Br[C@@H:2]([CH:6]([CH3:8])[CH3:7])[C:3]([OH:5])=[O:4].[OH-].[K+].C1C=CC2C(C3C=CC(O)=CC=3)(C3C=CC(O)=CC=3)OC(=O)C=2C=1.[F:35][C:36]([F:45])([F:44])[C:37]1[CH:43]=[CH:42][C:40]([NH2:41])=[CH:39][CH:38]=1>CO>[F:35][C:36]([F:44])([F:45])[C:37]1[CH:38]=[CH:39][C:40]([NH:41][C@@H:2]([CH:6]([CH3:8])[CH3:7])[C:3]([OH:5])=[O:4])=[CH:42][CH:43]=11.5 Grams (8.3 mmol) of the (S)-2-bromo-3-methylbutanoic acid is titrated with 8 ml of 1 M potassium hydroxide in methanol to a phenolphthalein endpoint. The solution is evaporated under high vacuum at 40° for 1 hour, and 0.51 g (2.33 mmol) of the resulting salt is heated together with 1.52 g (9.43 mmol) of 4-trifluoromethylaniline at 90°-95° under nitrogen for 1 hour. Heating is discontinued and the reaction worked up immediately by partition between ether/5% sodium hydroxide. The layers are separated and the organic phase is extracted with 5% sodium hydroxide (2×). The aqueous layers are combined and washed with ether (2×), then acidified with ice and conc. HCl and extracted with ether (3×). The latter ether extracts are washed with brine, dried over magnesium sulfate, filtered and evaporated, giving (S)-2-(4-trifluoromethylphenylamino)-3-methylbutanoic acid.
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