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

Figures & data

Scheme 1.  Synthesis of N₄-acetylated hexahydro-2,7-dioxopyrido[2,3-f]quinoxaline-8-carboxylic acids (9a-c).

Table  1.  In vitro antibacterial activity (minimum inhibitory concentration (MIC) values, μg/mL) of model compounds of the formulae 6a–c/9a–c as compared with the reference ciprofloxacin.

Compound number	LogP (cLogP)*	S. aureus ATCC 6538a MIC (μg/mL)	E. coli ATCC 8739 MIC (μg/mL)
6a	0.46 (1.57)	10.1	20.1
6b	0.95 (1.88)	9.5	19.5
6c	1.83 (2.81)	0.4	22.5
8a	–0.36 (0.79)	20.0	22.0
8b	0.13 (1.32)	5.8	11.5
8c	1.01 (2.24)	80.0	19
9a	–0.72 (0.65)	>100	>100
9b	–0.22 (1.17)	>100	>100
9c	0.66 (2.09)	>100	>100
3a	1.24 (1.76)	12.0	12.0
3b	0.42 (1.48)	10.5	0.7
Ciprofloxacin	—	1.23	0.31

*LogP (cLogP) were calculated using CambridgeSoft Chem Draw Ultra Version 8.0.

Scheme 2.  Fluoroquinolones (10, 11) with glycine substituent.