Search Results (1,512)

This paper presents the expected and unexpected, but typically substituent-dependent, ferrocene-catalyzed DDQ-mediated oxidative transformations of a series of 5,8-bis(methylthio)-1-aryl-1,2-dihydropyridazino[4,5-d]pyridazines and 8-(3,5-dimethyl-1H-pyrazol-1-yl)-5-(methylthio)-1-aryl-1,2-dihydropyridazino[4,5-d]pyridazines. Under noncatalytic conditions the reactions were sluggish, mainly producing a substantial amount of undefined tarry materials; nevertheless, the ferrocene-catalyzed reactions of the 5,8-bis(methylthio)-substituted precursors gave the aromatic products the expected aromatic products in low yields. Their formation was accompanied by ring transformations proceeding via aryne-generating fragmentation/Diels–Alder (DA)/N₂-releasing retro Diels–Alder (rDA) sequence to construct arene-fused phthalazines. On the other hand, neither the noncatalytic nor the catalytic reactions of the 8-pyrazolyl-5-methylthio-substituted dihydroaromatics yielded the expected aromatic products. Instead, depending on their substitution pattern, the catalytic reactions of these pyrazolyl-substituted precursors also led to the formation of dearylated arene-fused phthalazines competing with an unprecedented multistep fragmentation sequence terminated by the hydrolysis of cationic intermediates to give 4-(methylthio)pyridazino[4,5-d]pyridazin-1(2H)-one and the corresponding 3,5-dimethyl-1-aryl-1H-pyrazole. When 0.6 equivalents of DDQ were applied in freshly absolutized THF, a representative pyrazolyl-substituted model underwent an oxidative coupling to give a dimer formed by the interaction of the cationic intermediate, and a part of the N-nucleophilic precursor remained intact. A systematic computational study was conducted on these intriguing reactions to support their complex mechanisms proposed on the basis of the structures of the isolated products. Full article

The tumor microenvironment plays an important role in tumor incidence, metastasis, and chemotherapy resistance. Novel therapeutic strategies targeting the tumor microenvironment have become a research focus in the field of biomedicine. In this study, we developed a smart small-molecule probe, TZ2, featuring pH/GSH dual-responsive characteristics. TZ2 exhibits a unique pH-dependent reaction mechanism: GSH is preferentially covalently modified with maleimide groups in acidic microenvironments (pH < 7), while specifically activating nucleophilic substitutions under alkaline conditions (pH > 7). It is worth noting that TZ2 effectively eliminates intracellular glutathione (GSH) in a time and concentration-dependent manner, demonstrating significant GSH depletion ability in various tumor cell lines. Pharmacodynamic studies have shown that TZ2 not only inhibits the cell cycle by regulating the expression of cell cycle-related proteins, but also effectively suppresses the cloning ability of cancer cells. Furthermore, TZ2 significantly increases the sensitivity of drug-resistant cancer cells to cisplatin. By integrating microenvironment modulation, real-time monitoring, and synergistic therapy, TZ2 provides a novel molecular tool and theoretical basis for tumor theranostics integration. Full article

Lupeol, a naturally occurring pentacyclic triterpenoid widely distributed in various medicinal plants, has attracted significant attention due to its diverse pharmacological properties. In this study, we report the synthesis and structural modification of 14 lupeol derivatives through selective functionalizations at C3 and C30 positions of the lupane skeleton, via the sequential chemoselective introduction of carbonyl moieties and the addition of organometallics. Emphasis has been given to the stereoselective alkylation at C3 using a range of carbanions, including organolithiums, organomagnesiums and organoindiums. The C30 position was modified through oxidative pathways to introduce several functionalities. Full article

Heterocycles—cyclic compounds containing at least one non-carbon heteroatom (e.g., N, O, S)—are fundamental in medicinal chemistry due to their influence on a drug’s physicochemical and biological properties. They improve solubility, bioavailability, and facilitate molecular recognition through their electronic and hydrogen-bonding features. These properties make them indispensable in drug design. This study focuses on the synthesis of a key heterocyclic intermediate: benzyl-N-[4-(2-hydroxyethyl)-1,3-thiazol-2-yl]carbamate. This molecule incorporates a thiazole ring, known for its rigidity and electronic properties, that enhances target interactions. The 2-position bears a Cbz-protected amine, enabling orthogonal deprotection, while the 4-position features a hydroxyethyl side chain, providing a handle for further chemical modifications via nucleophilic substitution. Herein, we report the successful synthesis of this intermediate along with its full ¹H and ¹³C NMR spectra, melting point, and crystal structure, confirming its identity and purity. Full article

A synthesis of substituted 1,4-benzodiazepines has been developed via palladium-catalyzed cyclization of N-tosyl-disubstituted 2-aminobenzylamines with propargylic carbonates. The reaction proceeds through the formation of π-allylpalladium intermediates, which undergo intramolecular nucleophilic attack by the amide nitrogen to afford seven-membered benzodiazepine cores. In reactions involving unsymmetrical diaryl-substituted carbonates, regioselectivity was observed to favor nucleophilic attack at the alkyne terminus substituted with the more electron-rich aryl group, suggesting that electronic effects play a key role in determining product distribution. The versatility of this reaction was further demonstrated by constructing a benzodiazepine framework found in bioactive molecules, indicating its potential utility in medicinal chemistry. Mechanistic insights supported by stereochemical outcomes and X-ray crystallographic analysis of key intermediates reinforce the proposed reaction pathway. This palladium-catalyzed protocol thus offers an efficient and practical approach to access structurally diverse benzodiazepine derivatives. Full article

Fluorinated organic molecules have become indispensable in modern chemistry, owing to the unique properties imparted by fluorine to other compounds, including enhanced metabolic stability, controlled lipophilicity, and improved bioavailability. The site-selective incorporation of fluorine atoms into organic frameworks is essential in pharmaceutical, agrochemical, and material science research. In recent years, catalytic fluorination has become an important methodology for the efficient and selective incorporation of fluorine atoms into complex molecular architectures. This review highlights advances in catalytic fluorination reactions over the past six years and describes the contributions of transition metal catalysts, photocatalysts, organocatalysts, and electrochemical systems that have enabled site-selective fluorination under a variety of conditions. Particular attention is given to the use of well-defined fluorinating agents, including Selectfluor, N-fluorobenzenesulfonimide (NFSI), AlkylFluor, Synfluor, and hypervalent iodine reagents. These reagents have been combined with diverse catalytic systems, such as AgNO₃, Rh(II), Mo-based complexes, Co(II)-salen, and various organocatalysts, including β,β-diaryl serine catalysts, isothiourea catalysts, and chiral phase-transfer catalysts. This review summarizes proposed mechanisms reported in the original studies and discusses examples of electrophilic, nucleophilic, radical, photoredox, and electrochemical fluorination pathways. Recent developments in stereoselective and more sustainable protocols are also examined. By consolidating these strategies, this article provides an up-to-date perspective on catalytic fluorination and its impact on synthetic organic chemistry. Full article

Three previously synthesized ketene dithioacetals were used as intermediates to obtain four nucleophiles to synthesize ten tetra-substituted pyrazoles (11–20). This was achieved through microwave irradiation in ethanol as the solvent, yielding superb results ranging from 68.4% to 90.1%, in agreement with some of the principles of green chemistry. The proposed structures were determined using various spectroscopic techniques, including infrared spectroscopy and hydrogen and carbon-13 nuclear magnetic resonance. Furthermore, the compounds underwent in-silico evaluations using CLC-Pred and AdmetSAR software to predict the absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties. This was combined with molecular docking calculations for four main cancer-related targets for pyrazole core, to facilitate screening for subsequent biological assessments. Based on the data generated from these analyses, it was identified two pyrazoles (11 and 18) likely to exhibit anti-tumor activity, while also demonstrating low toxicity levels. Upon selection, these two pyrazoles were subjected to toxicity assessments using the Artemia salina method and evaluated for their effects on the viability of Jurkat cancer cells with a potency of 45.05 and 14.85 µM to 11 and 18, respectively, and with a potency of above 100 µM for the non-carcinogenic cells HEK 293. Overall, the findings from these studies indicate pyrazole derivatives as potential anti-tumor candidates. Full article

The persistent contamination of aquatic environments by heavy metals, particularly Pb²⁺, Cd²⁺, and Cu^2+, poses a serious global threat due to their toxicity, persistence, and bioaccumulative behavior. In response, low-cost and eco-friendly adsorbents are being explored, among which CaCO₃-based biocomposites derived from mollusk shells have shown exceptional performance. In this study, a hybrid biocomposite composed of poly(vinyl alcohol) (PVA) and oyster shell-derived CaCO₃ was computationally investigated using Density Functional Theory (DFT) to elucidate the electronic and structural basis for its high metal-removal efficiency. Calculations were performed at the B3LYP/6-311++G(d,p), M05-2X/6-311+G(d,p), and M06-2X/6-311++G(d,p) levels using GAUSSIAN 16. Among them, B3LYP was identified as the most balanced in terms of accuracy and computational cost. The hybridization with CaCO₃ reduced the HOMO-LUMO gap by 20% and doubled the dipole moment (7.65 Debye), increasing the composite’s polarity and reactivity. Upon chelation with metal ions, the gap further dropped to as low as 0.029 eV (Cd²⁺), while the dipole moment rose to 17.06 Debye (Pb²⁺), signaling enhanced charge separation and stronger electrostatic interactions. Electrostatic potential maps revealed high nucleophilicity at carbonate oxygens and reinforced electrophilic fields around the hydrated metal centers, correlating with the affinity trend Cu²⁺ > Cd²⁺ > Pb²⁺. Fukui function analysis indicated a redistribution of reactive sites, with carbonate oxygens acting as ambiphilic centers suitable for multidentate coordination. Natural Bond Orbital (NBO) analysis confirmed the presence of highly nucleophilic lone pairs and weakened bonding orbitals, enabling flexible adsorption dynamics. Furthermore, NCI/RDG analysis highlighted attractive noncovalent interactions with Cu²⁺ and Pb²⁺, while FT-IR simulations demonstrated the formation of hydrogen bonding (O–H···O=C) and Ca²⁺···O coordination bridges between phases. Full article

The ReAV enzyme from Rhizobium etli, a representative of Class 3 L-asparaginases, is sequentially and structurally different from other known L-asparaginases. This distinctiveness makes ReAV a candidate for novel antileukemic therapies. ReAV is a homodimeric protein, with each subunit containing a highly specific zinc-binding site created by two cysteines, a lysine, and a water molecule. Two Ser-Lys tandems (Ser48-Lys51, Ser80-Lys263) are located in the close proximity of the metal binding site, with Ser48 hypothesized to be the catalytic nucleophile. To further investigate the catalytic process of ReAV, site-directed mutagenesis was employed to introduce alanine substitutions at residues from the Ser-Lys tandems and at Arg47, located near the Ser48-Lys51 tandem. These mutational studies, along with enzymatic assays and X-ray structure determinations, demonstrated that substitution of each of these highly conserved residues abolished the catalytic activity, confirming their essential role in enzyme mechanism. Full article

Background: Betulinic acid (BA) and some derivatives are well-known antiproliferative compounds. Literature precedents suggest that incorporating triphenylphosphonium (TPP⁺) salts on this triterpenoid scaffold enhances its biological activity. In the present study, we carried out a simple synthesis of C-28 ester derivatives of this triterpenoid conjugated with TPP⁺ bromide salts through 4- to 6-carbon chains via nucleophilic substitution of the corresponding ω-TPP⁺bromoalkanes. Tests for antiproliferative activity in nine cancer cell lines and normal human fibroblasts showed that TPP⁺ incorporation enhanced the potency of BA by more than an order of magnitude, up to 100-fold. BA-C₄-TPP⁺Br⁻, with a four-carbon chain separating the TPP⁺ moiety from the BA, showed remarkable antiproliferative effects, sometimes more potent than the reference drug (Etoposide). This compound exhibited the strongest mitochondrial uncoupling effect in human cancer cells. No significant LDH release was noted in colorectal carcinoma cells at low micromolar concentrations of BA-C₄-TPP⁺Br⁻, and sub-micromolar concentrations were sufficient for inducing apoptosis. The in silico prediction of pharmacokinetic properties suggested high oral absorption (88%), as well as a non-inhibitor and non-substrate profile vs. cytochrome isoenzymes. These results point to this compound as a promising lead for the development of novel anticancer drugs. Full article

The objectives of this study were to design, synthesize, and evaluate the antibacterial activity of a series of novel aminoguanidine-tetralone derivatives. Thirty-four new compounds were effectively synthesized through nucleophilic substitution reaction and guanidinylation reaction. Chemical structures of all the desired compounds were identified by NMR and HR-MS spectroscopy. Most of the synthesized compounds showed significant antibacterial activity against ESKAPE pathogens and clinically resistant Staphylococcus aureus (S. aureus) isolates. S. aureus is an important pathogen that has the capacity to cause a variety of diseases, including skin infections, pneumonia, and sepsis. The most active compound, 2D, showed rapid bactericidal activity against S. aureus ATCC 29213 and MRSA-2 with MIC/MBC values of 0.5/4 µg/mL and 1/4 µg/mL, respectively. The hemolytic activity and cytotoxicity of 2D was low, with HC₅₀ and IC_{50(HEK 293-T)} values of 50.65 µg/mL and 13.09 µg/mL, respectively. Compound 2D induced the depolarization of the bacterial membrane and disrupted bacterial membrane integrity, ultimately leading to death. Molecular docking revealed that dihydrofolate reductase (DHFR) may be a potential target for 2D. In the mouse skin abscess model caused by MRSA-2, 2D reduced the abscess volume, decreased bacterial load, and alleviated tissue pathological damage at doses of 5 and 10 mg/kg. Therefore, compound 2D may be a promising drug candidate for antibacterial purposes against S. aureus. Full article

Biflavonoids are a unique subclass of dietary polyphenolic compounds known for their diverse bioactivities. Despite these benefits, these biflavonoids remain largely underexplored due to their limited natural availability and harsh conditions required for their synthesis, which restricts broader research and application in functional foods and nutraceuticals. To address this gap, we synthesized a library of rare biflavonoids using a radical–nucleophile coupling reaction previously reported by our group. The food grade coupling reaction under weakly alkaline water at room temperature led to isolation of 28 heterocoupled biflavones from 11 monomers, namely 3′,4′-dihydroxyflavone, 5,3′,4′-trihydroxyflavone, 6,3′,4′-trihydroxyflavone, 7,3′,4′-trihydroxyflavone, diosmetin, chrysin, acacetin, genistein, biochanin A, and wogonin. The structures of the dimers are characterized by nuclear magnetic resonance spectroscopy (NMR) and high-resolution mass spectroscopy (HRMS). In addition, we evaluated the antioxidant potential of these biflavones using a DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay and the DPPH value ranges between 0.75 to 1.82 mM of Trolox/mM of sample across the 28 synthesized dimers. Additionally, a three-dimensional quantitative structure–activity relationship (3D-QSAR) analysis was conducted to identify structural features associated with enhanced antioxidant activity. The partial least squares (PLS) regression QSAR model showed acceptable r² = 0.936 and q² = 0.869. Additionally, the average local ionization energy (ALIE), electrostatic potential (ESP), Fukui index (F-), and electron density (ED) were determined to identify the key structural moiety that was capable of donating electrons to neutralize reactive oxygen species. Full article

Background: Plastic is one of the most versatile and widely used materials, but the environmental accumulation of nanoplastics (NPs) poses a risk to human health. Preclinical studies have verified that the liver is one of the main organs susceptible to NPs. Biobran/MGN-3, an arabinoxylan from rice bran, has been shown to have hepatoprotective effects; here, we show Biobran’s ability to alleviate polyethylene nanoplastics (PE-NPs)-induced liver cell toxicity by reversing apoptosis and restoring G2/M cell arrest in mouse liver cells (BNL CL.2). Methods: Toxicological effects were measured using the sulforhodamine B (SRB) assay for cell viability and flow cytometry for cell cycle analysis and apoptosis. An in silico study was also used to demonstrate the docking of PE-NPs to pro-inflammatory mediator proteins (IL-6R, IL-17R, CD41/CD61, CD47/SIRP), cell cycle regulators (BCL-2, c-Myc), as well as serine carboxypeptidase, which is an active ingredient of Biobran. Results: Exposing liver cells to PE-NPs caused a significant decrease in cell viability, with an IC50 value of 334.9 ± 2.7 µg/mL. Co-treatment with Biobran restored cell viability to normal levels, preserving 85% viability at the highest concentration of PE-NPs. Additionally, total cell death observed after exposure to PE-NPs was reduced by 2.4-fold with Biobran co-treatment. The G2/M arrest and subsequent cell death (pre-G0 phase) induced by PE-NPs were normalized after combined treatment. The in silico study revealed that Biobran blocks the nucleophilic centers of PE-NPs, preventing their interaction with pro-inflammatory mediators and cell cycle regulators. Conclusions: These findings highlight the potential use of Biobran as a hepatoprotector against NP toxicity. Full article

The title compound, 4,4-dichloro-1,3-dithietane-2-one, was encountered when opening a commercial capped amber bottle labeled “thiophosgene” that had been stored in a cold room (4 °C) for decades without any special precautions. Treating it as an unknown, the structure was established by single crystal X-ray analysis, and confirmed by ¹³C NMR, FTIR, melting behavior, and elemental analysis; its behavior under several mass spectrometric conditions was also examined. The dithietane appears to be a spontaneously formed cyclodimer of thiophosgene in which exactly one (not zero, not both) of the dichloromethylene moieties has been hydrolyzed to a carbonyl function. The relative long-term stability of the hydrolyzed dimer, along with a pathway back to thiophosgene, suggests that it might serve as a storage vehicle for toxic thiophosgene. Furthermore, as noted elsewhere, the title compound reacts with nucleophiles under mild aqueous conditions, suggesting that it may be a useful probe in chemical biology. Full article

This study explores the chemical composition and synergistic anti-fungal properties of essential oils from the aerial parts of Satavari (Asparagus racemosus Willd.), Dill (Anethum graveolens L.), and lemongrass (Cymbopogon citratus Stapf), along with the peels of Lime (Citrus aurantifolia (Christm.)) and Kaffir lime (Citrus hystrix DC), as well as the leaves of Citrus hystrix DC, against Malassezia furfur, a yeast linked to dandruff and seborrheic dermatitis. Gas chromatography-mass spectrometry (GC-MS) identified key volatile compounds within these oils. In vitro anti-fungal assays evaluated their efficacy individually and in combinations using checkerboard dilution techniques to assess synergy. Results indicated significant antifungal activity, with lemongrass exhibiting the strongest effect (MIC of 0.125% v/v). Notably, a 1:1 combination of lemongrass and kaffir lime essential oils showed synergism, reducing the MIC to 0.0625% v/v. The antifungal activity was primarily attributed to citral and citronellal, with MICs of 0.03125% v/v and 0.125% v/v, respectively. Molecular orbital analysis revealed that the higher energy levels of the lowest unoccupied molecular orbitals (LUMOs) in citral correlate with greater antifungal efficacy, likely due to its enhanced electrophilicity, facilitating nucleophilic interactions with M. furfur’s cellular components. These findings highlight potential applications of essential oil combinations in antifungal therapies. Full article