Antimicrobial Evaluation of New Quinoxaline Derivatives Synthesized by Selective Coupling with Alkyl Halides and Amino Acids Esters

• Published in: Journal of heterocyclic chemistry 2017-09, Vol.54 (5), p.2881-2888
• Main Authors: Boraei, Ahmed T. A., El Tamany, El Sayed H., Ali, Ibrahim A. I., Gebriel, Sara M.
• Format: Article
• Language: English
• Subjects: Acetylacetone; Aldehydes; Alkylation; Amines; Amino acids; Antiinfectives and antibacterials; Antimicrobial agents; Bacteria; Coupling (molecular); E coli; Esters; Fungi; Fusarium; Fusarium oxysporum; Halides; Heterocyclic compounds; Ketones; Mass spectrometry; NMR spectroscopy; Pyrazole; Synthesis
• ISSN: 0022-152X; 1943-5193
• DOI: 10.1002/jhet.2896

Alkylation of quinoxaline scaffold 1 in the presence of K2CO3 preferred N‐alkylation than O‐alkylation. Quinoxaline hydrazide 6 was successfully coupled with various amino acids, esters, and amines via azide‐coupling method. New heterocyclic compounds containing quinoxaline linked to 1,3,4‐oxadiazolethione or pyrazole were obtained from cyclization of 6 with CS2 and acetylacetone, respectively. A series of hydrazide Schiff's bases were formed from hydrazide 6 by condensation with a set of aldehydes and ketones. NMR spectroscopy and mass spectrometry were used for structure elucidation of new compounds. The antimicrobial activity of the synthesized compounds was investigated toward two wild‐type bacterial strains (Staphylococcus aureus and Escherichia coli) and two fungal species (Alternaria brassicicola and Fusarium oxysporum). Four compounds displayed a significant activity toward S. aureus. The ester 4 showed higher activity than the standard drugs, which make it a promising lead compound. ■