[Li+].C[Si]([N-][Si](C)(C)C)(C)C.[O:11]=[C:12]1[CH2:16][CH2:15][CH2:14][N:13]1[C:17]([O:19][C:20]([CH3:23])([CH3:22])[CH3:21])=[O:18].Br[CH2:25][C:26]1[CH:31]=[CH:30][C:29]([Cl:32])=[CH:28][CH:27]=1.C1C[O:36]CC1>>[C:20]([O:19][C:17]([NH:13][CH2:14][CH2:15][CH:16]([CH2:25][C:26]1[CH:31]=[CH:30][C:29]([Cl:32])=[CH:28][CH:27]=1)[C:12]([OH:36])=[O:11])=[O:18])([CH3:23])([CH3:22])[CH3:21]LHMDS (28.3 mL, 28.3 mmol) was diluted into THF (90 mL) and cooled to −78° C. tert-Butyl 2-oxopyrrolidine-1-carboxylate (5.00 g, 27.0 mmol) was dissolved into THF (35 mL) and added to the LHMDS over a 5 minute period at −78° C. The reaction was allowed to stir for 45 minutes, and then a THF (35 mL) solution of 1-(bromomethyl)-4-chlorobenzene (5.82 g, 28.3 mmol, 1.05 equiv) was added. The reaction was allowed to stir at −78° C. for 1 hour, and then warmed to room temperature over 3 hours. The mixture was quenched with the addition of a 3M LiOH solution (90 mL) and stirred for 48 hours at room temperature. The reaction was then diluted with water and washed with ethyl acetate. The aqueous layer was acidified with 3M HCl and extracted several times with ethyl acetate. The combined organic fractions were washed with water, dried over MgSO4, filtered, and concentrated to give the crude product. The crude product was purified by column chromatography (60:40 hexanes:ethyl acetate) to give 4-(tert-butoxycarbonylamino)-2-(4-chlorobenzyl)butanoic acid (0.84 g, 9.4%).
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