A series of 2-(substituted phenyl)-N-methyl-N-[(1S)-1-(substituted alkyl)-2-(1-(3-pyrrolinyl))ethyl]acetamides were synthesized and evaluated as highly selective kappa-agonists with K-i values in low nanomolar range. 3-Pyrroline incorporated into the basic amino functionality in combination with 2-(methylthio)ethyl substituent on the carbon adjacent to the amide nitrogen remarkably enhanced the K-selectivity. 3,4-Dichlorophenyl derivative le was found the most potent and selective analgesic in this series with ED50 value of 0.023 mg/kg. (C) 2002 Elsevier Science Ltd. All rights reserved.
A series of 2-(substituted phenyl)-N-methyl-N-[(1S)-1-(substituted alkyl)-2-(1-(3-pyrrolinyl))ethyl]acetamides were synthesized and evaluated as highly selective kappa-agonists with K-i values in low nanomolar range. 3-Pyrroline incorporated into the basic amino functionality in combination with 2-(methylthio)ethyl substituent on the carbon adjacent to the amide nitrogen remarkably enhanced the K-selectivity. 3,4-Dichlorophenyl derivative le was found the most potent and selective analgesic in this series with ED50 value of 0.023 mg/kg. (C) 2002 Elsevier Science Ltd. All rights reserved.