[Br:1][CH:2]([CH3:12])[C:3]([NH:5][C:6]([CH3:11])([CH3:10])[C:7]([OH:9])=[O:8])=O.C(N(CC)CC)C.ClC(OCC)=O>CC(C)=O>[Br:1][CH:2]([C:3]1[O:8][C:7](=[O:9])[C:6]([CH3:11])([CH3:10])[N:5]=1)[CH3:12]To a stirring mixture of 2-(2-bromopropionylamino)-2-methyl propionic acid (50.00 g, 0.21 mol), triethylamine (23.37 g, 0.23 mol), and 150 mL acetone cooled to 5° C., was added dropwise a solution of ethyl chloroformate (25.07 g, 0.23 mol) in 40 mL acetone. After full addition, the mixture was allowed to warm to room temperature, and was stirred for two hours. The mixture was filtered, and the solid was washed with ether. The solvent was then removed under vacuum, and the residue was filtered. The filtrate was distilled under reduced pressure to give a colorless oil (bp 63-64° C. at 1 mmHg). A yield of 34.73 g (75%) was obtained.
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