Pd-catalyzed direct C-H bond functionalization of spirocyclic σ1 ligands: generation of a pharmacophore model and analysis of the reverse binding mode by docking into a 3D homology model of the σ1 receptor

J Med Chem. 2012 Sep 27;55(18):8047-65. doi: 10.1021/jm300894h. Epub 2012 Sep 10.

Abstract

To explore the hydrophobic binding region of the σ(1) receptor protein, regioisomeric spirocyclic thiophenes 9-11 were developed as versatile building blocks. Regioselective α- and β-arylation using the catalyst systems PdCl(2)/bipy/Ag(2)CO(3) and PdCl(2)/P[OCH(CF(3))(2)](3)/Ag(2)CO(3) allowed the introduction of various aryl moieties at different positions in the last step of the synthesis. The increasing σ(1) affinity in the order 4 < 5/6 < 7/8 indicates that the positions of the additional aryl moiety and the S atom in the spirocyclic thiophene systems control the σ(1) affinity. The main features of the pharmacophore model developed for this class of σ(1) ligands are a positive ionizable group, a H-bond acceptor group, two hydrophobic moieties, and one hydrophobic aromatic group. Docking of the ligands into a σ(1) 3D homology model via molecular mechanics/Poisson-Boltzmann surface area calculations led to a very good correlation between the experimentally determined and estimated free energy of receptor binding. These calculations support the hypothesis of a reverse binding mode of ligands bearing the aryl moiety at the "top" (compounds 2, 3, 7, and 8) and "left" (compounds 4, 5, and 6) positions, respectively.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Catalysis
  • Drug Design
  • Hydrogen Bonding
  • Ligands
  • Molecular Docking Simulation*
  • Palladium / chemistry*
  • Protein Binding
  • Receptors, sigma / chemistry*
  • Receptors, sigma / metabolism*
  • Reproducibility of Results
  • Sequence Homology, Amino Acid*
  • Sigma-1 Receptor
  • Spiro Compounds / chemistry*
  • Spiro Compounds / metabolism*
  • Stereoisomerism
  • Structure-Activity Relationship

Substances

  • Ligands
  • Receptors, sigma
  • Spiro Compounds
  • Palladium