Antiviral compounds and methods of making and using the same

A compound of Formula I:

• or a pharmaceutically acceptable salt thereof, wherein:
• R1 is OH;
• R2 is OH;
• R3 is C(O)R7;
• R7 is C1-C8alkyl, C3-C8 carbocyclyl, C6-C10 aryl, 4 to 6 membered heterocyclyl containing 1, 2, or 3 O, or 5 to 6 membered heteroaryl containing 1, 2, or 3 heteroatoms selected from N, O, and S;
• wherein the alkyl, carbocyclyl, aryl, heterocyclyl, and heteroaryl of R7 are each, independently, optionally substituted with one, two or three substituents independently selected from the group consisting of halo, oxo, cyano, —N3, —OR8, C1-C8 alkyl, —NR9R10, C3-C8 carbocyclyl optionally substituted with C1-C6 alkyl, and phenyl optionally substituted with one, two, or three substituents independently selected from halo, cyano, and C1-C6 alkyl;
• and
• each R8 is independently H, C1-C6 alkyl, C1-C6 haloalkyl, and C3-C6 cycloalkyl;
• each R9 is independently H, C1-C6 alkyl, C1-C6 haloalkyl, and C3-C6 cycloalkyl;
• each R10 is independently H, C1-C6 alkyl, C1-C6 haloalkyl, and C3-C6 cycloalkyl;
• and
• Base is
• wherein
• R11 is C1-C6 alkyl substituted with —OP(O)(OH)2 or —OC(O)R12;
• R12 is C1-C8 alkyl;
• and
• R13 is C1-C6 alkyl substituted with —OP(O)(OH)2 or —OC(O)R12.