Recent Advances in Pyridine Scaffold: Focus on Chemistry, Synthesis, and Antibacterial Activities

Development of Membrane-Targeting Osthole Derivatives Containing Pyridinium Quaternary Ammonium Moieties with Potent Anti-Methicillin-Resistant Staphylococcus aureus Properties

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of hospital- and community-acquired infections, necessitating the development of novel antibacterials. Here, we designed and synthesized 30 osthole derivatives with pyridinium quaternary ammonium moieties. In vitro bioassay showed that compounds 8u and 8ac exhibited potent antibacterial activity against S. aureus ATCC 29213 and ten clinical MRSA isolates (MIC = 0.5-1 μg/mL), with low hemolytic activity, rapid bactericidal effects, and minimal resistance induction. In MRSA-infected mouse models of skin abscesses and sepsis, 8u and 8ac also displayed excellent antibacterial effects and safety, which were comparable to vancomycin. Mechanistic studies revealed that 8u and 8ac selectively target bacterial membranes via binding to phosphatidylglycerol (PG), increasing intracellular reactive oxygen species (ROS), inducing content leakage, and ultimately causing bacterial death. These findings suggest 8u and 8ac as promising novel lead candidates for anti-MRSA drug development.

Antiparasitic and Antifungal Activities of Cetyl-Maritima, a New N-Cetyl-Modified Maritima Derivative

Background/Objectives: New drugs are urgently needed for the treatment of neglected tropical diseases including leishmaniasis and eumycetoma, as well as globally occurring parasitic diseases such as toxoplasmosis. Fragrances, both natural and synthetic, were shown to be a rich source for the development of new anti-infectives and warrant deeper investigations. Exemplarily, we synthetically optimized the fragrance 4-(4,8-dimethyl-3,7-nonadienyl)-pyridine, a.k.a. Maritima, a pyridine derivative with marine odor. Methods: A new cationic N-cetyl-modified derivative of Maritima (dubbed Cetyl-Maritima), obtained by alkylation of Maritima, was tested for its activity against Madurella mycetomatis (M. mycetomatis) fungi, as well as against Toxoplasma gondii (T. gondii) and Leishmania major (L. major) protozoal parasites. Results: Cetyl-Maritima was found to be more strongly antifungal than the parent Maritima and a known antibiotic cetylpyridinium salt. Cetyl-Maritima also showed a similar activity against T. gondii parasites and, most notably, exhibited sub-micromolar activity against L. major amastigotes. Conclusions: The considerable antileishmanial activity of Cetyl-Maritima might lead to the development of a new potent and cost-effective drug candidate for the therapy of leishmaniasis and other infectious diseases caused by kinetoplastid parasites.

Reaction strategies for the meta-selective functionalization of pyridine through dearomatization

The pyridine moiety is a crucial structural component in various pharmaceuticals. While the direct ortho- and para-functionalization of pyridines is relatively straightforward, the meta-selective C-H functionalization remains a significant challenge. This review highlights dearomatization strategies as a key area of interest in expanding the application of meta-C-H functionalization of pyridines. Dearomatization enables the meta-functionalization through various catalytic methods that directly generate dearomatization products, and some products can be rearomatized back to pyridine derivatives. Furthermore, this article also covers the dearomatization of multiple positions of pyridine in the synthesis of polycyclic compounds. It offers a comprehensive overview of the latest advancements in dearomatization at different positions of pyridine, aiming to provide a valuable resource for researchers in this field. It also highlights the advantages and limitations of existing technologies, aiming to inform a broader audience about this important field and foster its future development.

Two-Step Formation of Substituted Pyridines from Iodoenones

A new access to substituted pyridines was developed from iodoenones. This two-step procedure involves a Sonogashira coupling with a free alkyne containing a nosylamide followed by a thiophenol treatment in basic conditions that triggers nosyl deprotection, a Michael-retro-Michael process, condensation, and isomerization in cascade to yield the heterocycle. This method enables the introduction of different substituents at several pyridine positions. This approach offers new synthetic opportunities to produce heterocycles present in many bioactive compounds.

Discovery of Quinazolone Pyridiniums as Potential Broad-Spectrum Antibacterial Agents

The overprescription of antibiotics in medicine and agriculture has accelerated the development and spread of antibiotic resistance in bacteria, which severely limits the arsenal available to clinicians for treating bacterial infections. This work discovered a new class of heteroarylcyanovinyl quinazolones and quinazolone pyridiniums to surmount the increasingly severe bacterial resistance. Bioactive assays manifested that the highly active compound 19a exhibited strong inhibition against MRSA and Escherichia coli with extremely low MICs of 0.5 μg/mL, being eightfold more active than that of norfloxacin (MICs = 4 μg/mL). The highly active 19a with rapid bactericidal properties displayed imperceptible resistance development trends, negligible hemolytic toxicity, and effective biofilm inhibitory effects. Preliminary explorations on antibacterial mechanisms revealed that compound 19a could cause membrane damage, embed in intracellular DNA to hinder bacterial DNA replication, and induce metabolic dysfunction. Surprisingly, active 19a was found to trigger the conformational change in PBP2a of MRSA to open the active site, which might account for its high inhibition against MRSA. In addition, the little effect of molecule 19a on the production of reactive oxygen species indicated that bacterial death was not caused by oxidative stress. The above comprehensive analyses highlighted the large potential of quinazolone pyridiniums as multitargeting broad-spectrum antibacterial agents.

Cracking the code: the clinical and molecular impact of aminopyridines; a review (2019-2024)

Aminopyridines belong to a class of compounds that are monoamino and diamino derivatives of pyridine. They work primarily by blocking voltage-gated potassium channels in a dose-dependent manner. Essential heterocycles used extensively in synthetic, natural products, and medicinal chemistry are aminopyridine and its derivatives. A vast array of biological and pharmacological effects can result from the interaction of aminopyridine rings with different enzymes and receptors, due to their unique structural properties. Aminopyridine research is continually growing, and there are now greater expectations for how it may aid in the treatment of numerous disorders. This review article will serve as an innovative platform for researchers investigating aminopyridine compounds, intending thoroughly to examine both traditional and novel synthesis strategies in addition to investigating the various biological characteristics displayed by these adaptable heterocycles. We attempt to provide valuable insights that will contribute to further progress in the synthesis and utilization of aminopyridines in various fields.

Recent Progresses in Development of Heterocyclic Compounds for Epilepsy Treatment: Key Research Highlights from 2019-2024

Epilepsy which is a chronic neurological disorder is characterized by recurrent seizure poses a significant challenge to healthcare professionals worldwide. Most of antiepileptic drugs have serious side effects that might affect the quality of life such as fatigue, dizziness, weight gain and cognitive impairments. In this context, the search for more effective and potential antiepileptic drug candidate has led to a growing interest in the field of synthesis of heterocyclic compounds. This review will focus on the utilization of heterocyclic moieties including imidazole, indole, thiazole, triazine, quinazoline and oxazole which show remarkable anticonvulsant properties. Furthermore, the exploration of various methodologies for the synthesis of heterocyclic anticonvulsant drugs such as green methodologies and microwave assisted protocols have contributed to the development of environment friendly, more efficient and potential approaches. The review will distinguish from previous ones by specifically focusing on innovative synthetic methodologies, including greener methodologies and micro-assisted techniques, that contribute to eco-friendly and environment benign approaches during 2019-2024. In addition to this, the review will focus on the Structure Activity Relationship (SAR) studies of heterocyclic compounds in order to offer insight into the design of next generation antiepileptic drugs with improved efficacy and reduced side effects.

Comprehensive drug-like assessment of pyridine carbothioamide analogs: from molecular modeling to in-vivo evaluation

AIM

To evaluate the anti-inflammatory potential of novel class of chemical compounds designed by the linkage of carbothioamide moiety with pyridine.

MATERIALS & METHODS

In silico analysis was conducted using molecular docking followed by an in vitro cytotoxicity assay and evaluation of anti-inflammatory activity. Subsequently, in vivo performance was determined using the Complete Freund's Adjuvant-induced inflammatory model, employing macroscopic, histopathological, and protein expression analyses.

RESULTS

Molecular interaction studies revealed that compound R2 displayed the most favorable binding mode with human nitric oxide synthase, cyclooxygenase-1, and cycloxygenase-2. All compounds exhibit dose-dependent cytotoxicity. Notably, compound R4 was safer at higher concentration, whereas compound R2 was comparatively toxic. The in vitro anti-inflammatory activity demonstrated half maximal inhibitory concentration (IC50) values ranging from 10.25 ± 0.0 to 23.15 ± 4.24 µM, with compound R6 exhibiting the lowest IC50 value and compound R3 showing the highest. The in vivo results corroborated the anti-inflammatory effects, with a significant reduction in paw size (p < 0.001). Among the tested compounds, compound R4 exhibited the most potent anti-inflammatory activity, whereas R2 exhibited the least potency.

CONCLUSION

The study highlights the promise of discovering new anti-inflammatory drugs containing pyridine moiety with proven potency, efficacy, and reduced side effects.

Novel Copper(II) Coordination Compounds Containing Pyridine Derivatives of N4-Methoxyphenyl-Thiosemicarbazones with Selective Anticancer Activity

Ten coordination compounds, [Cu(L1)Cl] (C1), [Cu(L1)NO3] (C2), [Cu(L2)Cl] (C3), [Cu(L2)NO3] (C4), [Cu(L3)Cl] (C5), [Cu(L3)NO3] (C6), [Cu(L4)NO3] (C7), [Cu(L4)Cl] (C8), [Cu(L5)Cl] (C9), and [Cu(L5)NO3] (C10), containing pyridine derivatives of N4-methoxyphenyl-thiosemicarbazones were synthesized and characterized. The molecular structure of four compounds was investigated using single crystal X-ray diffraction. Spectral analysis techniques such as FT-IR, 1H NMR, 13C NMR, elemental analysis, and molar conductivity were used for all the synthesized compounds. The tested synthesized compounds were evaluated for their anticancer activity and selectivity against a variety of cancer cell lines, including HL-60, LNCaP, MCF-7, HepG-2, K-562, HeLa, BxPC-3, RD, and MDCK normal cell line. Most compounds demonstrated selective anticancer activity superior to doxorubicin. Notably, all ligands showed high antiproliferative activity against HL-60 cells, with IC50 values between 0.01 and 0.06 µM and a selectivity index as high as 5000. Coordination of copper(II) with ligands HL1 and HL3 notably enhanced antiproliferative activity, lowering the IC50 to 0.03 µM. Additionally, the antioxidant activity of these compounds was assessed, revealing that all tested ligands and most coordination compounds exhibited greater antioxidant activity compared to Trolox, with some ligands showing activity up to 12.3 times higher. Toxicity studies on Daphnia magna indicated low toxicity for the ligands, generally less than doxorubicin, with LC50 values ranging from 13 to 90 µM, suggesting moderate toxicity. Conversely, the coordination complexes were more toxic, with LC50 values between 0.5 and 13 µM.

Cutting-edge Bioinformatics strategies for synthesizing Cyclotriazadisulfonamide (CADA) analogs in next-Generation HIV therapies

Cyclotriazadisulfonamide (CADA) is a macrocyclic compound known for its unique mechanism in inhibiting HIV infection by downregulating the CD4 T-cell receptor, a crucial entry point for the virus. Unlike other antiretrovirals, CADA exhibits activity against a wide range of HIV strains, as all HIV variants require CD4 binding for infection. Furthermore, CADA has shown a synergistic effect with clinically approved anti-HIV drugs, offering potential for enhanced therapeutic strategies (Vermeire & Schols, [65]). One proposed mechanism for CADA's inhibition of the CD4 receptor involves blocking the gates of the Sec61 channel, thereby preventing its translocation. However, CADA suffers from poor solubility and bioavailability. To address this, the study aimed to design CADA analogs with improved binding to the Sec61 channel, enhanced bioavailability, and reduced toxicity. The analogs were designed using SeeSAR, with Avogadro and Meeko used for 3D configuration and pseudoatom placement, respectively. AutoDock Vina version 1.2.4 was employed to predict the binding energies of these analogs. Of the 113 analogs designed, 93 demonstrated a more negative binding energy to the Sec61 channel compared to CADA. Structure-binding energy analyses were done to the top-binding analogs to show favorable structural modifications. Enzyme-ligand interactions were analyzed to elucidate the forces contributing to these binding energies. Additionally, 33 of the 113 analogs were deemed bioavailable using a bioavailability criteria specific for macrocycles. Toxicity predictions using PASS Online and StopTox identified analogs JGL023, JGL024, JGL032, and JGL047 as potential drug candidates. Molecular dynamics simulations using Gromacs-2020.4 revealed that JGL023 and JGL032 exhibited the most favorable binding to the Sec61 channel, as determined by evaluating ligand and residue flexibility, compactness, contact frequency, motion pathways, free energy, and other relevant parameters. Synthetic routes for these four analogs were proposed for future studies. The results of this study offer a new perspective on developing drugs to inhibit HIV entry.

Antibacterial Activity and Antifungal Activity of Monomeric Alkaloids

Scientists are becoming alarmed by the rise in drug-resistant bacterial and fungal strains, which makes it more costly, time-consuming, and difficult to create new antimicrobials from unique chemical entities. Chemicals with pharmacological qualities, such as antibacterial and antifungal elements, can be found in plants. Alkaloids are a class of chemical compounds found in nature that mostly consist of basic nitrogen atoms. Biomedical science relies heavily on alkaloid compounds. Based on 241 papers published in peer-reviewed scientific publications within the last ten years (2014-2024), we examined 248 natural or synthesized monomeric alkaloids that have antifungal and antibacterial activity against Gram-positive and Gram-negative microorganisms. Based on their chemical structure, the chosen alkaloids were divided into four groups: polyamine alkaloids, alkaloids with nitrogen in the side chain, alkaloids with nitrogen heterocycles, and pseudoalkaloids. With MIC values of less than 1 µg/mL, compounds 91, 124, 125, 136-138, 163, 164, 191, 193, 195, 205 and 206 shown strong antibacterial activity. However, with MIC values of below 1 µg/mL, compounds 124, 125, 163, 164, 207, and 224 demonstrated strong antifungal activity. Given the rise in antibiotic resistance, these alkaloids are highly significant in regard to their potential to create novel antimicrobial drugs.

Application of magnetic deep eutectic solvents as an efficient catalyst in the synthesis of new 1,2,3-triazole-nicotinonitrile hybrids via a cooperative vinylogous anomeric-based oxidation

Magnetic deep eutectic solvents (MDESs) are adjuvants and an emerging subclass of heterogeneous catalysts in organic transformations. Herein, choline chloride (Ch/Cl) embedded on naphthalene bis-urea-supported magnetic nanoparticles, namely, Fe3O4@SiO2@DES1, was constructed by a special approach. This compound was scrutinized and characterized by instrumental techniques such as FTIR, thermogravimetry and derivative thermogravimetry (TGA/DTG), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), elemental mapping, vibrating sample magnetometer (VSM) and X-ray diffraction (XRD) analyses. Potential catalytic activity of Fe3O4@SiO2@DES1 was impressive, facilitating the synthesis of new 1,2,3-triazole-nicotinonitrile hybrids via a multicomponent method with 65-98% yields. Enhanced rates, high yields, mild reaction conditions, and recycling and reusability of Fe3O4@SiO2@DES1 are the distinct benefits of this catalytic organic synthetic methodology.

A decade of pyridine-containing heterocycles in US FDA approved drugs: a medicinal chemistry-based analysis

Heterocyclic scaffolds, particularly, pyridine-containing azaheterocycles, constitute a major part of the drugs approved in the past decade. In the present review, we explored the pyridine ring part of US FDA-approved small molecules (2014-2023). The analysis of the approved drugs bearing a pyridine ring revealed that a total of 54 drugs were approved. Among them, the significant number comprised the anticancer category (18 drugs, 33%), followed by drugs affecting the CNS system (11 drugs, 20%), which include drugs to treat migraines, Parkinsonism disorders, chemotherapeutic-induced nausea, insomnia, and ADHD or as CNS-acting analgesics or sedatives. Next, six drugs (11%) were also approved to treat rare conditions, followed by five drugs that affect the hematopoietic system. The analysis also revealed that drug approval was granted for antibiotics, antivirals, and antifungals, including drugs for the treatment of tropical and sub-tropical diseases. Primary drug targets explored were kinases, and the major metabolizing enzyme was CYP3A4. Further analysis of formulation types revealed that 50% of the approved drugs were tablets, followed by 17% capsules and 15% injections. Elemental analysis showed that most approved drugs contained sulfur, while fluorine was noted in 32 compounds. Therefore, the present review is a concerted effort to cover drugs bearing pyridine rings approved in the last decade and provide thorough discussion and commentary on their pharmacokinetics and pharmacodynamics aspects. Furthermore, in-depth structural and elemental analyses were explored, thus providing comprehensive guidance for medicinal chemists and scientists working in allied science domains.

An Overview of Naphthylimide as Specific Scaffold for New Drug Discovery

Naphthylimides play a pivotal role as aromatic heterocyclic compounds, serving as the foundational structures for numerous pharmacologically significant drugs. These drugs encompass antibacterial, antifungal, anticancer, antimalarial, antiviral, anti-inflammatory, antithrombotic, and antiprotozoal agents. The planar and heteroaromatic characteristics of naphthylimides grant them a strong ability to intercalate into DNA. This intercalation property renders naphthylimide derivatives highly valuable for various biological activities. The advantageous pharmacological activity and ease of synthesis associated with naphthylimides and their derivatives provide significant benefits in the design and development of new compounds within this class. Currently, only a few such molecules are undergoing preclinical and clinical evaluations. In this paper, we have compiled the literature on naphthylimides reported by researchers from 2006 to 2024. Our focus lies on exploring the pharmacological activities of their analogues from a drug development and discovery perspective, while examining their structure-activity relationship and mechanisms of action.

An In-Depth Exploration of Six Decades of the Kröhnke Pyridine Synthesis

The Kröhnke Pyridine Synthesis has been discovered about six decades ago (1961), by Fritz Kröhnke and Wilfried Zecher at the University of Giessen. The original method involved the reaction of α-pyridinium methyl ketone salts with α,β-unsaturated carbonyl compounds in the presence of a nitrogen source, frequently ammonium acetate. Since its discovery, the Kröhnke methodology has been demonstrated to be suitable for the preparation of mono-, di-, tri- and tetra-pyridines, with important applications in several research fields. Over the years, a number of modifications to the original approach have been developed and reported, enabling for the broad applicability of these methods even in modern days, also for the synthesis of non-pyridine compounds. In this critical and tutorial review, we will thoroughly explore and discuss the potential of the original method, the refinements that have been made over the years, as well as some applications arising from each type of pyridine and/or non-pyridine compounds produced by Kröhnke's approach.

Synthesis and Antimicrobial Activity of Newly Synthesized Nicotinamides

Antioxidants are promising compounds with antimicrobial activity against drug-resistant pathogens, especially when combined with conventional antimicrobials. Our study aimed to characterize the structure of nicotinamides synthesized from nicotinic acid and thiocarbohydrazones and to evaluate their antibacterial and antifungal activity. Seven nicotinic acid hydrazides (NC 1-7) were synthesized using mono-thiocarbohydrazones with hydroxyl group substituents, along with quinolone, phenolic, and pyridine rings known for their antimicrobial activity. The in vitro antimicrobial activity of NC 1-7, at concentrations ranging from 0.001 to 1 mM, was tested against Staphylococcus aureus (ATCC 6538), Enterococcus faecalis (ATCC 29212), Pseudomonas aeruginosa (ATCC 27853), Klebsiella pneumoniae (NCIMB 9111), and Candida albicans (ATCC 24433) using the broth microdilution method per EUCAST 2024 guidelines. Microorganism survival percentages were calculated based on optical density, and target fishing using the PharmMapper database identified potential molecular targets. The results showed that P. aeruginosa was most susceptible to the compounds, while C. albicans was the least susceptible. NC 3 significantly inhibited P. aeruginosa and K. pneumoniae growth at 0.016 mM, while higher concentrations were required for S. aureus, E. faecalis, and C. albicans. NC 5 was most effective against gram-positive bacteria at 0.03 mM. Only NC 4 completely inhibited C. albicans below 1 mM. NC 3, with the lowest concentration for 50% growth inhibition (0.016-0.064 mM), showed promising antibacterial potential against specific AMR-related proteins (bleomycin resistance protein, HTH-type transcriptional regulator QacR, and streptogramin A acetyltransferase), suggesting that this class of compounds could enhance or restore the activity of established antibiotics.

Synthesis of nicotinimidamides via a tandem CuAAC/ring-cleavage /cyclization/oxidation four-component reaction and their cytotoxicity

Nicotinamide and its derivatives, recognized as crucial drug intermediates, have been a focal point of extensive chemical modifications and rigorous pharmacological studies. Herein, a series of novel nicotinamide derivatives, nicotinimidamides, were synthesized via a tandem CuAAC/ring-cleavage/cyclization/oxidation four-component reaction procedure from O-acetyl oximes, terminal ynones, sulfonyl azides, and NH4OAc. This strategy is significantly more efficient than previously reported, and the cytotoxicity of the nicotinimidamides is also tested. This project not only exhibits a sustainable and eco-friendly domino methodology for the creation of nicotinimidamides but also presents a promising candidate for liver cancer treatment.

Unveiling dynamics of nitrogen content and selected nitrogen heterocycles in thrombin inhibitors: a ceteris paribus approach

BACKGROUND

Despite the progress in comprehending molecular design principles and biochemical processes associated with thrombin inhibition, there is a crucial need to optimize efforts and curtail the recurrence of synthesis-testing cycles. Nitrogen and N-heterocycles are key features of many anti-thrombin drugs. Hence, a pragmatic analysis of nitrogen and N-heterocycles in thrombin inhibitors is important throughout the drug discovery pipeline. In the present work, the authors present an analysis with a specific focus on understanding the occurrence and distribution of nitrogen and selected N-heterocycles in the realm of thrombin inhibitors.

RESEARCH DESIGN AND METHODS

A dataset comprising 4359 thrombin inhibitors is used to scrutinize various categories of nitrogen atoms such as ring, non-ring, aromatic, and non-aromatic. In addition, selected aromatic and aliphatic N-heterocycles have been analyzed.

RESULTS

The analysis indicates that ~62% of thrombin inhibitors possess five or fewer nitrogen atoms. Substituted N-heterocycles have a high occurrence, like pyrrolidine (23.24%), pyridine (20.56%), piperidine (16.10%), thiazole (9.61%), imidazole (7.36%), etc. in thrombin inhibitors.

CONCLUSIONS

The majority of active thrombin inhibitors contain nitrogen atoms close to 5 and a combination of N-heterocycles like pyrrolidine, pyridine, piperidine, etc. This analysis provides crucial insights to optimize the transformation of lead compounds into potential anti-thrombin inhibitors.

Synthesis of Pyridin-2(1H)-imines via the Transformation of Conjugated Ynones

Conjugated ynones represent an important class of reactive species, useful synthetic intermediates, and synthons. However, the reactivity and synthetic applications of ynones are usually focused on the transformation of mono- or dual-functional groups. Herein, we developed a straightforward synthesis of pyridin-2(1H)-imines from the transformation of conjugated ynones. This cascade process probably began with a Michael addition of ynones and 2-aminopyridines, further underwent an intramolecular cyclization to generate the N,O-bidentate intermediates, and finally reacted with sulfonyl azides giving the pyridin-2(1H)-imines with accompanying loss of diazo.

Insights into the potential dual-antibacterial mechanism of Kelisha capsule on Escherichia coli

Traditional Chinese medicine (TCM), AYURVEDA and Indian medicine are essential in disease prevention and treatment. Kelisha capsule (KLSC), a TCM formula listed in the Chinese Pharmacopoeia, has been clinically proven to possess potent antibacterial properties. However, the precise antimicrobial mechanism of KLSC remained unknown. This study aimed to elucidate the dual antibacterial mechanism of KLSC using network pharmacology, molecular docking, and experimental validation. By analyzing the growth curve of Escherichia coli (E. coli), it was observed that KLSC significantly inhibited its growth, showcasing a remarkable antibacterial effect. Furthermore, SEM and TEM analysis revealed that KLSC damaged the cell wall and membrane of E. coli, resulting in cytoplasmic leakage, bacterial death, and the exertion of antibacterial effects. The network pharmacology analysis revealed that KLSC exhibited an effect on E. coli ATP synthase, thereby influencing the energy metabolism process. The molecular docking outcomes provided evidence that the active compounds of KLSC could effectively bind to the ATP synthase subunit. Subsequently, experimental findings substantiated that KLSC effectively suppressed the activity of ATP synthase in E. coli and consequently decreased the ATP content. This study highlighted the dual antibacterial mechanism of KLSC, emphasizing its effects on cell structure and energy metabolism, suggesting its potential as a natural antibacterial agent for E. coli-related infections. These findings offered new insights into exploring the antibacterial mechanisms of TCM by focusing on the energy metabolism process.

Reaction Pattern and Mechanistic Aspects of Iodine and Iodine-Based Reagents in Selenylation of Aliphatic, Aromatic, and (Hetero)Cyclic Systems

Organoselenium compounds have been the subject of extensive research since the discovery of the biologically active compound ebselen. Ebselen has recently been found to show activity against the main protease of the virus responsible for COVID-19. Other organoselenium compounds are also well-known for their diverse biological activities, with such compounds exhibiting interesting physical properties relevant to the fields of electronics, materials, and polymer chemistry. In addition, the incorporation of selenium into various organic molecules has garnered significant attention due to the potential of selenium to enhance the biological activity of these molecules, particularly in conjunction with bioactive heterocycles. Iodine and iodine-based reagents play a prominent role in the synthesis of organoselenium compounds, being valued for their cost-effectiveness, non-toxicity, and ease of handling. These reagents efficiently selenylate a broad range of organic substrates, encompassing alkenes, alkynes, and cyclic, aromatic, and heterocyclic molecules. They serve as catalysts, additives, inducers, and oxidizing agents, facilitating the introduction of different functional groups at alternate positions in the molecules, thereby allowing for regioselective and stereoselective approaches. Specific iodine reagents and their combinations can be tailored to follow the desired reaction pathways. Here, we present a comprehensive review of the progress in the selenylation of organic molecules using iodine reagents over the past decade, with a focus on reaction patterns, solvent effects, heating, microwave, and ultrasonic conditions. Detailed discussions on mechanistic aspects, such as electrophilic, nucleophilic, radical, electrochemical, and ring expansion reactions via selenylation, multiselenylation, and difunctionalization, are included. The review also highlights the formation of various cyclic, heterocyclic, and heteroarenes resulting from the in situ generation of selenium intermediates, encompassing cyclic ketones, cyclic ethers, cyclic lactones, selenophenes, chromones, pyrazolines, pyrrolidines, piperidines, indolines, oxazolines, isooxazolines, lactones, dihydrofurans, and isoxazolidines. To enhance the reader's interest, the review is structured into different sections covering the selenylation of aliphatic sp2/sp carbon and cyclic sp2 carbon, and then is further subdivided into various heterocyclic molecules.

Pd-NHC (NHC = N-Heterocyclic Carbene)-Catalyzed B-Alkyl Suzuki Cross-Coupling of 2-Pyridyl Ammonium Salts by N-C Activation: Application to the Discovery of Agrochemical Molecular Hybrids

2-Alkylpyridines are a privileged scaffold throughout the realm of organic synthesis and play a key role in natural products, pharmaceuticals, and agrochemicals. Herein, we report the first B-alkyl Suzuki cross-coupling of 2-pyridyl ammonium salts to access functionalized 2-alkylpyridines. The use of well-defined, operationally simple Pd-NHCs permits for an exceptionally broad scope of the challenging B-alkyl C-N cross-coupling with organoboranes containing β-hydrogen, representing a novel method for the discovery of highly sought-after molecules for plant protection.

Chemoselectivity of the CuAAC/Ring Cleavage/Cyclization Reaction between Enaminones and α-Acylketenimine

Ketenimines represent an important class of reactive species, useful synthetic intermediates, and synthons. However, in general, ketenimines preferentially undergoes nucleophilic addition reactions with hydroxyl and amino groups, and carbon functional groups remain a less studied subset of such systems. Herein, we develop a straightforward syntheses of pyridin-4(1H)-imines that is achieved by cyclization of a reacting enaminone unit with α-acylketenimine which is generated from the reactions of sulfonyl azides and terminal ynones in situ (CuAAC/Ring cleavage reaction). The cascade process preferentially starts with the nucleophilic α-C of the enaminone unit instead of an amino group, attacking the electron-deficient central carbon of ketenimine, and the chemoselectivity unconventional products pyridin-4(1H)-imines were formed by intramolecular cyclization.

A New Benzo[6,7]oxepino[3,2-b] Pyridine Derivative Induces Apoptosis in Canine Mammary Cancer Cell Lines

CMC is the most frequently diagnosed cancer and one of the leading causes of death in non-spayed female dogs. Exploring novel therapeutic agents is necessary to increase the survival rate of dogs with CMC. MPOBA is a BZOP derivative that has a significant anticancer effect in a human cell line. The main goal of this study was to investigate the anticancer properties of MPOBA against two CMC cell lines (REM134 and CMGT071020) using a 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, a wound healing assay, a transwell migration assay, an Annexin V-FITC apoptosis assay with a flow cytometry analysis, a mRNA expression analysis using quantitative real-time PCR (qRT-PCR), and an immunohistochemistry (IHC). According to the accumulated studies, MPOBA caused significant concentration- and time-dependent reductions in cell proliferation and cell migration and induced apoptosis in both CMC cell lines. In gene expression analysis, nine canine genes, including TP53, BCL-2, BAX, epidermal growth factor receptor (EGFR), snail transcription factor (SNAIL), snail-related zinc-finger transcription factor (SLUG), TWIST, E-cadherin, and N-cadherin, were investigated. The mRNA expression results revealed that MPOBA induced upregulation of TP53 and overexpression of the pro-apoptotic gene BAX, together with an inhibition of BCL-2. Moreover, MPOBA also suppressed the mRNA expression levels of SNAIL, EGFR, and N-cadherin and induced upregulation of E-cadherin, crucial genes related to the epithelial-to-mesenchymal transition (EMT). However, there was no significant difference in the IHC results of the expression patterns of vimentin (VT) and cytokeratin (CK) between MPOBA-treated and control CMC cells. In conclusion, the results of the present study suggested that MPOBA exhibited significant anticancer activity by inducing apoptosis in both CMCs via upregulation of TP53 and BAX and downregulation of BCL-2 relative mRNA expression. MPOBA may prove to be a potential candidate drug to be further investigated as a therapeutic agent for CMC.

Synthesis and Biological Activity of Piperidinothiosemicarbazones Derived from Aminoazinecarbonitriles

To investigate how structural modifications affect tuberculostatic potency, we synthesized seven new piperidinothiosemicrabazone derivatives 8-14, in which three of them had a pyrazine ring replacing the pyridine ring. Derivatives 8-9 and 13-14 exhibited significant activity against the standard strain (minimum inhibitory concentration (MIC) 2-4 μg/mL) and even greater activity against the resistant M. tuberculosis strain (MIC 0.5-4 μg/mL). Additionally, the effects of compounds 8-9 were entirely selective (MIC toward other microorganisms ≥ 1000 μg/mL) and non-toxic (IC50 to HaCaT cells 5.8 to >50 μg/mL). The antimycobacterial activity of pyrazine derivatives 11-12 was negligible (MIC 256 to >500 μg/mL), indicating that replacing the aromatic ring was generally not a promising line of research in this case. The zwitterionic structure of compound 11 was determined using X-ray crystallography. Absorption, distribution, metabolism, and excretion (ADME) calculations showed that all compounds, except 11, could be considered for testing as future drugs. An analysis of the structure-activity relationship was carried out, indicating that the higher basicity of the substituent located at the heteroaromatic ring might be of particular importance for the antituberculous activity of the tested groups of compounds.