A series of ethyl 2-(2-(arylidene)hydrazinyl)thiazole-4-carboxylates (2a–r) was synthesized in two steps from thiosemicarbazones (1a–r), which were cyclized with ethyl bromopyruvate to ethyl 2-(2-(arylidene)hydrazinyl)thiazole-4-carboxylates (2a–r). The structures of compounds (2a–r) were established by FT-IR, 1H- and 13C-NMR. The structure of compound 2a was confirmed by HRMS. The compounds (2a–r) were then evaluated for their antimicrobial and antioxidant assays. The antioxidant studies revealed, ethyl 2-(2-(4-hydroxy-3-methoxybenzylidene)hydrazinyl)thiazole-4-carboxylate (2g) and ethyl 2-(2-(1-phenylethylidene)hydrazinyl)thiazole-4-carboxylate (2h) as promising antioxidant agents with %FRSA: 84.46 ± 0.13 and 74.50 ± 0.37, TAC: 269.08 ± 0.92 and 269.11 ± 0.61 and TRP: 272.34 ± 0.87 and 231.11 ± 0.67 μg AAE/mg dry weight of compound. Beside bioactivities, density functional theory (DFT) methods were used to study the electronic structure and properties of synthesized compounds (2a–m). The potential of synthesized compounds for possible antiviral targets is also predicted through molecular docking methods. The compounds 2e and 2h showed good binding affinities and inhibition constants to be considered as therapeutic target for Mpro protein of SARS-CoV-2 (COVID-19). The present in-depth analysis of synthesized compounds will put them under the spot light for practical applications as antioxidants and the modification in structural motif may open the way for COVID-19 drug.

Trypanosomatids are protozoan parasites responsible for leishmaniasis, Chagas disease and sleeping sickness. The design of new antitrypanosomatid drugs with trypanosomicidal and leishmanicidal activities is an effective perspective. The thiazolidinone ring is an important scaffold for several biological disorders. Herein, 4‐oxothiazolidine‐5‐acetic acids (1 a‐1 w) have been synthesized from respective thiosemicarbazone and maleic anhydride. Some of these 4‐oxothiazolidine‐5‐acetic acids were toxic for trypomastigotes without affecting macrophages viability. From this series, compounds 1 e (IC50=10 μM), 1 u (IC50=8.94 μM), 1 g (IC50=5.65 μM) and 1 w (14.06 μM) showed the best anti‐T. cruzi activity for trypomastigote form, while 1 e, 1 u and 1 g showed SI higher than benznidazole (BZD). Similarly, against epimastigote the compound 1 q (IC50epi= 4.70 μM) has been found more selective and most active than benznidazole. However, evaluation against T. cruzi revealed that most of the active compounds have a low inhibition profile and weak leishmanicidal activity. In silico data suggests a good drug‐likeness profile, high chemical stability and demonstrate the use of these compounds in the designing of new anti‐T. cruzi and anti‐Leishmanial drugs.

Chagas and leishmaniasis are both neglected tropical diseases, whose inefficient therapies have made them remain the cause for millions of deaths worldwide.