A compound of Formula (I), wherein: X is hydrogen, C 1-6 alkyl, halogen, N 3 , OH, CN or SH, and is preferably hydrogen or halogen; Y is oxygen or sulfur, and is preferably oxygen; R 1 , R 2 , R 6 , and R 7 are each independently selected from the group consisting of hydrogen, optionally substituted C 1-10 alkyl, optionally substituted cycloalkyl, optionally substituted aryl, optionally substituted heterocyclyl, and optionally substituted heteroaryl, wherein R 2 and R 6 can be connected to form a 3-8 membered carbocyclic ring which may contain 0-3 heteroatoms selected from N, O, and S, and may be a saturated, unsaturated, or aromatic ring; R 3 is selected from the group consisting of optionally substituted aryl and optionally substituted heteroaryl, and is preferably optionally substituted aryl; R 4 is selected from the group consisting of hydrogen, and optionally substituted C 1-10 acyl, and is preferably hydrogen; Q is a purine base having the following structure: and Z is hydrogen, optionally substituted C 1-10 alkyl or halogen; the above expression "optionally substituted" means unsubstituted or substituted with one or more substituents selected from the group consisting of halogen, alkyl, amino, alkylamino, alkoxy, haloalkyl, haloalkoxy, hydroxy, hydroxyalkyl, alkoxyalkyl, amido, sulfonamido, cyano, nitro, nitroso, azido, aldehyde, alkenyl, alkynyl, cycloalkyl, aryl, aralkyl, aryloxy, heteroaryl, heteroaryloxy, acyl, carboxyl, alkylcarbonyl, arylcarbonyl, heteroarylcarbonyl, and carboxylate; and the substituents can be connected to each other to form a 3-8 membered saturated, unsaturated or aromatic ring containing 0-3 heteroatoms selected from N, O, and S; or a pharmaceutically acceptable salt, ester thereof, or any crystalline form thereof, or a mixture thereof. X is hydrogen, C 1-6 alkyl, halogen, N 3 , OH, CN or SH, and is preferably hydrogen or halogen; Y is oxygen or sulfur, and is preferably oxygen; R 1 , R 2 , R 6 , and R 7 are each independently selected from the group consisting of hydrogen, optionally substituted C 1-10 alkyl, optionally substituted cycloalkyl, optionally substituted aryl, optionally substituted heterocyclyl, and optionally substituted heteroaryl, wherein R 2 and R 6 can be connected to form a 3-8 membered carbocyclic ring which may contain 0-3 heteroatoms selected from N, O, and S, and may be a saturated, unsaturated, or aromatic ring; R 3 is selected from the group consisting of optionally substituted aryl and optionally substituted heteroaryl, and is preferably optionally substituted aryl; R 4 is selected from the group consisting of hydrogen, and optionally substituted C 1-10 acyl, and is preferably hydrogen; Q is a purine base having the following structure: and Z is hydrogen, optionally substituted C 1-10 alkyl or halogen; the above expression "optionally substituted" means unsubstituted or substituted with one or more substituents selected from the group consisting of halogen, alkyl, amino, alkylamino, alkoxy, haloalkyl, haloalkoxy, hydroxy, hydroxyalkyl, alkoxyalkyl, amido, sulfonamido, cyano, nitro, nitroso, azido, aldehyde, alkenyl, alkynyl, cycloalkyl, aryl, aralkyl, aryloxy, heteroaryl, heteroaryloxy, acyl, carboxyl, alkylcarbonyl, arylcarbonyl, heteroarylcarbonyl, and carboxylate; and the substituents can be connected to each other to form a 3-8 membered saturated, unsaturated or aromatic ring containing 0-3 heteroatoms selected from N, O, and S; or a pharmaceutically acceptable salt, ester thereof, or any crystalline form thereof, or a mixture thereof. <EOS>