[CH3:1][C:2]1[C:6]2[CH:7]=[CH:8][CH:9]=[CH:10][C:5]=2[O:4][N:3]=1.[CH2:11](Br)[CH:12]=[CH2:13].[Li+].CC([N-]C(C)C)C.C(OCC)(=O)C>C1COCC1.O>[CH2:1]([C:2]1[C:6]2[CH:7]=[CH:8][CH:9]=[CH:10][C:5]=2[O:4][N:3]=1)[CH2:13][CH:12]=[CH2:11]3.0 mL dry THF was added to an oven-dried 25 mL flask and cooled to −78° C. on a dry ice/isopropanol bath. Diisopropylamine (840 μl, 6.0 mmol) was added followed by n-BuLi (3.8 mL, 1.6 M, 6.0 mmol). The LDA-solution that was obtained was left at room temperature. Compound 25 (666 mg, 5.0 mmol) was dissolved in 10 mL dry THF and added to an oven-dried 50 mL flask followed by allylbromide (476 μl, 5.5 mmol). The freshly prepared LDA-solution was slowly added at −78° C. and the mixture was left at room temperature for 30 min. Ethyl acetate and water were added. The phases were separated and the aqueous phase was extracted with ethyl acetate. The combined organic phases were dried over magnesium sulphate and evaporated to dryness to produce 893 mg of a light brown oil. Crude product was purified by column chromatography (heptane:ethyl acetate; 9:1; isocratic) to produce pure 26 (355 mg, 41%).
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