Synthesis of a cross-bridged cyclam derivative for peptide conjugation and 64Cu radiolabeling

Bioconjug Chem. 2008 Jul;19(7):1476-84. doi: 10.1021/bc800039e. Epub 2008 Jul 3.

Abstract

The increased use of copper radioisotopes in radiopharmaceutical applications has created a need for bifunctional chelators (BFCs) that form stable radiocopper complexes and allow covalent attachment to biological molecules. Previous studies have established that 4,11-bis-(carbo- tert-butoxymethyl)-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane (H 2CB-TE2A), a member of the ethylene "cross-bridged" cyclam (CB-cyclam) class of bicyclic tetraaza macrocycles, forms highly kinetically stable complexes with Cu(II) and is less susceptible to in vivo transchelation than its nonbridged analogue, 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetic acid (TETA). Herein, we report a convenient synthesis of a novel cross-bridged BFC that is structurally analogous to CB-TE2A in that it possesses two coordinating acetate arms, but in addition possesses a third orthogonally protected arm for conjugation to peptides and other targeting agents. Application of this strategy to cross-bridged chelators may also enable the development of even further improved agents for (64)Cu-mediated diagnostic positron emission tomography (PET) imaging as well as for targeted radiotherapeutic applications.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Amines / chemistry
  • Chelating Agents / chemical synthesis*
  • Chelating Agents / chemistry
  • Copper Radioisotopes
  • Cross-Linking Reagents / chemical synthesis*
  • Cross-Linking Reagents / chemistry
  • Lactams, Macrocyclic / chemical synthesis*
  • Lactams, Macrocyclic / chemistry
  • Ligands
  • Peptides / chemistry*
  • Peptides / therapeutic use
  • Staining and Labeling / methods*

Substances

  • Amines
  • Chelating Agents
  • Copper Radioisotopes
  • Cross-Linking Reagents
  • Lactams, Macrocyclic
  • Ligands
  • Peptides