An amount 2.0 g of trichloromethyl chloroformate (TCF) was dissolved in 30 ml of toluene and cooled to 5° C. or lower. To the solution was added dropwise a solution of 5.0 g of 5-chloro-N-{2-[4-(2-ethoxyethyl)2-methylphenoxy]ethyl}-6-methyl-4-pyrimidine amine and 1.8 g of triethylamine dissolved in 20 ml of toluene, and after the dropwise addition, the mixture was stirred at room temperature for 3 hours. After completion of the reaction, 20 ml of water was added, and the mixture was stirred at room temperature for one hour to decompose excessive TCF.
