Identification of sulfonamide compounds active on the insect nervous system: Molecular modeling, synthesis and biological evaluation.

Insect nicotinic acetylcholine receptors (nAChRs) are a recognized target for insecticide design. In this work, we have identified, from a structure-based approach using molecular modeling tools, ligands with potential selective activity for pests versus pollinators. A high-throughput virtual screening with the Openeye software was performed using a library from the ZINC database, thiacloprid being used as the target structure. The top sixteen molecules were then docked in α6 cockroach and honeybee homomeric nAChRs to check from a theoretical point of view relevant descriptors in favor of pest selectivity. Among the selected molecules, one original sulfonamide compound has afterward been synthesized, together with various analogs. Two compounds of this family have been shown to behave as activators of the cockroach cholinergic synaptic transmission.

Binding of Sulfoxaflor to Aplysia californica-AChBP: Computational Insights from Multiscale Approaches.

Structural features and binding properties of sulfoxaflor (SFX) with Ac-AChBP, the surrogate of the insect nAChR ligand binding domain (LBD), are reported herein using various complementary molecular modeling approaches (QM, molecular docking, molecular dynamics, and QM/QM'). The different SFX stereoisomers show distinct behaviors in terms of binding and interactions with Ac-AChBP. Molecular docking and Molecular Dynamics (MD) simulations highlight the specific intermolecular contacts involved in the binding of the different SFX isomers and the relative contribution of the SFX functional groups. QM/QM' calculations provide further insights and a significant refinement of the geometric and energetic contributions of the various residues leading to a preference for the SS and RR stereoisomers. Notable differences in terms of binding interactions are pointed out for the four stereoisomers. The results point out the induced fit of the Ac-AChBP binding site according to the SFX stereoisomer. In this process, the water molecules-mediated contacts play a key role, their energetic contribution being among the most important for the various stereoisomers. In all cases, the interaction with Trp147 is the major binding component, through CH···π and π···π interactions. This study provides a rationale for the binding of SFX to insect nAChR, in particular with respect to the new class of sulfoximine-based insect nAChR competitive modulators, and points out the requirements of various levels of theory for an accurate description of ligand-receptor interactions.

Enantioseparation and thermodynamic study of naphthalene derivatives, new melatoninergic agonists, on coated amylose [tris(S)-1-phenylethylcarbamate] stationary phase. Transposition to preparative scale.

This work reports a high-performance liquid chromatography normal-phase methodology to elucidate enantiomers of naphthalene derivatives, evaluated as melatoninergic agonists. For this purpose four different polysaccharide based chiral stationary phases were evaluated, namely Chiralcel OD-H (cellulose tris-3,5-dimethylphenylcarbamate), Chiralcel OJ (cellulose tris-methylbenzoate), Chiralpak AD (amylose tris-3,5-dimethylphenylcarbamate) and Chiralpak AS (amylose tris-(S)-1-phenylethylcarbamate) with different alcoholic modifiers on different amounts in n-heptane. A temperature study was carried out, between 20 and 40 °C and the apparent thermodynamic parameters were calculated thanks to the Van't Hoff linearization. For all compounds (except 3), ΔΔH° and ΔΔS° exhibited positive values ranging from 791.2 to 9999.3 J/mol and from 3.9 to 37.8 J/K/mol respectively, indicating entropically driven separations. Optimized conditions led to goof resolution of 2.37 for compound 1 on Chiralpak AS, with heptane-2-propanol 90:10 (v/v), at a temperature of 30 °C. Then they were transposed to the preparative scale for compound 1, generating 22 mg of each enantiomer with an 80% yield. The limits of detection and of quantification were determined to allow the calculation of the enantiomeric excess. They were found with very low values, equal to 0.32 and 1.05 µ m and 0.33 and 1.11 µ m, respectively, for peaks 1 and 2 of compound 1.

Enhanced detection for determination of enantiomeric purity of novel agomelatine analogs by EKC using single and dual cyclodextrin systems.

Performing CD-EKC, baseline separation of five agomelatine analogs, potential antidepressant compounds, was achieved. A method for the enantioresolution and determination of enantiomeric purity of these naphthalene derivatives was developed using capillaries dynamically coated with polyethylene oxide and anionic cyclodextrins (highly sulfated CD) as chiral selectors. Operational parameters such as the nature and concentration of the cyclodextrins were investigated. In a second step the implementation of a dual cyclodextrin system was found to strongly enhance the LOD of the analytes. After optimization, best conditions were a 25 mM phosphate buffer at pH 2.5 containing 5% w/v (i.e. 19.7 mM) of highly sulfated-γ-CD and 10 mM of 6-monodeoxy-6-monoamino-ß-CD dual system, leading to resolution of, at least, 3.6 in 35 min. A preliminary validation of the developed method was undertaken: linearity, precision, and LOD and LOQ were evaluated. The latest ones were found equal to 0.25 and 0.82 µM and to 0.31 and 0.96 µM respectively for the first and the second enantiomer of compound 1.

New melatonin (MT1/MT2) ligands: design and synthesis of (8,9-dihydro-7H-furo[3,2-f]chromen-1-yl) derivatives.

Herein we describe the synthesis of novel tricyclic analogues issued from the rigidification of the methoxy group of the benzofuranic analogue of melatonin as MT1 and MT2 ligands. Most of the synthesized compounds displayed high binding affinities at MT1 and MT2 receptors subtypes. Compound 6b (MT1, Ki=0.07nM; MT2, Ki=0.08nM) exhibited with the vinyl 6c and allyl 6d the most interesting derivatives of this series. Functional activity of these compounds showed full agonist activity with EC50 in the nanomolar range. Compounds 6a (EC50=0.8nM and Emax=98%) and 6b (EC50=0.2nM and Emax=121%) exhibited good pharmacological profiles.

Mannose-coupled AAV2: A second-generation AAV vector for increased retinal gene therapy efficiency.

Inherited retinal diseases are a leading and untreatable cause of blindness and are therefore candidate diseases for gene therapy. Recombinant vectors derived from adeno-associated virus (rAAV) are currently the most promising vehicles for in vivo therapeutic gene delivery to the retina. However, there is a need for novel AAV-based vectors with greater efficacy for ophthalmic applications, as underscored by recent reports of dose-related inflammatory responses in clinical trials of rAAV-based ocular gene therapies. Improved therapeutic efficacy of vectors would allow for decreases in the dose delivered, with consequent reductions in inflammatory reactions. Here, we describe the development of new rAAV vectors using bioconjugation chemistry to modify the rAAV capsid, thereby improving the therapeutic index. Covalent coupling of a mannose ligand, via the formation of a thiourea bond, to the amino groups of the rAAV capsid significantly increases vector transduction efficiency of both rat and nonhuman primate retinas. These optimized rAAV vectors have important implications for the treatment of a wide range of retinal diseases.

Novel conformationally constrained analogues of agomelatine as new melatoninergic ligands.

Novel conformationally restricted analogues of agomelatine were synthesized and pharmacologically evaluated at MT1 and MT2 melatoninergic receptors. Replacement of the N-acetyl side chain of agomelatine by oxathiadiazole-2-oxide (compound 3), oxadiazole-5(4H)-one (compound 4), tetrazole (compound 5), oxazolidinone (compound 7a), pyrrolidinone (compound 7b), imidazolidinedione (compound 12), thiazole (compounds 13 and 14) and isoxazole moieties (compound 15) led to a decrease of the melatoninergic binding affinities, particularly at MT1. Compounds 7a and 7b exhibiting nanomolar affinity towards the MT2 receptors subtypes have shown the most interesting pharmacological results of this series with the appearance of a weak MT2-selectivity.

Mode of action of sulfoxaflor on α-bungarotoxin-insensitive nAChR1 and nAChR2 subtypes: Inhibitory effect of imidacloprid.

Cockroach neurosecretory cells, dorsal unpaired median (DUM) neurons, express two distinct α-bungarotoxin-insensitive nicotinic acetylcholine receptor subtypes, nAChR1 and nAChR2 which are differently sensitive to the neonicotinoid insecticides and intracellular calcium pathways. The aim of this study is to determine whether sulfoxaflor acts as an agonist of nAChR1 and nAChR2 subtypes. We demonstrated that 1 mM sulfoxaflor induced high current amplitudes, compared to acetylcholine, suggesting that it was a full agonist of DUM neuron nAChR subtypes. Sulfoxaflor evoked currents were not inhibited by the nicotinic acetylcholine receptor antagonist d-tubocurarine (dTC) which reduced nAChR1. But, sulfoxaflor evoked currents were reduced in the presence of 5 µM mecamylamine which is known to reduce nAChR2 subtype. Interestingly, when 1 µM imidacloprid was added in the extracellular solution, sulfoxaflor-induced currents were significantly suppressed. Moreover, when extracellular calcium concentration was increased, bath application of 1 µM imidacloprid partially reduced sulfoxaflor activated currents when nAChR1 was inhibited with 20 µM dTC and completely suppressed sulfoxaflor currents when nAChR2 was inhibited with 5 µM mecamylamine. Our data demonstrated therefore that sulfoxaflor activates both nAChR1 and nAChR2 subtypes.

Synthesis and biological evaluation of new naphtho- and quinolinocyclopentane derivatives as potent melatoninergic (MT1/MT2) and serotoninergic (5-HT2C) dual ligands.

We recently reported a series of naphthofuranic compounds as constrained agomelatine analogues. Herein, in order to explore alternative ethyl amide side chain rigidification, naphthocyclopentane and quinolinocyclopentane derivatives with various acetamide modulations were synthesized and evaluated at both melatonin (MT1, MT2) and serotonin (5-HT2C) receptors. These modifications has led to compounds with promising dual affinity and high MTs receptors agonist activity. Enantiomeric separation was then performed on selected compounds allowing us to identify levogyre enantiomers (-)-17g and (-)-17k as the highest (MT1, MT2)/5-HT2C dual ligands described nowadays.

New quinolinic derivatives as melatonergic ligands: Synthesis and pharmacological evaluation.

New series of melatonergic ligands issued from two methoxy-quinolinic scaffolds (2-MQ and 3-MQ), were designed and synthesized. Herein we report the synthetic scheme and pharmacological results of the new prepared compounds. Investigation of compound 11a, the strict 2-MQ analogue, revealed the promising potential of this series. Therefore, pharmacomodulation of the acetamide function of 11a has led to compounds with different pharmacological profiles and the emergence of an MT2 selectivity. Besides, sulphonamide 11b showed the most important MT2 selectivity of this series (167 folds) while methyl and ethyl-ureas 11f and 11g represented the most potent melatonergic ligands of this study.

Design of experiments for enantiomeric separation in supercritical fluid chromatography.

A new chiral melatoninergic ligand, potentially successor of Valdoxan(®), presenting an improved pharmacological profile with regard to agomelatine, was chosen as a probe for a supercritical fluid chromatographic separation carried-out on an amylose tris[(S)-1-α-methylbenzylcarbamate] based stationary phase. The goal of this work was to optimize simultaneously three factors identified to have a significant influence to obtain the best resolution in the shortest analysis time (i.e., retention time of the second eluting enantiomer) for this chiral compound. For this purpose a central circumscribed composite (CCC) design was developed with three factors: the flow-rate, the pressure outlet and the percentage of ethanol to optimize of two responses: shortest analysis time and best resolution. The optimal conditions obtained via the optimizer mode of the software (using the Nelder-Mead method) i.e., CO2/EtOH 86:14 (v:v), 104bar, 3.2mLmin(-1) at 35°C lead to a resolution of 3.27 in less than 6min. These conditions were transposed to a preparative scale where a concentrated methanolic solution of 40mM was injected with a sample loop of 100µL. This step allowed to separate an amount of around 65mg of racemic melatonin ligand in only 3h with impressive yields (97%) and enantiomeric excess (99.5%).

Melatonergic ligands: Design, synthesis and pharmacological evaluation of novel series of naphthofuranic derivatives.

Following our research for new melatonergic ligands, herein we report the design, synthesis and biological evaluation of new series of naphthofuranic derivatives as MT1 and MT2 ligands. Binding affinity results of the prepared compounds revealed good binding affinities at both melatonin receptor subtypes. Particularly, compound 6a behaved as an MT1 partial agonist and MT2 full agonist and exhibited an excellent binding affinity at MT2 (Ki = 0.09 nM). In addition, lateral chain displacement from position 1 to 2 of the furan core had no effect on the binding affinity at both MT1 and MT2, while elongation of this side chain, led to decreased melatonergic binding affinities.

Synthesis and pharmacological evaluation of a series of the agomelatine analogues as melatonin MT1 /MT2 agonist and 5-HT2C antagonist.

Agomelatine is a naphthalenic analogue of melatonin that is in clinical use for the treatment of major depressive disorders. Interestingly, while agomelatine exhibits potent affinity for melatonin receptors, it binds with only moderate affinity to the serotonin 5-HT2C receptor. Optimization of agomelatine toward this target could further potentiate its clinical efficacy. To explore this hypothesis and to access derivatives in which a key point of agomelatine metabolism is blocked, a series of naphthalenic derivatives was designed and synthesized as novel analogues of agomelatine. Most of the prepared compounds exhibited good binding affinity at the melatonin MT1 and MT2 receptor subtypes. Two compounds, an acetamide and an acrylamide derivative, exhibited good binding affinities at both the human melatonin (MT) receptors and the serotonin 5-HT2C receptor subtype, with pKi values of 7.96 and 7.95 against MT1, 7.86 and 8.68 against MT2, and 6.64 and 6.44 against 5-HT2C, respectively.