Applications of environmentally benign supercritical water to organic syntheses.

Supercritical water (scH(2)O) is utilized for organic synthesis as an acid- or a base-catalyst as well as a useful replacement for organic solvents. There have been few works on the use of scH(2)O for acid- or base-catalyzed organic synthesis, because the ion product of scH(2)O is much lower than liquid water under certain conditions. Our recent studies by in situ Raman and IR spectroscopic measurements were allowed to expect the occurrence of acid- or base-catalysis of scH(2)O. Contrary to the conventional wisdom that acid- or base-catalyzed reactions will not take place in scH(2)O, these results indicated the possibilities of scH(2)O participating in Lewis acid- or base-catalysis, besides the Br?nsted acid-base function. In this paper, we thus demonstrate that the new-generation syntheses of lactam, arylated olefin, and monoterpene alcohols can be successfully created in scH(2)O.     

Molecularly imprinted polymers for triazine herbicides prepared by multi-step swelling and polymerization method. Their application to the determination of methylthiotriazine herbicides in river water

Uniformly-sized, molecularly imprinted polymers (MIPs) for atrazine, ametryn and irgarol were prepared by a multi-step swelling and polymerization method using ethylene glycol dimethacrylate as a cross-linker and methacrylic acid (MAA), 2-(trifluoromethyl) acrylic acid (TFMAA) or 4-vinylpyridine either as a functional monomer or not. The MIP for atrazine prepared using MAA showed good molecular recognition abilities for chlorotriazine herbicides, while the MIPs for ametryn and irgarol prepared using TFMAA showed excellent molecular recognition abilities for methylthiotriazine herbicides. A restricted access media-molecularly imprinted polymer (RAM-MIP) for irgarol was prepared followed by in situ hydrophilic surface modification using glycerol dimethacrylate and glycerol monomethacrylate as hydrophilic monomers. The RAM-MIP was applied to selective pretreatment and enrichment of methylthiotriazine herbicides, simetryn, ametryn and prometryn, in river water, followed by their separation and UV detection via column-switching HPLC. The calibration graphs of these compounds showed good linearity in the range of 50-500 pg/mL (r > 0.999) with a 100 mL loading of a river water sample. The quantitation limits of simetryn, ametryn and prometryn were 50 pg/mL, and the detection limits were 25 pg/mL. The recoveries of simetryn, ametryn and prometryn at 50 pg/mL were 101%, 95.6% and 95.1%, respectively. This method was successfully applied for the simultaneous determination of simetryn, ametryn and prometryn in river water.     

Novel crosslinked gels with starch derivatives. Polymer‐water interactions. Applications in waste water treatment.

Crosslinked polymers containing starch have been used for the recovery of various pollutants from aqueous solutions. These polymers have been prepared by reticulation of starch‐enriched flour using epichlorohydrin as crosslinking agent. Several studies (kinetics, time, concentration, role of crosslinking agent) are presented here. The results show that these polymers exhibit high sorption capacities toward substituted phenol derivatives. The mechanism of sorption is both physical and steric adsorption in the polymer network and/or the formation of hydrogen bond and hydrophobic interactions.     

The first Pummerer cyclisations on solid phase. Convenient construction of oxindoles enabled by a sulfur-link to resin

Alpha-sulfanyl N-aryl acetamides, attached to resin via the sulfur atom, undergo efficient Pummerer cyclisation upon activation of the sulfur link, to give oxindoles; heterocyclic products can be cleaved from the resin in a traceless manner using samarium(II) iodide.     

Applications of gas-liquid chromatography in protein chemistry. Determination of C-terminal sequences on nanomolar amounts of proteins.

A method for the determination of C-terminal amino acids and C-terminal amino acid sequences in nanomolar amounts of proteins is described, based on carboxypeptidase A digestion of the protein, followed by removal of the partially digested protein and quantitative gas-liquid chromatographic determination of the amino acids released after known time intervals. Sequences deduced from the kinetics of release of specific amino acids are compared with the known C-terminal sequences of well-characterized proteins.     

Novel chiral water soluble phosphines II. Applications in catalytic asymmetric hydrogenation

The results of the homogeneous asymmetric hydrogenation of several dehydroamino acids by rhodium-diene complexes of the chiral ligands; 2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(-bis(-p-N,N-dimethylaminophenyl)phosphino)butane, 2a; 2,4-bis(-bis(-p-N,N-dimethylaminophenyl)phosphino)pentane, 3a; and 2,3-bis(-bis(-p-N,N-dimethylaminophenyl)phosphino) butane, 4a; and their N-protonated and N-Me quaternized analogues are reported. The ligands comprise a versatile set which can be used both in organic and aqueous solvents. A detailed investigation of solvent and substituent effects is provided. The presence of p-NMe₂ groups enhances the rate of reaction in all cases. For the DIOP derivative, 2a, the presence of the dimethylamino group causes a reversal in the observed dominant product antipode. This is attributed predominantly to a change in preferred ligand conformation rather than to a kinetic difference between the two diastereomers of a single ligand conformation.     

Polarizable interaction potential for water from coupled cluster calculations. II. Applications to dimer spectra, virial coefficients, and simulations of liquid water

The six-dimensional CC-pol interaction potential for the water dimer was used to predict properties of the dimer and of liquid water, in the latter case after being supplemented by a nonadditive potential. All the results were obtained purely from first principles, i.e., without any fitting to experimental data. Calculations of the vibration-rotation-tunneling levels of (H(2)O)(2) and (D(2)O)(2), a very sensitive test of the potential surface, gave results in good agreement with experimental high-resolution spectra. Also the virial coefficients and properties of liquid water agree well with measured values. The present model performs better than published force fields for water in a simultaneous reproduction of experimental data for dimer spectra, virials, and properties of the liquid.     

Visualizing information in multivariate data: Applications to petroleum geochemistry : Part 1. Projection methods

General procedures are developed for revealing and comparing the information carried by experimental data obtained for different petroleum fractions. Oblique rotation of principal components is used to obtain projections amenable to geochemical interpretation. A systematic method is given for selecting markers, i.e., compounds related to specific geochemical factors. By projecting samples onto axes defined by markers, their potential for describing a petroleum fraction can be evaluated. The similarity between samples or groups (classes) of samples is revealed by projecting samples onto “geochemicalrdquo; axes and by comparing their residual distances to class models. In class modelling, projections on markers are proposed as a method for eliminating differences induced by alteration processes not related directly to the source of the oils, e.g., maturity.     

Determination of chlorophenoxy acid herbicides in water by in situ esterification followed by in-vial liquid-liquid extraction combined with large-volume on-column injection and gas chromatography-mass spectrometry

A new approach for rapidly analysing chlorophenoxy acid herbicides in water is presented. The chlorinated acids are derivatised with dimethyl sulphate in the water sample itself (800 microl) and, next, the methyl esters are extracted with 800 microl of n-hexane. A 200-microl volume of the extract is injected into the GC-MS system. The miniaturisation of both the methylation and extraction steps could be implemented because of the use of large-volume on-column injection and mass spectrometric detection. The optimisation of the methylation reaction for the simultaneous determination of (3,6-dichloro-2-methoxy)benzoic acid, (2-methyl-4-chlorophenoxy)- and (2,4-dichlorophenoxy)acetic acids, (+/-)-2-(4-chloro-2-methylphenoxy)- and 2-(2,4-dichlorophenoxy)propanoic acids and 4-(4-chloro-2-methylphenoxy)- and 4-(2,4-dichlorophenoxy)butyric acids showed that tetrabutylammonium salts act as catalysts. Addition of sodium hydroxide was required to obtain quantitative reaction yields for 4-(4-chloro-2-methylphenoxy)- and 4-(2,4-dichlorophenoxy)butyric acids. The methylation-cum-extraction procedure takes only 3 min per sample for a batch of seven samples. Linear calibration plots were obtained for the complete procedure and the limits of detection were of 10-60 ng/l with a signal-to-noise ratio (S/N) of 6. Relative standard deviations ranged from 8 to 15% (n=7) for analyte concentrations of 0.5 microg/l in surface water.     

Lipase-catalyzed kinetic resolution of cis-1-diethylphosphonomethyl-2-hydroxymethylcyclohexane. Application to enantioselective synthesis of 1-diethylphosphonomethyl-2-(5′-hydantoinyl)cyclohexane

A kinetic resolution of cis-1-diethylphosphonomethyl-2-hydroxymethylcyclohexane1 by lipase has been developed. The transesterification of (±)−1 with vinyl acetate in the presence of Lipase AK without solvent proceeded to give (+)−1 and the corresponding acetate (+)−5 in good yield and high enantiomeric ratio. The alcohol (+)−1 was transformed to the optically active hydantoins 12 and 13, possible intermediates for the synthesis of conformational constrained analogues of AP-5.     

The multi-step phosphorelay mechanism of unorthodox two-component systems in E. coli realizes ultrasensitivity to stimuli while maintaining robustness to noises

E. coli has two-component systems composed of histidine kinase proteins and response regulator proteins. For a given extracellular stimulus, a histidine kinase senses the stimulus, autophosphorylates and then passes the phosphates to the cognate response regulators. The histidine kinase in an orthodox two-component system has only one histidine domain where the autophosphorylation occurs, but a histidine kinase in some unusual two-component systems (unorthodox two-component systems) has two histidine domains and one aspartate domain. So, the unorthodox two-component systems have more complex phosphorelay mechanisms than orthodox two-component systems. In general, the two-component systems are required to promptly respond to external stimuli for survival of E. coli. In this respect, the complex multi-step phosphorelay mechanism seems to be disadvantageous, but there are several unorthodox two-component systems in E. coli. In this paper, we investigate the reason why such unorthodox two-component systems are present in E. coli. For this purpose, we have developed simplified mathematical models of both orthodox and unorthodox two-component systems and analyzed their dynamical characteristics through extensive computer simulations. We have finally revealed that the unorthodox two-component systems realize ultrasensitive responses to external stimuli and also more robust responses to noises than the orthodox two-component systems.     

Rapid access to t-butylalkylated olefins enabled by Ni-catalyzed intermolecular regio- and trans-selective cross-electrophile t-butylalkylation of alkynes

Among the carbo-difunctionalization of alkynes, the stereoselective dialkylation of alkynes is the most challenging transformation due to associated competitive side reactions and thus remains underdeveloped. Herein, we report the first Ni-catalyzed regio- and trans-selective cross-dialkylation of alkynes with two distinct alkyl bromides to afford olefins with two aliphatic substituents. The reductive conditions circumvent the use of organometallic reagents, enabling the cross-dialkylation process to occur at room temperature from two different alkyl bromides. This operationally simple protocol provides a straightforward and practical access to a wide range of stereodefined dialkylated olefins with broad functional group tolerance from easily available starting materials.

A direct reductive cross-dialkylation of alkynes is achieved to afford trans-dialkylated olefins using two distinct alkyl bromides. The reaction undergoes with exclusive chemo-, regio- and stereoselectivity without the use of organometallic reagents.     

The principles of infrared-x-ray pump-probe spectroscopy. Applications on proton transfer in core-ionized water dimers

In this paper we derive the basic physics underlying infrared-x-ray pump-probe spectroscopy (IR, infrared). Particular features of the spectroscopy are highlighted and discussed, such as dependence on phase of the infrared pulse, duration and delay time of the x-ray pulse, and molecular orientation. Numerical applications are carried out for the water dimer using wave packet techniques. It is shown that core ionization of the donor oxygen of the water dimer results in a drastic change of the potential with the global minimum placed in the proton transfer region. The results of the modeling indicate that IR-x-ray pump-probe spectroscopy can be used to study the dynamics of proton transfer in this core-ionized state, and that, contrary to conventional core level photoelectron spectroscopy, x-ray core-ionization driven by an IR field is a proper method to explore the proton transfer in a system like the water dimer. We observe that the trajectory of the nuclear wave packet in the ground state potential well is strongly affected by the absolute phase of the IR pulse.