STRUCTURAL CHARACTERIZATION AND BIOCONJUGATION OF AN ACTIVE ESTER-CONTAINING OXORHENIUM(V) COMPLEX INCORPORATING A THIOETHER DONOR

A simple new 2,3,5,6-tetrafluorophenyl ester containing diamide-thioet her-thiol bifunctional chelating agent LH3, HS(CH2)(2)SCH2C(O)NHCH2C(O )NH(CH2)(3)C(O)OC6HF4, has been synthesised. The key intermediates wer e prepared using standard peptide chemistry procedures. Reaction of LH 3 with [Bu4N][ReOCl4] formed an uncharged oxorhenium(v) complex, which was characterised by X-ray structural analysis. The five-co-ordinate complex showed approximately square-pyramidal geometry with an apical oxo group and a basal ligand set comprising a deprotonated thiol group , two deprotonated amide groups, and a thioether group. A second compl ex of stoichiometry [ReO(LH2)(2)]Cl was formed by reaction of LH3 with a rhenium(v) gluconate intermediate in water at pH 4.7. The 1 : 1 com plex [ReOL] was conjugated with the small protein N-TIMP-2 by aminolys is at a lysine residue, to form a 1: 1 adduct as established by electr ospray mass spectrometry.