Piperidine Derivatives: Recent Advances in Synthesis and Pharmacological Applications

Alkaloids solenopsins from fire ants display in vitro and in vivo activity against the yeast Candida auris

The urgency surrounding Candida auris as a public health threat is highlighted by both the Center for Disease Control (CDC) and World Health Organization (WHO) that categorized this species as a priority fungal pathogen. Given the current limitations of antifungal therapy for C. auris, particularly due to its multiple resistance to the current antifungals, the identification of new drugs is of paramount importance. Some alkaloids abundant in the venom of the red invasive fire ant (Solenopsis invicta), known as solenopsins, have garnered attention as potent inhibitors of bacterial biofilms, and there are no studies demonstrating such effects against fungal pathogens. Thus, we herein investigated the antibiotic efficacy of solenopsin alkaloids against C. auris biofilms and planktonic cells. Both natural and synthetic solenopsins inhibited the growth of C. auris strains from different clades, including fluconazole and amphotericin B-resistant isolates. Such alkaloids also inhibited matrix deposition and altered cellular metabolic activity of C. auris in biofilm conditions. Mechanistically, the alkaloids compromised membrane integrity as measured by propidium iodide uptake in exposed planktonic cells. Additionally, combining the alkaloids with AMB yielded an additive antifungal effect, even against AMB-resistant strains. Finally, both extracted solenopsins and the synthetic analogues demonstrated protective effect in vivo against C. auris infection in the invertebrate model Galleria mellonella. These findings underscore the potent antifungal activities of solenopsins against C. auris and suggest their inclusion in future drug development. Furthermore, exploring derivatives of solenopsins could reveal novel compounds with therapeutic promise.

Updated pharmaceutical progress on plant antibiotic rhein and its analogs: Bioactivities, structure-activity relationships and future perspectives

Rhein, as a plant antibiotic, demonstrates a broad spectrum of pharmacological effects. Nevertheless, its limited water solubility, low bioavailability, and potential hepatotoxicity and nephrotoxicity making it difficult to directly become a medicine, thereby imposing significant constraints on its clinical application. In recent decades, extensive researches have been proceeded on the multifaceted structural modifications of rhein, resulting in notable improvements on pharmacological activities and druggabilities. This review offers a comprehensive overview and advanced update on the biological potential and structural-activity relationships (SARs) of various rhein derivatives, delineating the sites of structural modification and corresponding activity trends of rhein derivatives for future.

Analysis of cassine and spectaline in the Senna spectabilis ethanolic extracts by capillary zone electrophoresis with indirect UV detection

INTRODUCTION

2,6-Disubstituted piperidin-3-ols are an important group of piperidine alkaloids found in species such as Senna spectabilis, whose main constituents include cassine and spectaline, compounds with relevant pharmacological activity. The analysis of these compounds is challenging due to the complexity of plant extracts and the absence of chromophores capable of absorbing ultraviolet (UV) radiation.

OBJECTIVE

This paper presents a new analytical method to separate and quantify the non-UV-absorbing alkaloids present in ethanol extracts from S. spectabilis flowers using capillary zone electrophoresis (CZE) with indirect UV detection.

METHODOLOGY

The optimized CZE method employs a background electrolyte containing 60 mM histidine (His), 15 mM α-cyclodextrin, 20% acetonitrile (ACN), and pH-adjusted to 4.7 with acetic acid (AcOH).

RESULTS

The limit of detection (LOD) values was 10.2 and 13.9 mg L-1 for cassine and spectaline, respectively. For both analytes, the precision data were better than 2% of relative standard deviation (RSD) for migration times and peak areas. To evaluate the applicability of the developed method, ethanolic extracts from S. spectabilis flowers were prepared and analyzed.

CONCLUSIONS

Thereby, the method proved to be efficient and complementary to conventional techniques, offering a cost-effective alternative in the quantification of the non-UV-absorbing piperidine alkaloids present in plant extracts.

Design, synthesis, in vitro and in silico studies of novel piperidine derived thiosemicarbazones as inhibitors of dihydrofolate reductase

Dihydrofolate reductase (DHFR), an essential enzyme in folate metabolism, presents a promising target for drug development against various diseases, including cancer and tuberculosis. Herein, we present an integrated approach combining in vitro biochemical assays with in silico molecular docking analysis to evaluate the inhibitory potential of 4-piperidine-based thiosemicarbazones 5(a-s) against DHFR. In our in vitro study, a novel series of 4-piperidine-based thiosemicarbazones 5(a-s) were assessed for their inhibitory activity against DHFR enzyme. The synthesized compounds 5(a-s) exhibited potent inhibition with IC50 values in the range of 13.70 ± 0.25 µM to 47.30 ± 0.86 µM. Among all the derivatives 5p displayed highest inhibitory activity. Simultaneously, in silico analysis were performed and compared with standard drug (Methotrexate) to predict the binding affinity and interaction pattern of synthesized compounds with DHFR active site. SAR analysis was done to elucidate how structural modifications impact compound's biological activity, guiding the rational design of potent and selective drug candidates for targeted diseases. These findings may provide a comprehensive assessment of 4-piperdine-based thiosemicarbazones as DHFR inhibitors and contribute to the development of novel therapeutics targeting DHFR-associated diseases.

Revisiting the Reaction of Sulfur Ylides with Acetylenic Esters: Synthesis of Trisubstituted 1,3-Dienes, α-Carbonyl Vinyl Sulfoxides and α-Carbonyl Vinyl Sulfoxonium Ylides

We report herein a reexamination of the reactions between sulfoxonium ylides and acetylenic esters. Continuing our previous study of conjugate additions using α-carbonyl sulfoxonium ylides, we came across an interesting transformation when dimethyl acetylenedicarboxylate (DMAD) was employed as a Michael acceptor. Trisubstituted electron-deficient 1,3-dienes and α-carbonyl vinyl sulfoxides were obtained for the first time from these sulfur ylides, in a stereoselective manner (exclusively forming the E-isomer), achieving yields of up to 70 % and 83 %, respectively. Selected dienes were subsequently utilized in the synthesis of novel nitrogen heterocycles. Interestingly, when di-tert-butyl acetylenedicarboxylate (DtBAD) or alkyl propiolates were evaluated, the isolated product arose from the classical Michael addition, yielding α-carbonyl vinyl sulfoxonium ylides in yields of up to 89 %.

Stereocontrolled and time-honored access to piperidine- and pyrrolidine-fused 3-methylenetetrahydropyrans using lactam-tethered alkenols

Polycyclic oxygen-heterocycles bearing the 3-methylenetetrahydropyran (i.e., 3-MeTHP) motif are resident in bioactive molecules such as hodgsonox and iridoid. Meanwhile, the δ- and γ-lactam topologies as well as their reduced variants (i.e., piperidines and pyrrolidines) are at the core of several pharmaceuticals and fragrances. A stereocontrolled, time-honored, and cost-effective strategy that merges a 3-MeTHP motif with the aforementioned azaheterocyclic scaffolds could exponentially expand the 3D-structural space for the discovery of new small molecules with medicinal value. In these studies, readily affordable lactam-tethered alkenols have been interrogated in two complementary cascade approaches, leading to the regioselective and stereocontrolled synthesis of lactam-fused 3-MeTHPs. The first approach hinges on regioselective 6-endo-trig bromoetherification of the alkenols and concomitant elimination to arrive at the desired 3-MeTHPs. The methylene portion of the 3-MeTHP is unveiled at a late stage, which is noteworthy since all existing approaches to 3-MeTHPs rely on early-stage introduction of the methylene group. The second strategy involves transition metal-catalyzed alkoxylation of the tethered alkenol followed by base-induced double bond isomerization. The lactam-fused 3-MeTHPs are obtained in high site- and diastereo-selectivities. Post-modification of the bicycles has led to the construction of 3-MeTHP-fused saturated piperidines and pyrrolidines as well as 3-MeTHPs bearing four contiguous stereocenters.

Synthesis and molecular structure exploration of novel piperidin-4-one imine derivatives combined with DFT and X-ray: A new class of antioxidant and anti-inflammatory agents

Inflammation is one of the pertinent responses of the body, depending mainly on the process and factors involved in combating the oxidative species produced either by any infection or failure of the antioxidant pathways. In search of new compounds to exhibit antioxidant and anti-inflammatory activity here, we have successfully reported the synthesis of three novel compounds of Piperidin-4-one skeleton by adopting simple and convenient methods. Compound 1, (3, 3-dimethyl-2, 6-bis(3,4,5-trimethoxyphenyl) piperidin-4-one) was synthesized by one-pot Mannich condensation reaction having good yield (88 %). Furthermore in the next step highly functionalized imine derivatives, Compound 2 (3,3-dimethyl-2,6-bis (3,4,5-trimethoxyphenyl) piperidine-4-one) hydrazine carbothioamide) and Compound 3 (3,3-dimethyl-2,6-bis(3,4,5-trimethoxyphenyl) piperidin-4-one oxime) were prepared by the condensation reaction with thiosemicarbazide and hydroxylamine hydrochloride with compound 1, respectively. The structure of the compounds has been deduced by the combined use of modern spectroscopic and single crystal x-ray diffraction (XRD) techniques. in-silico ADMET studies predict pharmacokinetic properties and showed that compounds are non toxic on vital organs. The optimized geometry and reactivity parameters of compounds were further calculated based on the B3LYP/6-31G (d, p) density functional theory (DFT). The negative values of chemical potential follow the trend as 2 (-0.2101) > 3 (-0.2198) > 1(-0.2233) signifies that all compounds are reactive in nature as evident from in-vitro antioxidant and anti-inflammatory response were determined by using the DDPH assay and protein denaturation methods respectively. Compounds possess good radical scavenging activity having IC 50 values 30.392 μM (2), 37.802 (1) μM, and 72.285 (3) μM, and anti-inflammatory response in same manner indicating that 2 (71.3 %) is more active than compound 1 (43.5 %) and 3 (39.3 %) marking them as a potential antioxidant and anti-inflammatory agents.

Exploring fluorine-substituted piperidines as potential therapeutics for diabetes mellitus and Alzheimer's diseases

In the current study, a series of fluorine-substituted piperidine derivatives (1-8) has been synthesized and characterized by various spectroscopic techniques. In vitro and in vivo enzyme inhibitory studies were conducted to elucidate the efficacy of these compounds, shedding light on their potential therapeutic applications. To the best of our knowledge, for the first time, these heterocyclic structures have been investigated against α-glucosidase and cholinesterase enzymes. The antioxidant activity of the synthesized compounds was also assessed. Evaluation of synthesized compounds revealed notable inhibitory effects on α-glucosidase and cholinesterases. Remarkably, the target compounds (1-8) exhibited extraordinary α-glucosidase inhibitory activity as compared to the standard acarbose by several-fold. Subsequently, the potential antidiabetic effects of compounds 2, 4, 5, and 6 were validated using a STZ-induced diabetic rat model. Kinetic studies were also performed to understand the mechanism of inhibition, while structure-activity relationship analyses provided valuable insights into the structural features governing enzyme inhibition. Kinetic investigations revealed that compound 4 displayed a competitive mode of inhibition against α-glucosidase, whereas compound 2 demonstrated mixed-type behavior against AChE. To delve deeper into the binding interactions between the synthesized compounds and their respective enzyme targets, molecular docking studies were conducted. Overall, our findings highlight the promising potential of these densely substituted piperidines as multifunctional agents for the treatment of diseases associated with dysregulated glucose metabolism and cholinergic dysfunction.

Harnessing the power of natural alkaloids: the emergent role in epilepsy therapy

The quest for effective epilepsy treatments has spotlighted natural alkaloids due to their broad neuropharmacological effects. This review provides a comprehensive analysis of the antiseizure properties of various natural compounds, with an emphasis on their mechanisms of action and potential therapeutic benefits. Our findings reveal that bioactive substances such as indole, quinoline, terpenoid, and pyridine alkaloids confer medicinal benefits by modulating synaptic interactions, restoring neuronal balance, and mitigating neuroinflammation-key factors in managing epileptic seizures. Notably, these compounds enhance GABAergic neurotransmission, diminish excitatory glutamatergic activities, particularly at NMDA receptors, and suppress proinflammatory pathways. A significant focus is placed on the strategic use of nanoparticle delivery systems to improve the solubility, stability, and bioavailability of these alkaloids, which helps overcome the challenges associated with crossing the blood-brain barrier (BBB). The review concludes with a prospective outlook on integrating these bioactive substances into epilepsy treatment regimes, advocating for extensive research to confirm their efficacy and safety. Advancing the bioavailability of alkaloids and rigorously assessing their toxicological profiles are essential to fully leverage the therapeutic potential of these compounds in clinical settings.

Design, Synthesis, and Antibacterial Evaluation of Novel Isoindolin-1-ones Derivatives Containing Piperidine Fragments

A series of novel isoindoline-1-one derivatives containing piperidine moiety were designed and synthesized using natural compounds as raw materials, and their biological activities were tested for three bacterial and three fungal pathogens. These derivatives exhibited good against phytopathogenic bacteria activities against Pseudomonas syringae pv actinidiae (Psa) and Xanthomonas axonopodis pv.citri (Xac). Some compounds exhibited excellent antibacterial activities against Xanthomonas oryzae pv oryzae (Xoo). The dose of Y8 against Xoo (the maximum half lethal effective concentration (EC50) = 21.3 μg/mL) was better than that of the thiediazole copper dose (EC50 = 53.3 μg/mL). Excitingly, further studies have shown that the molecular docking of Y8 with 2FBW indicates that it can fully locate the interior of the binding pocket through hydrogen bonding and hydrophobic interactions, thereby enhancing its anti-Xoo activity. Scanning electron microscopy (SEM) studies revealed that Y8 induced the Xoo cell membrane collapse. Moreover, the proteomic results also indicate that Y8 may be a multifunctional candidate as it affects the formation of bacterial Xoo biofilms, thereby exerting antibacterial effects.

Stereoselective synthesis of gem-dihalopiperidines via the halo-aza-Prins cyclization reaction: access to piperidin-4-ones and pyridines

An efficient methodology for the synthesis of 4,4-dihalopiperidine derivatives in excellent yields has been developed using N-(3-halobut-3-en-1-yl)-4-methylbenzenesulfonamide and an aldehyde catalyzed by In(OTf)3. The reaction involves an initial formation of a six-membered carbocation via the aza-Prins cyclization reaction followed by a nucleophilic attack by a halide ion to give 4,4-dihalopiperidine. The dihalopiperidine is converted to tetrahydropiperidinone using Ac2O/Et3N in DCM/H2O (1 : 1). It is also utilized for the synthesis of pyridine scaffolds by treatment with DBU. Furthermore, the dihalopiperidine is transformed to its enol ether derivatives using KOH in alcohol.

Multimodal Acridine Photocatalysis Enables Direct Access to Thiols from Carboxylic Acids and Elemental Sulfur

Development of photocatalytic systems that facilitate mechanistically divergent steps in complex catalytic manifolds by distinct activation modes can enable previously inaccessible synthetic transformations. However, multimodal photocatalytic systems remain understudied, impeding their implementation in catalytic methodology. We report herein a photocatalytic access to thiols that directly merges the structural diversity of carboxylic acids with the ready availability of elemental sulfur without substrate preactivation. The photocatalytic transformation provides a direct radical-mediated segue to one of the most biologically important and synthetically versatile organosulfur functionalities, whose synthetic accessibility remains largely dominated by two-electron-mediated processes based on toxic and uneconomical reagents and precursors. The two-phase radical process is facilitated by a multimodal catalytic reactivity of acridine photocatalysis that enables both the singlet excited state PCET-mediated decarboxylative carbon-sulfur bond formation and the previously unknown radical reductive disulfur bond cleavage by a photoinduced HAT process in the silane-triplet acridine system. The study points to a significant potential of multimodal photocatalytic systems in providing unexplored directions to previously inaccessible transformations.

Hydrogen bonding-promoted tunable approach for access to aza-bicyclo-[3.3.0]octanes and cyclopenta[b] pyrroles

A unified strategy is disclosed that builds on successfully engaging the aniline nitrogen of 1,3-amphoteric γ-aminocyclopentenone for a tandem annulation with electron-poor alkynes, solely assisted by the H-bonding network of HFIP. This metal-free mild strategy provides access to medicinally relevant aza-bicyclo-octanes en route to another important scaffold: cyclopenta[b]pyrrole.

Identification of avaC from Human Gut Microbial Isolates that Converts 5AVA to 2-Piperidone

2-piperidone is a crucial industrial raw material of high-value nylon-5 and nylon-6,5. Currently, a major bottleneck in the biosynthesis of 2-piperidone is the identification of highly efficient 2-piperidone synthases. In this study, we aimed to identify specific strains among 51 human gut bacterial strains capable of producing 2-piperidone and to elucidate its synthetic mechanism. Our findings revealed that four gut bacterial strains, namely Collinsella aerofaciens LFYP39, Collinsella intestinalis LFYP54, Clostridium bolteae LFYP116, and Clostridium hathewayi LFYP18, could produce 2-piperidone from 5-aminovaleric acid (5AVA). Additionally, we observed that 2-piperidone could be synthesized from proline through cross-feeding between Clostridium difficile LFYP43 and one of the four 2-piperidone producing strains, respectively. To identify the enzyme responsible for catalyzing the conversion of 5AVA to 2-piperidone, we utilized a gain-of-function library and identified avaC (5-aminovaleric acid cyclase) in C. intestinalis LFYP54. Moreover, homologous genes of avaC were validated in the other three bacterial strains. Notably, avaC were found to be widely distributed among environmental bacteria. Overall, our research delineated the gut bacterial strains and genes involved in 2-piperidone production, holding promise for enhancing the efficiency of industrial biosynthesis of this compound.

Halimane Derivatives from Plectranthus ornatus Codd. as Novel Anti-cancer Agents

The Plectranthus genus is often cited for its medicinal properties. Plectranthus ornatus Codd. is traditionally used in Africa for the treatment of gastric and liver diseases and their leaves are used for their antibiotic action. The main constituent of P. ornatus is the halimane compound, 11 R∗-acetoxyhalima-5,13E-dien-15-oic acid (Hal), described for its antimicrobial and anticancer properties. The objective of this work was to improve the activity of the halimane lead molecule. Further physiochemical characterisation was performed on Hal. To the best of our knowledge, this work constitutes the first published data of the absolute configurations by SCXRD and thermal stability of Hal. Using Hal, reactions with different amines were carried out to afford novel semi-synthetic derivatives and their structural elucidation was completed. The cytotoxicity of the derivatives was assessed against three leukaemia cancer cell lines (CCRF-CEM, K562 and HL-60). The antioxidant activity was investigated using H2O2-induced HGF-1 cells and their anti-inflammatory activity was studied using RT-PCR and ELISA. Our data showed that amide derivatives of Hal presented moderate cytotoxicity and more potent activity when compared to the parent molecule, giving insight into the SAR of Hal. The derivatives also displayed protection against oxidative damage to DNA. Finally, the derivatives possessed anti-inflammatory properties at the level of gene and protein expression for the cytokines IL-1β, TNF-α and IL-6, induced by LPS in normal HGF-1 cells. Overall, our study provides useful insight into the enhanced biological activities of semi-synthetic Hal derivatives, as a starting point for novel drug formulations in cancer therapy.

Development in the Synthesis of Bioactive Thiazole-Based Heterocyclic Hybrids Utilizing Phenacyl Bromide

Heterocyclic hybrid frameworks represent a burgeoning domain within the realms of drug discovery and medicinal chemistry, attracting considerable attention in recent years. Thiazole pharmacophore fragments, inherent in natural products such as peptide alkaloids, metabolites, and cyclopeptides, have demonstrated a broad spectrum of pharmacological potentials. Given their profound biological significance, a plethora of thiazole-based hybrids have been synthesized through the conjugation of thiazole moieties with bioactive pyrazole and pyrazoline fragments. This review systematically presents a compendium of robust methodologies for the synthesis of thiazole-linked hybrids, employing the (3 + 2) heterocyclization reaction, specifically the Hantzsch-thiazole synthesis, utilizing phenacyl bromide as the substrate. The strategic approach of molecular hybridization has markedly enhanced drug efficacy, mitigated resistance to multiple drugs, and minimized toxicity concerns. The resultant thiazole-linked hybrids exhibit a myriad of medicinal properties viz. anticancer, antibacterial, anticonvulsant, antifungal, antiviral, and antioxidant activities. This compilation of methodologies and insights serves as a valuable resource for medicinal chemists and researchers engaged in the design of novel thiazole-linked hybrids endowed with therapeutic attribute.

Cyclic Amine Synthesis via Catalytic Radical-Polar Crossover Cycloadditions

The rapid assembly of valuable cyclic amine architectures in a single step from simple precursors has been recognized as an ideal platform in term of efficiency and sustainability. Although a vast number of studies regarding cyclic amine synthesis has been reported, new synthetic disconnection approaches are still high in demand. Herein, we report a catalytic radical-polar crossover cycloaddition to cyclic amine synthesis triggered from primary sulfonamide under photoredox condition. This newly developed disconnection, comparable to established synthetic approaches, will allow to construct β, β-disubstituted cyclic amine and β-monosubstituted cyclic amine derivatives efficiently. This study highlights the unique utility of primary sulfonamide as a bifunctional reagent, which acts as a radical precursor and a nucleophile. The open-shell methodology demonstrates broad tolerance to various functional groups, drug derivatives and natural products in an economically and sustainable fashion.

Rh-Catalyzed Chemodivergent [3+3] Annulations of Diazoenals and α-Aminoketones: Direct Synthesis of Functionalized 1,2-Dihydropyridines and Fused 1,4-Oxazines

Novel rhodium-catalyzed [3+3] annulations of diazoenals and α-amino ketones has been disclosed here. The reactivity of diazoenals has been switched from carbenoid to vinylogous NH-insertion by altering acyclic to cyclic α-amino ketones. In this direction, we report an efficient strategy to synthesize 1,2-dihydropyridines (DHPs) and fused 1,4-oxazines. Mechanistic investigation revealed that the formyl group is necessary for carbenoid [3+3] annulation and the cyclohexyl group is the dictating factor for vinylogous NH- insertion. The synthetic utility of 1,2-dihydropyridines was demonstrated by synthesizing piperidine, pyrido[1,2-a]indole, and 2-pyridone scaffolds. Further, structural diversification of fused 1,4-oxazines resulted in the short synthesis of hexahydroquinolin-2(1H)-ones, hexahydro quinolines and tetrahydroquinolinones via ring opening rearrangement and a new oxidative deformylation, respectively.

Antiproliferative piperidine alkaloids from the leaves of Alocasia macrorrhiza

Seventeen piperidine alkaloids, including 15 previously undescribed 2-substituted-6-(9-phenylnonyl)-piperidine-3,4-diol alkaloids and a previously undescribed 2-substituted-6-(9-phenylnonyl)-piperidine-3-ol alkaloid, were isolated from the leaves of Alocasia macrorrhiza (L.) Schott. Their planar structures and configurations were elucidated based on HR-ESI-MS, 1D and 2D NMR, Snatzke's method, modified Mosher method, single-crystal X-ray crystallography, as well as quantum chemical calculation. It was found that ΔδH5b-H5a can be used to elucidate the relative configuration of 2,3,4,6-tetrasubstituted piperidine, by analyzing the NMR data of 2-substituted-6-(9-phenylnonyl)-piperidine-3,4-diol. Antiproliferative activity was evaluated for all of the alkaloids, and compounds 6-8 showed considerable inhibitory activity against K562 cell line, with the IC50 values of 17.24 ± 1.62, 19.31 ± 0.9 and 18.77 ± 1.09μM, respectively. Furthermore, compounds 6 and 7 exerted an antiproliferative effect by inducing apoptosis.

Multi-target potential of newly designed tacrine-derived cholinesterase inhibitors: Synthesis, computational and pharmacological study

Simple and scalable synthetic approach was used for the preparation of thirteen novel tacrine derivatives consisting of tacrine and N-aryl-piperidine-4-carboxamide moiety connected by a five-methylene group linker. An anti-Alzheimer disease (AD) potential of newly designed tacrine derivatives was evaluated against two important AD targets, acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). In vitro pharmacological evaluation showed strong ChE inhibitory activity of all compounds, with IC50 values ranging from 117.5 to 455 nM for AChE and 34 to 324 nM for BuChE. As a representative of the series with the best cytotoxicity / ChE inhibitory activity ratio, expressed as the selectivity index (SI), 2-chlorobenzoyl derivative demonstrated mixed-type inhibition on AChE and BuChE, suggesting binding to both CAS and PAS of the enzymes. It also exhibited antioxidant capacity and neuroprotective potential against amyloid-β (Aβ) toxicity in the culture of neuron-like cells. In-depth computational analysis corroborated well with in vitro ChE inhibition, illuminating that all compounds exhibit significant potential in targeting both enzymes. Molecular dynamics (MD) simulations revealed that 2-chlorobenzoyl derivative, created complexes with AChE and BuChE that demonstrated sufficient stability throughout the observed MD simulation. Computationally predicted ADME properties indicated that these compounds should have good blood-brain barrier (BBB) permeability, an important factor for CNS-targeting drugs. Overall, all tested compounds showed promising pharmacological behavior, highlighting the multi-target potential of 2-chlorobenzoyl derivative which should be further investigated as a new lead in the drug development process.

Synthesis of Phenol-Pyridinium Salts Enabled by Tandem Electron Donor-Acceptor Complexation and Iridium Photocatalysis

Herein, we describe a dual photocatalytic system to synthesize phenol-pyridinium salts using visible light. Utilizing both electron donor-acceptor (EDA) complex and iridium(III) photocatalytic cycles, the C-N cross-coupling of unprotected phenols and pyridines proceeds in the presence of oxygen to furnish pyridinium salts. Photocatalytic generation of phenoxyl radical cations also enabled a nucleophilic aromatic substitution (SNAr) of a fluorophenol with an electron-poor pyridine. Spectroscopic experiments were conducted to probe the mechanism and reaction selectivity. The unique reactivity of these phenol-pyridinium salts were displayed in several derivatization reactions, providing rapid access to a diverse chemical space.

Nitrile stabilized synthesis of pyrrolidine and piperidine derivatives via tandem alkynyl aza-Prins-Ritter reactions

An efficient methodology for the synthesis of N-(pyrrolidine-3-ylidenemethyl)acetamides mediated by triflic acid in good yields with separable Z/E isomers within a short reaction time has been demonstrated. The reaction involves the initial formation of the pyrrolidin-3-ylidenemethylium carbocation via the Prins cyclization reaction followed by the Ritter reaction to produce N-(pyrrolidine-3-ylidenemethyl)acetamides. This methodology is also used for the synthesis of their piperidine derivatives.

A General Strategy for N-(Hetero)arylpiperidine Synthesis Using Zincke Imine Intermediates

Methods to synthesize diverse collections of substituted piperidines are valuable due to the prevalence of this heterocycle in pharmaceutical compounds. Here, we present a general strategy to access N-(hetero)arylpiperidines using a pyridine ring-opening and ring-closing approach via Zincke imine intermediates. This process generates pyridinium salts from a wide variety of substituted pyridines and (heteroaryl)anilines; hydrogenation reactions and nucleophilic additions then access the N-(hetero)arylpiperidine derivatives. We successfully applied high-throughput experimentation (HTE) using pharmaceutically relevant pyridines and (heteroaryl)anilines as inputs and developed a one-pot process using anilines as nucleophiles in the pyridinium salt-forming processes. This strategy is viable for generating piperidine libraries and applications such as the convergent coupling of complex fragments.

Piperidine: A Versatile Heterocyclic Ring for Developing Monoamine Oxidase Inhibitors

The monoamine oxidase enzyme (MAO), which is bound on the membrane of mitochondria, catalyzes the oxidative deamination of endogenous and exogenous monoamines, including monoamine neurotransmitters such as serotonin, adrenaline, and dopamine. These enzymes have been proven to play a significant role in neurodegeneration; thus, they have recently been researched as prospective therapeutic targets for neurodegenerative illness treatment and management. MAO inhibitors have already been marketed as neurodegeneration illness treatments despite their substantial side effects. Hence, researchers are concentrating on developing novel molecules with selective and reversible inhibitory properties. Piperine, which is a phytochemical component present in black pepper, has been established as a potent MAO inhibitor. Piperine encompasses a piperidine nucleus with antibacterial, anti-inflammatory, antihypertensive, anticonvulsant, antimalarial, antiviral, and anticancer properties. The current Review focuses on the structural changes and structure-activity relationships of piperidine derivatives as MAO inhibitors.

Palladium-Catalyzed Arylation of Endocyclic 1-Azaallyl Anions: Concise Synthesis of Unprotected Enantioenriched cis-2,3-Diarylpiperidines

Unprotected cis-2,3-diarylpiperidines are synthesized through an unprecedented palladium-catalyzed cross-coupling reaction between aryl halides and elusive endocyclic 1-azaallyl anions. These intermediates are generated in situ by the deprotonation of 2-aryl-1-piperideines, precursors that are readily prepared in two operations from simple piperidines. An asymmetric version of this reaction with (2R, 3R)-iPr-BI-DIME as the ligand provides products in moderate to good yields and enantioselectivities. This study significantly expands the synthetic utility of endocyclic 1-azaallyl anions.

Applications of palladium-catalyzed C-N cross-coupling reactions in pharmaceutical compounds

C-N cross-coupling bond formation reactions have become valuable approaches to synthesizing anilines and their derivatives, known as important chemical compounds. Recent developments in this field have focused on versatile catalysts, simple operation methods, and green reaction conditions. This review article presents an overview of C-N cross-coupling reactions in pharmaceutical compound synthesis reports. Selected examples of N-arylation reactions of various nitrogen-based compounds and aryl halides are defined for preparing pharmaceutical molecules.