Conjugated Double Bonds Research Articles

Direct Introduction of OH Group to sp2-Carbon on Platinum-Loaded Titanium Oxide Photocatalyst

Photocatalytic oxidation of various organic compounds by using molecular oxygen has been broadly investigated as a valuable synthetic route, but the application has been still limited because the active oxygen species from the molecular oxygen are usually difficult to be controlled. In this short review, we describe two kinds of photocatalytic oxygenation with H2O molecule as a source of OH group; i.e., photocatalytic hydroxylation of aromatic ring and photocatalytic hydration of alkene, on Pt/TiO2 photocatalyst. In both reactions, a photoformed active oxygen species attacks to the sp2-carbon to form a reaction intermediate. In the aromatic ring hydroxylation, the elimination of the H atom from the intermediate proceeds while the conjugate double bond of the aromatic ring maintains. In the alkene hydration, the addition of the H radical to the intermediate results in forming an alcohols molecule with the saturation of the double bond. In the former case, the electrophilic property of the active oxygen species predominantly determines the orientation of the OH group in the produced phenols. On the other hand, in the latter case, the thermodynamic stability of the intermediate radical species leads the active oxygen species preferentially to the terminal sp2-carbon, which makes it possible to provide the unique regioselectivity of alcohol according to the anti-Markovnikov rule.

Natural amber, copal resin and colophony investigated by UV-VIS, infrared and Raman spectrum

Natural amber, copal resin and colophony are have investigated by UV-VIS, infrared and Raman spectrum. In order to distinguish the natural amber, copal resin and colophony, we have successfully used the nondestructive examination (NDE) technology. The results show that UV-VIS could not distinguish these compositions. The infrared spectra can distinguish them, but the technology may destroy the specimen. The Raman spectra show three characteristic peaks of vibration near position 932 cm –1 and position 1179 cm –1 of copal resin, which confirm the existence of terpenes compounds in it. In the Raman spectra of colophony, the vibration characteristic peak at position 1589 cm –1 , caused by the conjugate double bond of internal unsaturated resin acid, is the basis of the characteristic difference between colophony and natural amber. The advantages of the distinguished technology by Raman spectroscopy are convenient and nondestructive examination for natural amber, copal resin and colophony.

Distinguishing Alternative Reaction Pathways by Single‐Molecule Fluorescence Spectroscopy

Focus on chemical transitions: Epoxidation of a double bond in conjugation to a fluorescent dye was studied at single-molecule level. Direct observation of oxirane formation, indicated as a spectral shift from substrate to product state, revealed an alternative reaction pathway for the epoxidation reaction. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Skin Sensitization of Epoxyaldehydes: Importance of Conjugation

Structure-activity relationship (SAR) models are important tools for predicting the skin sensitization potential of new compounds without animal testing. In compounds possessing a structural alert (aldehyde) and an activation alert (double bond), it is important to consider bioactivation/autoxidation (e.g., epoxidation). In the present study, we have explored a series of aldehydes with regard to contact allergy. The chemical reactivity of these 6 aldehydes toward a model hexapeptide was investigated, and their skin sensitization potencies were evaluated using the local lymph node assay (LLNA). Overall, we observed a similar trend for the in vitro reactivity and the in vivo sensitization potency for the structural analogues in this study. The highly reactive conjugated aldehydes (α,β-unsaturated aldehydes and 2,3-epoxyaldehydes) are sensitizing moieties, while nonconjugated aldehydes and nonterminal aliphatic epoxides show low reactivity and low sensitization potency. Our data show the importance of not only double bond conjugation to aldehyde but also epoxide-aldehyde conjugation. The observations indicate that the formation of nonconjugated epoxides by bioactivation or autoxidation is not sufficient to significantly increase the sensitization potency of weakly sensitizing parent compounds.

Conjugated linolenic acid nanoparticles inhibit hypercholesterolemia induced by feeding a high-fat diet in male albino rats

Conjugated linolenic acid (CLnA) refers to a group of octadecatrienoic acid isomers that have three double bonds in conjugation. However, CLnA is highly prone to oxidative damage due to the presence of unsaturation in CLnA. Nanoencapsulation offers increased stability of the CLnA molecule so that CLnA can show its full activity. The present study was designed to clarify the effects of two types of CLnA rich oil nanocapsules (CLnA rich oil nanocapsules with lipoic acid and CLnA rich oil nanocapsules with tert-butylhydroquinone [TBHQ]) on hypercholesterolemia induced by feeding a high-fat diet in male albino rats. CLnA rich oil nanocapsules were prepared by the ultrasonication method and the freeze-drying technique. The mean size of CLnA rich oil nanocapsules varied from 150 to 160 nm. The feeding experiment was carried out for a period of 30 days. Results showed that CLnA rich oil nanocapsules reduced the blood lipids, tissue lipids and plasma viscosity significantly. This paper is the first report of the lipid-lowering effects of CLnA rich oil nanocapsules suggesting that the CLnA rich oil nanocapsules could be used for the treatment of hypercholesterolemia. Lipoic acid showed better protective effect than TBHQ.

Analysis and Antioxidant Capacity of Anthocyanin Pigments. Part II: Chemical Structure, Color, and Intake of Anthocyanins

Anthocyanins belong to a large group of secondary plant metabolites collectively known as flavonoids, a subclass of the polyphenol family. They are a group of very efficient bioactive compounds that are widely distributed in plant food. Anthocyanins occur in all plant tissues, including leaves, stems, roots, flowers, and fruits. Research on phenolic compounds through the last century, from the chemical, biochemical, and biological points of view, has focused mainly on the anthocyanins. Anthocyanins have structures consisting of two aromatic rings linked by three carbons in an oxygenated heterocycle (i.e., a chromane ring bearing a second aromatic ring in position 2). The basic chromophore of anthocyanins is the 7-hydroxyflavilyum ion. Anthocyanin pigments consist of two or three chemical units: an aglycon base or flavylium ring (anthocyanidin), sugars, and possibly acylating groups. Only six of the different anthocyanidins found in nature occur frequently and are of dietary importance: cyanidin, delphinidin, petunidin, peonidin, pelargonidin, and malvidin. Each aglycon may be glycosilated or acylated by different sugars and aromatic or aliphatic acids, yielding over 600 different anthocyanins reported from plants. The sugar moiety is typically attached at the 3-position on the C-ring or the 5-position on the A-ring. The chromophore of eight conjugate double bonds carrying a positive charge on the heterocyclic oxygen ring is responsible for the intensive red-orange to blue-violet color produced by anthocyanins under acidic conditions. Anthocyanins occur in solution as a mixture of different secondary structures: flavylium ion, a quinoidal base, a carbinol base, and a chalcone pseudobase. Self-association, intermolecular, and intramolecular co-pigmentation of anthocyanins leads to the formation of tertiary structures through varying stabilization mechanisms. Anthocyanin composition has been used as a botanical tool for taxonomic classification of plants. In addition, anthocyanin profiles of fruits and vegetables allow detecting adulteration of anthocyanin-based products and are indicators of product quality. Anthocyanins are common components of the human diet, as they are present in many foods, fruits, and vegetables, especially in berries. Moreover, anthocyanins have an antioxidant activity, depending to a large extent upon their chemical structure. Many epidemiological studies have shown the benefits of a diet rich in fruit and vegetables to human health, and for the prevention of various diseases associated with oxidative stress, such as cancer and cardiovascular diseases. Anthocyanin-rich extracts are increasingly attractive to the food industry as natural alternatives to synthetic FD&C dyes and lakes, because of their coloring properties. Anthocyanins are also one of the nine European Union-designated natural color classes. Various adverse effects on health have frequently been attributed to synthetic antioxidants. For these reasons, currently, there is a trend towards relying on antioxidants derived from natural products. Anthocyanins act as antioxidants both in the foodstuffs in which they are found and in the organism after intake of these foods. This review, like the first one of the series, intends to reflect the interdisciplinary nature of the research that is currently carried out in this prolific area.

Study of molecule spectra of carotenoid

Carotenoid is a short-chain polyene biomolecule of 9 CC conjugate double-bonds. Due to its special structure carotenoid is used not only in photoprotection and anti-cancer, but also in molecule wires, light switch, and light filter. In this paper molecule spectra of carotenoid are studied. The carotenoid has the broadband fluorescence, the broadband stimulated Raman scattering is obtained when the fluorescence of carotenoid is used to enhance stimulated Raman scattering. Electron energy gap of carotenoid becomes narrow with temperature decreasing, and absorption spectra are red-shifted. These characteristics can make the carotenoid a high-quality semiconductor component. Raman active is intensive and the 3rd order optical nonlinear coefficient is large. The Raman scattering cross section of CC bond is about 10 orders of magnitude larger than that of common molecule. The Raman scattering intensity of overtone is intensive: the ratio of overtone to basic frequency is around 0.5 at low temperature. These spectrum characteristics of carotenoid are significant for studying polyene molecule structure, property and non-biology domain.

X-ray photoelectron spectroscopic characterization of the acetylene cyclotrimerization catalyst NbCl2(C n H n ) (n = 10–12)

The elemental and ionic compositions of the surface of NbCl2(C n H n ) (n = 10–12), an active catalyst for acetylene cyclotrimerization into benzene, have been determined by X-ray photoelectron spectroscopy. Binding energy data for the sample sputtered with argon ions E b (Nb3d 5/2) = 203.8–204.2 eV) suggest that the oxidation state of niobium in the active catalyst is +2 or +3. The narrow C1s line indicates the equivalence of all carbon atoms, and the corresponding binding energy, E b(C1s) = 284.0 eV, is close to the BE value for cyclic unsaturated hydrocarbons with conjugate double bonds. Interacting with atmospheric oxygen and moisture during sample preparation, niobium ions on the catalyst surface oxidize to their highest oxidation state, +5, characterized by E b (Nb3d 5/2) = 207.3–207.7 eV. These data suggest that niobium oxychlorides or oxides form ion the sample surface. The catalyst is stable in a high vacuum and undergoes slight charging under the action of an X-ray beam, showing poor dielectric properties.

Cycloaddition reactions of 2- or 3-substituted 1-benzopyran-4-ones having a double bond in conjugation with the pyran 2,3-olefinic bond

Cycloaddition reactions of 2- or 3-substituted 1-benzopyran-4-ones having a double bond in conjugation with the pyran 2,3-olefinic bond

Monitoring cellular responses upon fatty acid exposure by Fourier transform infrared spectroscopy and Raman spectroscopy

We investigated the applicability of FTIR-spectroscopy as a high throughput screening method for detection of biochemical changes in intact liver cells in bulk upon fatty acid exposure. HepG2 cells adapted to serum free (HepG2-SF) growth were exposed to four different fatty acids, three octadecenoic acids, differing in cis/trans-configuration or double bond position (oleic acid, elaidic acid and vaccenic acid) as well as palmitic acid in three days. High throughput FTIR spectroscopic measurements on dried films of intact cells showed spectra with high signal-to-noise ratio and great reproducibility. When applying principal component analysis (PCA) a clear discrimination between fatty acid exposures was observed. Higher levels of triacylglycerides were accumulated in cells exposed to elaidic acid than when exposed to the other fatty acids; the least accumulation appeared to be in cells exposed to palmitic acid. An increased absorption at ~966 cm(-1) corresponding to trans-double bond was detected upon elaidic acid exposure but not upon vaccenic acid exposure. Instead, upon vaccenic acid exposure two new absorption bands were observed at 981 and 946 cm(-1) due to the presence of double bond conjugation. Raman spectroscopy on single cells, with and without treatment by vaccenic acid, confirmed the presence of conjugation. By fatty acid composition analysis, the conjugation was further specified to be conjugated linoleic acid (CLA) isomers. Thus, instead of being preserved as a monounsaturated fatty acid, vaccenic acid was converted into CLA in HepG2 cells. The results demonstrate the applicability of high-throughput FTIR spectroscopy as an explorative method in in vitro systems from which biologically relevant hypotheses can be generated and further investigated.

Bisindole anchored mesoporous silica nanoparticles for cyanide sensing in aqueous media

For CN(-) recognition, a series of bisindolyl compounds 1-3 were prepared, and their chromodosimetric color changes toward anions were investigated. Nucleophilic addition of the cyanide ion to the meso position of the bisindolyl group gave rise to breaking of the double bond conjugation, thereby inducing spectroscopic changes in the compound. Mesoporous silica nanoparticles 3 also gave color changes from deep orange to yellow in response to the cyanide ion.

Relationship between the tautomeric structures of curcumin derivatives and their Aβ-binding activities in the context of therapies for Alzheimer's disease

Curcumin, which can exist in an equilibrium between keto and enol tautomers, binds to β-amyloid (Aβ) fibrils/aggregates. The aim of this study was to assess the relationship between the tautomeric structures of curcumin derivatives and their Aβ-binding activities. Curcumin derivatives with keto-enol tautomerism showed high levels of binding to Aβ aggregates but not to Aβ monomers. The binding activity of the keto form analogue of curcumin to Aβ aggregates was found to be much weaker than that of curcumin derivatives with keto-enol tautomerism. The color of a curcumin derivative with keto-enol tautomerism, which was substituted at the C-4 position, changed from yellow to orange within 30 min of being combined with Aβ aggregates in physiological buffer. This resulted from a remarkable increase in the enol form with extended conjugation of double bonds upon binding. These findings suggest that curcumin derivatives exist predominantly in the enol form during binding to Aβ aggregates, and that the enolization of curcumin derivatives is crucial for binding to Aβ aggregates. The keto-enol tautomerism of curcumin derivatives may be a novel target for the design of amyloid-binding agents that can be used both for therapy and for amyloid detection in Alzheimer's disease.

Synthesis and structure–activity relationship of botryllamides that block the ABCG2 multidrug transporter

In previous work, botryllamides discovered from the marine ascidian Botryllus tyreus were characterized as selective inhibitors of the ABCG2 multidrug transporter. However, the structural basis for this activity could not be established. In this study, botryllamide F, the core botryllamide structure, and botryllamide G, the most potent botryllamide ABCG2 inhibitor, were synthesized along with a series of structural variants for evaluation of structure–activity relationships. The biological activity of synthetic botryllamide analogs implied that the 2-methoxy- p-coumaric acid portion, and the degree of double bond conjugation within this group, were critical for inhibition of ABCG2. However, variations in the substituents on the two aryl groups did not appear to significantly impact the potency or degree of inhibition.

A highly regioselective route to arbutin esters by immobilized lipase from Penicillium expansum

Immobilized lipase from Penicillium expansum, a novel and inexpensive enzyme preparation that we immobilized in our laboratory, was an excellent catalyst for highly regioselective acylation of arbutin with fatty acid vinyl esters. For the enzymatic butanoylation of arbutin, under the optimal conditions, initial reaction rate was 75.1 mM/h, and substrate conversion and regioselectivity were greater than 99%. In addition, a variety of 6′-esters of arbutin were prepared with high conversion (>99%) and excellent regioselectivity (>99%). It was found that the enzymatic reaction rate varied widely with different acyl donors, presumably owing to their different interactions with the active site of the lipase. The immobilized lipase from P. expansum displayed highest catalytic activity with medium-length straight-chain acyl donors. Acyl donors bearing a substituent or a conjugate double bond gave reduced reaction rates.

(E)-2-(2-Nitro-prop-1-en-yl)furan.

Crystals of the title compound, C7H7NO3, under Mo Kα radiation sublime in less than 1h at room temperature. However, it was possible to collect data at 100K. It crystallized as the E isomer only. A double-bond conjugation in the furan ring is extended to the nitro­alkenyl group. Mol­ecular associations were realized in the crystal through N⋯π [3.545 (2) Å] inter­actions involving the furan ring and C—H⋯O hydrogen bonds.

Reactions of Group III Biheterocyclic Complexes

Group III alkyl complexes supported by a ferrocene diamide ligand (1,1'-fc(NSi(t)BuMe(2))(2)) have been found to be reactive toward aromatic N-heterocycles such as 1-methylimidazole and pyridines. These reactions were investigated experimentally and computationally. An initial C-H activation event is followed by a coupling reaction to form biheterocyclic complexes, in which one of the rings is dearomatized. In the case of 1-methylimidazole, the biheterocyclic compound could not be isolated and further led to an imidazole ring-opened product; in the case of pyridines, it transformed into an isomer with extended conjugation of double bonds. Mechanisms for both reactions are proposed on the basis of experimental and computational results. DFT calculations were also used to show that an energetically accessible pathway for the ring-opening of pyridines exists.

Timing of the Δ10,12-Δ11,13 Double Bond Migration During Ansamitocin Biosynthesis in Actinosynnema pretiosum

The timing of introduction of the unusually placed Delta(11,13) diene system in ansamitocin (AP) biosynthesis was probed by synthesizing optically active potential tri- and tetraketide intermediates as their SNAC thioesters. An AP-nonproducing mutant Actinosynnema pretiosum was complemented by the R enantiomer of the triketide and by the tetraketide with rearranged double bonds, but not by the tetraketide carrying the double bonds in conjugation to the thioester function. The results show that the double bonds are installed in their final positions during processing of the nascent polyketide on module 3 of the asm PKS and that KS4 of the PKS acts as a gatekeeper which accepts only a tetraketide with shifted double bonds as substrate for further processing.

Characterisation of Ni+ implanted PEEK, PET and PI

Polyimide (PI), polyetheretherketone (PEEK) and polyethyleneterephthalate (PET) were implanted with 40keV Ni+ ions at room temperature at fluences ranging from 1.0×1016 to 1.5×1017ionscm−2 and with ion current density varying between 4 and 10μAcm−2. The depth profiles of the implanted Ni atoms determined by the RBS technique were compared with those predicted by the SRIM and TRIDYN codes. Hydrogen depletion as a function of the ion fluence was determined by the ERDA technique, and the compositional and structural changes of the polymers were characterised by the UV–vis and XPS methods. The implanted profiles differed significantly from those predicted by the SRIM code while the lower fluences were satisfactorily described by the TRIDYN simulation. A significant hydrogen release from the polymer surface layer was observed along with significant changes in the surface layer composition. The UV–vis results indicated an increase in the concentration and conjugation of double bonds.

Synthesis of Oligo(1,6-heptadiynes) with a Single Structure and Terminal Methylene Groups Using Molybdenum-Based Wittig and Metathesis Chemistry. 1. 2,6-Dimethylphenylimido Systems

In this paper we demonstrate a method of synthesizing oligoenes of diisopropyldipropargylmalonate, [CH2][bx][CH2] (x = 2, 3, 4, 5), in which the “b” repeat unit is identical to the five-membered ring formed in a tail-to-tail cyclopolymerization of diisopropyldipropargylmalonate, and methylene groups are capping the ends. For example, a “degenerate” metathesis reaction between the “monomer”, [CH2][b][CH2], and 2 equiv of Mo(NAr′)(CHCMe2Ph)(ORF6)2 ([Mo][CHCMe2Ph] where Ar′ = 2,6-Me2C6H3 and ORF6 = OCMe(CF3)2) gives [Mo][b][Mo]. An “Mo-Wittig” reaction between [Mo][b][Mo] and 2 equiv of the aldehyde, [CH2][b][O], then gives the “trimer”, [CH2][b3][CH2]. Treatment of [CH2][b3][CH2] with 2 equiv of [Mo][CHCMe2Ph] gives [Mo][b3][Mo], which upon treatment with 2 equiv of [CH2][b][O] gives the “pentamer”, [CH2][b5][CH2], which contains 11 double bonds in conjugation in a molecule in which the repeat units are connected by trans C═C bonds. The oligoenes are not always obtained in high yield in pure form because (inter alia) C═C metathesis reactions compete with the Mo-Wittig reaction of the aldehyde (e.g., to give [CH2][b2][CH2] also in the synthesis of [CH2][b3][CH2]). These complications could be minimized by employing adducts (L)[Mo][bx][Mo](L), where L = PMe3 or quinuclidine, instead of base-free [Mo][bx][Mo] species in the Mo-Wittig reaction. X-ray structures are reported for [CH2][b2][CH2], [CH2][b3][CH2], (THF)[Mo][b2][Mo](THF), (Et2O)[Mo][b3][Mo](Et2O), and a mixture of homochiral and heterochiral [quin][Mo][b][Mo][quin].

Probing Inhibitory Effects of Antrodia camphorata Isolates Using Insect Cell-Based Impedance Spectroscopy: Inhibition vs Chemical Structure

A continuous online technique based on electric cell-substrate impedance sensing (ECIS) was used for probing inhibitory effects on Spodoptera frugiperda Sf9 insect cells exposed to structurally similar compounds isolated and purified from the fruiting bodies of the fungus Antrodia camphorata. Such chemicals consisted of three ergostane-related steroids and five lanosta-related triterpenes, which are known for their diverse properties and use in the formulation of nutraceuticals and functional foods. The half-inhibition concentration (ECIS(50)), the level at which 50% inhibition of the resistance response was obtained, was determined from the response function to establish inhibitory effects of the different isolates. A slight change in their chemical structures resulted in significant effects on inhibition as probed by impedance spectroscopy. The ergostane-related steroids were mostly inhibitory, but replacing their ketone groups with hydrogen or hydroxyl groups significantly reduced the inhibition. Similarly, the addition of methyl or carboxymethyl groups also lowered the inhibition. Removal of the double bond conjugation within the rings (sulfurenic acid) of the isolate drastically reduced the inhibition.