Double Bond System Research Articles

1,2-Azaphosphol-5-ene Complexes through Metal-Assisted Synthesis

Thermal ring opening of {[2-bis(trimethylsilyl)methyl-3-phenyl-2H-azaphosphirene-κP]pentacarbon-yltungsten(0)} (1) in toluene in the presence of 1-piperidino carbonitrile (2) and various mono- and disubstituted alkenes, i.e., ethyl acrylate (4), E-stilbene (6), fumaronitrile (7), and maleic anhydride (10), was investigated. Special emphasis was placed on the dependence of the regio- and stereoselectivity of the transiently formed nitrilium phosphane-ylide complex 3 on the electronic properties of the alkenes. Three-component reaction of 1, 2, and 4 yielded regioselectively a 1:1 mixture of the diastereomeric 4-ethoxycarbonyl-substituted 1,2-azaphosphol-5-ene complexes 5a,b; the constitution of 5a was unambiguously established by single-crystal X-ray diffraction. Whereas E-stilbene (6) gave no reaction with complex 3, fumaronitrile (7) reacted with transient 3 to furnish the diastereomeric 1,2-azaphosphol-5-ene complexes 8a,b together with the 2H-1,3,2-diazaphosphole complex 9; the product ratio of 2:1:1 was determined by 31 P{ 1 H} NMR spectroscopy. Reaction of 1, 2, and maleic anhydride (10) resulted in a complicated product mixture, whereby the constitution of the spirocyclic complexes 11a,b (bearing a 1,3,2-oxazaphosphol-3-ene moiety) is based on their NMR data. Further examination showed that the C-O double bond system of 10 did not participate in a [3+2] cycloaddition reaction if the thermal decomposition of complex 1 was carried out in neat benzonitrile, thus showing the preference of the transiently formed C-phenyl-substituted nitrilium phosphane-ylide complex 12 for the C-C double bond of 6: In this case, the bicyclic complexes 13a,b were formed exclusively.

Chromatographic techniques to determine conjugated linoleic acid isomers

Conjugated linoleic acid (CLA) is a complex mixture of positional and geometric isomers that contains a conjugated double-bond system and exhibits health-promoting attributes. Although cis-9 trans-11 is the predominant species in dairy foods and biological subtracts, there is a real need to determine the CLA-isomer distribution, since the isomers may have different biological functions. This review covers the latest advances in the analytical techniques, mainly GC-MS and Ag +-HPLC, to determine the isomeric profile of CLA.

Plant‐oil‐based lubricants and hydraulic fluids

AbstractIt is estimated that, at present, approximately 50% of all lubricants sold worldwide end up in the environment via total loss applications, volatility, spills or accidents. More than 95% of these materials are currently mineral oil based. In view of their high ecotoxicity and low biodegradability, mineral oil‐based lubricants constitute a considerable threat to the environment. In contrast, most lubricants and hydraulic fluids based on plant oils are rapidly and completely biodegradable and are of low ecotoxicity; moreover, lubricants based on plant oils display excellent tribological properties and generally have very high viscosity indices and flashpoints. However, in order to compete with mineral‐oil‐based products, some of their inherent disadvantages must be corrected, such as their sensitivity to hydrolysis and oxidative attack, and their behaviour at low temperatures. Various methods to improve the undesirable properties of native plant oils will be discussed. In parallel, government regulations that encourage or enforce the use of bio‐based fluids, at least in ecologically sensitive areas, will help to increase their market share. Using the numerous possibilities for selective breeding and/or chemical improvement of the double bond systems of natural fatty acids by increased R&D, the major obstacles regarding the use of plant‐based raw materials for the production of lubricant base fluids can be overcome and bio‐based fluids should expect a future with increasing market shares. Copyright © 2006 Society of Chemical Industry

Syntheses of conjugated octadecadienoic acids

Three approaches for the synthesis of octadecadienoic acids with conjugated double bond systems are presented: synthesis of (10Z, 12Z)-octadecadienoic acid via an enyne-substructure; the use of an educt with a conjugated double bond system for the synthesis of (10E, 12E)-octadecadienoic acid; and the Suzuki cross coupling for the synthesis of (7E,9Z)-octadecadienoic acid.

LiBx (0.82 < × ≤ 1.0) – an Incommensurate Composite Structure below 150 K

AbstractThe lithium boride LiBx (0.82 < × ≤ 1.0) contains linear boron chains isolelectronic to carbyne. The negatively charged boron chains are embedded in and stabilized by a lithium matrix. At room temperature they are disordered with respect to each other and also not commensurate with the Li matrix. Below about 150 K a phase transition takes place, where the boron chains successively order with respect to each other, but remaining still incommensurate with the Li substructure. The crystal structure of LiBx at 2 K was determined from neutron powder diffraction data and refined in the (3+1)‐dimensional superspace group $P{\bar 1}$(αβγ) The unit cell parameters are a = 4.012(1) Å, b = 4.012(1) Å, c = 2.794(1) Å, α = 90°, β = 90°, γ = 120° for the lithium and a = 4.017(1) Å, b = 4.019(1) Å, c = 1.578(1) Å, α=93.35(1), β = 92.83(1)°, γ = 119.71(1)° for the boron substructure, respectively. The q‐vector is (0.1267 0.1482 1.7707). The boron atoms within the linear chains are equidistant, suggesting a cumulated double bond system, similar to a cumulenic chain in the carbon case. Band structure calculations and the electron localization function give more insight into the unusual physical properties of LiBx.

5-Alkylresorcinols fromMeruliusincarnatus

Two new, 5-heptadeca-8'Z,11'Z,16-trienylresorcinol (1) and 5-heptadeca-9'E,11'Z,16-trienylresorcinol (2), and six known 5-alkylresorcinols (3-8) were isolated from the mushroom Merulius incarnatus. Compound 2 is the first 5-alkylresorcinol derivative that contains a trans-cis conjugated double bond system. Compounds 1, 2, 5, 6, 7, and 8 were found to inhibit methacillin-resistant Staphylococcus aureus (MRSA) with IC(50) values of 2.5, 15, 9.5, 8.0, 5.0, and 6.5 microg/mL, respectively. Compound 1 was also active against leishmania, with an IC(50) value of 3.6 microg/mL, and showed no cytotoxicity in our Vero cell test up to a concentration of 25 microg/mL. The structures of these isolates were determined by spectroscopic data including 1D and 2D NMR.

Bis‐methylene‐interrupted octadecadienoic fatty acids in Bulgarian bovine butter fats

AbstractPreparative silver nitrate thin‐layer chromatography of fatty acid methyl esters and gas chromatography‐mass spectrometry of 4,4‐dimethyloxazoline derivatives were applied in combination to analyze the cis,cis octadecadienoic (18:2) fraction in commercial samples of bovine butter fat in Bulgaria. The main component, 9,12–18:2 was accompanied by a series of bis‐methylene‐interrupted isomers, cis,cis‐5,9‐; 6,10‐; 9,13‐ and 11,15–18:2, which were unambiguously identified by their specific mass spectra. The latter are characterized by the presence of very intensive diagnostic fragments which help to correctly locate the position of the double bond system in the carbon chain. The cis,cis‐5,9–18:2 isomer was found for the first time in butter fat, and the 6,10–18:2 isomer has not been described as yet.

The effects of molecular aggregation and isomerization on the fluorescence of “push-pull” hyperpolarizable chromophores

Hyperpolarizable organic molecules are attracting interest for use in nonlinear optical devices. Some zwitterionic merocyanine chromophores with exceptionally high first hyperpolarizabilities have been synthesized that possess an electron donor moiety coupled to an electron acceptor through a conjugated double bond system. Aligned arrays of these molecules tethered to a polyurethane backbone and spun onto a substrate to form a thin film, respond to the application of external electric fields with changes to their refractive indices, i.e. the electro-optic effect. This behavior can be capitalized upon to fabricate optical switches and modulators. High concentrations, or loadings, of these nonlinear optical molecules in thin films are required to produce a usable electro-optic effect, ca. 0.1–0.5 mol L −1, and this promotes molecular aggregation which alters their polarizabilities and also has implications for their photostabilities. The fluorescence spectra of these molecules in polymer films at ambient temperature and in solution in a 9:1 ethanol–water mixture over a range of temperatures down to 80 K show a substantial blue shift as the temperature is lowered. This is attributed to a reduction in the solvating power of the solvent as it becomes increasingly more viscous at lower temperatures. At the lowest temperatures studied a shoulder on the lower energy side of the fluorescence spectral distribution is apparent which is ascribed to the formation of antiparallel dimers/aggregates; a consequence of the highly dipolar character of these molecules. In addition, dual fluorescence is observed in high viscosity environments suggesting the involvement of twisting about the bridging conjugated bond system that links the electron donor to the electron acceptor.

Prediction of gas chromatographic retention of polyunsaturated fatty acid methyl esters

Multivariate regression models were applied to predict retention indices as equivalent chain lengths (ECL) for methylene-interrupted polyunsaturated fatty acids. Simple molecular descriptors, the chain length, the number of double bonds and the position of the double bond system, were used as predictors. The merits of different variable combinations were evaluated. For general models, it was necessary to include the distance from the double bond system to both the carbonyl group (Δ-position) and the methyl end of the fatty acid ( n-position). The best accuracy was found for models including higher order terms of Δ and n. For models restricted to n-3 and n-6 isomers, it was not necessary to include the n-position among the variables. The highest residuals for the most accurate models were below 0.06 ECL units, and root mean square error of prediction was below 0.030. The ECL data was achieved by three different temperature programs on a cyanopropyl column.

Interaction of bovine serum amine oxidase with the polyamine oxidase inactivator MDL 72527

MDL 72527 was considered a selective inhibitor of FAD-dependent polyamine oxidases. In the present communication, we demonstrate that MDL 72527 inactivates bovine serum amine oxidase, a copper-containing, TPQ-enzyme, time-dependently at 25 °C. In striking contrast, the enzyme remained active after incubation with excessive MDL 72527 at 37 °C, even after 70 h of incubation. Inactivation of BSAO with MDL 72527 at 25 °C did not involve the cofactor, as was shown by spectroscopy and by reaction with phenylhydrazine. Docking of MDL 72527 is difficult, owing to its size and two lipophilic moieties, and it has been shown that minor changes in reaction rate of substrates cause major changes in K m and k cat/ K m. We hypothesise that subtle conformational changes between 25 and 37 °C impair MDL 72527 from productive binding and prevent the nucleophilic group from reacting with the double bond system.

Production of (10 E,12 Z)-conjugated linoleic acid in yeast and tobacco seeds

The polyenoic fatty acid isomerase from Propioniumbacterium acnes (PAI) was expressed in E. coli and biochemically characterized. PAI catalyzes the isomerization of a methylene-interrupted double bond system to a conjugated double bond system, creating (10 E,12 Z)-conjugated linoleic acid (CLA). PAI accepted a wide range of free polyunsaturated fatty acids as substrates ranging from 18:2 fatty acids to 22:6, converting them to fatty acids with two or three conjugated double bonds. For expression of PAI in yeast the PAI-sequence encoding 20 N-terminal amino acid residues was altered for optimal codon usage, yielding codon optimized PAI ( coPAI). The percentage of 10,12-CLA of total esterified fatty acids was 8 times higher in yeast transformed with coPAI than in cells transformed with PAI. CLA was detected in amounts up to 5.7% of total free fatty acids in yeast transformed with coPAI but none was detected in yeast transformed with PAI. PAI or coPAI under the control of the constitutive CaMV 35S promoter or the seed-specific USP promoter was transformed into tobacco plants. CLA was only detected in seeds in coPAI-transgenic plants. The amount of CLA detected in esterified fatty acids was up to 0.3%, in free fatty acids up to 15%.

Conjugated docosahexaenoic acid inhibits lipid accumulation in rats

Conjugated linoleic acid (CLA), which contains a conjugated double-bond system, and n-3 highly unsaturated fatty acids such as docosahexaenoic acid (DHA) are widely known to improve lipid metabolism. To examine the possibility that a fatty acid with a combination of these structural features might have stronger physiological effects, we prepared conjugated DHA (CDHA) by alkaline isomerization of DHA and examined its effects on lipid and sugar metabolism in rats. Rats were force fed with 200 mg of test oils [linoleic acid (LA), DHA, CLA or CDHA] everyday for 4 weeks. Compared with the animals from the other groups, those in the CDHA group showed a significant weight loss in white adipose tissue (57% of adipose tissue weight in the LA group) and significant decreases in the levels of liver triacylglycerol (TG; 65% of TG level in the LA group) as well as total cholesterol (TC; 88% of TC level in the LA group), indicating suppression of lipid accumulation in the liver and adipose tissue. In addition, plasma TG and TC levels significantly decreased (69% of TG level and 82% of TC level in the LA group), indicating improved lipid metabolism. In the liver, the fatty acid synthesis system was inhibited and the fatty acid β-oxidation system was activated, whereas the free fatty acid, glucose and tumor necrosis factor α levels in the plasma were lowered following CDHA administration. Hence, intake of CDHA appears to suppress the accumulation of fat in the liver and epididymal adipose tissue and improves lipid and sugar metabolism in rats.

Gas chromatography–mass spectrometry determination of metabolites of conjugated cis-9, trans-11, cis-15 18:3 fatty acid

Structural determination of polyunsaturated fatty acids by gas chromatography–mass spectrometry (GC–MS) requires currently the use of nitrogen containing derivatives such as picolinyl esters, 4,4-dimethyloxazoline or pyrrolidides derivatives. The derivatization is required in most cases to obtain low energy fragmentation that allows accurate location of the double bonds. In the present work, the following metabolites of rumelenic ( cis-9, trans-11, cis-15 18:3) acid, from rat livers, were identified: cis-8, cis-11, trans-13, cis-17 20:4, cis-5, cis-8, cis-11, trans-13, cis-17 20:5, cis-7, cis-10, cis-13, trans-15, cis-19 22:5, and cis-4, cis-7, cis-10, cis-13, trans-15, cis-19 22:6 acids by GC–MS as their 4,4-dimethyloxazoline and methyl esters derivatives. Specific fragmentation of the methyl ester derivatives revealed some similarity with their corresponding DMOX derivatives. Indeed, intense ion fragments at m/ z = M + − 69, corresponding to a cleavage at the center of a bis-methylene interrupted double bond system were observed for all identified metabolites. Moreover, intense ion fragments at m/ z = M + − 136, corresponding to allylic cleavage of the n-12 double bonds were observed for the C20:5, C22:5, C22:6 acid metabolites. For the long chain polyunsaturated fatty acids from the rumelenic metabolism, we showed that single methyl esters derivatives might be used for both usual quantification by GC–FID and identification by GC–MS.

Intercedensides D−I, Cytotoxic Triterpene Glycosides from the Sea Cucumber Mensamaria intercedens Lampert

Six new triterpene glycosides, intercedensides D-I (1-6), were isolated from the whole bodies of the sea cucumber Mensamria intercedens Lampert, which is found in the South China Sea. Their structures were elucidated by extensive spectroscopic analysis (NMR and ESIMS) and chemical methods. lntercedensides D (1), E (2), G (4), and H (5) have a conjugated double bond system (22Z,24-diene) in the aglycon side chain, while intercedensides F (3) and I (6) have only a single double bond (24, 25) in this same chain. lntercedensides D-H (1-5) showed significant cytotoxicity (ED(50) 0.96-5.0 mug/mL) against 10 human tumor cell lines.

Decomposition of metal tetrasulphophthalocyanines incorporated in SiO2 gels

The aggregation of metal 2,9,16,23-tetrasulphophthalocyanines, MTSPc (M=Fe, Co, Ni, Cu and Al), embedded in transparent monolithic gels of silica, prepared by the sol–gel method has been successfully controlled by the addition of N,N-dimethylformamide (DMF) or pyridine (py). The utilization of DMF produces materials less prone to fracture and with better optical properties than those obtained by the use of pyridine. In the case of CuTSPc, CoTSPc and NiTSPc species with DMF (4% v/v) some colour fading in the gels was observed. The comparative study of gels prepared with M(II)TSPc (M=Cu, Ni and Co) and (OH)M(III)TSPc (M=Fe, Al) species has shown that loss of colour in solution and in the monoliths depends on the oxidation number of the cation. An interaction between the DMF and the metal macrocycle, favoring the disruption of the conjugated double bond system of the organic macrocycle has been originally proposed, but now evidence is given that the possible decomposition of the complex is caused by internal conditions prevailing in the gel. Experiments in alkaline solution confirm that, when trapped in gels, (OH)M(III)TSPc forms μ-oxo dimers, and M(II)TSPc decomposes.

Direct monitoring of lipid oxidation in edible oils by Fourier transform Raman spectroscopy

Fourier transform Raman spectroscopy has been used to investigate the chemical changes taking place during lipid oxidation in several edible oils. Oxidative degradation of six vegetable oils was accelerated by heating at 160 °C. Formation of aldehydes was detected, and saturated as well as α,β-unsaturated aldehydes could be identified with the help of pure component spectra. The formation of conjugated double bond systems and the isomerisation of cis to trans double bonds was observed in the C C stretching region and found to follow a distinct pattern for the different oils. It was possible to associate these differences to the fatty acid composition. The time-dependent intensity changes in certain Raman bands were compared to conventional parameters used to determine the extent of oxidation in oils, such as anisidine value and K 270, and showed good correlation.

Synthesis and Properties of Novel Stilbazolium Analogues as Second-Order Nonlinear Optical Chromophores

Abstract This study synthesized a series of methoxystilbazolium analogues with π-conjugation extended by attaching a fused aromatic ring, i.e., 6-styrylisoquinolinium and 4-[2-(2-naphthyl)ethenyl]pyridinium derivatives with methoxy substituents. We evaluated their transition energies (Eegs) and second-order hyperpolarizabilities (βs) experimentally using their absorption spectra and a hyper-Rayleigh scattering measurement, respectively. Subsequently, we calculated βs using the MOPAC PM3 method. These values were compared with those of 4-[4-(4-methoxyphenyl)-1,3-butadienyl]pyridinium derivative, which is a stilbazolium analogue with π-conjugation that is simply extended by an increase of the double-bond number between two aromatic rings. This study clarified that the fused-ring systems possess large βs, irrespective of their relatively short absorption wavelengths, compared to the double-bond elongation system.

Analysis of the interaction of substituted coumarins with the DPPH free radical by means of multivariate statistics.

The interaction of some substituted coumarin derivatives with the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical was analysed by means of multivariate statistics using a variety of molecular descriptors. The compounds contain a conjugated double bond system, which was considered to be an essential structural characteristic for the free-radical scavenging activity. Partial least-square analysis led to an adequate two-component model based on bulk descriptors and the electronic properties concerning atoms involved or next to the double-bond system.

Synthesis of long chain n-3 and n-6 fatty acids having a photoactive conjugated tetraene group

Fatty acids of the n-3 and n-6 families containing a photoactive conjugated tetraene group near the carboxylate were prepared from several naturally occurring fatty acids by sequential iodolactonization and treatment with excess 1,8-diazabicyclo[5.4.0]undec-7-ene. The new conjugated fatty acids include 5 E,7 E,9 E,11 Z,14 Z- and 5 E,7 E,9 E,11 E,14 Z-eicosapentaenoic acids derived from arachidonic acid; 5 E,7 E,9 E,11 Z,14 Z,17 Z- and 5 E,7 E,9 E,11 E,14 Z,17 Z-eicosahexaenoic acids from eicosapentaenoic acid; and 4 E,6 E,8 E,10 Z,13 Z,16 Z,19 Z- and 4 E,6 E,8 E,10 E,13 Z,16 Z,19 Z-docosaheptaenoic acids from docosahexaenoic acid. All of the newly synthesized fatty acids were characterized by UV, 1 H NMR and mass spectroscopy. These new products represent the first examples of directed conjugation of methylene interrupted double bond systems. The products can be synthesized in gram quantities and in high yields (>50%). Interestingly, it did not prove possible to synthesize fatty acids having a triene group near the carboxyl group even using mild conditions and different synthetic approaches. Once initiated, the isomerization always continued until a tetraene group was formed. Because of the sensitivity of the tetraene group to light, these fatty acids have the potential for being used in tracking fatty acid movements in cells employing fluorescence techniques and in UV light-induced cross linking to membrane proteins.

Methods for Analysis of Conjugated Linoleic Acids and trans-18:1 Isomers in Dairy Fats by Using a Combination of Gas Chromatography, Silver-Ion Thin-Layer Chromatography/Gas Chromatography, and Silver-Ion Liquid Chromatography

Conjugated linoleic acids (CLA) are octadecadienoic acids (18:2) that have a conjugated double-bond system. Interest in these compounds has expanded since CLA were found to be associated with a number of physiological and pathological responses such as cancer, metastases, atherosclerosis, diabetes, immunity, and body fat/protein composition. The main sources of these conjugated fatty acids are dairy fats. Rumen bacteria convert polyunsaturated fatty acids, especially linoleic and linolenic acids, to CLA and numerous trans- containing mono- and diunsaturated fatty acids. It has been established that an additional route of CLA synthesis in ruminants and monogastric animals, including humans, occurs via delta9 desaturation of the trans-18:1 isomers. To date, a total of 6 positional CLA isomers have been found in dairy fats, each occurring in 4 geometric forms (cis,trans; trans,cis; cis,cis; and trans,trans) for a total of 24. All of these CLA isomers can be resolved only by a combination of gas chromatography (GC), using 100 m highly polar capillary columns, and silver-ion liquid chromatography, using 3 of these 25 cm columns in series. Complete analysis of all the trans-18:1 isomers requires prior isolation of trans monoenes by silver-ion thin-layer chromatography (TLC), followed by GC analysis using the same 100 m capillary columns operated at low temperatures starting from 120 degrees C. These analytical techniques are required to assess the purity of commercial CLA preparations, because their purity will affect the interpretation of any physiological and/or biochemical response obtained. Prior assessment of CLA preparations by TLC is also recommended to determine the presence of any other impurities. The availability of pure CLA isomers will permit the evaluation and analysis of individual CLA isomers for their nutritional and biological activity in model systems, animals, and humans. These techniques are also essential to evaluate dairy fats for their content of specific CLA isomers and to help design experimental diets to increase the level of the desired CLA isomers in dairy fats. These improved techniques are further required to evaluate the CLA profile in monogastric animals fed commercial CLA preparations for CLA enrichment of animal products. This is particularly important because absorption and metabolism will alter the ingested-CLA profile in the animal fed.