azathioprine crystalline; 6-(1-methyl-4-nitroimidazol-5-ylthio)purine; azathioprine; 6-[(1-methyl-4-nitro-1h-imidazol-5-yl)thio]-1h-purine; 6-((1-methyl-4-nitroimidazol-5-yl)thio)purine; 6-(methyl-p-nitro-5-imidazolyl)-thiopurine; Azathiopurine; 6-[(1-methyl-4-nitro-1H-imidazol-5-yl)sulfanyl]-7H-purine; 6-[(1-methyl-4-nitro-1H-imidazol-5-yl)sulfanyl]-5H-purine