10-substituted 11-oxygenated (R)-aporphines: Synthesis, Pharmacology, and Modeling of 5-HT1A Receptor Interactions

J Med Chem. 1996 Aug 30;39(18):3491-502. doi: 10.1021/jm960188q.

Abstract

Derivatives of the selective serotonin 5-HT1A receptor agonist (R)-11-hydroxy-10-methylaporphine (2) having various substituents in the C10-position or at the nitrogen have been synthesized from natural morphine or 6-O-acetylcodeine, respectively. The C10-substituents were introduced using efficient Stille or Suzuki cross-coupling reactions. The compounds were evaluated for their affinities to 5-HT1A and dopamine (DA) D1 and D2A receptors in vitro. All compounds tested displayed low (micromolar) affinities to D1 and D2A receptors. In addition, changes in steric bulk and/or electronic properties of the C10-substituent as compared to a C10-methyl group, as well as substitution of the N-methyl group for a hydrogen or a larger N-alkyl group, produced a marked decrease in the affinities to 5-HT1A receptors. Selected compounds that displayed moderate to high affinities to 5-HT1A receptors were evaluated for their ability to stimulate 5-HT1A receptors in vivo. The evaluated compounds behaved as agonists at 5-HT1A receptors, except for the N-propyl analogue of 2, (R)-11-hydroxy-10-methyl-N-propylnoraporphine (23), which displayed weak DA receptor agonism at the doses tested. Hence, the substitution pattern of 2 (a C10-methyl, a C11-hydroxy, and an N-methyl group) appears to be optimal for potent interaction of 10,11-disubstituted (R)-aporphines with 5-HT1A receptors. Modeling of ligand-5-HT1A receptor interactions was performed in an attempt to rationalize the observed affinity data. The binding site model suggests the presence of a "methyl pocket" in the 5-HT1A receptor binding ste. The C11-methoxy-substituted aporphines appear to have a different binding mode compared to 2, implying a different accessibility of these compounds to the "methyl pocket".

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Humans
  • Male
  • Models, Molecular
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Serotonin / metabolism*
  • Serotonin Receptor Agonists / chemical synthesis*
  • Serotonin Receptor Agonists / metabolism
  • Serotonin Receptor Agonists / pharmacology
  • Structure-Activity Relationship

Substances

  • Receptors, Serotonin
  • Serotonin Receptor Agonists