Sofosbuvir sofosBuvir impurity 47 sofosBuvir impurity 41 Sofosbuvir Impurity 5 Sofosbuvir Impurity 57 SofosBuvir Impurity 56 SofosBuvir Impurity 50 sofosBuvir Impurity 34 Sofosbuvir impurity J Sofosbuvir Impurity 60 SofosBuvir Impurity 53 sofosBuvir Impurity 37 Sofosbuvir Impurity 9 L-Alanine, N-[(S)-hydroxyphenoxyphosphinyl]-, 1-Methylethyl ester, (P→3'),(P'→5')-diester with (2'R)-2'-deoxy-2'-fluoro-2'-Methyluridine SofosBuvir impurity 63 Sofosbuvir IMpurity 4 SofosBuvir Impurity 55 sofosBuvir impurity 49