1,4-Dioxane hydrochloride → N-[4-({[2-(acetylamino)-1,3-thiazol-4-yl]methyl}amino)benzyl]hydrazinecarboxamide dihydrochloride

To a suspension of tert-butyl 2-{[4-({[2-(acetylamino)-1,3-thiazol-4-yl]methyl}amino)benzoyl]carbamoyl}hydrazinecarboxylate (306.2 mg, 0.705 mmol) in anhydrous dichloromethane (7 ml) was added 4M hydrogen chloride dioxane solution (7.0 ml, 28.0 mmol). The mixture was stirred at room temperature for 2 hr, and concentrated under reduced pressure. Ethyl acetate was added to the residue, and the mixture was concentrated again under reduced pressure. This operation was repeated 3 times to remove hydrogen chloride azeotropically. The residue was suspended in ethyl acetate, and the suspension was filtered, washed twice with ethyl acetate, and dried under reduced pressure. The residue was recrystallized by dissolving in methanol (3.6 ml) and then addition of ethyl acetate (12 ml). The crystals were collected by filtration, and dried under reduced pressure to give the title compound (272.8 mg, 0.670 mmol, yield 95.0%) as a white solid.