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 linear or branched C 1-7 alkylene; which is optionally substituted with one or more substituents independently selected from the group consisting of halo, C 3-7 cycloalkyl, C 1 - 7 alkoxy, hydroxy and O-acetate; in which two geminal alkyl can optionally combine to form a C 3-7 cycloalkyl; or A 1 is a linear or branched C 1-7 alkenylene; or A 1 is a linear C 1-4 alkylene wherein one or more carbon atom(s) is/are replaced with an heteroatom selected from O, NR c; and A 1 is optionally substituted with one or more substituents independently selected from the group consisting of halo and C 1-7 alkyl; in which R c for each occurrence, is independently H, C 1-7 alkyl, -C -O-C 1-7 alkyl or -CH 2 C OH; or 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 linear or branched C 1-7 alkylene; which is optionally substituted with one or more substituents independently selected from the group consisting of halo, C 3-7 cycloalkyl, C 1 - 7 alkoxy, hydroxy and O-acetate; in which two geminal alkyl can optionally combine to form a C 3-7 cycloalkyl; or A 1 is a linear or branched C 1-7 alkenylene; or A 1 is a linear C 1-4 alkylene wherein one or more carbon atom(s) is/are replaced with an heteroatom selected from O, NR c; and A 1 is optionally substituted with one or more substituents independently selected from the group consisting of halo and C 1-7 alkyl; in which R c for each occurrence, is independently H, C 1-7 alkyl, -C -O-C 1-7 alkyl or -CH 2 C OH; or 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.