A Benzil- and BODIPY-Based Turn-On Fluorescent Probe for Detection of Hydrogen Peroxide.

Faced with rising threats of terrorism, environmental and health risks, achieving sensitive and selective detection of peroxide-based explosives (PEs) has become a global focus. In this study, a turn-on fluorescent probe (BOD) based on benzil (H2O2-recognition element) and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) derivative (fluorophore) was developed to sensitively and specifically detect hydrogen peroxide (H2O2). The synthesized BOD had a very weak fluorescence due to intramolecular donor-excited photo-induced electron transfer (d-PET) effect; however, it could emit a strong fluorescence since H2O2 selectively oxidized the benzil moiety and released free BODIPY fluorophore (BOD-COOH). As a result, the proposed BOD detected H2O2 in linear detection ranged from 25 to 125 µM with a detection limit of 4.41 µM. Meanwhile, the proposed BOD showed good selectivity toward H2O2, which is not affected by other common reactive oxygen species (ROS) and ions from explosive residues. In addition, a blue shift from 508 to 498 nm was observed in the absorption spectra upon addition of H2O2. More importantly, the BOD was successfully applied for rapid detection of H2O2 vapor with good sensitivity (down to 7 ppb), which holds great potential for practical use in public safety, forensic analysis and environmental monitoring.

Catalyst-free [2 + 2] photocycloadditions between benzils and olefins under visible light.

The catalyst-free [2 + 2] photocycloaddition between benzils and simple olefins is reported. The adoption of visible light proved essential for the transformation, as shorter wavelengths led to uncontrolled decomposition. When cyclic olefins were used, the reaction occurred smoothly to afford the expected oxetanes regio- and stereoselectively after 24 h of irradiation. In contrast, in the case of acyclic olefins, longer reaction times were typically required and small amounts (ca. 20%) of [4 + 2] photocycloadducts and by-products deriving from competitive hydrogen atom abstraction were observed. The selectivity of the transformation could be consistently improved by decreasing the reaction temperature, thus restoring the desired [2 + 2] reactivity. An overall mechanistic picture is also offered based on the chemical and photophysical quenching experiments and the stereochemical output is rationalized based on Griesbeck models.

New Benzil and Isoflavone Derivatives with Cytotoxic and NO Production Inhibitory Activities from Placolobium vietnamense.

The phytochemical investigation of Placolobium vietnamense stems led to the isolation of a new isoflavone derivative (1) and three new benzil derivatives (2-4), together with four known pyranoisoflavones (5-8). The structures of all isolated compounds were determined on the basis of extensive spectroscopic analyses, including NMR and HRMS spectral data, as well as comparison of their spectroscopic data with those reported in the literature. The cytotoxicity of all isolated compounds was assessed against the human liver hepatocellular carcinoma (Hep G2) cell line, and compound 1 displayed the most significant cytotoxicity with an IC50 value of 8.0 µM. Furthermore, all isolated compounds were also tested for their inhibitory activity against NO production in RAW 264.7 macrophages. Of these, compound 1 exhibited the strongest inhibitory efficacy against the LPS-induced NO production with the IC50 value of 13.7 µM.

Synthesis, biological evaluation (antioxidant, antimicrobial, enzyme inhibition, and cytotoxic) and molecular docking study of hydroxy methoxy benzoin/benzil analogous.

In this work, due to the biological activity evaluation, a series of hydroxy methoxy benzoins (1-8), benzils (10-16) and methoxy benzoin/benzil-O-ß-d-glucosides (17-28) were synthesized. Antioxidant (FRAP, CUPRAC, DPPH), antimicrobial (16 microorganisms, and two yeast), enzyme inhibition (α-amylase, α-glucosidase, AChE, BChE, and tyrosinase) of all synthesized benzoin/benzil analogs were investigated. Benzoins (1-8) showed the most effective antioxidant properties compared to all three methods. Compound 28 against α-amylase, compound 9 against α-glucosidase, compound 11 against AChE, compound 2 against BChE, and compound 13 against tyrosinase showed the best activities with the better or similar IC50 values as used standards. Hydroxy methoxy benzoin compounds (1-8) among all four groups were seen as the most effective against the tested microorganism. Molecular docking analysis showed that all tested compounds 1-28 (0.01-2.22 µM) had the best binding affinity against AChE enzyme. Cytotoxic effects of the many of compounds (1-16, 21, and 24) also investigated and it was found that they caused different effects in different cells. The LDH tests of compounds 1a + b, 4, 7, 8, 9, 11, 12, 21, and 24, seemed to be effective compared to the positive control cisplatin. The cytotoxicity of compounds 6 (9.24%) for MCF7 cancer cells, 8 (5.16%) and 4 (8.26%) for HT29 cancer cells, 24 (9.84%) for Hep3B cells and 8 (8.52%), 7 (5.70%), 4 (6.94) and 9 (7.22%) for C6 cells were at normal values. And also cytotoxic activity of four compounds (5, 9, 21, and 24) among the all synthetic groups, were evaluated to the HeLa and RPE. Compound 5 showed anticancer activity on HeLa and RPE cancer cells as much as or better than cisplatin which was used as standard.

Microbial Synthesis of (S)- and (R)-Benzoin in Enantioselective Desymmetrization and Deracemization Catalyzed by Aureobasidium pullulans Included in the Blossom Protect™ Agent.

In this study, we examined the Aureobasidium pullulans strains DSM 14940 and DSM 14941 included in the Blossom Protect™ agent to be used in the bioreduction reaction of a symmetrical dicarbonyl compound. Both chiral 2-hydroxy-1,2-diphenylethanone antipodes were obtained with a high enantiomeric purity. Mild conditions (phosphate buffer [pH 7.0, 7.2], 30 °C) were successfully employed in the synthesis of (S)-benzoin using two different methodologies: benzyl desymmetrization and rac-benzoin deracemization. Bioreduction carried out with higher reagent concentrations, lower pH values and prolonged reaction time, and in the presence of additives, enabled enrichment of the reaction mixture with (R)-benzoin. The described procedure is a potentially useful tool in the synthesis of chiral building blocks with a defined configuration in a simple and economical process with a lower environmental impact, enabling one-pot biotransformation.

Chiral Benzoins via Asymmetric Transfer Hemihydrogenation of Benzils: The Detail that Matters.

The synthesis of enantiomerically pure benzoins by hydrogenation of readily available benzils has been long thwarted by their base-sensitivity. We show here that an iron(II) hydride complex catalyzes the asymmetric transfer hydrogenation of benzils from 2-propanol. When strictly base-free conditions are granted, excellent enantioselectivity is achieved even with o-substituted substrates, which are particularly challenging to prepare with other methods. Hence, under optimized reaction conditions, chiral benzoins were prepared in good yields (up to 83%) and excellent enantioselectivity (up to 98% ee) in short reaction times (30-75 min). Also, this work confirms that both enantiomers of the benzoin products can be accessed when a metal catalyst is used, which is a clear advantage over enzymatic methods.

H2O2-responsive polymeric micelles with a benzil moiety for efficient DOX delivery and AIE imaging.

Nano drug delivery is a promising domain in biomedical theranostics and has aroused more and more attention in recent years. We report here an amphiphilic polymer TPG1, bearing a H2O2-sensitive benzil and an AIE fluorophore tetraphenylethene (TPE) unit, which is able to self-assemble into spherical nanosized micelles in aqueous solution. Doxorubicin (DOX) can be encapsulated into TPG1 micelles efficiently with the loading capability of up to 59% by weight. The benzil moiety could be cleaved via the Baeyer-Villiger type reaction in the presence of H2O2, leading to the decomposition of TPG1 micelles and release of DOX. In vitro studies indicated that DOX-loaded TPG1 micelles can be internalized by cancer cells, followed by unloading encapsulated DOX under the stimulation of H2O2. The drug release process can be monitored by the AIE fluorescence from the degradation products containing a TPE moiety. MTT assays against HeLa and HepG2 cancer cells demonstrated that DOX-loaded micelles showed good anticancer efficacy. The polymer TPG1 and the corresponding decomposed products showed great biocompatibility. Our data suggest that TPG1 has the potential to be employed for the controlled drug delivery system.

Arginine-selective bioconjugation with 4-azidophenyl glyoxal: application to the single and dual functionalisation of native antibodies.

Here, we introduce 4-azidophenyl glyoxal (APG) as an efficient plug-and-play reagent for the selective functionalisation of arginine residues in native antibodies. The selective reaction between APG and arginines' guanidine groups allowed a facile introduction of azide groups on the monoclonal antibody trastuzumab (plug stage). These pre-functionalised antibody-azide conjugates were then derivatised during the "play stage" via a biorthogonal cycloaddition reaction with different strained alkynes. This afforded antibody-fluorophore and antibody-oligonucleotide conjugates, all showing preserved antigen selectivity and high stability in human plasma. Due to a lower content of arginines compared to lysines in native antibodies, this approach is thus attractive for the preparation of more homogeneous conjugates. This method proved to be orthogonal to classical lysine-based conjugation and allowed straightforward generation of dual-payload antibody.

Synthesis of benzil-o-carboxylate derivatives and isocoumarins through neighboring ester-participating bromocyclizations of o-alkynylbenzoates.

Bromide mediated neighboring ester-participating bromocyclizations of o-alkynylbenzoates are described here for the synthesis of benzil-o-carboxylates. 4-bromoisocoumarins are also synthesized when phenyl o-alkynylbenzoate is used as the substrate. Mechanistic studies suggest that the whole process is composed of an electrophilic bromocyclization and a dibromohydration-based ring-opening, and the neighboring ester group participates in the bromocyclization. Interestingly, the two oxygen atoms of the keto carbonyls in benzil-o-carboxylates are both derived from water. The electrophilic bromo source is in situ generated from the oxidation of bromide.

One-pot synthesis of a new 2-substituted 1,2,3-triazole 1-oxide derivative from dipyridyl ketone and isonitrosoacetophenone hydrazone: Nickel(II) complex, DNA binding and cleavage properties.

An efficient and simple one-pot synthesis of a new 1,2,3-triazole-1-oxide via reaction between isonitrosoacetophenone hydrazone and dipyridyl ketone in the EtOH/AcOH at room temperature has been developed smoothly in high yield. The reaction proceeds via metal salt free, in-situ formation of asymmetric azine followed by cyclization to provide 1,2,3-triazole 1-oxide compound. It has been structurally characterized. The 1:1 ratio reaction of the 1,2,3-triazole 1-oxide ligand with nickel(II) chloride gives the mononuclear complex [Ni(L)(DMF)Cl2], hexa-coordinated within an octahedral geometry. Characterization of the 1,2,3-triazole compound and its Ni(II) complex with FTIR, 1H and 13C NMR, UV-vis and elemental analysis also confirms the proposed structures of the compounds. The interactions of the compounds with Calf thymus DNA (CT-DNA) have been investigated by UV-visible spectra and viscosity measurements. The results suggested that both ligand and Ni(II) complex bind to DNA in electrostatic interaction and/or groove binding, also with a slight partial intercalation in the case of ligand. DNA cleavage experiments have been also investigated by agarose gel electrophoresis in the presence and absence of an oxidative agent (H2O2). Both 1,2,3-triazole 1-oxide ligand and its nickel(II) complex show nuclease activity in the presence of hydrogen peroxide. DNA binding and cleavage affinities of the 1,2,3-triazole 1-oxide ligand is stronger than that of the Ni(II) complex.

Biotransformation Capacity of Carboxylesterase in Skin and Keratinocytes for the Penta-Ethyl Ester Prodrug of DTPA.

The penta-ethyl ester prodrug of the chelating agent diethylene triamine pentaacetic acid (DTPA), referred to as C2E5, effectively accelerated clearance of americium after transdermal delivery. Carboxylesterases (CESs) play important roles in facilitating C2E5 hydrolysis. However, whether CESs in human skin hydrolyze C2E5 remains unknown. We evaluated the gene and protein expression of CESs in distinctive human epidermal cell lines: HEKa, HEKn, HaCaT, and A431. The substrates p-nitrophenyl acetate (pNPA) and 4-nitrophenyl valerate (4-NPV) were used to access esterase and CES activity. C2E5 hydrolysis was measured by radiometric high-performance liquid chromatography after incubation of [(14)C]C2E5 with supernatant fractions after centrifugation at 9000g (S9) prepared from skin cell lines. CES-specific inhibitors were used to access metabolism in human skin S9 fractions with analysis by liquid chromatography-tandem mass spectrometry. We identified the human carboxylesterase 1 and 2 (CES1 and CES2) bands in a Western blot. The gene expression of these enzymes was supported by a real-time polymerase chain reaction (qPCR). pNPA and 4-NPV assays demonstrated esterase and CES activity in all the cell lines that were comparable to human skin S9 fractions. The prodrug C2E5 was hydrolyzed by skin S9 fractions, resulting in a primary metabolite, C2E4. In human skin S9 fractions, inhibition of C2E5 hydrolysis was greatest with a pan-CES inhibitor (benzil). CES1 inhibition (troglitazone) was greater than CES2 (loperamide), suggesting a primary metabolic role for CES1. These results indicate that human keratinocyte cell lines are useful for the evaluation of human cutaneous metabolism and absorption of ester-based prodrugs. However, keratinocytes from skin provide a small contribution to the overall metabolism of C2E5.

Design, synthesis, characterization and antimicrobial/antioxidant activities of 1, 4-dicarbonyl-phenyl-dihydrazide based macrocyclic ligand and its Cu(II), Co(II) and Ni(II) complexes.

Mononuclear transition metal complexes of Cu(II), Co(II) and Ni(II) with a newly synthesised macrocyclic ligand derived from 1, 4-dicarbonyl-phenyl-dihydrazide and 1,2-diphenylethane-1,2-dione (2:2) have been synthesised. The synthesised compounds were characterised by various physical and spectroscopic techniques including elemental analysis, FTIR, Uv-Vis., 1H NMR, mass spectra, magnetic moment and XRD. The investigation of these macrocyclic complexes established that the stability of metal-ligand coordination through N atoms as tetradentate chelates. The metal/ligands ratio of 1:1 was proposed to afford octahedral geometry for the complexes. The antimicrobial activity of the compounds against some bacterial and fungal species were done by well diffusion method and the results shows that the metal complexes have a promising biological activity comparable with the parent ligand against all bacterial and fungal species. The antioxidant activity of the compounds was also studied through scavenging effect on DPPH radicals with the copper complex showing enhanced activity than other compounds. Additionally, the docking studies predicted the high antimicrobial activity due to the interaction of ligand with the protein.

Synthesis, crystal structures and spectroscopic properties of triazine-based hydrazone derivatives; a comparative experimental-theoretical study.

We report here a comparative theoretical and experimental study of four triazine-based hydrazone derivatives. The hydrazones are synthesized by a three step process from commercially available benzil and thiosemicarbazide. The structures of all compounds were determined by using the UV-Vis., FT-IR, NMR (1H and 13C) spectroscopic techniques and finally confirmed unequivocally by single crystal X-ray diffraction analysis. Experimental geometric parameters and spectroscopic properties of the triazine based hydrazones are compared with those obtained from density functional theory (DFT) studies. The model developed here comprises of geometry optimization at B3LYP/6-31G (d, p) level of DFT. Optimized geometric parameters of all four compounds showed excellent correlations with the results obtained from X-ray diffraction studies. The vibrational spectra show nice correlations with the experimental IR spectra. Moreover, the simulated absorption spectra also agree well with experimental results (within 10-20 nm). The molecular electrostatic potential (MEP) mapped over the entire stabilized geometries of the compounds indicated their chemical reactivates. Furthermore, frontier molecular orbital (electronic properties) and first hyperpolarizability (nonlinear optical response) were also computed at the B3LYP/6-31G (d, p) level of theory.

Self-assembly of Metallamacrocycles Employing a New Benzil-based Organometallic Bisplatinum(II) Acceptor.

A benzil-based semi-rigid dinuclear-organometallic acceptor 4,4'-bis[trans-Pt(PEt(3))(2)(NO(3))(ethynyl)]benzil (bisPt-NO(3)) containing a Pt-ethynyl functionality was synthesized in good yield and characterized by multinuclear NMR ((1)H, (31)P, and (13)C), electrospray ionization mass spectrometry (ESI-MS), and single-crystal X-ray diffraction analysis of the iodide analogue bisPt-I. The stoichiometric (1:1) combination of the acceptor bisPt-NO(3) separately with four different ditopic donors (L(1)-L(4); L(1) = 9-ethyl-3,6-di(1H-imidazol-1-yl)-9H-carbazole, L(2) = 1,4-bis((1H-imidazol-1-yl)methyl)benzene, L(3) = 1,3-bis((1H-imidazol-1-yl)methyl)benzene and L(4) = 9,10-bis((1H-imidazol-1-yl) methyl)anthracene) yielded four [2 + 2] self-assembled metallacycles M(1)-M(4) in quantitative yields, respectively. All these newly synthesized assemblies were characterized by various spectroscopic techniques (NMR, IR, ESI-MS) and their sizes/shapes were predicted through geometry optimization employing the PM6 semi-empirical method. The benzil moiety was introduced in the backbone of the acceptor bisPt-NO(3) due to the interesting structural feature of long carbonyl C-C bond (∼1.54 Å), which enabled us to probe the role of conformational flexibility on size and shapes of the resulting coordination ensembles.

Copper-catalyzed direct synthesis of diaryl 1,2-diketones from aryl iodides and propiolic acids.

Benzil derivatives such as diaryl 1,2-diketones are synthesized via the direct decarboxylative coupling reaction of aryl propiolic acids and their oxidation. The optimized conditions are that the reaction of aryl propiolic acids and aryl iodides is conducted at 140 °C for 6 h in the presence of 10 mol % CuI/Cu(OTf)2 and Cs2CO3, after which HI (aq) is added and further reacted. The method shows good functional group tolerance toward ester, aldehyde, cyano, and nitro groups. In addition, symmetrical diaryl 1,2-diketones are obtained from aryl iodides and propiolic acid in the presence of palladium and copper catalysts.

One-pot, two-step desymmetrization of symmetrical benzils catalyzed by the methylsulfinyl (dimsyl) anion.

An operationally simple one-pot, two-step procedure for the desymmetrization of benzils is herein described. This consists in the chemoselective cross-benzoin reaction of symmetrical benzils with aromatic aldehydes catalyzed by the methyl sulfinyl (dimsyl) anion, followed by microwave-assisted oxidation of the resulting benzoylated benzoins with nitrate, avoiding the costly isolation procedure. Both electron-withdrawing and electron-donating substituents may be accommodated on the aromatic rings of the final unsymmetrical benzil.

Potential Treatments for Epiglottic Collapse in Obstructive Sleep Apnea: How Modified Drug-Induced Sleep Endoscopy Help?

OBJECTIVE: In patients with obstructive sleep apnea (OSA), epiglottic collapse (EC) constitutes a major factor in the failure of continuous positive airway pressure therapy and uvulopalatopharyngoplasty. This study explored treatments that can improve EC in patients with OSA through drug-induced sleep endoscopy with target-controlled infusion (TCI-DISE). STUDY DESIGN: Retrospective cohort study. SETTING: Tertiary center. METHODS: This study screened 352 OSA patients who underwent TCI-DISE between 2016 and 2022. Fifty-four patients with EC were included in the final analysis. EC severity was assessed multiple times through TCI-DISE with different interventions. RESULTS: The application of these interventions in patients with anteroposterior epiglottic collapse (apEC) led to a significant decrease in apEC severity from total to partial or no obstruction in 60.0% of patients by head rotation, in 53.6% by mouth closure, in 47.4% who received oral appliances (OA), and in 28.0% who received intermittent negative airway pressure (iNAP). With simultaneous head rotation, apEC severity decreased more significantly from total to partial or no obstruction in 77.8% of patients by mouth closure, in 70.3% who received OA, and in 68.0% who received iNAP. Lateral epiglottic collapse (latEC) severity decreased in 53.8% of patients after OA use and in 61.5% of patients with OA use and head rotation. CONCLUSION: This study identified head rotation with mouth closure as the most effective treatment for apEC through TCI-DISE. Patients with latEC had higher weight, apnea-hypopnea index, and body mass index compared with patients with apEC. OA use with head rotation appeared more effective in latEC through TCI-DISE.

Orthogonal control of endogenous gene expression in mammalian cells using synthetic ligands.

Gene switches have wide utility in synthetic biology, gene therapy, and developmental biology, and multiple orthogonal gene switches are needed to construct advanced circuitry or to control complex phenotypes. Endogenous vascular endothelial growth factor (VEGF-A) is crucial to angiogenesis, and it has been shown that multiple alternately spliced VEGF-A isoforms are necessary for proper blood vessel formation. Such a necessity limits the utility of direct transgene delivery, which can provide only one splice variant. To overcome this limitation, we constructed a gene switch that can regulate the (VEGF-A) locus in mammalian cells by combining an engineered estrogen receptor (ER) ligand-binding domain (LBD), a p65 activation domain, and an artificial zinc-finger DNA binding domain (DBD). Our gene switch is specifically and reversibly controlled by 4,4'-dyhydroxybenzil (DHB), a small molecule, non-steroid synthetic ligand, which acts orthogonally in a mammalian system. After optimization of the gene switch architecture, an endogenous VEGF-A induction ratio of >100-fold can be achieved in HEK293 cells at 1 µM DHB, which is the highest endogenous induction reported to date. In addition, induction has been shown to be reversible, repeatable, and sustainable. Another advantage is that the ligand response is tunable by varying the clonal composition of a stably integrated cell line. The integration of our findings with the technology to change ligand specificity and DNA binding specificity will provide the framework for generating a wide array of orthogonal gene switches that can control multiple genes with multiple orthogonal ligands.

Biochemical and structural characterization of recombinant short-chain NAD(H)-dependent dehydrogenase/reductase from Sulfolobus acidocaldarius highly enantioselective on diaryl diketone benzil.

The gene encoding a novel alcohol dehydrogenase that belongs to the short-chain dehydrogenases/reductases superfamily was identified in the aerobic thermoacidophilic crenarchaeon Sulfolobus acidocaldarius strain DSM 639. The saadh2 gene was heterologously overexpressed in Escherichia coli, and the resulting protein (SaADH2) was purified to homogeneity and both biochemically and structurally characterized. The crystal structure of the SaADH2 NADH-bound form reveals that the enzyme is a tetramer consisting of identical 27,024-Da subunits, each composed of 255 amino acids. The enzyme has remarkable thermophilicity and thermal stability, displaying activity at temperatures up to 80 °C and a 30-min half-inactivation temperature of ∼88 °C. It also shows good tolerance to common organic solvents and a strict requirement for NAD(H) as the coenzyme. SaADH2 displays a preference for the reduction of alicyclic, bicyclic and aromatic ketones and α-ketoesters, but is poorly active on aliphatic, cyclic and aromatic alcohols, showing no activity on aldehydes. Interestingly, the enzyme catalyses the asymmetric reduction of benzil to (R)-benzoin with both excellent conversion (98 %) and optical purity (98 %) by way of an efficient in situ NADH-recycling system involving a second thermophilic ADH. The crystal structure of the binary complex SaADH2-NADH, determined at 1.75 Å resolution, reveals details of the active site providing hints on the structural basis of the enzyme enantioselectivity.

One-pot synthesis of 2,4,5-trisubstituted imidazoles using [BPy]H2PO4, an efficient and recyclable catalyst.

[BPy]H(2)PO(4) was easily prepared and used as an efficient and recyclable catalyst for the one-pot synthesis of 2,4,5-trisubstituted imidazoles under solvent-free conditions in good to excellent yields. Solvent-free conditions, simple experimental and workup procedures, and the use of a nontoxic, recyclable catalyst of an environmentally benign nature are remarkable features of the procedure.