B(F)(F)F.[C:5](O)(=[O:7])[CH3:6].[O:9]([C@H:16]([CH3:21])[C:17]([O:19][CH3:20])=[O:18])[C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1.C([O-])(=O)C.[Na+]>>[C:5]([C:13]1[CH:14]=[CH:15][C:10]([O:9][C@H:16]([CH3:21])[C:17]([O:19][CH3:20])=[O:18])=[CH:11][CH:12]=1)(=[O:7])[CH3:6]67 g (1 mol) of boron trifluoride were passed into 60 g (1 mol) of acetic acid. The mixture was heated to 45°-50° C., and 36 g (0.2 mol) of methyl (R)-2-phenoxypropionate were added. After stirring at 45°-50° C. for 7 hours, the temperature was raised to 80° C. for 1 h and the mixture was then stirred into 800 ml of 25% by weight aqueous sodium acetate solution. The product was extracted with 200 ml of ethyl acetate and, after concentration of the organic phase, purified by vacuum distillation. Yield: 83.7% (94-95% enantiomeric excess).
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