Patent ID: 8383625

Claim:
A compound of formula I or a pharmaceutically acceptable salt or zwitterionic form thereof, wherein R 1 and R 3 are each independently a C 3 -C 15 -carbocyclic group, optionally substituted by one to three substituents selected from halo, cyano, oxo, hydroxy, amino, nitro, carboxy, C 1 -C 10 -alkyl, C 1 -C 10 -haloalkyl, C 1 -C 10 -alkoxy, C 1 -C 10 alkylcarbonyl, C 1 -C 10 -alkyl-sulfonyl, —SO2NH2, —COO—C 6 -C 10 -aryl, —COO—, C 7 -C 15 -aralkyl, a C 3 -C 15 -carbocyclic group or a 5- to 12-membered heterocyclic group having at least one ring heteroatom selected from nitrogen, oxygen and sulphur; or a 5- to 12-membered heterocyclic group having at least one ring heteroatom selected from nitrogen, oxygen and sulphur, optionally substituted by one to four substituents selected from halo, cyano, oxo, hydroxy, carboxy, nitro, C 1 -C 4 -alkyl, C 1 -C 10 alkylcarbonyl and C 1 -C 10 alkoxy optionally substituted by aminocarbonyl; R 2 is hydroxy; R 4 is C 1 -C 4 -alkyl; R 5 is C 1 -alkyl substituted by —CO—NH—R 6 ; and R 6 is a 5- to 12-membered heterocyclic group having at least one ring heteroatom selected from nitrogen, oxygen and sulphur, and is optionally substituted by one to four substituents selected from halo, cyano, oxo, hydroxy, carboxy, nitro, C 1 -C 4 -alkyl, C 1 -C 10 -alkylcarbonyl and C 1 -C 10 -alkoxy optionally substituted by aminocarbonyl; said compound having a pharmaceutically acceptable counter on comprising fluoride, chloride, bromide, iodide, nitrate, sulfate, phosphate, formate, acetate, trifluoroacetate, propionate, butyrate, lactate, citrate, tartrate, malate, maleate, succinate, benzoate, p-chlorobenzoate, diphenylacetate; triphenylacetate, o-hydroxybenzoate, p-hydroxybenzoate, 1-hydroxynaphthalene-2-carboxylate, 3-hydroxynaphthalene-2-carboxylate, methanesulfonate or benzenesulfonate.