Tautomerism and Physical Properties of Pyrido[1,2-a]benzimidazole (PBI) GABA-A Receptor Ligands (original) (raw)
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2020
It is of interest to study the binding capacity of "3-[2-(2-Amino-1H-benzo[d]imidazol-1-yl)ethyl]-1,3-oxazolidin-2-one" (OXB2) with the active site of gamma-aminobutyric acid (GABA) located in the GABA type A receptor (GABAAR) in comparison with different GABAA subtypes. Optimal binding features were observed with the α2β2γ2 isoform (-8 kcal/mol). This is similar (-7.3 and -7.2 kcal/mol, respectively) for subtypes (α3β2γ2 and α1β2γ2). This implies that OXB2 binds preferentially to subtypes associated with anxiety (α2- and/or α3-containing receptors) linked molecules than with the subtype associated with sedation (α1-containing receptors). It is further noted that molecular dynamics simulation data of the complex (OXB2-GABAAR) shows adequate structural stability in aqueous environment. Moreover, relevant ADMET data is found adequate for further consideration.
Journal of Medicinal Chemistry, 2005
A series of new 1,2-diphenylimidazole derivatives (1a-x) were synthesized and evaluated for their ability to potentiate γ-aminobutyric acid (GABA)-evoked currents in Xenopus laevis oocytes expressing recombinant human GABA A receptors. Many of these compounds enhanced GABA action with potencies (EC 50) 0.19-19 µM) and efficacies (maximal efficacies of up to 640%) similar to or greater than those of anesthetics such as etomidate, propofol, and alphaxalone. Structure-activity relationship analysis revealed that the presence of an ester moiety in the imidazole ring was required for full agonist properties, while modifications made in the phenyl rings affected potency and efficacy, with ethyl 2-(4-bromophenyl)-1-(2,4-dichlorophenyl)-1H-4-imidazolecarboxylate showing the highest potency. These compounds potentiated the [ 3 H]-GABA binding to rat brain membranes, suggesting a site of interaction different from that of GABA. As for etomidate, mutation of asparagine-265 in the 2 subunit of the GABA A receptor into serine reduced the ability of derivative 1i to modulate the GABA function.
Differential modulation of GABAA receptor function by aryl pyrazoles
European Journal of Pharmacology, 2014
Several aryl pyrazoles characterized by a different molecular structure (flexible vs constrained), but chemically related to rimonabant and AM251, were tested for their ability to modulate the function of recombinant α 1 β 2 γ 2L GABA A receptors expressed in Xenopus laevis oocytes. The effects of 6Bio-R, 14Bio-R, NESS 0327, GP1a and GP2a (0.3-30 μM) were evaluated using a two-electrode voltage-clamp technique. 6Bio-R and 14Bio-R potentiated GABA-evoked Cl À currents. NESS 0327, GP1a and GP2a did not affect the GABA A receptor function, but they acted as antagonists of 6Bio-R. Moreover, NESS 0327 inhibited the potentiation of the GABA A receptor function induced by rimonabant. The benzodiazepine site seems to participate in the action of these compounds. In fact, flumazenil antagonized the potentiation of the GABA A receptor induced by 6Bio-R, and NESS 0327 reduced the action of lorazepam and zolpidem. On the contrary, NESS 0327 did not antagonize the action of "classic" GABAergic modulators (propanol, anesthetics, barbiturates or steroids). In α 1 β 2 receptors 6Bio-R potentiated the GABAergic function, but flumazenil was still able to antagonize the potentiation induced by 6Bio-R. Aryl pyrazole derivatives activity at the GABA A receptor depends on their molecular structure. These compounds bind to both an αβγ binding site, and to an α⧸β site which do not require the γ subunit and that may provide structural leads for drugs with potential anticonvulsant effects.
Bioorganic & Medicinal Chemistry, 2010
In this and previous studies we investigated the importance of partial structures of Telmisartan on PPARc activation. The biphenyl-4-ylmethyl moiety at N1 and residues at C2 of the central benzimidazole were identified to be essential for receptor activation and potency of receptor binding. Now we focused our attention on positions 5 and 6 of the central benzimidazole and introduced bromine (3b-5/6, 3c), phenylcarbonyl (3d-5/6), hydroxy(phenyl)methyl (3g-5/6), hydroxymethyl (3h-5/6) and formyl (3i) groups. The selection of these moieties was inspired by the structure of Losartan and its metabolite EXP3179. In order to increase the hydrophobicity of the central part of the molecule, the benzimidazole was exchanged by a naphtho[2,3-d]imidazole (5). The compounds 3a-3i and 5 were tested in a differentiation assay using 3T3-L1 preadipocytes and a luciferase assay using COS-7 cells, transiently transfected with pGal4-hPPARcDEF, pGal5-TK-pGL3 and pRL-CMV, as established models for the assessment of cellular PPARc activation. An enhanced effect on PPARc activation could be observed if lipophilic moieties are introduced in these positions. 4 0 -[(2-Propyl-1H-naphtho[2,3-d]imidazol-1-yl)methyl]biphenyl-2-carboxylic acid (5) was identified as the most potent compound with an EC 50 of 0.26 lM and the profile of a full agonist.
Bioorganic & Medicinal Chemistry, 2011
The pharmacophoric model using ADLR procedure, based on pyrazolo [5,1-c][1,2,4]benzotriazine system, studied in our laboratory, allowed us to identify the essential interaction points (HBp-1, HBp-2, and Lp-1) and the important areas for affinity modulation (HBp-3 and Lp-2) for binding recognition at benzodiazepine (Bzs) site of GABA A receptors (GABA A -Rs). In this work ADLR method is used to rationalize the affinity data of 23 new compounds and to improve the knowledge on HBp-3 area, hydrogen bond area. Among these new compounds emerge the pyrrolo derivatives (18, 25, 28, 34, and 37) for their good affinity value (14.9 > K i (nM) > 63.0). In the orientations proposed by ADLR, the NH moiety of the pyrrole ring, independently of the position in the pyrazolobenzotriazine core, fits in HBp-3 area and points out the acceptor feature of this hydrogen bond area, already known as donor area. Unexpectedly, the oxygen atom of the furane ring does not form efficient hydrogen bond with the same area, probably for an imperfect distance. The size of substituent at position 8 is important but not necessary for the receptor recognition, in fact the interdependence between the features of the 3-and 8-substituent's is again verified, (i.e., compound 20 vs 32).
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The isosteric replacement of the benzene with thiophene ring is a chemical modification widely applied in medicinal chemistry. Several drugs containing the thiophene ring are marketed for treating various pathologies (osteoporosis, peripheral artery disorder, psychosis, anxiety and convulsion). Taking into account this evidence and as a continuation of our study in the GABAA receptor modulators field, we designed and synthesized new compounds containing the thiophene ring with 4,5-dihydro-5-oxo-pyrazolo[1,5-a]thieno[2,3-c]pyrimidine and pyrazolo[1,5-a]thieno[2,3-c] pyrimidine scaffold. Moreover, these cores, never reported in the literature, are isosteres of pyrazolo[1,5-a]quinazolines (PQ), previously published by us as GABAAR subtype ligands. We introduced in the new scaffold those functions and groups (esters, ketones, alpha/beta-thiophene) that in our PQ derivatives were responsible for the activity, and at the same time, we have extensively investigated the reactivity of the ne...
International Journal of Molecular Sciences
As a continuation of our study in the GABAA receptor modulators field, we report the design and synthesis of new 8-chloropyrazolo[1,5-a]quinazoline derivatives. Molecular docking studies and the evaluation of the ‘Proximity Frequencies’ (exploiting our reported model) were performed on all the final compounds (3, 4, 6a–c, 7a,b, 8, 9, 12a–c, 13a,b, 14–19) to predict their profile on the α1β2γ2-GABAAR subtype. Furthermore, to verify whether the information coming from this virtual model was valid and, at the same time, to complete the study on this series, we evaluated the effects of compounds (1–100 µM) on the modulation of GABAA receptor function through electrophysiological techniques on recombinant α1β2γ2L-GABAA receptors expressed in Xenopus laevis oocytes. The matching between the virtual prediction and the electrophysiological tests makes our model a useful tool for the study of GABAA receptor modulators.
Potential anxiolytic agents. 3. Novel A-ring modified pyrido[1,2-a]benzimidazoles
Bioorganic & Medicinal Chemistry Letters, 1999
A variety of pyrido[1,2-a]benzimidazoles (PBIs) modified on the A-ring were prepared and evaluated for affinity to the benzodiazepine binding site on the GABA-A receptor and in animal models predictive of anxiolytic activity in humans. A-ring benzo-fused derivative 7 exhibited potent activity, as did the 6-and 7-pyrido compounds 3 and 4.