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Fürstner Alois - - 2003
A concise total synthesis of citreofuran 4 is described, a structurally unique octaketide derivative belonging to the curvularin family. Key steps involve the elaboration of orsellinic acid methyl ester 5 to acid 14, which converts, on attempted formation of the corresponding acid chloride, to the 3-alkoxyisocoumarin derivative 20. This heterocycle ...
Reichwein John F - - 2003
Treatment of nonstabilized beta-hydroxy phosphonic acid mono methyl esters with diisopropyl carbodiimide at ambient temperature leads to clean stereospecific elimination. The phosphonic acid mono alkyl esters are accessible by the selective partial saponification of dimethyl or diethyl alkyl phosphonates with NaOH or MgBr(2). Isolated yields over both hydrolysis and elimination ...
Raku T - - 2003
To improve trehalose lipophilicity, trehalose was regioselectively esterified with vinyl fatty acid esters in dimethyl formamide by protease from Bacillus subtilis to give 6-O-lauroyltrehalose, 6-O-myristoyltrehalose, 6-O-palmitoyltrehalose, 6-O-stearoyltrehalose, 6-O-oleoyltrehalose and 6-O-linoleoyltrehalose. The influence of structural variation by changing fatty acid substitute was examined by measurement of the surface tension and biodegradability.
Dardonville Christophe - - 2003
The synthesis of (2R)-2-methyl-4,5-dideoxy and (2R)-2-methyl-4-deoxy analogues of 6-phosphogluconate is described. The synthetic strategy relies on the Evans aldol reaction for the installation of the chiral centres in the 2- and 3-positions. The selective phosphorylation at the primary alcohol function of (2R,3S)-3,6-dihydroxy-2-methylhexanoic acid benzyl ester (5) and (2R,3S,5S)-3,5,6-trihydroxy-2-methylhexanoic acid benzyl ...
Tsikas Dimitrios - - 2003
Oleic acid, cis-9-octadecenoic acid, is the major fatty acid in mammals. Its oxide, cis-9,10-epoxyoctadecanoic acid (cis-EODA), has been identified in blood and urine of humans, its origin is, however, still unknown. Lipid peroxidation and enzyme-catalyzed epoxidation of oleic acid are two possible sources. In the present article, we investigated by ...
Scalabrino Gaia - - 2003
Synthesis of (1R,5R,6R)-2-(6-hydroxymethyl-5-isopropyl-2-methylcyclohex-2-enyl)-N- methoxy-N-methylacetamide 8 from R-(-)-phellandrene in six steps, and (3aR*,4S*,6R*,6aS*)- (6-hydroxymethyl-4-methoxy-2,2,6-trimethyltetrahydrofuro[3,4-d][1,3]dioxol- 4-yl)acetic acid methyl ester 17 from tetrabromoacetone and 2-methoxy-5-methylfuran in six steps, provided two key fragments which have been combined to produce intermediates for attempted construction of the basic skeleton of eleutherobin.
Temeriusz Andrzej - - 2003
The syntheses of new oxamide derivatives of methyl 2-amino-2-deoxy-alpha-D-glucopyranoside and amino acid or peptide esters are presented. The reaction of methyl 3,4,6-tri-O-acetyl-2-acetamido-2-deoxy-alpha-D-glucopyranoside and oxalyl chloride gave N-(methyl 3,4,6-tri-O-acetyl-2-deoxy-alpha-D-glucopyranosid-2-yl) oxamic acid chloride which on reaction with the ester of Gly, L-Ala, L-Phe, GlyGly, Gly-L-Phe and Gly-L-Ala afforded N-(methyl 3,4,6-tri-O-acetyl-2-deoxy-alpha-D-glucopyranosid-2-yl), N'-oxalyl-amino acid ...
Li Wenkui - - 2003
Analysis of two commercial extracts of Andrographis paniculata using high-performance liquid chromatography (HPLC) with photodiode array absorbance detection showed the presence of several unexpected compounds, which were isolated and identified as methyl, ethyl, and propyl esters of p-hydroxybenzoic acid by using high-resolution mass spectrometry and nuclear magnetic resonance. Quantitative analysis ...
Krugliak Miriam - - 2003
Esters of amino acids are known to penetrate into cells by simple diffusion. Subsequently, they are hydrolyzed by hydrolases to release the parent amino acid. Due to the abundance of hydrolases in phagolysosomes, amino acids accumulate, there because the rate of influx and hydrolysis exceed the rate of amino acid ...
Pietzsch Jens - - 2003
N(O,S)-ethoxycarbonyltrifluoroethyl amino acid esters are formed by the reaction of amino acids with ethylchloroformate plus trifluoroethanol plus pyridine. The use of these derivatives for a rapid and sensitive determination of 3-chlorotyrosine, a highly specific marker of myeloperoxidase-catalyzed protein oxidation, by using standard gas chromatography/electron impact mass spectrometry, is discussed.
Olson Edwin S - - 2003
Bench-scale research demonstrated that using an efficient esterification step to integrate an ethanol with a carboxylic acid fermentation stream offers potential for producing valuable ester feedstocks and fuels. Polar organic acids from bacterial fermentations are difficult to extract and purify, but formation of the ammonium salts and their conversion to ...
Rontani J-F - - 2003
The electron ionization (EI) mass spectra of saturated and alpha,beta-unsaturated C(19) isoprenoid aldehydes and carboxylic acid methyl and trimethylsilyl esters are reported. Different pathways are proposed in order to explain the main fragmentations observed. The conjugated double bond migrates more or less readily before gamma-hydrogen rearrangement according to the structure ...
Kurkiewicz Slawomir - - 2003
A single-step method suitable for cellular fatty acid derivatization to picolinyl esters with the use of a pyrolyzer as a thermochemical micro-reactor was developed for whole bacterial cells. This reduced the preparation time from several hours to less than two minutes. In addition, the minimal bacterial mass required for analysis ...
Best Catherine A - - 2003
This report describes the biochemistry of fatty acid ethyl esters (FAEE), non-oxidative metabolites of ethanol, and their clinical significance. We review information regarding the enzymes responsible for FAEE synthesis and degradation, and the mechanisms involved with the intracellular and extracellular transport of FAEE and FAEE-mediated cytotoxicity. Also a summary of ...
Kaphalia Bhupendra S - - 2003
Formation of fatty acid ethyl esters (FAEEs, catalyzed by FAEE synthase) has been implicated in the pathogenesis of chronic pancreatitis. In previous studies, we demonstrated that FAEE synthase, purified from rat liver microsomes, is identical to rat liver carboxylesterase (pI 6.1), and structurally and functionally different than that from pancreas. ...
Wellendorph Petrine - - 2003
A general, improved procedure for rapid synthesis of philanthotoxin analogues, a pharmacologically important class of polyamine conjugates, is described. The solution-phase procedure is illustrated by gram-scale synthesis of philanthotoxins PhTX-343 and PhTX-12. Selectively protected polyamines are coupled to N(alpha)-Fmoc-protected amino acid pentafluorophenyl esters. After removal of the N(alpha)-Fmoc group, the ...
Leal Walter S - - 2003
Three amino acid-derived compounds were identified in extracts from the pheromone glands of the scarab beetle Phyllophaga elenans, i.e., L-isoleucine methyl ester (LIME), N-formyl L-isoleucine methyl ester (For-LIME), and N-acetyl L-isoleucine methyl ester (Ac-LIME). The compounds were characterized from their spectral data (MS and IR), confirmed by synthesis, and their ...
Stephens P J - - 2003
Ab initio Density Functional Theory (DFT) calculations of transparent spectral region, discrete frequency specific rotations were used to assign the absolute configurations (ACs) of: 1, 2H-naphtho[1,8-bc]thiophene 1-oxide; 2, m-F-phenyl glycidic acid methyl ester; 3, o-Br-phenyl glycidic acid methyl ester; 4, p-CH(3)-phenyl glycidic acid methyl ester; 5, 2-(1-hydroxyethyl)-chromen-4-one; and 6, 6-Br-2-(1-hydroxyethyl)-chromen-4-one. ...
Zhang Xini - - 2002
The standard method for preparing carboxylic acid hydrazides is hydrazinolysis of esters in alcoholic solutions. However, when applied to alpha,beta-unsaturated esters, the main product typically is the pyrazolidinone resulting from an undesired Michael-type cyclization. Other alternative methodologies reported for direct preparation of hydrazides from acids are inefficient. We developed an ...
Chen Ping - - 2002
Epigallocatechin-3-O-gallate (EGCG) was modified by catalytic esterification with hexadecanoyl chloride. A long-chain fatty acid ester derivative was obtained from the purification of this reaction product by high-speedcounter-current chromatography using a solvent system composed of n-hexane-ethyl acetate-methanol-water (1:1:1:1, v/v). The structure of the derivative, epigallocatechin-3-O-gallate-4'-hexadecanate, was elucidated by IR, MS and ...
Musshoff Frank - - 2002
The development in chromatographic methods for the determination of markers of alcohol consumption is summarized in this review. The markers included in this article are ethanol in body fluids, ethanol congeners, fatty acid ethyl esters (FAEEs), ethyl glucuronide (EtG), cocaethylene (CE), carbohydrate-deficient transferrin (CDT), phosphatidylethanol (PEth), 5-hydroxytryptophol (5-HTOL), dolichol, ketone ...
Blatrix Rumsaïs - - 2002
Dufour's gland is the origin of the trail pheromone of Gnamptogenys striatula. Chemical analysis of the glandular extracts revealed a series of new natural products, especially esters of (2E)-3,4,7-trimethyl-2,6-octadien-1-ol (4-methylgeraniol), and (2E)-3,4,7-trimethyl-2,6-nonadien-1-ol (a bishomogeraniol isomer) with medium-chain fatty acids. Bioassays with synthetic racemates of the esters revealed that the 4-methylgeranyl ...
Guan Ziqiang - - 2002
Electron capture dissociation (ECD) has been demonstrated to be an effective fragmentation technique for characterizing the site and structure of the fatty acid modification in ghrelin, a 28-residue growth-hormone-releasing peptide that has an unusual ester-linked n-octanoyl (C8:0) modification at Ser-3. ECD cleaves 21 of 23 possible backbone amine bonds, with ...
Juzeniene A - - 2002
5-Aminolevulinic acid (ALA) and two of its esters were studied in cells in vitro and in vivo on skin of healthy hairless mice. In vitro, both esters, which are more lipophilic than ALA, induced higher PpIX fluorescence at lower concentrations compared with ALA. In vivo, ALA induced PpIX fluorescence more ...
Schreiner Erwin P - - 2002
A two-step protocol for the first chemoselective cleavage of 2-hydroxy acid amides has been developed. Mesylation of the model substrate 2-(hydroxypropionylamino)-4-methylpentanoic acid methyl ester (11) followed by treatment with N-ethylthiourea (13) allows cleavage of 2-hydroxy acid amides under smooth conditions. Successful application of this methodology to the open-chain transesterification product ...
Tindall G William - - 2002
The properties of mixed cellulose esters are strongly affected by the nature and ratio of acid substituents. Fast reliable methods are needed to determine the acid substituents of these products. For some applications it is necessary to also determine the unesterified hydroxyl content. A generally applicable method has been developed ...
Gallart Magdalena - - 2002
The influence of fatty acids (free and bound as ethyl esters) on wine foaming was studied in different white wines and the corresponding sparkling wines. Moreover, from three of these wines the foam formed by CO(2) injection was separated, and two fractions were then obtained: foam wine (FW) and remainder ...
Thomas Jeffrey - - 2003
Fenofibrate is clinically successful in treating hypertriglyceridemia and mixed hyperlipidemia presumably through peroxisome proliferator-activated receptor alpha (PPARalpha)-dependent induction of genes that control fatty acid beta-oxidation. Lipid homeostasis and cholesterol metabolism also are regulated by the nuclear oxysterol receptors, liver X receptors alpha and beta (LXRalpha and LXRbeta). Here we show ...
Slaitas A - - 2002
This study towards the development of sulfurane-based coupling agents shows that bis-[alpha,alpha-bis(trifluoromethyl)-benzyloxy]diphenylsulfur (BTBDS) can facilitate rapid amide bond formation between Nalpha-urethane-protected l-amino acids and l-phenylalanine ethyl ester in the absence of an external base. The corresponding dipeptide esters were obtained in excellent yields and with no detectable racemization, as judged ...
Nuissier Gladys - - 2002
Wastes produced during fermentation and distillation of crude sugarcane juice in rum factories were evaluated as a new source of waxes. The chemical composition of the crude wax extracted from adsorbat of the wastes on fuller's earth was studied by GC-mass spectrometry. Series of linear alkanes (C19-C33), and wax esters ...
Falkiewicz Bogdan - - 2002
PNA type I monomer backbone with a reduced peptide bond was synthesized on a Merrifield resin in Mitsunobu reaction of Boc-aminoethanol with resin-bound o-nitrobenzenesulfonylglycine. The pseudodipeptide secondary amine group was deprotected by thiolysis and acylated with thymin-1-ylacetic acid. The monomer was released as a methyl ester. The procedure seems to ...
Klán Petr - - 2002
2,5-Dimethylphenacyl phosphoric and sulfonic esters release the corresponding acids upon irradiation in nearly quantitative isolated yields, with quantum yields phi = 0.71 and 0.68 in methanol, 0.09 and 0.19 in benzene. In methanol solution the reactions proceed predominantly via the (Z)-photoenol, the lifetimes of which (20 and 25 micros) were ...
Prinz Sonja - - 2002
Abietic acid (1) and its methyl ester (2) were investigated under various storage conditions to provide an indication of their preferred oxidation mechanisms and to investigate the most susceptible positions for modification in the abietane skeleton. Six known compounds, methyl 7alpha,13beta-dihydroxyabiet-8(14)-enoate (4a), methyl 7alpha,13alpha-dihydroxyabiet-8(14)-enoate (4b), methyl 12-oxoabietate (6), methyl 7-oxodehydroabietate ...
Jetter Reinhard - - 2002
The cuticular wax of Taxus baccata L. needles was found to contain four different classes of long-chain esters that were identified by various chemical transformations with product assignment employing GC-MS. Homologous series of (1) 3-(4'-hydroxyphenyl)-propyl esters of C(20)-C(36) fatty acids, (2) 4-(4'-hydroxyphenyl)-2-butyl esters of C(18)-C(28) fatty acids, (3) 3-(3',4'-dihydroxyphenyl)-propyl esters ...
Dorta Enrique - - 2002
Three new terpenoids, 1a-3a, and the known metabolites atomaric acid, stypoquinonic acid, and 5'a-desmethyl-5'-acetylatomaric acid have been isolated from the tropical brown alga Stypopodium zonale. The structures and relative stereochemistry of the methyl ester of 1a-3a were determined by spectral methods. The methyl ester of 3a exhibits in vitro cytotoxic ...
Kunze Carmen - - 2002
Salicylic and acetylsalicylic acid esters were tested as plasticizers for biodegradable poly(3-hydroxybutyrate) (PHB). The aim is the combination of plasticizing and anti-inflammatory properties in the fabrication of implant materials. Solution-cast films made of mixtures of PHB and 30% ester showed plasticization accompanied by a decrease of elastic modulus and an ...
Baraniak Janina - - 2002
A method of highly efficient synthesis of N- and O-phosphorothioylated amino acids was developed. N- and O-(2-Thiono-1,3,2-oxathiaphospholanyl)amino acid methyl esters (3) were prepared in high yields in reaction of amino acid methyl esters with 2-chloro-1,3,2-oxathiaphospholane in pyridine in the presence of elemental sulfur. Compounds 3 were converted in high yield ...
Hin Bunda - - 2002
Treatment of 5-monosubstituted Meldrum's acids with dimethylmethyleneimmonium iodide (Eschenmoser's iodide salt) in methanol gives alpha-substituted acrylate methyl esters in good yields. Easy access to 5-monosubstituted Meldrum's acids allowed us to synthesize a wide variety of alpha-substituted acrylate methyl esters. The reaction conditions are mild and tolerate many functional groups commonly ...
Chang Michelle C Y - - 2002
We describe a general method for the unimolecular photochemical generation of tyrosyl radicals from a diaryl oxalate ester platform on the nanosecond time scale. Symmetric and asymmetric tyrosine oxalate esters have been prepared in gram quantities. Direct photocleavage of the oxalate linkage by laser flash photolysis affords tyrosyl radicals within ...
Huang Xian - - 2002
An efficient method for the preparation of polymer-bound cyclic malonic acid ester starting from Merrifield resin has been developed. Reaction of the resin-bound cyclic malonic acid ester with triethyl orthoformate and subsequent double substitution with nucleophilic reagents, such as arylamine, urea, thiourea, 2-aminobenzothiazoles, or isothiosemicarbazones, afforded the corresponding polymer-bound substituted ...
Jover Eric - - 2002
Steryl esters occurring in lanolin have been characterised by sub-ambient pressure gas chromatography coupled to mass spectrometry. Electron impact and chemical ionisation modes with different reagent gases have been evaluated in order to carry out unambiguous peak identification. Steryl esters with different sterol (i.e. cholesterol, lanosterol and dihydrolanosterol) and acid ...
Laposata Michael - - 2002
Fatty acid ethyl esters (FAEE), esterification products of fatty acids and ethanol, have been shown to be mediators of ethanol-induced cell injury and their presence in the blood and tissues is a marker of ethanol intake. Recently, it has been shown that FAEE are produced within seconds of infusion of ...
Pérez Ana G - - 2002
The fate of amino acids in relation to aroma biogenesis was studied in strawberries using the in vitro growth approach. This fruit presented differences in the level of metabolization for different amino acids. Incubations of strawberries with L-isoleucine gave rise to an increase of fourteen compounds in this fruit aroma, ...
Vale Paulo - - 2002
A new outbreak of human diarrhoeic poisonings (DSP) with esters of okadaic acid (OA) was confirmed after ingestion of razor clams (Solen marginatus) harvested at Aveiro lagoon (NW Portugal) in the summer of 2001. Accumulation of marine toxins in second order consumers was investigated in the edible parts of a ...
Kim Sang-In - - 2002
Two new benzofurans, 5,6-dihydroxybenzofuran-2,3-dicarboxylic acid dimethyl ester (kynapcin-13) and 5,6,5',6'-tetrahydroxy[3,3']bibenzofuranyl-2,2'-dicarboxylic acid 2'-methyl ester (kynapcin-28) were isolated from Polyozellus multiplex, and shown to non-competitively inhibit prolyl endopeptidase (PEP), with the IC50 values of 76.80 and 0.98 microM, respectively. Kynapcin-13 and -28 were less inhibitory to other serine proteases such as chymotrypsin, ...
Fujita Takuma - - 2002
The enantioresolution method using (S)-(+)-2-methoxy-2-(1-naphthyl)propionic acid (MalphaNP acid 1) was applied to 1,2,3,4-tetrahydro-4-phenanthrenol (4). Racemic alcohol (+/-)-4 was esterified with (S)-(+)-1, and a diastereomeric mixture of esters formed was separated by HPLC on silica gel giving the first-eluted ester 5a and the second-eluted one 5b. Ester 5a was reduced with ...
Chen Jian-Xin - - 2002
Esters of three types of silylated alpha-amino acids have been prepared from appropriate zirconaaziridines. Slow addition (syringe pump) of the (R,R) carbonate of trans-stilbene gave metallacycles with the maximum possible diastereomeric excess (as determined by the diastereomeric excess produced by the Hoffmann test-the same reaction but with racemic carbonate). Methanolysis ...
Qian M - - 2002
The volatile compounds in Parmigiano-Reggiano cheese were isolated by solvent extraction/high vacuum distillation, followed by separation into acidic, basic, water-soluble, and neutral fractions. The neutral fraction was further fractionated by a normal-phase liquid chromatography. Aroma compounds were identified using gas chromatography/Osme-mass spectrometry and confirmed with retention index of standards. Butanoic, ...
Valencia-Islas Norma - - 2002
Bioassay-guided fractionation of a phytotoxic extract of Prionosciadium watsoni led to the isolation of three new pyranocoumarins and two pyranochromones. The new compounds were characterized as propionic acid (9R,10R)-9-acetoxy-8,8-dimethyl-9,10-dihydro-2H,8H-benzo[1,2-b:3,4-b']dipyran-2-one-10-yl ester (1), isobutyric acid (9R,10R)-9-hydroxy-8,8-dimethyl-9,10-dihydro-2H,8H-benzo[1,2-b:3,4-b']dipyran-2-one-10-yl ester (2), isobutyric acid (9R)-8,8-dimethyl-9,10-dihydro-2H,8H-benzo[1,2-b:3,4-b']dipyran-2-one-9-yl ester (10), 2-methylbut-(2Z)-enoic acid (3R)-5-methoxy-3,4-dihydro-2,2,8-trimethyl-6-oxo-2H,6H-benzo[1,2-b:5,4-b']dipyran-3-yl ester (11), and isobutyric acid (3R)- ...
Iwata Arihiro - - 2002
Ring-opening halosilation of lactones with two types of reagents, Et(3)SiH/MeI(PdCl(2)) (1a) and Et(3)SiH/AllylBr(PdCl(2)) (1b), was studied. Cyclic esters such as gamma-butyrolactones, delta-valerolactone, and 6-hexanolide reacted with 1 equiv of 1a,b to give triethylsilyl omega-iodo- and omega-bromoalkanoates in good yields. Reaction of an acyclic ester, methyl benzoate, with 1a afforded triethylsilyl ...
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