5-Iodo-2',3'-dideoxycytidine is a synthetic nucleoside analogue characterized by the replacement of the hydroxyl groups at the 2' and 3' positions of the ribose sugar with hydrogen atoms (dideoxy) and the substitution of an iodine atom at the 5-position of the cytosine base. This structural modification renders it a chain terminator during DNA synthesis, as it lacks the 3'-OH group necessary for phosphodiester bond formation. Its primary application is in biochemical and virological research, particularly as a potent inhibitor of reverse transcriptase. It has been studied for its activity against retroviruses, including HIV-1. The compound serves as a key intermediate or precursor in the synthesis of more complex antiviral nucleoside analogues and probes for studying nucleic acid metabolism and enzyme mechanisms. As a modified nucleoside, it is a specialized building block for drug discovery rather than a general-purpose synthetic reagent. Its handling requires caution in a laboratory setting due to its potential biological activity.