Synthesis and Antibacterial Potency of 4-Methyl-2,7-dioxo-1,2,3,4,7,10- hexahydropyrido[2,3-ƒ]quinoxaline-8-carboxylic acid, Selected [a]-Fused Heterocyles and Acyclic Precursors

Abstract

The reaction of 7-chloro-1-cyclopropyl-6-fluoro-8-nitro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (7) with each of sarcosine and (±)-pipecolinic acid afforded the corresponding N-(4- oxoquinolin-7-yl)-α-amino acids 8 and 9. Reductive lactamization of the latter with sodium dithionite gave hexahydropyrido[2,3- f ]quinoxaline (10) and octahydrodipyrido[1,2-a : 2,3- f ]quinoxaline (11) derivatives, respectively. Compounds 8 - 11 and their homologs 1 - 6, accessible from (S)-proline, (2S, 4R)-4-hydroxyproline and (S)-tetrahydroisoquinoline-3-carboxylic acid exhibit good to excellent antibacterial activities against E. coli and S. aureus.