SCHEDULED MAINTENANCE
Structural characterisation and bioconjugation of an active ester containing oxorhenium(V) complex incorporating a thioether donor
Abstract
A simple new 2,3,5,6-tetrafluorophenyl ester containing diamide–thioether–thiol bifunctional chelating agent LH3, HS(CH2)2SCH2C(O)NHCH2C(O)NH(CH2)3C(O)OC6HF4, has been synthesised. The key intermediates were prepared using standard peptide chemistry procedures. Reaction of LH3 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 complex 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 complex [ReOL] was conjugated with the small protein N-TIMP-2 by aminolysis at a lysine residue, to form a 1∶1 adduct as established by electrospray mass spectrometry.
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