Structure and absolute configuration of an unsaturated anteiso fatty acid from Bacillus megaterium

Gas chromatography in combination with electron ionization mass spectrometry (GC/EI-MS) was used to determine the fatty acids of a membrane lipid from Bacillus megaterium. Special attention was put on the structure and absolute configuration of a monoenoic fatty acid previously described in this sample. GC/EI-MS operated in the selected ion monitoring mode was used to determine twelve fatty acids in the bacterium. Methyl esters were prepared to verify the presence of a 14-methylhexadecenoic acid (a17:1) isomer. The position of the double bond of the a17:1 isomer and four further monoenoic fatty acids was elucidated by means of their picolinyl esters produced by the transesterification of the phospholipid. For the a17:1 isomer, the double bond was located between C-5 and C-6. Silver ion liquid chromatography was used to verify that the double bond was in cis-configuration. The bacterial 14-methylhexadec-5-enoic acid (a17:1Δ5) is chiral due to the stereogenic C-14 carbon. Initial enantioselective measurements were carried out with isomers of a17:1Δ5 which were available in form of racemic and (S)-enantiopure cis- and trans-isomers of a17:1Δ12 previously synthesized. The cis-a17:1Δ12 enantiomers were partly resolved on a chiral stationary phase coated with 50% heptakis(6-O-tert.-butyldimethylsilyl-2,3-di-O-methyl)-β-cyclodextrin in OV-1701 (β-TBDM). However, resolution of the enantiomers of the trans-isomer of a17:1Δ12 failed. Only one peak was also observed for the a17:1Δ5 isomer from B. megaterium. Thus, it remained unclear whether the compound a17:1Δ5 was racemic or enantiopure in the sample. To clarify this point, we separated the cis-monoenoic fraction from the saturated fatty acids. Then, the monoenoic fraction was hydrogenated in order to transform a17:1Δ5 into 14-methylhexadecanoic acid (a17:0). This chiral fatty acid was known to be sufficiently enantioseparated on the β-TBDM column and was found to be (S)-enantiopure in the sample. Hence, these measurements verified that the B. megaterium sample contained enantiopure (S)-a17:1Δ5.     

Toward new biosilicones: hydrosilylation of fish oil unsaturated fatty acid esters

Hydrosilylation of fatty acid methyl esters (FAMEs) were efficiently catalyzed by Speier's and Wilkinson's catalysts in the case of vinylic acid esters, but less efficiently in the case of ­non‐vinylic ones, which gave non‐regiospecific additions. In the latter case, initiation by radicals led to regiospecific reactions for oleic esters (C10‐silylation). This regiospecificity can be attributed to the higher stability of the C10‐silylated adduct and of the corresponding radical intermediate. Only regioselective addition was observed for linoleic esters (C13‐silylation ≈ 70%, C10 ≈ 20%, C9 ≈ 10%). Molecular modeling was used to examine the stability of the isomeric products and radicals. The new concept of radical initiation sequence has been successfully applied to FAMEs and then was extended to crude fish oil. Copyright © 2001 John Wiley & Sons, Ltd.     

Malyngic acid,a new fatty acid from Lyngbya majuscula

Malyngic acid, a major fatty acid in several varieties of the marine blue-green alga Lyngbya majuscula, has been determined to be 9(S),12(R),13(S)-trihydroxyoctadeca-10(E),15(Z)-dienoic acid from chemical and spectral data and by its conversion to 9(S),12(R),13(S)-trihydroxystearic acid and degradation to 2-deoxy-D-ribitol.     

A new eudesmane derivative and a new fatty acid ester from Sambucus williamsii

1,4,13-Trihydroxy-eudesm-11(12)-ene, a new eudesmane derivative (3), (9E)-8,11,12-trihydroxyoctadecenoic acid methyl ester, a new fatty acid ester (2) and tianshic acid (1) were obtained from the stems of Sambucus williamsii. Their structures were elucidated by physiochemical properties and spectroscopic analysis. Both compounds 1 and 2 showed stimulating effects on alkaline phosphatase activity of the osteoblastic UMR106 cell about 1.5 fold at 30 mumol/l while they had no effects on cell proliferation.     

Structure elucidation of new fusarielins from Fusarium sp. and their antimicrobial activity

Three new fusarielins, 3‐epi‐fusarielin H ( 1 ), 3‐O‐methyl‐fusarielin H ( 2 ), and 3‐O‐methyl‐epi‐fusarielin H ( 3 ), were isolated from the fungus Fusarium sp. together with the known analogues, fusarielins F ( 4 ) and G ( 5 ). The structures of these compounds were elucidated by analysis of their ESI‐HRTOFMS, 1D and 2D NMR spectroscopic data. The new compounds exhibited weak antibacterial effect against Staphylococcus aureus.     

Preparation and thin-layer chromatography of bromo-derivatives of unsaturated fatty acid esters. A simple and rapid procedure for fatty acid analysis.

Bromo-addition products of unsaturated long-chain fatty acid esters have been prepared and chromatographed on thin layers of unmodified silica gel. The polarity of these derivatives was found to be directly related to the number of double bonds of the parent fatty acid from which they were derived. This has been made the basis of a simple method for assessing the relative proportions of the main fatty acid classes in a mixture.     

Sm/TiCl4体系对α,β-不饱和羧酸的邻二溴化合物的脱溴研究

低价钛试剂(又称为McMuny试剂)可由TiCl4或者TiCl3在还原剂如LiAlH4，Li，Mg，Zn，Cu-Zn，C8K等作用下得到。近年来，由稀土金属Sm与TiCl4生成的低价钛体系在有机反应和有机合成中的应用也得到了较多研究。例如，Sm/TiCl4体系可以促进烷基硫氰酸酯或烷基硫代硫酸钠生成烷基二硫醚；可以促进亚砜脱氧变成硫醚。芳磺酰氯在Sm/TiCl4的作用下发生偶联脱氧生成二硫醚；     

Structure of an unsaturated fatty acid with unique vicinal dimethyl branches isolated from the Okinawan soft coral of the genus Sinularia

A new unsaturated fatty acid with unique vicinal dimethyl branches was isolated from the Okinawan soft coral of the genus Sinularia. The structure of the compound was determined based on the results of spectroscopic analysis and chemical conversion. The absolute configuration was deduced by applying the Ohrui-Akasaka method.     

Metathesis of renewable unsaturated fatty acid esters catalysed by a phoban-indenylidene ruthenium catalyst

The phoban-indenylidene complex is a robust catalyst for self-metathesis and ethenolysis reactions of methyl oleate. The phoban-indenylidene catalyst was characterized by X-ray analysis, NMR and microanalysis and was used in various self-metathesis and ethenolysis of methyl oleate, giving rise to significantly higher end of run conversions compared to Grubbs 1st generation catalyst. These complexes are more stable and active than commercial Grubbs 1st generation catalyst, can be accessed from simple precursors and should give rise to more economical metathesis processes.     

Reactive uptake of NO3 radicals by unsaturated fatty acid particles

The reactive uptake of NO(3) by particles containing four unsaturated fatty acid species was studied for the first time in a flow tube reactor coupled to a chemical ionization mass spectrometer (CIMS). Using a mixed-phase relative rates technique, the reactive uptake coefficients, γ(part), were determined to be (0.27 ± 0.06) for oleic acid (OA), (0.53 ± 0.12) for linoleic acid (LA), (0.72 ± 0.17) for linolenic acid (LNA), and (1.01 ± 0.18) for conjugated linoleic acid (CLA) in N(2) bath gas. In the presence of 20% O(2), their uptake coefficients are (0.31 ± 0.09) for OA, (0.55 ± 0.12) for LA, (0.78 ± 0.17) for LNA, and (1.08 ± 0.17) for CLA. All the uncertainties are 2σ and represent precision only. The products of the NO(3) reactions with these organic particles were studied in the presence and absence of O(2) using CIMS. It was found that the detected yields and compositions of the products were substantially different with or without O(2). Based on the observed products and general gas-phase chemistry of NO(3) radicals, a reaction mechanism is proposed for NO(3) reactions with unsaturated organic particles. The atmospheric implications of the heterogeneous chemical processes involving NO(3) are also discussed.     

内南五味子化学成分的研究

从内南五味子的茎藤中分得七个化合物, 经波谱和X衍射分析, 其中五广系一类新型的螺环衍生物木脂素, 分别定名为内南五味子素(3), 内南五味子素乙(4), 丙(5),J(6)及异内南五味子素(7), 另外两个已知化合物为南五味子素和β-谷甾醇。     

Retention behaviour of unsaturated fatty acid methyl esters on porous graphitic carbon

The eluotropic strength of binary mobile phases was calculated for three homologous series of cis, trans, and cis-cis unsaturated fatty acid methyl esters (FAMEs). Binary mobile phases with chloroform, dichloromethane, or tetrahydrofuran as strong solvent and methanol or acetonitrile as weak solvent were tested. The volume fraction of strong solvent in the binary phases was between 0.3 and 0.8. Curves of eluotropic strength versus volume fraction of strong solvents showed similar trends to previously published results for saturated homologues. Correlation coefficients of the plots of eluotropic strength values for saturated versus unsaturated FAMEs were close to 1.0. Therefore these similarities validate the model of eluotropic strength previously established with saturated FAMEs as relevant for unsaturated FAMEs. The separation factors between cis and trans homologues always showed elution of the cis before the trans homologue. The difference in retention is due primarily to the geometry of the molecule. The retention is lowered more by the addition of a first carbon double bond than by the addition of a second one, independently of the mobile phase composition.     

Tagetnoic acid,a new lipoxygenase inhibitor peroxy fatty acid from Tagetes minuta growing in Saudi Arabia

Abstract

A new peroxy fatty acid, tagetnoic acid (5) [4-((3S,6S)-6-((3E,8E)-octadeca-3,8-dien-1-yl)-3,6-dihydro-1,2-dioxin-3-yl)butanoic acid] and four known metabolites: ecliptal (5-formyl-α-terthiophene) (1), 5-(4-hydroxybut-1-ynyl)-2,2′-bithiophene (2), 22,23-dihydrospinasterone (3), and stigmasterol (4) were separated from the n-hexane fraction of the aerial parts of Tagetes minuta L. (Asteraceae). Their chemical structures were verified using IR, UV, 2D and 1D NMR, and HRMS. Compounds 3–5 displayed potent lipoxygenase inhibitory potential with IC₅₀s 2.26, 1.83, and 1.17?μM, respectively compared to indomethacin (IC₅₀ 0.89?μM). Moreover, molecular docking study revealed that the potent activity of 5 is due to H-bonding and hydrophobic interaction. The results of this study suggested that Tagetes minuta dietary consumption would be useful for the individuals at risk of acute and chronic inflammatory disorders.     

Energetics of the biosynthesis of cyclopentenones from unsaturated fatty acids

Polyunsaturated fatty acids like linolenic acid or arachidonic acid upon enzymatic hydroxylation (lipoxygenases) can lead to corresponding hydroperoxides. Their dehydration gave rise to vinyl allene oxides, which cyclized into cyclopentenones, precursors of jasmonic acid or prostanoids.     

A new fatty acid ester from Nigella sativa var. hispidula Boiss showing potent anti-protein tyrosine phosphatase 1B activity

A new fatty acid ester (1) and seven known phenolic compounds, i.e. salfredin B₁₁ (2), nigephenol C (3), nigephenol B (4), acetovanillion (5), p-hydroxybenzoic acid (6), p-hydroxy-acetophenone (7) and p-hydroxybenzaldehyde (8), were isolated from the seeds of Nigella sativa var. hispidula. Among them, compounds 5, 7 and 8 were isolated from Nigella for the first time. Their structures were elucidated with HR-ESI-MS, 1D and 2D NMR spectra. Evaluation of the isolated compounds on protein tyrosine phosphatase (PTP1B) assay indicated that although compounds 2–8 show no promising anti-PTP1B activities, compound 1 possess anti-PTP1B activity with an IC₅₀ value of 7.38 ± 0.14 μM in vitro.