Recent Progress in the Synthesis of Isoxazoles

: Isoxazole derivatives are aromatic five-membered ring heterocyclic compounds with one oxygen atom and one nitrogen atom at adjacent positions. These compounds have a broad spectrum of applications in medicinal chemistry, such as antimicrobial, anticancer, antitumor, antitubercular, analgesic, anti-inflammatory, antidepressant, and anticonvulsant activities and some of them are well-known drugs for the treatment of various diseases in the market. The use of this class of compounds in agriculture as herbicides, insecticides have been widely reported. In organic materials, these compounds have been applied as semiconductors, single-walled nanotubes, liquid crystals, chiral ligands, scaffolds for peptidomimetics, dyes, and high-temperature lubricants. Isoxazole derivatives also play an important role in organic synthesis because they can be converted into several important synthetic units such as β-hydroxy ketones, γ-amino alcohols, α,β-unsaturated oximes, β-hydroxy nitriles, α-hydroxy-β-diketones, and β-dicarbonyl compounds. Due to such a wide range of applicability, the synthesis of isoxazole derivatives has attracted intensive research from chemists. This review will focus on considerable studies on the synthesis of isoxazoles which date back from 2012.

Preclinical Study of Immunological Isoxazole Derivatives as a Potential Support for Melanoma Chemotherapy

(1) Background: Melanoma is an aggressive neoplasm derived from melanocyte precursors with a high metastatic potential. Responses to chemotherapy and immunotherapy for melanoma remain weak, underlining the urgent need to develop new therapeutic strategies for the treatment of melanoma. (2) Methods: The viability of NHDF and A375 cell cultures after the administration of the tested isoxazole derivatives was assessed after 24-h and 48-h incubation periods with the test compounds in the MTT test. ROS and NO scavenging analyses, a glycoprotein-P activity analysis, a migration assay, a test of apoptosis, and a multiple-criteria decision analysis were also performed. (3) Results: All compounds that were tested resulted in a slower migration of melanoma neoplastic cells. The mechanism of the antitumor activity of the tested compounds was confirmed—i.e., the pro-apoptotic activity of the compounds in A375 cell cultures. Compound O7K qualified for further research. (4) Conclusions: All the tested compounds inhibited the formation of melanoma metastases and demonstrated the ability to reduce the risk of developing drug resistance in the tumor. The MCDA results showed that O7K showed the strongest antitumor activity.

In-silico Studies, Synthesis, and Antibacterial Evaluation of Thiophene Linked Isoxazole Derivatives

In this work a series of thiophene linked isoxazole derivatives (LK1-LK8) was synthesized by cyclization of different substituted thienyl chalcones (PL1-PL8). The structures of the synthesized compounds were characterized by IR, 1H NMR and mass spectral data. These derivatives were evaluated for antibacterial activities. Compounds LK7 showed excellent antibacterial activities amongst the synthesized compounds with MIC value 6.75 µg/ml. Molecular docking of these linked isoxazole derivatives (LK1-LK8) was also performed with crystal structure of staph gyrase B 24kDa (PDB code: 5 4URM). All the isoxazole derivatives (LK1-LK8) were docked into same groove of the binding site of native co-crystallized (1R,4aS,5S,6S,8aR)-5-{[(5S)-1-(3-O-acetyl-4-O-carbamoyl-6-deoxy-2-O-methyl-alpha-L-talopyra nosy l)-4 hydroxy 2-oxo-5-(propan-2-yl)-2,5-dihydro-1H-pyrrol-3-yl]carbonyl}-6-methyl-4 1, 2, 3, 4 methylid-ene,4a,5,6,8a-octahydronaphthalen-1-yl2,6-dideoxy-3-C-[(1S)-1-{[(3,4-dichloro-5-methyl-1 H-pyrrol-2-yl) carbonyl]amino}ethyl]-beta-D-ribo-hexopyranoside) ligand for activity explanation and exhibited good ligand interaction and binding affinity were of range -2.04 to -4.34 kcal/mol.

Recent Progress in the Gold-Catalyzed Annulations of Ynamides with Isoxazole Derivatives via α-Imino Gold Carbenes

During the past two decades, gold-catalyzed nitrene-transfer reactions via α-imino gold carbenes have received extensive attention as this strategy provides rapid access to N-containing molecules with high efficiency. In this review, we will focus on the recent progress in the gold-catalyzed formal annulations of ynamides with isoxazole derivatives as nitrene-transfer reagents via α-imino gold carbenes in atom-economic and rapid construction of N-heterocycles.

Synthesis of New Class of Functionalized Flavones/Isoxazole Derivatives-Nitrile oxide 1,3-Dipolar Cycloaddition

A new series of functionalized flavone-isoxazole derivatives have been synthesized from alkyne tethered 3-hydroxy flavone by adopting facile synthetic method, intermolecular nitrile oxide 1,3-dipolar cycloaddition in the presence of eco-friendly sodium hypochloride oxidant under mild reaction conditions. Structures of all the synthesized compounds were established on the basis of 1H NMR, 13C NMR and ESI-mass.