Methyl 1-benzyl-5-oxo-3-pyrrolidinecarboxylate (2.00 g, 8.57 mmol) was used as a raw material and dissolved in a mixed solvent of methanol (10 mL) and tetrahydrofuran (10 mL). Subsequently, 2 N aqueous lithium hydroxide (8.6 mL) was added to this solution. The reaction mixture was heated to reflux for 20 minutes. Upon completion of the reaction, the reaction solution was cooled in an ice bath, adjusted to acidity with aqueous potassium bisulfate, and then extracted with ethyl acetate. The organic layers were combined, concentrated and purified by repurification (ethyl acetate/hexane) and dried to give 1-benzyl-5-oxo-3-pyrrolidinecarboxylic acid (1.83 g, 97% yield).1H-NMR (DMSO-d6) δ: 2.56 (2H, m), 3.80 (1H, m), 3.15 (2H, m), 3.25 (2H, m), 4.36 (2H , q, J = 8.6 Hz), 7.27 (5H, m), 12.61 (1H, s).
