Hydrochloric Acid → (S)-2-Methylcysteine hydrochloride

Temperature

20 °C

18.6 g of 4-methyl-2-phenylthiazoline-4-carboxylic acid were dissolved in 186 ml of 6 N HCl under a nitrogen atmosphere and the solution was then heated under reflux for 16 hours. After cooling to 20° C., the precipitated benzoic acid was filtered off and washed with 2×10 ml of completely demineralized water. The filtrate was extracted three times with 95 ml each of MTBE, then residual MTBE was stripped off by evacuation at room temperature and only then was the water removed by distillation at reduced pressure and at most 40° C. The oil obtained was dissolved in 110 ml of water and again concentrated down to an about 50% strength solution. 300 ml of 2-butanol were added to this concentrated solution and the residual water was entrained by distilling off the azeotrope of 2-butanol and water (total: 250 ml). In the course of this, a water content of 0.6 gg % was achieved in the last distillate fraction. The concentrated solution obtained was further concentrated under reduced pressure, cooled to room temperature and then treated with 200 ml of MTBE. The precipitated crystals were filtered off with suction, washed 2× with 20 ml each of MTBE and dried at 45° C./30 mbar.

1. temperaturethe solution was then heated
2. temperatureunder reflux for 16 hours
3. filtrationthe precipitated benzoic acid was filtered off
4. washwashed with 2×10 ml of completely demineralized water
5. extractionThe filtrate was extracted three times with 95 ml each of MTBE
6. customwas stripped off by evacuation at room temperature
7. customremoved by distillation at reduced pressure and at most 40° C
8. customThe oil obtained
9. concentrationagain concentrated down to an about 50% strength solution
10. addition300 ml of 2-butanol were added to this concentrated solution
11. distillationby distilling off the azeotrope of 2-butanol and water (total: 250 ml)
12. customThe concentrated solution obtained
13. concentrationwas further concentrated under reduced pressure
14. temperaturecooled to room temperature
15. additiontreated with 200 ml of MTBE
16. filtrationThe precipitated crystals were filtered off with suction
17. washwashed 2× with 20 ml each of MTBE
18. customdried at 45° C./30 mbar

ORD record

ord-34974ad1aa7f457d96db9838f3281727

Source dataset

uspto-grants-2005_05

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06894170B2