Carbamic acid, [(2R)-2-aminopropyl]-, 1,1-dimethylethyl ester (9CI)

Synthesis

NaOH (8.82 g, 0.2205 mol) was dissolved in 96% ethanol (150 mL) under vigorous stirring, followed by the addition of (S)-(-)-diaminopropane dihydrochloride (16.36 g, 0.11 mol). After 2 hours of reaction, the resulting white precipitate was removed by filtration. To the filtrate was added tert-butyl phenyl carbonate (39.37 g, 0.203 mol) and the mixture was refluxed for 24 hours. After completion of the reaction, the solvent was removed by vacuum concentration to give a colorless oil. To this oily substance, water (175 mL) was added and the pH was adjusted to 3 with 2M H2SO4. The aqueous phase was washed with CH2Cl2 (3 x 200 mL) and then the pH was adjusted to 12 with 2M NaOH. Subsequently, the aqueous phase was extracted with CH2Cl2 (4 x 200 mL), and the organic phases were combined, dried over Na2SO4, and concentrated to give (R)-(2-aminopropyl)amino tert-butyl formate as a colorless oil (9.58 g, 50% yield). The product was characterized by 1H NMR (300 MHz, CDCl3), 13C NMR (126 MHz, CDCl3) and MS (FAB), and the correct structure was confirmed.

References

[1] Tetrahedron, 2015, vol. 71, # 7, p. 1109 - 1116
[2] Patent: US2009/247519, 2009, A1. Location in patent: Page/Page column 134