Potent imidazole and triazole CB 1 receptor antagonists related to SR141716

Synthesis, physicochemical characterization, and investigation of anti-inflammatory activity of water-soluble PEGylated 1,2,4-Triazoles

A series of water-soluble PEGylated 1,2,4-triazoles 5-8 were successfully synthesized from methyl 5-(chloromethyl)-1-aryl-1H-1,2,4-triazole-3-carboxylates 1. All of the water-soluble PEGylated 1,2,4-triazoles were characterized by FT-IR and 1H NMR spectroscopy. The solubility, in vitro plasma stability, and anti-inflammatory activity were also determined and compared to original methyl 5-(halomethyl)-1-aryl-1H-1,2,4-triazole-3-carboxylates. For SAR study, all PEGylated 1,2,4-triazoles 5-8 performed potential anti-inflammatory activity on LPS-induced RAW 264.7 cells (IC50 = 3.42-7.81 μM). Moreover, the western blot result showed PEGylated 1,2,4-triazole 7d performed 5.43 and 2.37 folds inhibitory activity over iNOS and COX-2 expressions. On the other hand, the cell viability study revealed PEGylated 1,2,4-triazoles 7 and 8 with PEG molecular weight more than 600 presented better cell safety (cell viability > 95 %). Through the solubility and in vitro plasma stability studies, PEGylated 1,2,4-triazoles 7a-d exhibited higher hydrophilicity and prolonged 2.01 folds of half-life in compound 7d. Furthermore, the in vivo anti-inflammatory and gastric safety results indicated PEGylated 1,2,4-triazole 7d more effectively decreased the inflammatory response in edema and COX-2 expression and exhibited higher gastric safety than Indomethacin. Following the in vitro and in vivo study results, PEGylated 1,2,4-triazole 7d possessed favorable solubility, plasma stability features, safety, and significant anti-inflammatory activity to become the potential water-soluble anti-inflammatory candidate.

Synthesis and anti-inflammatory activity evaluation of NO-releasing furoxan/1,2,4-triazole hybrid derivatives

An efficient synthesis method was developed for furoxan/1,2,4-triazole hybrids 5a-k from methyl 5-(halomethyl)-1-aryl-1H-1,2,4-triazole-3-carboxylates 1 through two-steps reaction including hydrolyzation and esterification. All of the furoxan/1,2,4-triazole hybrid derivatives were characterized by spectroscopy. On the other hand, the influence of newly synthesized multi-substituted 1,2,4-triazoles on the exogenous NO release ability, in vitro and in vivo anti-inflammatory activity, and in silico predictions were experimentally evaluated. Based on the exogenous NO release ability study and SAR studies of in vitro anti-inflammatory activity, all of compounds 5a-k exhibited slightly NO release ability and potential anti-inflammatory activity on LPS-induced RAW264.7 cells (IC₅₀ = 5.74-15.3 μM) compared to Celecoxib (IC₅₀ = 16.5 μM) and Indomethacin (IC₅₀ = 56.8 μM). Furthermore, compounds 5a-k were also subjected to in vitro COX-1/COX-2 inhibition assays. Particularly, compound 5f exhibited extraordinary COX-2 inhibition (IC₅₀ = 0.0455 μM) and selectivity (SI = 209). In addition, compound 5f was also examined in vivo pro-inflammatory cytokine productions and gastric safety and possessed the better inhibition of cytokine and safety compared with Indomethacin at the same concentration. Through the molecular modeling and in silico physicochemical and pharmacokinetic properties prediction, compound 5f was stabilized in COX-2 active binding site and possessed the fundamental strong H-bond interaction with Arg499 to form the significant physicochemical and pharmacological properties as a candidate drug. Following the in vitro, in vivo, and in silico study results, compound 5f demonstrated to be a potential anti-inflammatory agent and had comparable effects with Celecoxib.

Isocyanide-Based Multicomponent Reactions in Water: Advanced Green Tools for the Synthesis of Heterocyclic Compounds

Reaction rate acceleration using green methods is an intriguing area of research for chemists. In this regard, water as a "green solvent" plays a crucial role in the acceleration of some organic transformations and reveals exclusive selectivity and reactivity in comparison with conventional organic solvents. In particular, multicomponent reactions (MCRs) as sustainable tools lead to the rapid generation of small-molecule libraries in water and aqueous media due to the prominent role of the hydrophobic effect. MCRs, as diversity-oriented synthesis (DOS) methods, have great efficiency with simple operations, atom, pot, and step economy synthesis, and mechanistic beauty. Among diverse classes of MCRs, isocyanide-based multicomponent reactions (I-MCRs), as sustainable and versatile reactions, have gained considerable attention in the synthesis of diverse heterocycle rings, especially in drug design because of the peculiar nature of isocyanide as a particular active reactant. I-MCRs that are performed in water are mild, environmentally friendly, and easily controlled, and have a reduced number of workup, purification, and extraction steps, which fit well with the advantages of "green" chemistry. Performing these powerful organic transformations in water and aqueous media is accompanied by acceleration owing to negative activation volumes, which originate from connecting several reactants together to generate a single product. It should be noted that the combination of MCR strategy and aqueous phase reaction is of growing interest for the development of sustainable synthetic techniques in organic conversions. However, an exclusive account focusing on the recent progress in eco-friendly I-MCRs for the construction of heterocycles in water and aqueous media is particularly lacking. This review highlights the progress of various kinds of I-MCRs in water and aqueous media as benign methods for the efficient construction of vital heterocyclic scaffolds, with a critical discussion of the subject in the period 2000-2021. We hope that this themed collection will be of interest and beneficial for organic and pharmaceutical chemists and will inspire more reaction development in this fascinating field.

Design, synthesis and biological evaluation of glycolamide, glycinamide, and β-amino carbonyl 1,2,4-triazole derivatives as DPP-4 inhibitors

Through modification of the skeleton of Sitagliptin and Vildagliptin, we successfully synthesized and built-up four series of 1,2,4-triazole derivatives, containing N,O-disubstituted glycolamide, N,N'-disubstituted glycinamide, β-amino ester, and β-amino amide as linkers, for the development of new dipeptidyl peptidase 4 (DPP-4) inhibitors. The synthetic strategy for glycolamides or glycinamides involved convenient two-steps reaction: functionalized transformation of 2-chloro-N-(2,4,5-triflurophenyl)acetamide 9 (hydroxylation or amination) and esterification or amidation of 1,2,4-triazole-3-carboxylic acid. On the other hand, the one-pot synthesis procedure, including substitution and deprotection, was developed for the preparation of β-amino carbonyl 1,2,4-triazoles from (1H-1,2,4-triazol-3-yl)methanol 12 or (1H-1,2,4-triazol-3-yl)methanamine 13 and Boc-(R)-3-amino-4-(2,4,5-trifluoro-phenyl)-butyric acid 14. All of glycolamides, glycinamides, and β-amino carbonyl 1,2,4-triazoles were also evaluated against DPP-4 inhibitory activity. Based on the SAR study of DPP-4 inhibitory capacity, β-amino ester 5n and β-amino amide 1,2,4-triazoles 6d and 6p possessed the significant inhibition of DPP-4 (IC₅₀ < 51.0 nM), particularly for compound 6d (IC₅₀ = 34.4 nM). The selectivity evaluation indicated compound 5n and 6p had excellent selectivity over QPP, DPP-8, and DPP-9. In addition, the docking results revealed compounds 5n and 6p provided stronger π-π stacking interaction with residue Phe357 than 1,5-disubstituted 1,2,4-triazole 6d and Sitagliptin 1. In summary, compounds 5n and 6p could be promising lead compounds for further development of DPP-4 inhibitor.

Chlorotrimethylsilane promoted one-flask heterocyclic synthesis of 1,2,4-triazoles from nitrilimines: Modeling studies and bioactivity evaluation of LH-21 and Rimonabant analogues

An efficient one-flask cascade method for synthesis of the multi-substituted 1,2,4-triazoles via chlorotrimethylsilane as a promoter was developed. Firstly, nitrilimines were transformed to hydrazonamides as intermediate in high yield by treatment with commercially available hexamethyldisilazane. Subsequently, the mixture was added with corresponding acyl chloride and heated in the presence of pyridine to give the corresponding multi-substituted 1,2,4-triazoles via chlorotrimethylsilane promoted heterocyclization reaction. The utility of method was demonstrated to synthesize CB₁ ligands including Rimonabant analogue 4c and LH-21 3 for modeling study. All synthesized compounds were subjected to the cAMP functional assay of CB₁/CB₂ receptor. Especially, compound 4g enhanced the reversal of cAMP reduction by CP59440 than LH-21 and Rimonabant analogue in CHO-hCB₁ cells. In addition, the docking results showed compound 4g fits the best position with CB₁ receptor. However, the ability to penetrate brain-blood barrier of compound 4g is similar with Rimonabant in MDCK-mdr1 permeability assay, which might cause CNS side effect. This study still provides the basis for further development of a potent and specific CB₁ antagonist.

Design, Synthesis, Antimicrobial Evaluation and Molecular Modeling Study of New 2-mercaptoimidazoles (Series-III)

Background:

A series of novel substituted 2-mercaptoimidazoles was synthesised efficiently and in high yields using one-pot synthesis from m-hydroxyacetophenones.

Methods:

The structures of the newly synthesized compounds were established, their molecular activity was investigated against some bacteria and fungi were further validated using molecular docking study.

Results:

Reaction of o-hydroxyphenacylbromide (2) with substituted aniline and KSCN, in the presence of catalyst p-toluene sulfonic acid afforded 4(a-r) in good yield. The structure of compounds (4a-r) was confirmed by IR, NMR and MS.

Conclusion:

The compounds exhibited excellent antimicrobial potency against the tested microorganism.

One for the Price of Two…Are Bivalent Ligands Targeting Cannabinoid Receptor Dimers Capable of Simultaneously Binding to both Receptors?

Bivalent ligands bridging two G-protein-coupled receptors (GPCRs) provide valuable pharmacological tools to target oligomers. The success of therapeutically targeting the cannabinoid CB1 receptor has been limited, in part due to its widespread neuronal distribution. Therefore, CB1 ligands targeting oligomers that exhibit restricted distribution or altered pharmacology are highly desirable, and several bivalent ligands containing a CB1 pharmacophore have been reported. Bivalent ligand action presumes that the ligand simultaneously binds to both receptors within the dimeric complex. However, based on the current understanding of CB1 ligand binding, existing bivalent ligands are too short to bind both receptors simultaneously. However, ligands with longer linkers may not be the solution, because evidence suggests that ligands enter CB1 through the lipid bilayer and, thus, linkers are unlikely to exit the receptor through its external face. Thus, the entire premise of designing bivalent ligands targeting CB1 must be revisited.

Synthesis and biological evaluation of bivalent ligands for the cannabinoid 1 receptor

Dimerization or oligomerization of many G-protein-coupled receptors (GPCRs), including the cannabinoid 1 (CB1) receptor, is now widely accepted and may have significant implications for medications development targeting these receptor complexes. A library of bivalent ligands composed of two identical CB1 antagonist pharmacophores derived from SR141716 linked by spacers of various lengths were developed. The affinities of these bivalent ligands at CB1 and CB2 receptors were determined using radiolabeled binding assays. Their functional activities were measured using GTP-γ-S accumulation and intracellular calcium mobilization assays. The results suggest that the nature of the linker and its length are crucial factors for optimum interactions of these ligands at CB1 receptor binding sites. Finally, selected bivalent ligands (5d and 7b) were able to attenuate the antinociceptive effects of the cannabinoid agonist CP55,940 (21) in a rodent tail-flick assay. These novel compounds may serve as probes that will enable further characterization of CB1 receptor dimerization and oligomerization and its functional significance and may prove useful in the development of new therapeutic approaches to G-protein-coupled receptor mediated disorders.

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.

DFT study on the mechanisms of stereoselective C2-vinylation of 1-substituted imidazoles with 3-phenyl-2-propynenitrile

Recently, the first examples of direct vinylation of 1-substituted imidazoles at the 2-position of the imidazole nucleus have been described (J. Org. Chem. 2008, 73, 9155-9157). 1-Substituted imidazoles are C(2)-vinylated with 3-phenyl-2-propynenitrile at room temperature without catalyst and solvent to afford 3-(1-organyl-1H-imidazol-2-yl)-3-phenyl-2-propenenitriles, mainly (ca. 95%) as (Z)-isomers, in 56-88% yield. Nevertheless, the stereoselectivity of vinylation, which has been elusive over the past decades, is still a big problem to explain. In this paper, the reaction mechanisms of stereoselective C(2)-vinylation of 1-methylimidazole with 3-phenyl-2-propynenitrile have been investigated using density functional theory (DFT). The geometries of the reactants, transition states, intermediates, and products were optimized at the B3LYP/6-31G(d,p) level. The calculated results reveal that the reaction contains three processes: formation of zwitterion, proton transfer, and ring rearrangement. Four possible reaction channels are shown, including two (E)-isomer channels and two (Z)-isomer channels. One of the (Z)-isomer channels has the lowest energy barrier among all the four channels, with the highest energy barrier for 83.62 kJ/mol, so it occurs more often than the others at room temperature, which is in good agreement with experiment. Further calculations of solvation effects show that the title reaction can be carried out more smoothly in the gas phase.

Cannabinoid CB1 receptor antagonists in therapeutic and structural perspectives

The observed antiobesity effect of rimonabant (1) in a pharmacological rodent model 10 years ago has led to a surge in the search for novel cannabinoid CB1 antagonists as a new therapeutic target for the treatment of obesity. Rimonabant showed clinical efficacy in the treatment of obesity and also improved cardiovascular and metabolic risk factors. Cannabinoid CB1 receptor antagonists have also good prospects in other therapeutic areas, including smoking and alcohol addiction as well as cognitive impairment. Solvay's research achievements in this fast-moving field are reported in relation with the current state of the art. Several medicinal chemistry strategies have been pursued. The application of the concept of conformational constraint led to the discovery of more rigid analogs of the prototypic CB1 receptor antagonist rimonabant. Replacement of the central heterocyclic pyrazole ring in rimonabant yielded imidazoles, triazoles, and thiazoles as selective CB1 receptor antagonists. Dedicated medium-throughput screening efforts delivered one 3,4-diarylpyrazoline hit. Its poor pharmacokinetic properties were successfully optimized which led to the discovery of orally active and highly CB1/CB2 receptor selective analogs in this series. Regioisomeric 1,5-diarylpyrazolines, 1,2-diarylimidazolines, and water-soluble imidazoles have been designed as novel CB1 receptor antagonist structure classes.

Synthesis of 2,4,5-trisubstituted imidazoles catalyzed by [Hmim]HSO4 as a powerful Brönsted acidic ionic liquid

An efficient and green procedure for the synthesis of 2,4,5-trisubstituted imidazoles with various aldehydes using a catalytic amount of 1-methylimidazolium hydrogenesulfate as an active and low cost Brönsted acidic room temperature ionic liquid has been developed. The ionic liquid was easily separated from the reaction mixture and was recycled five times without any loss in activity.Key words: ionic liquid, 2,4,5-trisubstituted imidazoles, [Hmim]HSO4, aldehyde, benzil.

Blocking the Cannabinoid Receptors: Drug Candidates and Therapeutic Promises

The CB1 and CB2 cannabinoid receptors have been described as two prime sites of action for endocannabinoids. Both the localization and pharmacology of these two G-protein-coupled receptors are well-described, and numerous selective ligands have been characterized. The physiological effects of Cannabis sativa (cannabis) and a throughout study of the endocannabinoid system allowed for the identification of several pathophysiological conditions--including obesity, dyslipidemia, addictions, inflammation, and allergies--in which blocking the cannabinoid receptors might be beneficial. Many CB1 receptor antagonists are now in clinical trials, and the results of several studies involving the CB1 antagonist lead compound rimonabant (SR141716A) are now available. This review describes the pharmacological tools that are currently available and the animal studies supporting the therapeutic use of cannabinoid receptor antagonists and inverse agonists. The data available from the clinical trials are also discussed.

Copper-catalyzed N-arylation of imidazoles and benzimidazoles

4,7-Dimethoxy-1,10-phenanthroline (L1c) was found to be an efficient ligand for the copper-catalyzed N-arylation of imidazoles and benzimidazoles with both aryl iodides and bromides under mild conditions. Further optimization of the system has revealed that the addition of poly(ethylene glycol) accelerates this reaction. A variety of hindered and functionalized imidazoles, benzimidazoles, and aryl halides were transformed in good to excellent yields. Heteroaryl halides were also coupled in moderate to good yields. We also present the results obtained from a series of coupling reactions, which directly compare the use of L1c with other recently reported ligands.

Optimization of imidazole amide derivatives as cannabinoid-1 receptor antagonists for the treatment of obesity

Several imidazole-based cyclohexyl amides were identified as potent CB-1 antagonists, but they exhibited poor oral exposure in rodents. Incorporation of a hydroxyl moiety on the cyclohexyl ring provided a dramatic improvement in oral exposure, together with a ca. 10-fold decrease in potency. Further optimization provided the imidazole 2-hydroxy-cyclohexyl amide 45, which exhibited hCB-1 K(i)=3.7nM, and caused significant appetite suppression and robust, dose-dependent reduction of body weight gain in industry-standard rat models.

4,7-Dimethoxy-1,10-phenanthroline: an excellent ligand for the Cu-catalyzed N-arylation of imidazoles

[reaction: see text] 4,7-Dimethoxy-1,10-phenanthroline (L) was found to be an efficient ligand for the copper-catalyzed N-arylation of imidazole with aryl iodides and bromides under mild conditions. A variety of hindered and functionalized imidazoles and aryl halides were transformed in good to excellent yields.

Novel 3,4-diarylpyrazolines as potent cannabinoid CB1 receptor antagonists with lower lipophilicity

Novel 3,4-diarylpyrazolines 1 as potent CB1 receptor antagonists with lipophilicity lower than that of SLV319 are described. The key change is the replacement of the arylsulfonyl group in the original series by a dialkylaminosulfonyl moiety. The absolute configuration (4S) of eutomer 24 was established by X-ray diffraction analysis and 24 showed a close molecular fit with rimonabant in a CB1 receptor-based model. Compound 17 exhibited the highest CB1 receptor affinity (Ki = 24 nM) in this series, as well as very potent CB1 antagonistic activity (pA2 = 8.8) and a high CB1/CB2 subtype selectivity (approximately 147-fold).

Recent developments in cannabinoid ligands

Over the past 40 years, much research has been carried out directed toward the characterization of the cannabinergic system. With the identification of two G-protein coupled receptors and the endogenous ligand, anandamide, pharmacological targets have expanded to encompass hydrolase and transport proteins as well as novel classes of cannabinoid ligands. Those ligands that demonstrate high affinity for the receptors and good biological efficacy are tied together through lipophilic regions repeatedly demonstrated necessary for activity. This review presents recent developments in the structure-activity relationships of several classes of cannabinoid ligands.

A Facile Solid-Phase Synthesis of 1,2,4,5-Tetrasubstituted Imidazoles Using Sodium Benzenesulfinate as a Traceless Linker

The preparation of substituted imidazoles, thiazoles, and oxazoles using traceless solid-phase sulfone linker strategy is described. Key steps involved are (i) sulfinate acidification, (ii) sulfinic acid condensation with aldehyde and amine, and (iii) traceless product release by a one-pot elimination-cyclization reaction. The elimination reaction was carried out in the presence of a thiazolium catalyst that facilitated the in situ formation of the alpha-ketoamide, which was subsequently converted to the corresponding imidazoles, oxazoles, and thiazoles by treatment with amines, PPh(3)/I(2) or Lawesson's reagent. A library of 18 compounds was synthesized.

Substituted 5,5'-diphenyl-2-thioxoimidazolidin-4-one as CB1 cannabinoid receptor ligands: synthesis and pharmacological evaluation

A set of 30 substituted 5,5'-diphenyl-2-thioxoimidazolidin-4-one (thiohydantoins) derivatives was synthesized, and their affinity for the human CB(1) cannabinoid receptor has been evaluated. These compounds are derived from the previously described cannabinoid ligands 5,5'-diphenylimidazolidine-2,4-dione (hydantoins). The replacement of the oxygen by a sulfur leads to an increase of the affinity while the function-i.e., inverse agonism-determined by [(35)S]GTPgammaS experiments remains unaffected. Finally, to evaluate the molecular parameters that could influence the affinity of the thiohydantoins, molecular electrostatic potential as well as lipophilicity calculations were undertaken on representative thiohydantoins and hydantoins derivatives. In conclusion, 5,5'-bis-(4-iodophenyl)-3-butyl-2-thioxoimidazolidin-4-one (31) and 3-allyl-5,5'-bis(4-bromophenyl)-2-thioxoimidazolidin-4-one (32) possess the highest affinity for the CB(1) cannabinoid receptor described to date for the hydantoin and thiohydantoins series when compared in a same bioassay.

Keynote review: Medicinal chemistry strategies to CB1 cannabinoid receptor antagonists

The proven clinical efficacy of the CB(1) cannabinoid receptor antagonist rimonabant in both obesity and smoking cessation and its therapeutic potential in other disorders has given a tremendous impetus to the discovery of novel CB(1) antagonists. The number of disclosed patents wherein novel chemical entities having CB(1) antagonistic or inverse agonistic properties have been claimed has exploded. Besides novel compound classes that were identified in screening, rational medicinal chemistry approaches such as conformational constraint and scaffold hopping have been successfully applied. CB(1) receptor modelling has provided insight into crucial receptor-ligand interaction points thereby leading to a general CB(1) inverse agonist pharmacophore model.