[ClH:1].C(OC([NH:9][C@@H:10]([CH2:19][CH3:20])[CH2:11][NH:12][C:13](=[O:18])[C:14]([O:16][CH3:17])=[O:15])=O)(C)(C)C>O1CCOCC1>[ClH:1].[NH2:9][C@@H:10]([CH2:19][CH3:20])[CH2:11][NH:12][C:13](=[O:18])[C:14]([O:16][CH3:17])=[O:15]To an ice cold solution of 4M HCl in dioxane (20 mL) was added (S)-methyl 2-((2-((tert-butoxycarbonyl)amino)butyl)amino)-2-oxoacetate (1.3 g, 4.6 mmol). After 30 minutes, the reaction mixture was concentrated to provide a yellow foam (968 mg, 100%), which was used without further purification. MS (ESI): mass calcd. for C7H14N2O3, 174.1; m/z found, 175.2 [M+H]+.
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