2-Amino-9-(2-hydroxyethyl)-1,9-dihydro-6H-purin-6-one; Hydroxyethyl guanine (USP) ; 9-(2-Hydroxyethyl)guanine; 2-Amino-1,9-dihydro-9-(2-hydroxyethyl)-6H-purin-6-one; 9-(2'-Hydroxyethyl)guanine; Guanine, 9-(2-hydroxyethyl); 2-Amino-9-(2-hydroxyethyl)-3H-purin-6-one; 9-(2′-Hydroxyethyl)guanine; Aciclovir Impurity P; Acyclovir Hydroxyethyl Guanine