Used as an intermediate in the synthesis of antiviral medications, particularly nucleoside analogs targeting RNA viruses such as those causing HIV and hepatitis B. The ethyl carbonate moiety at the 3'-position acts as a protecting group during synthesis or in prodrug formulations to enhance solubility and bioavailability. Upon metabolic hydrolysis, it releases the parent nucleoside (a thymidine analog), which is subsequently phosphorylated intracellularly to the active 5'-triphosphate form, inhibiting viral replication.