合成路线1

The methylation of 2,6-difluorophenol (I) with methyl iodide and K2CO3 in DMF gives 2,6-difluoroanisole (II), which by treatment with butyllithium and CO2 yields 2,4-difluoro-3-methoxybenzoic acid (III). The methylation of (III) with diazomethane in ether affords the methyl ester (IV), which by reaction with BBr3 in dichloromethane results in 2,4-difluoro-3-hydroxybenzoic acid methyl ester (V). The alkylation of (V) with chlorodifluoromethane and K2CO3 in DMF gives 3-(difluoromethoxy)-2,4-difluorobenzoic acid methyl ester (VI), which is treated with sodium azide in DMSO, yielding the azido derivative (VII). The reduction of (VII) with H2 over Pd/C in ethanol affords 3-amino-2,4-difluorobenzoic acid methyl ester (VIII), which is hydrolyzed with NaOH in ethanol, giving the free acid (IX). The reaction of (IX) with NaNO2 and HBr yields 4-bromo-3-(difluoromethoxy)-2-fluorobenzoic acid (X), which is condensed with the magnesium salt of malonic acid monoethyl ester (XI) by means of CDI in THF, affording the 3-oxopropionate (XII). The reaction of (XII) with dimethylformamide dimethylacetal (XIII) and cyclopropylamine (XIV) by means of acetic anhydride in dichloromethane gives the 3-(cyclopropylamino)acrylate (XV), which is cyclized by means of K2CO3 in hot DMSO, yielding quinolone (XVI). The condensation of (XVI) with the isoindolylboronic acid derivative (XVII) - obtained by reaction of 5-bromo-1(R)-methyl-2-tritylisoindoline (XIX) with triisopropyl borate and butyllithium in THF - by means of bis(triphenylphosphine)palladium(II) chloride as catalyst in refluxing toluene affords the protected compound (XVIII), which is finally deprotected with HCl in ethanol.