Nucleoside derivatives and methods of use thereof

A compound of Formula I

• or a pharmaceutically acceptable salt thereof,
• wherein R1 or R2 is independently H, heteroaryl, —(CO)C1-C6 alkyl, —(CO)OC1-C6 alkyl, —(CO)C5-C10 aryl, —(CO)C5-C10 heteroaryl, —(CO)OC5-C10 aryl, —(CO)OC5-C10 heteroaryl, —(CO)NHC1-C6 alkyl, (CO)NHC5-C10 aryl, or (CO)NHC5-C10 heteroaryl, wherein the heteroaryl, —(CO)C1-C6 alkyl, —(CO)OC1-C6alkyl, —(CO)C5-C10 aryl, —(CO)C5-C10 heteroaryl, —(CO)OC5-C10 aryl, —(CO)OC5-C10 heteroaryl, —(CO)NHC1-C6 alkyl, (CO)NHC5-C10 aryl or (CO)NHC5-C10 heteroaryl is optionally substituted with one or more substituents each independently selected from the group consisting of halo, OH, —O—C1-C6 alkyl, NRR5, C1-C6 alkyl, C5-C10 aryl and heteroaryl,
• wherein R3 or R4 is independently H, D, halo or C1-C3 alkyl, wherein alkyl is optionally substituted with one or more halo.
• wherein R5 or R6 is independently H, OH, C1-C6 alkyl, —(CO)C1-C6 alkyl, —(CO)OC1-C6 alkyl, —(CO)C5-C10 aryl, —(CO)C5-C10 heteroaryl, C5-C10 aryl or C5-C10 heteroaryl,
• wherein the link is independently selected from
• wherein each R, and R5 is independently selected from H and C1-C6 alkyl and wherein R7 and R8 can fuse to each other to form a ring.