A series of novel 1-alkoxy-1,4-dihydro-4-oxo-3-quinolinecarboxylic acids was synthesized and screened as antimicrobial agents. The most active compounds in vitro against gram-negative microorganisms and Staphylococcus aureus were 1,4-dihydro-1-methoxy-6,7-methylenedioxy-4-oxo-3-quinolinecarboxylic acid (22), 1,2,6,9-tetrahydro-6-methoxy-9-oxofuro[3,2-f]quinoline-8-carboxylic acid (30, and 2,3,6,9-tetrahydro-6-methoxy-3-methyl -2,9-dioxothiazolo [5,4-f]quinoline-8-carboxylic acid (34). These compounds had antigram-negative activity comparable to that of the corresponding N-ethyl derivatives 1, 2, and 4. Their serum levels and urinary recovery rates in rats, however, were significantly improved relative to the latter compounds (1,2, and 4).

Aus den substituierten und kondensierten 4‐Chlor‐chinolin‐3‐carbonsäure‐ estern (I) entstehen mit m‐Chlorperbenzoesäure die N‐Oxide (II), die zu den N‐Hydroxy‐chinolonen (III) und ihren Substitutionsprodukten (IV) führen.