A solution of triphenylphosphine (288 mg, 1.1 mmol) in methylene chloride (6 mL) was cooled to 0° C. and then treated with N-bromosuccinimide (196 mg, 1.1 mmol). The reaction mixture was stirred at 0° C. for 30 min and then treated with 3-cyclopentyl-2-[3-fluoro-4-(5-methyl-tetrazol-1-yl)-phenyl]-propionic acid (prepared in Example 1, 175 mg, 0.55 mmol). The clear solution was stirred for 15 min at 0° C. and then allowed to warm to 25° C. where it was stirred for 1.5 h. The reaction mixture was then treated with 2-amino-5-bromopyridine (476 mg, 2.75 mmol), and the resulting suspension was stirred for 2 d at 25° C. The reaction mixture was then concentrated in vacuo to remove methylene chloride, and the residue was diluted with ethyl acetate (50 mL) and water (50 mL). The two layers were separated, and the aqueous layer was extracted with ethyl acetate (1×25 mL). The combined organic extracts were successively washed with a saturated aqueous sodium bicarbonate solution (1×50 mL) and a saturated aqueous sodium chloride solution (1×50 mL), dried over anhydrous magnesium sulfate, filtered, and concentrated in vacuo. Biotage chromatography (FLASH 40S, Silica, 2/1 hexanes/ethyl acetate) afforded N-(5-bromo-pyridin-2-yl)-3-cyclopentyl-2-[3-fluoro-4-(5-methyl-tetrazol-1-yl)-phenyl]-propionamide (190 mg, 73%) as a white solid: mp 73-78° C.; EI-HRMS m/e calcd for C21H22BrFN6O (M+) 472.1022, found 472.1022.
