Design, Synthesis, and Anti-Bacterial Evaluation of Tetrahydrobenzothiophene Derivatives as Lipopolysaccharide Biogenesis Inhibitors

Background: Bacterial infections caused by multidrug-resistant bacteria have emerged as major threats to human communities worldwide. There is a great need to develop new mechanisms by which anti-bacterial agents can combat bacterial antibiotic resistance. Objective: This study aims to synthesize and characterize a series of novel tetrahydrobenzothiophene derivatives and evaluate their anti-bacterial activities. Methods: In this study, we have synthesized 2-benzamido-4,5,6,7-tetrahydrobenzo[b]thiophene-3- carboxylic acid derivatives (3a-3r) and investigated their anti-bacterial activities against E. coli, P. aeruginosa, Salmonella, and S. aureus. Results: The MIC values demonstrated that all synthesized derivatives possessed potent anti-bacterial activity properties. Compounds 3b, 3e, 3f, 3g, 3h, 3n, and 3q exhibited in vitro excellent anti-bacterial efficiency. Compounds 3b, 3e, 3f, and 3p were evaluated by in vitro time-kill assay; they displayed concentration- dependent bacteriostatic effects. Compounds 3b, 3e, 3f, and 3p showed moderate water solubility, high stability in plasma, and moderate acute oral toxicity. Conclusion: Most of the 2-benzamido-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylic acid derivatives exhibited potent anti-bacterial activities. The data reported in this paper may guide the design of tetrahydrobenzothiophene derivatives.