[F:1][C:2]1[CH:7]=[C:6]([F:8])[CH:5]=[CH:4][C:3]=1[C:9]1([O:18][CH2:17]1)[CH:10]([F:16])[C:11]([O:13][CH2:14][CH3:15])=[O:12].[NH:19]1[CH:23]=[N:22][CH:21]=[N:20]1.C(OCC)(=O)C>O>[F:1][C:2]1[CH:7]=[C:6]([F:8])[CH:5]=[CH:4][C:3]=1[C:9]([OH:18])([CH2:17][N:19]1[CH:23]=[N:22][CH:21]=[N:20]1)[CH:10]([F:16])[C:11]([O:13][CH2:14][CH3:15])=[O:12]A mixture of 2.4 g of ethyl 3-(2,4-difluorophenyl)-3,4-epoxy-2-fluorobutyrate (a mixture of diastereomers) and 6.4 g of 1,2,4-triazole was subjected to reaction at 90°-100° C. for 8 hours. To the reaction mixture were then added 10 ml of ethyl acetate and 5 ml of water. The organic layer was separated, washed with a saturated aqueous sodium chloride solution, and then dried over anhydrous magnesium sulfate. The solvent was removed by distillation under reduced pressure. The residue obtained was purified by a column chromatography (eluant: chloroform/methanol=20/1) to obtain 650 mg of ethyl 3-(2,4-difluorophenyl)-2-fluoro-3-hydroxy-4-(1H-1,2,4-triazol-1-yl)butyrate (one of the diastereomers).
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