Patent ID: 8168654

Claim:
A compound of formula I in salt or zwitterionic form wherein R 1 and R 3 are each independently phenyl or a 5-membered heterocyclic group having at least one ring heteroatom selected from nitrogen, oxygen and sulphur; R 2 is hydrogen, halo, hydroxy, C 1 -C 8 -alkoxy or C 1 -C 8 -alkyl optionally substituted by hydroxy; R 4 is C 1 -C 8 -alkyl substituted by —NR 5 —CO—R 6 , —CO—NR 9 R 10 ; R 5 is hydrogen or C 1 -C 8 -alkyl; R 6 is C 1 -C 8 -alkyl, C 2 -C 8 -alkenyl, C 2 -C 10 -alkynyl or C 1 -C 8 -alkoxy in each case optionally substituted by a 4- to 12-membered heterocyclic group having at least one ring heteroatom selected from nitrogen, oxygen and sulphur, or R 6 is a 4- to 12-membered heterocyclic group having at least one ring heteroatom selected from nitrogen, oxygen and sulphur; R 9 is hydrogen or C 1 -C 8 -alkyl; R 10 is hydrogen, C 1 -C 8 -alkyl optionally substituted by cyano, amino, nitro, carboxy, C 1 -C 8 -alkoxy, or by a 4- to 12-membered heterocyclic group having at least one ring heteroatom selected from nitrogen, oxygen and sulphur, or R 10 is a 4- to 12-membered heterocyclic group having at least one ring heteroatom selected from nitrogen, oxygen and sulphur.