To (1R,3R)-methyl 1-amino-3-(4-bromophenyl)cyclopentanecarboxylate (1.5 g, 5.03 mmol) in acetonitrile (7.2 ml) and water (1.800 ml) was added N-(Benzyloxycarbonyloxy)succinimide (1.254 g, 5.03 mmol) followed by potassium carbonate (0.695 g, 5.03 mmol). The reaction mixture was stirred for 1 hour at room temperature. The solvent was removed and the remaining aqueous slurry was taken up in water and ethyl acetate. The organic layer was removed and washed with brine, dried over MgSO4 and concentrated in vacuo. The crude was purified by flash chromatography to yield (1R,3R)-methyl 1-(benzyloxycarbonylamino)-3-(4-bromophenyl)cyclopentanecarboxylate (1.4 g, 3.24 mmol, 64.4% yield) as an off white gum.
