Oligo(styryl)benzenes liposomal AIE-dots for bioimaging and phototherapy in an in vitro model of prostate cancer

Whilst the development of advanced organic dots with aggregation-induced emission characteristics (AIE-dots) is being intensively studied, their clinical translation in efficient biotherapeutic devices has yet to be tackled. This study explores the synergistic interplay of oligo(styryl)benzenes (OSBs), potent fluorogens with an increased emission in the aggregate state, and Indocyanine green (ICG) as dual Near Infrared (NIR)-visible fluorescent nanovesicles with efficient reactive oxygen species (ROS) generation capacity for cancer treatment using photodynamic therapy (PDT). The co-loading of OSBs and ICG in different nanovesicles has been thoroughly investigated. The nanovesicles' physicochemical properties were manipulated via molecular engineering by modifying the structural properties of the lipid bilayer and the number of oligo(ethyleneoxide) chains in the OSB structure. Diffusion Ordered Spectroscopy (DOSY) NMR and spectrofluorometric studies revealed key differences in the structure of the vesicles and the arrangement of the OSB and ICG in the bilayer. The in vitro assessment of these OSB-ICG nanovesicles revealed that the formulations can increase the temperature and generate ROS after photoirradiation, showing for the first time their potential as dual photothermal/photodynamic (PTT/PDT) agents in the treatment of prostate cancer. Our study provides an exciting opportunity to extend the range of applications of OSB derivates to potentiate the toxicity of phototherapy in prostate and other types of cancer.

Diphenyl Diselenide Through Reduction of Inflammation, Oxidative Injury and Caspase-3 Activation Abates Doxorubicin-Induced Neurotoxicity in Rats

Neurotoxicity associated with chemotherapy is a debilitating side effect of cancer management in humans which reportedly involves inflammatory and oxidative stress responses. Diphenyl diselenide (DPDS) is an organoselenium compound which exhibits its anti-tumoral, anti-oxidant, anti-inflammatory and anti-mutagenic effects. Nevertheless, its possible effect on chemotherapy-induced neurotoxicity is not known. Using rat model, we probed the behavioral and biochemical effects accompanying administration of antineoplastic agent doxorubicin (7.5 mg/kg) and DPDS (5 and 10 mg/kg). Anxiogenic-like behavior, motor and locomotor insufficiencies associated with doxorubicin were considerably abated by both DPDS doses with concomitant enhancement in exploratory behavior as demonstrated by reduced heat maps intensity and enhanced track plot densities. Moreover, with exception of cerebral glutathione (GSH) level, superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities, biochemical data demonstrated reversal of doxorubicin-mediated decline in cerebral and cerebellar antioxidant status indices and the increase in acetylcholinesterase (AChE) activity by both doses of DPDS. Also, cerebellar and cerebral lipid peroxidation, hydrogen peroxide as well as reactive oxygen and nitrogen species levels were considerably diminished in rats administered doxorubicin and DPDS. In addition, DPDS administration abated myeloperoxidase activity, tumour necrosis factor alpha and nitric oxide levels along with caspase-3 activity in doxorubicin-administered rats. Chemoprotection of doxorubicin-associated neurotoxicity by DPDS was further validated by histomorphometry and histochemical staining. Taken together, DPDS through offsetting of oxido-inflammatory stress and caspase-3 activation elicited neuroprotection in doxorubicin-treated rats.

Biological Evaluation of Isosteric Applicability of 1,3-Substituted Cuneanes as m-Substituted Benzenes Enabled by Selective Isomerization of 1,4-Substituted Cubanes

We herein evaluate a biological applicability of 1,3-substituted cuneanes as an isostere of m-substituted benzenes based on its structural similarity. An investigation of a method to obtain 1,3-substituted cuneanes by selective isomerization of 1,4-substituted cubanes enables this attempt by giving a key synthetic step to obtain a cuneane analogs of pharmaceuticals having m-substituted benzene moiety. Biological evaluation of the synthesized analogs and in silico study of the obtained result revealed a potential usage of cuneane skeleton in medicinal chemistry.

Indene, indane and naphthalene in a mixture with BTEX affect aerobic compound biodegradation kinetics and indigenous microbial community development

BTEX (benzene, toluene, ethylbenzene, xylene) are common pollutants often found in former gasworks sites together with some other contaminants like indene, indane and naphthalene (Ie, Ia, N). This study aimed to evaluate the inhibitory or stimulative substrate interactions between BTEX, and Ie, Ia, N during aerobic biodegradation. For this, batch bottles, containing originally anaerobic subsurface sediments, groundwater and indigenous microorganisms from a contaminated former gasworks site, were spiked with various substrate combinations (BTEX, BTEXIe, BTEXIa, BTEXN, BTEXIeIa, BTEXIeN, BTEXIaN, BTEXIeIaN). Subsequently concentrations were monitored over time. For the BTEXIeIaN mixture, initial concentrations were between 1 and 5 mg L-1, and all compounds were completely degraded by the microbial consortia within 39 days of incubation. The experimental data were fitted to a first order kinetic degradation model for interpretation of inhibition/stimulation between the compounds. Results showed that indene, indane, and naphthalene inhibited the degradation of benzene, toluene, ethylbenzene, o-xylene, with benzene being the most affected. M/p-xylene is the only compound whose biodegradation is stimulated by the presence of indene and indane (individually or mixed) but inhibited by the presence of naphthalene. 16S rRNA amplicon sequencing revealed differentiation in the microbial communities within the batches with different substrate mixtures, especially within the two microbial groups Micrococcaceae and Commamonaceae. Indene had more effect on the BTEX microbial community than indane or naphthalene and the presence of indene increased the relative abundance of Micrococcaceae family. In conclusion, co-presence of various pollutants leads to differentiation in degradation processes as well as in microbial community development. This sheds some light on the underlying reasons for that organic compounds present in mixtures in the subsurface of former gasworks sites are either recalcitrant or subjective towards biodegradation, and this understanding helps to further improve the bioremediation of such sites.

Synthesis and Luminescent Properties of s-Tetrazine Derivatives Conjugated with the 4H-1,2,4-Triazole Ring

New derivatives obtained by the combination of unique 1,2,4,5-tetrazine and 4H-1,2,4-triazole rings have great application potential in many fields. Therefore, two synthetic few-step methodologies, which make use of commercially available 4-cyanobenzoic acid (method A) and ethyl diazoacetate (method B), were applied to produce two groups of the aforementioned heterocyclic conjugates. In both cases, the target compounds were obtained in various combinations, by introducing electron-donating or electron-withdrawing substituents into the terminal rings, together with aromatic or aliphatic substituents on the triazole nitrogen atom. Synthesis of such designed systems made it possible to analyze the influence of individual elements of the structure on the reaction course, as well as the absorption and emission properties. The structure of all products was confirmed by conventional spectroscopic methods, and their luminescent properties were also determined.

Novel 2,4-disubstituted quinazoline analogs as antibacterial agents with improved cytotoxicity profile: Modification of the benzenoid part

Bacterial resistance to currently used antibiotics demands the development of novel antibacterial agents with good safety margins and sufficient efficacy against multi-drug resistant isolates. We have previously described the synthesis of N-butyl-2-(butylthio)quinazolin-4-amine (I) as an optimized hit with broad-spectrum antibacterial activity and low cytotoxicity. In addition, we have identified a potential growing vector for this series of compounds. Herein, we describe further hit optimization which includes systematic diversifications of both the benzenoid part and the substituents at position 6 and 7 of compound I. Growing of the molecule beside the core modifications yielded several compounds with remarkable anti(myco)bacterial activity against a panel of pathogenic bacteria, including drug-resistant strains. Compound 12 showed a 2-4 fold improvement in activity than I against S. aureus Newman, S. pneumoniae DSM-20566 and E. faecalis DSM-20478. The compounds also showed a good safety profile towards human HepG2 cells.

Reperfusion mediates heme impairment with increased protein cysteine sulfonation of mitochondrial complex III in the post-ischemic heart

A serious consequence of myocardial ischemia-reperfusion injury (I/R) is oxidative damage, which causes mitochondrial dysfunction. The cascading ROS can propagate and potentially induce heme bleaching and protein cysteine sulfonation (PrSO3H) of the mitochondrial electron transport chain. Herein we studied the mechanism of I/R-mediated irreversible oxidative injury of complex III in mitochondria from rat hearts subjected to 30-min of ischemia and 24-h of reperfusion in vivo. In the I/R region, the catalytic activity of complex III was significantly impaired. Spectroscopic analysis indicated that I/R mediated the destruction of hemes b and c + c1 in the mitochondria, supporting I/R-mediated complex III impairment. However, no significant impairment of complex III activity and heme damage were observed in mitochondria from the risk region of rat hearts subjected only to 30-min ischemia, despite a decreased state 3 respiration. In the I/R mitochondria, carbamidomethylated C122/C125 of cytochrome c1 via alkylating complex III with a down regulation of HCCS was exclusively detected, supporting I/R-mediated thioether defect of heme c1. LC-MS/MS analysis showed that I/R mitochondria had intensely increased complex III PrSO3H levels at the C236 ligand of the [2Fe2S] cluster of the Rieske iron‑sulfur protein (uqcrfs1), thus impairing the electron transport activity. MS analysis also indicated increased PrSO3H of the hinge protein at C65 and of cytochrome c1 at C140 and C220, which are confined in the intermembrane space. MS analysis also showed that I/R extensively enhanced the PrSO3H of the core 1 (uqcrc1) and core 2 (uqcrc2) subunits in the matrix compartment, thus supporting the conclusion that complex III releases ROS to both sides of the inner membrane during reperfusion. Analysis of ischemic mitochondria indicated a modest reduction from the basal level of complex III PrSO3H detected in the mitochondria of sham control hearts, suggesting that the physiologic hyperoxygenation and ROS overproduction during reperfusion mediated the enhancement of complex III PrSO3H. In conclusion, reperfusion-mediated heme damage with increased PrSO3H controls oxidative injury to complex III and aggravates mitochondrial dysfunction in the post-ischemic heart.

Effects of Substitution on Cytotoxicity of Diphenyl Ditelluride in Cultured Vascular Endothelial Cells

Among organic–inorganic hybrid molecules consisting of organic structure(s) and metal(s), only few studies are available on the cytotoxicity of nucleophilic molecules. In the present study, we investigated the cytotoxicity of a nucleophilic organotellurium compound, diphenyl ditelluride (DPDTe), using a cell culture system. DPDTe exhibited strong cytotoxicity against vascular endothelial cells and fibroblasts along with high intracellular accumulation but showed no cytotoxicity and had less accumulation in vascular smooth muscle cells and renal epithelial cells. The cytotoxicity of DPDTe decreased when intramolecular tellurium atoms were replaced with selenium or sulfur atoms. Electronic state analysis revealed that the electron density between tellurium atoms in DPDTe was much lower than those between selenium atoms of diphenyl diselenide and sulfur atoms of diphenyl disulfide. Moreover, diphenyl telluride did not accumulate and exhibit cytotoxicity. The cytotoxicity of DPDTe was also affected by substitution. p-Dimethoxy-DPDTe showed higher cytotoxicity, but p-dichloro-DPDTe and p-methyl-DPDTe showed lower cytotoxicity than that of DPDTe. The subcellular distribution of the compounds revealed that the compounds with stronger cytotoxicity showed higher accumulation rates in the mitochondria. Our findings suggest that the electronic state of tellurium atoms in DPDTe play an important role in accumulation and distribution of DPDTe in cultured cells. The present study supports the hypothesis that nucleophilic organometallic compounds, as well as electrophilic organometallic compounds, exhibit cytotoxicity by particular mechanisms.

Dihydroisocoumarins and Dihydroisoflavones from the Rhizomes of Dioscorea collettii with Cytotoxic Activity and Structural Revision of 2,2'-Oxybis(1,4-di-tert-butylbenzene)

The investigation of the constituents of the rhizomes of Dioscorea collettii afforded one new dihydroisocoumarin, named (−)-montroumarin (1a), along with five known compounds—montroumarin (1b), 1,1′-oxybis(2,4-di-tert-butylbenzene) (2), (3R)-3′-O-methylviolanone (3a), (3S)-3′-O-methylviolanone (3b), and (RS)-sativanone (4). Their structures were elucidated using extensive spectroscopic methods. To the best of our knowledge, compound 1a is a new enantiomer of compound 1b. The NMR data of compound 2 had been reported but its structure was erroneous. The structure of compound 2 was revised on the basis of a reinterpretation of its NMR data (1D and 2D) and the assignment of the ¹H and ¹³C NMR data was given rightly for the first time. Compounds 3a–4, three dihydroisoflavones, were reported from the Dioscoreaceae family for the first time. The cytotoxic activities of all the compounds were tested against the NCI-H460 cell line. Two dihydroisocoumarins, compounds 1a and 1b, displayed moderate cytotoxic activities, while the other compounds showed no cytotoxicity.

Selective Photoswitchable Allosteric Agonist of a G Protein-Coupled Receptor

G protein-coupled receptors (GPCRs) are the most common targets of drug discovery. However, the similarity between related GPCRs combined with the complex spatiotemporal dynamics of receptor activation in vivo has hindered drug development. Photopharmacology offers the possibility of using light to control the location and timing of drug action by incorporating a photoisomerizable azobenzene into a GPCR ligand, enabling rapid and reversible switching between an inactive and active configuration. Recent advances in this area include (i) photoagonists and photoantagonists that directly control receptor activity but are nonselective because they bind conserved sites, and (ii) photoallosteric modulators that bind selectively to nonconserved sites but indirectly control receptor activity by modulating the response to endogenous ligand. In this study, we designed a photoswitchable allosteric agonist that targets a nonconserved allosteric site for selectivity and activates the receptor on its own to provide direct control. This work culminated in the development of aBINA, a photoswitchable allosteric agonist that selectively activates the Gi/o-coupled metabotropic glutamate receptor 2 (mGluR2). aBINA is the first example of a new class of precision drugs for GPCRs and other clinically important signaling proteins.

A platform for on-the-complex annulation reactions with transient aryne intermediates

Organometallic complexes are ubiquitous in chemistry and biology. Whereas their preparation has historically relied on ligand synthesis followed by coordination to metal centers, the ability to efficiently diversify their structures remains a synthetic challenge. A promising yet underdeveloped strategy involves the direct manipulation of ligands that are already bound to a metal center, also known as chemistry-on-the-complex. Herein, we introduce a versatile platform for on-the-complex annulation reactions using transient aryne intermediates. In one variant, organometallic complexes undergo transition metal-catalyzed annulations with in situ generated arynes to form up to six new carbon-carbon bonds. In the other variant, an organometallic complex bearing a free aryne is generated and intercepted in cycloaddition reactions to access unique scaffolds. Our studies, centered around privileged polypyridyl metal complexes, provide an effective strategy to annulate organometallic complexes and access complex metal-ligand scaffolds, while furthering the synthetic utility of strained intermediates in chemical synthesis.

Density Functional Theory and Molecular Docking Investigations of the Chemical and Antibacterial Activities for 1-(4-Hydroxyphenyl)-3-phenylprop-2-en-1-one

The present investigation informs a descriptive study of 1-(4-Hydroxyphenyl) -3-phenylprop-2-en-1-one compound, by using density functional theory at B3LYP method with 6-311G** basis set. The oxygen atoms and π-system revealed a high chemical reactivity for the title compound as electron donor spots and active sites for an electrophilic attack. Quantum chemical parameters such as hardness (η), softness (S), electronegativity (χ), and electrophilicity (ω) were yielded as descriptors for the molecule’s chemical behavior. The optimized molecular structure was obtained, and the experimental data were matched with geometrical analysis values describing the molecule’s stable structure. The computed FT-IR and Raman vibrational frequencies were in good agreement with those observed experimentally. In a molecular docking study, the inhibitory potential of the studied molecule was evaluated against the penicillin-binding proteins of Staphylococcus aureus bacteria. The carbonyl group in the molecule was shown to play a significant role in antibacterial activity, four bonds were formed by the carbonyl group with the key protein of the bacteria (three favorable hydrogen bonds plus one van der Waals bond) out of six interactions. The strong antibacterial activity was also indicated by the calculated high binding energy (−7.40 kcal/mol).

A peroxisomal β-oxidative pathway contributes to the formation of C6-C1 aromatic volatiles in poplar

Benzenoids (C6-C1 aromatic compounds) play important roles in plant defense and are often produced upon herbivory. Black cottonwood (Populus trichocarpa) produces a variety of volatile and nonvolatile benzenoids involved in various defense responses. However, their biosynthesis in poplar is mainly unresolved. We showed feeding of the poplar leaf beetle (Chrysomela populi) on P. trichocarpa leaves led to increased emission of the benzenoid volatiles benzaldehyde, benzylalcohol, and benzyl benzoate. The accumulation of salicinoids, a group of nonvolatile phenolic defense glycosides composed in part of benzenoid units, was hardly affected by beetle herbivory. In planta labeling experiments revealed that volatile and nonvolatile poplar benzenoids are produced from cinnamic acid (C6-C3). The biosynthesis of C6-C1 aromatic compounds from cinnamic acid has been described in petunia (Petunia hybrida) flowers where the pathway includes a peroxisomal-localized chain shortening sequence, involving cinnamate-CoA ligase (CNL), cinnamoyl-CoA hydratase/dehydrogenase (CHD), and 3-ketoacyl-CoA thiolase (KAT). Sequence and phylogenetic analysis enabled the identification of small CNL, CHD, and KAT gene families in P. trichocarpa. Heterologous expression of the candidate genes in Escherichia coli and characterization of purified proteins in vitro revealed enzymatic activities similar to those described in petunia flowers. RNA interference-mediated knockdown of the CNL subfamily in gray poplar (Populus x canescens) resulted in decreased emission of C6-C1 aromatic volatiles upon herbivory, while constitutively accumulating salicinoids were not affected. This indicates the peroxisomal β-oxidative pathway participates in the formation of volatile benzenoids. The chain shortening steps for salicinoids, however, likely employ an alternative pathway.

Chromoselective Photocatalysis Enables Stereocomplementary Biocatalytic Pathways*

Controlling the selectivity of a chemical reaction with external stimuli is common in thermal processes, but rare in visible-light photocatalysis. Here we show that the redox potential of a carbon nitride photocatalyst (CN-OA-m) can be tuned by changing the irradiation wavelength to generate electron holes with different oxidation potentials. This tuning was the key to realizing photo-chemo-enzymatic cascades that give either the (S)- or the (R)-enantiomer of phenylethanol. In combination with an unspecific peroxygenase from Agrocybe aegerita, green light irradiation of CN-OA-m led to the enantioselective hydroxylation of ethylbenzene to (R)-1-phenylethanol (99 % ee). In contrast, blue light irradiation triggered the photocatalytic oxidation of ethylbenzene to acetophenone, which in turn was enantioselectively reduced with an alcohol dehydrogenase from Rhodococcus ruber to form (S)-1-phenylethanol (93 % ee).

Hexadehydro-Diels-Alder Reaction: Benzyne Generation via Cycloisomerization of Tethered Triynes

The hexadehydro-Diels-Alder (HDDA) reaction is the thermal cyclization of an alkyne and a 1,3-diyne to generate a benzyne intermediate. This is then rapidly trapped, in situ, by a variety of species to yield highly functionalized benzenoid products. In contrast to nearly all other methods of aryne generation, no other reagents are required to produce an HDDA benzyne. The versatile and customizable nature of the process has attracted much attention due not only to its synthetic potential but also because of the fundamental mechanistic insights the studies often afford. The authors have attempted to provide here a comprehensive compilation of publications appearing by mid-2020 that describe experimental results of HDDA reactions.

PEG-Coated Large Mesoporous Silicas as Smart Platform for Protein Delivery and Their Use in a Collagen-Based Formulation for 3D Printing

Silica-based mesoporous systems have gained great interest in drug delivery applications due to their excellent biocompatibility and high loading capability. However, these materials face challenges in terms of pore-size limitations since they are characterized by nanopores ranging between 6-8 nm and thus unsuitable to host large molecular weight molecules such as proteins, enzymes and growth factors (GFs). In this work, for an application in the field of bone regeneration, large-pore mesoporous silicas (LPMSs) were developed to vehicle large biomolecules and release them under a pH stimulus. Considering bone remodeling, the proposed pH-triggered mechanism aims to mimic the release of GFs encased in the bone matrix due to bone resorption by osteoclasts (OCs) and the associated pH drop. To this aim, LPMSs were prepared by using 1,3,5-trimethyl benzene (TMB) as a swelling agent and the synthesis solution was hydrothermally treated and the influence of different process temperatures and durations on the resulting mesostructure was investigated. The synthesized particles exhibited a cage-like mesoporous structure with accessible pores of diameter up to 23 nm. LPMSs produced at 140 °C for 24 h showed the best compromise in terms of specific surface area, pores size and shape and hence, were selected for further experiments. Horseradish peroxidase (HRP) was used as model protein to evaluate the ability of the LPMSs to adsorb and release large biomolecules. After HRP-loading, LPMSs were coated with a pH-responsive polymer, poly(ethylene glycol) (PEG), allowing the release of the incorporated biomolecules in response to a pH decrease, in an attempt to mimic GFs release in bone under the acidic pH generated by the resorption activity of OCs. The reported results proved that PEG-coated carriers released HRP more quickly in an acidic environment, due to the protonation of PEG at low pH that catalyzes polymer hydrolysis reaction. Our findings indicate that LPMSs could be used as carriers to deliver large biomolecules and prove the effectiveness of PEG as pH-responsive coating. Finally, as proof of concept, a collagen-based suspension was obtained by incorporating PEG-coated LPMS carriers into a type I collagen matrix with the aim of designing a hybrid formulation for 3D-printing of bone scaffolds.

Synthesis of Polyfluorinated Thia- and Oxathiacalixarenes Based on Perfluoro-m-xylene

Perfluorinated tetrathiacalix[4]arene was obtained by heating perfluoro-m-xylene with thiourea or 2,5-difluoro-4,6-bis(trifluoromethyl)benzene-1,3-dithiol at 90 °C. Interaction of perfluoro-m-xylene with resorcinol or orcinol under mild conditions and subsequent heating of the mixture with 2,5-difluoro-4,6-bis(trifluoromethyl)benzene-1,3-dithiol leads to polyfluorinated dioxadithiacalix[4]arenes. Triphenyl and pentaphenyl ethers formed by the interaction of perfluoro-m-xylene with resorcinol under heating with thiourea gives polyfluorinated oxathiacalixarenes containing six and five aromatic nuclei, respectively.

Effects of inhaled combined Benzene, Toluene, Ethylbenzene, and Xylenes (BTEX): Toward an environmental exposure model

Combined environmental exposures to the volatile organic compounds (VOCs) Benzene, Toluene, Ethylbenzene, and Xylene (BTEX) pose clear risks to public health. Research into these risks is under-studied even as BTEX levels in the atmosphere are predicted to rise. This review focuses on the available literature using single- and combined-BTEX component inhaled solvent exposures in animal models, necessarily also drawing on findings from models of inhalant abuse and occupational exposures. Health effects of these exposures are discussed for multiple organ systems, but with particular attention on neurobehavioral outcomes such as locomotor activity, impulsivity, learning, and psychopharmacological responses. It is clear that animal models have significant differences in the concentrations, durations and patterns of exposure. Experimental evidence of the deleterious health and neurobehavioral consequences of exposures to the individual components of BTEX were found, but these effects were typically assessed using concentrations and exposure patterns not characteristic of environmental exposure. Future studies with animal models designed appropriately to explore combined BTEX will be necessary and advantageous to discovering health outcomes and more subtle neurobehavioral impacts of long-term environmental exposures.

Amycolasporins and Dibenzoyls from Lichen-Associated Amycolatopsis hippodromi and Their Antibacterial and Anti-inflammatory Activities

Eleven metabolites, six echinosporins (1-6), four dibenzoyls (7-10), and an aromatic compound (11), were isolated from the fermentation broth of lichen-associated Amycolatopsis hippodromi. The structures of the new compounds (1-5, 8-11) were elucidated by comprehensive spectroscopic analysis including data from experimental and calculated ECD spectra. Amycolasporins A-C (1-3) demonstrated antibacterial activities against Bacillus subtilis, Staphylococcus aureus, and Escherichia coli with MIC values of 25 or 100 μg/mL. Amycolasporin C (3) and the known dibenzoyl (7) attenuated the production of NO due to the suppression of the expression of nitric oxide synthase (iNOS) in LPS-induced RAW 264.7 cells in a dose-dependent manner.

Selective N1/N4 1,4-Cycloaddition of 1,2,4,5-Tetrazines Enabled by Solvent Hydrogen Bonding

An unprecedented 1,4-cycloaddition (vs 3,6-cycloaddition) of 1,2,4,5-tetrazines is described with preformed or in situ generated aryl-conjugated enamines promoted by the solvent hydrogen bonding of hexafluoroisopropanol (HFIP) that is conducted under mild reaction conditions (0.1 M HFIP, 25 °C, 12 h). The reaction constitutes a formal [4 + 2] cycloaddition across the two nitrogen atoms (N1/N4) of the 1,2,4,5-tetrazine followed by a formal retro [4 + 2] cycloaddition loss of a nitrile and aromatization to generate a 1,2,4-triazine derivative. The factors that impact the remarkable change in the reaction mode, optimization of reaction parameters, the scope and simplification of its implementation through in situ enamine generation from aldehydes and ketones, the reaction scope for 3,6-bis(thiomethyl)-1,2,4,5-tetrazine, a survey of participating 1,2,4,5-tetrazines, and key mechanistic insights into this reaction are detailed. Given its simplicity and breath, the study establishes a novel method for the simple and efficient one-step synthesis of 1,2,4-triazines under mild conditions from readily accessible starting materials. Whereas alternative protic solvents (e.g., MeOH vs HFIP) provide products of the conventional 3,6-cycoladdition, the enhanced hydrogen bonding capability of HFIP uniquely results in promotion of the unprecedented formal 1,4-cycloaddition. As such, the studies represent an example of not just an enhancement in the rate or efficiency of a heterocyclic azadiene cycloaddition by hydrogen bonding catalysis but also the first to alter the mode (N1/N4 vs C3/C6) of cycloaddition.

Synthesis of Organosilicon Ligands for Europium (III) and Gadolinium (III) as Potential Imaging Agents

The relaxivity of MRI contrast agents can be increased by increasing the size of the contrast agent and by increasing concentration of the bound gadolinium. Large multi-site ligands able to coordinate several metal centres show increased relaxivity as a result. In this paper, an “aza-type Michael” reaction is used to prepare cyclen derivatives that can be attached to organosilicon frameworks via hydrosilylation reactions. A range of organosilicon frameworks were tested including silsesquioxane cages and dimethylsilylbenzene derivatives. Michael donors with strong electron withdrawing groups could be used to alkylate cyclen on three amine centres in a single step. Hydrosilylation successfully attached these to mono-, di-, and tri-dimethylsilyl-substituted benzene derivatives. The europium and gadolinium complexes were formed and studied using luminescence spectroscopy and relaxometry. This showed the complexes to contain two bound water moles per lanthanide centre and T₁ relaxation time measurements demonstrated an increase in relaxivity had been achieved, in particular for the trisubstituted scaffold 1,3,5-tris((pentane-sDO3A)dimethylsilyl)benzene-Gd₃. This showed a marked increase in the relaxivity (13.1 r_1p/mM⁻¹s⁻¹).

Bonding Analysis of Compounds with Unusual Coordination of Carbon: Proposed Symmetric Systems with Six-Coordinate Carbon

The possibility of carbon tetravalence in geometries other than tetrahedral and of carbon hypervalence has been taken seriously since the 1970s. Computational modeling and subsequent experimental validation have established the existence of molecules with carbon atoms with planar tetravalence and as many as six objects in carbon’s coordination sphere. In this work, we develop insight into the nature of bonding to carbon in these unusual environs as provided by Bader’s Atoms in Molecules (AIM) analysis of the electron density, along with the electron localization function (ELF) and the non-covalent index (NCI). We review several well-established systems (spiropentadiene dication, hexamethyl benzene dication, dimethanospiro[2.2]octaplane dication, and 1,8-dimethoxy-9-dimethoxyanthracene cation) and propose new D2d–symmetric variants of a hexacoordinated species.

New synthetic chitosan derivatives bearing benzenoid/heterocyclic moieties with enhanced antioxidant and antifungal activities

In this paper, several novel chitosan derivatives bearing benzenoid / heterocyclic moieties were synthesized via introducing aminobenzene and heterocyclic compounds onto carboxymethyl chitosan. The specific structures of chitosan derivatives were confirmed by FTIR, ¹H NMR, and elemental analysis. Meanwhile, the antioxidant efficiencies of chitosan derivatives were assayed in vitro. In particular, all chitosan derivatives showed significant improvement in superoxide-radical scavenging activity and DPPH radical scavenging activity. Their antifungal activities against two plant pathogenic fungi (Colletotrichum lagenarium and Phomopsis asparagi) were estimated in vitro by hyphal measurement, and all products exhibited excellent antifungal activity. Besides, the cytotoxicity of them was also measured by CCK-8 in vitro on L929 cells, and all samples showed low cytotoxicity. The good biocompatibility and enhanced biological activity of new synthetic chitosan derivatives might be obvious advantages, while applied in wide range of applications as antifungal agents or antioxidants in food, medicine, cosmetics, and other fields.

Properly Substituted Cyclic Bis-(2-bromobenzylidene) Compounds Behaved as Dual p300/CARM1 Inhibitors and Induced Apoptosis in Cancer Cells

Bis-(3-bromo-4-hydroxy)benzylidene cyclic compounds have been reported by us as epigenetic multiple ligands, but different substitutions at the two wings provided analogues with selective inhibition. Since the 1-benzyl-3,5-bis((E)-3-bromobenzylidene)piperidin-4-one 3 displayed dual p300/EZH2 inhibition joined to cancer-selective cell death in a panel of tumor cells and in in vivo xenograft models, we prepared a series of bis((E)-2-bromobenzylidene) cyclic compounds 4a–n to test in biochemical (p300, PCAF, SIRT1/2, EZH2, and CARM1) and cellular (NB4, U937, MCF-7, SH-SY5Y) assays. The majority of 4a–n exhibited potent dual p300 and CARM1 inhibition, sometimes reaching the submicromolar level, and induction of apoptosis mainly in the tested leukemia cell lines. The most effective compounds in both enzyme and cellular assays carried a 4-piperidone moiety and a methyl (4d), benzyl (4e), or acyl (4k–m) substituent at N1 position. Elongation of the benzyl portion to 2-phenylethyl (4f) and 3-phenylpropyl (4g) decreased the potency of compounds at both the enzymatic and cellular levels, but the activity was promptly restored by introduction of a ketone group into the phenylalkyl substituent (4h–j). Western blot analyses performed in NB4 and MCF-7 cells on selected compounds confirmed their inhibition of p300 and CARM1 through decrease of the levels of acetyl-H3 and acetyl-H4, marks for p300 inhibition, and of H3R17me2, mark for CARM1 inhibition.

Identifying alternative solvents for C60 manufacturing using singular and combined toxicity assessments

Linseed oil, olive oil, and sunflower oil were selected based on green chemistry principles and C₆₀ solubility as alternative solvents to replace 1,2,4-trimethylbenzene (TMB) for C₆₀ manufacturing. Singular acute toxicity experiments of C₆₀ and the four solvents was performed using Daphnia magna to identify the solvent with the lowest toxicity and estimate the toxicity of C₆₀. The EC₅₀ for C₆₀ was estimated to be higher than 176 ppm. The toxicity of the solvents increased from sunflower oil to olive oil, linseed oil, and TMB. Combined toxicity tests were conducted to investigate the interaction between C₆₀ and the solvent since essential oils can be nanocarriers and facilitate the transport of C₆₀ into the cell membranes, which would increase its toxicity. Various concentrations of C₆₀ (0, 11, 22, 44, 88, and 176 mg/L) were mixed with solvents at their EC₅₀ concentrations. The toxicity of linseed oil increased with increasing C₆₀ concentrations. For olive and sunflower oil, the toxicity was lowered with low concentrations of C₆₀. Olive oil was determined to be a suitable solvent for C₆₀ manufacturing based on singular and combined toxicity assessments. This study showed the importance of considering combined toxicity for solvent selection.