<unk>  is a thiopurine linked to a second heterocycle (an imidazole derivative) via a thioether. It is a pale yellow solid with a slightly bitter taste and a melting point of 238–245 °C. It is practically insoluble in water and only slightly soluble in lipophilic solvents such as chloroform, ethanol, and diethylether. It dissolves in alkaline aqueous solutions, where it hydrolyzes to 6-mercaptopurine.<unk>  is synthesized from 5-chloro-1-methyl-4-nitro-1H-imidazole and 6-mercaptopurine in dimethyl sulfoxide. The synthesis of the former starts with an amide from methylamine and diethyl oxalate, which is then cyclized and chlorinated with phosphorus pentachloride; the nitro group is introduced with nitric and sulfuric acid. The whole process of<unk>  synthesis
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