A ketone compound (217 mg) was prepared in substantially the same manner as in step b) of Synthesis Example 1, except that 398 mg of 7-[(pyrimidin-5-yl)hydroxymethyl]imidazo[5,1-b]thiazole and 400 mg of manganese dioxide were used as the starting compounds. 7-(Pyrimidin-5-yl)carbonyl-2-(tri-n-butylstannyl)-imidazo[5,1-b]thiazole (68 mg) was prepared in substantially the same manner as in step c) of Synthesis Example 1, except that 46 mg of the ketone compound, 0.124 ml of tri-n-butylstannyl chloride, and 0.900 ml of a 1.0 N lithium bis(trimethylsilyl)amide/THF solution were used as the starting materials.
