A compound represented by formula I: or a pharmaceutically acceptable salt, stereoisomer or N-oxide thereof, wherein R b is selected from the group consisting of H, halogen, hydroxyl, cyano and C 1 -C 6 alkyl; R is H, C 1 -C 6 alkyl or -C -C 1 -C 6 alkyl; R 1 is H or C 1 -C 6 alkyl; R 2 is H or C 1 -C 6 alkyl; R 3 is C 1 -C 6 alkyl; C 1 -C 6 alkoxy; -O-C 1 -C 6 alkylene-phenyl; C 2 -C 6 alkenyl; C 2 -C 6 alkynyl; C 3 -C 6 cycloalkyl; phenyl; or heteroaryl including from 5 to 6 ring atoms wherein 1, 2, or 3 of the ring atoms are independently selected from the group consisting ofN, NH, N(C1-C3 alkyl), O, and S;, wherein R 3 is optionally substituted with one, two, or three substituents independently selected from the group consisting of amino, protected amino, halogen, C 1 -C 6 alkyl, C 1 -C 6 alkoxy, hydroxyl, phenyl (optionally substituted by one, two, or three substituents each independently selected from R a), benzyl (optionally substituted by one, two, or three substituents each independently selected from R a), and-C 1 -C 6 alkylene-C 3 -C 6 cycloalkyl (optionally substituted by one, two or three substituents independent selected from halogen and C 1 -C 6 alkyl); R a is selected from the group consisting of halogen, C 1 -C 6 alkyl (optionally substituted by one, two or three halogens), C 3 -C 6 cycloalkyl (optionally substituted by one, two or three halogens), and C 1 -C 6 alkoxy (optionally substituted by one, two or three halogens); R 4 is H or C 1 -C 6 alkyl; R 5 is H or C 1 -C 6 alkyl; X is selected from the group consisting of: H; C 1 -C 6 alkyl; -OH; C 1 -C 6 alkoxy;-CO 2 H; -C NR c R d; and heteroaryl including from 5 to 6 ring atoms wherein 1, 2, or 3 of the ring atoms are independently selected from the group consisting ofN, NH, N(C1-C3 alkyl), O, and S, wherein the heteroaryl ring may be optionally substituted with one, two, or three substituents independently selected from the group consisting of halogen, C 1 -C 6 alkyl, C 1 -C 6 alkoxy, hydroxyl and phenyl; and R c and R d are each independently selected from the group consisting of H, C 1 -C 6 alkyl, or phenyl, or R c and R d together with the nitrogen to which they are attached, form heterocyclyl including from 4 to 6 ring atoms; wherein the heterocyclyl includes not more than two ring heteroatoms (including the nitrogen atom attached to R c and R d), and the second ring heteroatom, when present, is independently selected from the group consisting ofN, NH, N(C1-C3 alkyl), O, and S; and wherein the heterocyclyl is optionally substituted with from 1-3 substituents independently selected from the group consisting of halogen, cyano, oxo, and C 1 -C 6 alkyl. R b is selected from the group consisting of H, halogen, hydroxyl, cyano and C 1 -C 6 alkyl; R is H, C 1 -C 6 alkyl or -C -C 1 -C 6 alkyl; R 1 is H or C 1 -C 6 alkyl; R 2 is H or C 1 -C 6 alkyl; R 3 is C 1 -C 6 alkyl; C 1 -C 6 alkoxy; -O-C 1 -C 6 alkylene-phenyl; C 2 -C 6 alkenyl; C 2 -C 6 alkynyl; C 3 -C 6 cycloalkyl; phenyl; or heteroaryl including from 5 to 6 ring atoms wherein 1, 2, or 3 of the ring atoms are independently selected from the group consisting ofN, NH, N(C1-C3 alkyl), O, and S;, wherein R 3 is optionally substituted with one, two, or three substituents independently selected from the group consisting of amino, protected amino, halogen, C 1 -C 6 alkyl, C 1 -C 6 alkoxy, hydroxyl, phenyl (optionally substituted by one, two, or three substituents each independently selected from R a), benzyl (optionally substituted by one, two, or three substituents each independently selected from R a), and-C 1 -C 6 alkylene-C 3 -C 6 cycloalkyl (optionally substituted by one, two or three substituents independent selected from halogen and C 1 -C 6 alkyl); R a is selected from the group consisting of halogen, C 1 -C 6 alkyl (optionally substituted by one, two or three halogens), C 3 -C 6 cycloalkyl (optionally substituted by one, two or three halogens), and C 1 -C 6 alkoxy (optionally substituted by one, two or three halogens); R 4 is H or C 1 -C 6 alkyl; R 5 is H or C 1 -C 6 alkyl; X is selected from the group consisting of: H; C 1 -C 6 alkyl; -OH; C 1 -C 6 alkoxy;-CO 2 H; -C NR c R d; and heteroaryl including from 5 to 6 ring atoms wherein 1, 2, or 3 of the ring atoms are independently selected from the group consisting ofN, NH, N(C1-C3 alkyl), O, and S, wherein the heteroaryl ring may be optionally substituted with one, two, or three substituents independently selected from the group consisting of halogen, C 1 -C 6 alkyl, C 1 -C 6 alkoxy, hydroxyl and phenyl; and R c and R d are each independently selected from the group consisting of H, C 1 -C 6 alkyl, or phenyl, or R c and R d together with the nitrogen to which they are attached, form heterocyclyl including from 4 to 6 ring atoms; wherein the heterocyclyl includes not more than two ring heteroatoms (including the nitrogen atom attached to R c and R d), and the second ring heteroatom, when present, is independently selected from the group consisting ofN, NH, N(C1-C3 alkyl), O, and S; and wherein the heterocyclyl is optionally substituted with from 1-3 substituents independently selected from the group consisting of halogen, cyano, oxo, and C 1 -C 6 alkyl.