9H-Purin-6-amine; 6-Aminopurine; 1H-Purin-6-amine; 1,6-Dihydro-6-iminopurine (USP); Mercaptopurine Monohydrate - Impurity B; Mercaptopurine - Impurity B; Adenosine - Impurity A; 7H-purin-6-amine