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氟哌酸(Norfloxacin,8)为吡酮酸类抗菌药物的优秀代表之一,由7-氯-1-乙基-6-氟-1,4-二氢-4-氧喹啉-3-羧酸同无水哌嗪缩合而得,由于氯、氟对亲核取代相竞争,在一般条件下有25％左右的氟被哌嗪取代了的副产物生成(J Med Chem 1980,23:1358)。基于芳香硝基对亲核试剂的敏感性高于氯(化学通报 1983,(5):38),我们设想把7-位氯改为硝基,即用1-乙基-1,4-二氢-7-硝基-4-氧-6-氟喹啉-3-羧酸乙酯(1)与无水哌嗪反应、有可能减少
Norfloxacin (8) is one of the best representatives of the pyrazolonic acid antibacterials and is composed of 7-chloro-1-ethyl-6-fluoro-1,4-dihydro-4-oxoquinoline-3- Condensation of a carboxylic acid with an anhydrous piperazine results from the competition of fluorine and fluorine for nucleophilic substitutions and under normal conditions about 25% of the fluorine is generated as a by-product of piperazine substitution (J Med Chem 1980, 23: 1358 ). Based on the sensitivity of aromatic nitrogens to nucleophiles to be higher than that of chlorines (Chem. 1983, (5): 38), we envisaged changing the 7-position chloride to a nitro group with 1-ethyl- Hydrogen-7-nitro-4-oxo-6-fluoroquinoline-3-carboxylate (1) reacted with anhydrous piperazine,