Novel Benzylated (Pyrrolidin-2-one)/(Imidazolidin-2-one) Derivatives as Potential Anti-Alzheimer's Agents: Synthesis and Pharmacological Investigations

The Benzoylpiperidine Fragment as a Privileged Structure in Medicinal Chemistry: A Comprehensive Review

The phenyl(piperidin-4-yl)methanone fragment (here referred to as the benzoylpiperidine fragment) is a privileged structure in the development of new drugs considering its presence in many bioactive small molecules with both therapeutic (such as anti-cancer, anti-psychotic, anti-thrombotic, anti-arrhythmic, anti-tubercular, anti-parasitic, anti-diabetic, and neuroprotective agents) and diagnostic properties. The benzoylpiperidine fragment is metabolically stable, and it is also considered a potential bioisostere of the piperazine ring, thus making it a feasible and reliable chemical frame to be exploited in drug design. Herein, we discuss the main therapeutic and diagnostic agents presenting the benzoylpiperidine motif in their structure, covering articles reported in the literature since 2000. A specific section is focused on the synthetic strategies adopted to obtain this versatile chemical portion.

The memory ameliorating effects of novel N-benzyl pyridine-2-one derivatives on scopolamine-induced cognitive deficits in mice

BACKGROUND

Alzheimer's disease (AD), the most common form of progressive dementia in the elderly, is a chronic neurological disorder that decreases cognitive ability. Although the underlying cause of AD is yet unknown, oxidative stress and brain acetylcholine shortage are the key pathogenic causes.

RESULTS

The current study shows that these derivatives have the potential to improve memory in mice by inhibiting scopolamine-induced acetylcholinesterase activity, oxidative and nitrosative stress, and improving locomotor activity and muscle grip strength in the rota rod test. When compared to the illness control, the memory-enhancing potential of novel N-benzyl pyridine-2-one derivatives was highly significant (P < 0.0001).

CONCLUSIONS

The observed memory ameliorating effect of novel N-benzyl pyridine-2-one makes them as a a good choice for treatment of individuals with cognitive impairment.

Discovery of Quinolinone Hybrids as Dual Inhibitors of Acetylcholinesterase and Aβ Aggregation for Alzheimer's Disease Therapy

The development of multitargeted therapeutics has evolved as a promising strategy to identify efficient therapeutics for neurological disorders. We report herein new quinolinone hybrids as dual inhibitors of acetylcholinesterase (AChE) and Aβ aggregation that function as multitargeted ligands for Alzheimer's disease. The quinoline hybrids (AM1-AM16) were screened for their ability to inhibit AChE, BACE1, amyloid fibrillation, α-syn aggregation, and tau aggregation. Among the tested compounds, AM5 and AM10 inhibited AChE activity by more than 80% at single-dose screening and possessed a remarkable ability to inhibit the fibrillation of Aβ42 oligomers at 10 μM. In addition, dose-dependent screening of AM5 and AM10 was performed, giving half-maximal AChE inhibitory concentration (IC50) values of 1.29 ± 0.13 and 1.72 ± 0.18 μM, respectively. In addition, AM5 and AM10 demonstrated concentration-dependent inhibitory profiles for the aggregation of Aβ42 oligomers with estimated IC50 values of 4.93 ± 0.8 and 1.42 ± 0.3 μM, respectively. Moreover, the neuroprotective properties of the lead compounds AM5 and AM10 were determined in SH-SY5Y cells incubated with Aβ oligomers. This work would enable future research efforts aiming at the structural optimization of AM5 and AM10 to develop potent dual inhibitors of AChE and amyloid aggregation. Furthermore, the in vivo assay confirmed the antioxidant activity of compounds AM5 and AM10 through increasing GSH, CAT, and SOD activities that are responsible for scavenging the ROS and restoring its normal level. Blood investigation illustrated the protective activity of the two compounds against lead-induced neurotoxicity through retaining hematological and liver enzymes near normal levels. Finally, immunohistochemistry investigation revealed the inhibitory activity of β-amyloid (Aβ) aggregation.

Investigation, scaffold hopping of novel donepezil-based compounds as anti-Alzhiemer's agents: synthesis, in-silico and pharmacological evaluations

Alzheimer's disease (AD) is a multifaceted neurodegenerative condition. The pathogenesis of AD is highly intricate and the disease is apparent in the aged population ~ 50-70 years old. Even after > 100 years of research, the root origin of AD and its pathogenesis is unclear, complex and multifaceted. Herein, we have designed and synthesized 9 novel molecules with three different heterocyclic scaffolds namely pyrrolidone-2-one, quinoline & indoline-2-one to imitate and explore the novel chemical space around donepezil. The synthesized molecules were evaluated for their potential as anti-Alzheimer's agents through in-vitro and in-vivo studies in appropriate animal models. To further understand their interaction with acetylcholinesterase enzyme (AChE), extra-precision docking, and molecular dynamics simulation studies were carried out. As the number of compounds was limited to thoroughly explore the structure-activity relationship, atom-based 3D-quantitative structure-activity relationships (QSAR) studies were carried out to get more insights. All the designed compounds were found to inhibit AChE with IC50 in the micromolar range. From pyrrolidone-2-one series, 6-chloro-N-(1-(1-(3,4-dimethoxybenzyl)-2-oxopyrrolidin-3-yl)piperidin-4-yl)pyridine-3-sulfonamide (9), 2-(1-benzylpiperidin-4-yl)-6,7-dimethoxy-4-(4-methoxyphenyl)quinoline (18) from quinoline series and N-(1-benzylpiperidin-4-yl)-2-(2-oxoindolin-3-yl)acetamide (23) from indolin-2-one series inhibited AChE with an IC50 value of 0.01 µM. Based on other biochemical studies like lipid peroxidation, reduced glutathione, superoxide dismutase, catalase, nitrite, and behavioural studies (Morris water maze), compound 9 was found to be a potent AChE inhibitor which can be further explored as a lead molecule to design more potent and effective anti-Alzheimer's agents.

Design, Synthesis, and Biological Evaluation of Piperazine and N-Benzylpiperidine Hybrids of 5-Phenyl-1,3,4-oxadiazol-2-thiol as Potential Multitargeted Ligands for Alzheimer's Disease Therapy

Our present work demonstrates the successful design and synthesis of a new class of compounds based upon a multitargeted directed ligand design approach to discover new agents for use in Alzheimer's disease (AD). All the compounds were tested for their in vitro inhibitory potential against human acetylcholinesterase (hAChE), human butylcholinesterase (hBChE), β-secretase-1 (hBACE-1), and amyloid β (Aβ) aggregation. Compounds 5d and 5f have shown hAChE and hBACE-1 inhibition comparable to donepezil, while hBChE inhibition was comparable to rivastigmine. Compounds 5d and 5f also demonstrated a significant reduction in the formation of Aβ aggregates through the thioflavin T assay and confocal, atomic force, and scanning electron microscopy studies and significantly displaced the total propidium iodide, that is, 54 and 51% at 50 μM concentrations, respectively. Compounds 5d and 5f were devoid of neurotoxic liabilities against RA/BDNF (RA = retinoic acid; BDNF = brain-derived neurotrophic factor)-differentiated SH-SY5Y neuroblastoma cell lines at 10-80 μM concentrations. In both the scopolamine- and Aβ-induced mouse models for AD, compounds 5d and 5f demonstrated significant restoration of learning and memory behaviors. A series of ex vivo studies of hippocampal and cortex brain homogenates showed that 5d and 5f elicit decreases in AChE, malondialdehyde, and nitric oxide levels, an increase in glutathione level, and reduced levels of pro-inflammatory cytokines, tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) mRNA. The histopathological examination of mice revealed normal neuronal appearance in the hippocampal and cortex regions of the brain. Western blot analysis of the same tissue indicated a reduction in Aβ, amyloid precursor protein (APP)/Aβ, BACE-1, and tau protein levels, which were non-significant compared to the sham group. The immunohistochemical analysis also showed significantly lower expression of BACE-1 and Aβ levels, which was comparable to donepezil-treated group. Compounds 5d and 5f represent new lead candidates for developing AD therapeutics.

The Antiarrhythmic and Hypotensive Effects of S-61 and S-73, the Pyrrolidin-2-one Derivatives with α1-Adrenolytic Properties

Heart rhythm abnormalities are a cause of many deaths worldwide. Unfortunately, the available antiarrhythmic drugs show limited efficacy and proarrhythmic potential. Thus, efforts should be made to search for new, more effective, and safer pharmacotherapies. Several studies suggested that blocking the α₁-adrenoceptors could restore normal heart rhythm in arrhythmia. In this study, we aimed to assess the antiarrhythmic potential of S-61 and S-73, two novel pyrrolidin-2-one derivatives with high affinity for α₁-adrenergic receptors. First, using radioligand binding studies, we demonstrated that S-61 and S-73 did not bind with β₁-adrenoceptors. Next, we assessed whether S-61 and S-73 could protect rats against arrhythmia in adrenaline-, calcium chloride- and aconitine-induced arrhythmia models. Both compounds showed potent prophylactic antiarrhythmic properties in the adrenaline-induced arrhythmia model, but the effect of S-61 was more pronounced. None of the compounds displayed antiarrhythmic effects in calcium chloride- or aconitine-induced arrhythmia models. Interestingly, both derivatives revealed therapeutic antiarrhythmic activity in the adrenaline-induced arrhythmia, diminishing heart rhythm irregularities. Neither S-61 nor S-73 showed proarrhythmic potential in rats. Finally, the compounds decreased blood pressure in rodents. The hypotensive effects were not observed after coadministration with methoxamine, which suggests the α₁-adrenolytic properties of both compounds. Our results confirm that pyrrolidin-2-one derivatives possess potent antiarrhythmic properties. Given the promising results of our experiments, further studies on pyrrolidin-2-one derivatives might result in the development of a new class of antiarrhythmic drugs.

Design, synthesis, extra-precision docking, and molecular dynamics simulation studies of pyrrolidin-2-one derivatives as potential acetylcholinesterase inhibitors

Inhibition of acetylcholinesterase (AChE) has been widely explored to develop novel molecules for management of Alzheimer's disease. In past research finding reported molecule 3-(4-(4-fluorobenzoyl)piperidin-1-yl)-1-(4-methoxybenzyl)pyrrolidin-2-one displayed a spectrum of anti-Alzheimer's properties herein, we report a library of 18 novel molecules that were rationally designed and synthesized employing known literature to mimic and explore the novel chemical space around the lead compound 6e and donepezil. All the compounds were docked in extra-precision mode with AChE (PDB ID 4EY7) using the Glide module. Molecular dynamics (MD) simulation studies were carried out for 100 ns along with MM-PBSA studies of the trajectory frames generated post-MD simulations. Docking and MD simulation studies suggested that the synthesized compounds showed a good binding affinity with AChE. and might form stable complexes. 3-(4-(benzyl(methyl)amino)piperidin-1-yl)-1-(3,4-dimethoxybenzyl)pyrrolidin-2-one (14a; docking score: -18.59) and 1-(3,4-dimethoxybenzyl)-3-(4-(methyl(thiazol-2-ylmethyl)amino)piperidin-1-yl)pyrrolidin-2-one (14d; docking score: -18.057) showed higher docking score than donepezil (docking score: -17.257) while most of the compounds had docking score >-10.0. ADMET study predicted these compounds to be CNS active and most of the compounds were drug-like molecules with no HERG blockade and good to excellent oral absorption. We developed an atom-based 3 D-QSAR model with R^2 and Q^2 values of 0.9639 and 0.8779 to predict the activity of the synthesized compounds. The model predicted these compounds to be potent AChE inhibitors with IC₅₀ values in the lower micromolar range. Based on the in silico findings, we report these newly synthesized compounds 3-(4-(benzyl(methyl)amino)piperidin-1-yl)-1-(3,4-dimethoxybenzyl)pyrrolidin-2-one (14a) and 7-(2,6-difluorobenzyl)-2-(4-methoxybenzyl)-2,7-diazaspiro[4.5]decan-1-one (20 b) as potential AChE inhibitors.Communicated by Ramaswamy H. Sarma.

Design, Synthesis, and Evaluation of Isoindoline Derivatives as New Antidepressant Agents

Background:

Isoindoline derivatives exhibit a wide range of biological activities and have attracted considerable attention. However, few studies have been conducted on their antidepressant activity.

Objective:

Here, we designed and synthesized a series of isoindoline derivatives and studied their antidepressant activities.

Method:

Forced swimming test (FST) and tail suspension test (TST) were used to evaluate the antidepressant activity of the target compounds. The most active compound was used to evaluate the exploratory activity of the animals by the open-field test. 5-HT concentration was estimated to evaluate if the compound has an effect on the mice brain by using ELISA. The biological activities of the compounds were verified by molecular docking studies. The pharmacokinetic properties of the target compounds were predicted by Discovery Studio (DS) 2020.

Results:

The results of the pharmacological experiments showed that most isoindoline derivatives exhibited significant antidepressant activity. Among these compounds, compound 4j showed the highest antidepressant activity. The results of the measurement of 5-HT levels in the brains of mice indicate that the antidepressant activity of isoindoline derivatives may be mediated by elevated 5-HT levels. Compound 4j was used in molecular docking experiments to simulate the possible interaction of these compounds with the 5-HT1A receptor. The results demonstrated that compound 4j had a significant interaction with amino acids around the active site of the 5-HT1A receptor in the homology model.

Conclusion:

Isoindoline derivatives synthesized in this study have a significant antidepressant activity. These findings can be useful in the design and synthesis of novel antidepressants.

Construction of Azacycles by Intramolecular Amination of Organoboronates and Organobis(boronates)

Intramolecular amination of organoboronates occurs with a 1,2-metalate shift of an aminoboron "ate" complex to form azetidines, pyrrolidines, and piperidines. Bis(boronates) undergo site-selective amination to form boronate-containing azacycles. Enantiomerically enriched azacycles are formed with high stereospecificity.

The recent development of donepezil structure-based hybrids as potential multifunctional anti-Alzheimer's agents: highlights from 2010 to 2020

Dementia is a term used to define different brain disorders that affect memory, thinking, behavior, and emotion. Alzheimer's disease (AD) is the second cause of dementia that is generated by the death of cholinergic neurons (especially acetylcholine (ACh)), which have a vital role in cognition. Acetylcholinesterase inhibitors (AChEI) affect acetylcholine levels in the brain and are broadly used to treat Alzheimer's. Donepezil, rivastigmine, and galantamine, which are FDA-approved drugs for AD, are cholinesterase inhibitors. In addition, scientists are attempting to develop hybrid molecules and multi-target-directed ligands (MTDLs) that can simultaneously modulate multiple biological targets. This review highlights recent examples of MTDLs and fragment-based strategy in the rational design of new potential AD medications from 2010 onwards.

This review highlights recent examples of multi-target-directed ligands (MTDLs) based on donepezil structure modification from 2010 onwards.