Chiral picolylamines for Michael and aldol reactions: probing substrate boundaries

Modification of 4-(4-chlorothiophen-2-yl)thiazol-2-amine derivatives for the treatment of analgesia and inflammation: synthesis and in vitro, in vivo, and in silico studies

Inflammation is a protective response to a variety of infectious agents. To develop a new anti-inflammatory drug, we explored a pharmacologically important thiazole scaffold in this study. In a multi-step synthetic approach, we synthesized seven new thiazole derivatives (5a-5g). Initially, we examined the in vitro anti-inflammatory potentials of our compounds using COX-1, COX-2, and 5-LOX enzyme assays. After in vitro confirmation, the potential compounds were subjected to in vivo analgesic and anti-inflammatory studies. The hot plate method was used for analgesia, and carrageenan-induced inflammation was also assayed. Overall, all our compounds proved to be potent inhibitors of COX-2 compared to celecoxib (IC50 0.05 μM), exhibiting IC50 values in the range of 0.76-9.01 μM .Compounds 5b, 5d, and 5e were dominant and selective COX-2 inhibitors with the lowest IC50 values and selectivity index (SI) values of 42, 112, and 124, respectively. Similarly, in the COX-1 assay, our compounds were relatively less potent but still encouraging. Standard aspirin exhibited an IC50 value of 15.32 μM. In the 5-LOX results, once again, compounds 5d and 5e were dominant with IC50 values of 23.08 and 38.46 μM, respectively. Standard zileuton exhibited an IC50 value of 11.00 μM. Based on the COX/LOX and SI potencies, the compounds 5d and 5e were subjected to in vivo analgesic and anti-inflammatory studies. Compounds 5d and 5e at concentrations of 5, 10, and 20 mg/kg body weight were significant in animal models. Furthermore, we explored the potential role of compounds 5d and 5e in various phlogistic agents. Similarly, both compounds 5d and 5e were also significantly potent in the anti-nociceptive assay. The molecular docking interactions of these two compounds with the target proteins of COX and LOX further strengthened their potential for use in COX/LOX pathway inhibitions.

New Succinimide-Thiazolidinedione Hybrids as Multitarget Antidiabetic Agents: Design, Synthesis, Bioevaluation, and Molecular Modelling Studies

Diabetes mellitus (DM) is a metabolic disorder majorly arising from the pathophysiology of the pancreas manifested as a decline in the insulin production or the tissue's resistance to the insulin. In this research, we have rationally designed and synthesized new succinimide-thiazolidinedione hybrids for the management of DM. In a multistep reaction, we were able to synthesize five new derivatives (10a-e). All the compounds were new containing a different substitution pattern on the N-atom of the succinimide ring. Initially, all the compounds were tested against the in vitro α-glucosidase, α-amylase, PTP1B, and DPP4 targets. In all of these targets, the compound 10d was observed to be the most potential antidiabetic agent. Based on this, the antidiabetic activity of the compound 10d was further investigated in experimental animals, which overall gave us encouraging results. The molecular docking studies of the compound 10d was also performed against the target enzymes α-glucosidase, α-amylase, PTP1B, and DPP4 using MOE. Overall, we observed that we have explored a new class of compounds as potential antidiabetic agents.

Synthesis, Molecular Docking, and Preclinical Evaluation of a New Succinimide Derivative for Cardioprotective, Hepatoprotective and Lipid-Lowering Effects

Cardiac and hepatotoxicities are major concerns in the development of new drugs. Better alternatives to other treatments are being sought to protect these vital organs from the toxicities of these pharmaceuticals. In this regard, a preclinical study is designed to investigate the histopathological effects of a new succinimide derivative (Comp-1) on myocardial and liver tissues, and the biochemical effects on selected cardiac biomarkers, hepatic enzymes, and lipid profiles. For this, an initially lethal/toxic dose was determined, followed by a grouping of selected albino rats into five groups (each group had n = 6). The control group received daily oral saline for 8 days. The 5-FU (5-Fluorouracil) group received oral saline daily for 8 days, added with the administration of a single dose of 5-FU (150 mg/kg I.P.) on day 5 of the study. The atenolol group received oral atenolol (20 mg/kg) for 8 days and 5-FU (150 mg/kg I.P.) on day 5 of the protocol. Similarly, two groups of rats treated with test compound (Comp-1) were administered with 5 mg/kg I.P. and 10 mg/kg I.P. for 8 days, followed by 5-FU (150 mg/kg I.P.) on day 5. Toxicity induced by 5-FU was manifested by increases in the serum creatinine kinase myocardial band (CK-MB), troponin I (cTnI) and lactate dehydrogenase (LDH), lipid profile, and selected liver enzymes, including ALP (alkaline phosphatase), ALT (alanine transaminase), AST (aspartate aminotransferase), BT (bilirubin total), and BD (direct bilirubin). These biomarkers were highly significantly decreased after the administration of the mentioned doses of the test compound (5 mg/kg and 10 mg/kg). Similarly, histological examination revealed cardiac and hepatic tissue toxicity by 5-FU. However, those toxic effects were also significantly recovered/improved after the administration of Comp-1 at the said doses. This derivative showed dose-dependent effects and was most effective at a dose of 10 mg/kg body weight. Binding energy data computed via docking simulations revealed that our compound interacts toward the human beta2-adrenergic G protein-coupled receptor (S = −7.89 kcal/mol) with a slight stronger affinity than the calcium channel T-type (S = −7.07 kcal/mol). In conclusion, the histological and biochemical results showed that the test compound (Comp-1) had prominent cardioprotective, hepatoprotective, and lipolytic effects against 5-FU-induced toxicity in the subjected animal model.

Anti-Inflammatory Potentials of β-Ketoester Derivatives of N-Ary Succinimides: In Vitro, In Vivo, and Molecular Docking Studies

Inflammation, being a well-known and complex pathological condition, is always a challenge to the human health. This research work was designed for a rationale-based anti-inflammatory study on β-ketoester derivatives of N-ary succinimides. The compounds (A–D) were synthesized by organocatalytic Michael addition. The compounds were initially screened for in vitro 5-lipoxygenase (5-LOX) and cyclooxygenase (COX-2) assays. For the in vivo activity, carrageenan-induced paw edema and arachidonic acid-induced ear edema tests were used. Furthermore, different in vivo pathways such as prostaglandins E2, histamine, leukotriene, and bradykinin were studied. The results were supported with molecular docking studies. Among the compounds, D (ethyl 1-(1-benzyl-2,5-dioxopyrrolidin-3-yl)-2-oxocyclohexane-1-carboxylate) at a concentration of 1000 μg/ml showed significant inhibitory effects of 83.67% and 78.12% against COX-2 and 5-LOX in comparison to celecoxib and zileuton, respectively. Similarly, compound D also showed excellent in vivo anti-inflammatory potential. Amongst all the compounds, D demonstrated excellent (55.92 ± 2.95%) anti-inflammatory potential at maximum tested dose (100 mg/kg) which accomplished the highest significance at 4 h following the carrageenan insertion and stayed considerable ( ${}^{\ast \ast \ast }P<0.001$ ) till the 5th hour of test sample injection. Compound D also exhibited excellent percent inhibition (63.81 ± 2.24%) at the highest dose in arachidonic acid-induced ear inflammation. On the basis of in vivo and in vitro results, compound D was subjected to various inflammation-causing agents such as histamine, prostaglandins E2, bradykinin, and leukotriene via the mouse paw edema test. Compound D revealed moderate effect (28.10 ± 1.64%) against histamine-induced paw edema while nonsignificant result (9.72 ± 3.125%) was marked for the bradykinin pathway. Compound D showed significance against edematogenic consequence of prostaglandin E2 (56.28–72.03%) and leukotriene (55.13 ± 2.25%) induced inflammation. In summary, our findings recommended that compound D possesses double acting anti-inflammatory properties inhibiting both COX and LOX pathways. Binding orientations and energy values computed via docking simulations support the results of the experimental in vitro evaluation.

Anti-Inflammatory, Analgesic and Antioxidant Potential of New (2S,3S)-2-(4-isopropylbenzyl)-2-methyl-4-nitro-3-phenylbutanals and Their Corresponding Carboxylic Acids through In Vitro, In Silico and In Vivo Studies

In the current study, a series of new (2S,3S)-2-(4-isopropylbenzyl)-2-methyl-4-nitro-3-phenylbutanals (FM1-6) with their corresponding carboxylic acid analogues (FM7-12) has been synthesized. Initially, the aldehydic derivatives were isolated in the diastereomeric form, and the structures were confirmed with NMR, MS and elemental analysis. Based on the encouraging results in in vitro COX 1/2, 5-LOX and antioxidant assays, we oxidized the compounds and obtained the pure single (major) diastereomer for activities. Among all the compounds, FM4, FM10 and FM12 were the leading compounds based on their potent IC₅₀ values. The IC₅₀ values of compounds FM4, FM10 and FM12 were 0.74, 0.69 and 0.18 µM, respectively, in COX-2 assay. Similarly, the IC₅₀ values of these three compounds were also dominant in COX-1 assay. In 5-LOX assay, the majority of our compounds were potent inhibitors of the enzyme. Based on the potency and safety profiles, FM10 and FM12 were subjected to the in vivo experiments. The compounds FM10 and FM12 were observed with encouraging results in in vivo analgesic and anti-inflammatory models. The molecular docking studies of the selected compounds show binding interactions in the minimized pocked of the target proteins. It is obvious from the overall results that FM10 and FM12 are potent analgesic and anti-inflammatory agents.

α-Glucosidase, α-Amylase and Antioxidant Evaluations of Isolated Bioactives from Wild Strawberry

Diabetes mellitus is a metabolic disorder and is a global challenge to the current medicinal chemists and pharmacologists. This research has been designed to isolate and evaluate antidiabetic bioactives from Fragaria indica. The crude extracts, semi-purified and pure bioactives have been used in all in vitro assays. The in vitro α-glucosidase, α-amylase and DPPH free radical activities have been performed on all plant samples. The initial activities showed that ethyl acetate (Fi.EtAc) was the potent fraction in all the assays. This fraction was initially semi-purified to obtain Fi.EtAc 1–3. Among the semi-purified fractions, Fi.EtAc 2 was dominant, exhibiting potent IC₅₀ values in all the in vitro assays. Based on the potency and availability of materials, Fi.EtAc 2 was subjected to further purification to obtain compounds 1 (2,4-dichloro-6-hydroxy-3,5-dimethoxytoluene) and 2 (2-methyl-6-(4-methylphenyl)-2-hepten-4-one). The two isolated compounds were characterized by mass and NMR analyses. The compounds 1 and 2 showed excellent inhibitions against α-glucosidase (21.45 for 1 and 15.03 for 2 μg/mL), α-amylase (17.65 and 16.56 μg/mL) and DPPH free radicals (7.62 and 14.30 μg/mL). Our study provides baseline research for the antidiabetic bioactives exploration from Fragaria indica. The bioactive compounds can be evaluated in animals-based antidiabetic activity in future.

3-(((1S,3S)-3-((R)-Hydroxy(4-(trifluoromethyl)phenyl)methyl)-4-oxocyclohexyl)methyl)pentane-2,4-dione: Design and Synthesis of New Stereopure Multi-Target Antidiabetic Agent

The chiral drug candidates have more effective binding affinities for their specific protein or receptor site for the onset of pharmacological action. Achieving all carbon stereopure compounds is not trivial in chemical synthesis. However, with the development of asymmetric organocatalysis, the synthesis of certain vital chiral drug candidates is now possible. In this research, we have synthesized 3-(((1S,3S)-3-((R)-hydroxy(4-(trifluoromethyl)phenyl)methyl)-4-oxocyclohexyl)methyl)pentane-2,4-dione (S,S,R-5) and have evaluated it potential as multi-target antidiabetic agent. The stereopure compound S,S,R-5 was synthesized with a 99:1 enantiomeric ratio. The synthesized compound gave encouraging results against all in vitro antidiabetic targets, exhibiting IC₅₀ values of 6.28, 4.58, 0.91, and 2.36 in α-glucosidase, α-amylase, PTP1B, and DPPH targets, respectively. The molecular docking shows the binding of the compound in homology models of the respective enzymes. In conclusion, we have synthesized a new chiral molecule (S,S,R-5). The compound proved to be a potential inhibitor of the tested antidiabetic targets. With the observed results and molecular docking, it is evident that S,S,R-5 is a potential multitarget antidiabetic agent. Our study laid the baseline for the animal-based studies of this compound in antidiabetic confirmation.

Crude extract and isolated bioactive compounds from Notholirion thomsonianum (Royale) Stapf as multitargets antidiabetic agents: in-vitro and molecular docking approaches

Background

Diabetes mellitus is a common disease effecting the lifestyles of majority world population. In this research work, we have embarked the potential role of crude extracts and isolated compounds of Notholirion thomsonianum for the management diabetes mellitus.

Methods

The crude extracts of N. thomsonianum were initially evaluated for α-glucosidase, α-amylase and antioxidant activities. The compounds were isolated from the activity based potent solvent fraction. The structures of isolated compounds were confirmed with NMR and MS analyses. The isolated compounds were tested for α-glucosidase, α-amylase, protein tyrosine phosphatase 1B (PTP1B) and DPPH activities. The molecular docking studies were carried out to find the binding interactions of isolated compounds for α-glucosidase, α-amylase and PTP1B.

Results

Initially, we screened out crude extracts and subfractions of N. thomsonianum against different in-vitro targets. Among all, Nt.EtAc was observed a potent fraction among all giving IC₅₀ values of 67, 70, < 0.1, 89 and 16 μg/mL against α-glucosidase, α-amylase, DPPH, ABTS and H₂O₂ respectively. Three compounds (Nt01, Nt02 and Nt03) were isolated from Nt.EtAc of N. thomsonianum. The isolated compounds Nt01, Nt02 and Nt03 exhibited IC₅₀ values of 58.93, 114.93 and 19.54 μM against α-glucosidase, while 56.25, 96.54 and 24.39 μM against α-amylase respectively. Comparatively, the standard acarbose observed IC₅₀ values were 10.60 and 12.71 μM against α-glucosidase, α-amylase respectively. In PTP1B assay, the compounds Nt01, Nt02 and Nt03 demonstrated IC₅₀ values of 12.96, 36.22 and 3.57 μM in comparison to the standard ursolic acid (IC₅₀ of 3.63 μM). The isolated compounds also gave overwhelming results in DPPH assay. Molecular docking based binding interactions for α-glucosidase, α-amylase and PTP1B were also encouraging.

Conclusions

In the light of current results, it is obvious that N. thomsonianum is potential medicinal plant for the treatment of hyperglycemia. Overall, Nt.EtAc was dominant fraction in all in-vitro activities. Three compounds Nt01, Nt02 and Nt03 were isolated from ethyl acetate fraction. The Nt03 specifically was most potent in all in-vitro assays. The molecular docking studies supported our in-vitro results. It is concluded that N. thomsonianum is a rich source of bioactive antidiabetic compounds which can be further extended to in-vivo based experiments.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03443-7.

Synthesis of Michael Adducts as Key Building Blocks for Potential Analgesic Drugs: In vitro, in vivo and in silico Explorations

Background

Organocatalytic asymmetric Michael addition is a strong approach for C-C bond formation. The objective of the study is to design molecules by exploiting the efficiency of Michael Adducts. We proceeded with the synthesis of Michael adducts by tailoring the substitution pattern on maleimide and trans-β-nitro styrene as Michael acceptors. The synthesized compounds were evaluated for dual cyclooxygenases (COX) and lipoxygenase (LOX) inhibition.

Methods

The compounds (4, 9–11) were synthesized through Michael additions. The cyclooxygenases (COX-1 and 2) and lipoxygenase (5-LOX) assays were used for in vitro evaluations of compounds. After the acute toxicity studies, the in vivo analgesic potential was determined with acetic acid induced writhing, tail immersion, and formalin tests. Furthermore, the possible roles of adrenergic and dopaminergic receptors were also studied. Extensive computational studies were performed to get a better understanding regarding the binding of this compound with protein target.

Results

Four Michael adducts (4, 9–11) were synthesized. Compound 4 was obtained in enantio- and diastereopure form. The stereopure compound 4 showed encouraging COX-1 and-2 inhibitions with IC₅₀ values of 128 and 65 μM with SI of 1.94. Benzyl derivative 11 showed excellent COX-2 inhibition with the IC₅₀ value of 5.79 μM and SI value 7.96. Compounds 4 and 11 showed good results in in vivo models of analgesia like acetic acid test, tail immersion, and formalin tests. Our compounds were not active in dopaminergic and adrenergic pathways and so were acting centrally. Through extensive computational studies, we computed binding energies, and pharmacokinetic predictions.

Conclusion

Our findings conclude that our synthesized Michael products (pyrrolidinedione 4 and nitroalkane 11) can be potent centrally acting analgesics. Our in silico predictions suggested that the compounds have excellent pharmacokinetic properties. It is concluded here that dual inhibition of COX/LOX pathways provides a convincing step towards the discovery of safe lead analgesic molecules.

Comparative Cholinesterase, α-Glucosidase Inhibitory, Antioxidant, Molecular Docking, and Kinetic Studies on Potent Succinimide Derivatives

Introduction

The current study was designed to synthesize derivatives of succinimide and compare their biological potency in anticholinesterase, alpha-glucosidase inhibition, and antioxidant assays.

Methods

In this research, two succinimide derivatives including (S)-1-(2,5-dioxo-1-phenylpyrrolidin-3-yl) cyclohexanecarbaldehyde (Compound 1) and (R)-2-((S)-2,5-dioxo-1-phenylpyrrolidin-3-yl)-2-phenylpropanal (Compound 2) were synthesized using Michael addition. Both the compounds, ie, 1 and 2 were evaluated for in-vitro acetylcholinesterase (AChE), butyrylctcholinesterase (BChE), antioxidant, and α-glucosidase inhibitory potentials. Furthermore, molecular docking was performed using Molecular Operating Environment (MOE) to explore the binding mode of both the compounds against different enzymes. Lineweaver-Burk plots of enzyme inhibitions representing the reciprocal of initial enzyme velocity versus the reciprocal of substrate concentration in the presence of synthesized compounds and standard drugs were constructed using Michaelis-Menten kinetics.

Results

In AChE inhibitory assay, compounds 1 and 2 exhibited IC₅₀ of 343.45 and 422.98 µM, respectively, against AChE enzyme. Similarly, both the compounds showed IC₅₀ of 276.86 and 357.91 µM, respectively, against BChE enzyme. Compounds 1 and 2 displayed IC₅₀ of 157.71 and 471.79 µM against α-glucosidase enzyme, respectively. In a similar pattern, compound 1 exhibited to be more potent as compared to compound 2 in all the three antioxidant assays. Compound 1 exhibited IC₅₀ values of 297.98, 332.94, and 825.92 µM against DPPH, ABTS, and H₂O₂ free radicals, respectively. Molecular docking showed a triple fold in the AChE and BChE activity for compound 1 compared with compound 2. The compound 1 revealed good interaction against both the AChE and BChE enzymes which revealed the high potency of this compound compared to compound 2.

Conclusion

Both succinimide derivatives exhibited considerable inhibitory activities against cholinesterases and α-glucosidase enzymes. Of these two, compound 1 revealed to be more potent against all the in-vitro targets which was supported by molecular docking with the lowest binding energies. Moreover, compound 1 also proved to have antiradical properties.

SAR based in-vitro anticholinesterase and molecular docking studies of nitrogenous progesterone derivatives

Progesterone is a steroidal hormone that has been described with pathogenic features of brain dysfunction, realized with advanced age-related neurodegenerative diseases such as Alzheimer's disease. In this study, sixteen nitrogenous derivatives of progesterone which we previously synthesized have been used for Alzheimer targets. The progesterone derivatives (1-16) were screened for their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory potentials in a dose-dependent manner. All the compounds exhibited overwhelming AChE inhibitions, with IC₅₀ values ranging from 14.40 to 40.37 μM. Similarly, the BChE inhibitory potentials of our compounds were also dominant with IC₅₀values between 20.08 and 46.84 μM. In comparison to our compounds, the standard drug galantamine attain IC₅₀ values of 12.03 and 18.20 μM against AChE and BChE respectively. Molecular docking studies suggested that the compounds exerted their inhibitory activity by binding to the active site of the enzyme. The cholinergic system plays an important role in the regulation of learning and memory processes and has been a major target for the design of anti-Alzheimer's drugs. Therefore, these nitrogen-containing progesterone derivatives will be of potential interest to researchers working in AD for developing new drugs or chemical tools to study the disease.

Pharmacological Evaluation of Aldehydic-Pyrrolidinedione Against HCT-116, MDA-MB231, NIH/3T3, MCF-7 Cancer Cell Lines, Antioxidant and Enzyme Inhibition Studies

Purpose

The current work was designed to synthesize a bioactive derivative of succinimide and evaluate it for anti-Alzheimer, anticancer and anti-diabetic potentials.

Methods

The compound was synthesized by Michael addition of butyraldehyde with N-phenylmaleimide. The synthesized compound was screened for biological potentials including anti-cholinesterase, in-vitro anti-diabetic, antioxidant and anthelmintic potentials. The anti-cholinesterase potential was evaluated against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), anti-diabetic potential against α-glucosidase, antioxidant potential against ABTS, DPPH and H₂O₂ and anthelmintic potential against Perethima posthuma and Ascaridia galli respectively.

Results

The compound demonstrated significant AChE and BChE inhibition i.e., 71.34±1.92 and 73.42 ±1.92 at the concentration of 1000 µg/mL respectively. Other dilutions exhibited concentration-dependent inhibitory activity against both enzymes. In the MTT assay, the newly synthesized compound was found active against all of the cell lines viz, HCT-116, MDA-MB231, NIH/3T3 and MCF-7 and the highest cytotoxicity potential was observed against the colon cancer cell line (HCT-116) with an IC₅₀ value of 78 µg/mL exhibiting its highest potential. Moreover, the compound exhibited prominent α-glucosidase inhibitory potentials (79.86±2.54% at 1000 µg/mL) with IC₅₀ value of 156.23 µg/mL. Further, our test compound exhibited considerable scavenging activity against DPPH, ABTS and H₂O₂ free radicals with percent inhibitions of 75.84±1.58, 72.85±1.17 and 54.82±1.82 and IC₅₀ values of 84.36, 139.74 and 752.21 µg/mL respectively. Our test sample exhibited significant anthelmintic potentials. It demonstrated significant paralysis and death of the test worms in an unbelievably short time in comparison with albendazole.

Conclusion

Going into the detail of all observations, it may be deduced that the newly synthesized succinimide derivative could be an important drug candidate against neurodegenerative disorders like Alzheimer's disease, cancer, diabetes mellitus and worms. Further detailed studies in animal models are required for in-vivo analysis of the compound.

Design, synthesis, in-vitro, in-vivo and in-silico studies of pyrrolidine-2,5-dione derivatives as multitarget anti-inflammatory agents

In recent years, drug discovery paradigm has been shifted from conventional single target inhibition toward multitarget design concept. In current research, we have reported synthesis, in-vitro, in-vivo and acute toxicity determination of N-substituted pyrrolidine-2,5-dione derivatives as multitarget anti-inflammatory agents. We synthesized cycloalkyl, alkyl and aryl carbonyl derivatives by the Michael addition of ketones to N-substituted maleimides using self-assembled three component system as an organocatalyst. Anti-inflammatory potential of the compounds was determined by using different in-vitro assays, like cyclooxygenase-1, cyclooxygenase-2 and 5-lipoxygenase, albumin denaturation and anti-protease assays. Amongst the synthesized compounds, 13a-e series of compounds showed inhibition in low micromolar to submicromolar ranges. These compounds also demonstrated COX-2 selectivity. Compound 13e with IC₅₀ value 0.98 μM and SI of 31.5 emerged as the most potent inhibitor of COX-2. Based on in-vitro results, in-vivo anti-inflammatory investigations were performed on compounds 3b and 13evia carrageenan induced paw edema test. The possible mode of action of compounds 3b and 13e were ascertained with various mediators like histamine, bradykinin, prostaglandin and leukotriene. In-vivo acute toxicity study showed the safety of synthesized compounds up to 1000 mg/kg dose. The selectivity of the compounds against cyclooxygenase isoforms was supported by docking simulations. Selective COX-2 inhibitors showed significant interactions with the amino acid residues present in additional secondary COX-2 enzyme pocket. Furthermore, in-silico pharmacokinetic predictions confer the drug-like characteristics.

Synthesis, anticholinesterase and antioxidant potentials of ketoesters derivatives of succinimides: a possible role in the management of Alzheimer's

Background

Based on the pharmacological potency and structural features of succinimides, this study was designed to synthesize new ketoesters derivatives of succinimides. Furthermore, the synthesized compounds were evaluated for their possible anticholinesterase and antioxidant potentials. The compounds were synthesized by organocatalytic Michael additions of α-ketoesters to N-aryl maleimides. Acetyl and butyrylcholinesterase inhibitory activities were determined using Ellman’s spectrophotometric assay. The antioxidant activity was performed with DPPH and ABTS free radicals scavenging assay.

Results

The Michael additions of α-ketoesters to maleimides was promoted by 8-hydroxyquinoline. The organocatalyst (8-hydroxyquinoline, 20 mol %) produced the compounds in relatively shorter time (20–24 h) and with excellent isolated yields (84-98 %). The synthesized compounds (1–4) showed outstanding acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory potentials, i.e., 98.75 and 90.00 % respectively for compound 2, with IC₅₀ < 0.1 μg/mL. Additionally, compounds 1–4 revealed moderate antioxidant activity at different concentrations. In DPPH free radical scavenging assay, compound 1 showed dominant result with 72.41 ± 0.45, 52.49 ± 0.78 and 35.60 ± 0.75 % inhibition at concentrations of 1000, 500 and 250 μg/mL respectively, IC₅₀ value of 440 μg/mL. However, the free radical scavenging was better when used ABTS free radicals. In ABTS free radicals scavenging assay compound 1 exhibited 88.51 ± 0.62 % inhibition at highest tested concentration i.e., 1000 μg/mL.

Conclusions

Herein, we have synthesized four ketoesters derivatives of succinimides in a single step reaction and high yields. As a highlight, we have showed a first report on the anticholinesterase and antioxidant potentials of succinimides. All the compounds showed overwhelming enzyme inhibitions and moderate antioxidant potentials.

Graphical Abstract

Asymmetric synthesis of substituted NH-piperidines from chiral amines

Previously, we reported an efficient asymmetric synthesis of substituted piperidines through an exocyclic chirality induced nitroalkene/amine/enone (NAE) condensation reaction. An effective protecting group strategy was developed herein to achieve enantiopure piperidines (yields up to 92%) with complete chirality retention (ee > 95%). A simple derivatization of the obtained piperidines gave thiourea catalysts, indicating the strong potential of this method for producing new amine-based dual functional organocatalysts for future development.

Synthesis of γ-nitroaldehydes containing quaternary carbon in the α-position using a 4-oxalocrotonate tautomerase whole-cell biocatalyst

Synthetically valuable quaternary carbon containing γ-nitroaldehydes were obtained from branched chain aldehydes and a range of α,β-unsaturated nitroalkenes by a whole-cell biocatalytic reaction using 4-oxalocrotonate tautomerase as catalyst.