A solution of phosgene(12.5% in toluene, 25 mL, 31.6 mmol) was added to a suspension of l-leucine (1.31 g, 10 mmol) in dioxane (30 mL) and ethyl acetate (25 mL) at 40 ℃ under a static atmosphere of nitrogen. After 4 h, the leucine had dissolved and then the excess phosgene was removed in a stream of nitrogen. The solvent was removed at 40 ℃ in vacuo and the residue was recrystallized from diethyl ether/light petroleum (bp 40–60 ℃) to yield colorless needles of 4-(2-methylpropyl)oxazolidine-2,5-dione (1.01 g, 69%).
