2'-Deoxy-uridine 5'-(O-Phenyl Carbonothioate) is an intermediate in synthesizing 5’O,6-Cyclo-dihydro-2’,2’-difluoro-2’-deoxyuridine (C989920), which is an impurity (a product of degradation) of Gemcitabine Hydrochloride (G305000) which is an antineoplastic agent.