[H-].[Na+].[C:3]([O:11][CH2:12][CH3:13])(=[O:10])[CH2:4][C:5]([O:7][CH2:8][CH3:9])=[O:6].Br[CH2:15][CH2:16][CH:17]=[CH2:18]>CN(C=O)C>[CH2:12]([O:11][C:3](=[O:10])[CH:4]([CH2:18][CH2:17][CH:16]=[CH2:15])[C:5]([O:7][CH2:8][CH3:9])=[O:6])[CH3:13]A mixture of sodium hydride (60% in mineral oil, 435 mg, 10.87 mmol, 1.1 eq) in DMF (20 mL) was treated dropwise with diethyl malonate (1.5 mL, 9.88 mmol, 1.0 eq). The reaction mixture was then cooled to 0° C. and 4-bromo-1-butene (1.0 mL, 9.88 mmol, 1 eq) was added dropwise. The reaction mixture was warmed to rt, stirred for 3 days and then partitioned between ether and water. The layers were separated, the aqueous layer was extracted with ether (2×50 mL) and the combined organic phases were washed with water (2×) and brine, dried over MgSO4 and concentrated. Column chromatography (SiO2, 5% ether/heptane) gave C8.1 (1.51 g, 71% yield) as a colorless oil. 1H NMR (400 MHz, DMSO-d6): δ 5.77 (m, 1 H), 5.00 (m, 2 H), 4.13 (q, J=7.1 Hz, 4 H), 3.43 (t, J=7.4 Hz, 1 H), 2.02 (m, 2 H), 1.84 (m, 2 H), 1.17 (t, J=7.1 Hz, 6 H).
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