[F:1][C:2]([F:18])([F:17])[CH2:3][CH:4]([CH3:16])[C:5]([NH:7][C@H:8]([C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1)[CH3:9])=[O:6].CC(C)([O-])C.[K+].O.C1(C)C=CC=CC=1>O1CCCC1>[F:1][C:2]([F:17])([F:18])[CH2:3][C@@H:4]([CH3:16])[C:5]([NH:7][C@H:8]([C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1)[CH3:9])=[O:6]
10 g of 4,4,4-trifluoro-2-methyl-N-[(S)-1-phenylethyl]butyramide (diastereomer ratio 2(S):1(R), prepared by a method similar to that described in step c)above) was dissolved in tetrahydrofuran (25 ml) with stirring. Potassium t-butoxide (2.02 g) was then added, together with tetrahydrofuran (5 ml). The resultant solution was then stirred for one hour, by which time complete equilibration of the diastereomers had occured, as monitored by HPLC analysis. Water was then added with cooling to maintain the temperature at 20°-25° C. The solution was then stirred for 10 minutes, and then toluene (25 ml) was added, and the stirring was continued for a further 15 minutes. The organic layer was then separated, washed with water (12.5 ml) and concentrated by distillation at atmospheric pressure to a temperature of 110° C. The volume was adjusted to 80 ml by adding toluene, and the mixture heated under reflux. Petroleum ether (b.p. 100°-120° C.) (80 ml) was then added. The solution was then allowed to cool to 40° C., seeded with (R)-4,4,4-trifluoro-2-methyl-N-[(S)-1-phenylethyl]butyramide and held at 40° C. for 2 hours. The mixture was then allowed to cool to 30° C., and was stirred overnight. The crystalline product was then filtered off, washed with petroleum ether (b.p. 100°-120° C.) and dried at 65° C. to afford 3.20 g (32%) of (R)-4,4,4-trifluoro-2-methyl-N-[(S)-1-phenylethyl]butyramide contaminated with about 6% of the undesired (S) diastereomer. ##STR2##
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