enkephalin--leucine-2-alanine and 3-methylfentanyl-isothiocyanate

Recently we reported the synthesis of the first enantiomeric pair of irreversible opioid ligands [(3S,4R)-(-)- and (3R,4S)-(+)-cis-4, SUPERFIT] and specific interaction of the latter with the delta receptor. Here we report another enantiomeric pair of irreversible opioid ligands, (+)-trans- and (-)-trans-3-methylfentanyl isothiocyanates [(3S,4S)-(+)-trans- and (3R,4R)-(-)-trans-4]. A single-crystal X-ray analysis of the 2,4,6-trinitrobenzenesulfonic acid salt of (+)-trans-3-methyl-N-phenyl-4-piperidinamine [(+)-trans-8] revealed it (and, therefore, 4) to have the trans configuration and the absolute configuration of (+)-trans-8 to be 3S,4S. The (+)-trans enantiomer of 4 was shown to be highly potent and about 10-fold more selective as an acylating agent than (-)-trans-4 for the higher affinity [3H]DADL (delta) binding site in rat brain membranes. In that assay, (+)-trans-4 and (+)-cis-4 were essentially equipotent as affinity ligands, and the levo enantiomers were considerably less potent. (+)-trans-4 was, thus, a potent, subtype-selective acylating agent for the delta opioid receptor in vitro. With membranes from NG108-15 neuroblastoma x glioma hybrid cells, containing only delta receptors, (+)-cis-4 was found to be a little more potent than (+)-trans-4. Similarly, (+)-cis-4 is the most effective inhibitor of adenylate cyclase in these membranes, (+)-trans-4 has weak activity, and the levo enantiomers are inactive. Only (+)-cis-4 was found to have antinociceptive activity in vivo.

Topics: Acylation; Adenylyl Cyclase Inhibitors; Analgesia; Animals; Brain; Cell Membrane; Chemical Phenomena; Chemistry; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Enkephalins; Fentanyl; Glioma; Hybrid Cells; Indicators and Reagents; Ligands; Male; Molecular Structure; Neuroblastoma; Rats; Rats, Inbred Strains; Receptors, Opioid; Receptors, Opioid, delta; Stereoisomerism; Structure-Activity Relationship; Tumor Cells, Cultured

SuperFIT is an high affinity acylating ligand derived from fentanyl. Previous studies suggested that a selective acylation of delta receptors (J. Med. Chem. 29:1087-1093, 1986) resulted from exposure of membranes to this and structurally related compounds. We report in this preliminary study that intracerebroventricular administration of either superFIT or its enantiomer 18 to 24 hours prior to sacrifice decreased the subsequent binding of [3H]DADL to both its higher and lower affinity binding sites.

Topics: Acylation; Animals; Cerebral Ventricles; Enkephalin, Leucine; Enkephalin, Leucine-2-Alanine; Fentanyl; Indicators and Reagents; Injections, Intraventricular; Male; Rats; Rats, Inbred Strains; Receptors, Opioid; Stereoisomerism