To a solution of (3S)-1-[(3-Bromophenyl)methyl]-3-methylpiperazine (250 mg, 0.5 mmol), TEA (0.5 ml, 3.5 mmol), and DMAP (12 mg, 0.1 mmol) in 1 mL of dry DMSO was added dropwise benzyl chloroformate (0.34 mL, 2.25 mmol) at 10° C. while stirring. The mixture was then heated and stirred at 50° C. for 1.5 h. After cooling to room temperature, 15 mL of ethyl acetate and 5 mL of saturated NaHCO3 were added. The organic layer was separated, concentrated under vacuum and purified by Gilson reverse phase HPLC, eluting with acetonitrile/water/0.1% TFA (10/90 to 70/30, v/v, over 12 min), to give the title compound (180 mg, 70%). LC/MS: m/z, 403 (M+H), 1.74 min.
