To a solution of 1-boc-piperidin-4-ylpropionic acid (1.20 g, 4.7 mmol, Astatech) in DMF (10 mL), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (1.16 g, 6.1 mmol) and 1-hydroxy-7-azabenzotriazole (0.83 g, 6.1 mmol) were added and the solution was stirred at room temperature for 30 min. To the resultant solution, a solution of 1-(4-fluorobenzyl)piperazin-2-one (1.07 g, 5.1 mmol, see Example 31, Steps 5-8) in DMF (2 mL) was added and the mixture was stirred for two hours. The product mixture was concentrated under vacuum, and the residue partitioned between water and ethyl acetate. The combined organic extracts were washed with brine, dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure. The residue was purified by flash column chromatography (ISCO column, 120 g silica gel) eluting with a 0-6% MeOH/CHCl3 gradient over 40 min. Collection and concentration of appropriate fractions provided the coupled product as a white solid.
