General procedure for the synthesis of 4-(benzyloxy)-1-(tert-butoxycarbonyl)pyrrolidine-2-carboxylic acid from 1-(tert-butyl) 2-methyl (2S,4R)-4-(benzyloxy)pyrrolidine-1,2-dicarboxylic acid ester: lithium hydroxide was added to a mixture of THF and H2O (60 mL, 2:1, v/v/v/v/v) of compound 2 (3.45 g, 10.29 mmol) monohydrate (1.29 g, 30.87 mmol). The reaction mixture was stirred at room temperature for 3 hours. After the completion of the reaction was monitored by TLC, the reaction mixture was concentrated under reduced pressure, acidified to pH < 7 with 1N hydrochloric acid solution and subsequently extracted with ethyl acetate (3 x 30 mL). The organic layers were combined, washed with saturated sodium chloride solution (30 mL), dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give the crude product. The crude product was purified by grinding with pentane (20 mL) to give compound 3 (3.21 g, 97% yield) in white solid form. Mass spectrum (ESI) m/z 322 [M+H]+.
