Sodium Hydroxide → 4-{(S)-1-[(S)-6-(2-Hydroxy-2-methyl-propyl)-2-oxo-6-phenyl-[1,3]oxazinan-3-yl]-ethyl}-benzoic acid

1 M aqueous NaOH solution (5 mL) was added to a solution of 4-{(S)-1-[(S)-6-(2-hydroxy-2-methyl-propyl)-2-oxo-6-phenyl-[1,3]oxazinan-3-yl]-ethyl}-benzoic acid methyl ester (0.73 g) in tetrahydrofuran (5 mL). The resulting solution was stirred at room temperature overnight. Then, the solution was concentrated and the residue was taken up in water and filtered. The aqueous filtrate was acidified with 1 M hydrochloric acid and the resulting mixture was extracted with ethyl acetate. The combined extracts were washed with brine and dried (MgSO4). The solvent was removed to afford the title compound as a foam-like solid.