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Heterocyclic compounds with oxazole and imidazole rings in their structure have disclosed momentous biological aptitudes. Taking into account their superlative attributes, the present study was designed to introduce a new synthetic scheme to make new derivatives with tremendous futuristic pharmacological potentialities. Series of Oxazolones were synthesized by using substituted benzaldehyde with benzyl halides to produce respective benzaldehyde derivatives 1 (a-d) which further reacted with hippuric acid to yield oxazolones 2 (a-e). Newly synthesized oxazolones then reacted with 4-chloroaniline to yield corresponding imidazolones 3 (a-e). All the compounds were characterized by using FTIR and NMR spectroscopic techniques. Docking studies of Compounds were conducted using AutoDock Vina and analyzed with PYMOL. All synthesized oxazolone and imidazolone derivatives exhibited antioxidant potential, demonstrated by their IC50 values compared to ascorbic acid standard. Oxazolone derivatives (2a-2e) exhibited good acetyl cholinesterase inhibitory potential whereas Imidazolone series did not show significant inhibition as shown by their IC50 values compared to donepezil as a standard. Docking studies of all compounds against acetylcholinesterase demonstrated favorable binding affinity, indicating their potential for further in-vivo studies. It is notable that novel compounds of both oxazolones and Imidazolone series exhibited antioxidant potential with maximum percentage inhibition of 75.9 (IC50 12.9 ± 0.0573 µM/mL) by compound 2d while compound 2a showed AChE inhibitory potential with maximum %age inhibition of 75.49 (IC50 7.8 ± 0.0218 µM/mL).Communicated by Ramaswamy H. Sarma.

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We synthesized seven (Z)-benzylidene-2-(E)-styryloxazol-5(4H)-ones derivatives of cinnamic acid and evaluated the ability of these compounds to inhibit human acetylcholinesterase (hAChE). The most potent compound was evaluated for cognitive improvement in short-term memory. The seven compounds reversibly inhibited the hAChE between 51 and 75% at 300 µM, showed an affinity (Ki) from 2 to 198 µM, and an IC50 from 9 to 246 µM. Molecular docking studies revealed that all binding moieties are involved in the non-covalent interactions with hAChE for all compounds. In addition, in silico pharmacokinetic analysis was carried out to predict the compounds' blood-brain barrier (BBB) permeability. The most potent inhibitor of hAChE significantly improved cognitive impairment in a modified Y-maze test (5 µmol/kg) and an Object Recognition Test (10 µmol/kg). Our results can help the rational design of hAChE inhibitors to work as potential candidates for treating cognitive disorders.

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The 3,4-dihydrocoumarin derivatives were obtained from 2-alkyl phenols and oxazolones via C-H oxidation and cyclization cascade in the presence of silver oxide (Ag2O) and p-toluenesulfonic acid as a Brønsted acid catalyst. This approach provides a one-pot strategy to synthesize the multisubstituted 3,4-dihydrocoumarins with moderate to high yields (64-81%) and excellent diastereoselectivity (>20:1).

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A new route to bicyclic γ-lactams was found, which was proposed as a three-component cyclization of ethyl trifluoropyruvate with methyl ketones and 1,2-, 1,3-amino alcohols. As a result, a series of trifluoromethyl-substituted tetrahydropyrrolo [2,1-b]oxazol-5-ones and tetrahydropyrrolo[2,1-b][1,3]oxazine-6-ones was synthesized, in which the substituent at the nodal carbon atom was varied. The introduction of a twofold excess of ethyl trifluoropyruvate in reactions with amino alcohols and acetone made it possible to obtain the same bicycles, but functionalized with a hydroxyester fragment, which are formed due to four-component interactions of the reagents. Transformations with 2-butanone and aminoethanol lead predominantly to similar bicycles, while an analogous reaction with aminopropanol gives N-hydroxypropyl-2,3-dihydropyrrol-5-one. Almost all bicycles are formed as two diastereomers, the structure of which was determined using 1H, 19F, 13C NMR spectroscopy, including two-dimensional experiments and XRD analysis. A domino mechanism for the formation of tetrahydropyrrolo[2,1-b]oxazacycles was proposed, which was confirmed by their stepwise synthesis through the preliminary preparation of the aldol and bis-aldol from ethyl trifluoropyruvate and methyl ketones.

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The cycloisomerization of alkyne-tethered N-benzoyloxycarbamates to 2-(3H)oxazolones is described. Two catalytic systems are tailored for intramolecular 5-exo-alkyne carboxyamidation and concomitant alkene isomerization. PtCl2 /CO (5 mol%, toluene, 100 °C) promotes both carboxyamidation and alkene isomerization but has a limited substrate scope. On the other hand, FeCl3 (5 mol%, CH3 CN, 100 °C) promotes carboxyamidation effectively but a cocatalyst is required for the exocyclic alkene isomerization. Thus, a two-step one-pot protocol has been developed for a broader reaction scope, which involves FeCl3 -catalyzed carboxyamidation and base-induced alkene isomerization. Crossover experiments suggest that these reactions proceed mainly through a mechanism involving acylnitrenoid intermediates rather than carbenoid intermediates.

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The goal of the work reported here was to amplify the fluorescent properties of 4-aryliden-5(4H)-oxazolones by suppression of the hula-twist non-radiative deactivation pathway. This aim was achieved by simultaneous bonding of a Pd center to the N atom of the heterocycle and the ortho carbon of the arylidene ring. Two different 4-((Z)-arylidene)-2-((E)-styryl)-5(4H)-oxazolones, the structures of which are closely related to the chromophore of the Kaede protein and substituted at the 2- and 4-positions of the arylidene ring (1a OMe; 1b F), were used as starting materials. Oxazolones 1a and 1b were reacted with Pd(OAc)2 to give the corresponding dinuclear orthometalated palladium derivates 2a and 2b by regioselective C-H activation of the ortho-position of the arylidene ring. Reaction of 2a (2b) with LiCl promoted the metathesis of the bridging carboxylate by chloride ligands to afford dinuclear 3a (3b). Mononuclear complexes containing the orthopalladated oxazolone and a variety of ancillary ligands (acetylacetonate (4a, 4b), hydroxyquinolinate (5a), aminoquinoline (6a), bipyridine (7a), phenanthroline (8a)) were prepared from 3a or 3b through metathesis of anionic ligands or substitution of neutral weakly bonded ligands. All species were fully characterized and the X-ray determination of the molecular structure of 7a was carried out. This structure has strongly distorted ligands due to intramolecular interactions. Fluorescence measurements showed an increase in the quantum yield (QY) by up to one order of magnitude on comparing the free oxazolone (QY < 1%) with the palladated oxazolone (QY = 12% for 6a). This fact shows that the coordination of the oxazolone to the palladium efficiently suppresses the hula-twist deactivation pathway.

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The five membered heterocyclic oxazole group plays an important role in drug discovery. Oxazolones present a wide range of biological activities. In this article the synthesis of 4-substituted-2-phenyloxazol-5(4H)-ones from the appropriate substituted aldehydes via an Erlenmeyer-Plochl reaction is reported. Subsequently, the corresponding benzamides were produced via a nucleophilic attack of a secondary amine on the oxazolone ring applying microwave irradiation. The compounds are obtained in good yields up to 94% and their structures were confirmed using IR, 1H-NMR, 13C-NMR and LC/MS data. The in vitro anti-lipid peroxidation activity and inhibitory activity against lipoxygenase and trypsin induced proteolysis of the novel derivatives were studied. Inhibition of carrageenin-induced paw edema (CPE) and nociception was also determined for compounds 4a and 4c. Oxazolones 2a and 2c strongly inhibit lipid peroxidation, followed by oxazolones 2b and 2d with an average inhibition of 86.5%. The most potent lipoxygenase inhibitor was the bisbenzamide derivative 4c, with IC50 41 µΜ. The benzamides 3c, 4a-4e and 5c were strong inhibitors of proteolysis. The replacement of the thienyl moiety by a phenyl group does not favor the protection. Compound 4c inhibited nociception higher than 4a. The replacement of thienyl groups by phenyl ring led to reduced biological activity. Docking studies of the most potent LOX inhibitor highlight interactions through allosteric mechanism. All the potent derivatives present good oral bioavailability.

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The stereoselective synthesis of truxillic bis-amino esters from polyfunctional oxazolones is reported. The reaction of 4-((Z)-arylidene)-2-(E)-styryl-5(4H)-oxazolones 2 with Pd(OAc)2 resulted in ortho-palladation and the formation of a dinuclear open-book complexes 3 with carboxylate bridges, where the Pd atom is C^N bonded to the oxazolone. In 3 the two exocyclic C=C bonds of the oxazolone are in a face-to-face arrangement, which is optimal for their [2 + 2] photocycloaddition. Irradiation of dimers 3 in CH2Cl2 solution with blue light (465 nm) promoted the chemo- and stereoselective [2 + 2] photocycloaddition of the exocyclic C=C bonds and the formation of cyclobutane-containing ortho-palladated complexes 4. Treatment of 4 with CO in a MeOH/NCMe mixture promoted the methoxycarbonylation of the palladated carbon and the release of the corresponding ortho-functionalized 1,3-diaminotruxillic bis-amino esters 5 as single isomers.

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Novel azole derivatives 3-30 were designed, synthesized, and screened for their antitumor activity on HepG2 cell line. The cytotoxicity screening demonstrated that imidazolone 8 and triazoles 25 and 29 exhibited more potent cytotoxic activities by 1.21-, 4.75-, and 1.8-fold compared to Sorafenib (SOR). Furthermore, vascular endothelial growth factor receptor-2 (VEGFR-2) enzyme inhibition assay declared that compounds 25 and 29 had inhibitory activity at the nanomolar concentration. Moreover, the tested compounds exhibited good ß-tubulin (TUB) polymerization inhibition percentages. In addition, DNA flow cytometry analysis over HepG2 cells indicated that triazoles 25 and 29 demonstrated arrest at G1 and G2/M phase of the cell cycle and induced apoptotic activity by increasing sub-G1 phase. Finally, mechanistic studies of the proapoptotic activities of compounds 8, 10, 11, 25, and 29 indicated that they induced upregulation of P53, Fas/Fas-ligand, and BAX/BCL-2 ratio expression that resulted in increasing the active caspase 3/7 percentages and trigger apoptosis.

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Acetylcholine esterase (AChE) is one of the targeted enzymes in the therapy of important neurodegenerative diseases such as Alzheimer's disease. Many studies on carbazole- and oxazolone-based compounds have been conducted in the last decade due to the importance of these compounds. New carbazole-bearing oxazolones were synthesized from several carbazole aldehydes and p-nitrobenzoyl glycine as AChE inhibitors by the Erlenmeyer reaction in the present study. The inhibitory effects of three carbazole-bearing oxazolone derivatives on AChE were studied in vitro and the experimental results were modeled using artificial neural network (ANN). The developed ANN provided sufficient correlation between several dependent systems, including enzyme inhibition. The inhibition data for AChE were modeled by a two-layered ANN architecture. High correlation coefficients were observed between the experimental and predicted ANN results. Synthesized carbazole-bearing oxazolone derivatives inhibited AChE under in vitro conditions, and further research involving in vivo studies is recommended. An ANN may be a useful alternative modeling approach for enzyme inhibition.

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BACKGROUND: Oxazolones and 1,2,3-triazoles are among the extensively studied heterocycles in medicinal chemistry. Both of these moieties are reported to possess a broad spectrum of biological activity including antimicrobial. OBJECTIVE: The objective of the current work is to design, synthesize and antimicrobial evaluation of some new oxazolone-1,2,3-triazole hybrids. METHODS: The designed oxazolone-1,2,3-triazole hybrids were synthesized using copper(I)-catalyzed azide-alkyne cycloaddition. The antimicrobial evaluation was carried out using serial dilution method. RESULTS: Most of the synthesized hybrids showed significant antimicrobial properties. Some of the compounds were found to be possessing better or comparable activity to that of the standards used. The docking simulations results are also in agreement with the antimicrobial activity data. CONCLUSION: Sixteen new hybrids were synthesized and tested in vitro for their antimicrobial activity. Some of the tested compounds exhibited promising antimicrobial activity and could be utilized for the development of the lead compounds for new and more potent antimicrobial drugs.

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O-Heterocycles have been explored in the field of medicinal chemistry for a long time, but their significance has not been duly recognised and they are often shunned in favour of N-heterocycles. The design of bioactive molecules for nearly every pathophysiological condition is primarily focused on novel N-heterocycles. The main reasons for such bias include the ease of synthesis and possible mimicking of physiological molecules by N-heterocycles. But considering only this criterion rarely provides breakthrough molecules for a given disease condition, and instead the risks of toxicity or side effects are increased with such molecules. On the other hand, owing to improved synthetic feasibility, O-heterocycles have established themselves as equally potent lead molecules for a wide range of pathophysiological conditions. In the last decade there have been hundreds of reports validating the fact that equally potent molecules can be designed and developed by using O-heterocycles, and these are also expected to have comparably low toxicity. Even so, researchers tend to remain biased toward the use of N-heterocycles over O-heterocycles. Thus, this review provides a critical analysis of the synthesis and medicinal attributes of O-heterocycles, such as pyrones, oxazolones, furanones, oxetanes, oxazolidinones, and dioxolonones, and others, reported in the last five years, underlining the need for and the advantages guiding researchers toward them.

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We have developed a new method to prepare 4-acetoxy substituted 5(4H)-oxazolones by direct oxidation of N-benzoyl amino-acids using hypervalent iodine. The method is efficient, economical and easy to perform for the synthesis of quaternary substituted amino acid derivatives. We used online FTIR monitoring techniques to analyze the reaction, and gave a plausible reaction mechanism.

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The formation of peptides upon 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)-promoted activation of N-carbamoylamino acids (CAA), was considered in the scope of our recent works on carbodiimide promoted C-terminus elongation of peptides in a prebiotic context. Thus EDC promoted activation of CAA derivatives of Tyr(Me) or Ala in dilute aqueous medium pH 5.5-6.5 in the presence of excess of AA, resulted in peptide formation by C-terminus activation/elongation. Kinetic results similar to those of EDC-mediated activation of N-acyl-AA lead us to postulate the formation of a 2-amino-5(4H)-oxazolone intermediate by cyclization of the activated CAA, in spite of the absence of epimerization occurred at CAA residues. Thus, in a prebiotic context, CAA may have played a similar role as N-acyl-AA in the initiation of C-terminus peptide elongation.

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4-(4'-acetyloxy-3'-methoxybenzylidene)-5-oxazolone fluorescent molecules bearing four different aryl groups attached to the 2-position of 5-oxazolone ring have been investigated by spectrophotometric and potentiometric techniques in solution media. The acidity constants (pKa) of the fluorescent molecules were precisely determined in acetone, acetonitrile, dimethylformamide and in 1:1 mixture of toluene-isopropanol. The studied derivatives were titrated with tetrabutylammonium hydroxide and non-aqueous perchloric acid by scanning the basic and acidic region of the pH scale. A computerizable derivative method was used in order to descript precisely the end point and pKa values. The molecules investigated performed well-shaped and stoichiometric potentiometric titration curves.

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Azlactones (also known as oxazolones) are heterocycles usually employed in the stereoselective synthesis of α,α-amino acids, heterocycles and natural products. The versatility of the azlactone scaffold arises from the numerous reactive sites, allowing its application in a diversity of transformations. This review aims to cover classical and recent applications of oxazolones, especially those involving stereoselective processes. After a short introduction on their structures and intrinsic reactivities, dynamic kinetic resolution (DKR) processes as well as reactions involving stereoselective formation of a new σ C-C bond, such as alkylation/allylation/arylation, aldol, ene, Michael and Mannich reactions will be exposed. Additionally, cycloadditions, Steglich rearrangement and sulfenylation reactions will also be discussed. Recent developments of the well-known Erlenmeyer azlactones will be described. For the most examples, the proposed mechanism, activation modes and/or key reaction intermediates will be exposed to rationalize both the final product and the observed stereochemistry. Finally, this review gives an overview of the synthetic utility of oxazolones.

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A mild and practical method for the construction of heterocycles from N-substituted 2-oxazolones through cascade, BF3 ⋅Et2 O/H2 O-catalyzed reactions involving iminium ion generation and trapping by external or internal olefinic and aryl moieties is described. Mechanistic and computational studies revealed the strong protic acid HBF4 as the initiating catalyst for these cascade reactions. Providing access to novel molecular diversity, these processes may facilitate chemical biology studies, drug discovery efforts and natural products synthesis.

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Syntheses and structures are described for some alkylidene-substituted dihydrooxazolones and dihydroimidazoles derived from simple acylglycines. A second, triclinic, polymorph of 4-benzylidene-2-(4-methylphenyl)-1,3-oxazol-5(4H)-one, C17H13NO2, (I), has been identified and the structure of 2-methyl-4-[(thiophen-2-yl)methylidene]-1,3-oxazol-5(4H)-one, C9H7NO2S, (II), has been rerefined taking into account the orientational disorder of the thienyl group in each of the two independent molecules. The reactions of phenylhydrazine with 2-phenyl-4-[(thiophen-2-yl)methylidene]-1,3-oxazol-5(4H)-one or 2-(4-methylphenyl)-4-[(thiophen-2-yl)methylidene]-1,3-oxazol-5(4H)-one yield, respectively, 3-anilino-2-phenyl-5-[(thiophen-2-yl)methylidene]-3,5-dihydro-4H-imidazol-4-one, C10H15N3OS, (III), and 3-anilino-2-(4-methylphenyl)-5-[(thiophen-2-yl)methylidene]-3,5-dihydro-4H-imidazol-4-one, C21H17N3OS, (IV), which both exhibit orientational disorder in their thienyl groups. The reactions of 2-phenyl-4-[(thiophen-2-yl)methylidene]-1,3-oxazol-5(4H)-one with hydrazine hydrate or with water yield, respectively, N-[3-hydrazinyl-3-oxo-1-(thiophen-2-yl)prop-1-en-2-yl]benzamide and 2-(benzoylamino)-3-(thiophen-2-yl)prop-2-enoic acid, which in turn react, respectively, with thiophene-2-carbaldehyde to form 2-phenyl-5-[(thiophen-2-yl)methylidene]-3-{[(E)-(thiophen-2-yl)methylidene]amino}-3,5-dihydro-4H-imidazol-4-one, C19H13N3OS2, (V), which exhibits orientational disorder in only one of its thienyl groups, and with methanol to give methyl (2Z)-2-(benzoylamino)-3-(thiophen-2-yl)prop-2-enoate, C15H13NO3S, (VI). There are no direction-specific intermolecular interactions in the crystal structure of the triclinic polymorph of (I), but the molecules of (II) are linked by two independent C-H···O hydrogen bonds to form C2(2)(14) chains. Compounds (III) and (IV) both form centrosymmetric R2(2)(10) dimers built from N-H···O hydrogen bonds, while compound (V) forms a centrosymmetric R2(2)(10) dimer built from C-H···O hydrogen bonds. In the structure of compound (VI), a combination of N-H···O and C-H···π(arene) hydrogen bonds links the molecules into sheets. Comparisons are made with some similar compounds.

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In the course of solid-state photoreactions, a single crystal (SC) of the reactant can be transformed into an SC of the product or it can lose crystallinity and become amorphous. In-between these two scenarios exist the reconstructive phase transformations, where upon irradiation, the reactant SC becomes a powder or an SC with increased mosaicity. We present a detailed description of reconstructive photodimerization, where the structural changes are directly correlated with the disintegration process. The kinetics of the reaction is explained by two kinetic regimes, forming an autocatalytic autoinhibition photoreaction set with high quantum yield. In addition, the photoreaction pathways were studied theoretically.

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A cyclic form of N(6)-threonylcarbamoyladenosine bearing an oxazolone moiety (ct(6)A) was discovered very recently at the position 37 in several tRNA sequences. Our study on the synthesized 5',3',2'-O-acetylated derivative of ct(6)A confirmed high stability of the modified nucleoside under physiological conditions (PBS buffer, pH 7.4) and revealed remarkable stability of the oxazolone ring in acidic (100mM HCl, pH 1) and basic (0.1mM NaOH, pH 10) conditions. This feature may allow for the post-synthetic conversion of t(6)A into ct(6)A in assembled oligoribonucleotides.

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