(2'R)-2'-Deoxy-3',5'-bis-O-[(1,1-dimethylethyl)dimethylsilyl]-2'-fluoro-2'-methyl-uridine is an intermediate in the synthesis of Sofosbuvir (R)-Phosphate (S675615), which is an impurity of PSI-7977 (P839640), a prodrug that is metabolized to the active antiviral agent 2'-deoxy-2'-α-fluoro-β-C-methyluridine-5'-monophosphate and is currently being investigated in phase 3 clinical trials for the treatment of hepatitis C. Studies have profiled PSI-7977 as a nucleotide inhibitor of hepatitis C virus, exerting selective inhibitory effects towards HCV NS5B polymerase.