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To develop highly efficient and low cost acaricides, a series of 2,4-diphenyl-1,3-oxazolines containing an ether moiety at the

The biological impact of ether glycerophospholipids (GP) in peroxisomal disorders and other diseases makes them significant targets as biomarkers for diagnostic assays or deciphering pathology of the disorders. Ether lipids include both plasmanyl and plasmenyl lipids, which each contain an ether or a vinyl ether bond at the

Aqueous-liquid crystal (LC) interfaces offer promise as responsive interfaces at which biomolecular recognition events can be amplified into macroscopic signals. However, the design of LC interfaces that distinguish between specific and non-specific protein interactions remains an unresolved challenge. Herein we report the synthesis of amphiphilic monomers, dimers and trimers conjugated to sulfonamide ligands via triazole rings, their assembly at aqueous-LC interfaces, and the orientational response of LCs to the interactions of carbonic anhydrase II (CAII) and serum albumin with the oligomer-decorated LC interfaces. Of six oligomers synthesized, only dimers without amide methylation were found to assemble at aqueous interfaces of nematic 4-cyano-4’-pentylbiphenyl (5CB) to induce perpendicular LC orientations. At dimer-decorated LC interfaces, we found that concentrations of CAII less than 4 μM did not measurably perturb the LC but prevented non-specific adsorption and penetration of serum albumin into the dimer-decorated interface that otherwise triggered bright, globular LC optical domains. These experiments and others (including competitive adsorption of CAII, BSA and lysozyme) support our hypothesis that specific binding of CAII to the dimer prevents LC anchoring transitions triggered by non-specific adsorption of serum albumin. We illustrate the utility of the approach by reporting (i) the relative activity of two small molecule inhibitors (6-ethoxy-2-benzothiazolesulfonamide and benzenesulfonamide) of binding of CAII to sulfonamide, and (ii) proteolytic digestion of a protein (CAII) by thermolysin. Overall, the results in this paper provide new insight into the interactions of proteins at aqueous-LC interfaces and fresh ideas for either blocking non-specific interactions of proteins at surfaces or reporting specific binding events at LC interfaces in the presence of non-specific proteins.

Enzymatic digestion of complex protein samples is often performed by use of multiple proteases to improve protein identification and characterization. Combining trypsin with ArgC is one option to enhance sequence coverage in bottom-up proteomics. However, the low selectivity of this endoprotease derogates from the benefit of the combination. Our approach here is to mimic ArgC digestion by chemically modifying all lysine residues in proteins so that trypsin can only cleave C-terminal to arginine. Four different amine modifications, dimethylation, acetylation, propionylation, and carbethoxylation, were tested, and the protocols were optimized. A nearly complete conversion of the primary amines was achieved for all modifications. Tryptic digestion of Escherichia coli lysate proteins after acylation of lysine residues shows the most significant improvement compared with data received from ArgC digest. After propionylation, 9216 unique peptides identified 1439 proteins, which, compared with a conventional tryptic digestion, represents the identification of 150 additional proteins due to a reasonable reduction of the sample complexity and higher fragmentation efficiencies of the peptides. It is therefore concluded that the Arg-C like digestion should no longer be regarded as a complementary approach but forms a viable and superior alternative to the conventional trypsin digestion.

Nanoparticles (NPs) have received much attention in recent years for their diverse potential biomedical applications. However, the synthesis of NPs with desired biodistribution and pharmacokinetics is still a major challenge, with NP size and surface chemistry being the main factors determining the behavior of NPs in vivo. Here we report on the surface chemistry and in vitro cellular uptake of magnetic iron oxide NPs coated with zwitterionic dopamine sulfonate (ZDS). ZDS-coated NPs were compared to similar iron oxide NPs coated with PEG-like 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (MEEA) to investigate how surface chemistry affects their in vitro behavior. ZDS-coated NPs had a very dense coating, guaranteeing high colloidal stability in several aqueous media and negligible interaction with proteins. Treatment of HepG2 cells with increasing doses (2.5-100 mug Fe/mL) of ZDS-coated iron oxide NPs had no effect on cell viability and resulted in a low, dose-dependent NP uptake, inferior than most reported data for the internalization of iron oxide NPs by HepG2 cells. MEEA-coated NPs were scarcely stable and formed micrometer-sized aggregates in aqueous media. They decreased cell viability for dose >=50 mug Fe/mL, and were more efficiently internalized than ZDS-coated NPs. In conclusion, our data indicate that the ZDS layer prevented both aggregation and sedimentation of iron oxide NPs and formed a biocompatible coating that did not display any biocorona effect. The very low cellular uptake of ZDS-coated iron NPs can be useful to achieve highly selective targeting upon specific functionalization.

Although the uniform initial hydroxylation of methyl tert-butyl ether (MTBE) and other oxygenates during aerobic biodegradation has already been proven by molecular tools, variations in carbon and hydrogen enrichment factors (ε(C) and ε(H)) have still been associated with different reaction mechanisms (McKelvie et al. Environ. Sci. Technol. 2009, 43, 2793-2799). Here, we present new laboratory-derived ε(C) and ε(H) data on the initial degradation mechanisms of MTBE, ethyl tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME) by chemical oxidation (permanganate, Fenton reagents), acid hydrolysis, and aerobic bacteria cultures (species of Aquincola, Methylibium, Gordonia, Mycobacterium, Pseudomonas, and Rhodococcus). Plotting of Δδ(2)H/ Δδ(13)C data from chemical oxidation and hydrolysis of ethers resulted in slopes (Λ values) of 22 ± 4 and between 6 and 12, respectively. With A. tertiaricarbonis L108, R. zopfii IFP 2005, and Gordonia sp. IFP 2009, ε(C) was low (|-1|‰) and ε(H) was insignificant. Fractionation obtained with P. putida GPo1 was similar to acid hydrolysis and M. austroafricanum JOB5 and R. ruber DSM 7511 displayed Λ values previously only ascribed to anaerobic attack. The fractionation patterns rather correlate with the employment of different P450, AlkB, and other monooxygenases, likely catalyzing ether hydroxylation via different transition states. Our data questions the value of 2D-CSIA for a simple distinguishing of oxygenate biotransformation mechanisms, therefore caution and complementary tools are needed for proper interpretation of groundwater plumes at field sites.

In this paper, a theoretical study of 1,2-dimethoxyethane (DME) and 1,2-dimethoxypropane (DMP) at water/n-heptane and 1,2-dimyristoyl-sn-glycero-3- phospatidycholine (DMPC) lipid bilayer/water interfaces using the umbrella sampling method is reported. Recently proposed GROMOS96/OPLS compatible models for DME and DMP have been used for the simulation studies. The percolation free energy barrier of one DME and DMP molecule from water to n-heptane phase calculated using the umbrella sampling method turned out to be equal to ∼18.5 kJ/mol and ∼6 kJ/mol, respectively. In the case of the DMPC lipid bilayer, overall free energy barriers of ∼20 kJ/mol and ∼12 kJ/mol were obtained for DME and DMP, respectively. The spontaneous diffusion of DME and DMP in the lipid bilayer has also been investigated using unconstrained molecular dynamics simulations at the water/DMPC interface and inside the lipid bilayer. As expected from the estimated percolation barriers, simulation results show that DME, contrary to DMP, spontaneously diffuse into the aqueous solution from the lipid interior. In addition, simulations with multiple DME or DMP molecules at the interface show spontaneous diffusion within 50 ns inside the DMPC layer only for DMP. © 2012 American Chemical Society.

Two equivalents of the unsymmetrical Schiff base ligand (L(tBu))(-) (4-tert-butyl phenyl(pyrrolato-2-ylmethylene)amine) and MoCl(2)(NtBu)O(dme) (dme = 1,2-dimethoxyethane) gave a single stereoisomer of a mixed imido/oxido Mo(VI) complex 2(tBu). The stereochemistry of 2(tBu) was elucidated using X-ray diffraction, NMR spectroscopy, and DFT calculations. The complex is active in an oxygen atom transfer (OAT) reaction to trimethyl phosphane. The putative intermediate five-coordinate Mo(IV) imido complex coordinates a PMe(3) ligand, giving the six-coordinate imido phosphane Mo(IV) complex 5(tBu). The stereochemistry of 5(tBu) is different from that of 2(tBu) as shown by NMR spectroscopy, DFT calculations, and X-ray diffraction. Single-electron oxidation of 5(tBu) with ferrocenium hexafluorophosphate gave the stable cationic imido phosphane Mo(V) complex [5(tBu)](+) as the PF(6)(-) salt. EPR spectra of [5(tBu)](PF(6)) confirmed the presence of PMe(3) in the coordination sphere. Single-crystal X-ray diffraction analysis of [5(tBu)](PF(6)) revealed that electron transfer occurred under retention of the stereochemical configuration. The rate of OAT, the outcome of the electron transfer reaction, and the stabilities of the imido complexes presented here differ dramatically from those of analogous oxido complexes.

We propose a new transferable force field to simulate phase equilibrium and interfacial properties of systems involving ethers and glycol ethers. On the basis of the anisotropic united-atom force field, only one new group is introduced: the ether oxygen atom. The optimized Lennard-Jones (LJ) parameters of this atom are identical whatever the molecule simulated (linear ether, branched ether, cyclic ether, aromatic ether, diether, or glycol ether). Accurate predictions are achieved for pure compound saturated properties, critical properties, and surface tensions of the liquid-vapor interface, as well as for pressure-composition binary mixture diagrams. Multifunctional molecules (1,2-dimethoxyethane, 2-methoxyethanol, diethylene glycol) have also been studied using a recently proposed methodology for the calculation of the intramolecular electrostatic energy avoiding the use of additional empirical parameters. This new force field appears transferable for a wide variety of molecules and properties. It is furthermore worth noticing that binary mixtures have been simulated without introducing empirical binary parameters, highlighting also the transferability to mixtures. Hence, this new force field gives future opportunities to simulate complex systems of industrial interest involving molecules with ether functions.

A range of methyl and ethyl ethers of aliphatic alcohols have been synthesized cleanly in high yield by reacting the corresponding alcohol with dimethyl carbonate or diethyl carbonate over the solid acid catalyst, γ-alumina. The reaction could be conducted at ambient pressure without the need for the large excess of dialkyl carbonate as previously reported in the literature. If the reaction was conducted at high pressure, the conversion of the starting alcohol was greatly reduced. However, high pressure CO2 can be used as the solvent without significant reduction in yield. This has implications for tandem reactions.

A highly regioselective Lewis acid-mediated S(N)2-type ring-opening of N-sulfonylaziridines and azetidines with tetraalkylammonium halides in CH(2)Cl(2) solution to afford 1,2- and 1,3-haloamines in excellent yields is described. An easy diastereoselective route toward substituted chiral N-tosylaziridines has been developed. The mechanism of ring-opening via S(N)2 pathway has been confirmed by the formation of chiral haloamines with excellent er and dr. Chloroamines obtained from 2,3-disubstituted aziridines were converted to the chiral N-tosylamines via radical dehalogenation.

A wide variety of 3-iodobenzo[b]furans were readily prepared by iodocyclization of 2-alkynyl-1-(1-ethoxyethoxy)benzenes with the I(coll)2PF6-BF3 x OEt2 combination. Aryl-, vinylic-, and alkyl-substituted alkynes undergo iodocyclization in good to excellent yields. The mechanism of the reaction is also discussed.

The photochemical reaction of (eta5-C5H5)Mo(CO)3I with maleimide in the presence of diisopropylamine yielded complex (eta5-C5H5)Mo(CO)3(eta1-N-maleimidato) 4 in 52% yield. The single-crystal X-ray structure of this complex was determined and shows unusual interactions between oxygen atoms of the maleimidato ligand and carbon atoms of the cis-CO ligands. The tungsten analogue of 4, (eta5-C5H5)W(CO)3(eta1-N-maleimidato) 5, was synthesized in 37% yield by the reaction of (eta5-C5H5)W(CO)3I with the thallium(I) salt of maleimide. Complexes 4 and 5 reacted with cysteine ethyl ester and glutathione to afford products of the addition of the sulfhydryl group to the ethylenic bond of the maleimidato ligand. The reaction of 4 and 5 with glutathione proceeded faster than the reaction of the analogous complex (eta5-C5H5)Fe(CO)2(eta1-N-maleimidato) (3). However, all these complexes react with glutathione more slowly than N-ethylmaleimide. Complexes 4 and 5 were used for labeling of bovine serum albumin (BSA), enriched in thiol groups by reaction with Traut's reagent. Reaction of thiolated BSA containing 7.4 SH groups with 4 and 5 gave bioconjugates bearing 6.9 and 6.4 metallocarbonyl moieties, respectively. Under the same conditions, reaction with 3 afforded a BSA conjugate containing 7.6 metallocarbonyl moieties. Labeling was presumed to be site-specific, as the number of metallocarbonyl entities matched very well with the initial number of SH groups measured for the thiolated BSA sample. IR spectra of BSA labeled with 4 and 5 show intense nu(C[triple bond]O)) bands (2042 and 1948 cm(-1) in the latter case), enabling sensitive detection of the bioconjugates in biological samples. Complexes 4 and 5 (especially the latter) should be of interest as heavy atom phasing reagents for protein X-ray crystallography.

Shell cross-linked (SCL) micelles with hydroxy-functional coronas have been constructed in aqueous solution by exploiting the micellar self-assembly behavior of a new thermoresponsive ABC triblock copolymer. This copolymer was prepared via atom transfer radical polymerization in a convenient one-pot synthesis and comprised a thermoresponsive core-forming poly(propylene oxide) (PPO) block, a cross-linkable central poly(2-(dimethylamino)ethyl methacrylate) (DMA) block, and a hydroxy-functional outer block based on poly(glycerol monomethacrylate) (GMA). DMF GPC analysis confirmed a unimodal molecular weight distribution for the PPO-PDMA-PGMA triblock copolymer precursor, with an M(n) of 12 100 and a polydispersity of approximately 1.26. This copolymer dissolved molecularly in aqueous solution at 5 degrees C but formed micelles with hydroxy-functional coronas above a critical micelle temperature of around 12 degrees C, which corresponded closely to the cloud point of the PPO macroinitiator. Cross-linking of the DMA residues using 1,2-bis(2-iodoethoxy)ethane produced SCL micelles that remained intact at 5 degrees C, i.e., below the cloud point of the core-forming PPO block. Dynamic light scattering studies confirmed that the SCL micelle diameter could be varied depending on the temperature employed for cross-linking: smaller, more compact SCL micelles were formed at higher temperatures, as expected. Since cross-linking involved quaternization of the DMA residues, the SCL micelles acquired cationic surface charge as judged by aqueous electrophoresis studies. These cationic SCL micelles were adsorbed onto near-monodisperse anionic silica sols, which were used as a model colloidal substrate. Thermogravimetric analyses indicated a SCL micelle mass loading of 2.5-4.4%, depending on the silica sol diameter and the initial micelle concentration. Aqueous electrophoresis measurements confirmed that surface charge reversal occurred after adsorption of the SCL micelles, and scanning electron microscopy studies revealed a uniform coating of SCL micelles on the silica particles.

In beer, the development of a solvent-like stale flavor is associated with the formation of furfuryl ethyl ether. The synthesis rate of this important flavor compound is proportional to the concentration of furfuryl alcohol in beer. This study shows that furfuryl alcohol in beer is mainly formed by Maillard reactions initiated during wort boiling and malt production. A mechanism for its formation from alpha-(1,4)-oligoglucans and amino acids in wort and beer is proposed. During wort boiling, a quadratic relationship was found between the wort extract concentration, on the one hand, and the increase of furfuryl alcohol and furfural, on the other. The reduction of furfural by yeast during fermentation further increases the furfuryl alcohol content. In pale beers, the furfuryl alcohol concentration is essentially determined by the thermal load on wort during brewing operations. In dark beers, a considerable fraction of furfuryl alcohol may, however, come from the dark malts used. These results lead to important practical conclusions concerning the control over furfuryl ethyl ether in beer.

Time-resolved FTIR spectroscopic studies of the flash photolysis of several 1-(2-nitrophenyl)ethyl ethers derived from aliphatic alcohols showed that a long-lived hemiacetal intermediate was formed during the reaction. Breakdown of this intermediate was rate-limiting for product release. One of these compounds (methyl 2-[1-(2-nitrophenyl)ethoxy]ethyl phosphate, 9) was studied in detail by a combination of time-resolved FTIR and UV-vis spectroscopy. In addition, product studies confirmed clean photolytic decomposition to the expected alcohol, 2-hydroxyethyl methyl phosphate, and the 2-nitrosoacetophenone byproduct. At pH 7.0, 1 degrees C, the rate constant for product release was 0.11 s(-1), very much slower than the 5020 s(-1) rate constant for decay of the photochemically generated aci-nitro intermediate (pH 7.0, 2 degrees C). Time-resolved UV-vis measurements showed that the hemiacetal intermediate is formed by two competing pathways, with fast (approximately 80% of the reaction flux) and slow (approximately 20% of the flux) components. Only the minor, slower path is responsible for the observed aci-nitro decay process. These competing reactions are interpreted with the aid of semiempirical PM3 calculations of reaction barriers. Furthermore, AMSOL calculations indicate that the pK(a) of the nitronic acid isomer formed by photolysis is likely to determine partition into the alternate paths. These unusual results appear to be general for 1-(2-nitrophenyl)ethyl ethers and contrast with a related 2-nitrobenzyl ether that photolyzed without involvement of a long-lived hemiacetal.

A series of ethers of orvinol and isoorvinol has been prepared and evaluated in opioid receptor binding and in vitro functional assays. The most striking finding was the very large difference in kappa-opioid receptor activity between the diastereomeric ethyl ethers: 46-fold in binding, 150-fold in GPI, and 900-fold in the [(35)S]GTPgammaS assay in favor of the (R)-diastereomer. Additionally in the (R)-series there was a 700-fold increase in kappa-agonist potency in the [(35)S]GTPgammaS assay when OEt was replaced by OBn. The data can be explained in a triple binding site model: an H-bonding site, a lipophilic site, and an inhibitory site with which the 20-Me group in the (S)-ethers may interact. It appears that kappa-agonist binding of the orvinols avoids the inhibitory site in the intramolecular H-bonded conformation.

An unprecedented natural acetophenone, polygonophenone (1), and a new resorcinol, polygonocinol (2), were isolated from the dichloromethane and methanol extracts of Polygonum maritimum and identified as 2-hydroxy-4-[(2-methoxyethoxy)methoxy] acetophenone and 2-methyl-5-nonadecylresorcinol, respectively. In addition, 11 known compounds were identified, namely, the sesquiterpenoid (+)-8-hydroxycalamene, four ferulic acid esters (tetracosyl, hexacosyl, octacosyl, and triacontyl ferulate), the arylpropane broussonin B, the flavonoids quercetin, quercitrin, and (+)-catechin, the hydroquinone glucoside isotachioside, and beta-sitosterol. The structures of the new compounds were elucidated on the basis of their NMR and MS data. It is noteworthy that polygonophenone (1) is the first naturally methoxyethoxymethyl (MEM)-substituted natural product, and its isolation gives support for the use of MEM protection in biomimetic synthetic schemes.

Methyl or ethyl ethers of 1-naphthyl carbinols ArCR2OR‘ (Ar = 1-naphthyl, R‘ = Me, Et) can occur in a range of rotational conformations whose population varies with the nature of the substituents R...

The biotransformation of the fuel oxygenates methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) was studied in rats after inhalation exposure; the biotransformation of the initial metabolite of these ethers, tert-butyl alcohol, was studied after oral gavage. To study ether metabolism, rats were exposed for 6 h to initial concentrations of 2000 ppm of MTBE or ETBE, respectively [2-13C]MTBE and [2-13C]ETBE. Urine was collected for 48 h after the end of the exposure, and urinary metabolites were identified by 13C NMR (13C-labeled ethers) and gas chromatography/mass spectrometry (GC/MS) (12C- and 13C-labeled ethers). To study tert-butyl alcohol metabolism, rats were dosed either with tert-butyl alcohol at natural carbon isotope ratio or with 13C-enriched tert-butyl alcohol (250 mg/kg of body weight), urine was collected, and metabolites were identified by NMR and GC/MS. tert-Butyl alcohol was identified as a minor product of the biotransformation of MTBE and ETBE. In addition, small amounts of a tert-butyl alcohol conjugate, likely a glucuronide, were present in the urine of the treated animals. Moreover, the mass spectra obtained indicate the presence of small amounts of [13C]acetone in the urine of [13C]MTBE and [13C]ETBE-treated rats. 2-Methyl-1,2-propanediol, 2-hydroxyisobutyrate, and another unidentified conjugate of tert-butyl alcohol, most probably a sulfate, were major urinary metabolites of MTBE and ETBE as judged by the intensities of the NMR signals. In [13C]-tert-butyl alcohol-dosed rats, [13C]acetone, tert-butyl alcohol, and its glucuronide represented minor metabolites; as with the ethers, 2-methyl-1,2-propanediol, 2-hydroxyisobutyrate, and the presumed tert-butyl alcohol sulfate were the major metabolites present. In one human individual given 5 mg/kg [13C]-tert-butyl alcohol orally, 2-methyl-1,2-propanediol and 2-hydroxyisobutyrate were major metabolites in urine detected by 13C NMR analysis. Unconjugated tert-butyl alcohol and tert-butyl alcohol glucuronide were present as minor metabolites, and traces of the presumed tert-butyl alcohol sulfate were also present. Our results suggest that tert-butyl alcohol formed from MTBE and ETBE is intensively metabolized by further oxidation reactions. Studies to elucidate mechanisms of toxicity for these ethers to the kidney need to consider potential toxicities induced by these metabolites.

Although a number of hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs) have been developed as possible substitutes for restricted chlorofluorocarbons (CFCs), it is not easy to satisfy both the industrial and environmental requirements. In the case of blowing agents, HFC 245fa and cyclopentane are presently expected to be promising alternatives to the traditional agent CFC 11 (trichlorofluoromethane). Gaseous thermal conductivities of six fluorinated methyl ethyl ethers, which are potential replacements for traditional blowing agents, have been measured by a transient hot-wire method. Temperature and pressure ranges of the measurements are from 303 K to 343 K and up to 0.4 MPa, respectively. The uncertainty of the thermal conductivities obtained is estimated to be within {+-}1%. Simple correlation equations were developed to represent the temperature and pressure dependences on the experimental thermal conductivities. Comparisons of the thermal conductivities between the present fluorinated ethers and those of traditional blowing agents CFC 11 (trichlorofluoromethane) and HCFC 141b (1,1-dichloro-1-fluoroethane) are given.

Furfural, 5-methylfurfural, and vanillin co-occurred in 64 barrel-aged red, white, and model wines with the reduction products, furfuryl alcohol, 5-methylfurfuryl alcohol, and vanillyl alcohol, and with the corresponding ethyl ethers of these alcohols. Hydrolytic studies in a model wine have shown that 5-methylfurfuryl ethyl ether is formed rapidly from 5-methylfurfuryl alcohol, but both decomposed quickly under the conditions. Vanillyl ethyl ether was also formed relatively rapidly, and both this ether and vanillyl alcohol were stable in the model wine. The formation of furfuryl ethyl ether from furfuryl alcohol and the subsequent decomposition of these two compounds were comparatively slow. The relative concentration of these aromatic alcohols and ethers in the barrel-aged wines was consistent with the observed stability of the furan derivatives, but low concentrations of vanillyl alcohol and vanillyl ethyl ether observed in all samples showed that factors other than solvolytic degradation were responsible for reducing the concentration of these compounds in wine. Furfuryl ethyl ether, which had an aroma threshold of 430 µg/L in a white wine, was found at approximate concentrations of up to 230 µg/L in the wines.

Enediynyl ethyl ethers 14/17 were synthesized by using the Pd(PPh3)4-catalyzed cross-coupling reactions between enynyl iodides 13/16 and (2-ethoxyethynyl)zinc chloride. Thermolysis of these enediynyl ethyl ethers in refluxing chlorobenzene (132 °C) promoted a retro-ene reaction to produce enyne−ketenes, which underwent the Moore cyclization reactions to form the biradicals having a phenyl radical center and a phenoxy radical center. The presence of two radical centers in the same molecule simultaneously provided many opportunities for intramolecular decay through disproportionation, radical−radical combination, and the formation of o-quinone methide.

Industrial production of mixed tertiary ethers by reacting methanol or ethanol with a mixed tertiary olefin stream is a distinct possibility. Consequently, the synthesis of mixed ethyl tertiary alkyl ethers from ethanol and mixtures of reactive iso-olefins in an isothermal integral packed-bed reactor is studied. The rate expressions in terms of activities for the individual reaction rates in this family of ethers are taken from related work. These kinetic expressions are utilized here for comparison with experimental data obtained in a packed-bed reactor containing Amberlyst 15 ion-exchange resin catalyst for a mixed iso-C6 olefin feed stream as well as for a mixed C4, C5, and C6 iso-olefin stream. Etherification and isomerization conversions increase with space time at the lower temperatures; however, at the higher temperatures equilibrium limitations are approached. As a function of temperature, the conversions first increase and then decline due to thermodynamic limitations for these exothermic reactio...

A new general route to conjugated enynyl ketones was developed based on a two-step procedure. First, palladium-catalyzed cross-coupling reactions of 1-(benzotriazol-1-yl)propargyl ethyl ether (3) and vinyl triflates or vinyl bromides afforded the key intermediates [1-(benzotriazol-1-yl)-1-enynyl]methyl ethyl ethers 5a-d in good yields. Then reactions of compounds 5 with primary halides gave intermediates 8, which were hydrolyzed by dilute acid to enynyl ketones 9a-g. Similar palladium-catalyzed coupling reactions of 3 with various aryl iodides followed by an analogous sequence afforded aryl-substituted propargyl ethers 12a-d and thence alkynyl ketones 13a,b.

[Reaction: see text] The (R)-oxynitrilase from almonds was immobilized as a cross-linked enzyme aggregate (CLEA) via precipitation with 1,2-dimethoxyethane and subsequent cross-linking using glutaraldehyde. The resulting preparation was a highly effective hydrocyanation catalyst under microaqueous conditions, which suppress the nonenzymatic background reaction. The beneficial effect of these latter conditions on the hydrocyanation of slow-reacting aldehydes is demonstrated. The oxynitrilase CLEA was recycled 10 times without loss of activity.

Tertiary ethers produced from reactive C{sub 5} and C{sub 6} olefins and ethanol or methanol are being investigated as oxygenate gasoline additives in addition to isobutylene-derived methyl tert-butyl ether and ethyl tert-butyl ether. The kinetics of liquid-phase etherification and accompanying isomerization of four reactive C{sub 6} olefin isomers with ethanol catalyzed by the ion-exchange resin catalyst Amberlyst 15 were determined at temperatures from 313 to 353 K and a pressure of 0.69 MPa in a differential packed-bed reactor. Rate expressions in terms of species activities, with the activity coefficients determined by the UNIFAC method, were developed to correlate the experimental data over a wide range of compositions. The rate expressions are based on the Langmuir-Hinshelwood-Hougen-Watson formalism involving a dual-site surface etherification reaction and a single-site surface isomerization reaction as the rate-limiting steps, along with the assumption of ethanol as the most abundant surface species. The negligibility of olefins and ether adsorption terms, but the nonnegligibility of vacant sites, was confirmed by independent liquid-phase adsorption experiments. The developed rate expressions were finally tested in an integral reactor and found to be accurate.

Alternatives to the conventional isobutylene-derived ethers, namely methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE), are being explored, e.g., those produced from a combination of the branched C{sub 5} and C{sub 6} olefins with methanol or biomass-based ethanol. The conversion and selectivity of these ethers are thermodynamically limited. This paper, thus, describes the determination and analysis of the equilibrium limitations in the liquid-phase synthesis of two of the three possible isomers of tert-hexyl ethyl ether (THEE) from reactive C{sub 6} olefins and ethanol in the temperature range 298--353 K. The coupled reaction network for either of these two ethers involves two simultaneous esterification and one isomerization reactions, all being reversible. The equilibrium constants for these reactions, experimentally determined from equilibrium composition and the corresponding activity coefficients estimated by the UNIFAC method, decrease in the following order of tertiary olefins: 2M1P > isobutylene 2M2P > 2M2B > 2,3DM2B for etherification reactions with ethanol, and (2,3DM1B {r_reversible} 2,3DM2B) > (2M1B {r_reversible} 2M2B) > (2M1P {r_reversible} 2M2P) for the isomerization reactions. This is explained on the basis of the relative stability of these olefins. The developed correlations are used to study the influence of process variables onmore » the equilibrium conversion and selectivity of THEE formation.« less

An efficient Au(I)-catalyzed synthesis of highly strained and functionalized bicyclo[3.2.0]heptanes is developed. Subsequent couplings with various nucleophiles offer additional structural features/complexity. These one-pot, three-component reactions are proposed to proceed via a key 1,3-dipolar cycloaddition between a Au carbenoid-containing carbonyl ylide and ethyl vinyl ether.

Bacterial luciferase is a heteropolymeric protein (alphabeta) that catalyses the conversion of chemical energy to light by oxidation of a reduced flavin mononucleotide and a long chain aliphatic aldehyde. Elucidation of the specific amino acid residues involved in the enzymatic reaction is essential for understanding the mechanisms of the bioluminescent reaction. Luciferase has been found to be inactivated by ethoxyformic anhydride with a second-order rate constant of 146 M-1 min-1 at pH 6.1 and 0 degrees C with a concomitant increase in absorbance at 240 nm due to formation of ethoxyformylhistidyl derivatives. Activity could be restored by hydroxylamine and the pH curve of inactivation indicated the involvement of a residue having a pKa of 6.8. Both substrates, FMNH2 and aldehyde, protected the enzyme against inactivation, suggesting that the modification occurred at or near the active site. Incorporation of [14C]ethoxyformyl groups in luciferase indicated that inactivation resulted from the modification of about three histidyl residues, one histidine being found on the alpha subunit and two on the beta subunit. Hybridization experiments, in which ethoxyformylluciferase, alphambetam, was complemented with native subunits, alpha or beta, showed that the hybrid alphambetam, has the same activity as alphambetam whereas the activity of the hybrid alphabetam, was close to that of the reconstituted luciferase alphabeta. The results indicate that modification of only one histidyl residue on the alpha subunit inactivates luciferase and suggest that this histidyl residue plays an essential role in the mechanism of the bacterial bioluminescent reaction.

The 3-[(2-ethoxyphenoxy)methyl]piperidine derivatives 3-5 were synthesized and screened as potential antidepressant agents by the reserpine interaction test in mice and the evaluation of reuptake inhibition of biogenic amines in pig brain synaptosomal fractions. In addition, their anticonvulsant activity, tested by pentyleneetrazole antagonism, and approximate acute toxicity were evaluated. In vivo and in vitro tests showed that compounds 3 and 5 possess a biological activity comparable to that of the antidepressant drug viloxazine.

The vinyl ethers of choline and of its alpha- and beta-methyl homologues were prepared to determine their cholinergic effects and to determine whether a separation of the dual physiologic activity (nicotinic and muscarinic) reported for the vinyl ether of choline could be achieved by this modification. A literature method of vinyl transetherification of amino alcohols has been studied and modified. The ethyl ethers of choline and of alpha- and beta-methylcholine were prepared for comparison with the vinyl ethers. Two independent, unequivocal syntheses of the ethyl ether of beta-methylcholine have been accomplished. This study showed that the two literature methods for synthesis of this compound are equivocal, and, hence, the biological data reported for this compound in the older literature may not be valid. Certain of the ethers showed marked nicotinic or muscarinic activities.