A compound of formula (Ia'): or a pharmaceutically acceptable salt thereof, wherein; R 1 is selected from the group consisting of H, F, C 1 -C 3 alkyl, and C 1 -C 3 haloalkyl; R 2 is selected from the group consisting of halogen, C 1 -C 3 alkyl, C 1 -C 3 haloalkyl, OC 1 -C 3 alkyl, OC 1 -C 3 haloalkyl, OH, C 2 -C 3 alkenyl, C 2 -C 3 alkynyl, N(C 1 -C 3 alkyl) 2 , NH(C 1 -C 3 alkyl), SC 1 -C 3 alkyl; R 3 is selected from the group consisting of halogen, C 1 -C 3 alkyl, C 1 -C 3 haloalkyl, OC 1 -C 3 alkyl, OC 1 -C 3 haloalkyl, OH, C 2 -C 3 alkenyl, C 2 -C 3 alkynyl, N(C 1 -C 3 alkyl) 2 , NH(C 1 -C 3 alkyl), SC 1 -C 3 alkyl; R 4 is selected from the group consisting of H, F, C 1 -C 4 alkyl, and C 1 -C 3 haloalkyl; R 5 is selected from the group consisting of H, F, Cl, OR 6 , C 1 -C 3 alkyl, and C 1 -C 3 haloalkyl; each R 6 is independently selected from the group consisting of H, C 1 -C 4 alkyl, and C 1 -C 4 haloalkyl; X 1 is C(O); X 2 is CHR 8 CHR 8 ; X 3 is selected from the group consisting of COOR 6 , SO 2 R 6 , and C(O)N(R 9 ) 2 , where each R 9 is independently selected from the group consisting of H, COOR 6 , and SO 2 R 6 ; each R 8 is selected from the group consisting of H, C 1 -C 4 alkyl, C 1 -C 4 alkyl substituted by OH, C 1 -C 4 alkyl substituted by OC 1 -C 3 alkyl, and C 3 -C 6 cycloalkyl, and where optionally 2 R 8 are taken together, along with the atoms to which they are attached, to form a 3-to 6-membered fused ring; wherein when X 1 -X 2 -X 3 is X 1 -CHR 8 CH 2 -X 3 , at least one of R 2 and R 3 is not selected from the group consisting of halogen, OC 1 -C 3 alkyl, OC 1 -C 3 haloalkyl, OH, C 1 -C 3 alkyl, and C 1 -C 3 haloalkyl. R 1 is selected from the group consisting of H, F, C 1 -C 3 alkyl, and C 1 -C 3 haloalkyl; R 2 is selected from the group consisting of halogen, C 1 -C 3 alkyl, C 1 -C 3 haloalkyl, OC 1 -C 3 alkyl, OC 1 -C 3 haloalkyl, OH, C 2 -C 3 alkenyl, C 2 -C 3 alkynyl, N(C 1 -C 3 alkyl) 2 , NH(C 1 -C 3 alkyl), SC 1 -C 3 alkyl; R 3 is selected from the group consisting of halogen, C 1 -C 3 alkyl, C 1 -C 3 haloalkyl, OC 1 -C 3 alkyl, OC 1 -C 3 haloalkyl, OH, C 2 -C 3 alkenyl, C 2 -C 3 alkynyl, N(C 1 -C 3 alkyl) 2 , NH(C 1 -C 3 alkyl), SC 1 -C 3 alkyl; R 4 is selected from the group consisting of H, F, C 1 -C 4 alkyl, and C 1 -C 3 haloalkyl; R 5 is selected from the group consisting of H, F, Cl, OR 6 , C 1 -C 3 alkyl, and C 1 -C 3 haloalkyl; each R 6 is independently selected from the group consisting of H, C 1 -C 4 alkyl, and C 1 -C 4 haloalkyl; X 1 is C(O); X 2 is CHR 8 CHR 8 ; X 3 is selected from the group consisting of COOR 6 , SO 2 R 6 , and C(O)N(R 9 ) 2 , where each R 9 is independently selected from the group consisting of H, COOR 6 , and SO 2 R 6 ; each R 8 is selected from the group consisting of H, C 1 -C 4 alkyl, C 1 -C 4 alkyl substituted by OH, C 1 -C 4 alkyl substituted by OC 1 -C 3 alkyl, and C 3 -C 6 cycloalkyl, and where optionally 2 R 8 are taken together, along with the atoms to which they are attached, to form a 3-to 6-membered fused ring; wherein when X 1 -X 2 -X 3 is X 1 -CHR 8 CH 2 -X 3 , at least one of R 2 and R 3 is not selected from the group consisting of halogen, OC 1 -C 3 alkyl, OC 1 -C 3 haloalkyl, OH, C 1 -C 3 alkyl, and C 1 -C 3 haloalkyl. <EOS>