A compound of Formula I': or a pharmaceutically acceptable salt thereof, wherein: R 1 is H, C 1-7 alkyl, hydroxy, C 1-7 alkoxy, halogen, -SH, -S-C 1-7 alkyl or NR a R b; R 2 for each occurence, is independently C 1-7 alkyl, halo, NO 2, CN, C 1-7 alkanoylamino, C 3-7 cycloalkyl, hydroxy, C 1-7 alkoxy, haloC 1-7 alkyl, -NR a R b, C 6-10 aryl, heteroaryl or heterocyclyl; wherein R a and R b for each occurrence are independently H or C 1-7 alkyl; R 3 is A 1 -C X 1; R 5 is H, halo, hydroxy, C 1-7 alkoxy, halo, C 1-7 alkyl or halo-C 1-7 akyl; and X and X 1 are independently OH, -O-C 1-7 alkyl, -NR a R b, -NHS 2 -C 1-7 alkyl, -NHS 2 -benzyl or -O- C 6-10 aryl; wherein alkyl is optionally substituted with one or more substituents independently selected from the group consisting of C 6-10 aryl, heteroaryl, heterocyclyl, C NH 2, C NH- C 1-6 alkyl, and C N(C 1-6 alkyl) 2; B 1 is -C NH- or -NHC -; A 1 is a bond; or A 1 is a phenyl or a heteroaryl; each of which is optionally substituted with one or more substituents independently selected from the group consisting of C 1-7 alkyl, C 3-7 cycloalkyl, halo-C 1-7 alkyl, hydroxy, C 1-7 alkoxy, halo, -NR a R b, -OCH 2 CO 2 H, and -OCH 2 C NH 2; or A 1 is a C 3-7 cycloalkyl; A 1 is -C 1-4 alkylene-C 6-10 -aryl-, -C 1-4 alkylene-heteroaryl- or -C 1-4 alkylene-heterocyclyl-, wherein A 1 may be in either direction; and n is 0, 1, 2, 3, 4 or 5; wherein each heteroaryl is a monocyclic or bicyclic aromatic ring comprising 5-10 ring atoms selected from carbon atoms and 1 to 5 heteroatoms, and each heterocyclyl is a monocyclic saturated or partially saturated but non-aromatic moiety comprising 4-7 ring atoms selected from carbon atoms and 1-5 heteroatoms, wherein each heteroatom of a heteroaryl or a heterocyclyl is independently selected from O, N and S. R 1 is H, C 1-7 alkyl, hydroxy, C 1-7 alkoxy, halogen, -SH, -S-C 1-7 alkyl or NR a R b; R 2 for each occurence, is independently C 1-7 alkyl, halo, NO 2, CN, C 1-7 alkanoylamino, C 3-7 cycloalkyl, hydroxy, C 1-7 alkoxy, haloC 1-7 alkyl, -NR a R b, C 6-10 aryl, heteroaryl or heterocyclyl; wherein R a and R b for each occurrence are independently H or C 1-7 alkyl; R 3 is A 1 -C X 1; R 5 is H, halo, hydroxy, C 1-7 alkoxy, halo, C 1-7 alkyl or halo-C 1-7 akyl; and X and X 1 are independently OH, -O-C 1-7 alkyl, -NR a R b, -NHS 2 -C 1-7 alkyl, -NHS 2 -benzyl or -O- C 6-10 aryl; wherein alkyl is optionally substituted with one or more substituents independently selected from the group consisting of C 6-10 aryl, heteroaryl, heterocyclyl, C NH 2, C NH- C 1-6 alkyl, and C N(C 1-6 alkyl) 2; B 1 is -C NH- or -NHC -; A 1 is a bond; or A 1 is a phenyl or a heteroaryl; each of which is optionally substituted with one or more substituents independently selected from the group consisting of C 1-7 alkyl, C 3-7 cycloalkyl, halo-C 1-7 alkyl, hydroxy, C 1-7 alkoxy, halo, -NR a R b, -OCH 2 CO 2 H, and -OCH 2 C NH 2; or A 1 is a C 3-7 cycloalkyl; A 1 is -C 1-4 alkylene-C 6-10 -aryl-, -C 1-4 alkylene-heteroaryl- or -C 1-4 alkylene-heterocyclyl-, wherein A 1 may be in either direction; and n is 0, 1, 2, 3, 4 or 5; wherein each heteroaryl is a monocyclic or bicyclic aromatic ring comprising 5-10 ring atoms selected from carbon atoms and 1 to 5 heteroatoms, and each heterocyclyl is a monocyclic saturated or partially saturated but non-aromatic moiety comprising 4-7 ring atoms selected from carbon atoms and 1-5 heteroatoms, wherein each heteroatom of a heteroaryl or a heterocyclyl is independently selected from O, N and S. wherein each heteroaryl is a monocyclic or bicyclic aromatic ring comprising 5-10 ring atoms selected from carbon atoms and 1 to 5 heteroatoms, and each heterocyclyl is a monocyclic saturated or partially saturated but non-aromatic moiety comprising 4-7 ring atoms selected from carbon atoms and 1-5 heteroatoms, wherein each heteroatom of a heteroaryl or a heterocyclyl is independently selected from O, N and S.