合成路线1

Reductive ring closure of diethyl 2-nitrobenzylidenemalonate (I) afforded quinolone (II). Subsequent N-alkylation of (II) with isopropyl iodide gave (III). Carboxylic acid (IV) was then obtained by basic hydrolysis of the ethyl ester (III). In a related procedure, reductive alkylation of 2-aminobenzyl alcohol (V) with acetone in the presence of NaBH4 gave the N-isopropyl derivative (VI). Oxidation of (VI) using activated MnO2 in toluene yielded aldehyde (VII). Further Knoevenagel condensation of (VII) with diethyl malonate in the presence of piperidine and AcOH produced the previously described quinolone ester (III). Alternatively, condensation of (VII) with malonic acid directly produced the previously described quinolonecarboxylic acid (IV). Acid chloride (VIII) was then prepared by treatment of (IV) with thionyl chloride in hot toluene.