[C:1]([O:6][CH2:7][CH3:8])(=[O:5])[CH:2]([CH3:4])[CH3:3].[Li+].CC([N-]C(C)C)C.[CH2:17]([O:24][C:25]1[CH:32]=[CH:31][C:28]([CH:29]=[O:30])=[CH:27][CH:26]=1)[C:18]1[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=1.O>C1COCC1>[CH2:7]([O:6][C:1](=[O:5])[C:2]([CH3:4])([CH3:3])[CH:29]([C:28]1[CH:27]=[CH:26][C:25]([O:24][CH2:17][C:18]2[CH:19]=[CH:20][CH:21]=[CH:22][CH:23]=2)=[CH:32][CH:31]=1)[OH:30])[CH3:8]Ethyl isobutyrate (2.5 mL, 18.42 mmol) was dissolved in THF (8 mL), and the solution was cooled to −78° C. LDA (9.2 mL, 18.42 mmol) was added thereto, and the mixture was stirred at the corresponding temperature for 2 hours. After 4-benzyloxy-benzaldehyde (1.7 g, 8.01 mmol) obtained in Step A was added thereto at −78° C., the mixture was heated to room temperature, and then stirred for 2 days. The reactant was added with water, and then extracted with EtOAc. The organic layer was concentrated under reduced pressure. The residue was purified by column chromatography (eluent, EtOAc/Hex=1/5) to obtain the title compound (1.77 g, 67%).
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