[ClH:1].C(OC([NH:9][CH2:10][C@@H:11]([N:16]1[CH2:21][CH2:20][N:19]([S:22]([CH3:25])(=[O:24])=[O:23])[CH2:18][CH2:17]1)[C:12]([O:14][CH3:15])=[O:13])=O)(C)(C)C>C(O)(C)C.CO>[ClH:1].[NH2:9][CH2:10][C@@H:11]([N:16]1[CH2:21][CH2:20][N:19]([S:22]([CH3:25])(=[O:24])=[O:23])[CH2:18][CH2:17]1)[C:12]([O:14][CH3:15])=[O:13]15 ml of a solution of hydrochloric acid in isopropanol having a concentration of 5-6N are added dropwise to a solution of 3.8 g (10.4 mmol) of methyl (R)-3-tert-butoxycarbonylamino-2-(4-methanesulphonylpiperazin-1-yl)propanoate in 50 ml of methanol. The reaction medium is stirred at 40° C. for 3 h, concentrated under vacuum then taken up in diethyl ether. The product precipitates, is filtered, rinsed with diethyl ether then dried under vacuum. 3 g (97%) of methyl (R)-3-amino-2-(4-methanesulphonylpiperazin-1-yl)propanoate hydrochloride are obtained in the form of a beige solid.
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