[OH:1][CH2:2][C:3]1[CH:19]=[CH:18][C:6]([CH2:7][C:8]2[C:9]([O:11][C:12](=O)C=2C(C)C)=[O:10])=[CH:5][CH:4]=1.CO.O1C[CH2:25][CH2:24][CH2:23]1.C[Si](C=[N+]=[N-])(C)C.CCCCCC.C1(C)C=CC=CC=1.[C:47]([O:50][CH2:51]C)(=[O:49])[CH3:48]>>[OH:1][CH2:2][C:3]1[CH:19]=[CH:18][C:6]([CH2:7]/[C:8](=[C:48](\[CH:24]([CH3:25])[CH3:23])/[C:47]([O:50][CH3:51])=[O:49])/[C:9]([O:11][CH3:12])=[O:10])=[CH:5][CH:4]=1To a solution of 2-[4-(hydroxymethyl)benzyl]-3-isopropylmaleic anhydride (101 mg, 0.388 mmol) in a mixed solvent of methanol (1.0 mL) and tetrahydrofuran (1.0 mL) was added a 2.0 M trimethylsilyl diazomethane-hexane solution (1.0 mL, 2.0 mmol) with stirring under ice cooling. The reaction mixture was stirred at room temperature for 2 h and directly concentrated under reduced pressure. The residue thus obtained was subjected to silica gel column chromatography (toluene-ethyl acetate 4:1→3:1) to give 96 mg of dimethyl 2-[4-(hydroxymethyl)benzyl]-3-isopropylmaleate as oil (yield: 81%).
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