Fluorinated GluN2B Receptor Antagonists with a 3-Benzazepine Scaffold Designed for PET Studies

ChemMedChem. 2018 May 23;13(10):1058-1068. doi: 10.1002/cmdc.201700819. Epub 2018 Apr 17.

Abstract

To analyze the N-methyl-d-aspartate (NMDA) receptor distribution in the central nervous system, fluorinated ligands that selectively address the ifenprodil binding site of GluN2B-subunit-containing NMDA receptors were developed. Various strategies to introduce a fluorine atom into the potent GluN2B ligand 2 (3-(4-phenylbutyl)-2,3,4,5-tetrahydro-1H-3-benzazepin-1,7-diol) were pursued, including replacement of the benzylic OH moiety with a fluorine atom (13) and introduction of fluoroethoxy moieties at various positions (14 (7-position), 17 (9-position), 18a-c (1-position)). With respect to GluN2B affinity and selectivity over related receptors, the fluoroethoxy derivatives 14 and 18a are the most promising ligands. Radiosynthesis of fluoroethoxy derivative [18 F]14 was performed by nucleophilic substitution of the phenol 2 with 2-[18 F]fluoroethyl tosylate. On rat brain slices the fluorinated PET tracer [18 F]14 accumulated in regions with high density of NMDA receptors containing GluN2B subunits. The bound radioactivity could not be replaced by (S)-glutamate. However, the GluN2B ligands eliprodil, Ro 25-6981, and the non-labeled 3-benzazepine 14 were able to abolish the specific binding of [18 F]14.

Keywords: 3-benzazepines; GluN2B; NMDA receptor; radiosynthesis; selectivity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites
  • Drug Discovery
  • Hydrocarbons, Fluorinated / chemistry
  • Hydrocarbons, Fluorinated / pharmacology*
  • Molecular Structure
  • Positron-Emission Tomography
  • Receptors, N-Methyl-D-Aspartate / antagonists & inhibitors*

Substances

  • Hydrocarbons, Fluorinated
  • NR2B NMDA receptor
  • Receptors, N-Methyl-D-Aspartate