A solution of triphenylphosphine (409 mg, 1.56 mmol) in methylene chloride (8 mL) was cooled to 0° C. and then treated with N-bromosuccinimide (277 mg, 1.56 mmol). The reaction mixture was stirred at 0° C. for 30 min and then treated with a solution of 2-[3-chloro-4-(5-trifluoromethyl-tetrazol-1-yl)-phenyl]-3-cyclohexyl-propionic acid (370 mg, 0.92 mmol) in methylene chloride (5 mL). The clear solution was stirred for 15 min at 0° C. and then allowed to warm to 25° C. where it was stirred for 2 h. The reaction mixture was then treated with 2-aminothiazole (276 mg, 2.76 mmol), and the resulting suspension was stirred for 15 h at 25° C. The reaction mixture was concentrated in vacuo to remove methylene chloride, and the residue was diluted with ethyl acetate (100 mL) and a 1N aqueous hydrochloric acid solution (50 mL). The two layers were separated, and the aqueous layer was extracted with ethyl acetate (1×50 mL). The combined organic extracts were successively washed with a saturated aqueous sodium bicarbonate solution (1×100 mL) and a saturated aqueous sodium chloride solution (1×100 mL), dried over anhydrous magnesium sulfate, filtered, and concentrated in vacuo. Biotage chromatography (FLASH 40S, Silica, 3/2 hexanes/ethyl acetate) afforded 2-[3-chloro-4-(5-trifluoromethyl-tetrazol-1-yl)-phenyl]-3-cyclohexyl-N-thiazol-2-yl-propionamide (83 mg, 18%) as an amorphous solid: EI-HRMS m/e calcd for C20H20ClF3N6OS (M+) 484.1060, found 484.1068.
