[CH3:1][CH2:2][C:3](=[O:9])[CH2:4][C:5](=[O:8])[CH2:6][CH3:7].[H-].[Na+].[CH2:12]([O:14][C:15](=[O:18])[CH2:16]Br)[CH3:13]>O1CCCC1>[CH2:12]([O:14][C:15](=[O:18])[CH2:16][CH:4]([C:3](=[O:9])[CH2:2][CH3:1])[C:5](=[O:8])[CH2:6][CH3:7])[CH3:13]Dissolve heptane-3,5-dione (2.5 g, 19.5 mmol) in dry tetrahydrofuran (10 mL) and add the resulting solution dropwise to a chilled (0° C.) suspension of sodium hydride (0.94 g, 23.4 mmol, 60% dispersion in oil) in tetrahydrofuran (20 mL). Stir at 0° C. for 1 hr., then add bromoacetic acid ethyl ester (2.6 mL, 23.4 mmol) dropwise. Stir for 16 hr. at 0° C. and warm to room temperature. Partition the reaction mixture between diethyl ether (100 mL) and saturated aqueous ammonium chloride solution (50 mL). Separate the organic layer and wash with saturated aqueous sodium chloride solution (50 mL), dry (sodium sulfate), filter and concentrate. Purify using silica gel chromatography, eluting with 10:1 hexanes:ethyl acetate, to give 4-oxo-3-propionyl-hexanoic acid ethyl ester as an oil (3.2 g, 77%). 1H-NMR (400 MHz, CDCl3) δ 4.08 (m, 3H), 2.83 (d, 2H), 2.55 (q, 2H), 1.21 (t, 3H), 1.02 (t, 6H).
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