Abstract
An efficient synthesis of a series of 4-((2H-chromen-3-yl)/(2-phenyl-2H-chromen-3-yl)methylene)-3-methylisoxazol-5(4H)-ones has been developed via one-pot multicomponent addition of ethyl acetoacetate, hydroxylamine hydrochloride and 2H-chromene-3-carbaldehydes using DABCO as organocatalyst in refluxing ethanol. The reaction acted as a cyclocondensation between ethyl acetoacetate, hydroxylamine hydrochloride and 2H-chromenealdehyde, resulting into chromenyl isoxazolone. This mild cost-effective hetero-cyclization was obtained by simple crystallization with comparatively high yields and purity with good substrate scope adequacy. All the synthesized compounds were subsequently evaluated for in vitro anti-bacterial assay against Gram-negative (Escherichia coli and Klebsiella pneumoniae) and Gram-positive (Staphylococcus aureus and Streptococcus pyogenes) pathogenic bacteria in comparison to the standard antibiotic Gentamicin. Compounds 21f and 21h found to have potent inhibitory activity against E. coli having ZI at 18 mm and 19 mm each corresponding to a MIC of 6.25 (μg/ml), respectively. SAR and molecular docking revealed compounds 21f and 21h having –Cl and –Br group displayed improved halogen and hydrogen bond-interaction with bacterial DNA gyrase of E. coli (PDBID:1KZN) having binding affinity of −8.8 kcal/mol respectively.
Published Version
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