[C:1]([NH:4][C@H:5]1[CH2:10][CH2:9][N:8](C(OC)=O)[C@H:7]([CH2:15][C:16]2[CH:21]=[CH:20][C:19]([Cl:22])=[CH:18][CH:17]=2)[CH2:6]1)(=[O:3])[CH3:2].Br.O>C(O)(=O)C>[Cl:22][C:19]1[CH:18]=[CH:17][C:16]([CH2:15][C@@H:7]2[CH2:6][C@@H:5]([NH:4][C:1](=[O:3])[CH3:2])[CH2:10][CH2:9][NH:8]2)=[CH:21][CH:20]=1Methyl (2R*,4S*)-4-acetylamino-2-(4-chlorobenzyl)piperidine-1-carboxylate (30.0 g, 92.3 mmol) are treated with 51.8 ml 33% strength hydrogen bromide in acetic acid. After 16 hours, the mixture is treated with 200 ml of water and washed twice with toluene. The aqueous phase is rendered basic and extracted twice with ethyl acetate. The organic phases are dried on potassium carbonate and evaporated on a rotary evaporator. The title compound crystallizes from EtOHI ethyl acetate as the hydrochloride. M.p.: 288-289° C. TLC: methylene chloride/methanolconc. ammonia (90:9:1) Rf =0.17, FD-MS: (M+1)+ =267.
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