Search

High exo-facial selectivity was observed in the selective monohydrolysis of a series of near-symmetric diesters that possess an exo-ester group and an endo-ester group attached on a norbornane or norbornene skeleton. The selectivities were found to be clear-cut, although the reaction center in these reactions is one covalent bond distant from the norbornane or norbornene ring, where the difference of the environment between the exo face and endo face is therefore expected to be negligible. The effect of the co-solvent we studied earlier for the selective monohydrolysis reaction was also confirmed and contributed to improvement of the yields of the half-esters.

Straightforward access toward previously unreported substituted, heterocyclic spiro[3.3]heptanes is disclosed. These spirocyclic systems may be considered as alternatives to 1,3-heteroatom-substituted cyclohexanes, which are otherwise insufficiently stable to allow their use in drug discovery. Conformational details are discussed on the basis of X-ray crystallographic structures.

Four medical grade silicones were swollen, until they reached equilibrium (i.e. constant mass) in eight liquids at 25 degrees C. The greatest swelling was obtained with n-heptane but the volume fraction, varphi, of the silicones in their swollen state was not significantly different (p<0.05) in this liquid than in cyclohexane. For each grade of silicone, varphi was plotted against delta(l), the liquid solubility parameter, for each liquid in which it was swollen. A second-order polynomial was plotted through the results; the minimum in this polynomial provided a value for the polymer solubility parameter, delta(p). The Flory polymer-liquid interaction parameter, chi, was calculated for the four best liquids, using Hildebrand's solubility parameter theory. An alternative method for calculating chi, directly from swelling measurements, was shown to produce physically unreasonable results. The cross-link density, upsilon, was calculated, from varphi and chi, for each grade of silicone, using the Flory-Rehner equation. Since the values of two parameters involved in Hildebrand's theory cannot be determined reliably and because the Flory-Rehner equation is an approximation, absolute values of upsilon cannot be obtained. However, the relative values of upsilon obtained were higher for the harder grades then for the softer grades and similarly, the grades with the higher Young's modulus had higher upsilon values.

Direct esterification of alpha-terpineol and acetic anhydride catalyzed by Candida rugosa lipase was performed in supercritical carbon dioxide (SC-CO(2)) with organic solvent serving as co-solvents. The highest yield of terpinyl acetate after 1.5h of reaction performance (95.1%) was obtained in SC-CO(2) with n-heptane serving as a co-solvent and immobilized Candida rugosa lipase as an enzyme at 50 degrees C. The optimal pressure for terpinyl acetate synthesis in SC-CO(2) medium was 10 MPa. Acetic anhydride was the best substrate among all acyl donors. Anhydrous enzyme was found to be the best for the esterification reaction. Lipase immobilization increased the catalytic efficiency up to 1.8-fold. The analysis of the initial rate data showed that reaction followed a Ping-Pong Bi-Bi mechanism with inhibition by acetic anhydride. The kinetic constants were obtained by multiple regression analysis of experimental findings. The reaction went smoothly without the use of hazardous reactants, and the developed method is useful for industrial application., ((c) 2010. Published by Elsevier B.V. All rights reserved.)

Intramolecular nitrone cycloaddition (INC) reaction on a d-glucose derived substrate carrying an allyl group at C-1 and an enose-nitrone at C-5 or an aldehyde-nitrone at C-1 and vinyl group at C-4 furnished a tricyclo[6.2.1.0(2,6)]undecane or a tricyclo[5.2.1.0(2,6)]decane ring structure. These tricycles were converted to bicylic nucleosides with oxabicyclo[3.2.1]octane and oxabicyclo[2.2.1]heptane rings in three steps. An oxabicyclo[3.2.1]octane ring compound could alternatively be formed by RCM reaction between C-1-allyl and C-4-vinyl moieties and transformed to nucleoside analogues through a nucleophilic substitution reaction. Participation of a neighboring benzyl ether substituent in one case paved the way for an enantiodivergent synthesis.

Conventional analytical methods such as (1)H NMR, vapor pressure osmometry (VPO) and elemental analysis were used to characterize the tar obtained from pyrolysis of pine. The major fraction of tar obtained during pyrolysis of pine at different temperatures was the insoluble fraction in n-heptane which corresponds to asphaltenes; this fraction was characterized and analyzed using average structural parameters. The structural unit of the tar is composed of one aromatic ring substituted by aliphatic chains, olefinic groups and the presence of oxygenated groups. Two of such average structures determined with this methodology corresponds to 4-formyl-2,6-dimethoxy-3-[(1E)-prop-1-en-1-yl]-5-propylbenzoic acid and 2,3,5-trimethoxy-6-[(1E)-prop-1-en-1-yl]-4-propylbenzaldehyde., (Copyright 2009 Elsevier Ltd. All rights reserved.)

Partition coefficients for 84 varied compounds were determined for n-heptane-formamide biphasic partition system and used to derive a model for the distribution of neutral compounds between the n-heptane-rich and formamide-rich layers. The partition coefficients, log K(p), were correlated through the solvation parameter model giving log K(p)=0.083+0.559E-2.244S-3.250A-1.614B+2.387V with a multiple correlation coefficient of 0.996, standard error of the estimate 0.139, and Fisher statistic 1791. In the model, the solute descriptors are excess molar refraction, E, dipolarity/polarizability, S, overall hydrogen-bond acidity, A, overall hydrogen-bond basicity, B, and McGowan's characteristic volume, V. The model is expected to be able to estimate further values of the partition coefficient to about 0.13 log units for the same descriptor space covered by the calibration compounds (E=-0.26-2.29, S=0-1.93, A=0-1.25, B=0.02-1.58, and V=0.78-2.50). The n-heptane-formamide partition system is shown to have different selectivity to other totally organic biphasic systems and to be suitable for estimating descriptor values for compounds of low water solubility and/or stability.

In the present work, the adsorption ability of sugarcane bagasse to remove oil by-products from aqueous solution was evaluated. The objective was treating the contaminated wastewater while enriching the bagasse for its later use as fuel in boilers. Adsorption experiments were carried out in an agitated reactor at room temperature to obtain kinetic curves and adsorption isotherms of gasoline and n-heptane on sugarcane bagasse. The results showed the great potential of bagasse as an adsorbent, since it was able to adsorb up to 99% of gasoline and 90% of n-heptane in solutions containing about 5% of these contaminants. In the adsorption kinetics of gasoline, the equilibrium was reached after just 5 min. This result shows that the adsorption is very favorable. Langmuir, Freundlich, Temkin and D-R models did not describe well the adsorption behavior obtained for these systems., ((c) 2009 Elsevier B.V. All rights reserved.)

Ultrafast two dimensional infrared (2D-IR) spectroscopic methods have been used to study the vibrational dynamics of a transient 17e(-) metallocarbonyl species formed following photolysis of the n-propyl-cyclopentadienyl tungsten tricarbonyl dimer [(nPr-Cp)W(CO)(3)](2) in solution. A combination of ground-state 2D-IR and transient 2D-IR techniques has revealed interesting differences in the vibrational relaxation processes of the parent dimer and the monomeric photoproduct that are ascribed to changes in solvent interactions arising from the unsaturated coordination sphere of the intermediate. Additionally, the infrared spectrum of the lesser-populated gauche isomeric form of the dimer in the carbonyl-stretching region has been determined using the presence of off-diagonal peaks in the 2D-IR spectra.

The de novo synthesis of racemic 1',4'-dimethyluridine was accomplished in 12 steps starting from 2,5-dimethylfuran and vinylene carbonate. Key steps of the sequence include the stereoconvergent preparation of a meso diacid, and a stereoselective glycosylation without neighboring group participation. Such 1',4'-disubstituted ribonucleoside analogues are undisclosed compounds, which may present interesting biological activities.

Water-in-oil (W/O) microemulsion is a well-suitable confined reacting medium for the synthesis of structured functional nanoparticles of controlled size and shape. During the last decade, it allowed the synthesis of multi-functional silica nanoparticles with morphologies as various as core-shell, homogenous dispersion or both together. The morphology and properties of the different intermediates and final materials obtained through this route are discussed in the light of UV-Vis-NIR spectroscopy, dynamic light scattering (DLS) and X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and magnetometer SQUID analysis.

Cross-linked polydimethylsiloxane (PDMS)-polyetherimide (PEI) composite membranes were prepared, in which asymmetric microporous PEI membrane prepared with phase inversion method was acted as the microporous supporting layer in the flat-plate composite membrane. Membrane characterization was conducted by Fourier transform infrared and scanning electronic microscopy analysis. The composite membranes were employed in pervaporation separation of n-heptane-thiophene mixtures. Effect of amount of PDMS, cross-linking temperature, amount of cross-linking agent, and cross-linking time on the separation efficiency of n-heptane-thiophene mixtures was investigated experimentally. Experiment results demonstrated that 80-100 degrees degrees C of cross-linking temperature was more preferable for practical application, as the amount of cross-linking agent was up to 20 wt.%, and 25 wt.% of PDMS amount was more optimal as far as flux and sulfur enrichment factor were concerned. In addition, the swelling degree of and stableness of composite membrane during long-time operation were studied, which should be significant for practical application.

Objectives: The objective of this work was to evaluate thiol-norbornene and thiol-ene-methacrylate systems as the resin phase of dental restorative materials and demonstrate their superior performance as compared to dimethacrylate materials., Methods: Polymerization kinetics and overall functional group conversions were determined by Fourier transform infrared spectroscopy (FTIR). Flexural strength and modulus were determined with a 3-point flexural test. Polymerization-induced shrinkage stress was measured with a tensometer., Results: Thiol-ene polymer systems were demonstrated to exhibit advantageous properties for dental restorative materials in regards to rapid curing kinetics, high conversion, and low shrinkage and stress. However, both the thiol-norbornene and thiol-allyl ether systems studied here exhibit significant reductions in flexural strength and modulus relative to BisGMA/TEGDMA. By utilizing the thiol-ene component as the reactive diluent in dimethacrylate systems, high flexural modulus and strength are achieved while dramatically reducing the polymerization shrinkage stress. The methacrylate-thiol-allyl ether and methacrylate-thiol-norbornene systems both exhibited equivalent flexural modulus (2.1+/-0.1 GPa) and slightly reduced flexural strength (95+/-1 and 101+/-3 MPa, respectively) relative to BisGMA/TEGDMA (flexural modulus; 2.2+0.1 GPa and flexural strength; 112+/-3 MPa). Both the methacrylate-thiol-allyl ether and methacrylate-thiol-norbornene systems exhibited dramatic reductions in shrinkage stress (1.1+/-0.1 and 1.1+/-0.2 MPa, respectively) relative to BisGMA/TEGDMA (2.6+/-0.2 MPa)., Significance: The improved polymerization kinetics and overall functional group conversion, coupled with reductions in shrinkage stress while maintaining equivalent flexural modulus, result in a superior overall dental restorative material as compared to traditional bulk dimethacrylate resins.

Physicochemical properties (partition and diffusion coefficients) involved in the mobility and release of salt and aroma compounds in model cheeses were determined in this study. The values of NaCl water/product partition coefficients highlighted interactions between proteins and NaCl. However, these interactions were not modified by the product composition or structure. On the contrary, model cheese composition and structure influenced NaCl diffusion and both partition and diffusion for aroma compounds. Analysis of in-nose measurements of aroma release during eating, with regard to physicochemical properties, showed that product and aroma properties partly contributed to flavor release. Depending on the model cheese composition, structure and firmness, physicochemical properties, food breakdown, and chewing behavior can lead to different aroma release profiles. Finally, a discussion of all the results with regard to salt and flavor perception of the model cheese showed that both physicochemical and cognitive mechanisms contributed to perception.

This critical review showcases examples of rapid formation of complexity in total syntheses starting from 7-oxabicyclo[2.2.1]hept-5-ene derivatives. An overview of methods allowing synthetic access to these building blocks is provided and their application in recently developed synthetic transformations to structurally complex systems is illustrated. In addition, the facile access to a novel oxabicyclo[2.2.1]heptene derived building block is presented which significantly enlarges the possibilities of previously known chemical transformations and is highlighted in the enantioselective route to the core of the banyaside and suomilide natural products (107 references).

We have reported the study of methanol/AOT/n-heptane reverse micellar aggregates using Fourier Transform Infrared (FTIR) spectroscopy. We have divided our whole work into two parts. In the first part we have studied the structural properties of Aerosol OT (AOT) reverse micelles by monitoring the changes in the symmetrical sulfonate stretching region (1000-1100 cm(-1)), asymmetrical sulfonate stretching region (1130-1330 cm(-1)) and carbonyl frequency region (1695-1770 cm(-1)), and in the other part we have measured the changes in the maximum position of OH stretching frequency region (3140-3650 cm(-1)) with increasing methanol content of the reverse micellar solution. Finally we have defined and established the presence of different types of methanol inside the reverse micelle by splitting the OH frequency region using multiple Gaussian curve fitting. Though methanol is partially soluble in n-heptane, this work certainly proves the existence of stable methanol/AOT/n-heptane reverse micelles.

The present study investigated the effects of oxygen-containing terpenes as skin permeation enhancers on the lipoidal pathways of human epidermal membrane (HEM). The enhancement (E(HEM)) effects of menthol, thymol, carvacrol, menthone, and cineole on the transport of a probe permeant, corticosterone, across HEM were determined. It was found that the enhancer potencies of menthol, thymol, carvacrol, and menthone were essentially the same and higher than that of cineole based on their aqueous concentration in the diffusion cell chamber at E(HEM) = 4. Thymol and carvacrol also had the same E(HEM) = 10 concentration further supporting that they had the same enhancer potency based on the aqueous concentration. The uptake amounts of terpene into the HEM stratum corneum (SC) intercellular lipid under the same conditions indicate that the intrinsic potencies of the studied terpenes are the same based on their concentration in the SC and similar to those of n-alkanol and n-alkylphenyl alcohol. Moreover, they are all better enhancers compared to branched-chain alkanol. The approximately same uptake enhancement of beta-estradiol induced by the studied terpenes and alcohols at E(HEM) conditions into the SC intercellular lipids suggests that the mechanism of enhancement action for the terpenes and those of alcohols are essentially the same.

A stereocontrolled synthesis of alkanes containing five contiguous fluorine atoms is presented. The compounds were prepared by sequential fluorination of diastereoisomeric alcohol-diepoxides. The chemistry involved epoxide ring-opening with HF.NEt(3) and deshydroxyfluorination reactions of free alcohols with Deoxo-Fluor. The fluorination reactions were all highly stereospecific, with all five fluorines being incorporated in three sequential steps. Three different diastereoisomers of the 2,3,4,5,6-pentafluoroheptyl motif were prepared as heptane-1,7-diol derivatives, a structural format amenable for incorporation of the vicinal pentafluoro scaffold into larger molecular architectures.

Addition of allyltributylstannane to 2,7-dioxabicyclo[2.2.1]heptane in the presence of TiCl(4) produces 5-allyl-2-(hydroxymethyl)tetrahydrofuran with a trans/cis ratio of 93:7. The trans-selectivity is also observed in additions of various other carbon nucleophiles.

The coexistence of different excited states with different properties of the same chromophores could have significant consequences for the accurate characterization of solvation dynamics in a heterogeneous environment, such as a protein. The purpose of this work is to study the contributions of the locally excited (LE) and charge-transferred (CT) states of the fluorescent probe molecule 6-propionyl-2-(N,N-dimethylamino)naphthalene (PRODAN) to its solvation dynamics in the heterogeneous environment provided by reverse micelles formed by sodium 1,4-bis-(2-ethylhexyl) sulfosuccinate (AOT)/n-heptane/water. We have found that the LE and CT states of PRODAN solvate on different time scales in reverse micelles (2 and approximately 0.4 ns, respectively), consistent with results suggested in the literature, and have concluded that PRODAN's use as a probe of heterogeneous environments must be used with caution and that, more importantly, the same caution must be exercised with any chromophore capable of emitting from different excited states.

Mesoporous silica (SBA-15) synthesized by using Pluronic123 as the structure-directing template was functionalized by imidazolium-based ionic liquid precursors. Silver salts were then immobilized onto the supported ionic liquids using the incipient wetness impregnation technique. The separation of unsaturated species was achieved through the reversible and specific interaction between silver ions and carbon-carbon double bonds. This adsorbent was examined for the selective separation of polyunsaturated triacylglycerols (PUTAG) using High Pressure Liquid Chromatography (HPLC) with Evaporative Light Scattering Detection (ELSD) as the quantification methodology. AgBF(4)/SBA15.HPSiOEtIM.PF(6) showed an adsorption capacity for linolenin of about 217 mg adsorbed/gram of sorbent. This adsorbent had good selectivity and a high capacity for the most highly unsaturated triacylglycerol when applied to a mixture of triacylglycerols with varying degrees of unsaturation. Consequently, a stepwise methodology was also developed to increase the recovery of the adsorbed components. This adsorbent retained its selectivity and capacity when recycled up to five times., (2009 American Institute of Chemical Engineers Biotechnol.)

In the present molecular dynamics simulations we study the chemical warfare agent sulfur mustard (bis(2-chloroethyl) sulfide) and the alkane heptane inserted into a dipalmitoylphosphatidylcholine (DPPC) bilayer, a generic model for a biological membrane. We investigate the diffusion, the orientation, the preferred positioning, and the end-to-end distance of the solutes within the membrane as well as the corresponding coupling times. We compare results of equilibrium simulations and simulation at different external forces, which drag the solutes through the membrane. These properties lead to a general comparison of the rotational and translational behaviors of the two solutes during the penetration of the membrane. We show that sulfur mustard, due to its atomic charge polarization, its bigger flexibility and its smaller molecular volume, is the faster moving molecule within the membrane. In last consequence, we show that this leads to different limits for the transport mechanism as observed in these simulations. For heptane the hindrance to penetrate into the membrane is significantly higher than for sulfur mustard. In contrast to heptane molecules, which spend the most of the time penetrating the tail groups, sulfur mustard needs more time to escape the tail group-head group interface of the membrane.

This paper reports a theoretical study of decan-1-ol+heptane and ethanol+heptane systems and experimental data of decan-1-ol+heptane mixtures as a function of temperature and pressure over the whole composition range. The ability of the modifications introduced into the original ERAS model in determining thermodynamic excess properties of decan-1-ol+heptane and ethanol+heptane mixtures at high pressures is tested. This model was found to be sufficient for describing semiquantitatively excess volumes and excess enthalpies and qualitatively excess heat capacities under high pressure. The densities and speeds of sound in decan-1-ol+heptane mixtures were measured over the whole concentration range within the temperature interval from 293 to 318 K at atmospheric pressure and at pressures up to 101 MPa, respectively. The densities, heat capacities and appropriate excesses of these binaries were calculated for the same temperatures and pressures up to 100 MPa. In the calculations the acoustic method was applied. The effects of pressure and temperature on the excess volume, excess enthalpy, and the excess heat capacity of decan-1-ol+heptane mixtures are analyzed and compared with those of ethanol + heptane and dodecane+heptane mixtures. Properties of the alkan-1-ol+alkane mixtures are explained in terms of the self-association of the alkanols, free volume effect and the nonspecific interactions between the alcohol and heptane basing on the results obtained from the modified ERAS model.

A series of seven cyclopent-3-en-1-ylmethylamines bearing one, two, or three methyl substituents at the C2, C3, C4, or C(alpha) positions, including the unsubstituted parent, was accessed by ring-closing metatheses of alpha,alpha-diallylacetonitrile (or methallyl variants) and alpha,alpha-diallylacetone followed by hydride reductions or reductive amination, or by Curtius degradations of alpha,alpha-dimethyl- and 2,2,3-trimethylcyclopent-3-enylacetic acids. Oxidation of the primary amines with Pb(OAc)(4) in CH(2)Cl(2), CHCl(3) or benzene in the presence of K(2)CO(3) effected efficient intramolecular aziridinations, in all cases except the alpha-methyl analogue (16), to form the corresponding 1-azatricyclo[2.2.1.0(2,6)]heptanes, including the novel monoterpene analogues, 1-azatricyclene and the 2-azatricyclene enantiomers. The cumulative rate increases of aziridination reactions observed by (1)H NMR spectroscopy in CDCl(3) resulting from the presence of one or two methyl groups on the cyclopentene double bond, in comparison to the rate of the unsubstituted parent amine (1:17.5:>280), indicate a highly electrophilic intermediate as the nitrene donor and a symmetrical aziridine-like transition state. A mechanism is outlined in which the amine displaces an acetate ligand from Pb(OAc)(4) to form a lead(IV) amide intermediate RNHPb(OAc)(3) proposed as the actual aziridinating species.

SO(4)(2-)/M(x)O(y) is of the greatest interest in solid catalysts and green catalysts. Slurry bubble column reactors are of considerable interest in industrial processes and various biochemical processes. The cetane number (CN) has widely used diesel fuel quality parameter related to the ignition delay time (and combustion quality) of a fuel. CN improvement of diesel fuels is a difficult task that refiners will face in the near future. For that purpose, the tests were designed in which n-heptane is used as the reactant in the air or ozone atmosphere at room temperature (RT) and local atmospheric pressure (LAP) using different catalysts of sulfated tri-component metal oxides SO(4)(2-)/Fe(2)O(3)-TiO2-SnO(2) (SFTSn) and SO(4)(2-)/MnO(2)-TiO2-SnO(2) (SMTSn) in slurry bubble column reactor. The products distribution was analyzed by gas chromatography-mass spectrometry (GC-MS) method and the results show that the relative selectivity of long linear alkane (C(12)-C(28)) reaches the maximum (87.330%) when SMTSn is used as catalyst in flow air at 60 min. Diesel fuel components with higher cetane numbers can be easily obtained from this study.

In countercurrent chromatography (CCC) the choice of the liquid system is the heart of any separation. It corresponds to the selection of the mobile phase and the stationary phase at the same time. Any change in one phase composition induces a change in the other phase composition which renders the choice of the appropriate liquid system difficult and lengthy. A scale of compositions of the heptane-ethyl acetate-methanol-water quaternary liquid system was referred to by letters from A to Z and called the Arizona (AZ) liquid system. Each composition of the AZ system has the same heptane/ethyl acetate and methanol/water volume ratios. It is shown that there is a continuous polarity change from the hydrophilic A composition (ethyl acetate-water) to the hydrophobic Z (heptane-methanol) mixture by measuring the distribution constant K(D) of a known test mixture. For all compounds, the log K(D) is linearly increasing with the water content of the lower aqueous phase of the composition used. The slopes of the log K(D) versus percent H(2)O have very different values which means that the chromatographic selectivity changes with liquid system compositions. The AZ system was associated to the elution-extrusion method to design a procedure to identify rapidly the appropriate solvent composition able to fractionate correctly a complex natural extract. With the use of an integrated three-coil CCC column (40 mL each coil) able to test three AZ compositions in parallel, it is shown that the optimum AZ composition is found in half a day using less than a liter total volume of solvents. Two natural extracts are rapidly screened using the proposed protocol. An extract of Piper longum L. of intermediate polarity was fractionated in five usable portions using the 3/2/3/2 (Q) composition of the AZ system. A polar extract of Polygonum cuspidatum was also separated in five fractions using the 1/6/1/6 (D) composition. In both cases, a 140 mL CCC column was used for a direct scale-up transfer with the same liquid system. Purified fractions were subjected to an antioxidant activity assay and liquid chromatography with UV and mass spectrometry detection (LC-UV/MS) analysis to determine the molecular weight, number, and quantity of compounds in the active fractions. Four fractions of P. cuspidatum showed excellent antioxidant activity. They were rapidly produced at the milligram level by the 140 mL CCC column and fractionated by semipreparative high-performance liquid chromatography (HPLC) in individual compounds that were each identified by NMR and MS and reevaluated for confirmation of bioactivity. The rapid screening CCC protocol associated to the preparative capability of CCC allows for a fast identification and characterization of active compounds in natural products.

This paper reports the structure of the hydrate complex of an isolated alcoholic OH, produced in a small amount in hydrophobic solution in heptane. The structure was determined from the changes, caused by hydration, in the infrared and near-infrared spectra of 2-nonanol in the solution. The changes were exhibited in the "difference" spectrum, in which the spectrum of the solution before hydration was subtracted from that after hydration. The difference spectrum showed a "plus" or "minus" peak at the frequency of the stretching band of a free OH, depending on whether the concentration was below or above about 2%(v/v), respectively. The plus peak appears because the OH stretching band of the isolated OH that acts as an acceptor does not change in frequency but significantly increases in intensity, in agreement with theoretical calculations. In contrast, the stretching band of an isolated OH that acts as a donor shifts downward. This shift decreases the intensity at the stretching frequency of a free OH, giving rise to a minus peak at the frequency in the difference spectrum. It was concluded that an isolated OH is hydrated in the manner as HO...HOH and OH...OH(2) at a concentration below and above about 2%, respectively, in the hydrophobic solution of 2-nonanol.

The synthesis of a new series of oxazolidinones having spiro[2,4]heptane moieties is described. Their in vitro antibacterial activities against both Gram-positive and Gram-negative bacteria were tested and the effect of substituents on the oxazolidinone ring was investigated. A particular compound Ih having fluoro group showed the most potent antibacterial activity.

The purpose of this study was to investigate the effects of food-simulating liquids (FSL) on the hardness and flexural strength (FS) of a new silorane-based composite and to compare it with methacrylate-based composites (MBCs). Four restorative materials (Filtek Silorane, P60, Z250, and Supreme XT) were used. Specimens for the FS and hardness measurements were fabricated in customized molds. Immediately after polymerization, the materials were stored in the following dietary simulating solvents at 37 degrees C for 1 week: distilled water, 0.02 N citric acid, heptane, and 75% aqueous ethanol solution. After conditioning, the FS and hardness values were measured. Data were subjected to ANOVA/Scheffé's test at a significance level of 0.05. The hardness and FS of Filtek Silorane were not significantly affected by FSL (p>0.05). Conversely, the hardness of MBCs significantly decreased after conditioning in water and ethanol (p<0.05). Similarly, the FS values of MBCs were significantly affected after conditioning in ethanol.

Purpose: The aim of this study was to prepare and characterize novel hydrogel-based delivery systems allowing for the controlled release of drugs to mucosal surfaces., Methods: Terbutaline sulfate and bovine serum albumin (BSA)-loaded alginate-poloxamer microparticles were prepared by a w/o-emulsion- and external gelation method. The microparticles were characterized by optical and scanning electron microscopy, laser light diffraction, atomic absorption spectroscopy, energy-dispersive X-ray analysis, via complexation with 1,9-dimethyl methylene blue and using dialysis bags as well as modified Franz diffusion cells for in vitro drug-release measurements., Results: Using heptane as organic phase, homogeneous and almost spherical microparticles were obtained with a high-loading efficiency (>90%). The resulting drug-release patterns could effectively be adjusted by varying the "alginate:poloxamer" blend ratio. In addition, the particle size, morphology, calcium and chloride content as well as alginate-release rates could be altered. Erosion was the predominant release mechanism for BSA. Special attention needs to be paid to the microparticle recovery procedure, which can significantly affect key properties such as the resulting drug-release patterns., Conclusions: The novel hydrogel-based microparticles offering mild conditions for incorporated drugs (e.g., proteins) provide an interesting potential as controlled delivery systems for mucosal surfaces.

Abscisic acid (ABA) is a carotenoid-derived plant hormone known to regulate critical functions in growth, development and responses to environmental stress. The key enzyme which carries out the first committed step in ABA biosynthesis is the carotenoid cleavage 9-cis-epoxycarotenoid dioxygenase (NCED). We have developed a series of sulfur and nitrogen-containing compounds as potential ABA biosynthesis inhibitors of the NCED, based on modification of the sesquiterpenoid segment of the 9-cis-xanthophyll substrates and product. In in vitro assays, three sesquiterpene-like carotenoid cleavage dioxygenase (SLCCD) inhibitor compounds 13, 17 and 18 were found to act as inhibitors of Arabidopsis thaliana NCED 3 (AtNCED3) with K(i)'s of 93, 57 and 87 microM, respectively. Computational docking to a model of AtNCED3 supports a mechanism of inhibition through coordination of the heteroatom with the non-heme iron in the enzyme active site. In pilot studies, pretreatment of osmotically stressed Arabidopsis plants with compound 13 resulted lower levels of ABA and catabolite accumulation compared to levels in mannitol-stressed plant controls. This same inhibitor moderated known ABA-induced gene regulation effects and was only weakly active in inhibition of seed germination. Interestingly, all three inhibitors led to moderation of the stress-induced transcription of AtNCED3 itself, which could further contribute to lowering ABA biosynthesis in planta. Overall, these sesquiterpenoid-like inhibitors present new tools for controlling and investigating ABA biosynthesis and regulation.

Functionalized monolithic columns were prepared via ring-opening metathesis polymerization (ROMP) within silanized fused silica capillaries with an internal diameter of 200 microm by in situ grafting. This procedure is conducted in two steps, the first of which is the formation of the basic monolithic structure by polymerization of norborn-2-ene (NBE) and 1,4,4a,5,8,8a-hexahydro-1,4,5,8-exo,endo-dimethanonaphthalene (DMN-H6) in a porogenic system (toluene and 2-propanol) using RuCl(2)(PCy(3))(2)(CHPh) as ROMP initiator. In the second step the still active initiator sites located on the surface of the structure-forming microglobules were used as receptor groups for the attachment ("grafting") of functional groups onto the monolithic backbone by flushing the monolith with 7-oxanorborn-2-ene-5,6-carboxylic anhydride (ONDCA). Functionalization conditions were first defined that did not damage the backbone of low polymer content (20%) monoliths allowing high-throughput chromatographic separations. Variation of the functionalization conditions was then shown to provide a means of controlling the degree of functionalization and resulting ion-exchange capacity. The maximum level of in situ ONDCA grafting was obtained by a 3h polymerization in toluene at 40 degrees C. The weak cation-exchange monoliths obtained provided good separation of a standard peptide mixture comprising four synthetic peptides designed specifically for the evaluation of cation-exchange columns. An equivalent separation was also achieved using the lowest capacity column studied, indicative of a high degree of robustness of the functionalization procedure. As well as demonstrably bearing ionic functional groups enabling analyte separation in the cation-exchange mode, the columns exhibited additional hydrophobic characteristics which influenced the separation process. The functionalized monoliths thus represent useful tools for mixed-mode separations.

During soil bioremediation, the diffusion of oxygen into the soil is an important prerequisite for aerobic biodegradation, and the decrease of petroleum products is the ultimate goal. Both processes need to be monitored. The aim of this work was to develop a gas tracer test that yields information on both, gas diffusion and residual saturation with non-aqueous phase liquids (NAPLs) in unsaturated soil heaps. One conservative tracer (methane) and 4 partitioning gas tracers (diethylether, methyl tert-butyl ether, chloroform and n-heptane) were injected as vapors into laboratory columns filled with unsaturated sand with increasing NAPL saturation. Breakthrough curves of gaseous compounds were measured at two points and compared to analytical solutions of an analytical diffusive-reactive transport equation. By fitting of methane data, robust results for effective diffusivity (tortuosity) were obtained. NAPL saturation was most accurately measured by the moderately water soluble tracers (ethers and chloroform). The hydrophobic tracer n-heptane did not partition into water-immersed NAPL. An easy and accurate way to assess air-NAPL partitioning constants from gas chromatography retention times is furthermore reported. It is concluded that gas tracer tests have the potential for measuring two important properties in soil bioremediation systems easily and quickly.

It was of interest to investigate the possible interactions that might occur between chitosan and various compounds of different polarities using solvent vapor sorption and Fourier Transform Infrared Spectroscopy (FTIR). The sorption system was composed of a gas inlet, a 2 meter gas cell and a gas outlet. The experimental set up allowed quantification of the free vapor and therefore the amount of the sorbed vapor by chitosan powder. The BET equation was applied to the experimental data to obtain the apparent monolayer sorption capacity (Sm) and the parameter C, which is related to the heat of interaction. Results demonstrated that the surface areas obtained for chitosan from the BET analyses for heptane, 1,4-dioxane and methanol were 421, 379 and 58 m(2)/g, respectively. These values were extremely higher than the value obtained from nitrogen vapor adsorption isotherm (4.56 m(2)/g). The difference is attributed to the partitioning of these compounds into the chitosan particles. The large difference in the Sm values between the nonpolar (heptane and 1,4-dioxane) and the semipolar compounds (methanol) also suggested that the polarity of the solvent might have a significant effect on the partitioning of the these compounds into the chitosan particles. The results obtained from this study also confirmed what was previously described regarding the ability of chitosan to act as a 'fat magnet' or a 'fat sponge'.

A simple and efficient synthesis of nAChR antagonist (+/-)-7-methyl-2-exo-(3'-iodo-5'-pyridinyl)-7-azabicyclo[2.2.1]-heptane ((+/-)-NMI-EPB) has been developed. Both enantiomers of (+/-)-NMI-EPB were separated by semi-preparative chiral HPLC. The enantiomers manifested a substantial difference in their inhibition binding affinities ((+)-NMI-EPB, K(i)=2310, 1680 pM; (-)-NMI-EPB, K(i)=55, 68 pM). The enantiomers were stereoselectively radiolabeled with (11)C. In the distribution studies in the rodent brain [(11)C](-)-NMI-EPB specifically labeled nAChR whereas [(11)C](+)-NMI-EPB exhibited little specific binding. In the baboon PET study [(11)C](-)-NMI-EPB did not reach steady-state within 90 min post-injection suggesting that the radioligand may have some limitations for quantitative imaging.

Alpha series of novel 3,6-diazabicyclo[3.1.1]heptane derivatives 4a-f was synthesized and their affinity and selectivity towards alpha4beta2 and alpha7 nAChR subtypes were evaluated. The results of the current study revealed a number of compounds (4a, 4b and 4c) having a very high affinity for alpha4beta2 (K(i) at alpha4beta2 ranging from 0.023 to 0.056 nM) versus alpha7 nAChR subtypes; among these compounds, the 3-(6-bromopyridin-3-yl)-3,6-diazabicyclo[3.1.1]heptane 4c was found to be the most alpha7alpha4beta2 selective term in receptor binding assays (alpha7alpha4beta2=1295). Moreover, compound 4d also had high affinity for the alpha4beta2 nAChR subtype (K(i)=1.2 nM) with considerably high selectivity (alpha7/alpha4beta2=23300).

Extraction of dyes from aqueous solution was studied using liquid emulsion membrane. Study was carried out using two dyes, namely, crystal violet (CV) and methylene blue (MB). Extraction of single component system of each dye and their binary mixture were investigated. Liquid emulsion membrane was formed using n-heptane as membrane phase, sodium hydroxide solution as the internal phase and dye solution as the external phase. Surfactant span 80 was used as the emulsion stabilizer. Effects of concentration of span 80, concentration of NaOH, stirring speed, composition of feed solution and the volume ratio of the oil phase to the aqueous phase (O/A) were studied in detail both for single and binary system. Maximum extraction of MB was found to be 99% and that for CV was about 95% in single component system. In binary mixture, these values were 97% and 90%, respectively.

Here it is shown that the chemical nature of outer organic surfactant layers, used to stabilize inorganic nanoparticles (NPs), is a key factor controlling solubility in a mixed liquid CO(2)-heptane (10% vol) solvent.

The synthesis and reactivity of the 7-azabicyclo[2.2.1]hept-2-yl radical has been extensively investigated in inter- and intramolecular reaction processes for the first time. In this work we will present the preparation of the radical and its successful intermolecular reaction with radical acceptors such as tert-butylisocyanide and acrylonitrile. Computational analyses have been carried out to show and explain the mechanisms and stereochemical outcome of these transformations. Overall and from the chemical point of view, a new and convenient synthetic approach has been developed for the synthesis of exo-2-(cyano)alkyl substituted 7-azabicyclo[2.2.1]heptane derivatives, a series of compounds of wide interest for the synthesis of heterocyclic analogues of epibatidine. As a result, we describe here the synthesis of the tetrazoloepibatidines (8 and 15) and the oxadiazoloepibatidine (10).

Injection of large volumes of samples in solvents other than mobile phase composition has been proved for some less hydrophobic compounds. Thus, the retention behavior of several compounds of pharmaceutical interest (isosorbide-2-nitrate, isosorbide-5-nitrate, tropicamide, pentoxifylline, and methyl p-hydroxybenzoate) was studied by using different hydrophobic solvents (n-hexane, n-heptane, or i-octane) as sample solvents. Two types of stationary phases were used: octyl and octadecyl modified silica (both of Zorbax Eclipse type). The experiments showed a linear dependence between capacity factor of each solute and sample injection volume, up to maximum volume values of about 680 microL for C8 stationary phase and 580 microL for C18 stationary phase, when the solutes are no longer retained in stationary phase. Injection of large volumes of these hydrophobic solvents is thus possible in RP-LC with a gradual reduction of retention and peak efficiency. Two major conditions are however necessary in order to apply such an injection approach: the solutes must have a proper solubility in hydrophobic solvents and meanwhile they have to be less hydrophobic than the sample solvent in order to avoid competition with solvent molecules in partitioning between mobile and stationary phases.

Several isomers of 7-methyl-2-exo-([(18)F]fluoropyridinyl-5'-pyridinyl)-7-azabicyclo[2.2.1]heptane have been developed as radioligands with optimized brain kinetics for PET imaging of nAChR. The binding assay demonstrated that all isomers are beta-nAChR selective ligands with Ki = 0.02-0.3 nM. The experimental lipophilicity values of all isomers were in the optimal range for the cerebral radioligands (log D7.4= 0.67-0.99). The isomers with higher binding affinity manifested slow baboon brain kinetics, whereas the isomer with the lowest binding affinity (Ki = 0.3 nM) ((-)-7-methyl-2- exo-[3'-(6-[(18)F]fluoropyridin-2-yl)-5'-pyridinyl]-7-azabicyclo[2.2.1]heptane, [(18)F](-)-6c) and greatest lipophilicity (log D 7.4 = 0.99) exhibited optimal brain kinetics. [(18)F](-)-6c manifests a unique combination of the optimally rapid brain kinetics, high BP and brain uptake, and favorable metabolic profile. Pharmacological studies showed that (-)-6c is an alpha4beta2-nAChR antagonist with low side effects in mice. This combination of imaging properties suggests that [(18)F]-(-)- 6c is a potentially superior replacement for 2-[(18)F]fluoro-A-85380 and 6-[(18)F]fluoro-A-85380, the only available nAChR PET radioligands for humans.

Silica-based monolithic columns were prepared for HPLC with systematic variations of the tetramethoxysilane (TMOS) and polyethylene oxide (PEO) content as reactants in a sol-gel process accompanied by phase separation. The resulting monoliths showed differences in the macropore and silica skeleton diameter as well as in the corresponding domain sizes (the sum of macropore and skeleton diameter). All monoliths were synthesized with a diameter of 4.6 mm and cladded with a suitable polyaryletheretherketone (PEEK) polymer in a standardized and optimized manner for the subsequent chromatographic evaluation of the resulting monolithic HPLC columns. The columns were tested under normal phase conditions using n-heptane/dioxane (95:5 v/v) as a mobile phase and 2-nitroanisole as a test compound for the determination of separation efficiency and permeability. Two different sets of columns were prepared: the first one in which the amount of PEO was stepwise decreased to yield monoliths with identical macropore volumes and variations in the domain sizes. The second group of materials was synthesized adjusting both TMOS and PEO quantities to yield monolithic columns with identical macropore diameters of about 1.80 microm but different skeleton diameters and macropore volumes. The chromatographic results suggest that an increase in the column performance cannot be achieved by just arbitrarily decreasing the domain size of a given column. From a certain point of "downsizing" the monolithic structure a loss of structural homogeneity can be observed, which is apparently responsible for a lower chromatographic performance.

This study attempted to optimize the compositions of microemulsion mobile phase to model the drug penetration across blood-brain barrier (BBB) by microemulsion liquid chromatography (MELC). During the study, a continuous increase of the retentions along the operation time was found for all the test drugs. A correction method using methyl paraben and propranolol as the internal standards was proposed, which improved the reliability of the retention time significantly. The corrected retention factors were then used to develop the predictive model. The optimized MELC system with microemulsion consisting of 3.3% sodium dodecyl sulfate (SDS)-6.6% butanol-1.6% heptane-88.5% phosphate buffer (pH 7.0) showed superiorities to other lipophilicity measuring systems for modeling BBB penetration.

Nanoparticles containing fluorine-18 were prepared from block copolymers made by ring opening metathesis polymerization (ROMP). Using the fast initiating ruthenium metathesis catalyst (H2IMes)(pyr)2(Cl)2Ru=CHPh, low polydispersity amphiphilic block copolymers were prepared from a cinnamoyl-containing hydrophobic norbornene monomer and a mesyl-terminated PEG-containing hydrophilic norbornene monomer. Self-assembly into micelles and subsequent cross-linking of the micelle cores by light-activated dimerization of the cinnamoyl groups yielded stable nanoparticles. Incorporation of fluorine-18 was achieved by nucleophilic displacement of the mesylates by the radioactive fluoride ion with 31% incorporation of radioactivity. The resulting positron-emitting nanoparticles are to be used as in vivo molecular imaging agents for use in tumor imaging.

The possible mechanisms of the aminolysis of N-methyl-3-(methoxycarbonyl)-4-hydroxy-2-pyridone (beta-hydroxy-alpha,beta-unsaturated ester) with dimethylamine are investigated at the hybrid density functional theory B3LYP/6-31G(d,p) level in the gas phase. Single-point computations at the B3LYP/6-311++G(d,p) and the Becke88-Becke95 1-parameter model BB1K/6-311++G(d,p) levels are performed for more precise energy predictions. Solvent effects are also assessed by single-point calculations at the integral equation formalism polarized continuum model IEFPCM-B3LYP/6-311++G(d,p) and IEFPCM-BB1K/6-311++G(d,p) levels on the gas-phase optimized geometries. Three possible pathways, the concerted pathway (path A), the stepwise pathway involving tetrahedral intermediates (path B), and the stepwise pathway via alpha-oxo ketene intermediate due to the participation of beta-hydroxy (path C), are taken into account for the title reaction. Moreover, path C includes two sequential processes. The first process is to generate alpha-oxo ketene intermediate via the decomposition of N-methyl-3-(methoxycarbonyl)-4-hydroxy-2-pyridone; the second process is the addition of dimethylamine to alpha-oxo ketene intermediate. Our results indicate that path C is more favorable than paths A and B both in the gas phase and in solvent (heptane). In path C, the first process is the rate-determining step, and the second process is revealed to be a [4+2] pseudopericyclic reaction without the energy barrier. Being independent of the concentration of amine, the first process obeys the first-order rate law.

Salt-free 1:1 cationic/anionic (catanionic) surfactant mixture tetradecyltrimethylammonium laurate (TTAL) could be prepared by mixing equimolar tetradecyltrimethylammonium hydroxide (TTAOH) and lauric acid (LA) in water. Given the condition of suitable range of weight fraction of TTAL in total surfactant, rho=WTTAL/(WTTAL+WLA), and at existence of a small amount of water, it was found that the mixtures of so-obtained TTAL and LA could spontaneously form stable reverse vesicles in various organic solvents including toluene, tert-butylbenzene, and cyclohexane. The reverse vesicle phase shows a blue color against room light and exhibits strong birefringence under polarized microscope. The reverse vesicles are very sensitive to temperature change. Increasing temperature could make the rho values within which reverse vesicles were constructed move to higher values. In organic solvents of alkanes such as n-heptane, reverse vesicles could still form but become unstable upon time and centrifugation. Increasing temperature could accelerate phase separation, and finally a gel-like bottom phase was usually observed. Interestingly, the stable reverse vesicles formed by so-called salt-free catanionic surfactant mixtures still show some resistance against adding inorganic salts. They can trap inorganic ions such as Zn2+ and S2- into their hydrophilic layers. This opens the door for template applications of reverse vesicles to prepare inorganic nanoparticles.

Linear solvation energy relationships (LSERs) have more recently been proposed as the method of choice to describe and/or predict the partitioning behavior of neutral organic compounds over a large range of environmental matrices and for a broad variety of compounds in a consistent manner. However, when dealing with more complex, polar compounds with multiple functional groups, it has also been noted that there is a severe lack of substance descriptors quantifying the different intermolecular interactions that these compounds may undergo. In this study, we used a system of eight reversed phase, normal phase, and hydrophilic interaction HPLC systems to determine the substance descriptors for H-bond donor (A) and acceptor (B) interactions and for polarizability and dipolarity (S) for a set of 76 complex compounds containing multiple functional groups, comprising mainly pesticides and some pharmaceuticals. The obtained substance descriptors for most compounds are unique in that values of A, S, and B are high and lie at the very upper end of the numerical range of currently known substance descriptors. The substance descriptors have been cross-compared against literature values of the octanol-water (Kow) and air-water (Kaw) partition coefficients and against a set of heptan-methanol partition coefficients (Khm) experimentally determined with a consistent methodology herein. The comparison confirmed plausibility of the substance descriptors of all except six tested compounds. The newly determined substance descriptors promise to be highly valuable in chemicalfate modeling, allowing, in conjunction with available phase descriptors, for a better representation of partitioning of polar compounds in those models. The results also reveal a systematic deviation of the log Kow values predicted with our substance descriptors from the literature values. The deviation points toward a possible problem when existing LSER equations are applied to polar, multifunctional compounds with high values of A, S, and B. Hence, the substance descriptors determined herein should also be helpful in revisiting the validity of existing LSERs for complex, polar compounds.

Electrophoresis is widely used to determine the electrostatic potential of colloidal particles. Oil droplets in pure water show negative or positive electrophoretic mobilities depending on the pH. This is commonly attributed to the adsorption of hydroxyl or hydronium ions, resulting in a negative or positive surface charge, respectively. This explanation, however, is not in agreement with the difference in isoelectric point and point of zero charge observed in experiment. Here we present molecular dynamics simulations of oil droplets in water in the presence of an external electric field but in the absence of any ions. The simulations reproduce the negative sign and the order of magnitude of the oil droplet mobilities at the point of zero charge in experiment. The electrostatic potential in the oil with respect to the water phase, induced by anisotropic dipole orientation in the interface, is positive. Our results suggest that electrophoretic mobility does not always reflect the net charge or electrostatic potential of a suspended liquid droplet and, thus, the interpretation of electrophoresis in terms of purely continuum effects may need to be reevaluated.