[CH3:1][O:2][C:3](=[O:21])[C:4]([CH3:20])([CH3:19])[CH2:5][N:6]1[CH2:11][CH2:10][N:9](C(OC(C)(C)C)=O)[CH2:8][CH2:7]1.O1CCOCC1.[ClH:28]>C(O)(C)C>[ClH:28].[ClH:28].[CH3:19][C:4]([CH3:20])([CH2:5][N:6]1[CH2:11][CH2:10][NH:9][CH2:8][CH2:7]1)[C:3]([O:2][CH3:1])=[O:21]To a solution of tert-butyl 4-(3-methoxy-2,2-dimethyl-3-oxopropyl)piperazine-1-carboxylate (58.0 g, 193.08 mmoles) in isopropyl alcohol (150 mL) add a 4M dioxane solution of hydrogen chloride ((4 equiv); 193.08 mL, 772.31 mmoles) over 15 minutes, observing gas evolution and a fine precipitate. Heat at 55° C. for 3 h to give a white precipitate. Cool to 10° C. and collect the white solid by filtration, wash with further isopropyl alcohol (30 mL), then EtOAc. Dry in a vacuum oven at 45° C. for 1 h to give methyl 2,2-dimethyl-3-(piperazin-1-yl)propanoate dihydrochloride (31 g, 59% yield). MS (m/z): =201.1 (M+1).
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