Deoxyuridine
Deoxyuridine (dU) is a compound and a nucleoside. It is similar in chemical structure to uridine, but without the 2'-hydroxyl group.
Idoxuridine and Trifluridine are variants of deoxyuridine used as antiviral drugs. They are similar enough to be incorporated as part of DNA replication, but they possess side groups on the uracil component (an iodine and a CF3 group, respectively), that prevent base pairing.