Synthesis
The general procedure for the synthesis of 3-amino-2 has lactam hydrochloride from methyl-2,6-diaminohexane hydrochloride is as follows:
1. L-lysine hydrochloride (100.0 g, 547 mmol) was dissolved in methanol (1200 mL) and stirred at 0 °C and under argon protection for 30 min.
2. Thionyl chloride (80 mL, 1.10 mol) was added slowly and dropwise over 20 min at 0 °C.
3. the reaction solution was stirred at room temperature for 1 hour and refluxed overnight.
4. After completion of the reaction, the solvent was removed under vacuum and the crude product was recrystallized from methanol to give L-lysine methyl ester dihydrochloride (124.1 g, 97% yield).
5. L-lysine methyl ester dihydrochloride (60.0 g, 257 mmol) was dissolved in methanol (1200 mL) and stirred at room temperature and under argon protection.
6. The reaction solution was refluxed for 4 hours by adding sodium methanol (48.0 g, 889 mmol).
7. Hydrolyze by addition of ammonium chloride (20.0 g), filter the reaction solution and remove the solvent under vacuum.
8. The residue was dissolved in dimethoxyethane (80 mL) and the solvent was removed by filtration.
9. The residue was dissolved in ethanol (100 mL) and ethanol saturated with hydrochloric acid (20 mL) was added to obtain the crude product.
10. The crude product was recrystallized by methanol to give (S)-3-aminoazepin-2-one hydrochloride (27.8 g, 66% yield).
References
[1] Heterocycles, 2017, vol. 94, # 5, p. 964 - 978
