Ethyl (2S,3R)-3-[(4R)-2,2-dimethyl-1,3-dioxolan-4- yl]-2,3-dihydroxy-2-methylpropanoate

Ethyl (2S,3R)-3-[(4R)-2,2-dimethyl-1,3-dioxolan-4-yl]-2,3-dihydroxy-2-methylpropanoate is a stereoisomerically defined ester derivative featuring a 1,3-dioxolane ring substituted at C4 with a 2,2-dimethyl group. The molecule incorporates adjacent 2S,3R-configured diol centers linked to a methylated propanoate ester. This compound arises as a stereoisomeric impurity during the synthesis of Sofosbuvir, differing from the parent drug by the (4R) configuration of the dioxolane ring and the ethyl ester functionality. It serves as a critical HPLC reference standard for chiral purity analysis in Sofosbuvir manufacturing.