A compound of the formula: wherein X is R 1 is aryl or heteroaryl, wherein said aryl and heteroaryl groups are optionally substituted with one to three substituents independently selected from the group consisting of hydroxyl, cyano, halo, C 1-3 alkyl, O(C 1-3 alkyl), NR 10 R 11, CH 2 NR 10 R 11, (C=O)NR 10 R 11 or heteroaryl; R 2 is (C=O)OR 6, (C=O)CH 2 R 6, R 3 is hydrogen, C 1-3 alkyl, or C 3-7 cycloalkyl, which is optionally substituted with one or two substituents independently selected from the group consisting of R 6, R 11, NR 10 R 11, (C=O)NR 10 R 11 and CH 2 NR 10 R 11; R 4 is hydrogen or C 1-4 alkyl; R 5 is (a) hydrogen, (b) (CH 2) m -cyclohexyl, which is optionally substituted with NR 10 R 11 or heterocyclyl, (c) (CH 2) n -piperidinyl, which is optionally substituted with benzyl, R 11, SO 2 R 10, SO 2 R 6, (C=O)R 6, R 6 or (C=O)R 10, (d) C 1-4 alkyl which is optionally substituted with R 6, NR 10 R 11 or NHSO 2 CH 3; each R 6 is independently aryl, heteroaryl, heterocyclyl or C 3-6 cycloalkyl, wherein said aryl and heteroaryl groups are optionally substituted with one to three substituents independently selected from the group consisting of hydroxyl, oxo, cyano, halo, C 1-3 alkyl, C 1-3 haloalkyl, O(C 1-3 alkyl), NR 10 R 11, CH 2 NR 10 R 11, CH 2 CN, (C=O)NR 10 R 11 and CH(NH 2)(OCH 3); R 7 is hydrogen or C 1-3 alkyl; R 8 is hydrogen or C 1-3 alkyl; R 9 is hydrogen, C 1-3 alkyl, C 1-3 haloalkyl or phenyl, wherein said phenyl group is optionally substituted with halo, cyano, methyl or CH 2 NR 10 R 11; each R 10 is independently hydrogen or C 1-5 alkyl; each R 11 is independently hydrogen or C 1-3 alkyl, which is optionally substituted with one to three substituents independently selected from the group consisting of halo and hydroxyl; R x is hydrogen or C 1-4 alkyl, which is optionally substituted with one to three substituents independently selected from the group consisting of halo, hydroxyl, N + CH 3 R 10 R 11 and NR 10 R 11, m is zero or one; n is zero or one; or a pharmaceutically acceptable salt thereof. wherein X is R 1 is aryl or heteroaryl, wherein said aryl and heteroaryl groups are optionally substituted with one to three substituents independently selected from the group consisting of hydroxyl, cyano, halo, C 1-3 alkyl, O(C 1-3 alkyl), NR 10 R 11, CH 2 NR 10 R 11, (C=O)NR 10 R 11 or heteroaryl; R 2 is (C=O)OR 6, (C=O)CH 2 R 6, R 3 is hydrogen, C 1-3 alkyl, or C 3-7 cycloalkyl, which is optionally substituted with one or two substituents independently selected from the group consisting of R 6, R 11, NR 10 R 11, (C=O)NR 10 R 11 and CH 2 NR 10 R 11; R 4 is hydrogen or C 1-4 alkyl; R 5 is (a) hydrogen, (b) (CH 2) m -cyclohexyl, which is optionally substituted with NR 10 R 11 or heterocyclyl, (c) (CH 2) n -piperidinyl, which is optionally substituted with benzyl, R 11, SO 2 R 10, SO 2 R 6, (C=O)R 6, R 6 or (C=O)R 10, (d) C 1-4 alkyl which is optionally substituted with R 6, NR 10 R 11 or NHSO 2 CH 3; (a) hydrogen, (b) (CH 2) m -cyclohexyl, which is optionally substituted with NR 10 R 11 or heterocyclyl, (c) (CH 2) n -piperidinyl, which is optionally substituted with benzyl, R 11, SO 2 R 10, SO 2 R 6, (C=O)R 6, R 6 or (C=O)R 10, (d) C 1-4 alkyl which is optionally substituted with R 6, NR 10 R 11 or NHSO 2 CH 3; each R 6 is independently aryl, heteroaryl, heterocyclyl or C 3-6 cycloalkyl, wherein said aryl and heteroaryl groups are optionally substituted with one to three substituents independently selected from the group consisting of hydroxyl, oxo, cyano, halo, C 1-3 alkyl, C 1-3 haloalkyl, O(C 1-3 alkyl), NR 10 R 11, CH 2 NR 10 R 11, CH 2 CN, (C=O)NR 10 R 11 and CH(NH 2)(OCH 3); R 7 is hydrogen or C 1-3 alkyl; R 8 is hydrogen or C 1-3 alkyl; R 9 is hydrogen, C 1-3 alkyl, C 1-3 haloalkyl or phenyl, wherein said phenyl group is optionally substituted with halo, cyano, methyl or CH 2 NR 10 R 11; each R 10 is independently hydrogen or C 1-5 alkyl; each R 11 is independently hydrogen or C 1-3 alkyl, which is optionally substituted with one to three substituents independently selected from the group consisting of halo and hydroxyl; R x is hydrogen or C 1-4 alkyl, which is optionally substituted with one to three substituents independently selected from the group consisting of halo, hydroxyl, N + CH 3 R 10 R 11 and NR 10 R 11, m is zero or one; n is zero or one; or a pharmaceutically acceptable salt thereof.