(S)-5-(p-nitrobenzyl)-PCTA, a promising bifunctional ligand with advantageous metal ion complexation kinetics

Bioconjug Chem. 2009 Mar 18;20(3):565-75. doi: 10.1021/bc8004914.


A bifunctional version of PCTA (3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9,-triacetic acid) that exhibits fast complexation kinetics with the trivalent lanthanide(III) ions was synthesized in reasonable yields starting from N,N',N''-tristosyl-(S)-2-(p-nitrobenzyl)-diethylenetriamine. pH-potentiometric studies showed that the basicities of p-nitrobenzyl-PCTA and the parent ligand PCTA were similar. The stability of M(NO(2)-Bn-PCTA) (M = Mg(2+), Ca(2+), Cu(2+), Zn(2+)) complexes was similar to that of the corresponding PCTA complexes, while the stability of Ln(3+) complexes of the bifunctional ligand is somewhat lower than that of PCTA chelates. The rate of complex formation of Ln(NO(2)-Bn-PCTA) complexes was found to be quite similar to that of PCTA, a ligand known to exhibit the fastest formation rates among all lanthanide macrocyclic ligand complexes studied to date. The acid-catalyzed decomplexation kinetic studies of the selected Ln(NO(2)-Bn-PCTA) complexes showed that the kinetic inertness of the complexes was comparable to that of Ln(DOTA) chelates making the bifunctional ligand NO(2)-Bn-PCTA suitable for labeling biological vectors with radioisotopes for nuclear medicine applications.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetates / chemical synthesis
  • Acetates / chemistry*
  • Bridged Bicyclo Compounds, Heterocyclic / chemical synthesis
  • Bridged Bicyclo Compounds, Heterocyclic / chemistry*
  • Coordination Complexes / chemical synthesis
  • Coordination Complexes / chemistry*
  • Ions / chemistry
  • Kinetics
  • Lanthanoid Series Elements / chemistry*
  • Ligands
  • Potentiometry


  • 3,6,9,15-tetraazabicyclo(9.3.1)pentadeca-1(15),11,13-triene-3,6,9-triacetic acid
  • Acetates
  • Bridged Bicyclo Compounds, Heterocyclic
  • Coordination Complexes
  • Ions
  • Lanthanoid Series Elements
  • Ligands