Green Synthesis of Isoxazole Derivatives by a One-Pot Multicomponent Reaction and Their Antiviral Activity Evaluation

A series of 4-substituted isoxazole derivatives were synthesized by a one-pot multicomponent reaction between aromatic aldehydes, ethyl acetoacetate, and hydroxylamine hydrochloride, with sulfonated rice straw ash (RSA-SO3H) used as an acid catalyst. The synthesized compounds were characterized using IR and 1H and 13C NMR spectroscopy and mass spectrometry. The antiviral activities of these derivatives were evaluated in vivo on Kufri Jyoti potato plants against the mechanically transmitted ssRNA Potato Virus Y (PVY), employing protective, simultaneous, and curative treatment approaches. Among the synthesized compounds, (4-(4-diethylamino)benzylidene)-3-methylisoxazol-5(4H)-one exhibited a significant antiviral activity, particularly in the protective treatment at a concentration of 250 µg/mL.