Synthesis, Characterization, and Antimicrobial Activity of New 1,2,3-Thiadiazole and 1,2,3-Selenadiazole Derivatives

Abstract

1,2,3-Thiadiazole, 1,2,3-selenadiazole, and semicarbazones that are prepared from ketones are promising moieties for lead compound development. New 1,2,3-thiadiazole (2c-4c) and 1,2,3-selenadiazole derivatives (2d–4d) were prepared from the corresponding semicarbazones (2b-4b). The semicarbazones (2b-4b) were prepared from the corresponding ketones (2a-4a). Characterization of the synthesized compounds was performed using infrared spectra (IR), proton nuclear magnetic resonance (1H-NMR) spectra, carbon nuclear magnetic resonance (13C-NMR), ultraviolet spectra, mass spectrometry, and elemental analysis. The antimicrobial activity of the prepared compounds was explored in vitro against various pathogenic microbes. All heterocyclic compounds had positive antimicrobial activity, but these activities varied in the extent of antimicrobial coverage. Compounds (2c) and (2d) had positive activity against Staphylococcus aureus and Escherichia coli but without any antipseudomonal activity. Compound (3c) had the most activity against Candida albicans with potential as a novel antifungal agent along with activity against some Gram-positive and Gram-negative bacteria. Compounds (4c) and (4d) exhibited broad-spectrum coverage in which both compounds demonstrated antimicrobial activity against all microorganisms explored. Interestingly, they both had substantial antipseudomonal activity against local resistant Pseudomonas aeruginosa and reference P. aeruginosa (ATCC 27853). This may suggest the potential for compounds (4c) and (4d) as novel broad-spectrum antibacterial agents with promising antipseudomonal activity. In conclusion, new 1,2,3-thiadiazole (2c-4c) and 1,2,3-selenadiazole (2d-4d) derivatives were identified as potential lead compounds for novel antibacterial agents.