The general procedure for the synthesis of 1-tert-butyl (R)-2-methylaziridine-1,2-dicarboxylate from di-tert-butyl dicarbonate and methyl (R)-1-tritylaziridine-2-carboxylate was as follows: firstly, cyclopropylamine (1400 g, 4.08 mol, 1 eq.), a cyclopropyl amine (1400 g, 4.08 mol, 1 eq.), a 2-methyl-aziridine-2-carboxylic acid, was added to dichloromethane (7 L), which had been pre-cooled to 7 °C. The reaction mixture was then slowly stirred and cooled to -10 °C with stirring. Subsequently, trifluoroacetic acid (700 g, 6.14 mol, 1.5 eq.) was slowly added and the reaction mixture was cooled with stirring to -10°C. Next, triethylamine (1600 g, 15.84 mol, 3.88 eq.) was slowly added to adjust the pH to about 8. Under these conditions, BOC anhydride (900 g, 4.13 mol, 1.01 eq.) was slowly added dropwise. The reaction temperature was maintained between -10°C and 0°C and the pH was maintained at pH = 8. Upon completion of the reaction, water was added to quench the reaction, followed by washing with hydrochloric acid. The organic phase was dried with anhydrous sodium sulfate and then the solvent was removed by rotary evaporation to give a colorless oily product, 1-tert-butoxycarbonyl(R)-2-hydroxymethyl-cyclopropylamine, in 70% yield.
