To a stirred solution of malonic acid monoethyl ester (0.5 g, 0.00377 mole) in DMF (10 mL) was added DIPEA (1.18 g, 0.0094 mole), HOBt (0.608 g, 0.0045 mole) and EDCI.HCl (0.865 g, 0.0045 mole). After 2 minutes 4-(2-chloro-5-fluoro-phenoxy)-piperidine hydrochloride (1 g, 0.003 7 mole) and the resulting mixture was stirred overnight. The reaction mixture was then diluted with cold water and the product was extracted with ethyl acetate. The organic layers were dried over sodium sulfate and concentrated under reduced pressure to get afford 0.9 g (70%) of 3-[4-(2-chloro-5-fluoro-phenoxy)-piperidin-1-yl]-3-oxo-propionic acid ethyl ester. LC-MS purity: 344.78 (M+1)+, 82.56%. To a stirred solution of 3-[4-(2-chloro-5-fluoro-phenoxy)-piperidin-1-yl]-3-oxo-propionic acid ethyl ester (0.9 g, 0.0026 mole) in a mixture of THF (10 mL), methanol (3 mL) and H2O (2 mL) was added LiOH.H2O (0.218 g, 0.0052 mole) at ambient temperature and the resulting mixture was stirred for 30 minutes. Volatiles were then evaporated and the resulting residue was diluted with water, acidified with 10% aqueous HCl solution. The product was extracted with ethyl acetate, and the organic layer was washed with brine solution, dried over sodium sulfate and concentrated under reduced pressure to afford 0.6 g (73%) of 3-[4-(2-chloro-5-fluoro-phenoxy)-piperidin-1-yl]-3-oxo-propionic acid. LC-MS purity: 316.72 (M+1)+, 75.8%.
