(R)-2-((tert-Butoxycarbonyl)amino)-2-phenylacetic acid (5.0 g, 19.9 mmol), (R)-quinuclidin-3-ol (3.8 g, 29.8 mmol), N,N′-Dicyclohexylcarbodiimide (4.72 g, 22.9 mmol) and 1-hydroxybenzotriazole hydrate (3.09 g, 22.9 mmol) where mixed together in tetrahydrofuran (175 mL) and stirred at ambient temperature for 18 hours. After this time the reaction mixture was filtered through a pad of Celite® and concentrated in vacuo. The resulting crude was partitioned between ethyl acetate (100 mL) and 10% aqueous sodium carbonate solution (50 mL), the resulting organic fractions were dried over magnesium sulfate, filtered and the solvent was removed in vacuo. Trituration with cold methanol gave the title compound as a white solid (898 mg, 17%) as a single diastereoisomer.
