C([O:3][C:4]([C:6]1([CH2:19][C:20]2[CH:25]=[CH:24][C:23]([Cl:26])=[CH:22][CH:21]=2)[CH2:11][CH2:10][CH2:9][N:8]([C:12]([O:14][C:15]([CH3:18])([CH3:17])[CH3:16])=[O:13])[CH2:7]1)=[O:5])C.[OH-].[Na+].Cl>C(O)(C)C>[C:12]([N:8]1[CH2:9][CH2:10][CH2:11][C:6]([CH2:19][C:20]2[CH:21]=[CH:22][C:23]([Cl:26])=[CH:24][CH:25]=2)([C:4]([OH:5])=[O:3])[CH2:7]1)([O:14][C:15]([CH3:17])([CH3:18])[CH3:16])=[O:13]A suspension of Ethyl-3-(4-chlorobenzyl)-N-Boc-piperidin-3-carboxylate (36.4 g, 0.105 mol) in isopropyl alcohol (300 mL) was treated with 10 N NaOH (300 mL). The mixture was heated at reflux for 48 hours. The reaction was cooled to room temperature and carefully neutralized by pouting over 1 L of crushed ice and adding 6 N HCl until pH 3. The mixture was then extracted with ethyl acetate (3×500 mL). The combined organic extracts were dried over anhydrous magnesium sulfate, filtered, and concentrated at reduced pressure to give 31 g of the product.
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