[Synthesis]
GENERAL STEPS: 1-benzyl-5-oxo-3-pyrrolidinecarboxylic acid (1.00 g, 4.56 mmol) was dissolved in tert-butanol (6 mL) followed by the addition of triethylamine (0.76 mL, 5.5 mmol). Next, a solution of diphenylphosphoryl azide (1.38 g, 5.02 mmol) in tert-butanol (4 mL) was slowly added dropwise to the reaction system. The resulting reaction mixture was heated to reflux for 2 hours. Upon completion of the reaction, the reaction solution was concentrated under reduced pressure and toluene was used as an azeotropic solvent to completely remove the tert-butanol. The residue was purified by silica gel column chromatography with the eluent being a mixed ethyl acetate/hexane solvent to give tert-butyl (1-benzyl-5-oxopyrrolidin-3-yl)carbamate (480 mg, 51% yield). The structure of the product was confirmed by 1H-NMR (DMSO-d6): δ 1.34 (9H, s), 2.23 (1H, dd, J = 5.7, 16.8 Hz), 2.61 (1H, dd, J = 8.6, 16.8 Hz), 3.01 (1H, dd, J = 5.7, 9.9 Hz), 3.43 (1H, dd, J = 8.6, 9.9 Hz), 4.03 (1H, m), 4.36 (2H, s), 7.30 (6H, m). |