[OH-].[Li+].C([O:5][C:6](=[O:22])[CH2:7][CH2:8][N:9]1[CH2:14][CH2:13][N:12]([C:15]([O:17][C:18]([CH3:21])([CH3:20])[CH3:19])=[O:16])[CH2:11][CH2:10]1)C>C(O)C>[NH3:9].[C:18]([O:17][C:15]([N:12]1[CH2:11][CH2:10][N:9]([CH2:8][CH2:7][C:6]([OH:22])=[O:5])[CH2:14][CH2:13]1)=[O:16])([CH3:21])([CH3:19])[CH3:20]1N Aqueous lithium hydroxide (15.6 ml) was added to a solution of tert-butyl 4-(3-ethoxy-3-oxopropyl)-1-piperazinecarboxylate (2.23 g) [see Preparation 89] in ethanol (95 ml). The reaction mixture was stirred for 18 hrs at room temperature, after which time the solvent was removed under reduced pressure. The crude product was purified by column chromatography on reverse phase MCI gel eluting with 1:1, acetonitrile:water and further purified on Dowex 50W-X8-100 ion-exchange resin eluting with water and then 10% ammonia to afford 3-[4-(tert-butoxycarbonyl)piperazino]propanoic acid (1.33 g) as a white solid.
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