[C:1]([O-:4])([O-:3])=O.[K+].[K+].[NH:7]1[CH2:12][CH2:11][CH2:10][CH2:9][CH2:8]1.[C:13](Cl)([O:15][CH2:16][C:17]1[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=1)=[O:14].[CH2:24]1COC[CH2:25]1.O>>[CH2:24]([O:3][C:1]([C@H:9]1[CH2:10][CH2:11][CH2:12][N:7]([C:13]([O:15][CH2:16][C:17]2[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=2)=[O:14])[CH2:8]1)=[O:4])[CH3:25]A 250 mL round-bottom flask was charged with K2CO3 (13.5 g, 97.6 mmol), piperidine (10 g, 32.5 mmol), and a 1:1 mixture of THF/H2O (100 mL). A 50 mL addition funnel was placed on the flask and charged with CbzCl (6.67 g, 39.0 mmol). The flask was cooled to 0° C. and then CbzCl was added dropwise over 5 minutes. The reaction mixture was warmed to 20° C. and stirred for 12 h. The reaction mixture was extracted with EtOAc (250 mL) and the organic layer was washed with saturated NaCl (250 mL), dried (MgSO4), filtered and concentrated in vacuo. The crude material (9.5 g, 100% yield) was carried on without further purification.
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