General procedure for the synthesis of α-amino-gamma-butyrolactone hydrobromide from L-methionine: Bromoacetic acid (46.0 kg), 2-propanol (69.0 kg), and acetic acid (69.0 kg) were sequentially added to an aqueous solution (69 kg) of L-methionine (46 kg) at ambient temperature. The resulting mixture was heated to reflux (85 °C to 95 °C) and stirred continuously at this temperature until the completion of the reaction was confirmed by 1H NMR. After completion of the reaction, the mixture was concentrated under reduced pressure and co-evaporated with 2-propanol. To the concentrated mixture was added 2-propanol (161.0 kg) followed by the slow addition of a 10 wt% HCl/dioxane solution (102 kg) at ambient temperature. The resulting slurry was heated to about 60°C and stirred for about 4 hours. Subsequently, the mixture was cooled to about 22°C and stirring was continued for about 2 hours. Filtration gave the product α-amino-γ-butyrolactone hydrobromide (Ma), which was was washed with two portions of 2-propanol (28 kg each) and dried under vacuum at 40 °C to give a white to off-white solid (39.3 kg, 70% yield).The 1H NMR (D2O) data were as follows: δ 4.79 (s, 2H), 4.61 (dd, 1H), 4.49-4.41 (m. 2H), 2.80 (m, 1H), 2.42 (m, 1H).
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