One-pot transformation of β-enamino diketones and arylhydrazines generated 4-iminium-N-arylpyrazole salt intermediates in situ, which were easily transformed into 4-[(tert-butylamino)methyl]-N-arylpyrazole derivatives by NaBH₃CN. The products could be isolated in the free or hydrochloride salt forms. Also, it was possible to obtain the products in the zwitterionic form by ester group hydrolysis. Furthermore, all synthesised compounds were evaluated in vitro against a panel of eight human tumor cell lines. The 4-[(tert-butylamino)methyl]-N-arylpyrazole derivatives were much more powerful than the hydrochloride and zwitterionic forms. Moreover, the results suggest that the N-aryl group at the pyrazole ring is vital for modulating antiproliferative activity. The 3-carboxyethyl 4-[(tert-butylamino)methyl]-N-phenylpyrazoles 3a-g exhibited higher inhibitory activities against OVCAR-3, with GI₅₀ values of 0.013-8.78 μM, and lower inhibitory activities against normal human cell lines. Molecular docking was performed to evaluate the probable binding mode of 3a into active site of CDK2.

Antiparasitic activities of novel pyrimidine N-acylhydrazone hybrids

In this article, a series of 29 new pyrimidine N-acylhydrazone hybrids were synthesized and evaluated in vitro against Leishmania amazonensis and Trypanosoma cruzi protozoa that cause the neglected diseases cutaneous leishmaniasis and Chagas disease, respectively. Eight of the target compounds showed significant antiprotozoal activities with IC₅₀ values in 4.3-33.6 μM range. The more active compound 4f exhibited selectivity index greater than 15 and drug-like properties based on Lipinski's rule.

Synthesis of novel 3,5,6-trisubstituted 2-pyridone derivatives and evaluation for their anti-inflammatory activity

The inflammatory response is the reaction of living tissue to an injury of a foreign nature, such as infection and irritants, and occurs as part of the body's natural defence response. Compounds capable of inhibiting cyclooxygenase (COX) enzymes, especially COX-2, have great potential as anti-inflammatory agents. Herein we present the regioselective synthesis of 49 novel compounds based on the 2-pyridone nucleus. The topical anti-inflammatory activity of seventeen compounds was evaluated in mice by croton oil (CO) induced ear edema assay. Most of the compounds exhibited a high level of in vivo anti-inflammatory activity, reducing ear edema and myeloperoxidase (MPO) activity. The most active compounds (2a and 7a) were inhibitors of COX enzymes. Compound 2a selectively inhibited the COX-2, while 7a was nonselective. Further, the compound 2a showed effective binding at the active site of COX-2 co-crystal by docking molecular study.

Oral treatment with T6-loaded yeast cell wall particles reduces the parasitemia in murine visceral leishmaniasis model

Yeast cell wall particles isolated from Saccharomyces cerevisiae (scYCWPs) have a rich constitution of β-glucan derived from the cell wall. After removing intracellular contents, β-glucan molecules are readily recognized by dectin-1 receptors, present on the cytoplasmic membrane surface of the mononuclear phagocytic cells and internalized. Leishmania spp. are obligate intracellular parasites; macrophages are its primary host cells. An experimental murine model of visceral leishmaniasis caused by L. infantum was used to evaluate the antileishmanial activity of oral administration of these particles. A low-water soluble thiophene previously studied in vitro against L. infantum was entrapped into scYCWPs to direct it into the host cell, in order to circumvent the typical pharmacokinetic problems of water-insoluble compounds. We found that scYCWPs + T6 reduced the parasitic burden in the liver and spleen. There was an increase in IFN-γ levels related to nitric oxide production, explaining the reduction of the L. infantum burden in the tissue. Histological analysis did not show signals of tissue inflammation and biochemical analysis from plasma did not indicate signals of cytotoxicity after scYCWPs + T6 treatment. These findings suggested that scYCWPs + T6 administered through oral route reduced the parasitic burden without causing toxic effects, satisfying requirements for development of new strategies to treat leishmaniasis.

Development of methodologies for the regioselective synthesis of four series of regioisomer isoxazoles from β-enamino diketones

Four methodologies are reported for the regioselective synthesis of four series of regioisomer isoxazoles from cyclocondensation of β-enamino diketones and hydroxylamine hydrochloride. Regiochemical control was achieved by varying reaction conditions and substrate structure. The mild reaction conditions used to access 4,5-disubstituted, 3,4-disubtituted, and 3,4,5-trisubstituted regioisomer isoxazoles, as well as the pharmacological and synthetic potential of the products, make these novel methodologies very powerful.

Efficient and regioselective synthesis of isoxazoles was demonstrated through cyclocondensation of β-enamino diketones with hydroxylamine: four of the six possible regioisomers were obtained.

Regiochemistry of cyclocondensation reactions in the synthesis of polyazaheterocycles

The syntheses of several polyazaheterocycles are demonstrated. The cyclocondensation reactions between β-enaminodiketones [CCl₃C(O)C(=CNMe₂)C(O)-CO₂Et] and aromatic amidines resulted in glyoxalate-substituted pyrido[1,2-a]pyrimidinone, thiazolo[3,2-a]pyrimidinone and pyrimido[1,2-a]benzimidazole. Pyrazinones and quinoxalinones were obtained through the reaction of these glyoxalates with ethylenediamine and 1,2-phenylenediamine derivatives. On the other hand, the reaction of glyoxalates with amidines did not lead to the formation of imidazolones, but rather N-acylated products were obtained. All the products were isolated in good yields. DFT-B3LYP calculations provided HOMO/LUMO coefficients, charge densities, and the stability energies of the intermediates, and from these data it was possible to explain the regiochemistry of the products obtained. Additionally, the data were a useful tool for elucidating the reaction mechanisms.

Synthesis and evaluation against Leishmania amazonensis of novel pyrazolo[3,4-d]pyridazinone-N-acylhydrazone-(bi)thiophene hybrids

A new series of pyrazolo[3,4-d]pyridazin-7-one derivatives were synthesised and evaluated for their in vitro antileishmanial activity against Leishmania amazonensis promastigote and axenic amastigote forms. The results showed that the pyrazolo[3,4-d]-pyridazin-7-one-N-acylhydrazone-(bi)thiophene hybrids 5b, 6b and 6d exhibit better antileishmanial activity with IC₅₀ 84.96, 3.63 and 10.79 μM, against the promastigote form and IC₅₀ 32.71, 2.32 and >100 μM against the axenic amastigote form, respectively. The active compounds had their cytotoxicity tested against macrophages and fibroblast cells with a higher selectivity index than 10 for compounds 6b and 6d. Molecular docking studies were performed for all active compounds using the enzyme trypanothione reductase (TR) to investigate a possible action mechanism. The results suggested that active compounds had interactions with the residues of amino acids Gly 13, Thr 51, Thr 160, Gly 161, Tyr 198, Arg 287, Asp 327, Thr 335, which may inhibit the enzyme TR.

Theoretical and experimental investigation of the polyeletrophilic β-enamino diketone: straightforward and highly regioselective synthesis of 1,4,5-trisubstituted pyrazoles and pyrazolo[3,4-d]pyridazinones

A highly efficient regioselective synthesis of 1,4,5-trisubstituted pyrazoles and pyrazolo[3,4-d]pyridazinones from enamino diketone along with a theoretical and experimental study of the chemical reactivity enamino diketone.

NMR spectroscopy and theoretical calculations in the conformational analysis of 1-methylpyrrolidin-2-one 3-halo-derivatives

This study reports the results of ab initio and density functional theory (DFT) electronic structure calculations as well as (3)J(HH) experimental and calculated coupling constant data obtained in the investigation of the conformational equilibrium of 3-halo-derivatives of 1-methylpyrrolidin-2-one. The five-membered ring assumes an envelope conformation owing to the plane of formation of the O═C-N-R bond, with C4 forming the "envelope lid". When the conformation changes, the "lid" alternates between positions above and below the amide plane. The α-carbonyl halogen assumes two positions: a pseudo-axial and a pseudo-equatorial. In the gaseous phase, the calculations indicate that the pseudo-axial conformer is more stable and preferable going down the halogen family. Natural bond orbital analysis showed that electronic delocalization is significant only for the iodo derivative. In the other derivatives, the electrostatic repulsion between oxygen and the halogen determines the conformational equilibrium. When the solvated molecule was taken into account, the pseudo-equatorial conformer population increased with the relative permittivity of the solvent. This variation was strong in the fluoro derivative, and the preference was inverted. In the chlorine derivative, the two populations became closer in methanol and acetonitrile. In the bromine and iodine derivatives, the percentage of pseudo-equatorial conformer increased only slightly owing to the dipole moment of the conformation: the pseudo-equatorial conformation has a greater dipole moment and thus is stable in media with high relative permittivity.

The conformational analysis of 2-halocyclooctanones

The establishment of the most stable structures of eight membered rings is a challenging task to the field of conformational analysis. In this work, a series of 2-halocyclooctanones were synthesized (including fluorine, chlorine, bromine and iodine derivatives) and submitted to conformational studies using a combination of theoretical calculation and infrared spectroscopy. For each compound, four conformations were identified as the most important ones. These conformations are derived from the chair-boat conformation of cyclooctanone. The pseudo-equatorial (with respect to the halogen) conformer is preferred in vacuum and in low polarity solvents for chlorine, bromine and iodine derivatives. For 2-fluorocyclooctanone, the preferred conformation in vacuum is pseudo-axial. In acetonitrile, the pseudo-axial conformer becomes the most stable for the chlorine derivative. According to NBO calculations, the conformational preference is not dictated by electron delocalization, but by classical electrostatic repulsions.

Ultrasound promoted synthesis of 2-imidazolines in water: a greener approach toward monoamine oxidase inhibitors

A series of sixteen 2-substituted-2-imidazolines (where the substituent R=Ph, Me-4-Ph; MeO-4-Ph; (MeO)(2)-3,4-Ph; (MeO)(3)-3,4,5-Ph; Ph-4-O-C(O)-Ph; Cl-4-Ph; Cl-2-Ph; Cl(2)-2,4-Ph; NO(2)-4-Ph; NO(2)-3-Ph; Naphth-2-yl; Fur-2-yl; Benzofur-2-yl; Pyridin-2-yl; Quinolin-2-yl) has been synthesized from the reaction of the substituted-aldehydes and ethylenediamine by ultrasound irradiation with NBS in an aqueous medium in high yields (80-99%). The 2-imidazoline ability to inhibit the activity of the A and B isoforms of monoamine oxidase (MAO) was investigated and some of them showed potent and selective MAO inhibitory activity especially for the MAO-B isoform and could become promising candidates for future development.

2-(4,5-Dihydro-1,3-oxazol-2-yl)quinoline

The title compound, C(12)H(10)N(2)O, is approximately planar. The angle between the quinoline and 4,5-dihydro-oxazole ring systems is 11.91 (12)°. The mol-ecules pack into a herringbone array with no significant π-π inter-actions. The dihydro-oxazole N and O atoms are disordered over two positions, with almost equal site occupancy factors.

Ultrasound promoted synthesis of 5-hydroxy-5-trihalomethyl-4,5-dihydroisoxazoles and beta-enamino trihalomethyl ketones in water

A convenient method for the preparation of 5-hydroxy-5-trihalo-4,5-dihydroisoxazoles and beta-enamino trihalomethyl ketones, from the reaction of 1,1,1-trihalo-4-alkoxy-3-alken-2-ones with hydroxylamine and anilines, respectively, using water as solvent and under ultrasound irradiation is reported.

Endogenous glucocorticoids modulate neutrophil function in a murine model of haemolytic uraemic syndrome

Haemolytic uraemic syndrome (HUS) is caused by Shiga-toxin-producing Escherichia coli (STEC). Although, Shiga toxin type 2 (Stx2) is responsible for the renal pathogenesis observed in patients, the inflammatory response, including cytokines and polymorphonuclear neutrophils (PMN), plays a key role in the development of HUS. Previously, we demonstrated that Stx2 injection generates an anti-inflammatory reaction characterized by endogenous glucocorticoid (GC) secretion, which attenuates HUS severity in mice. Here, we analysed the effects of Stx2 on the pathogenic function of PMN and the potential role of endogenous GC to limit PMN activation during HUS development in a murine model. For this purpose we assessed the functional activity of isolated PMN after in vivo treatment with Stx2 alone or in simultaneous treatment with Ru486 (GC receptor antagonist). We found that Stx2 increased the generation of reactive oxygen intermediates (ROI) under phobol-myristate-acetate (PMA) stimulation and that the simultaneous treatment with Ru486 strengthened this effect. Conversely, both treatments significantly inhibited in vitro phagocytosis. Furthermore, Stx2 augmented in vitro PMN adhesion to fibrinogen (FGN) and bovine serum albumin (BSA) but not to collagen type I (CTI). Stx2 + Ru486 caused enhanced adhesion to BSA and CTI compared to Stx2. Whereas Stx2 significantly increased migration towards N-formyl-methionyl-leucyl-phenylalanine (fMLP), Stx2 + Ru486 treatment enhanced and accelerated this process. The percentage of apoptotic PMN from Stx2-treated mice was higher compared with controls, but equal to Stx2 + Ru486 treated mice. We conclude that Stx2 activates PMN and that the absence of endogenous GC enhances this activation suggesting that endogenous GC can, at least partially, counteract PMN inflammatory functions.