[Mg].Br[C:3]1[CH:8]=[CH:7][CH:6]=[CH:5][CH:4]=1.[C:9]([O:14][CH2:15][C:16]([CH2:18][O:19][C:20](=[O:24])[CH:21]([CH3:23])[CH3:22])=[O:17])(=[O:13])[CH:10]([CH3:12])[CH3:11].Cl>C(OCC)C>[C:9]([O:14][CH2:15][C:16]([C:3]1[CH:8]=[CH:7][CH:6]=[CH:5][CH:4]=1)([OH:17])[CH2:18][O:19][C:20](=[O:24])[CH:21]([CH3:23])[CH3:22])(=[O:13])[CH:10]([CH3:12])[CH3:11]Under an atmosphere of argon, 2 ml of diethyl ether was slowly added to 695 mg of magnesium turnings, and then thereto was added dropwise 4 g of bromobenzene dissolved in 10 ml of diethyl ether. The resulting liquid was stirred for 1 hour under refluxing and allowed to cool. That liquid was added dropwise to 50 ml of diethyl ether solution of 3.78 g of 1,3-diisobutyryloxyacetone which was previously cooled to -50° C. After the resulting liquid was stirred at -50° C. for 1 hour, a temperature thereof was gradually raised to room temperature. Then, the reaction mixture was added to 50 ml of 2N aqueous solution of hydrochloric acid at 5° C. or below, and an organic layer was separated and the aqueous layer was extracted twice with 50 ml of ethyl acetate. The organic layers were combined and washed three times with 1N aqueous solution of sodium hydroxide, washed twice with saturated aqueous solution with sodium chloride, and dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure. The residue was purified by column chromatography on silica gel (eluent: n-hexane/ethyl acetate=1/1) to give 5.5 g of the desired compound.
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