[C:1]([O:4][CH2:5][CH:6](Br)[F:7])(=O)[CH3:2].[CH2:9]1C[O:12][CH2:11][CH2:10]1.C(OCC(Br)F)(=[O:16])C.C(=O)CC.C1COCC1.C(=O)CC.C(OC(C)C)(C)C>O>[F:7][CH:6]([CH:11]([OH:12])[CH2:10][CH3:9])[C:5]([O:4][CH2:1][CH3:2])=[O:16]
After a 500 mL reaction vessel which had been sufficiently dried inside by vacuum heating was replaced with dry nitrogen, and placed in an ice bath, 24.2 g (370 mmol/1.5 equivalent) of activated metal zinc and 300 mL of THF (dehydrated) were added into the reaction vessel. Thereto was added a bromofluoroethyl acetate/THF solution (46.91 g (253.6 mmol/1.0 equivalent) of bromofluoroethyl acetate and 80 mL of THF (dehydrated)) dropwise over 5 min. After the dropwise addition, the temperature of the mixture was elevated to the room temperature, followed by stirring for 20 min. Thereto was added a propionaldehyde/THF solution (17.76 g (305.8 mmol/1.2 equivalent) of propionaldehyde and 80 mL of THF (dehydrated)), and the mixture was stirred for 60 min at a room temperature. Thereafter, water and diisopropyl ether were added thereto, and two-layer separation was carried out. The organic layer thus obtained was washed with diluted hydrochloric acid and water, and the moisture was eliminated using anhydrous magnesium sulfate, followed by filtration. Then diisopropyl ether was distilled off to give 35.4 g (yield: 85%) of ethyl 2-fluoro-3-hydroxy-pentanoate represented by the following formula.
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