Evaluation of Amides, Carbamates, Sulfonamides, and Ureas of 4-Prop-2-ynylidenecycloalkylamine as Potent, Selective, and Bioavailable Negative Allosteric Modulators of Metabotropic Glutamate Receptor 5.

Negative allosteric modulators (NAMs) of the metabotropic glutamate receptor 5 (mGlu5) hold great promise for the treatment of a variety of central nervous system disorders. We have recently reported that prop-2-ynylidenecycloalkylamine derivatives are potent and selective NAMs of the mGlu5 receptor. In this work, we explored the amide, carbamate, sulfonamide, and urea derivatives of prop-2-ynylidenecycloalkylamine compounds with the aim of improving solubility and metabolic stability. In silico and experimental analyses were performed on the synthesized series of compounds to investigate structure-activity relationships. Compounds 12, 32, and 49 of the carbamate, urea, and amide classes, respectively, showed the most suitable cytochrome inhibition and metabolic stability profiles. Among them, compound 12 showed excellent selectivity, solubility, and stability profiles as well as suitable in vitro and in vivo pharmacokinetic properties. It was highly absorbed in rats and dogs and was active in anxiety, neuropathic pain, and lower urinary tract models.

New spirocyclic Δ²-isoxazoline derivatives related to selective agonists of α7 neuronal nicotinic acetylcholine receptors.

A set of structural analogues of spirocyclic quinuclidinyl-Δ(2)-isoxazolines, characterized as potent and selective α7 nicotinic agonists, was prepared and assayed for binding affinity at α7 and α4ß2 neuronal nicotinic acetylcholine receptors (nAChRs). The investigated derivatives (3a-3c, 4a-4c, 5a-5c, 6a-6c, and 7a-7c), synthesized via the 1,3-dipolar cycloaddition of nitrile oxides to suitable dipolarophiles, showed an overall reduced affinity at the α7 subtype when compared with their model compounds. Solely Δ(2)-isoxazolines 3a, 3b, and 6c maintained a binding affinity in the nanomolar range at the α7 nAChRs (K(i) = 230, 420 and 700 nM, respectively). The quaternary ammonium salt 6c retained also a noteworthy α7 vs. α4ß2 subtype selectivity, whereas 3a and 3b showed a sharp reduction in selectivity compared with 1a and 1b, their quinuclidinyl higher homologues.

Design, synthesis, and pharmacological characterization of novel spirocyclic quinuclidinyl-Δ2-isoxazoline derivatives as potent and selective agonists of α7 nicotinic acetylcholine receptors.

A set of racemic spirocyclic quinuclidinyl-Δ(2)-isoxazoline derivatives was synthesized using a 1,3-dipolar cycloaddition-based approach. Target compounds were assayed for binding affinity toward rat neuronal homomeric (α7) and heteromeric (α4ß2) nicotinic acetylcholine receptors. Δ(2) -Isoxazolines 3 a (3-Br), 6 a (3-OMe), 5 a (3-Ph), 8 a (3-OnPr), and 4 a (3-Me) were the ligands with the highest affinity for the α7 subtype (K(i) values equal to 13.5, 14.2, 25.0, 71.6, and 96.2 nM, respectively), and showed excellent α7 versus α4ß2 subtype selectivity. These compounds, tested in electrophysiological experiments against human α7 and α4ß2 receptors stably expressed in cell lines, behaved as partial α7 agonists with varying levels of potency. The two enantiomers of (±)-3-methoxy-1-oxa-2,7-diaza-7,10-ethanospiro[4.5]dec-2-ene sesquifumarate 6 a were prepared using (+)-dibenzoyl-L- or (-)-dibenzoyl-D-tartaric acid as resolving agents. Enantiomer (R)-(-)-6 a was found to be the eutomer, with K(i) values of 4.6 and 48.7 nM against rat and human α7 receptors, respectively.

Novel tricyclic Delta(2)-isoxazoline and 3-oxo-2-methyl-isoxazolidine derivatives: synthesis and binding affinity at neuronal nicotinic acetylcholine receptor subtypes.

A group of novel tricyclic Delta(2)-isoxazolines (4b, 5b, 7a-b, and 8a-b) and 3-oxo-isoxazolidines (6a-b and 9a-b), structurally related to cytisine or norferruginine, was prepared through 1,3-dipolar cycloadditions involving suitable olefins and bromonitrile oxide. The target compounds were assayed at alpha4beta2 and alpha7 neuronal acetylcholine receptors (nAChRs). The results of competition binding experiments indicated for the new derivatives a reduction of the affinity at the alpha4beta2 subtype in comparison with the reference molecules, coupled with an overall negligible affinity at the alpha7 subtype. The binding mode of the bromo-Delta(2)-isoxazolines 4b and 7b, which were the highest affinity ligands in the series (K(i)=0.92 and 0.75 microM, respectively), was analyzed by applying a recently developed model of the alpha4beta2 nAChRs.

Design of novel alpha7-subtype-preferring nicotinic acetylcholine receptor agonists: application of docking and MM-PBSA computational approaches, synthetic and pharmacological studies.

In the search for nicotinic acetylcholine receptor (nAChRs) agonists with a selective affinity for the homomeric alpha7 channels, we carried out the virtual screening of a test set of potential nicotinic ligands, and adopted a simplified MM-PBSA approach to estimate their relative binding free energy values. By means of this procedure, previously validated by a training set of compounds, we reached a realistic compromise between computational accuracy and calculation rate, and singled out a small group of novel structurally related derivatives characterized by a promising theoretical affinity for the alpha7 subtype. Among them, five new compounds were synthesized and assayed in binding experiments at neuronal alpha7 as well as alpha4beta2 nAChRs.

Novel chiral isoxazole derivatives: synthesis and pharmacological characterization at human beta-adrenergic receptor subtypes.

Isoxazole derivative (+/-)-4 and the three pairs of stereoisomeric 3-bromo-isoxazolyl amino alcohols (S,R)-(-)-7a/(R,R)-(+)-7b, (S,R)-(-)-8a/(R,R)-(+)-8b, and (S,R)-(-)-9a/(R,R)-(+)-9b were synthesized and assayed for their affinity and efficacy at human beta(1)-, beta(2)-, and beta(3)-adrenergic receptors (beta-ARs) in membranes from Chinese hamster ovary (CHO) cells stably transfected with the respective receptor subtype. Whereas derivative (+/-)-4 did not bind at all three beta-ARs, stereoisomers (S,R)-7a-(S,R)-9a behaved as high-affinity ligands at beta(1)- and, particularly, at beta(2)-ARs (K(i) 2.82-66.7 nM). The K(i) values of isomers (R,R)-7b-(R,R)-9b at beta(1)- and beta(2)-subtypes were about 30-100 times higher than those of their (S,R)-7a-9a counterparts, indicating a sizable stereochemical effect. The affinity at beta(3)-ARs was negligible for all the investigated compounds. When submitted to a functional assay, the three stereoisomeric pairs showed a comparable pattern of efficacy at all three beta-AR subtypes. The highest value of efficacy (75-90%) was observed at beta(2)-ARs, whereas all compounds behaved as partial agonists (30-60%) at the beta(3)-subtype. The lowest degree of efficacy (15-35%) was found at beta(1)-ARs. The affinity/efficacy profile of the derivatives under study has been compared with that of the two model compounds, Broxaterol [(+/-)-1] and BRL 37344 [(+/-)-6].