Sofosbuvir impurity 9/O-Desphenyl Sofosbuvir/isopropyl ((((2R,3R,4R,5R)-5-(2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)-4-fluoro-3-hydroxy-4-methyltetrahydrofuran-2-yl)methoxy)(hydroxy)phosphoryl)-L-alaninate Sofosbuvir metabolites Sofosbuvir IMP N-[(2'R)-2'-Deoxy-2'-fluoro-2'-methyl-5'-uridylyl]-1-(1-methylethyl) Ester L-Alanine O-Desphenyl Sofosbuvir Sofosbuvir O-Desphenyl Impurity L-Alanine, N-[(2'R)-2'-deoxy-2'-fluoro-2'-methyl-5'-uridylyl]-, 1-(1-methylethyl) ester