A compound of Formula wherein R 1a and R 1b are each independently C 1-6 alkyl optionally substituted with from 1 to 5 R 20 groups; R 2a and R 2b are each independently H or halo; R 3 is -C OR a, -NHC OR a, -NHS 2 R a, or -S 2 NR a R b; or selected from the group consisting of C 1-10 alkyl, C 1-10 alkoxy, amino, C 5-10 aryl, C 6-20 arylalkyl, C 1-10 heteroalkyl, C 5-10 heteroaryl, and C 6-20 heteroarylalkyl, each of which is optionally substituted with from 1 to 5 R 20 groups; one of R 4a and R 4b is selected from the group consisting of H and C 1-6 alkyl optionally substituted with from 1 to 5 R 20 groups, and the other is absent; R 5 is -C OR a, -NHC OR a, -NHS 2 R a, or -S 2 NR a R b; or selected from the group consisting of H, C 1-10 alkyl, C 1-10 haloalkyl, C 1-10 alkoxy, amino, C 5-10 aryl, C 6-20 arylalkyl, C 1-10 heteroalkyl, C 5-10 heteroaryl, and C 6-20 heteroarylalkyl, each of which is optionally substituted with from 1 to 5 R 20 groups; each R a and R b is independently selected from the group consisting of H, C 1-10 alkyl, C 5-10 aryl, C 6-20 arylalkyl, C 1-10 heteroalkyl, C 5-10 heteroaryl, and C 6-20 heteroarylalkyl, each of which is optionally substituted with from 1 to 5 R 20 groups; and each R 20 is independently selected from the group consisting of acyl, C 1-10 alkyl, C 1-10 alkoxy, amino, amido, amidino, C 5-10 aryl, C 6-20 arylalkyl, azido, carbamoyl, carboxyl, carboxyl ester, cyano, guanidino, halo, C 1-10 haloalkyl, C 1-10 heteroalkyl, C 5-10 heteroaryl, C 6-20 heteroarylalkyl, hydroxy, hydrazino, imino, oxo, nitro, sulfinyl, sulfonic acid, sulfonyl, thiocyanate, thiol, and thione; wherein the C 1-10 alkyl, C 5-10 aryl, C 6-20 arylalkyl, C 1-10 heteroalkyl, C 5-10 heteroaryl, and C 6-20 heteroarylalkyl groups are optionally substituted with from 1 to 3 substituents independently selected from C 1-6 alkyl, C 5-10 aryl, halo, C 1-6 haloalkyl, cyano, hydroxyl, and C 1-6 alkoxy; or a pharmaceutically acceptable salt thereof. R 1a and R 1b are each independently C 1-6 alkyl optionally substituted with from 1 to 5 R 20 groups; R 2a and R 2b are each independently H or halo; R 3 is -C OR a, -NHC OR a, -NHS 2 R a, or -S 2 NR a R b; or selected from the group consisting of C 1-10 alkyl, C 1-10 alkoxy, amino, C 5-10 aryl, C 6-20 arylalkyl, C 1-10 heteroalkyl, C 5-10 heteroaryl, and C 6-20 heteroarylalkyl, each of which is optionally substituted with from 1 to 5 R 20 groups; one of R 4a and R 4b is selected from the group consisting of H and C 1-6 alkyl optionally substituted with from 1 to 5 R 20 groups, and the other is absent; R 5 is -C OR a, -NHC OR a, -NHS 2 R a, or -S 2 NR a R b; or selected from the group consisting of H, C 1-10 alkyl, C 1-10 haloalkyl, C 1-10 alkoxy, amino, C 5-10 aryl, C 6-20 arylalkyl, C 1-10 heteroalkyl, C 5-10 heteroaryl, and C 6-20 heteroarylalkyl, each of which is optionally substituted with from 1 to 5 R 20 groups; each R a and R b is independently selected from the group consisting of H, C 1-10 alkyl, C 5-10 aryl, C 6-20 arylalkyl, C 1-10 heteroalkyl, C 5-10 heteroaryl, and C 6-20 heteroarylalkyl, each of which is optionally substituted with from 1 to 5 R 20 groups; and each R 20 is independently selected from the group consisting of acyl, C 1-10 alkyl, C 1-10 alkoxy, amino, amido, amidino, C 5-10 aryl, C 6-20 arylalkyl, azido, carbamoyl, carboxyl, carboxyl ester, cyano, guanidino, halo, C 1-10 haloalkyl, C 1-10 heteroalkyl, C 5-10 heteroaryl, C 6-20 heteroarylalkyl, hydroxy, hydrazino, imino, oxo, nitro, sulfinyl, sulfonic acid, sulfonyl, thiocyanate, thiol, and thione; wherein the C 1-10 alkyl, C 5-10 aryl, C 6-20 arylalkyl, C 1-10 heteroalkyl, C 5-10 heteroaryl, and C 6-20 heteroarylalkyl groups are optionally substituted with from 1 to 3 substituents independently selected from C 1-6 alkyl, C 5-10 aryl, halo, C 1-6 haloalkyl, cyano, hydroxyl, and C 1-6 alkoxy;