[Si:1]([O:8][CH:9]1[CH2:13][C:12](=[O:14])[C:11]([CH2:15][CH:16]=[CH2:17])=[CH:10]1)([C:4]([CH3:7])([CH3:6])[CH3:5])([CH3:3])[CH3:2].O1CCC[CH2:19]1.C[Li].C(O)(=O)CC(CC(O)=O)(C(O)=O)O>C(OCC)C>[Si:1]([O:8][CH:9]1[CH2:13][C:12]([CH3:19])([OH:14])[C:11]([CH2:15][CH:16]=[CH2:17])=[CH:10]1)([C:4]([CH3:7])([CH3:6])[CH3:5])([CH3:2])[CH3:3]
To a solution mixture of 5 g of (RS)-3-allyl-4-oxo-2-cyclopenten-1-yl (t-butyldimethylsilyl) ether and 50 ml of tetrahydrofuran was added under nitrogen stream 23.7 ml of 1.07 M diethyl ether solution of methyllithium at -78° C. and the resulting mixture was stirred at the same temperature for 2 hours. Then, the reaction liquid was poured into ice-cooled 5% aqueous solution of citric acid and extracted two times with diethyl ether. The combined ether layer was washed successively with saturated aqueous sodium bicarbonate solution and saturated aqueous sodium chloride solution, then dried over anhydrous magnesium sulfate, and the solvent was distilled off under reduced pressure. The residue thus obtained was subjected to silica gel column chromatography to obtain 4.7 g of (1RS,4RS)-3-allyl-4-methyl-4-hydroxy-2-cyclopenten-1-yl (t-butyldimethylsilyl) ether. Yield 84%
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