Synthesis and biological evaluation of 4-(aminomethyl)-1-hydroxypyrazole analogues of muscimol as γ-aminobutyric acid(a) receptor agonists

J Med Chem. 2013 Feb 14;56(3):993-1006. doi: 10.1021/jm301473k. Epub 2013 Jan 23.

Abstract

A series of bioisosteric 4-(aminomethyl)-1-hydroxypyrazole (4-AHP) analogues of muscimol, a GABA(A) receptor agonist, has been synthesized and pharmacologically characterized at native and selected recombinant GABA(A) receptors. The unsubstituted 4-AHP analogue (2a) (EC(50) 19 μM, R(max) 69%) was a moderately potent agonist at human α(1)β(2)γ(2) GABA(A) receptors, and in SAR studies substitutions in the 3- and/or 5-position were found to be detrimental to binding affinities. Ligand-receptor docking in an α(1)β(2)γ(2) GABA(A) receptor homology model along with the obtained SAR indicate that 2a and muscimol share a common binding mode, which deviates from the binding mode of the structurally related antagonist series based on 4-(piperidin-4-yl)-1-hydroxypyrazole (4-PHP, 1). Selectivity for α(1)β(2)γ(2) over ρ(1) GABA(A) receptors was observed for the 5-chloro, 5-bromo, and 5-methyl substituted analogues of 2a illustrating that even small differences in structure can give rise to subtype selectivity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Computer Simulation
  • GABA-A Receptor Agonists / chemical synthesis
  • GABA-A Receptor Agonists / pharmacology*
  • Magnetic Resonance Spectroscopy
  • Models, Molecular
  • Muscimol / analogs & derivatives*
  • Muscimol / chemical synthesis
  • Muscimol / pharmacology
  • Spectrometry, Mass, Electrospray Ionization
  • Structure-Activity Relationship

Substances

  • GABA-A Receptor Agonists
  • Muscimol