Studies of the Synthesis of Fused Isoxazoline/Isoquinolinones and Evaluation of the Antifungal Activity of Isoxazole-like Benzamide and Isoquinolinone Hybrids
2025
Konstantinos A. Ouzounthanasis | Jasmina Glamočlija | Ana Ćirić | Alexandros E. Koumbis
Isoxazole derivatives (isoxazoles, isoxazolines, and isoxazolidines) are present in the structure of several natural products and/or pharmaceutically interesting compounds. In this work, a synthetic study for the preparation of fused isoxazoline/isoquinolinone hybrids is presented. The initial approach involving the sequential 1,3-dipolar cycloaddition of nitrile oxides to indenone (to obtain the isoxazoline ring) and a Beckmann rearrangement (to construct the isoquinolinone lactam system) was complicated by the formation of fragmentation products during the latter. Therefore, the desired hybrids were successfully reached by applying DDQ-mediated oxidation of the respective isoxazolidines. Based on the results, key observations were made regarding the mechanism of the Beckmann reaction. Moreover, selected isoxazole benzamides and fused isoxazoline/isoxazolidine isoquinolinones were in vitro evaluated against a series of fungi strains (including a 2D checkerboard assay with ketoconazole), revealing that some of these compounds exhibit promising antifungal activity.
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