New thiophene-derived α-aminophosphonic acids: Synthesis under microwave irradiations, antioxidant and antifungal activities, DFT investigations and SARS-CoV-2 main protease inhibition

Four new α-aminophosphonic acids containing thiophene ring have been synthesized using simple, neat and catalyst-free conditions, more convenient and eco-friendly method under microwave irradiations. The structures of the title molecules have been confirmed by UV-Vis, FT-IR, (1)H NMR, (13)C NMR and (31)P NMR. Moreover, their antioxidant activity was evaluated using DPPH, ABTS and phenantroline methods; the obtained results indicate that the title molecules exhibit excellent activity better than standards BHT and BHA. Also, the synthesized compounds show a good antifungal activity against two fungi, Fusarium oxysporum and Alternaria alternata. In addition, molecular, electronic properties, stability and reactivity of the synthesized products were studied by the density functional theory (DFT). Furthermore, molecular docking investigations of the studied α-aminophosphonic acids showed a good inhibition of SARS-CoV-2 main protease (Mpro).