The effective synthesis of the azathioprine analogs - 2-subsituted derivatives of 7-methyl-6-(1-methyl-4-nitroimidazol-5-ylthio)purines 5 has been achieved by the reaction of 2-subsituted 6-purinethiones 4 with 5-chloro-l-methyl-4-nitroimidazole in ethano