合成路线1

Treatment of 3,4-difluoroaniline (I) with CS2 and Et3N gives triethylammonium dithiocarbamate (II), which reacts with ethyl chloroformate in chloroform to yield (III). Isothiocyanate (III) is converted into the potassium salt (IV) by reaction with diethyl malonate and KOH in dioxane and then transformed into methoxymethyl thioether (VI) by means of reagent (V) and Et3N in toluene. Cyclization of (VI) by heating in diphenyl ether affords quinoline (VII), which then reacts with benzoyl chloride (VIII) in pyridine to furnish (IX). Benzoyloxy derivative (IX) is converted into (X) by means of HCl in EtOH, and its reaction with 1-bromo-2-fluoroethane (XI) and NaHCO3 yields compound (XII). Chlorination of (XII) with SO2Cl2 in hexane provides (XIII), which by simultaneous hydrolysis and intramolecular cyclization by means of Et3N /H2O in THF provides the mixture of isomers (XIV). (+)-(XV) is obtained by HPLC chromatography of (XIV) on a chiral stationary phase. Treatment of (+)-(XV) with 1-methylpiperazine (XVI) in DMF provides ethyl ester (+)-(XVII), which is finally hydrolyzed by means of H2SO4 in H2O.