A solution of triphenylphosphine (279 mg, 1.06 mmol) in methylene chloride (5 mL) was cooled to 0° C. and then slowly treated with N-bromosuccinimide (189 mg, 1.06 mmol). The reaction mixture was stirred at 0° C. for 20 min and then treated with 3-cyclopentyl-2-(4-ethanesulfonyl-phenyl)-propionic acid (300 mg, 0.97 mmol). The resulting reaction mixture was stirred at 0° C. for 10 min and then allowed to warm to 25° C. where it was stirred for 30 min. The reaction mixture was then treated with 2-aminothiazole (213 mg, 2.13 mmol). The resulting reaction mixture was stirred at 25° C. for 15 h. The crude reaction mixture was then directly purified by flash chromatography (Merck Silica gel 60, 230-400 mesh, 1/1 hexanes/ethyl acetate) to afford 3-cyclopentyl-2-(4-ethanesulfonyl-phenyl)-N-thiazol-2-yl-propionamide (330 mg, 87%) as a pale yellow solid: mp 178-179° C.; EI-HRMS m/e calcd for C19H24N2O3S2 (M+) 392.1228, found 392.1230.
