Isothiocyanate-substituted kappa-selective opioid receptor ligands derived from N-methyl-N-[(1S)-1-phenyl-2-(1-pyrrolidinyl)ethyl] phenylacetamide

J Med Chem. 1994 Sep 2;37(18):2856-64. doi: 10.1021/jm00044a006.


The synthesis of isothiocyanate-substituted kappa-selective opioid ligands derived from N-methyl-N-[(1S)-1-phenyl-2-(1-pyrrolidinyl)ethyl]ethyl]phenylacetami de (8) and their effects in radioligand displacement assays are reported. Ligands 3-5 with the S-absolute configuration were prepared with the isothiocyanate functionality at the 2-, 3-, and 4-positions in the phenylacetamide aromatic ring. The 2-isothiocyanato-4,5-dichlorophenylacetamide 6 was prepared to evaluate the effect of 4,5-dichloro substitution in the same aromatic ring as the 2-isothiocyanate function. N-Methyl-N-[(1S)-1-(4-isothiocyanatophenyl)-2-(1-pyrrolidinyl) ethyl]-3,4-dichlorophenylacetamide (7), with the 4-isothiocyanate function in the 1-phenyl ring, was prepared for comparison with the other compounds in the series. Of the prepared ligands, 7 and 8 (IC50s congruent to 1.4-1.8 nM) were approximately equal in affinity with 2 (ICI-199,441), followed by 3 and 6. All of these compounds were more kappa-selective than 2, as well. The binding characteristics of 8 show that the previously reported 4,5-dichloro substitution is not required for high affinity and kappa-selectivity. All of the synthesized isothiocyanate-substituted ligands irreversibly inhibited radioligand binding to guinea pig brain membrane preparations, including compound 2 (ICI-199,441) which had no isothiocyanate functionality.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acetamides / chemical synthesis*
  • Acetamides / metabolism
  • Acetanilides / chemistry*
  • Animals
  • Binding, Competitive
  • Brain / metabolism
  • Guinea Pigs
  • In Vitro Techniques
  • Isothiocyanates / chemical synthesis
  • Isothiocyanates / metabolism
  • Radioligand Assay
  • Receptors, Opioid, kappa / metabolism*
  • Stereoisomerism


  • Acetamides
  • Acetanilides
  • Isothiocyanates
  • Receptors, Opioid, kappa
  • N-methyl-N-(1-phenyl-2-(1-pyrrolidinyl)ethyl)phenylacetamide