Patent ID: 8343910

Claim:
A compound of the formula: wherein: R 1 is a radical of the formula: —R 5 —R 6 —B wherein R 2 is H or —SO 3 H at position 2 of the fluorene ring; B is maleimido, —S—CO—CH 3 or a PEG moiety; R 5 is selected from the group consisting of —NH—, —S—, —CO—, —COO—, —CH 2 —, SO 2 —, —SO 3 —, —PO 2 — and —PO 3 —; R 6 is a bond or a radical selected from the group consisting of —CO—, —COO—, —CH 2 —, —CH(CH 3 )—, —CO—NH—, —CS—NH—, —CO—CH 2 —NH—CO—, —CO—CH(CH 3 )—NH—CO—, —CO—CH 2 —NH—CO—NH, Z is O, S or NH; R 7 is selected from the group consisting of C 1 -C 18 straight or branched alkylene, phenylene, an oxyalkylene radical having 3-18 carbon atoms in the backbone, a residue of a peptide containing 2-10 amino acid residues, and a residue of a saccharide containing 1-10 monosaccharide residues; and R 8 is a C 1 -C 8 straight or branched alkylene, when B is maleimido or —S—CO—CH 3 .