To a stirred solution of (3S)-3-(formylamino)pyrrolidine-1-carboxylic acid tert-butyl ester (2.29 g, 10 mmol) in tetrahydrofuran (35 ml) at 0°C was slowly added a tetrahydrofuran solution of 1 M borane (32 ml, 32 mmol). The reaction mixture was stirred at room temperature for 18 h. The reaction was quenched with methanol (10 ml) followed by vacuum concentration. The resulting white solid was redissolved in methanol (30 ml) and heated to reflux for 18 hours. Finally, the solvent was removed by vacuum evaporation to afford (S)-1-Boc-3-(methylamino)pyrrolidine as a light yellow oil (2.45 g, 12.2 mmol, 100% yield). The product was characterized by 1HNMR (400 MHz, CDCl3): δ 1.45 (s, 9H), 1.47-1.77 (m, 2H), 1.71 (m, 1H), 2.03 (m, 1H), 2.43 (s, 3H), 3.04-3.26 (m, 1H), 3.29-3.58 (m, 2H); LRMS m/z ELSD- apci+ 201 [mh]+.
