Provided herein are compounds, compositions and methods for the treatment of Flaviviridae infections, including HCV infections. In certain embodiments, compounds and compositions of nucleoside derivatives are disclosed, which can be administered either alone or in combination with other anti-viral agents. In certain embodiments, the compounds are 3′-deoxy nucleoside compounds according to Formula 3001a or 3001b: or a pharmaceutically acceptable salts, solvates, stereoisomeric forms, tautomeric forms, or polymorphic forms thereof, wherein PD, Base1 and Base2 are as provided herein.