Structure-activity relationships of constrained phenylethylamine ligands for the serotonin 5-HT2 receptors

PLoS One. 2013 Nov 7;8(11):e78515. doi: 10.1371/journal.pone.0078515. eCollection 2013.

Abstract

Serotonergic ligands have proven effective drugs in the treatment of migraine, pain, obesity, and a wide range of psychiatric and neurological disorders. There is a clinical need for more highly 5-HT2 receptor subtype-selective ligands and the most attention has been given to the phenethylamine class. Conformationally constrained phenethylamine analogs have demonstrated that for optimal activity the free lone pair electrons of the 2-oxygen must be oriented syn and the 5-oxygen lone pairs anti relative to the ethylamine moiety. Also the ethyl linker has been constrained providing information about the bioactive conformation of the amine functionality. However, combined 1,2-constriction by cyclization has only been tested with one compound. Here, we present three new 1,2-cyclized phenylethylamines, 9-11, and describe their synthetic routes. Ligand docking in the 5-HT2B crystal structure showed that the 1,2-heterocyclized compounds can be accommodated in the binding site. Conformational analysis showed that 11 can only bind in a higher-energy conformation, which would explain its absent or low affinity. The amine and 2-oxygen interactions with D3.32 and S3.36, respectively, can form but shift the placement of the core scaffold. The constraints in 9-11 resulted in docking poses with the 4-bromine in closer vicinity to 5.46, which is polar only in the human 5-HT2A subtype, for which 9-11 have the lowest affinity. The new ligands, conformational analysis and docking expand the structure-activity relationships of constrained phenethylamines and contributes towards the development of 5-HT2 receptor subtype-selective ligands.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Crystallography, X-Ray
  • Humans
  • Ligands
  • Molecular Docking Simulation*
  • Phenethylamines / chemistry*
  • Receptor, Serotonin, 5-HT2A / chemistry*
  • Receptor, Serotonin, 5-HT2B / chemistry*
  • Structure-Activity Relationship

Substances

  • Ligands
  • Phenethylamines
  • Receptor, Serotonin, 5-HT2A
  • Receptor, Serotonin, 5-HT2B

Grants and funding

VI and JP were supported by the Lundbeck- and DEG by the Carlsberg Foundations. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.