Methanol → 2-(2-Oxo-1,3-oxazinan-3-yl)acetic acid

To a solution of 0.068 g (0.39 mmol) of methyl (2-oxo-1,3-oxazinan-3-yl)acetate from step B above in 6 mL of THF and 2 mL of water and 2 mL of methanol was added 0.60 mL (1.2 mmol) of an aqueous 2.0 M sodium hydroxide solution. The resulting mixture was stirred at ambient temperature for 3 h and then evaporated in vacuo to remove the methanol and THF. The aqueous phase was acidified with a 2 N hydrochloric acid solution until a pH of 2 was achieved and then extracted with a 30% isopropyl alcohol in chloroform mixture (3×10 mL). The combined organic layers were dried over anhydrous sodium sulfate, filtered and evaporated to yield the title compound as an off-white solid (0.06 g, 99%). 1H NMR (CD3OD, 500 MHz) δ: 4.32 (t, J=5.4 Hz, 2H), 4.03 (s, 2H), 3.41 (t, J=6.2 Hz, 2H), 2.10-2.05 (m, 2H). LC-MS: m/z (ES) 160 (MH)+.