Synthesis and in vitro biological evaluation of carbon-11-labeled quinoline derivatives as new candidate PET radioligands for cannabinoid CB2 receptor imaging

Bioorg Med Chem. 2010 Mar 15;18(6):2099-2106. doi: 10.1016/j.bmc.2010.02.011. Epub 2010 Feb 10.

Abstract

Cannabinoids have been recently proposed as a new family of potential antitumor agents, and cannabinoid receptor 2 (CB2) is believed to be over-expressed in tumor cells. This study was designed to develop new radioligands for imaging of CB2 receptor in cancer using biomedical imaging technique positron emission tomography (PET). Carbon-11-labeled 2-oxoquinoline and 2-chloroquinoline derivatives, [(11)C]6a-d and [(11)C]9a-d, were prepared by O-[(11)C]methylation of their corresponding precursors using [(11)C]CH(3)OTf under basic conditions and isolated by a simplified solid-phase extraction (SPE) method in 40-50% radiochemical yields based on [(11)C]CO(2) and decay corrected to end of bombardment (EOB). The overall synthesis time from EOB was 15-20 min, the radiochemical purity was >99%, and the specific activity at end of synthesis (EOS) was 111-185 GBq/micromol. Radioligand binding assays indicated compounds 6f, 6b, and 9f display potent in vitro binding affinities with nanomolar K(i) values and at least 100-2000-fold selectivity for CB2.

Publication types

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

MeSH terms

  • Binding Sites
  • Carbon Radioisotopes / chemistry
  • Drug Design
  • Humans
  • Isotope Labeling
  • Ligands
  • Molecular Imaging / methods
  • Molecular Structure
  • Positron-Emission Tomography / methods*
  • Quinolines / chemical synthesis*
  • Quinolines / chemistry
  • Quinolines / pharmacology*
  • Radioligand Assay / methods*
  • Receptor, Cannabinoid, CB1 / analysis
  • Receptor, Cannabinoid, CB1 / chemistry
  • Receptor, Cannabinoid, CB1 / metabolism
  • Receptor, Cannabinoid, CB2 / analysis*
  • Receptor, Cannabinoid, CB2 / chemistry
  • Receptor, Cannabinoid, CB2 / metabolism
  • Solid Phase Extraction
  • Stereoisomerism
  • Structure-Activity Relationship

Substances

  • Carbon Radioisotopes
  • Ligands
  • Quinolines
  • Receptor, Cannabinoid, CB1
  • Receptor, Cannabinoid, CB2