N-(4-(Phenylmethoxy)benzoyl)glycine pentafluorophenyl ester. N-(4-(Phenyl-methoxy)benzoyl)glycine methyl ester (14.75 g, 49.2 mmol) was boiled under reflux with methanolic sodium hydroxide (1M) (80 mL) for 2 h. The solvent was evaporated under reduced pressure. The residue was dissolved in water and was acidified by addition of aqueous hydrochloric acid. The suspension was extracted with ethyl acetate. The extract was washed with saturated brine and was dried with anhydrous magnesium sulphate. The solvent was evaporated under reduced pressure to give N-(4-(phenylmethoxy)benzoyl)glycine (6.59 g, 47%). Dicyclohexylcarbodiimide (720 mg, 3.5 mmol) was added to N-(4-(phenylmethoxy)benzoyl)glycine (100 g, 3.5 mmol) in dry tetrahydrofuran (100 mL) and the mixture was taken to 0° C. Pentafluorophenol (640 g, 3.5 mmol) was added dropwise and the mixture was stirred for 17 h at 0° C. The suspension was filtered and the solvent was evaporated from the filtrate under reduced pressure. The residue was dissolved in ethyl acetate (200 mL) and was washed with saturated aqueous sodium hydrogen carbonate (2×75 mL), with aqueous sulphuric acid (10%) and with water. The solution was dried with anhydrous magnesium sulphate and the solvent was evaporated under reduced pressure to give N-(4-(phenylmethoxy)benzoyl)glycine pentafluorophenyl ester (Intermediate B) (1.5 g, 95%).
