[CH2:1]([Li])[CH2:2][CH2:3][CH3:4].CCCCCC.[OH:12][CH:13]1[CH2:17][C:16](=[O:18])[CH:15]=[CH:14]1>O1CCCC1>[CH2:1]([C:16]1([OH:18])[CH2:17][CH:13]([OH:12])[CH:14]=[CH:15]1)[CH2:2][CH2:3][CH3:4]30 ml of tetrahydrofuran was put in a reaction tube and cooled to -78° C., and n-butyllithium (as a 1.6M hexane solution; 13.8 ml, 22.08 mmmoles) was added dropwise. Then a solution of 4-hydroxy-2-cyclopentenone (987 mg; 10.1 mmoles) in 20 ml of tetrahydrofuran was added dropwise over about 20 minutes. The reaction mixture was washed with 8 ml of tetrahydrofuran. After 60 minutes, 40 ml of a saturated aqueous solution of ammonium chloride was added, and the mixture was vigorously shaken. The organic layer was separated, and the aqueous layer was extracted with ethyl acetate (20 ml×6). The extracts were dried over anhydrous sodium sulfate, filtered and concentrated. The residue was chromatographed on a silica gel column (Merck silica gel 30 g; hexane:ethyl acetate=4:1) to obtain 1.55 g (yield about 90%) of 4-butylcyclopent-2-ene-1,4-diol.
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