[CH2:1]([O:8][C:9]([N:11]1[CH2:16][CH2:15][CH:14]([C:17](=[O:21])[CH:18]=[N+]=[N-])[CH2:13][CH2:12]1)=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[BrH:22].CC(O)=O.C([O-])(O)=O.[Na+]>CCOC(C)=O>[CH2:1]([O:8][C:9]([N:11]1[CH2:16][CH2:15][CH:14]([C:17](=[O:21])[CH2:18][Br:22])[CH2:13][CH2:12]1)=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=14-(2-Diazo-acetyl)-piperidine-1-carboxylic acid benzyl ester (44 g, 0.15 mol) in EtOAc (300 mL) was cooled to 0° C. The solution was treated with 33% HBr/HOAc (75 mL, 0.42 mol) over 15 min and stirred at ambient temperature for 2 hours. The mixture was slowly treated with saturated NaHCO3 solution (300 mL) until pH was neutral or slightly basic and filtered. The solution was dried over MgSO4 and subjected to a 330 g SiO2 COMBIFLASH column (0-100% EtOAc-hexanes gradient) to afford 4-(2-bromo-acetyl)-piperidine-1-carboxylic acid benzyl ester (38.1 g, 81%): MS (ESI) m/z 341 [M+H]+.
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