2-Amino-9-[[[2-hydroxy-1-(hydroxymethyl)ethoxy]methoxy]methyl]-1,9-dihydro-6H-purin-6-one;2-Amino-9-((((1,3-dihydroxypropan-2-yl)oxy)methoxy)methyl)-1H-purin-6(9H)-one;Ganciclovir Dimether Impurity;