A compound of formula I: or a pharmaceutically acceptable salt thereof, wherein: R 1 is hydrogen or C 1-4 alkyl; R 2 is F, Cl, -CF 3, -OCF 3, -OCHF 2, -OCH 2 Ph, -OCH 3, -CN, -CH 3, R 3 is halogen, -OR, -CN, C 1-6 aliphatic optionally substituted with 1, 2, or 3 halogens, or -L-R'; or R 2 and R 3 are optionally taken together with the carbon atoms to which they are attached and any intervening atoms to form a 5-8 membered partially unsaturated ring having 0-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur; R 4 is hydrogen, halogen, -OR 5, -CN, C 1-6 aliphatic optionally substituted with 1, 2, or 3 halogens, or -L-R'; each R is independently hydrogen or an optionally substituted group selected from C 1-6 aliphatic, a 3-8 membered saturated or partially unsaturated monocyclic carbocyclic ring, phenyl, an 8-10 membered bicyclic aromatic carbocyclic ring, a 4-8 membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 5-6 membered monocyclic heteroaromatic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaromatic ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; R 5 is hydrogen, -(CH 2) n -phenyl, or C 1-6 alkyl optionally substituted with 1, 2, or 3 halogens; each L is independently a C 1-6 bivalent straight or branched hydrocarbon chain wherein 1-4 methylene units of the chain are independently and optionally replaced with -O-, -C -, -C O-, -OC -, -OC N -, - NC O-, -C N -, - NC -, -N -, -N C N -, -S-, -SO-, or -SO 2 -; each R' is independently hydrogen, C 1-6 aliphatic, or an optionally substituted 4-8 membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur; R 6 is hydrogen or C 1-4 alkyl; R 7 is hydrogen, -CO 2 R, C 1-6 optionally substituted aliphatic group, or a bivalent 3-7 membered ring; L 1 is selected from the group consisting of and n is independently 0, 1, 2, 3, 4, or 5; wherein said compound is other than compounds 4-[ -1-({5-chloro-6-[(2-oxo-1,3-oxazolidin-5-yl)methoxy]-1H-indol-2-yl}formamido)-2-hydroxyethyl]benzoic acid and 4-[ -1-[[5-Chloro-6-[2-(2-hydroxyethylamino)-2-oxo-ethoxy]-1H-indole-2-carbonyl]amino]-2-hydroxy-ethyl]benzoic acid. R 1 is hydrogen or C 1-4 alkyl; R 2 is F, Cl, -CF 3, -OCF 3, -OCHF 2, -OCH 2 Ph, -OCH 3, -CN, -CH 3, R 3 is halogen, -OR, -CN, C 1-6 aliphatic optionally substituted with 1, 2, or 3 halogens, or -L-R'; or R 2 and R 3 are optionally taken together with the carbon atoms to which they are attached and any intervening atoms to form a 5-8 membered partially unsaturated ring having 0-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur; R 4 is hydrogen, halogen, -OR 5, -CN, C 1-6 aliphatic optionally substituted with 1, 2, or 3 halogens, or -L-R'; each R is independently hydrogen or an optionally substituted group selected from C 1-6 aliphatic, a 3-8 membered saturated or partially unsaturated monocyclic carbocyclic ring, phenyl, an 8-10 membered bicyclic aromatic carbocyclic ring, a 4-8 membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 5-6 membered monocyclic heteroaromatic ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8-10 membered bicyclic heteroaromatic ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; R 5 is hydrogen, -(CH 2) n -phenyl, or C 1-6 alkyl optionally substituted with 1, 2, or 3 halogens; each L is independently a C 1-6 bivalent straight or branched hydrocarbon chain wherein 1-4 methylene units of the chain are independently and optionally replaced with -O-, -C -, -C O-, -OC -, -OC N -, - NC O-, -C N -, - NC -, -N -, -N C N -, -S-, -SO-, or -SO 2 -; each R' is independently hydrogen, C 1-6 aliphatic, or an optionally substituted 4-8 membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur; R 6 is hydrogen or C 1-4 alkyl; R 7 is hydrogen, -CO 2 R, C 1-6 optionally substituted aliphatic group, or a bivalent 3-7 membered ring; L 1 is selected from the group consisting of and n is independently 0, 1, 2, 3, 4, or 5; wherein said compound is other than compounds 4-[ -1-({5-chloro-6-[(2-oxo-1,3-oxazolidin-5-yl)methoxy]-1H-indol-2-yl}formamido)-2-hydroxyethyl]benzoic acid and 4-[ -1-[[5-Chloro-6-[2-(2-hydroxyethylamino)-2-oxo-ethoxy]-1H-indole-2-carbonyl]amino]-2-hydroxy-ethyl]benzoic acid.