Background: A series of novel 2-methoxy-N-phenyl-6-(5-phenyl-1,3,4-oxadiazol-2- yl)pyridin-3-amine (6a-i) have been synthesized from bromo methoxy picolinicacid as starting material. Finally, oxadiazole was coupled with various anilines using buchwald coupling reactions to give the target compounds. The newly synthesized compounds were evaluated for their efficacy as antimicrobial agents against various Gram-positive and Gram-negative strains of bacteria and fungal strains. Compounds 6h and 6i possessing trifluoromethyl groups at second and fourth positions of the aniline ring exhibited selective inhibition against S. aureus. Amongst these compounds 6c was found to be the most potent against Bacillus subtilis and Candida albicans. Moreover, other compounds also found to be potential antibacterial agents in comparison to the standard drugs.
Methods: On the basis of the above findings and in continuation of our search on 1,3,4-Oxadiazole derivatives with potential biological activity, we have synthesized new molecules based on 1,3,4-Oxadiazole ring system by incorporating methoxy pyridine moiety.
Results: The synthetic route for the synthesis of title compounds were started with using commercially available acid. In the first place Esterification of starting meterial followed by treating with hydrazine hydrate afforded the compound, which upon reaction with benzoylchloride in the presence of POCl3 furnished oxadiazloe derivatives. Finally, the key intermediates 1,3,4-oxadiazole were coupled with various anilines using buchwald reaction gave the final compounds. The chemical structures of all the newly synthesized compounds were confirmed by their 1H NMR, 13C NMR, mass spectral data and elemental analysis. Further these compounds have been screened for their antibacterial, antifungal and nematicidal activities.
Conclusion: Synthesis and screening of antibacterial and antifungal activities for a novel series of 1,3,4-Oxadiazole conjugates have been investigated. All the compounds have shown mild to potent inhibitory activity against B. subtilis and exhibited mild to moderate antibacterial activities against the other tested organisms. Compounds 6c and 6e were found to be the most active against most of the tested organisms. Some of the compounds have shown significant antibacterial activity in comparison to the controls.
Keywords: 1, 3, 4-Oxadiazole, antibacterialactivity, antifungalactivity, nematicidal activity.