[C:1]([CH:4]([CH:10]([CH3:12])[CH3:11])[C:5]([O:7][CH2:8][CH3:9])=[O:6])(=[O:3])[CH3:2].[Br:13]Br.C(Cl)(Cl)Cl.C(OCC)(=O)C>O>[Br:13][CH2:2][C:1](=[O:3])[CH:4]([CH:10]([CH3:11])[CH3:12])[C:5]([O:7][CH2:8][CH3:9])=[O:6]To a solution of ethyl 2-acetyl-3-methylbutanoate (5.10 g, 29.6 mmol) in water (10 mL) at 0° C. was added bromine (1.53 mL, 29.6 mmol) dropwise over 2 h. Chloroform (30 mL) was added and the resulting solution was stirred at rt for 16 h. Ethyl acetate (300 mL) was added to the reaction solution and the organic phase was dried over sodium sulfate and concentrated to give the title compound. 1HNMR (500 MHz, CDCl3), δ4.300-4.282 (m, 2H), 2.601-2.575 (m, 1H), 2.406 (s, 2H), 1.331-1.303 (t, J=7.1 Hz, 3H), 1.085-1.072 (d, J=6.5 Hz, 3H), 1.048-1.035 (d, J=6.7 Hz, 3H).
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