The development of new isoxazolone based inhibitors of tumor necrosis factor-alpha (TNF-α) production

A novel μ3-CO3 bridged linear polymeric Cu-complex ([Cu3(DMAP)8(μ3-CO3)2]I2) n ·xH2O: synthesis, characterization and catalytic applications in the synthesis of phenoxypyrimidines and arylthiopyrimidines via C-O and C-S cross-coupling reactions

This manuscript reports on the synthesis and characterization of a new polymeric copper complex ([Cu3(DMAP)8(μ3-CO3)2]I2) n ·xH2O and its successful application in C-O and C-S cross coupling reactions for the synthesis of biologically important phenoxypyrimidine and arylthiopyrimidine scaffolds. In an attempt to synthesize [Cu(DMAP)4I]I by adopting a procedure reported by Roy et al. with slight modification, the authors discovered a new polymeric Cu-complex that contains μ3-CO3 bridges. The polymeric linear structure of the complex was established using single crystal X-ray analysis. FT-IR, UV-vis and DSC studies were also performed on the polymeric complex. This novel polymeric Cu-complex was found to efficiently catalyse C-O/C-S cross coupling reactions between chloropyrimidines and phenols/thiophenols in an aqueous medium within a short reaction time, delivering their corresponding phenoxypyrimidines and arylthiopyrimidines. Using this protocol, 22 phenoxypyrimidines and 6 arylthiopyrimidines were successfully synthesized. The synthesized novel compounds were well characterized using 1H and 13C NMR spectroscopy and HRMS analysis and were screened for their drug-likeness properties using the SwissADME webtool.

Synthesis of Isoxazol-5(2H)-one Derivatives via (tBuO)2Mg Promoted [3 + 2] Annulations of δ-Acetoxy Allenoates with Hydroxylamine

Herein, an efficient (tBuO)2Mg promoted [3 + 2] annulation of δ-acetoxy allenoates with N-benzylhydroxylamine has been developed. This method provides a concise and facile protocol to synthesize vinylated isoxazol-5(2H)-one derivatives stereospecifically in a broad substrate scope with high efficiency (31 examples, up to 87% yield).

Copper-Catalyzed Direct Syntheses of Phenoxypyrimidines from Chloropyrimidines and Arylboronic Acids: A Cascade Avenue and Unconventional Substrate Pairs

This letter describes the first synthetic methodology for phenoxypyrimidines that avoids the direct use of phenols or their salts. In contrast to the general trend of delivering Suzuki-Miyaura cross-coupling products in reactions between aryl or alky halides and arylboronic acids, the substrate pairs used herein (chloropyrimidines and arylboronic acids) led to C-O bond formation under the reaction conditions. In total, 25 phenoxypyrimidines were successfully synthesized using the described protocol, 6 of which had a structural resemblance to etravirine.

Structural study and Hirshfeld surface analysis of (Z)-4-(2-meth-oxy-benzyl-idene)-3-phenyl-isoxazol-5(4H)-one

The title compound, C17H13NO3, adopts a Z configuration about the C=C bond. The isoxazole and meth-oxy-benzyl-idene rings are almost coplanar with a dihedral angle of 9.63 (7)° between them. In contrast, the phenyl substituent is twisted significantly out of the plane of the oxazole ring, with the two rings inclined to each other by 46.22 (4)°. The crystal structure features C-H⋯O, C-H⋯N and C-H⋯π hydrogen bonds and π-π contacts. An analysis of the Hirshfeld surfaces points to the importance of H⋯H, H⋯C/C⋯H and H⋯O/O⋯H contacts. The included surface areas of the title compound were compared to those of the isomeric structure (Z)-4-(4-meth-oxy-benzyl-idene)-3-phenyl-isoxazol-5(4H)-one [Zhang et al. (2015 ▸). CrystEngComm, 17, 7316-7322].

Crystal structure and Hirshfeld surface analysis of (Z)-3-methyl-4-(thio-phen-2-yl-methyl-idene)isoxazol-5(4H)-one

The title compound, C9H7NO2S crystallizes with two independent mol-ecules (A and B) in the asymmetric unit with Z = 8. Both mol-ecules are almost planar with a dihedral angle between the isoxazole and thio-phen rings of 3.67 (2)° in mol-ecule A and 10.00 (1) ° in mol-ecule B. The packing of mol-ecules A and B is of an ABAB⋯ type along the b-axis direction, the configuration about the C=C bond is Z. In the crystal, the presence of C-H⋯O, C-H⋯ N and π-π inter-actions [centroid-centroid distances of 3.701 (2) and 3.766 (2) Å] link the mol-ecules into a three-dimensional architecture. An analysis of Hirshfeld surfaces shows the importance of C-H⋯O and C-H⋯N hydrogen bonds in the packing mechanism of the crystalline structure.

Construction of isoxazolone-fused phenanthridines via Rh-catalyzed cascade C-H activation/cyclization of 3-arylisoxazolones with cyclic 2-diazo-1,3-diketones

A Rh(iii)-catalyzed cascade C-H activation/intramolecular cyclization of 3-aryl-5-isoxazolones with cyclic 2-diazo-1,3-diketones was described, leading to the formation of isoxazolo[2,3-f]phenanthridine skeletons. The protocol features the simultaneous one-pot formation of two new C-C/C-N bonds and one heterocycle in moderate-to-good yields with good functional group compatibility. It is amenable to large-scale synthesis and further transformation.

Magnetic sulfonated polysaccharides as efficient catalysts for synthesis of isoxazole-5-one derivatives possessing a substituted pyrrole ring, as anti-cancer agents

Four polysaccharides (chitosan, cellulose, starch, and pectin) were magnetized with magnetic iron oxide (Fe₃O₄) and then sulfonated (except pectin) with chlorosulfonic acid. The obtained solid acids were used as a catalyst in three-component reactions between N-substituted-2-formylpyrrole, hydroxylamine-hydrochloride, and β-keto esters for the synthesis of 4-(2-pyrrolyl) methylene-isoxazole-5-ones. The optimal catalyst system was selected and studied by IR, SEM, TEM and XRD methods. The diverse isoxazoline derivatives (obtained via a mild and simple approach) were also fully characterized by spectroscopic methods and screened for anti-cancer activities against HT-29 and MCF-7 colon and breast cancer and HEK 293 normal cells. The results revealed interesting anti-cancer activities.

Four magnetic polysaccharides containing acidic groups were used as catalysts for the synthesis of 4-(2-pyrrolyl) methylene-isoxazole-5-ones. The products showed anti-cancer activities.

Identification of potential TNF-α inhibitors: from in silico to in vitro studies

Tumor Necrosis Factor Alpha (TNF-α) is a pleiotropic pro-inflammatory cytokine. It act as central biological regulator in critical immune functions, but its dysregulation has been linked with a number of diseases. Inhibition of TNF-α has considerable therapeutic potential for diseases such as cancer, diabetes, and especially autoimmune diseases. Despite the fact that many small molecule inhibitors have been identified against TNF-α, no orally active drug has been reported yet which demand an urgent need of a small molecule drug against TNF-α. This study focuses on the development of ligand-based selective pharmacophore model to perform virtual screening of plant origin natural product database for the identification of potential inhibitors against TNF-α. The resultant hits, identified as actives were evaluated by molecular docking studies to get insight into their potential binding interaction with the target protein. Based on pharmacophore matching, interacting residues, docking score, more affinity towards TNF-α with diverse scaffolds five compounds were selected for in vitro activity study. Experimental validation led to the identification of three chemically diverse potential compounds with the IC₅₀ 32.5 ± 4.5 µM, 6.5 ± 0.8 µM and 27.4 ± 1.7 µM, respectively.

Investigation of antioxidant and anti-nociceptive potential of isoxazolone, pyrazolone derivatives, and their molecular docking studies

A series of new isoxazolone (3a-d) and pyrazolone (4a-d) derivatives were synthesized and assessed for their antioxidant and analgesic activity. Among synthesized compounds, 3b and 4b having nitro (NO₂ ) group show high analgesic activity at a dose of 6 mg/kg. Analgesic activity was further proceeded to explore the contribution of opioidergic mechanisms in the mediation of analgesic effects. Animals were administered with naloxone, a nonselective opioid inverse agonist, at the dose of 0.5 mg/kg. The results obtained suggested that the analgesic effects of the synthesized compounds were not reversed by naloxone, specifying that the compounds 3b and 4b do not follow the opioidergic pathway in order to relieve pain in animal models. Further, the binding interactions of compounds 3b and 4b were analyzed by docking them against nonopioid receptors COX-1 (3N8X) and COX-2 (3LN1). The results demonstrate the analgesic potential of isoxazolone and pyrazolone derivatives, especially compounds 3b and 4b can be considered promising lead molecules for further investigation and development into potent analgesic drugs. In addition, the antioxidant potential of compounds was also found to be related to better analgesic activity, thus providing an insight into the role of oxidative stress in the mediation of analgesia.

Regioselective catalytic asymmetric N-alkylation of isoxazol-5-ones with para-quinone methides

A highly regioselective and enantioselective N-alkylation of isoxazol-5-ones with para-quinone methides has been developed to obtain enantioenriched N-diarylmethane substituted isoxazolinones with high yields and enantioselectivities.

2,2′-((1,4-Dimethoxy-1,4-dioxobutane-2,3-diylidene)bis(azanylylidene))bis(quinoline-3-carboxylic acid)

The title compound, 2,2′-((1,4-dimethoxy-1,4-dioxobutane-2,3-diylidene)bis(azanylylidene))bis(quinoline-3-carboxylic acid) was synthesized from isoxazolo[3,4-b]quinolin-3(1H)-one and dimethyl acetylenedicarboxylate (DMAD) via a double aza-Michael addition followed by [1,3]-H shifts. The product was characterized by infrared and nuclear magnetic resonance spectroscopy, as well as elemental analysis and high-resolution mass spectrometry (HRMS). The proposed reaction mechanism was rationalized by density functional theory (DFT) calculations.

The tyrosinase inhibitory effects of isoxazolone derivatives with a (Z)-β-phenyl-α, β-unsaturated carbonyl scaffold

Thirteen (Z)-4-(substituted benzylidene)-3-phenylisoxazol-5(4H)-ones were designed to confirm the geometric effect of the double bond of the β-phenyl-α, β-unsaturated carbonyl scaffold on tyrosinase inhibitory activity. Compounds 1a-1m, which all possessed the (Z)-β-phenyl-α, β-unsaturated carbonyl scaffold, were synthesized using a tandem reaction consisting of an isoxazolone ring formation and a Knoevenagel condensation, and three starting materials, ethyl benzoylacetate, hydroxylamine and benzaldehydes. Some of the compounds showed inhibitory activity against mushroom tyrosinase as potent as compounds containing the "(E)"-β-phenyl-α, β-unsaturated carbonyl scaffold. Compounds 1c and 1m showed greater inhibitory activity than kojic acid: IC₅₀ = 32.08 ± 2.25 μM for 1c; IC₅₀ = 14.62 ± 1.38 μM for 1m; and IC₅₀ = 37.86 ± 2.21 μM for kojic acid. A kinetic study indicated that 1m inhibited tyrosinase in a competitive manner and that it probably binds to the enzyme's active site. In silico docking simulation supported binding of 1m (-7.6 kcal/mol) to the active site of tyrosinase with stronger affinity than kojic acid (-5.7 kcal/mol). Similar results were obtained using cell-based assays, and in B16F10 cells, compound 1m dose-dependently inhibited tyrosinase activity and melanogenesis. These results indicate the anti-melanogenic effect of compound 1m is due to the inhibition of tyrosinase and (Z)-isomer of the β-phenyl-α, β-unsaturated carbonyl scaffold can, like its congener the (E)-isomer, act as an excellent scaffold for tyrosinase inhibition.

Asymmetric Allylic Alkylation of β-Ketoesters with Allylic Alcohols by a Nickel/Diphosphine Catalyst

Asymmetric allylic alkylation of β-ketoesters with allylic alcohols catalyzed by [Ni(cod)2]/(S)-H8-BINAP was found to be a superior synthetic protocol for constructing quaternary chiral centers at the α-position of β-ketoesters. The reaction proceeded in high yield and with high enantioselectivity using various β-ketoesters and allylic alcohols, without any additional activators. The versatility of this methodology for accessing useful and enantioenriched products was demonstrated.

Organocatalytic asymmetric one-pot sequential conjugate addition/dearomative fluorination: synthesis of chiral fluorinated isoxazol-5(4H)-ones

A facile one-pot sequential conjugate addition/dearomative fluorination transformation of isoxazol-5(4H)-ones with nitroolefins and N-fluorobenzenesulfonimide (NFSI) has been developed. By using a bifunctional chiral tertiary amino-thiourea catalyst, a series of chiral fluorinated isoxazol-5(4H)-ones containing one fluorine-substituted quarternary stereocenter were obtained in high yields with high enantio- and diastereoselectivities. Further transformation of adducts could afford isoxazolidin-5-one derivatives with three contiguous stereocenters.

Isoxazolone based inhibitors of p38 MAP kinases

SAR of N-alkylated isoxazolones as p38 MAP kinase inhibitors was realized. The data herein show the possibility of transferring the SAR study and evaluation from N-1-substituted imidazole to isoxazolones. Optimization of substituent was realized.

The design and synthesis of novel alpha-ketoamide-based p38 MAP kinase inhibitors

We have identified a novel series of potent p38 MAP kinase inhibitors through structure-based design which due to their extended molecular architecture bind, in addition to the ATP site, to an allosteric pocket. In vitro ADME and in vivo PK studies show these compounds to have drug-like characteristics which could result in the development of an oral treatment for inflammatory conditions.

4-(4-Fluoro-phen-yl)-2-methyl-3-(1-oxy-4-pyridyl)isoxazol-5(2H)-one

The crystal structure of the title compound, C(15)H(11)FN(2)O(3), was determined as part of a study on the biological activity of isoxazolone derivatives as p38 mitogen-activated protein kinase (MAPK) inhibitors. The dihedral angles between rings are isoxazole/benzene = 55.0 (3)°, isoxazole/pyridine = 33.8 (2)° and benzene/pyridine = 58.1 (2)°.

4-[4-(4-Fluoro-phen-yl)-2-methyl-5-oxo-2,5-dihydro-isoxazol-3-yl]-1-methyl-pyridinium iodide-4-[3-(4-fluoro-phen-yl)-2-methyl-5-oxo-2,5-dihydro-isoxazol-4-yl]-1-methyl-pyridinium iodide (0.6/0.4)

The crystal structure of the title compound, C(16)H(16)FN(2)O(2) (+)·I(-), was determined as part of a study of the biological activity of isoxazolone derivatives as p38 mitogen-activated protein kinase (MAPK) inhibitors. The X-ray crystal structure of 4-[4-(4-fluoro-phenyl)-2-methyl-5-oxo-2,5-dihydro-isoxazol-3-yl]-1-methyl-pyridinium iodide showed the presence of the regioisomer 4-[3-(4-fluoro-phenyl)-2-methyl-5-oxo-2,5-dihydro-isoxazol-4-yl]-1-methyl-pyridinium iodide. The synthesis of the former compound was achieved by reacting 4-(4-fluoro-phenyl)-3-(4-pyridyl)isoxazol-5(2H)-one after treatment with Et(3)N in dimethyl-formamide, with iodo-methane. The unexpected formation of the regioisomer could be explained by a rearrangement occurring via aziridine of the isoxazolone compound. The regioisomers have site occupancies of 0.632 (4)/0.368 (4). The two six members rings make a dihedral angle of 66.8 (2)°.

On the Rearrangement in Dioxane/Water of (Z)-Arylhydrazones of 5-Amino-3-benzoyl-1,2,4-oxadiazole into (2-Aryl-5-phenyl-2H-1,2,3-triazol-4-yl)ureas: Substituent Effects on the Different Reaction Pathways

We have recently evidenced an interesting differential behavior in the reactivity in dioxane/water between the (Z)-2,4-dinitrophenylhydrazone (1a) and the (Z)-phenylhydrazone (1b) of 5-amino-3-benzoyl-1,2,4-oxadiazole. The former rearranges into the relevant triazole 2a only at pS+ > 4.5 while undergoing hydrolysis at high proton concentration (pS+ < 3.5); on the contrary, the latter rearranges into 2b in the whole pS+ range examined (0.1 < or = pS+ < or = 14.9). Thus, for a deeper understanding of these differences we have now collected kinetic data on the rearrangement in dioxane/water of a series of 3- or 4-substituted (Z)-phenylhydrazones (1c-l) of 5-amino-3-benzoyl-1,2,4-oxadiazole in a wide range of proton concentrations (pS+ 0.1-12.3) with the aim of gaining information about the effect of the substituent on the course of the reaction. All of the (Z)-arylhydrazones studied rearrange via three different reaction routes (specific-acid-catalyzed, uncatalyzed, and general-base-catalyzed), and the relevant results have been examined by means of free energy relationships.