[H-].[Na+].[C:3]([O:7][C:8]([N:10]1[CH2:15][CH2:14][CH2:13][CH2:12][C:11]1=O)=[O:9])([CH3:6])([CH3:5])[CH3:4].[F:17][C:18]1[CH:32]=[CH:31][C:21]([CH2:22]P(=O)(OCC)OCC)=[CH:20][CH:19]=1.C(=O)(O)[O-].[Na+]>O1CCCC1.C1OCCOCCOCCOCCOC1>[C:3]([O:7][C:8]([N:10]1[CH2:15][CH2:14][C:13](=[CH:22][C:21]2[CH:31]=[CH:32][C:18]([F:17])=[CH:19][CH:20]=2)[CH2:12][CH2:11]1)=[O:9])([CH3:6])([CH3:5])[CH3:4]To a stirred suspension of 13.20 g of 60% sodium hydride (in oil) containing 1.65 g of 15-crown-5 ether in 650 ml of tetrahydrofuran were added dropwise a solution of 59.78 g of N-t-butoxycarbonylpiperidone and 81.25 g of diethyl 4-fluorobenzylphosphonate in 150 ml of tetrahydrofuran under ice-cooling over 20 minutes. After stirring at room temperature for a day, a saturated aqueous sodium bicarbonate solution was added cautiously, followed by extracting with ethyl acetate. The extract was washed with a saturated aqueous sodium bicarbonate solution and a saturated aqueous sodium chloride solution, successively, and dried over anhydrous sodium sulfate, followed by removal of the drying agent by filtration. The filtrate was concentrated under reduced pressure and purified by a flash column chromatography (silica gel: Wakogel C200 (manufactured by Wako Pure Chemicals), eluent; hexane-ethyl acetate =20:1) to give 55.23 g of N-t-butoxycarbonyl-4-(4-fluorobenzylidene)piperidine as an oil, which was then crystallized by allowing to stand at room temperature overnight.
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