To a solution of (E)-ethyl 4-bromo-3-(1-ethoxycarbonylcyclopropyl)-2-fluoro-2-butenoate (143 mmol) in ethanol (1000 ml) was added sodium hydrogencarbonate (30.08 g, 358 mmol). After adding dropwise 1-(S)-phenylethylamine (20.31 ml, 158 mmol) thereinto at room temperature, the mixture was heated under reflux for 3 hours. Then the liquid reaction mixture was cooled and filtered through celite. The filtrate was concentrated under reduced pressure and the residue was subjected to flash silica gel column chromatography (eluent:n-hexane:ethyl acetate=2:1) to obtain 36.95 g (81.2%) of the-title compound as an oily substance.
