To a stirred solution of malonic acid monoethyl ester (1.2 g, 0.0089 mole) in DMF (10 mL) was added DIPEA (2.5 g, 0.02 mole), HOBt (1.3 g, 0.0097 mole) and EDCI.HCl (1.9 g, 0.0097 mole). After 2 minutes 4-(2-chloro-phenoxy)-piperidine hydrochloride (2 g, 0.0081 mole) was added 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. The resulting residue was purified by column chromatography using silica gel 60-120 mesh (60% ethyl acetate in hexane) to afford 1.1 g (42%) of 3-[4-(2-chloro-phenoxy)-piperidin-1-yl]-3-oxo-propionic acid ethyl ester. LC-MS purity: 326.11 (M+1)+, 90.2%. To a stirred solution of 3-[4-(2-chloro-phenoxy)-piperidin-1-yl]-3-oxo-propionic acid ethyl ester (1.1 g, 0.0034 mole) in a mixture of THF (20 mL), methanol (4 mL) and H2O (4 mL) was added LiOH.H2O (0.286 g, 0.0068 mole) at ambient temperature. 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 resulting precipitate was isolated by filtration and dried to afford 0.75 g (75%) of 3-[4-(2-chloro-phenoxy)-piperidin-1-yl]-3-oxo-propionic acid.
