Fatty acids, Part 33 The synthesis of all the octadecynoic acids and all the trans-octadecenoic acids

2-Octadecynoic acid as a dual life stage inhibitor of Plasmodium infections and plasmodial FAS-II enzymes

The malaria parasite Plasmodium goes through two life stages in the human host, a non-symptomatic liver stage (LS) followed by a blood stage with all clinical manifestation of the disease. In this study, we investigated a series of 2-alkynoic fatty acids (2-AFAs) with chain lengths between 14 and 18 carbon atoms for dual in vitro activity against both life stages. 2-Octadecynoic acid (2-ODA) was identified as the best inhibitor of Plasmodium berghei parasites with ten times higher potency (IC50=0.34 μg/ml) than the control drug. In target determination studies, the same compound inhibited three Plasmodium falciparum FAS-II (PfFAS-II) elongation enzymes PfFabI, PfFabZ, and PfFabG with the lowest IC50 values (0.28-0.80 μg/ml, respectively). Molecular modeling studies provided insights into the molecular aspects underlying the inhibitory activity of this series of 2-AFAs and a likely explanation for the considerably different inhibition potentials. Blood stages of P. falciparum followed a similar trend where 2-ODA emerged as the most active compound, with 20 times less potency. The general toxicity and hepatotoxicity of 2-AFAs were evaluated by in vitro and in vivo methods in mammalian cell lines and zebrafish models, respectively. This study identifies 2-ODA as the most promising antiparasitic 2-AFA, particularly towards P. berghei parasites.

In Vivo Studies of Dialkynoyl Analogues of DOTAP Demonstrate Improved Gene Transfer Efficiency of Cationic Liposomes in Mouse Lung

A novel set of dialkynoyl analogues of the cationic, gene delivery lipid DOTAP (1) was synthesized. Structure-activity studies demonstrate that replacement of the cis-double bonds of DOTAP with triple bonds in varying positions alters both the physical properties of the resultant cationic liposome-DNA complexes and their biological functionalities, both in vitro and in vivo. Particularly, in vivo studies demonstrate that pDNA transfection of mouse lung endothelial cells with lead analogue DS(14-yne)TAP (4):cholesterol lipoplexes exhibits double the transfection level with less associated toxicity relative to the well-established DOTAP:cholesterol system. In fact, 4:cholesterol delivers up to 3 times the dose of pDNA in mice than can be tolerated by DOTAP, leading to nearly 3 times greater marker-gene expression. X-ray diffraction studies suggest that lipoplexes containing analogue 4 display increased stability at physiological temperatures. Our results thus suggest that analogue 4 is a potentially strong candidate for the gene therapy of lung tumors.

Iron Carbonyl-Promoted Isomerization of Olefin Esters to Their alpha,beta-Unsaturated Esters: Methyl Oleate and Other Examples

Ultraviolet photolysis of stoichiometric amounts of methyl oleate and Fe(CO)(5) in hexanes solvent at 0 degrees C gives Fe(CO)(3)(eta(4)-alpha,beta-ester) in which the alpha,beta-unsaturated ester isomer of methyl oleate is stabilized by eta(4)-oxadiene pi coordination of the olefin and ester carbonyl groups to the Fe(CO)(3) unit. Treatment of the Fe(CO)(3)(eta(4)-alpha,beta-ester) with pyridine or CO liberates the free alpha,beta-ester, methyl octadec-trans-2-enoate, in 70% yield. The Fe(CO)(3) unit both catalyzes the olefin isomerization and stabilizes the alpha,beta-unsaturated ester, which results in the formation of the alpha,beta-ester in a yield far above that (3.5%) observed for simple catalyzed methyl oleate isomerization. The much smaller olefin esters, methyl 3-butenoate and ethyl 4-methyl-4-pentenoate, are isomerized under the same conditions to their alpha,beta-unsaturated esters in 94 and 90% yields, respectively. The effects of reaction conditions on the yield, the use of Fe(CO)(3)(cis-cyclooctene)(2) as a nonphotolytic catalyst, and the mechanism of this useful synthetic process are discussed.

Properties of unusual phospholipids: I. Synthesis, monolayer investigations and calorimetry of diacylglycerophosphocholines containing monoacetylenic acyl chains

Isomeric diacylglycerophosphocholines containing various octadecynoic acids (4-, 6-, 9-, 12-, 14- and 17-octadecynoic acid) were synthesized and purified to homogeneity. Their behaviour in monolayers, when studied by the Langmuir-Blodgett film balance technique, revealed systematic relationships between structure and packing properties. The thermotropic phase behaviour of these novel phospholipids, as measured by differential scanning calorimetry, depended in a systematic fashion on the position of the triple bond: the gel-to-liquid-crystalline phase transition temperature (Tm) passed through a minimum of -3.4 degrees C for a triple bond in position 9.

Synthesis of octadecynoic acids and [1-14C] labeled isomers of octadecenoic acids

Geometric and positional isomers of [1-14C] octadecenoic acids have been synthesized by modifications of published procedures. Positional isomers of octadecynoic acids also have been synthesized to obtain the geometric and positional isomers of the unlabeled octadecenoic acid analogs. The syntheses were accomplished by coupling a haloalkyl compound with a substituted acetylene using n-butyl lithium in hexamethylphosphoramide. The coupled product, either a 17- or 18-carbon acetylenic alcohol, could be semihydrogenated and chain extended to afford a carboxy labeled derivative, could be partially hydrogenated and chain extended to afford a carboxyl labeled cis- or trans-octadecenoic acid in the former case. In the latter case, octadecynoic, cis-octadecenoic or trans-octadecenoic acids could be obtained by the appropriate reactions. The methods used in this study enabled the synthesis of 14C-labeled fatty acids in generally higher yields and by simpler reactions than were previously possible.

Desaturation of positional and geometric isomers of monoenoic fatty acids by microsomal preparations from rat liver

A range of cis- and trans-monoenoic fatty acids was tested as substrates for desaturation in microsomal preparations from rat liver. Trans-monoenoic acids were generally desaturated in the delta 9 position to the same extent as stearic acid. Acids with delta 7-trans- and delta 11-trans-olefinic unsaturation produced delta 7-trans, 9-cis- and delta 9-cis, 11-trans-conjugated dienoic acids, respectively, but the delta 8-trans-and delta 10-trans-monoenoic acids did not give delta 8,9- or delta 9,10-allenes. Of the cis-monoenoic acids examined, only those with double bonds at or beyond the delta 14 position gave any measurable delta 9 desaturation. When delta 9 desaturation of long chain saturated acids was inhibited by adding sterculic acid, these saturated acids were desaturated at the delta 5 and delta 6 positions. Many of the monoenoic acids tested were also desaturated at the delta 5 and/or delta 6 positions, although the percentage conversions were always low. delta 9-cis, 11-trans-, delta 9-cis, 12-trans- and delta 9-cis, 13-trans-dienoic acids, produced in situ by delta 9 desaturation of the corresponding monoenoic acids, were extensively desaturated in the delta 6 position. These results are discussed in terms of: (a) the various models proposed to explain the substrate specificities of the desaturases, and (b) the metabolism of unnatural fatty acids ingested from dietary sources.

Quantitative effects of unsaturated fatty acids in microbial mutants. VII. Influence of the acetylenic bond location on the effectiveness of acyl chains

The ability of a series of 18 carbon acetylenic fatty acids to fulfill the unsaturated fatty acid requirements of Escherichia coli and Saccharomyces cerevisiae was investigated. Despite their high melting points (greater than 40 degrees C), several isomers of the acetylenic fatty acids were as efficient or more efficient in supporting growth than the analogous fatty acid having a cis-double bond. The efficiencies of the different positional isomers in supporting cell proliferation varied from essentially 0 cells per fmol for the 2-5 and 13-17 isomers to high values when the acetylenic bond was near the center of the chain: e.g. 45 E. coli and 5.5 S. cerevisiae cells/fmol for the 10 isomer. A striking ineffectiveness of the 9 isomer was observed with E. coli. The 7, 8 and 10 isomers were at least 10-fold more efficient than any of the other positional isomers in supporting the growth of E. coli. In contrast, the 9 isomer was among the most effective acetylenic fatty acids tested with the yeast mutant. Chromatographic analysis of the extracted lipids indicated that each of the acetylenic isomers tested (except delta2 and delta3) could be esterified by the prokaryotic and eukaryotic microorganisms. The content of unsaturated plus cyclopropane acids observed when growth ceased in E. coli cultures supplemented with growth-limiting concentrations of the acetylenic fatty acids ranged from approx. 15 mol% for the 8 isomer to approx. 35 mol% for the 14 and 17 isomers. The 8-11 isomers were observed to be esterified predominantly at the two position in phosphatidylethanolamine of E. coli and in phosphatidylcholine of S. cerevisiae.

Fatty acids. Part 48. 13C nuclear magnetic resonance studies of acetylenic fatty acids

The 13C NMR spectra of thirty-seven alkynoic acids (C8-C18) and ten alkadiynoic acids (C18 and C20) are reported and interpreted. The influence of COOH, COOCH3, CH3, and C identical to C groups on the chemical shifts of nearby carbon atoms is assessed. These influences are largely additive so that available spectra are readily interpreted and the spectra of new compounds of this type can be predicted. These preliminary results indicate that 13C NMR spectroscopy should be of considerable value in the structural identification of acetylenic compounds.

Mass spectra of acetylenic fatty acid methyl esters and derivatives

A series of isomeric methyl octadecynoates was analyzed by mass spectrometry; each isomer gave a unique spectrum. The characteristic ions were those resulting from a McLafferty rearrangement of the allenic sites or of the already-rearranged allenic sites. The acetylenic esters were also subjected to oxymercuration whereupon a carbonyl group was formed at either of the original actylenic carbon atoms providing two oxostearates. Further reaction with NaBH4 formed hydroxy esters which, after silylation, gave diagnostic mass spectra indicative of the triple bond location. Applied to esters with both double and triple bonds, this procedure permitted differentiation between the two types of unsaturation. Methoxyl groups marked the original double bond locations and hydroxyls did so for triple bonds.

The PMR analysis of non-conjugated alkenoic and alkynoic acids and esters

The 220 MHz PMR spectra of 143 non-conjugated alkenoic and alkynoic acids and esters are correlated so as to provide a method for the structural analysis of such compounds in general. The spectral data are explained in terms of long-range deshielding of the double bonds, triple bonds, acid and ester groups in the molecules, and parameters are derived to quantify the influence of these groups on the chemical shifts of methyl and methylene protons up to six carbon atoms distant along an alkyl chain. It is shown that, by the application of these parameters, 220 MHz PMR spectroscopy can be used to determine both the stereochemistry and position of double bonds, and the position of triple bonds, in the majority of fatty acids and esters. The 2- to 9- and 13- to 17-cis- and trans-isomers of octadecenoic acid may be readily idenfited in this way, whilst for the octadecynoic acids all positional isomers may be characterized. Examples are also given of the structural analysis of several polyenoic compounds, including methyl cis-5, cis-8, cis-11, cis-14, cis-5, cis-8, cis-11, trans-14, and trans-5, cis-8, cis-11, cis-14-eicosatetraenoates, and methyl trans-5, cis-9, cis-12-octadecatrienoate.