合成路线1

The reaction of 3-chlorotetrafluoropyridine (I) with sodium tert-butoxide in THF gives 4-tert-butoxy-3-chloro-2,5,6-trifluoropyridine (II), which is dechlorinated with H2 over Pd/C in methanol yielding 4-tert-butoxy-2,3,6-trifluoropyridine (III). The methylation of (III) with methyl iodide and lithium diethylamide (LDA) in THF affords 4-tert-butoxy-2,3,6-trifluoro-5-methylpyridine (IV), which is selectively defluorinated with hydrazine in refluxing propanol to give 4-tert-butoxy-2,5-difluoro-3-methylpyridine (V). The condensation of (V) with cyclopropylacetonitrile (VI) by means of LDA in THF yields 2-(4-tert-butoxy-5-fluoro-3-methyl-2-pyridyl)-2-cyclopropylacetonitrile (VII), which is treated first with trifluoroacetic acid and then with POCl3 to afford 2-(4-chloro-5-fluoro-3-methyl-2-pyridyl)-2-cyclopropylacetonitrile (VIII). The alcoholysis of (VIII) with ethanol/HCl gives the corresponding ethyl ester (IX), which is partially reduced with LiAlH4 in THF to afford the corresponding aldehyde (X). The condensation of (X) with diethyl malonate (XI) by means of piperidine in refluxing ethanol yields the ethylidenemalonate (XII), which, without isolation, is cyclized by heating at 235 C in Dowtherm to afford 8-chloro-1-cyclopropyl-7-fluoro-9-methyl-4-oxo-4H-quinolizine-3-carboxylic acid ethyl ester (XIII). The reaction of (XIII) with 3(S)-(tert-butoxycarbonylamino)pyrrolidine (XIV) by means of NaHCO3 in acetonitrile gives the corresponding condensation product (XV), which is hydrolyzed ith LiOH in THF/water to the corresponding free acid (XVI). Finally, this compound is deprotected with 4N HCl in dioxandichloromethane.