C([CH:5]1[CH:9]([OH:10])[CH2:8][CH2:7][N:6]1[C:11]([OH:13])=[O:12])(C)(C)C.[H-].[Na+].[Cl:16][C:17]1[CH:24]=[CH:23][C:20]([CH2:21]Br)=[CH:19][CH:18]=1>C1COCC1>[C:20]([O:13][C:11]([N:6]1[CH2:7][CH2:8][CH:9]([O:10][CH2:21][C:20]2[CH:23]=[CH:24][C:17]([Cl:16])=[CH:18][CH:19]=2)[CH2:5]1)=[O:12])([CH3:23])([CH3:21])[CH3:19]A solution of tert-butyl 3-hydroxy-1-pyrrolidinecarboxylic acid (0.27 g, 1.44 mmol) in dry THF (4 mL) was added dropwise to a cold (0° C.), stirred suspension of sodium hydride (0.078 g, 2.17 mmol, ca. 50% suspension in oil) in THF (10 mL). After 30 min. a solution of 4-chlorobenzyl bromide (0.36 g, 1.74 mmol) in THF (2 mL) was added and the resulting suspension was stirred at R.T. overnight. The reaction mixture was partitioned between water and ethyl acetate. The aqueous phase was extracted with ethyl acetate and the combined organic phase was washed with saturated aqueous sodium chloride, dried and concentrated. The residue was subjected to flash chromatography (heptane-ethyl acetate, 6:1) to afford the subtitle compound 3-(4-Chloro-benzyloxy)-pyrrolidine-1-carboxylic acid tert-butyl ester as an oil (0.30 g, 66.8%).
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