Synthesis
GENERAL STEPS: An 800 mL methanol solution containing 16.53 g (0.453 mol) of dry HCl was slowly added dropwise to 51.78 g (0.453 mol) of trans-(1R,2R)-1,2-diaminocyclohexane dissolved in 80 mL of methanol, and the dropwise addition process lasted for 2 hours. After the dropwise addition, 50 mL of water was added, followed by the addition of 98.97 g (0.453 mol) of di-tert-butyl dicarbonate in batches and the addition process lasted for 1 hour. The reaction mixture was stirred for 2 hours, after which the methanol was removed by rotary evaporation. The residue was washed with 900 mL of ether, filtered to remove insoluble material and dried. The crude product was dissolved in 800 mL of water and then extracted with a mixture of 500 mL of dichloromethane and 340 mL of 2M NaOH. The organic layer was retained, dried with anhydrous magnesium sulfate and evaporated to remove the solvent. Finally, 67.87 g (70% yield) of trans-(1R,2R)-1-Boc-amino-2-aminocyclohexane was obtained by recrystallization from 900 mL of petroleum ether.
References
[1] Archiv der Pharmazie, 2012, vol. 345, # 11, p. 896 - 901
[2] Bulletin of the Chemical Society of Japan, 2017, vol. 90, # 3, p. 312 - 321
[3] Bioorganic and Medicinal Chemistry Letters, 2013, vol. 23, # 13, p. 3793 - 3797
[4] Patent: US5021571, 1991, A
[5] Patent: US5089663, 1992, A
