The general procedure for the synthesis of 1-BOC-pyrrolidine-3-carboxamide from (R)-1-Boc-3-carboxypyrrolidine was as follows: to a solution of 1-(tert-butoxycarbonyl)pyrrolidine-3-carboxylic acid (5 g, 23.23 mmol) in anhydrous THF (100 mL) was added triethylamine (TEA, 4.69 g, 46.46 mmol) and isobutyl chloroformic acid ester (3.8 g, 27.87 mmol). The reaction mixture was stirred at 0 °C for 20 min. Subsequently, ammonia (NH3-H2O) was slowly added and stirring was continued for 2 h at room temperature. After completion of the reaction, the reaction mixture was diluted with ethyl acetate (30 mL) and washed sequentially with saturated sodium carbonate solution (2 × 20 mL) and saturated sodium bicarbonate solution. The organic layer was then washed with citric acid solution (2 × 20 mL) to remove residual base. Finally, the organic layer was dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure to give the crude product (2.39 g, 49% yield) as a yellow solid. Mass spectrometry (ESI) analysis showed: m/z = 159.0 [M + H]+.
