[NH2:1][C@:2]1([C:14]([OH:16])=[O:15])[CH2:6][CH2:5][C@H:4]([C:7]2[CH:12]=[CH:11][C:10]([Br:13])=[CH:9][CH:8]=2)[CH2:3]1.S(Cl)(Cl)=O.[CH3:21]O>>[CH3:21][O:15][C:14]([C@@:2]1([NH2:1])[CH2:6][CH2:5][C@H:4]([C:7]2[CH:12]=[CH:11][C:10]([Br:13])=[CH:9][CH:8]=2)[CH2:3]1)=[O:16]The (1R,3S)-1-amino-3-(4-bromo-phenyl)-cyclopentanecarboxylic acid (79 g, 0.28 mol) suspended in MeOH (1.8 L) was cooled in an ice/water bath and thionyl chloride (178 mL, 2.44 mol) was added dropwise. Following the addition the reaction was heated to reflux. After 2 days the reaction mixture was cooled to room temperature, filtered, and rinsed with MeOH (2×200 mL). The filtrate was concentrated in vacuo to provide a white solid. The white solid was triturated with EtOAc (1 L), collected by filtration, rinsed with EtOAc (2×500 mL), and dried under vacuum to give the (1R,3S)-1-amino-3-(4-bromo-phenyl)-cyclopentanecarboxylic acid methyl ester; hydrochloride as a white solid (79 g, 96%).
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