To a solution of (5-chloro-2-{2-[4-(4-fluoro-benzyl)-(2R,5S)-2,5-dimethyl-piperazin-1-yl]-2-oxo-ethoxy}-phenoxy)-acetic acid (0.051 g, 0.10 mmol) in methylene chloride (1 mL) was added 4-dimethylaminopyridine (0.022 g, 0.18 mmol), (3-(dimethylamino)propyl)ethyl carbodiimide hydrochloride (0.033 g, 0.17 mmol), methanesulfonamide (0.016 g, 0.17 mmol) and triethylamine (0.040 mL, 0.29 mmol). The reaction was stirred at ambient temperature for 3 days. The reaction mixture was then diluted with dichloromethane and washed with 10% aqueous acetic acid. The organic layer was washed with saturated aqueous sodium hydrogen carbonate, dried over magnesium sulfate and concentrated in vacuo. Chromatography on silica gel followed by trituration with methylene chloride/hydrogen chloride in diethyl ether gave the title compound as the hydrochloride salt (0.015 g, LRMS: 542.1, 544.1).
