Patent ID: 8066974

Claim:
A compounds of formula (I) and salts or optical active isomers thereof wherein each R 1 are the same or different and denote a moiety —(CX 2 ) n —R 3 —R; R 2 denotes hydrogen or C 1 -C 4 alkyl where the alkyl group may be substituted by hydroxyl groups or interrupted by an oxygen atom; each R 3 are the same or different and denote a moiety of formula —Z—CY—NR 5 — wherein R 5 has the meaning of R 2 Y denotes oxygen or sulphur; X denotes hydrogen or hydroxyl; Z denotes oxygen or a NH group; 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 groups R 4 wherein each R 4 are the same or different and denote a hydrogen atom or a non-ionic hydrophilic moiety comprising esters, amides or amine moieties, provided that at least one R 4 group in the compound of formula (I) is a hydrophilic moiety.