Hydrochloric Acid → (S)-2-Methylcysteine hydrochloride

S-tert-butyl-α-methyl-D-cysteine (20 g) was dissolved in conc. hydrochloric acid (180 g), and the resultant solution was refluxed under heating for 45 hours. The reaction solution was allowed to cool down to room temperature, and then concentrated to 35 g. Then, the solution was heated to 40° C., and toluene (110 mL) was added to the solution, followed by concentration to about 40 g. This operation was further repeated four times, and the produced solid was filtered off and dried under vacuum at 60° C. for 48 hours to obtain the title compound as a white solid (15.3 g). As a result of HPLC analysis (column: CAPCELL PAK SCX (produced by Shiseido Co., Ltd.), mobile phase: potassium dihydrogen phosphate-phosphoric acid solution (pH 2.0)/acetonitrile=95/5, flow rate: 0.3 ml/min, detection wavelength: 210 nm, column temperature: 30° C.), it was confirmed that the solid was the desired compound (yield 84.6%). The measurement of optical rotation showed [α]D20=−6.28 (c1. 21, H2O). Since the sign of the optical rotation was opposite to that of the α-methyl-L-cysteine hydrochloride produced in EXAMPLE 10, it was confirmed that the obtained compound was the intended D-stereoisomer.

1. temperatureunder heating for 45 hours
2. concentrationconcentrated to 35 g
3. temperatureThen, the solution was heated to 40° C.
4. additiontoluene (110 mL) was added to the solution
5. concentrationfollowed by concentration to about 40 g
6. filtrationthe produced solid was filtered off
7. customdried under vacuum at 60° C. for 48 hours

ORD record

ord-5550220fc6bf4ab1acf8675d7e44d5b1

Source dataset

uspto-grants-2015_03

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08993800B2