Synthesis and antibacterial properties of new N₄-acetylated hexahydro-2,7-dioxopyrido[2,3-f]quinoxaline-8-carboxylic acids

Abstract

Direct interaction between 7-chloro-1-cyclopropyl-6-fluoro-8-nitro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid and primary α-amino acids (exemplified by glycine, alanine, and l-valine) in aqueous ethanolic NaHCO₃ at 70–80°C for 24–72 h produced the respective N-(4-oxoquinolin-7-yl)-α-amino acids (6a–c). The latter derivatives underwent reductive lactamization upon treatment with Na₂S₂O₄ in aqueous ethanol to afford moderate yields of the corresponding pyrido[2,3-f]quinoxaline-8-carboxylic acids (8a–c). Acetylation of 8a–c using acetyl chloride afforded N₄-acetylated hexahydro-2,7-dioxopyrido[2,3-f]quinoxaline-8-carboxylic acids (9a–c). The structures, assigned to these new heterocyclic products, are supported by analytical and spectral data. The synthesized compounds (6a–c/9a–c) showed appreciable antibacterial activity as compared with ciprofloxacin.

Keywords::

• Synthesis
• hexahydro-2,7-dioxopyrido[2,3-f]quinoxaline-8-carboxylic acids
• antibacterial activity
• reductive lactamization

Acknowledgment

Deanship of Academic Research and Dean, Faculty of Pharmacy, University of Jordan, Amman, Jordan for providing Scifinder and e-library facilities.

Declaration of interest

The authors wish to thank Hamdi Mango Center for Scientific Research-University of Jordan, Amman, for financial support.