Antiseizure Activity of Novel γ-Aminobutyric Acid (A) Receptor Subtype-Selective Benzodiazepine Analogues in Mice and Rat Models

The antiseizure activity of benzodiazepines (BDZs) 1-5 in mice and rats as animal models is described. These BDZs have selective efficacy for α2β3γ2 and α3β3γ2 GABAA-receptors. Significant anticonvulsant activity with little or no motor impairment and therapeutic indexes (TI) of 2.8-44 (mice, ip) were observed for compounds 2-4 in the subcutaneous metrazole seizure (scMET) test. In rats orally (po) the TI was >5 to 105. These compounds represent novel leads in the search for anticonvulsants devoid of sedative, ataxic and amnestic side effects

Novel positive allosteric modulators of GABAA receptors: Do subtle differences in activity at alpha 1 plus alpha 5 versus alpha 2 plus alpha 3 subunits account for dissimilarities in behavioral effects in rats?

Over the last years, genetic studies have greatly improved Our knowledge on the receptor subtypes mediating various pharmacological effects of positive allosteric modulators at GABA(A) receptors. This stimulated the development of new benzodiazepine (BZ)-like ligands, especially those inactive/low-active at GABA(A) receptors containing the alpha(1) subunit, with the aim of generating more selective drugs. Hereby, the affinity and efficacy of four recently synthesized BZ site ligands: SH-053-2'N, SH-053-S-CH3-2'F, SH-053-R-CH3-2'F and JY-XHe-053 were assessed. They were also studied in behavioral tests of spontaneous locomotor activity, elevated plus maze, and water maze in rats, which are considered predictive of. respectively, the sedative, anxiolytic, and amnesic influence of BZs. The novel ligands had moderately low to low affinity and mild to partial agonistic efficacy at GABA(A) receptors containing the a, subunit, with variable, but more pronounced efficacy at other BZ-sensitive binding sites. While presumably alpha(1) receptor-mediated sedative effects of GABA(A) modulation were not fully eliminated with any of the ligands tested, only SH-053-2'N and SH-053-S-CH3-2'F, both dosed at 30 mg/kg, exerted anxiolytic effects. The lack of clear anxiolytic-like activity of JY-XHe-053, despite its efficacy at alpha(2)- and alpha(3)-GABA(A) receptors, may have been partly connected with its preferential affinity at alpha(5)-GABA(A) receptors coupled with weak agonist activity at alpha(1)-containing subtypes. The memory impairment in water-maze experiments, generally reported with BZ site agonists, was completely circumvented with all four ligands. The results suggest that a substantial amount of activity at a I GABA(A) receptors is needed for affecting spatial learning and memory impairments, while much weaker activity at alpha(1) and alpha(5)-GABA(A) receptors is sufficient for eliciting sedation

Novel positive allosteric modulators of GABAA receptors: Do subtle differences in activity at α1 plus α5 versus α2 plus α3 subunits account for dissimilarities in behavioral effects in rats?

Over the last years, genetic studies have greatly improved our knowledge on the receptor subtypes mediating various pharmacological effects of positive allosteric modulators at GABAA receptors. This stimulated the development of new benzodiazepine (BZ)-like ligands, especially those inactive/low-active at GABAA receptors containing the α1 subunit, with the aim of generating more selective drugs. Hereby, the affinity and efficacy of four recently-synthesized BZ site ligands: SH-053-2’N, SH-053-S-CH3-2’F, SH-053-R-CH3-2’F and JY-XHe-053 were assessed. They were also studied in behavioral tests of spontaneous locomotor activity, elevated plus maze, and water maze in rats, which are considered predictive of, respectively, the sedative, anxiolytic, and amnesic influence of BZs. The novel ligands had moderately low to low affinity and mild to partial agonistic efficacy at GABAA receptors containing the α1 subunit, with variable, but more pronounced efficacy at other BZ-sensitive binding sites. While presumably α1 receptor-mediated sedative effects of GABAA modulation were not fully eliminated with any of the ligands tested, only SH-053-2’N and SH-053-S-CH3-2’F, both dosed at 30 mg/kg, exerted anxiolytic effects. The lack of clear anxiolytic-like activity of JY-XHe-053, despite its efficacy at α2- and α3-GABAA receptors, may have been partly connected with its preferential affinity at α5-GABAA receptors coupled with weak agonist activity at α1-containing subtypes. The memory impairment in water-maze experiments, generally reported with BZ site agonists, was completely circumvented with all four ligands. The results suggest that a substantial amount of activity at α1 GABAA receptors is needed for effecting spatial learning and memory impairments, while much weaker activity at α1- and α5-GABAA receptors is sufficient for eliciting sedation

Anxiolytic-like effects of 8-acetylene imidazobenzodiazepines in a rhesus monkey conflict procedure

Conflict procedures can be used to study the receptor mechanisms underlying the anxiolytic effects of benzodiazepines and other GABAA receptor modulators. In the present study, we first determined the efficacy and binding affinity of the benzodiazepine diazepam and recently synthesized GABAA receptor modulators JY-XHe-053, XHe-II-053, HZ-166, SH-053-2'F-S-CH3 and SH-053-2'F-R-CH3 at GABAA receptors containing α1, α2, α3 and α5 subunits. Results from these studies suggest that each compound displayed lower efficacy at GABAA receptors containing α1 subunits and varying degrees of efficacy and affinity at GABAA receptors containing α2, α3 and α5 subunits. Next, we assessed their anxiolytic effects using a rhesus monkey conflict procedure in which behavior was maintained under a fixed-ratio schedule of food delivery in the absence (non-suppressed responding) and presence (suppressed responding) of response-contingent electric shock. Relatively non-selective compounds, such as diazepam and JY-XHe-053 produced characteristic increases in rates of suppressed responding at low to intermediate doses and decreased the average rates of non-suppressed responding at higher doses. XHe-II-053 and HZ-166 also produced increases in suppressed responding at low to intermediate doses, but were ineffective at decreasing rates of non-suppressed responding, consistent with their relatively low efficacy at GABAA receptors containing α1 and α5 subunits. In contrast, SH-053-2’F-S-CH3 and SH-053-2’F-R-CH3 produced only partial increases in suppressed responding and were ineffective on non-suppressed responding, consistent with their profiles as partial agonists at GABAA receptors containing α2, α3 and α5 subunits. These behavioral effects suggest that the anxiolytic and rate-reducing effects of GABAA receptor positive modulators are dependent on their relative efficacy and affinity at different GABAA receptor subtypes

Barberou

Dictionnaire Gustave Flaubert, sous la direction d’Éric Le Calvez [avec la collaboration d’A. Carrico, M. F. Davì Trimarchi, S. Dord-Crouslé, A. Herschberg Pierrot, C. Ippolito, É. Le Calvez, B. Magaudda, S. Mangiapane, K. Matsuzawa, R. M. Palermo Di Stefano, F. Pellegrini, N. Petibon, T. Poyet, J. Thomas et F. Vatan] ; Classiques Garnier, 2017 ; coll. Dictionnaires et synthèses ; 1259 page

Stereospecific Approach to the Synthesis of Ring‑A Oxygenated <i>Sarpagine</i> Indole Alkaloids. Total Synthesis of the Dimeric Indole Alkaloid <i>P</i>‑(+)-Dispegatrine and Six Other Monomeric Indole Alkaloids

The first regio- and stereocontrolled total synthesis of the bisphenolic, bisquaternary alkaloid (+)-dispegatrine (<b>1</b>) has been accomplished in an overall yield of 8.3% (12 reaction vessels) from 5-methoxy-d-tryptophan ethyl ester (<b>17</b>). A crucial late-stage thallium­(III) mediated intermolecular oxidative dehydrodimerization was employed in the formation of the C9–C9′ biaryl axis in <b>1</b>. The complete stereocontrol observed in this key biaryl coupling step is due to the asymmetric induction by the natural <i>sarpagine</i> configuration of the monomer lochnerine (<b>6</b>) and was confirmed by both the Suzuki and the oxidative dehydrodimerization model studies on the tetrahydro β-carboline (<b>35</b>). The axial chirality of the lochnerine dimer (<b>40</b>) and in turn dispegatrine (<b>1</b>) was established by X-ray crystallography and was determined to be <i>P</i>(S). Additionally, the first total synthesis of the monomeric indole alkaloids (+)-spegatrine (<b>2</b>), (+)-10-methoxyvellosimine (<b>5</b>), (+)-lochnerine (<b>6</b>), lochvinerine (<b>7</b>), (+)-sarpagine (<b>8</b>), and (+)-lochneram (<b>11</b>) were also achieved via the common pentacyclic intermediate <b>16</b>

Enantioselective Intermolecular [2 + 2 + 2] Cycloadditions of Ene–Allenes with Allenoates

An enantioselective [2 + 2 + 2] cycloaddition of ene–allenes with allenoates is described, which transforms simple π-components into stereochemically complex carbocycles in a single step. The rhodium(I)-catalyzed cycloaddition proceeds with good levels of enantioselectivity, and with high levels of regio-, chemo-, and diastereoselectivity. Our results are consistent with a mechanism involving an enantioselective intermolecular allene–allene oxidative coupling

Brønsted Acid Mediated Cyclization of Enaminones. Rapid and Efficient Access to the Tetracyclic Framework of the <i>Strychnos</i> Alkaloids

The development of an efficient diastereoselective method that permits rapid construction of the tetracyclic core <b>17</b> of the <i>Strychnos</i>-<i>Aspidosperma</i> alkaloids is described. Enaminone <b>16</b>, synthesized in high yield, has been cyclized under the influence of a Brønsted acid to provide the core tetracyclic framework <b>17</b> of the <i>Strychnos</i> alkaloids in optically active form or alternatively to the β-ketoester tetrahydro-β-carboline (THBC) unit <b>18</b>, by varying the equivalents of acid and the molar concentration. Attempts to utilize <b>18</b> to form the C(7)–C(16) bond of the akuammiline related alkaloids represented by strictamine (<b>22</b>), using metal-carbenoid chemistry, are also described

Anxiolytic-like effects of 8-acetylene imidazobenzodiazepines in a rhesus monkey conflict procedure

Conflict procedures can be used to study the receptor mechanisms underlying the anxiolytic effects of benzodiazepines and other GABA(A) receptor modulators. In the present study, we first determined the efficacy and binding affinity of the benzodiazepine diazepam and recently synthesized GABA(A) receptor modulators JY-XHe-053, XHe-II-053, HZ-166, SH-053-2'F-S-CH(3) and SH-053-2'F-R-CH(3) at GABA(A) receptors containing α1, α2, α3 and α5 subunits. Results from these studies suggest that each compound displayed lower efficacy at GABA(A) receptors containing α1 subunits and varying degrees of efficacy and affinity at GABA(A) receptors containing α2, α3 and α5 subunits. Next, we assessed their anxiolytic effects using a rhesus monkey conflict procedure in which behavior was maintained under a fixed-ratio schedule of food delivery in the absence (non-suppressed responding) and presence (suppressed responding) of response-contingent electric shock. Relatively non-selective compounds, such as diazepam and JY-XHe-053 produced characteristic increases in rates of suppressed responding at low to intermediate doses and decreased the average rates of non-suppressed responding at higher doses. XHe-II-053 and HZ-166 also produced increases in suppressed responding at low to intermediate doses, but were ineffective at decreasing rates of non-suppressed responding, consistent with their relatively low efficacy at GABA(A) receptors containing α1 and α5 subunits. In contrast, SH-053-2’F-S-CH(3) and SH-053-2’F-R-CH(3) produced only partial increases in suppressed responding and were ineffective on non-suppressed responding, consistent with their profiles as partial agonists at GABA(A) receptors containing α2, α3 and α5 subunits. These behavioral effects suggest that the anxiolytic and rate-reducing effects of GABA(A) receptor positive modulators are dependent on their relative efficacy and affinity at different GABA(A) receptor subtypes