Combination of two pharmacophoric systems: synthesis and pharmacological evaluation of spirocyclic pyranopyrazoles with high σ₁ receptor affinity

J Med Chem. 2011 Oct 13;54(19):6704-13. doi: 10.1021/jm200585k. Epub 2011 Sep 16.

Abstract

The novel class of spirocyclic σ(1) ligands 3 (6',7'-dihydro-1'H-spiro[piperidine-4,4'-pyrano[4,3-c]pyrazoles]) was designed by the combination of the potent σ(1) ligands 1 and 2 in one molecule. Thorough structure affinity relationships were derived by the variation of the substituents in position 1', 1, and 6'. Whereas the small electron rich methylpyrazole heterocycle was less tolerated by the σ(1) receptor protein, the introduction of a phenyl substituent instead of the methyl group led to ligands with a high σ(1) affinity. It is postulated that the additional phenyl substituent occupies a previously unrecognized hydrophobic region of the σ(1) receptor resulting in additional lipophilic interactions. The spirocyclic pyranopyrazoles are very selective against the σ(2) subtype, the PCP binding site of the NMDA receptor, and further targets. Despite high σ(1) affinity, the cyclohexylmethyl derivative 17i (K(i) (σ(1)) = 0.55 nM) and the isopentenyl derivative 17p (K(i) (σ(1)) = 1.6 nM) showed only low antiallodynic activity in the capsaicin assay.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analgesics / chemical synthesis*
  • Analgesics / chemistry
  • Analgesics / pharmacology
  • Animals
  • Brain / metabolism
  • Guinea Pigs
  • Hyperalgesia / drug therapy
  • In Vitro Techniques
  • Liver / metabolism
  • Mice
  • Pyrans / chemical synthesis*
  • Pyrans / chemistry
  • Pyrans / pharmacology
  • Pyrazoles / chemical synthesis*
  • Pyrazoles / chemistry
  • Pyrazoles / pharmacology
  • Radioligand Assay
  • Rats
  • Receptors, Opioid, delta / antagonists & inhibitors
  • Receptors, Opioid, delta / metabolism*
  • Spiro Compounds / chemical synthesis*
  • Spiro Compounds / chemistry
  • Spiro Compounds / pharmacology
  • Structure-Activity Relationship
  • Touch

Substances

  • Analgesics
  • Pyrans
  • Pyrazoles
  • Receptors, Opioid, delta
  • Spiro Compounds