6-Chloro-N4-[2-(phenylmethoxy)ethyl]-2,4-pyrimidinediamine is an intermediate used in the synthesis of 9-(2-Hydroxyethyl)guanine (H942035), which is an impurity of the antiviral agent Acyclovir (A192400). 9-(2-Hydroxyethyl)guanine is a nucleoside phosphotransferase acceptor.