The general procedure for the synthesis of (1S,3R)-3-((tert-butoxycarbonyl)amino)cyclopent-2-enecarboxylic acid using (1R,4S)-4-((tert-butoxycarbonyl)amino)cyclopent-2-enecarboxylic acid as a starting material was as follows: (1R,4S)-4-((tert-butoxycarbonyl)amino)cyclopent-2-enecarboxylic acid (230 g, 1.0 mol) prepared in step A was hydrogenated with 10% Pd/ C catalyst (5.0 g) in 500 mL of methanol and hydrogenated on a Parr shaker at 50 psi hydrogen pressure for 1 hour. Upon completion of the reaction, the catalyst was removed by filtration followed by evaporation of the filtrate to remove the solvent. The resulting residue was dissolved in dichloromethane and dried by adding anhydrous sodium sulfate. After filtration again, the filtrate was evaporated and dried under vacuum to afford (1S,3R)-3-((tert-butoxycarbonyl)amino)cyclopentanecarboxylic acid as a light yellow solid (230 g, 99% yield). Analyzed by LC-MS, the calculated value of [M+H+] for C11H19NO4 was 230 and the measured value was 230, which was as expected.
