[H-].[Na+].[NH:3]1[C:8](=O)[CH2:7][O:6][CH2:5][C:4]1=[O:10].F[B-](F)(F)F.[C:16]([C:21]1([P+](C2C=CC=CC=2)(C2C=CC=CC=2)C2C=CC=CC=2)[CH2:23][CH2:22]1)([O:18][CH2:19][CH3:20])=[O:17]>C1COCC1>[CH2:19]([O:18][C:16]([C:21]1[CH2:22][CH2:23][N:3]2[C:4](=[O:10])[CH2:5][O:6][CH2:7][C:8]=12)=[O:17])[CH3:20]To a suspension of sodium hydride (480 mg, 60% in mineral oil, 12 mmol) in 10 ml of anhydrous THF is added morpholine-3,5-dione (1.2 g, 10 mmol) in 20 ml of THF under an argon athmosphere. After 10 min., 1-carbethoxycyclopropyltriphenylphosphonium tetrafluoroborate (Fuchs' reagent, 6.8 g, 11 mmol)) in 20 ml of THF are added and the mixture is refluxed for 21 hours. After cooling, the suspension is concentrated on a rotary evaporator, poured onto ice/sat. sodium bicarbonate solution, and extracted three times with ether. The combined organic phases are washed with brine, dried over anhydrous sodium sulphate, and evaporated. The residual yellow oil (3.04 g) is purified by chromatography (Silica gel 60, 0.063-0.2 mesh, cyclohexane/ethyl acetate 1:1).
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