Synthesis and opiate receptor binding properties of 17-methyl-6,7-dehydro-3,14-dihydroxy-4,5alpha-epoxy-6,7:4',5'-pyrimidin omorphinans

Synthesis of Illudinine from Dimedone and Identification of Activity as a Monoamine Oxidase Inhibitor

The fungal metabolite illudinine is prepared in seven steps and ca. 55% overall yield from dimedone using an "open and shut" (ring-opening and ring-closing) strategy. Tandem ring-opening fragmentation and olefination of dimedone establishes alkyne and vinylarene functionality linked by a neopentylene tether. Oxidative cycloisomerization then provides the illudinine framework. The key innovation in this second-generation synthesis of illudinine is the use of the nitrile functional group, rather than an ester, as the functional precursor to the carboxylic acid of illudinine. The small, linear nitrile (C≡N) is associated with improved selectivity, π-conjugation, and reactivity at multiple points in the synthetic sequence relative to the carboxylic acid ester. Preliminary assays indicate that illudinine and several related synthetic analogues are monoamine oxidase inhibitors, which is the first reported indication of biological activity associated with this natural product. Illudinine was found to inhibit monoamine oxidase B (MAO-B) with an IC₅₀ of 18 ± 7.1 μM in preliminary assays.

Synthesis of Illudinine from Dimedone

A total synthesis of the illudalane sesquiterpene illudinine was realized in eight steps and 14% overall yield from commercially available dimedone. The approach features tandem fragmentation/Knoevenagel-type condensation and microwave-assisted oxidative cycloisomerization to establish the isoquinoline core. Completion of the synthesis involves a recently reported cascade S_NAr/Lossen rearrangement on a densely functionalized aryl bromide and an optimized procedure for O-methylation of 8-hydroxyisoquinolines. The oxidative cycloisomerization proceeds by way of a novel inverse-demand intramolecular dehydro-Diels-Alder cycloaddition, which has a potentially broader appeal for preparing substituted isoquinolines.

Oxymorphone: a review

Oxymorphone (oxymorphone hydrochloride) (14-hydroxy-dihydromorphinone), a semisynthetic mu-opioid agonist, was first approved by the US Food and Drug Administration in 1959. Oxymorphone is considered a more potent opioid than its parent compound, morphine. Recently, an immediate-release and long-acting oral formulation of this drug was developed that makes oxymorphone a new option in treating moderate to severe pain. This article reviews the pharmacodynamics, pharmacology, and clinical efficacy for this new option in treating moderate to severe pain.

Novel ligands for the opioid receptors: synthesis and structure-activity relationships among 5'-aryl and 5'-heteroaryl 17-cyclopropylmethyl-4,5 alpha-epoxypyrido[2',3':6,7]morphinans

A series of pyridomorphinans possessing an aryl (10a-s) or heteroaryl (11a-h) substituent at the 5'-position of the pyridine ring of 17-cyclopropylmethyl-4,5 alpha-epoxypyrido[2',3':6,7]morphinan was synthesized and evaluated for binding and functional activity at the opioid delta, mu, and kappa receptors. All of these pyridomorphinans bound with higher affinity at the delta site than at mu or kappa sites. The binding data on isomeric compounds revealed that there exists greater bulk tolerance for substituents placed at the o-position of the phenyl ring than at m- or p-positions. Among the ligands examined, the 2-chlorophenyl (10l), 2-nitrophenyl (10n), 2-pyridyl (11a), and 4-quinolinyl (11g) compounds bound to the delta receptor with subnanomolar affinity. Compound 10c with the p-tolyl substituent displayed the highest mu/delta selectivity (ratio=42) whereas compound 10l with the 2-chlorophenyl substituent displayed the highest kappa/delta selectivity (ratio=23). At 10 microM concentration, the in vitro functional activity determined using [(35)S]GTP-gamma-S binding assays showed that all of the compounds were antagonists devoid of any significant agonist activity at the delta, mu, and kappa receptors. Antagonist potency determinations of three selected ligands revealed that the p-tolyl compound 10c is a potent delta selective antagonist. In the [(35)S]GTP-gamma-S assays this compound had a functional antagonist K(i) value of 0.2, 4.52, and 7.62 nM at the delta, mu, and kappa receptors, respectively. In the smooth muscle assays 10c displayed delta antagonist potency with a K(e) value of 0.88 nM. As an antagonist, it was 70-fold more potent at the delta receptors in the MVD than at the mu receptors in the GPI. The in vitro delta antagonist profile of this pyridomorphinan 10c resembles that of the widely used delta selective antagonist ligand naltrindole.

Antinociceptive properties of oxymorphazole in the mouse

Oxymorphazole (17-methyl-6,7-dehydro-3,14-dihydroxy-4,5 alpha-epoxy-6,7:3',4'-pyrazolomorphinan), a hydrophilic opioid, given intracerebroventricularly (2.5-50 nmol) or intrathecally (0.3-5 nmol) dose-dependently produced tail-flick inhibition in male CD-1 mice. However, oxymorphazole given subcutaneously even at high doses (10-80 mg/kg) produced weak tail-flick inhibition. Oxymorphazole given intraperitoneally (0.1 to 10 mg/kg) dose-dependently inhibited abdominal constriction response induced by intraperitoneally injection of 0.6% acetic acid. Oxymorphazole given intracerebroventricularly (25 nmol) or intrathecally (5 nmol) induced tail-flick inhibition was blocked by pretreatment with the mu-opioid receptor antagonist D-Phe-Cys-Tyr-D-Orn-Thr-Pen-Thr-NH2, but not kappa-opioid receptor antagonist nor-binaltrophimine. The delta-opioid receptor antagonist, naltrindole, blocked the tail-flick inhibition induced by oxymorphazole given intrathecally but not intracerebroventricularly. The inhibition of the abdominal constriction response by oxymorphazole given intraperitoneally was blocked by intraperitoneally pretreatment with naloxone, but not naltrindole or nor-binaltrophimine. Thus, oxymorphazole given systemically produces antinociception only with the abdominal constriction test, but not the tail-flick test, suggesting that it produces the antinociception at the peripheral sites when administered systemically. The oxymorphazole-induced antinociception is mainly mediated by the stimulation of mu-opioid receptors when given either centrally or systemically and also the delta-opioid receptors when given intrathecally. The lack of central antinociceptive effect of oxymorphazole given systemically may have interesting clinical implications.