[C:1]1([CH2:7][CH2:8][CH2:9][CH2:10][O:11][CH2:12][CH2:13][CH:14]=[O:15])[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1.[CH2:16]([Mg]Br)[CH2:17][CH:18]=[CH2:19].C(O)(=O)C>C1COCC1>[C:1]1([CH2:7][CH2:8][CH2:9][CH2:10][O:11][CH2:12][CH2:13][CH:14]([OH:15])[CH2:19][CH2:18][CH:17]=[CH2:16])[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1A solution of Intermediate 13 (0.55 g, 2.66 mmol) in THF (5 mL) was cooled to −30° C. To this solution a 0.5 M solution of 3-butenylmagnesium bromide (5.8 mL, 2.92 mmol) in THF was added, and the resulting mixture was stirred 2 hours at −30° C. The reaction was allowed to reach room temperature; acetic acid (0.1 mL) was added and concentrated. Purification by column chromatography with silica gel and methylene chloride/acetone (20:1) as eluent afforded the title compound (410 mg, 54%) as oil.
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