(2S)-isopropyl 2-(((((2R,3R,4R,5R)-5-(2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)-4-fluoro-2-((((((S)-1-isopropoxy-1-oxopropan-2-yl)amino)(phenoxy)phosphoryl)oxy)methyl)-4-methyltetrahydrofuran-3-yl)oxy)(phenoxy)phosphoryl)amino)propanoate,(2S)-isopropyl 2-(((((2R,3R,4R,5R)-5-(2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)-4-fluoro-2-((((((S)-1-isopropoxy-1-oxopropan-2-yl)amino)(phenoxy)phosphoryl)oxy)methyl)-4-methyltetrahydrofuran-3-yl)oxy)(phenoxy)phosphoryl)amino)propanoate,"Sofosbuvir 3โ,5โ-Bis-(S)-phosphate is an impurity of PSI-7977, a prodrug that is metabolized to the active antiviral agent 2โ-deoxy-2โ-a-fluoro-ร-C-methyluridine-5โ-monophosphate and is currently being investigated in phase 3 clinical trials for the treat",Sofosbuvir Impurity