Studies on antibacterial agents. II. Synthesis and antibacterial activities of substituted 1,2-dihydro-6-oxo-6H-pyrrolo[3,2,1-ij]quinoline-5-carboxylic acids.

A series of substituted 1, 2-dihydro-6-oxo-pyrrolo[3, 2, 1-ij]quinoline-5-carboxylic acids for the treatment of systemic infections was synthesized via 7-bromo-3-ethylthio-4, 5-difluoro-2-methylindole (3), which was prepared by Gassman's indole synthesis in excellent yield. The synthesized pyrroloquinolines were tested for their antibacterial activities. 8-Fluoro-1, 2-dihydro-2-methyl-9-(4-methyl-1-piperazinyl)-6-oxo-6H-pyrrolo[3, 2, 1-ij]quinoline-5-carboxylic acid showed a potent antibacterial activity against gram-positive and gram-negative bacteria.