N'-(arylsulfonyl)pyrazoline-1-carboxamidines as novel, neutral 5-hydroxytryptamine 6 receptor (5-HT6R) antagonists with unique structural features.

The 5-HT(6) receptor (5-HT(6)R) has been in the spotlight for several years regarding CNS-related diseases. We set out to discover novel, neutral 5-HT(6)R antagonists to improve off-target selectivity compared to basic amine-containing scaffolds dominating the field. High-throughput screening identified the N'-(sulfonyl)pyrazoline-1-carboxamidine scaffold as a promising neutral core for starting hit-to-lead. Medicinal chemistry, molecular modeling, small molecule NMR and X-ray crystallography were subsequently applied to optimize the leads into antagonists (compounds 1-49) displaying high 5-HT(6)R affinity with optimal off-target selectivity. Unique structural features include a pseudoaromatic system and an internal hydrogen bond freezing the bioactive conformation. While physicochemical properties and CNS availability were generally favorable, significant efforts had to be made to improve metabolic stability. The optimized structure 42 is an extremely selective, hERG-free, high-affinity 5-HT(6)R antagonist showing good human in vitro metabolic stability. Rat pharmacokinetic data were sufficiently good to enable further in vivo profiling.

Probing the cannabinoid CB1/CB2 receptor subtype selectivity limits of 1,2-diarylimidazole-4-carboxamides by fine-tuning their 5-substitution pattern.

The cannabinoid CB(1)/CB(2) receptor subtype selectivity in the 1,2-diarylimidazole-4-carboxamide series was boosted by fine-tuning its 5-substitution pattern. The presence of the 5-methylsulfonyl group in 11 led to a greater than approximately 840-fold CB(1)/CB(2) subtype selectivity. The compounds 10, 18 and 19 were found more active than rimonabant (1) in a CB(1)-mediated rodent hypotension model after oral administration. Our findings suggest a limited brain exposure of the P-glycoprotein substrates 11, 12 and 21.

Design, synthesis, biological properties, and molecular modeling investigations of novel tacrine derivatives with a combination of acetylcholinesterase inhibition and cannabinoid CB1 receptor antagonism.

Pyrazolines 7-10 were designed as novel CB(1) receptor antagonists, which exhibited improved turbidimetric aqueous solubilities. On the basis of their extended CB(1) antagonist pharmacophore, hybrid molecules exhibiting cannabinoid CB(1) receptor antagonistic as well as acetylcholinesterase (AChE) inhibiting activities were designed. The target compounds 12, 13, 20, and 21 are based on 1 (tacrine) as the AChE inhibitor (AChEI) pharmacophore and two different CB(1) antagonistic pharmacophores. The imidazole-based 20 showed high CB(1) receptor affinity (48 nM) in combination with high CB(1)/CB(2) receptor subtype selectivity (>20-fold) and elicited equipotent AChE inhibitory activity as 1. Molecular modeling studies revealed the presence of a binding pocket in the AChE enzyme which nicely accommodates the CB(1) pharmacophores of the target compounds 12, 13, 20, and 21.

Synthesis and SAR of novel imidazoles as potent and selective cannabinoid CB2 receptor antagonists with high binding efficiencies.

The synthesis and structure-activity relationship studies of imidazoles are described. The target compounds 6-20 represent a novel chemotype of potent and CB(2)/CB(1) selective cannabinoid CB(2) receptor antagonists/inverse agonists with very high binding efficiencies in combination with favourable logP and calculated polar surface area values. Compound 12 exhibited the highest CB(2) receptor affinity (K(i)=1.03 nM) in this series, as well as the highest CB(2)/CB(1) subtype selectivity (>9708-fold).

Bioisosteric replacements of the pyrazole moiety of rimonabant: synthesis, biological properties, and molecular modeling investigations of thiazoles, triazoles, and imidazoles as potent and selective CB1 cannabinoid receptor antagonists.

Series of thiazoles, triazoles, and imidazoles were designed as bioisosteres, based on the 1,5-diarylpyrazole motif that is present in the potent CB(1) receptor antagonist rimonabant (SR141716A, 1). A number of target compounds was synthesized and evaluated in cannabinoid (hCB(1) and hCB(2)) receptor assays. The thiazoles, triazoles, and imidazoles elicited in vitro( )()CB(1) antagonistic activities and in general exhibited considerable CB(1) vs CB(2) receptor subtype selectivities, thereby demonstrating to be cannabinoid bioisosteres of the original diarylpyrazole class. Some key representatives in the imidazole series showed potent pharmacological in vivo activities after oral administration in both a CB agonist-induced hypotension model and a CB agonist-induced hypothermia model. Molecular modeling studies showed a close three-dimensional structural overlap between the key compound 62 and rimonabant. A structure-activity relationship (SAR) study revealed a close correlation between the biological results in the imidazole and pyrazole series.