[Cl:1][C:2]1[CH:7]=[CH:6][C:5]([CH:8]([CH3:20])[C:9]([NH:11][C:12]([CH3:19])([CH:16]([CH3:18])[CH3:17])[C:13]([OH:15])=[O:14])=O)=[CH:4][CH:3]=1.C(OC(=O)C)(=O)C.O>C1(C)C=CC=CC=1>[Cl:1][C:2]1[CH:7]=[CH:6][C:5]([CH:8]([C:9]2[O:14][C:13](=[O:15])[C:12]([CH:16]([CH3:18])[CH3:17])([CH3:19])[N:11]=2)[CH3:20])=[CH:4][CH:3]=13.7 g (12.5 mmol) of 2-[2-(4-chlorophenyl)-propanoylamino]-2,3-dimethylbutanoic acid was suspended in 50 ml of toluene. Thereto was added 2 g (19.6 mmol) of acetic anhydride. The mixture was refluxed with heating, to give rise to a reaction. The reaction was complete in 20 minutes. The reaction mixture was cooled to room temperature. 50 ml of water was added and phase separation was allowed to take place. The separated organic layer was washed with 30 ml of water and 30 ml of a saturated aqueous sodium bicarbonate solution, and then concentrated to obtain 3.2 g (yield=97%) of 2-[1-(4-chlorophenyl)ethyl]-4-isopropyl-4-methyl-1,3-oxazol-5-one.
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