1-hydroxybenzotriazole (22.91 g, 149.6 mmol), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (WSC) (28.68 g, 149.6 mmol), N,O-dimethylhydroxylamine hydrochloride (13.93 g, 136 mmol) and triethylamine (41.7 ml, 299.2 mmol) were added to a solution (1.0 l) of 3-[2-(3,4-diethoxyphenyl)thiazole-4-yl]propionic acid (43.71 g, 136 mmol) in dichloromethane, followed by stirring at room temperature for 4 hours. Water was added to separate the reaction mixture into layers, and the aqueous layer was further subjected to extraction with dichloromethane. The organic layer was dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure, and the residue was purified by silica gel column chromatography (eluent: ethyl acetate/n-hexane=1/3). The solvent was distilled off under reduced pressure, and the residue was recrystallized from an ethyl acetate/n-hexane mixed solvent, to thereby obtain 42.4 g (yield: 68%) of 3-[2-(3,4-diethoxyphenyl)thiazole-4-yl]-N-methoxy-N-methylpropionamide as colorless prisms.
