Gyula Simig

2,3-Benzodiazepine-type AMPA receptor antagonists and their neuroprotective effects

AMPA receptors are fast ligand-gated members of glutamate receptors in neuronal and many types of non-neuronal cells. The heterotetramer complexes are assembled from four subunits (GluR1-4) in region-, development- and function-selective patterns. Each subunit contains three extracellular domains (a large amino terminal domain, an agonist-binding domain and a transducer domain), and three transmembrane segments with a loop (pore forming domain), as well as the intracellular carboxy terminal tail (traffic and conductance regulatory domain). The binding of the agonist (excitatory amino acids and their derivatives) initiates conformational realignments, which transmit to the transducer domain and membrane spanning segments to gate the channel permeable to Na+, K+ and more or less to Ca2+. Several 2,3-benzodiazepines act as non-competitive antagonists of the AMPA receptor (termed also negative allosteric modulators), which are thought to bind to the transducer domains and inhibit channel gating. Analysing their effects in vitro, it has been possible to recognize a structure-activity relationship, and to describe the critical parts of the molecules involved in their action at AMPA receptors. Blockade of AMPA receptors can protect the brain from apoptotic and necrotic cell death by preventing neuronal excitotoxicity during pathophysiological activation of glutamatergic neurons. Animal experiments provided evidence for the potential usefulness of non-competitive AMPA antagonists in the treatment of human ischemic and neurodegenerative disorders including stroke, multiple sclerosis, Parkinsons disease, periventricular leukomalacia and motoneuron disease. 2,3-benzodiazepine AMPA antagonists can protect against seizures, decrease levodopa-induced dyskinesia in animal models of Parkinsons disease demonstrating their utility for the treatment of a variety of CNS disorders.

New practical synthesis of panomifene. The effect of 2-trifluoromethyl substituent on the stereoselectivity of dehydration of 1,1,2-triarylethanols

Abstract Highly stereoselective eliminations were achieved by acid-catalysed dehydration of 1-(4-alkoxy)-3,3,3-trifluoro-1,2-diphenylpropan-1-ols ( 10, 11, 15 ). The influence of the trifluoromethyl group on the stereochemistry of the elimination has been discussed. The observed high stereoselectivity has been applied to give a new, practical synthesis of antiestrogenic drug panomifene ( 1 ).

Optimization of (Arylpiperazinylbutyl)oxindoles Exhibiting Selective 5-HT7 Receptor Antagonist Activity

A series of (arylpiperazinylbutyl)oxindoles as highly potent 5-HT(7) receptor antagonists has been studied for their selectivity toward the 5-HT(1A) receptor and α(1)-adrenoceptor. Several derivatives exhibited high 5-HT(7)/5-HT(1A) selectivity, and the key structural factors for reducing undesired α(1)-adrenergic receptor binding have also been identified. Rapid metabolism, a common problem within this family of compounds, could be circumvented with appropriate substitution patterns on the oxindole carbocycle. Contrary to expectations, none of the compounds produced an antidepressant-like action in the forced swimming test in mice despite sufficiently high brain concentrations. On the other hand, certain analogues showed significant anxiolytic activity in two different animal models: the Vogel conflict drinking test in rats and the light-dark test in mice.

Ortho-selective metalation and electrophilic substitution of benzylamine derivatives

N-Pivaloylbenzylamines and derivs. [e.g., 2,4-R(MeO)C6H4CH2NHCOCMe3, I, R = H] undergo smooth ortho-metalation when treated with two equivs. of an organolithium reagent. Subsequent carboxylation or hydroxylation lead to a no. of products, e.g., I, R = CO2H, OH. [on SciFinder (R)]

8-Methoxyisoquinoline derivatives through ortho-selective metalation of 2-(3-methoxyphenyl)ethylamine

Butyllithium in Et2O smoothly metalates 3-MeOC6H4CH2CH2NHCOCMe3 at the ortho position flanked by the two substituents. Subsequent reaction with DMF followed by acid catalyzed cyclization and redn. gives 8-methoxy-1,2,3,4-tetrahydroisoquinoline (I). [on SciFinder (R)]

Medicinal chemistry of 5-HT5A receptor ligands: a receptor subtype with unique therapeutical potential.

Although the 5-HT(5) receptor subfamily was discovered more than 15 years ago, it is unambiguously the least known 5-HT receptor subtype. The G(i)/G(0)-mediated signal transduction and its intensive presence in raphe and other brainstem and pons nuclei suggest mechanisms similar to those of 5-HT(1) receptors, the ligands of which are already applied in the treatment of e.g. anxiety and migraine. In addition, a unique coupling and inhibition of adenosine diphosphate-ribosyl cyclase have also been described. High concentrations of 5-HT(5) receptor in other key regions including, e.g. locus coeruleus, nucleus of the solitary tract, arcuate and suprachiasmatic nuclei of the hypothalamus indicate a wide range of physiological effects, thus its ligands are potential drug candidates in various areas, e.g. anxiety, sleep, incontinence, food intake, learning and memory, pain or chemoreception pathways. These findings have motivated several institutes and pharmaceutical companies to participate in the research of this field. Despite extensive research, no selective agonist and only two selective antagonists have been identified until now. Beyond these compounds, the present review provides a complete overview on all other published 5-HT(5A) receptor ligands as well as on the structure, function, distribution, genetics and possible therapeutic applications of this receptor.

A novel GABAA alpha 5 receptor inhibitor with therapeutic potential

Novel 2,3-benzodiazepine and related isoquinoline derivatives, substituted at position 1 with a 2-benzothiophenyl moiety, were synthesized to produce compounds that potently inhibited the action of GABA on heterologously expressed GABAA receptors containing the alpha 5 subunit (GABAA α5), with no apparent affinity for the benzodiazepine site. Substitutions of the benzothiophene moiety at position 4 led to compounds with drug-like properties that were putative inhibitors of extra-synaptic GABAA α5 receptors and had substantial blood-brain barrier permeability. Initial characterization in vivo showed that 8-methyl-5-[4-(trifluoromethyl)-1-benzothiophen-2-yl]-1,9-dihydro-2H-[1,3]oxazolo[4,5-h][2,3]benzodiazepin-2-one was devoid of sedative, pro-convulsive or motor side-effects, and enhanced the performance of rats in the object recognition test. In summary, we have discovered a first-in-class GABA-site inhibitor of extra-synaptic GABAA α5 receptors that has promising drug-like properties and warrants further development.

An easy and versatile access to 8-substituted isoquinolines

Lithiation of N-(2,2-diethoxyethyl)benzylamines I (R = Me, PhCH2) and reaction with electrophiles followed by acid-catalyzed cyclization leads to isoquinolines II (R1 = Me, MeO, CH2OH, MeS, Cl, Br, iodo) in 37-75% yield. [on SciFinder (R)]

Three complementary methods offering access to 5-substituted 1,2,3,4-tetrahydroisoquinolines

The scope and limitations of three independent, though related routes leading to 5-substituted tetrahydroisoquinolines are explored: the Pictet-Spengler type cyclization of ortho-substituted 2-phenylethylamines, the Pomeranz-Fritsch type cyclization of meta-substituted benzylamines and the electrophilic trapping of 5-lithiated 4-lithiooxytetrahydroquinolines. The introduction of the substituent relies in all three cases on a neighboring group assisted, site selective metalation step. [on SciFinder (R)]

Synthesis of 1,3-di[alkoxy(aryloxy)carbonyl]-2-oxo-2,3-dihydroindoles

Abstract Two protocols have been developed for the synthesis of 1,3-di[alkoxy(aryloxy)carbonyl]-2-oxo-2,3-dihydroindoles starting from the corresponding N,O-diacyl derivatives obtained by treatment of 2-oxindoles with chloroformic acid esters and triethylamine. The first is rearrangement of N,O-diacylated compounds in the presence of 4-dimethylaminopyridine to give N,C(3)-diacylated products with identical acyl groups in the two positions. The second involves O-deacylation of the N,O-diacylated compounds, followed by O-acylation and rearrangement resulting N,C(3)-diacylated 2-oxindoles with different acyl groups in the two positions.