A potent new class of kappa-receptor agonist: 4-substituted 1-(arylacetyl)-2-[(dialkylamino)methyl]piperazines

J Med Chem. 1993 Jul 23;36(15):2075-83. doi: 10.1021/jm00067a004.


The synthesis of 4-substituted 1-(arylacetyl)-2-[(alkylamino)methyl]piperazines (10-22, 26, 27, and 30-33) and their activities as kappa-opioid receptor agonists are described. This includes a range of 4-acyl and 4-carboalkoxy derivatives with the latter series showing the greatest kappa-agonist activity. In particular, methyl 4-[(3,4-dichlorophenyl)acetyl]-3-[(1-pyrrolidinyl) methyl]-1-piperazinecarboxylate (18) displays exceptional potency and selectivity. It showed the following activities in functional in vitro assays: rabbit vas deferens (kappa-specific tissue) IC50 = 0.041 nM, rat vas deferens (mu-specific tissue) IC50 > 10,000 nM, and hamster vas deferens (delta-specific tissue) IC50 > 10,000 nM. Compound 18 is also a highly potent antinociceptive agent, as determined in the mouse acetylcholine-induced abdominal constriction test: ED50 = 0.000 52 mg/kg, sc. The activity of 18 resides solely in its 3(R)-enantiomer. The kappa-agonist activity in both the 4-acyl and the 4-carbamate series is sensitive to the size of the 4-substituent. In addition, it would appear that an appreciable negative electrostatic potential in this region of the molecule is an important requirement for optimal potency.

MeSH terms

  • Analgesics / chemical synthesis*
  • Analgesics / pharmacology
  • Animals
  • Cricetinae
  • Male
  • Mice
  • Molecular Conformation
  • Piperazines / chemical synthesis*
  • Piperazines / pharmacology
  • Pyrrolidines / chemical synthesis*
  • Pyrrolidines / pharmacology
  • Rabbits
  • Rats
  • Receptors, Opioid, kappa / drug effects*
  • Stereoisomerism
  • Structure-Activity Relationship
  • Vas Deferens / drug effects


  • Analgesics
  • Piperazines
  • Pyrrolidines
  • Receptors, Opioid, kappa
  • GR 89696