Synthesis, X-ray crystallographic determination, and opioid activity of erythro-5-methylmethadone enantiomers. Evidence which suggests that mu and delta opioid receptors possess different stereochemical requirements

Syntheses of (R)- and (S)-2- and 6-fluoronorepinephrine and (R)- and (S)-2- and 6-fluoroepinephrine: effect of stereochemistry on fluorine-induced adrenergic selectivities

Several routes to the enantiomers of fluoronorepinephrines (1) and fluoroepinephrines (2) were explored. A catalytic enantioselective oxazaborolidine reduction and a chiral (salen)Ti(IV) catalyzed asymmetric synthesis of silyl cyanohydrins proved efficacious in the key stereo-defining steps of two respective routes. Binding studies of the catecholamines with alpha(1)-, alpha(2)-, beta(1)-, and beta(2)-adrenergic receptors were examined. The assays confirmed that fluorine substitution had marked effects on the affinity of (R)-norepinephrine and (R)-epinephrine for adrenergic receptors, depending on the position of substitution. Thus, a fluoro substituent at the 2-position of (R)-norepinephrine and (R)-epinephrine reduced activity at both alpha(1)- and alpha(2)-receptors and enhanced activity at beta(1)- and beta(2)-receptors, while fluorination at the 6-position reduced activity at the beta(1)- and beta(2)-receptors. The effects of fluorine substitution on the S-isomers were less predictable.

Synthesis, biological activity, and absolute stereochemical assignment of NPS 1392: a potent and stereoselective NMDA receptor antagonist

The synthesis, biological activity, and single crystal X-ray structure of NPS 1392, (R)-(-)-3,3-bis(3-fluorophenyl)-2-methylpropan-1-amine (3a), a potent, stereoselective antagonist of the NMDA receptor, are described. The NMDA receptor selectively bound the levo isomer (3a) over its enantiomer (3b), which prompted a rigorous absolute configuration assignment. NPS 1392 has the R configuration based on the single-crystal X-ray diffraction analysis of the hydroiodide salt of NPS 1392. This compound is a potential neuroprotective agent for use in the treatment of ischemic stroke.

Phenyl-substituted normethadones: synthesis and pharmacology

Phenyl-substituted normethadone derivatives were synthesized and their affinity (IC50) for opioid receptors was determined by displacement of the specific binding sites of [3H]sufentanyl on rat brain preparations. Substitution resulted in a decrease of affinity in-vitro. These results suggest that normethadone-like compounds may interact with the P subsite of the mu-opioid receptor and that the P subsite has a well-defined cavity shape of stringent dimensions.

Methadone conformation and opioid activity

The inactive methadone analog threo-5-methylmethadone has a solid-state conformation in which the nitrogen is antiperiplanar to the tertiary carbon C(4). Since threo-5-methylmethadone exhibits no opioid agonism either in vivo or in vitro, methadone analogs probably do not have this conformation when bound to an opioid receptor. The potent agonist (-)-erythro-5-methylmethadone has a solid-state conformation in which the nitrogen atom is rotated back toward the phenyl rings on the quarternary carbon, suggesting that this unusual conformation is the active one.