Synthesis and evaluation of a novel series of 2-chloro-5-((1-methyl-2-(S)-pyrrolidinyl)methoxy)-3-(2-(4-pyridinyl)vinyl)pyridine analogues as potential positron emission tomography imaging agents for nicotinic acetylcholine receptors

J Med Chem. 2002 Jun 20;45(13):2841-9. doi: 10.1021/jm010550n.

Abstract

Reportedly, 2-[(18)F]fluoro-A-85380, 1, a promising radiotracer for imaging the nicotinic acetylcholine receptor (nAChR) by positron emission tomography (PET) in humans, exhibits slow penetration through the blood-brain barrier (BBB) due to its low lipophilicity. A ligand for nAChRs with greater lipophilicity than that of 1 would be potentially more favorable for PET imaging of nAChR due to its faster penetration through the BBB. Herein, a novel series of compounds has been developed based on the high affinity ligand for nAChRs, 2-chloro-5-((1-methyl-2-(S)-pyrrolidinyl)methoxy)-3-(2-(4-pyridinyl)vinyl)pyridine, 3b. The in vitro binding affinities for the new series were found to be in the range of K(i) = 9-331 pM. A molecular modeling study showed differences in the comformational profiles and the electronic properties of these compounds, which provides further insight into the structure-activity relationships at nAChR. Lipophilicities of the compounds 3b-6b have been found to be substantially higher than that of 1. As a result, compounds 3b-6b might exhibit a faster penetration through the BBB than the less lipophilic 1. The N-methyl derivatives 3b and 6b demonstrated very high affinities at nAChRs (K(i) = 28 and 23 pM, respectively) and will be targets for development of (11)CH(3)-labeled derivatives as radiotracers for PET imaging of nAChRs.

MeSH terms

  • Animals
  • Binding, Competitive
  • Brain / metabolism
  • In Vitro Techniques
  • Ligands
  • Models, Molecular
  • Molecular Conformation
  • Pyridines / chemical synthesis*
  • Pyridines / chemistry
  • Pyridines / pharmacology
  • Pyrrolidines / chemical synthesis*
  • Pyrrolidines / chemistry
  • Pyrrolidines / pharmacology
  • Radioligand Assay
  • Rats
  • Receptors, Nicotinic / metabolism*
  • Structure-Activity Relationship
  • Tomography, Emission-Computed

Substances

  • 2-chloro-5-((1-methyl-2-pyrrolidinyl)methoxy)-3-(2-(4-pyridinyl)ethyl)pyridine
  • 5-(2-(4-pyridinyl)vinyl)-6-chloro-3-(1-methyl-2-pyrrolidinylmethoxy)pyridine
  • Ligands
  • Pyridines
  • Pyrrolidines
  • Receptors, Nicotinic