Benzothiazole Clubbed Imidazolone Derivatives: Synthesis, Molecular Docking, DFT Studies, and Antimicrobial Studies.

Aim: This study aims to synthesize antimicrobial agents and their molecular docking, and DFT studies of benzothiazole-imidazolone scaffolds.

Background: Benzothiazole and imidazolone analogues are of interest due to their potential activity against microbial infections. In search of suitable antimicrobial compounds, we report here the synthesis, characterization, and biological activities of benzothiazole and imidazolone analogues (4a-l).

Objective: The benzothiazole clubbed imidazolone motifs were synthesized, characterized, and screened for their antimicrobial activity. Molecular docking was carried out for the development of antimicrobial agents based on the results of biological activity obtained.

Methods: We have synthesized a new series of benzothiazole-clubbed imidazolone hybrids by using multi-step reactions in the search for antimicrobial agents (4a-l). The structures were determined by ¹H NMR, ¹³C NMR, IR, and mass spectroscopy techniques. Moreover, synthesized compounds were evaluated for their antimicrobial activity by using a Serial Broth Dilution method. In addition, molecular electrostatic potential, geometric optimization, and molecular reactivity analyses (HOMO-LUMO) of 4c, which is one of the compounds with the highest antibacterial activity, were performed.

Results: The in vitro antimicrobial activity was evaluated against pathogenic strains. Among them, compounds 4c showed the most potent biological activity against Gram-negative bacteria, E. coli with MIC values of 50 μg/mL, and compound 4c active against A. clavatus with MIC values of 100 μg/mL. Active compound 4c HUMO-LUMO energies, molecular electrostatic potential analysis, and geometric optimization parameters were calculated with a 6-31G ** base set using DFT/B3LYP theory, and the results were displayed. Molecular docking studies were performed on E. coli DNA Gyrase B to understand the binding interaction of compound 4c, and it was observed that compound 4c interacted with Arg76 amino acid of the active site through hydrophobic interaction.

Conclusion: Benzothiazole-clubbed imidazolone hybrids (4a-l) indicated promising antimicrobial activity. Among them, compounds 4b (MIC=50 μg/mL C. albicans), 4c (MIC=50 μg/mL, E. coli), 4e (MIC= 100 μg/mL, A. niger), and 4g (MIC= 50 μg/mL, S. pyogenes) with electronwithdrawing bromo, chloro, and fluoro group at the para position of the phenyl ring on benzothiazole-imidazolone hybrids indicated remarkable potency compared to the standard drug. The geometric optimization, molecular reactivity, and MESP analyses of 4c were calculated with the B3LYP/6-31G ** base set and ΔE = ELUMO-EHOMO, which was found to be - 0.12096 eV. In addition, the binding affinity scores correlated well with the in vitro antimicrobial activity (4c), while their binding modes proposed the involvement of steric, electrostatic, and hydrogen- bonding interactions with the active site.