Patent ID: 8124806

Claim:
Compounds of formula (I) wherein each R 1 independently are the same or different and denote a moiety —(CX 2 ) n —R 3 —R; R 2 denotes a hydrogen, a hydroxyl group or a C 1 -C 4 alkyl group where the alkyl group may be substituted by hydroxyl or amino groups and interrupted by an oxygen atom; each R 3 independently are the same or different and denote a moiety of formula —NR 5 —CO—wherein R 5 has the meaning of R 2 ; X denotes hydrogen or hydroxyl; n is a integer of 1 to 4; and each R independently are the same or different and denote a triiodinated phenyl group, further substituted by two R 4 groups wherein each R 4 are the same or different and denote a hydrogen atom or a non-ionic hydrophilic moiety, provided that at least one R 4 group in the compound of formula (I) is a hydrophilic moiety; and salts or optical active isomers thereof.