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 2′-chloro nucleosides according to Formula 2001: or a pharmaceutically acceptable salt, solvate, stereoisomeric form, tautomeric form or polymorphic form thereof, wherein B, Z and PD are as described herein.