SFB C compound

SFB C compound is a Sofosbuvir-related API impurity arising from incomplete phosphorylation of the nucleoside core, retaining a terminal hydroxyl group at the uracil sugar moiety. Its structure features a 2'-deoxy-2'-α-fluoro-β-L-ribofuranosyl uracil scaffold with a truncated phosphate ester chain, lacking the methyl ester prodrug functionality. This impurity forms via side-chain cleavage during Sofosbuvir synthesis, resulting in a stable, non-oxidative degradation byproduct. It serves as a critical HPLC reference standard for quantifying process-related impurities in Sofosbuvir drug substance batches.