[Cl:1][C:2]1[CH:7]=[CH:6][C:5]([CH:8]([CH3:21])[C:9]([NH:11][C:12]([CH3:20])([CH:17]([CH3:19])[CH3:18])[C:13]([O:15]C)=[O:14])=[O:10])=[CH:4][CH:3]=1.[OH-].[Na+].Cl>CS(C)=O>[Cl:1][C:2]1[CH:7]=[CH:6][C:5]([CH:8]([CH3:21])[C:9]([NH:11][C:12]([CH3:20])([CH:17]([CH3:18])[CH3:19])[C:13]([OH:15])=[O:14])=[O:10])=[CH:4][CH:3]=10.7 g (2.24 mmol) of methyl 2-[2-(4-chlorophenyl)propanoylamino]-2,3-dimethylbutanoate was dissolved in 20 ml of dimethyl sulfoxide. To the solution was dropwise added, at room temperature with stirring, 5 ml (2.87 mmol) of a 23% sodium hydroxide aqueous solution, and a reaction was allowed to take place at room temperature for 1 hour. Part of the reaction mixture was taken by weighing, acidified (pH=2) with diluted hydrochloric acid, and subjected to extraction with ethyl acetate, after which the extract was analyzed by GC. It was confirmed that the total amount of the methyl 2-[2-(4-chlorophenyl)propanoylamino]-2,3-dimethylbutanoate was converted into 2-(4-chlorophenyl)-N-(1-hydroxycarbonyl-1,2-dimethylpropyl)propionamide. 100 ml of water was added and the mixture was allowed to have a pH of 2 with diluted hydrochloric acid. Extraction was made twice using 100 ml of ethyl acetate. The two organic layers were combined, washed with 50 ml of water, and washed with a saturated aqueous sodium chloride solution. The organic layer obtained was concentrated to obtain 0.5 g (1.7 mmol) (yield=75%) of 2-[2-(4-chlorophenyl)propanoylamino]-2,3-dimethylbutanoic acid.
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