Trifluoroacetic acid (5.0 mL) was added to a stirred solution of [(1S)-2-(3,5-dichloro-1-oxido-pyridin-1-ium-4-yl)-1-(3,4-dimethoxyphenyl)ethyl] 3-[(2-tert-butoxy-2-oxo-1-phenyl-ethyl)sulfamoyl]benzoate (1.0 g, 1.39 mmol) in dichloromethane (5.0 mL) at 0° C., and stirring was maintained at 0° C. for 2.5 hours. The reaction mixture was then stirred at ambient temperature for 30 minutes, after which time toluene (50 mL) was added and the solvent removed under reduced pressure to yield a yellow solid, inferred as the intermediate 2-[[3-[(1S)-2-(3,5-dichloro-1-oxido-pyridin-1-ium-4-yl)-1-(3,4-dimethoxyphenyl)ethoxy]carbonylphenyl]sulfonylamino]-2-phenyl-acetic acid. The crude was subsequently dissolved in THF (20 mL), and N,N′-dicyclohexylcarbodiimide (431 mg, 2.09 mmol), 1-hydroxybenzotriazole hydrate (282 mg, 2.09 mmol) and (R)-quinuclidin-3-ol (355 mg, 2.79 mmol) were sequentially added. The resulting reaction mixture was stirred at ambient temperature for 18 hours, after which time the reaction mixture was filtered through a pad of Celite®, washing with tetrahydrofuran (10 mL). The filtrate was concentrated under reduced pressure and the resulting crude was partitioned between ethyl acetate (20 mL) and water (10 mL), the organic phases were dried over magnesium sulfate and concentrated under reduced pressure. The resulting crude was triturated in diethyl ether, and final purification was achieved by preparative HPLC and subsequent SFC to afford the title compound as a pale yellow solid (17.9 mg, de=100%).
