Subtype-selective N-methyl-D-aspartate receptor antagonists: benzimidazalone and hydantoin as phenol replacements

Efficient heterogeneous catalysis by pendant metalloporphyrin-functionalized polythiophenes for the electrochemical reduction of carbon dioxide

Pendant metalloporphyrin-functionalized polythiophenes serve as efficient catalysts for the practical heterogeneous electrochemical reduction of carbon dioxide under ambient conditions in aqueous media.

Benzimidazolone bioisosteres of potent GluN2B selective NMDA receptor antagonists

Overactivation of the NMDA receptor is associated with excitotoxic events leading to neurodegenerative processes as observed during the development of Alzheimer's disease, ParFnson's disease, Chorea Huntington and epilepsy. Negative allosteric modulators addressing selectively the ifenprodil binding site of GluN2B subunit containing NMDA receptors are of major interest due to their neuroprotective potential accompanied by few side effects. Herein benzimidazolone bioisosteres of potent GluN2B antagonists 1-5 were designed and synthesized. A seven step sequence provided the central intermediate 19 in 28% yield. Elimination of water, methylation, epoxidation, epoxide rearrangement and finally reductive amination afforded the [7]annulenobenzimidazolone 30 with a 3-phenylpropylamino substituent in 6-position. Although 30 fits nicely into the pharmacophore of potent GluN2B antagonists, the gluN2B binding affinity of 30 was only moderate (Ki = 697 nM). Additionally, 30 shows low selectivity over the σ2 receptor (Ki = 549 nM). The moderate GluN2B affinity was explained by the rigid tricyclic structure of the [7]annulenobenzimidazolone 30.

Glutamate receptors as therapeutic targets for Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by motor symptoms including tremor and bradykinesia. The primary pathophysiology underlying PD is the degeneration of dopaminergic neurons of the substantia nigra pars compacta. Loss of these neurons causes pathological changes in neurotransmission in the basal ganglia motor circuit. The ability of ionotropic and metabotropic glutamate receptors to modulate neurotransmission throughout the basal ganglia suggests that these receptors may be targets for reversing the effects of altered neurotransmission in PD. Studies in animal models suggest that modulating the activity of these receptors may alleviate the primary motor symptoms of PD as well as side effects induced by dopamine replacement therapy. Moreover, glutamate receptor ligands may slow disease progression by delaying progressive dopamine neuron degeneration. Antagonists of NMDA receptors have shown promise in reversing motor symptoms, levodopa-induced dyskinesias, and neurodegeneration in preclinical PD models. The effects of drugs targeting AMPA receptors are more complex; while antagonists of these receptors exhibit utility in the treatment of levodopa-induced dyskinesias, AMPA receptor potentiators show promise for neuroprotection. Pharmacological modulation of metabotropic glutamate receptors (mGluRs) may hold even more promise for PD treatment due to the ability of mGluRs to fine-tune neurotransmission. Antagonists of mGluR5, as well as activators of group II mGluRs and mGluR4, have shown promise in several animal models of PD. These drugs reverse motor deficits in addition to providing protection against neurodegeneration. Glutamate receptors therefore represent exciting targets for the development of novel pharmacological therapies for PD.

Unambiguous structural characterization of hydantoin reaction products using 2D HMBC NMR spectroscopy

Data from two-dimensional (2D) NMR experiments were used to identify the reaction products resulting from the opening of pyroglutamates with isocyanates or thioisocyanates. The reaction has the potential to produce compounds that would have very similar one-dimensional proton ((1)H) or carbon-13 ((13)C) NMR spectra. Careful analysis of (1)H--(1)H COSY, (1)H--(1)H NOESY, and HMBC data, including chemical shifts and coupling constants, were used to distinguish correctly between carbamoyl-2-pyrrolidinone, hydantoin, and perhydro-1,3-diazepine-2,4-dione type structures that could result from this reaction. This work describes their preparation and subsequent identification using 2D NMR spectroscopy, and includes complete (13)C assignments of the reaction products. The 2D NMR techniques and analysis described here can be applied successfully to other synthetic reactions with the potential to produce isomeric products.

Ion channels involved in stroke

Ion channels are membrane proteins that flicker open and shut to regulate the flow of ions down their electrochemical gradient across the membrane and consequently regulate cellular excitability. Every living cell expresses ion channels, as they are critical life-sustaining proteins. Ion channels are generally either activated by voltage or by ligand interaction. For each group of ion channels the channels' molecular biology and biophysics will be introduced and the pharmacology of that group of channels will be reviewed. The in vitro and in vivo literature will be reviewed and, for ion channel groups in which clinical trials have been conducted, the efficacy and therapeutic potential of the neuroprotective compounds will be reviewed. A large part of this article will deal with glutamate receptors, focusing specifically on N-methyl-D-aspartate (NMDA) receptors. Although the outcome of clinical trials for NMDA receptor antagonists as therapeutics for acute stroke is disappointing, the culmination of these failed trials was preceded by a decade of efforts to develop these agents. Sodium and calcium channel antagonists will be reviewed and the newly emerging efforts to develop therapeutics targeting potassium channels will be discussed. The future development of stroke therapeutics targeting ion channels will be discussed in the context of the failures of the last decade in hopes that this decade will yield successful stroke therapeutics.

An MCASE approach to the search of a cure for Parkinson's Disease

BACKGROUND

Parkinson's disease is caused by a dopamine deficiency state in the fore brain area. Dopamine receptor agonists, MAO-B inhibitors, and N-Methyl-D-Aspartate (NMDA) receptor antagonists are known to have antiparkinson effect. Levodopa, a dopamine structural analog, is the best currently available medication for the treatment of Parkinsons disease. Unfortunately, it also induces side effects upon long administration time. Thus, multidrug therapy is often used, in which various adjuvants alleviate side effects of levodopa and enhance its antiparkinsonian action.

RESULTS

Computer models have been created for three known antiparkinson mechanisms using the MCASE methodology. New drugs for Parkinsons disease can be designed on the basis of these models. We also speculate that the presence of biophores belonging to different groups can be beneficial and designed some potential drugs along this line. The proposed compounds bear pharmacophores of MAO-B inhibitors, dopamine agonists and NMDA antagonists, which could synergistically enhance their antiparkinson effect.

CONCLUSIONS

The methodology could readily be expanded to other endpoints where drugs with multiple activity mechanisms would be desirable.

Solid-phase preparation of hydantoins through a new cyclization/cleavage step

An efficient process for the solid-phase synthesis of hydantoins has been developed. The amino acid starting material is anchored to the resin from its carboxylic acid end through formation of a very stable amide bond. After introduction of different functional groups, the cleavage/cyclization step can be performed in acidic or basic conditions.

(1S,2R)-1-Phenyl-2-[(S)-1-aminopropyl]-N,N-diethylcyclopropanecarboxamide (PPDC), a new class of NMDA-receptor antagonist: molecular design by a novel conformational restriction strategy

We have found that milnacipran, a clinically useful antidepressant due to its inhibition of the re-uptake of serotonin (5-HT) and noradrenaline, is also a non-competitive NMDA-receptor antagonist. Based on the cyclopropane structure of milnacipran, conformationally restricted analogs were designed and synthesized. Of these analogs, (1S,2R)-1-phenyl-2-[(S)-1-aminopropyl]-N,N-diethylcyclopropanecarboxamide (PPDC) is 30-fold stronger than milnacipran as an NMDA-receptor antagonist with virtually no inhibitory effect on the neurotransmitter re-uptake. PPDC was identified as a new class of NMDA-receptor antagonist because it has a mode of action different from that of the previous antagonists; it selectivly binds the GluRepsilon3/GluRzeta1 and GluRepsilon4/GluRzeta1 subtype receptors in an agonist-independent allosteric manner. Functional assays of PPDC with the Xenopus oocytes system and cultured mouse neurons under voltage-clamp conditions confirmed that it acts as a potent NMDA-receptor antagonist. PPDC effectively protected against NMDA-induced neurotoxicity in both cultured mouse cerebral cortex and delayed neuronal death in a gerbil ischemic model. It was also active in a reserpine-treated mouse Parkinsons disease model. Thus, PPDC may be a candidate for a clinically useful NMDA-receptor antagonist, since the development of previous NMDA-receptor antagonists as drugs has been hindered by various undesirable side effects.