General procedure for the synthesis of N-Boc-N-methyl-4-aminomethylbutanol from 4-(methylamino)butan-1-ol and di-tert-butyl dicarbonate: a solution of 4-(methylamino)butan-1-ol (2.76g, 26.8mmol) in triethylamine/methanol (1:7 v/v, 100mL) was stirred for 10 minutes at 0 °C. Subsequently, a solution of di-tert-butyl dicarbonate (8.76 g, 40.2 mmol) in methanol (20 mL) was added dropwise over 10 min. The reaction mixture was stirred under nitrogen protection for 1 hour. After that, the temperature of the reaction system was allowed to gradually increase to room temperature and stirring was continued overnight. Upon completion of the reaction, the solvent was removed by evaporation under reduced pressure and the residue was dissolved in dichloromethane and washed with deionized water. The organic layer was separated, dried with anhydrous sodium sulfate, filtered and concentrated to afford the colorless oily product N-Boc-N-methyl-4-aminomethylbutanol (4.54 g, 84% yield), which could be used in the next reaction without further purification.1H NMR (CDCl3) δ 3.66 (t, 2H), 3.23 (t, 2H), 2.83 (s, 3H), 1.78 (br s, 1H), 1.51-1.60 (m, 4H), 1.44 (s, 9H).
