General procedure for the synthesis of methyl 5-oxopyrrolidine-3-carboxylate from methyl 1-(benzyloxy)-5-oxopyrrolidine-3-carboxylate: to an autoclave was added methyl 1-(benzyloxy)-5-oxopyrrolidine-3-carboxylate (51.0 g, 0.205 mol), 10% Pd-C catalyst (9.0 g) and methanol (400 mL). The reaction mixture was stirred vigorously at room temperature under 50 atm hydrogen pressure for 24 hours. Upon completion of the reaction, the suspension was filtered to remove the catalyst and the catalyst residue was washed with methanol (2 x 100 mL). The filtrate and washings were combined and the solvent was removed by distillation under reduced pressure to afford the colorless oily product methyl 5-oxopyrrolidine-3-carboxylate (29.2 g, 100% yield), which crystallized upon standing. The melting point of the product was 55-58 °C (literature value 10b 61-62 °C). Mass spectrum (m/z, CI): 287 (M2H+), 144 (MH+). Elemental analysis (C6H9NO3) Calculated values: C 50.35, H 6.34, N 9.79; measured values: C 50.13, H 6.47, N 10.02.1H NMR (500 MHz, DMSO-d6) δ 7.67 (s, 1H), 3.64 (s, 3H), 3.46 (t, J=11.1Hz, 1H), 3.39- 3.31 (m, 2H), 2.43-2.28 (m, 2H).13C NMR (126 MHz, DMSO-d6) δ 175.4,174.0,52.4,44.0,38.4,33.4.
