Patent ID: 7947730

Claim:
A compound of formula I in salt or zwitterionic form wherein R 1 and R 3 are each independently 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; R 2 is hydroxy; J is C 1 -C 2 -alkylene; R 4 is C 1 -C 4 -alkyl; R 5 is C 1 -alkyl substituted by —CO—R 6 , or —CO—NH—R 6 , or R 5 is C 2 -C 10 -alkyl substituted by —O—R 6 , —O—CO—R 6 , or —R 8 , or R 5 is C 2 -C 10 -alkenyl or C 2 -C 10 -alkynyl optionally substituted by —R 8 ; R 6 is a C 3 -C 15 -carbocyclic group, or R 6 is C 1 -C 10 -alkyl optionally substituted by C 1 -C 10 -alkoxy, —O—R 8 or a C 3 -C 15 -carbocyclic group; and R 8 is a C 3 -C 15 -carbocyclic group.