Synthesis and structural elucidation of novel quaternary pyridinium salt and indolizine derivatives as an anti-tubercular agent: In Silico and In Vitro screening

The in vitro anti-mycobacterial activity of a novel series of diversely substituted quaternary pyridinium salts (3a-m) and indolizines (5a-h) were assessed against H37Rv strain of Mycobacterium tuberculosis (M.tb). The series of intermediate 1-(2-oxo-2-phenylethyl)-4-(piperidin-1-yl)pyridin-1-ium bromide, which contains a heterocyclic ring molecule, has been prepared by reacting with 4-(piperidin-1-yl)pyridine and phenacyl bromide at room temperature. The final ethyl 3-benzoyl-7-(piperidin-1-yl)indolizine-1-carboxylate analogues were prepared by using pyridin-1-ium bromide with electron-deficient acetylene, undergoing 1, 3-dipolar cycloaddition at the ambient temperature using anhydrous potassium carbonate and N, N-dimethylformamide as a solvent. All the newly synthesized compounds were characterized by spectroscopic techniques such as ¹H and ¹³C NMR, and HRMS. All the synthesized intermediates and final compounds were evaluated for their anti-tubercular activities against H37Rv (ATCC 27294) strain. All the compounds exhibited anti-tubercular activities in the range of 12.5–50 µM. In vitro screening of all derivatives concluded that among all the screened candidates 3k emerged as an active hit with MIC 12.5 µM, 3l and 3m with MIC 25 µM.