Cl.[CH2:2]([N:9]1[CH2:14][CH2:13][C:12]([OH:18])([C:15]([OH:17])=[O:16])[CH2:11][CH2:10]1)[C:3]1[CH:8]=[CH:7][CH:6]=[CH:5][CH:4]=1.[C:19](OC(=O)C)(=[O:21])[CH3:20].N1C=CC=CC=1.OS([O-])(=O)=O.[K+]>C(Cl)Cl.C(O)C>[C:19]([O:18][C:12]1([C:15]([OH:17])=[O:16])[CH2:11][CH2:10][N:9]([CH2:2][C:3]2[CH:4]=[CH:5][CH:6]=[CH:7][CH:8]=2)[CH2:14][CH2:13]1)(=[O:21])[CH3:20]A mixture of 9.4 g 1-benzyl-4-hydroxy-piperidine-4-carboxylic acid, hydrochloride, 3.62 g (35 mmol) acetic anhydride, 11.89 mL pyridine in 40 mL DCM was stirred for 1 h at room temperature. KHSO4 (10%) and ethanol were added and filtered. The filtrate was evaporated and the residue was purified by preparative HPLC on reversed phase eluting with a gradient formed from acetonitrile, water and HCOOH. The product containing fractions were evaporated to yield 4.2 g (52%) of the title compound as light yellow solid. MS (m/e): 278.1 [(M+H)+].
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