A compound of formula I: or a pharmaceutically acceptable salt, solvate, hydrate, tautomer, or stereoisomer thereof, wherein: L 1 is straight or branched C 1 -C 5 alkyl unsubstituted or substituted with one or more substituents selected from the group consisting of OR 10, NH 2, NHR 10, and N(R 10)(R 10 ') provided that no more than one oxygen or nitrogen is attached to any carbon; or L 1 is selected from the group consisting of -C -C 1 -C 3 alkylenyl-, -S 2 -, -S 2 NH-, - C NH-, and -C NR 10 -; each R 10 and R 10 ' is independently selected from the group consisting of H; C 1 -C 6 alkyl unsubstituted or substituted with one or more substituents selected from the group consisting of OH, O-C 1 -C 5 alkyl, OPO 3 -2 M 2, OP 2, OC -C 1 -C 6 alkyl, and OC O-C 1 -C 6 alkyl where M is a monovalent metal cation; and C 3 -C 18 cycloalkyl unsubstituted or substituted with one or more substituents selected from the group consisting of OH and O-C 1 -C 5 alkyl provided that no more than one oxygen is attached to any carbon; or R 10 and R 10 ', together with the nitrogen to which they are attached, may form a heterocycle; R 1 is C 3 -C 18 cycloalkyl, aryl, or heteroaryl, any of which is unsubstituted or substituted with one or more substituents selected from the group consisting of OH, CN, halogen, -Ci-C 6 alkylaryl, -O-C 1 -C 6 alkylaryl, O-R 10, OPO 3 -2 M 2, OP 2, SH, S-R 10, C 1 -C 5 alkyl, branched C 1 -C 6 alkyl, NH 2, NHR 10, NHS 2 R 10, N(R 10)(R 10 '), and NHCOR 10 where M is a monovalent metal cation; X is selected from O, S, -S -, and -S 2 -; Y and Y' are independently H, halogen, or C 1 -C 5 alkyl; L 2 is a bond; R 2 is phenyl unsubstituted or substituted with one or more substituents selected from the group consisting of halogen, OH, OR 10, CN, NH 2, NHR 10, N(R 10)(R 10 '), SH, SR 10, SOR 10, SO 2 R 10, SO 2 NHR 10, SO 2 N(R 10)(R 10 '), CONH 2, CONR 10, CON(R 10)(R 10 '); and wherein aryl is a cyclic, aromatic hydrocarbon group with 1 or 2 aromatic rings; and wherein heteroaryl is a monocyclic, bicyclic or polycyclic aromatic radical of 5 to 10 ring atoms and containing one or more ring heteroatoms selected from N, O, or S, the remaining ring atoms being C. L 1 is straight or branched C 1 -C 5 alkyl unsubstituted or substituted with one or more substituents selected from the group consisting of OR 10, NH 2, NHR 10, and N(R 10)(R 10 ') provided that no more than one oxygen or nitrogen is attached to any carbon; or L 1 is selected from the group consisting of -C -C 1 -C 3 alkylenyl-, -S 2 -, -S 2 NH-, - C NH-, and -C NR 10 -; each R 10 and R 10 ' is independently selected from the group consisting of H; C 1 -C 6 alkyl unsubstituted or substituted with one or more substituents selected from the group consisting of OH, O-C 1 -C 5 alkyl, OPO 3 -2 M 2, OP 2, OC -C 1 -C 6 alkyl, and OC O-C 1 -C 6 alkyl where M is a monovalent metal cation; and C 3 -C 18 cycloalkyl unsubstituted or substituted with one or more substituents selected from the group consisting of OH and O-C 1 -C 5 alkyl provided that no more than one oxygen is attached to any carbon; or R 10 and R 10 ', together with the nitrogen to which they are attached, may form a heterocycle; R 1 is C 3 -C 18 cycloalkyl, aryl, or heteroaryl, any of which is unsubstituted or substituted with one or more substituents selected from the group consisting of OH, CN, halogen, -Ci-C 6 alkylaryl, -O-C 1 -C 6 alkylaryl, O-R 10, OPO 3 -2 M 2, OP 2, SH, S-R 10, C 1 -C 5 alkyl, branched C 1 -C 6 alkyl, NH 2, NHR 10, NHS 2 R 10, N(R 10)(R 10 '), and NHCOR 10 where M is a monovalent metal cation; X is selected from O, S, -S -, and -S 2 -; Y and Y' are independently H, halogen, or C 1 -C 5 alkyl; L 2 is a bond; R 2 is phenyl unsubstituted or substituted with one or more substituents selected from the group consisting of halogen, OH, OR 10, CN, NH 2, NHR 10, N(R 10)(R 10 '), SH, SR 10, SOR 10, SO 2 R 10, SO 2 NHR 10, SO 2 N(R 10)(R 10 '), CONH 2, CONR 10, CON(R 10)(R 10 '); and wherein aryl is a cyclic, aromatic hydrocarbon group with 1 or 2 aromatic rings; and wherein heteroaryl is a monocyclic, bicyclic or polycyclic aromatic radical of 5 to 10 ring atoms and containing one or more ring heteroatoms selected from N, O, or S, the remaining ring atoms being C.