Noncovalent Bifunctional Organocatalysts: Powerful Tools for Contiguous Quaternary-Tertiary Stereogenic Carbon Formation, Scope, and Origin of Enantioselectivity

Catalytic Asymmetric α-Functionalization of α-Branched Aldehydes

Aldehydes constitute a main class of organic compounds widely applied in synthesis. As such, catalyst-controlled enantioselective α-functionalization of aldehydes has attracted great interest over the years. In this context, α-branched aldehydes are especially challenging substrates because of reactivity and selectivity issues. Firstly, the transient trisubstituted enamines and enolates resulting upon treatment with an aminocatalyst or a base, respectively, would exhibit attenuated reactivity; secondly, mixtures of E- and Z-configured enamines/enolates may be formed; and third, effective face-discrimination on such trisubstituted sp2 carbon intermediates by the incoming electrophilic reagent is not trivial. Despite these issues, in the last 15 years, several catalytic approaches for the α-functionalization of prostereogenic α-branched aldehydes that proceed in useful yields and diastereo- and enantioselectivity have been uncovered. Developments include both organocatalytic and metal-catalyzed approaches as well as dual catalysis strategies for forging new carbon–carbon and carbon–heteroatom (C-O, N, S, F, Cl, Br, …) bond formation at Cα of the starting aldehyde. In this review, some key early contributions to the field are presented, but focus is on the most recent methods, mainly covering the literature from year 2014 onward.

Exploration of Succinimide Derivative as a Multi-Target, Anti-Diabetic Agent: In Vitro and In Vivo Approaches

Diabetes mellitus (DM) is counted among one of the leading challenges in the recent era, and it is a life-threatening disorder. Compound 4-hydroxy 3-methoxy phenylacetone (compound 1) was previously isolated from Polygonum aviculare. This compound was reacted with N-benzylmaleimide to synthesize the targeted compound 3. The purpose of this research is to exhibit our developed compound 3's ability to concurrently inhibit many targets that are responsible for hyperglycemia. Compound 3 was capable of inhibiting α-amylase, α-glucosidase, and protein tyrosine phosphatase 1 B. Even so, outstanding in vitro inhibition was shown by the compound against dipeptidyl peptidase-4 (DPP-4) with an IC₅₀ value of 0.07 µM. Additionally, by using DPPH in the antioxidant activity, it exhibited good antioxidant potential. Similarly, in the in vivo activity, the experimental mice proved to be safe by treatment with compound 3. After 21 days of examination, the compound 3 activity pattern was found to be effective in experimental mice. Compound 3 decreased the excess peak of total triglycerides, total cholesterol, AST, ALT, ALP, LDL, BUN, and creatinine in the STZ-induced diabetic mice. Likewise, the histopathology of the kidneys, liver, and pancreas of the treated animals was also evaluated. Overall, the succinimde moiety, such as compound 3, can affect several targets simultaneously, and, finally, we were successful in synthesizing a multi-targeted preclinical therapy.

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.

Asymmetric Conjugate Addition of Ketones to Maleimides Organocatalyzed by a Chiral Primary Amine-Salicylamide

Enantioenriched substituted succinimides are interesting compounds, and their asymmetric organocatalytic synthesis by the conjugated addition of ketones to maleimides has been scarcely explored. This study shows the enantioselective conjugate addition of ketones to maleimides organocatalyzed by a simple primary amine-salicylamide derived from a chiral trans-cyclohexane-1,2-diamine, which provides the desired succinimides in good to excellent yields (up to 98%) and with moderate to excellent enantioselectivities (up to 99%).

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.

β-Amino Acid Organocatalysts in the Asymmetric Michael Addition of Isobutyraldehyde to N-Substituted Maleimides

Asymmetric Michael additions of carbonyl compounds to N-substituted maleimides are among the most convenient reactions to prepare optically pure succinimide building blocks. Although a few β-amino acids were found to be highly efficient organocatalysts in the addition of α-branched aldehydes, the effect of their structure on the results of these reactions has not yet been investigated. In the present study, we disclose several unexpected and interesting structural effects of aliphatic and cycloaliphatic β-amino acids obtained in the enantioselective conjugate addition of isobutyraldehyde to N-benzylmaleimide. The dependence of the sense of the enantioselectivity on the bulkiness of the substituent on the β-carbon atom, the beneficial spatial arrangements of the functional groups in cis isomers with cyclohexane scaffold and the inversion of the enantioselectivity depending on the absence of a base additive observed with some trans isomers are unprecedented findings. The minor influence of the nitrogen substituent of the maleimide ring on both the reaction rate and the enantioselectivity was also evidenced using alicyclic β-amino acid prepared from an easily available terpene derivative.

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.

Comparative in-vitro anti-inflammatory, anticholinesterase and antidiabetic evaluation: computational and kinetic assessment of succinimides cyano-acetate derivatives

This research was planned to synthesize cyano-acetate derivatives of succinimide and evaluate its comparative biological efficacy as anti-inflammatory, anti-cholinesterase and anti-diabetic, which was further validated by molecular docking studies. The three cyano-acetate derivatives of succinimide including compound 23 Methyl 2-cyano-2-(2,5-dioxopyrrolidin-3-yl)acetate, compound 31 Methyl 2-cyano-2-(1-methyl-2,5-dioxopyrrolidin-3-yl)acetate and compound 44 Methyl 2-cyano-2-(1-ethyl-2,5-dioxopyrrolidin-3-yl) acetate were synthesized. The mentioned compounds were checked for in vitro anti-inflammatory, anti-cholinesterase and anti-diabetic (α-amylase inhibition) activity. To validate the in vitro results, computational studies were carried out using molecular operating environment to analyse the BE, i.e. binding energies of all synthesized compounds against the respective enzymes. The Compounds 23, 31, 44 exhibited anti-inflammatory via inhibiting COX-2 (IC50 value of 204.08, 68.60 and 50.93 µM, respectively), COX-1 (IC50 value of 287, 185, and 143 µM, respectively) and 5-LOX (IC50 value of 138, 50.76 and 20, 87 µM respectively). They exhibited choline-mimetic potential, such as compound 23, 31 and 44 inhibited AChE enzyme (IC50 value of 240, 174, and 134 µM, respectively) and BChE enzyme (IC50 value of 203, 134 and 97 µM, respectively). The Compounds 23, 31, 44 exhibited anti-diabetic effect via inhibiting α-amylase enzyme (IC50 values of 250, 106 and 60 µM, respectively). Molecular docking studies revealed that the synthesized compounds have good binding affinity in the binding pockets of AChE, BChE, COX-2, 5-LOX and α-amylase enzyme and showed high binding energies. The synthesized succinimide derivatives, i.e. compound 23, 31, 44 showed marked inhibitory activities against cyclooxygenase, lipoxygenase, α-amylase and cholinesterase enzymes. Among these three, compound 44 and 31 showed strong anti-inflammatory and anti-diabetic activity while they displayed moderate anti-cholinesterase activity supported by molecular docking results.Communicated by Ramaswamy H. Sarma.

Enantioselective Organocatalyzed Michael Addition of Isobutyraldehyde to Maleimides in Aqueous Media

Thiourea was introduced into (R,R)-1,2-diphenylethylenediamine as an organocatalyst to promote the reaction between isobutyraldehydes and maleimides. Enantioselective Michael addition reaction was carried out as an eco-friendly method using water as the solvent. As a result of the reaction between isobutyraldehyde and maleimide, ≥97% yield and 99% enantioselectivity were obtained at a low catalyst loading of 0.01 mol%. The solvent effect can be explained by theoretical calculations that indicate the participation of a transition state, in which the CF₃ substituent of the catalyst is a hydrogen bond activated by the surrounding water molecules. This discovery enabled the use of low catalyst loading in the organic reactions of chiral substances for pharmaceutical applications. Furthermore, a solvent effect for Michael reaction of the organocatalysts was proposed, and the organic reaction mechanisms were determined through quantum calculations.

Enantioselective Michael addition of aldehydes to maleimides catalysed by surface-adsorbed natural amino acids

Chiral hybrid materials obtained by adsorption of primary α-amino acids on the surface of inorganic oxides are economic, recyclable, highly enantioselective heterogeneous catalysts for the Michael addition of aldehydes to N-substituted maleimides.

Bioactive stigmastadienone from Isodon rugosus as potential anticholinesterase, α-glucosidase and COX/LOX inhibitor: In-vitro and molecular docking studies

Natural product is a well-known source of bioactive compounds. Herein, a steroidal compound stigmasta-7,22-diene-3-one (stigmastadienone) has been isolated from Isodon rugosus. The potency of isolated compound has been tested for several in-vitro targets. The acetyl and butyrylcholinesterase assays were performed using Ellman's procedure. For the in-vitro antidiabetic potential, α-glucosidase inhibitory assay was performed. Similarly, the cyclo and lipoxygenase pathways were studied to find its potential role in the management of inflammation and analgesia. The 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and hydrogen peroxide (H₂O₂) assays were performed for the antioxidant potentials. Docking studies were performed against acetylcholinesterase, cyclooxygenase and lipoxygenase targets. In anticholinesterase assays, stigmastadienone exhibited half-maximal inhibitory concentration (IC₅₀) values of 13.52 and 11.53 μg/ml for acetyl and butyrylcholinesterase respectively. The observed IC₅₀ values for that of galantamine were 6.07 and 4.42 μg/ml for acety and butyrylcholinesterase respectively. In inhibiting α-glucosidase enzyme, the compound showed mediocre IC₅₀ of 109.40 μg/ml compared to the standard acarbose (7.60 μg/ml). The stigmastadienone proved to be an excellent inhibitor of cyclooxygenase 2 (COX-2) and 5-lipoxygenase (5-LOX) attaining IC₅₀ values of 4.72 and 3.36 μg/ml respectively. The standard drugs IC₅₀ values for COX-2 (celecoxib) and 5-LOX (montelukast) were 3.81 and 2.74 μg/ml respectively. The enzymatic activities of stigmastadienone were also supplemented with antioxidant results, specifically it was more dominant against DPPH and ABTS free radicals. Docking studies showed that only the carbonyl oxygen is able to form hydrogen bond interaction with the residues. In conclusions, the stigmastadienone has been isolated from Isodon rugosus for the first time. Moreover, the compound has been evaluated for several biochemical pathways which suggest its pharmacological role on the explored targets.

Tailoring the substitution pattern of Pyrrolidine-2,5-dione for discovery of new structural template for dual COX/LOX inhibition

Dual inhibition of the enzymatic pathways of cyclooxygenases (COX-1/COX-2) and lipoxygenase (LOX) is a rational approach for developing more efficient and safe anti-inflammatory agents. Herein, dual inhibitors of COX and LOX for the management of inflammation are reported. The structural modifications of starting pyrrolidine-2,5-dione aldehyde derivatives resulted in two structurally diverse families (Family A & B). Synthesized derivatives from both Families displayed preferential COX-2 affinity in submicromolar to nanomolar ranges. Disubstitution pattern of the most active series of compounds having N-(benzyl(4-methoxyphenyl)amino moiety presents a new template that is mimic to the diaryl pattern of traditional COX-2 inhibitors. Compound 78 with IC₅₀ value of 0.051 ± 0.001 μM emerged as the most active compound. Highly potent COX-2/5-LOX inhibitors have also demonstrated appreciable in-vivo anti-inflammatory activity through carrageenan induced paw edema test. Moreover, the involvement of histamine, bradykinin, prostaglandin, and leukotriene mediators to adjust the inflammatory response were also studied. Apart from COX inhibition, sulfonamide is considered an important template for carbonic anhydrase inhibition. Hence, we also evaluated six sulfonamide derivatives for off-target in-vitro bovine carbonic anhydrase-II inhibition. Biological results were finally rationalized by docking simulations. Typically, most active COX-2 inhibitors interact with the amino acid residues responsible for the COX-2 selectivity.

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.

Recent advances in reactions promoted by amino acids and oligopeptides

During the last 20 years, Organocatalysis has become one of the major fields of Catalysis. Herein, we provide a recent overview on reactions where the use of amino acids and peptides as the organocatalysts was employed. All aspects regarding aldol reactions, Michael reactions, epoxidation, Henry reactions and many others that are crucial for the reaction conditions and reaction mechanisms are discussed.

Straightforward access to densely substituted chiral succinimides through enantioselective organocatalyzed Michael addition of α-alkyl-cyclic ketones to maleimides

A simple, cheap and unchanged organocatalytic system provides efficient access to densely substituted chiral succinimides bearing QCC–TCC vicinal stereocenters from unreactive α-alkyl cyclic ketones and maleimides.

N-Primary-amine tetrapeptide-catalyzed highly asymmetric Michael addition of aliphatic aldehydes to maleimides

The highly asymmetric Michael addition reaction between maleimides and aldehydes catalyzed by N-primary-amine β-turn tetrapeptides with excellent yields and enantioselectivities was reported.

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.

Regio- and Stereoselective Synthesis of Fully Substituted Silyl Enol Ethers of Ketones and Aldehydes in Acyclic Systems

The regio- and stereoselective preparation of fully substituted and stereodefined silyl enol ethers of ketones and aldehydes through an allyl-Brook rearrangement is reported. This fast and efficient method proceeds from a mixture of E and Z isomers of easily accessible starting materials.

Enantioselective Michael Addition of Aldehydes to Maleimides Organocatalyzed by a Chiral Primary Amine-Salicylamide

A primary amine-salicylamide derived from chiral trans-cyclohexane-1,2-diamine was used as an organocatalyst for the enantioselective conjugate addition of aldehydes, mainly α,α-disubstituted to N-substituted maleimides. The reaction was performed in toluene as a solvent at room temperature. The corresponding enantioenriched adducts were obtained with high yields and enantioselectivities up to 94%. Theoretical calculations were used to justify the stereoinduction.

Synthesis of α-alkylated γ-butyrolactones with concomitant anhydride kinetic resolution using a sulfamide-based catalyst

The Kinetic Resolution (KR) of α-alkylated enolisable disubstituted anhydrides has been shown to be possible for the first time. In the presence of an ad hoc designed novel class of bifunctional sulfamide organocatalyst, a regio-, diastereo- and enantioselective cycloaddition reaction between the enolisable anhydride and benzaldehydes provides densely functionalised γ-butyrolactones in one pot (up to 19 : 1 dr, 94% ee) with control over three contiguous stereocentres. The concomitant resolution of the starting material anhydride, provides access to a range of chiral succinate derivatives with selectivity factors up to S* = 10.5.

Acetophenone Mannich bases: study of ionic liquid catalysed synthesis and antioxidative potential of products

Three-component Mannich reaction of acetophenone or 4-iodoacetophenone with a variety of substituted anilines and benzaldehyde, catalysed with diethanolammonium chloroacetate, was performed under mild conditions. Mannich bases (MBs), of which five are new, were obtained in good to excellent yields. All compounds were characterized using elemental analysis, NMR and IR. In addition, detailed experimental and simulated UV-Vis spectral characterization of these compounds is presented here for the first time. In vitro antioxidative potential of synthetized MBs was evaluated using 2,2-diphenyl-1-picryl-hydrazyl radical and density functional theory (DFT) thermodynamical study. It was shown that compounds with anisidine moiety express moderate antioxidative activity. Mechanism of the organocatalysed Mannich reaction was thoroughly inspected by means of DFT. The reaction undergoes the hydrogen bonding-assisted mechanism. Moreover, the proposed rate determining step of the overall reaction is water elimination in the process of iminium ion formation. To the extent of our knowledge, this is the first detailed report on the influence of this type of catalyst on the formation of iminium ion, as a crucial intermediate for the whole reaction.

Combining organocatalysis with photoorganocatalysis: photocatalytic hydroacylation of asymmetric organocatalytic Michael addition products

Organocatalysis and photoorganocatalysis are two areas of synthetic methodology that have been successfully combined.

Ethyl 3-oxo-2-(2,5-dioxopyrrolidin-3-yl)butanoate Derivatives: Anthelmintic and Cytotoxic Potentials, Antimicrobial, and Docking Studies

Development of multidrug resistance (MDR) to antimicrobial, antiparasitic and chemotherapeutic agents is a global challenge for the scientific community. Despite of the emergence of MDR pathogens, the development of novel and more effective drugs is slow and scientist even speculate that we are going back the pre-antibiotic era. This work aims to study and evaluate the preliminary antibacterial, anthelmintic and cytotoxic potentials of ethyl 3-oxo-2-(2,5-dioxopyrrolidin-3-yl)butanoates. Among all of the four compounds, compound 2 has displayed remarkable potency with MIC values of 0.125, 0.083, 0.073, and 0.109 mg/ml against E. sakazakii, E. coli. S. aureus, and K. pneumonia, respectively. Compared to etoposide (LC50 9.8 μg/ml), the compounds demonstrated LC50 values from 280 to 765 μg/ml. For anthelmintic assay, three concentrations of each compound and standard drug were studied in determination of time of death of the two species. Excellent anthelmintic activity was observed by all four compounds against P. posthuma and A. galli better than standard albendazole. High GOLD fitness score data from docking analysis toward the targets represent better protein-ligand binding affinity and thus indicate a high propensity for all the active compounds to bind to the active site. The promising in-vitro antimicrobial, anthelmintic activity, and cytotoxicity data conclusively revealed that these compounds may serve as viable lead compounds for the treatment of bacterial and parasitic infections, and therefore, could help the medicinal chemists to design future chemotherapeutic agents to avoid rapid drug resistance.

Asymmetric Michael Addition Organocatalyzed by α,β-Dipeptides under Solvent-Free Reaction Conditions

The application of six novel α,β-dipeptides as chiral organocatalysts in the asymmetric Michael addition reaction between enolizable aldehydes and N-arylmaleimides or nitroolefins is described. With N-arylmaleimides as substrates, the best results were achieved with dipeptide 2 as a catalyst in the presence of aq. NaOH. Whereas dipeptides 4 and 6 in conjunction with 4-dimethylaminopyridine (DMAP) and thiourea as a hydrogen bond donor proved to be highly efficient organocatalytic systems in the enantioselective reaction between isobutyraldehyde and various nitroolefins.

Phospha-Michael addition reaction of maleimides employing N-heterocyclic phosphine-thiourea as a phosphonylation reagent: synthesis of 1-aryl-2,5-dioxopyrrolidine-3-yl-phosphonate derivatives

The phospha-Michael addition reaction of maleimides with NHP-thiourea under catalyst and additive free conditions has been developed for desymmetrization of maleimides.

Asymmetric dual catalysis via fragmentation of a single rhodium precursor complex

A strategy for dual transition metal catalysis and organocatalysis is reported via disintegration of a single rhodium complex. Conveniently, the chiral-at-metal rhodium precatalyst can be synthesized in just two steps starting from rhodium trichloride without the need for any chromatography.

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

Preparation of conformationally restricted β(2,2)- and β(2,2,3)-amino esters and derivatives containing an all-carbon quaternary center

β-Amino acids are routinely incorporated into peptidic drugs to increase their stability and to incur conformational biases. However, the synthesis of highly substituted β-amino acids still represents a great challenge. A new approach to their preparation is reported involving a Vilsmeier-Haack reaction with nonaromatic carbon nucleophiles. The highly challenging preparation of contiguous tertiary and all-carbon quaternary centers was successfully used to generate several β(2,2,3)-amino esters, such as derivatives of homoproline, homoalanine, and homopipecolinic esters.