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ORGANIC chemistry and PETROLEUM

CHEMISTRY education in universities & colleges and ORGANIC chemistry

Discusses a modern approach to teaching organic chemistry. Organic chemistry courses must begin with structure. Suggests using nuclear magnetic resonance spectroscopy to introduce structure; Introduce students to symmetry axes and planes; Review valence of hydrogen and first-row elements; Give them the equation for calculating the number of sites of unsaturation from the molecular formula; Give students the results of 13C{1H} DEPT with details later; More.

POLYMER research and MASS spectrometry

Examines proposed partial least squares (PLS) multivariate statistical models for predicting concentration of hydrocarbon- and oxygen-containing functional groups for a calibration set of model homopolymers. Plasma-deposited films; Static secondary ion mass spectrometry (SIMS); PLS modeling; Preprocessing; Prediction of surface oxygen and hydrogen concentration.

SEDIMENTATION & deposition research, OCEAN bottom, and CARBONATE minerals

Discusses the mechanism underlying the relative deposition rates of organic carbon and calcite to the sea floor. Effect of total calcite concentration on the specific depth at which calcite dissolves; Control of atmospheric carbon dioxide by ocean carbonate chemistry; Organic carbon degradation in the sediments.

GUMS & resins, ALLERGIES, COLOPHONS, GLYCERYL ethers, PATIENTS, and NUCLEAR magnetic resonance

In the esterification of rosin with glycerol, the main compound formed, glyceryl triabietate, shows low allergenic activity. In this study, compounds formed in smaller amounts, when abietic add (main component in rosin) was esterified with glycerol, were identified as glyceryl-1-monoabietate (GMA), glyceryl-1,2-diabietate (GDA,1,2) and glycery-1,3-diabietate (GDA1,3), using nuclear magnetic resonance (NMR), infra-red (IR) and mass spectrometry (MS) analyses. According to animal experiments, OMA was a contact allergen. No cross-reactivity was seen to allergens in unmodified rosin. Some patients allergic to unmodified rosin reacted when tested with GMA. No reactions were seen to the 2 diabietates. Some patients also reacted to commercial glycerol-modified rosins. OMA together with unmodified abietic acid were identified in these rosin samples. The reactions seen in rosin-sensitive patients to commercial glycerol-esterified rosins probably derive from the unmodified material still present in the product, but could also be the result of OMA obtained from the glycerol derivatization. [ABSTRACT FROM AUTHOR]

RING formation (Chemistry) and TRANSITION metals

Reviews the theoretical and mechanical metal-assisted cycloaddition transition reactions in organic chemistry. Organic and organometallic reactions; Schematically simulated reactions; Metal-assisted transition.

INSECT sex attractants, GRACILLARIIDAE, TORTRICIDAE, YPONOMEUTIDAE, OECOPHORIDAE, PYRALIDAE, GELECHIIDAE, and ALCOHOLS (Chemical class)

Field screening tests of 21 saturated and monounsaturated straight chain C12 and C14 alcohols and their acetates as well as some binary mixtures in dosages of 1 and 0.2 mg/dispenser were carried out in Lithuanian in 1993 and 1994. New sex attractants were determined for males of five moth species of the family Gracillariidae ( E10-12:OH for Phyllonorycter sorbi, E10-12Ac for Ph. cydoniella and Ph. oxyacanthae, Z10-12:OAc for Ph. junoniella, and a mixture of Z10-14:OAc with E9-14:OAc in a 1:10 for Ph. sylvella), for four species of the family Tortricidae ( E10-14:OAc for Endothenia ericetana, Z10-14:OAc in a 10:1 mixture with E11-14:OAc for Eudemis pozphyrana, E11-14:OAc in a 10:1 mixture with E11-14:OH for Dichrorampha petiverella and Cochylis dubitana), for two species of Gelechiidae ( Z9-14:OAc in a mixture with either Z10-14:OAc in a ratio 1:1, E9-14:OAc in a ratio 1:10 or E10-14:OAc in a ratio 10:1 for Bryotropha galhanella, Z10-14:OAc and E9-14:OAc in a ratio 10:1 for B. mundella), as well as for one species of each of the families Yponomeutidae ( Z7-14:OAc for Paraswammerdamia lutarea) and Oecophoridae ( Z10-14:OAc and E9-14:OAc in a ratio 10:1 for Pseudatemelia josephinae). Preliminary composition of sex attractants was established for three moth species of the family Gracillariidae ( Z10-14:OAc in a 1:10 mixture with E9-14:OAc for Phyllonorycter heegerella, Ph. coryli and Ph. dubitella) and for one species of the family Gelechiidae ( Z9-14:OAc for Bryotropha terella). Inhibitors of the sex attractants were found for four leafminer species of the family Gracillariidae ( Z7-, Z9- and Z10-12:OAc for Phyllonorycter sorbi, Z10-, E10-12:OH and E10-14:OH for Ph. mespilella, E10-12:OH for Ph. cydoniella, Z10-12:OH and E10-14:OH for Ph. oxyacanthae), for three species of Tortricidae ( E9-, Z11- and E11-14:OAc for Endothenia ericetana, E11-14:OAc for Gypsonoma minutana, E10- and E11-14:OAc for Epagoge grotiana), and for one species from the family Pyralidae ( Z10-, E10- and E11-14:OAc for Pyrausta aurata). Data from male behaviour tests in tube olfactometers are presented for Phyllonorycter blancardella, Ph. sorbi, Ph. dubitella and Ph. strigulatella and active compounds revealed. [ABSTRACT FROM AUTHOR]

LEAFMINERS, INSECT sex attractants, and PHEROMONES

Dodecyl acetate (12:OAc) (E)-10-dodecenyl acetate (E10-12:OAc) and (E)-10-dodecenol (E10-12:OH) in the ratio 8 : 80 : 12 were collected by solid phase micro-extraction of the volatiles emitted by virgin signalling females of the spotted tentiform leafminer moth, Phyllonorycter blancardella. The same compounds in the ratio 8 : 79 : 13 were extracted from the sex pheromone glands of virgin signalling females of the same species. The chemical structures of the compounds were identified by gas chromatography and mass spectrometry. Trapping results obtained from field tests using synthetic components of the sex pheromone demonstrated that only one component, E10–12:OAc, was essential for the attraction of conspecific males and should be considered as a sex pheromone. [ABSTRACT FROM AUTHOR]

THERMAL analysis, THERMODYNAMICS, INORGANIC chemistry, ORGANIC compounds, and POLYMERS

Summarizes developments and applications in thermal analysis that appeared in Chemical Abstracts from October 1997 to October 1999. Instrumentation; Thermodynamic measurements; Kinetic considerations; Inorganic chemistry; Organic and polymeric materials; Biochemical and natural products; Pharmaceutical applications; Minerals.

OLFACTORY nerve, TOBACCO, MOTH flies, SMELL, CHROMATOGRAPHIC analysis, and ELECTROPHYSIOLOGY

An important question in olfaction is for which odorants receptor neurones have evolved. In the present study, olfactory receptor neurones on the antennae of the tobacco budworm moth Heliothis virescens were screened for sensitivity to naturally occurring plant-produced volatiles by the use of gas chromatography linked to electrophysiology. Volatiles of host as well as non-host plants collected by headspace techniques were used for stimulating the neurones, sequentially via two columns, one polar and one nonpolar installed in parallel in the gas chromatograph. Three types of neurones presented in this paper responded to one, two or three compounds for which the retention times were determined in both column types. The chemical structures of the active components were determined on the basis of mass spectrometry linked to gas chromatography, indicating E-β-ocimene and β-myrcene as stimulants for neurone type 1, E,E-α-farnesene for neurone type 2 and homo-farnesene for neurone type 3. Re-testing authentic materials verified the identifications for the type 1 neurones. The results demonstrate a high specificity for the three types of neurones by strong responses to one or two structurally similar compounds out of hundreds present in a large variety of plants. The study exemplifies plant odour detection by narrowly tuned receptor neurones in a polyphagous moth species. [ABSTRACT FROM AUTHOR]

CETACEA, ENANTIOSELECTIVE catalysis, POLYCHLORINATED biphenyls, and TOXICOLOGY

Isomer-specific concentrations of 41 polychlorinated biphenyls (PCBs) and the enantiomeric ratios (ER) of nine chiral PCBs were determined in the liver of four cetacean species--Risso's dolphin (Grampus griseus), bottlenose dolphin (Tursiops truncatus), fin whale (Balaenoptera physalus), and long-finned pilot whale (Globicephala melaena)--found dead in the Mediterranean Sea. The total PCB concentration (sum of 41 congeners) ranged from 484 to 63,200 ng/g wet weight. The 2,3,7,8 tetrachlorodibenzo- p-dioxin (TCDD) toxic equivalents (TEQs), as defined by the World Health Organization (WHO), ranged from 4.3 to 1,454 pg/g wet weight. The contribution of mono-ortho PCBs was consistently higher than non-ortho PCB congeners, in whale species, whereas in dolphins this predominance was not so clear. The PCB profiles were dominated by congeners 138, 153, and 180 in almost all the investigated samples. Comparison of PCB profiles by using principal component analysis allowed to separate the species into different groups. Polychlorinated biphenyls 170 and 180 seem to be eliminated by the two whale species, and PCB 180 also seems to be eliminated by Risso's dolphins. The PCBs 95, 132, 149, and 176 revealed an enantiomeric excess of the second eluted enantiomer in almost all the cetaceans investigated, where 136 and 174 were racemic or almost racemic. It is the first time that an enantiomeric excess of PCB 84 and 91 has been reported in biological samples. Although it was only possible to calculate them in two dolphin liver samples, the high values of enantiomeric excess found are surprising (86.3 and 32% for PCB 91 and 84, respectively). [ABSTRACT FROM AUTHOR]

ACYLATION, QUINOLINE, AMINES, and HYDROGEN bonding

A significant acceleration of acyl transfer has been achieved on 8-acetoxy-2-oxazolinylquinoline in the presence of benzylamine. Comparison of the aminolysis by the new acylating reagent with that of 8-acetoxyquinoline and 8-acetoxyquinoline-2-carbonitrile has been carried out. The results of these experiments suggest that the proximity of a supplementary basic atom to the ester group increases the participation effect of the basic site mainly by formation of a possible second hydrogen bond. The association constant of benzylamine into the basic cavity of 8-methoxy-2-oxazolinylquinoline (Ka=80 M−1) has been measured by 1H NMR titration experiments. [Copyright &y& Elsevier]

PRINTING, MOLECULAR self-assembly, and MONOMOLECULAR films

A technique for generating a general screening platform consisting of dots of immobilized beads on silicon has been developed via self-sorting and -assembly of different kinds of beads. The dots are defined by a teflon-like film, which due to its hydrophobic characteristics also prevents cross-contamination of liquid from different dots. To enable functionalization of individual dots with different target molecules simultaneously a new way of microcontact printing has been explored where different target solutions are printed in parallel using one stamp. In order to show that this platform can be designed for both biochemical assays and organic chemistry, streptavidin-, amino- and hydroxy-functionalized beads have been self-sorted and -assembled both on separate and common platforms. The self-sorting and -arrangement are based on surface chemistry only, which has not previously been reported. Beads of different sizes and material have successfully been immobilized in line patterns as narrow as 5 μm. Besides silicon, quartz and polyethylene have also been used as substrates. [Copyright &y& Elsevier]

STEREOCHEMISTRY and ENANTIOSELECTIVE catalysis

For the description of the stereoselectivity of (bio)catalytic asymmetric reactions which may proceed via different regio- or stereo-isomeric pathways (e.g. catalysed by epoxide hydrolases, dehalogenases, sulfatases or glycosidases), a parameter ‘RI’ (Retention–Inversion ratio) was introduced in analogy to the Enantiomeric Ratio (E), which describes enantioselectivity. A computer program was developed for the treatment of the kinetics of such single-step processes, which offer the potential of deracemization, i.e. a single stereoisomeric product is formed from a racemate in an enantioconvergent fashion. By analysis of experimentally determined progress curves of the enantiomeric excess of substrate and product (e.e.S, e.e.P, respectively) and the conversion (c), relative first-order rate constants ki, the enantioselectivity (E) and the RI ratio (RI) can be determined; in addition, processes can be simulated based on assumed ki values. [Copyright &y& Elsevier]

NATURAL products, HYDROLYSIS, and EPOXY compounds

A short chemoenzymatic route to two natural products—the first, a constituent of Jamaican rum and the second the (+)-antipode of the gibberelin synergist (−)-Pestalotin—was accomplished based on an enzyme-triggered cascade-reaction. Thus, a racemic halomethyl oxirane was hydrolyzed by bacterial epoxide hydrolases to furnish the corresponding vic-halomethyl-diol, which underwent spontaneous ring-closure to furnish an epoxy alcohol in up to 93% e.e. and ≥99 d.e. Due to the fact that this process was enantioconvergent, the occurrence of the undesired enantiomer was entirely avoided. [Copyright &y& Elsevier]

ESTRONE, CHLOROFLUOROCARBONS, and IRRADIATION

A rapid and efficient deuteration procedure was developed for estrone. Irradiation of estrone in CF3COOD in a microwave oven gave [2,4,16,16-2H4]-estrone in 95% yield. Ultrasound and CF3COOD reflux deuterations of estrone were also studied. [Copyright &y& Elsevier]

COMBINATORIAL chemistry, SOLID-phase analysis, and MICROWAVE heating

Recent advances in microwave-assisted combinatorial chemistry include high-speed solid-phase and polymer-supported organic synthesis, rapid parallel synthesis of compound libraries, and library generation by automated sequential microwave irradiation. In addition, new instrumentation for high-throughput microwave-assisted synthesis continues to be developed at a steady pace. The impressive speed combined with the unmatched control over reaction parameters justifies the growing interest in this application of microwave heating. [ABSTRACT FROM AUTHOR]

GERMACRENE, OVIPARITY, TOBACCO budworm, BUD-moth, OLFACTORY receptors, NEURONS, and ANTENNAE (Biology)

The sesquiterpene germacrene D (GD) activates a major type of olfactory receptor neuron on the antennae of the heliothine moths. In Heliothis virescens females, 80% of the recordings have shown activity of one neuron type responding with high sensitivity and selectivity to GD. With the aim of determining the behavioural significance of this sesquiterpene, we have used a two-choice wind-tunnel to study the preference of mated H. virescens females for host plants with and without (-)-GD added. Tobacco plants containing dispensers with low release rate of (-)-GD had a greater attractiveness than tobacco plants without this substance. In addition, a significant increase of oviposition was found on the plants with (-)-GD. [ABSTRACT FROM AUTHOR]

ESTERS, ENANTIOSELECTIVE catalysis, and ENANTIOMERS

Enantioselective biohydrolysis of sec-alkyl sulfate esters using a bacterial alkylsulfatase from Rhodococcus ruber DSM 44541 proceeded in a stereoselective fashion though inversion of configuration. Thus, from racemic substrates, the corresponding (R)-enantiomers were hydrolyzed selectively to furnish the corresponding sec-alcohol and non-reacted sulfate ester, both of (S)-configuration, which represents a homochiral product mixture. The enantioselectivities were found to depend on the substrate structure and were optimal for sec-sulfate esters in the ω-1 position (up to E=21). Since the enzyme was inactive on prim-sulfate esters, it can be classified as a sec-alkylsulfatase [EC 3.1.6.X]. [Copyright &y& Elsevier]

ESTERS, HYDROLYSIS, and ENANTIOMERS

The Enantioselectivity of the biohydrolysis of sec-alkyl sulfate esters using a bacterial alkylsulfatase from Rhodococcus ruber DSM 44541 was dramatically enhanced in presence of additives (‘enhancers’) such as carbohydrates, polyethylene glycol, detergents, metal ions and through enzyme immobilization. In presence of iron, the E value for the kinetic resolution of (±)-3- and (±)-4-octyl sulfate was improved from E=3.9 to ≥200 and E=1.1 to 10, respectively. [Copyright &y& Elsevier]

OXAZOLES, CATALYSTS, and LIGANDS (Biochemistry)

Metal complexes of chiral oxazoline derivatives immobilized on soluble as well as insoluble supports serve as versatile asymmetric catalysts in a variety of applications. In a few cases recovery and reuse of the chiral ligands have been achieved. [Copyright &y& Elsevier]

POLYTEF, BUFFER solutions, and LIGHT emitting diodes

The polytetrafluoroethylene (Teflon) was utilized as buffer layer to improve the performance of organic light emitting diodes (OLEDs). In the ITO/Teflon/N,N′-diphenyl-N,N′-(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD)/tris(8-hydroxy-quinoline) aluminum (Alq3)/Ca/Ag device, the Teflon film helped to enhance the hole tunneling injection and effectively impede indium diffusion from the ITO electrode. Compared with the devices without Teflon, the turn-on voltage was lowered by 1.5 V due to the introduction of Teflon buffer, and the optimized devices exhibited a luminous efficiency double that of the devices without Teflon layer, and the device lifetime proved to be dramatically increased. [Copyright &y& Elsevier]

KERATIN, SHEEP, and PROTEOGLYCANS

Recently, we reported the isolation and partial characterization of keratan sulphate (KS) from sheep brain. In this study, a panel of monoclonal antibodies (Mab) recognizing epitopes within KS chains and core proteins of KS-containing proteoglycans were used to detect, by immunoblotting, antigenically related molecules extracted from cerebrum, cerebellum and brainstem, respectively. Although the intensity of labelling varied with each of the antibodies, the brain KSPGs were recognized by all the monoclonals used, confirming the presence of KS side chains, which react with the Mabs: 5-D-4, EFG-11, EFG-4, I22, as also the presence of KSPGs related to phosphacan-KS (3H1 proteoglycan). Extracts of all the three brain areas could bind both anti-KS and anti-core protein Mabs, as also anti-HNK-1 monoclonal antibody. Binding was sensitive to keratanases degradation in the cerebrum and brainstem except cerebellum where the presence of a large molecular size hybrid CS/KSPG bearing KS chains partially resistant to keratanases was identified. This population reacts only with 5-D-4, EFG-11 and EFG-4 antibodies. Furthermore, the presence of HNK-1 epitope in CSPGs was detected in the cerebellum and brainstem. In contrast, in the cerebrum the coexistence of HNK-1 epitope and KS in KSPGs was identified. These data suggest that the KSs of sheep brain are part of proteoglycans containing protein and KS antigenic sites related to those of corneal and cartilage KSPG, as also of the brain proteoglycan phosphacan-KS. [Copyright &y& Elsevier]

AEROSOLS and ATMOSPHERIC chemistry

Atmospheric aerosols play a central role in climate and atmospheric chemistry. Organic matter frequently composes aerosol major fraction over continental areas. Reactions of natural volatile organic compounds, with atmospheric oxidants, are a key formation pathway of fine particles. The gas and particle atmospheric concentration of organic compounds directly emitted from conifer leaf epicuticular wax and of those formed through the photooxidation of α- and β-pinene were simultaneously collected and measured in a conifer forest by using elaborated sampling and G/ MS techniques. The saturation concentrations of acidic and carbonyl photooxidation products were estimated, by taking into consideration primary gas- and particle-phase organic species. Primary organic aerosol components represented an important fraction of the atmospheric gasphase organic content. Consequently, saturation concentrations of photooxidation products have been lowered facilitating new particle formation between molecules of photooxidation products and semi-volatile organic compounds. From the measured concentrations of the abovementioned compounds, saturation concentrations (C[sub sat, i]) of α- and β-pinene photooxidation products were calculated for nonideal conditions using a previously developed absorptive model. The results of these calculations indicated that primarily emitted organic species and ambient temperature play a crucial role in secondary organic aerosol formation. [ABSTRACT FROM AUTHOR]

DYNAMICS and ACETONE

Whole lyophilised cells of Rhodococcus ruber DSM 44541 were employed for the oxidative kinetic resolution of sec-alcohols using acetone as hydrogen acceptor. The enantioselectivity of this process could be controlled effectively by introducing C&z.sbnd;C multiple bonds into substrates, which were inefficiently recognised, in particular short-chain (ω-1)-alcohols and (ω-2)-analogs. Thus, the enantioselectivities of rac-2-pentanol (E=16.8) and rac-3-octanol (E=13.3) were significantly improved by introducing a C&z.dbnd6;C bond adjacent to the alcohol moiety to give racemic (E)-pent-3-en-2-ol and 4-(E)-octen-3-ol, which were resolved with excellent selectivities (E >100 and 50, respectively). In addition, it was found that high stereodifferentiation between the E- and Z-configured double bonds occurred, as the corresponding (Z)-isomers were not converted. Similar selectivity-enhancing effects were observed with acetylenic analogs. [Copyright &y& Elsevier]

COUPLING constants and PROTONS

A new method for heteronuclear X-filtering is presented, which relies on repetitive applications of 90°(1H)–τ(1/41JHC)–180°(1H,13C)–τ(1/41JHC)–90°(1H,13C)–PFG building blocks employing gradient-mediated suppression of magnetization built up for directly heteronuclear coupled protons. Thereby, a range of heteronuclear coupling constants can be suppressed by varying the delays of scalar coupling evolution both within and between individual transients. To achieve efficient destruction of 13C-coupled protons in macromolecular systems, the scalar coupling evolution delays were optimized using simulated annealing by including transverse relaxation effects. With a combination of regular hard pulses, delays and pulsed field gradients only, this method yields sufficient X-filtering to allow the observation of intermolecular nuclear overhauser effects in a molecular complex consisting of a 13C, 15N double-labeled, and an unlabeled protein. This is achieved by exciting magnetization of 12C- and 14N-bound protons and detecting 13C-bound 1H magnetization in a 3D 13C-filtered, 13C-edited NOESY–HSQC experiment. The method is tested on the 18 kDa homodimeric bacterial antidote ParD. [Copyright &y& Elsevier]

AMINO alcohols and CHEMICAL reagents

A large set of syn- and anti-1,2-amino alcohols has been synthesized. Upon comparison of the CH¯O and CH¯N 1H NMR shifts a general trend has been observed, making it possible to determine the relative configuration of 1,2-amino alcohols without derivatization or shift reagents. [Copyright &y& Elsevier]

AMINO alcohols and LIGANDS

(R,R)-Threoninol was prepared in one step from l-threonine in 86% isolated yield. The product was regioselectively transformed into 2,2-bis[(4R,5R)-4-(hydroxymethyl)-5-methyl-1,3-oxazolin-2-yl]propane in 42% isolated yield. [ABSTRACT FROM AUTHOR]

AMINO acids and ORGANIC synthesis

Six chiral amino sulfides have been synthesised from the amino acids phenylalanine, phenylglycine and valine. These amino sulfides were used as chiral ligands in the asymmetric addition of n-butyllithium and metyllithium to various aldehydes at low temperatures. The highest stereoselectivities were obtained with benzaldehyde, resulting in 1-phenyl-1-pentanol and 1-phenyl-1-ethanol in enantiomeric excesses of >98.5 and 95%, respectively. These stereoselectivities were significantly higher than those induced by the ether analogues. [Copyright &y& Elsevier]

ODORS, PLANTS, PISSODES, GAS chromatography, ALCOHOL, and CLUSTER pine

Plants release complex mixtures of volatiles important in the interaction with insects and other organisms. In the search for compounds that contribute to the perception of odour quality in the weevil Pissodes notatus, single olfactory receptor neurones on the antennae were screened for sensitivity to naturally produced plant volatiles by the use of gas chromatography linked to single cell recordings. We here present 60 olfactory neurones responding to 25 of the numerous compounds released by host and non-host plants. All the neurones show high selectivity and are classified into 12 distinct types. The two most abundant types respond to α-pinene, β-pinene, and 3-carene (n=17), and to isopinocamphone and pinocamphone (n=17), respectively. Other neurone types respond to limonene (n=9), β-phellandrene (n=3), and fenchone (n=4). Responses to β-caryophyllene (n=1) and to ethanol (n=4) are also shown. Except for two pairs, the neurone types do not show overlap of the molecular receptive range. The active compounds are present in the host, Pinus pinaster, as well as in non-hosts, supporting the idea that plant odour quality is mediated by the ratio of the compounds rather than specific odorants. [ABSTRACT FROM AUTHOR]

PERESKIA and ALCOHOL dehydrogenase

The organic solvent-stable redox-system of Rhodococcus ruber DSM 44541, which allows the efficient oxidation/reduction of sec-alcohols/ketones at the expense of acetone/2-propanol, respectively, as cosubstrate was optimized with respect to a maximum of alcohol dehydrogenase activity during cell growth. Comparison of the fermentation of R. ruber DSM 44541 in shake flasks cultures (1 l flask with 250 ml medium) and in a bioreactor (15 l with 10 l working volume) revealed that the desired organic solvent-stable alcohol dehydrogenase activity reached its maximum during the log phase for the bioreactor. In contrast, in shake flasks the maximum of activity was reached during the stationary phase. [Copyright &y& Elsevier]

ESTROGEN and ESTRADIOL

The estrogen metabolite 2-methoxyestradiol was synthesized from estradiol bis-THP-ether which was 2-hydroxylated using the superbase LIDAKOR, trimethyl borate, and H2O2, then methylated and deprotected to obtain 2-methoxyestradiol in three steps and 61% yield. 2-Hydroxyestradiol was obtained by deprotecting the 2-hydroxyestradiol bis-THP-ether from the first step. [Copyright &y& Elsevier]

LEWIS acids, AMMONIUM, and YLIDES

An investigation of the Lewis acid mediated [2,3]-sigmatropic rearrangement of allylic ammonium ylides has been conducted by employing various bases and boron Lewis acids. Using BBr3 together with the phosphazene base 6, various allylic amines could be rearranged in good yields with low to excellent diastereoselectivity. [Copyright &y& Elsevier]

CHITOSAN and FOURIER transform infrared spectroscopy

The surface of chitosan films was modified using acid chloride and acid anhydrides. Chemical composition at the film surface was analyzed by attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). ATR-FTIR data verified that the substitution took place at the amino groups of chitosan, thus forming amide linkages, and the modification proceeded to the depth at least 1 μm. Choices of molecules substituted at the amino groups of the glucosamine units did affect the hydrophobicity of the film surface, as indicated by air–water contact angle analysis. The surface became more hydrophobic than that of non-modified film when a stearoyl group (C17H35CO&z.sbnd;) was attached to the films. The reaction of chitosan films with succinic anhydride or phthalic anhydride, however, produced more hydrophilic films. Selected modified films were subjected to protein adsorption study. The amount of protein adsorbed, determined by bicinchoninic acid (BCA) assay, related to the types of attached molecules. The improved surface hydrophobicity affected by the stearoyl groups promoted protein adsorption. In contrast, selective adsorption behavior was observed in the case of the chitosan films modified with anhydride derivatives. Lysozyme adsorption was enhanced by H-bonding and charge attraction with the hydrophilic surface. While the amount of albumin adsorbed was decreased possibly due to negative charges that gave rise to repulsion between the modified surface and albumin. This study has demonstrated that it is conceivable to fine-tune surface properties which influence its response to bio-macromolecules by heterogeneous chemical modification. [Copyright &y& Elsevier]

MOLYBDENUM, VANADIUM, MICROCLUSTERS, and CRYSTALLOGRAPHY

Two novel trimetallic nanocluster complexes, {MoVI6MoV2VIV8O40(PO4)[Co(phen)2(H2O)]2}[Co2(phen)2(OH)2(H2O)4]1/2 (1) (phen = 1,10-phenanthroline) and {MoVI5MoV3VIV8O40(PO4)[Co(phen)(en)(H2O)]2}[Co(phen)3] ·1.5H2O (2) (phen = 1,10-phenanthroline, en = ethylenediamine), which are the first examples of mixed molybdenum-vanadium polyoxoanion bridged cluster complexes, have been hydrothermally prepared and characterized by X-ray crystallography. [ABSTRACT FROM AUTHOR]

PYRIDINIUM compounds and SOLID-phase synthesis

Pyridinium chlorochromate adsorbed on neutral alumina (PCC-Al2O3) under solvent-free conditions has been found to oxidize primary aliphatic alcohols to alkyl alkanoates whereas primary benzylic and primary allylic alcohols produce the corresponding aldehydes. Secondary aliphatic and aromatic alcohols produce ketones without isomerization and polymerization of double bonds, overoxidation and other side-reactions. [Copyright &y& Elsevier]

MOTHS, OLFACTORY nerve, INSECT food, SESQUITERPENES, TERPENES, and COMPARATIVE physiology

Specificity of olfactory receptor neurones plays an important role in food and host preferences of a species, and may have become conserved or changed in the evolution of polyphagy and oligophagy. We have identified a major type of plant odour receptor neurones responding to the sesquiterpene germacrene D in three species of heliothine moths, the polyphagous Heliothis virescens and Helicoverpa armigera and the oligophagous Helicoverpa assulta. The neurones respond with high sensitivity and selectivity to (–)-germacrene D, as demonstrated by screening via gas chromatography with numerous mixtures of plant volatiles. Germacrene D was present in both host and non-host plants, but only in half of the tested species. The specificity of the neurones was similar in the three species, as shown by the "secondary" responses to a few other sesquiterpenes. The effect of (–)-germacrene D was about ten times stronger than that of the (+)-enantiomer, which again was about ten times stronger than that of (–)-α-ylangene. Weaker effects were obtained for (+)-β-ylangene, (+)-α-copaene, β-copaene and two unidentified sesquiterpenes. The structure-activity relationship shows that the important properties of (–)-germacrene D in activating the neurones are the ten-membered ring system and the three double bonds acting as electron-rich centres, in addition to the direction of the isopropyl-group responsible for the different effects of the germacrene D enantiomers. [ABSTRACT FROM AUTHOR]

FURANS and NATURAL products

The synthesis of 5- and 3-(1′-hydroxyalkyl)-substituted 5H-furan-2-ones 4a–d and 8a–d as well as 5-alkylidene-5H-furan-2-ones 5a–d is described. A study of the structure–activity relationship of these furanone-based natural product analogues towards two different quorum sensing systems is reported. Although the synthesized compounds are not as potent quorum sensing inhibitors as some natural counterparts and a synthetic analogue hereof, interesting structure–activity relationships are seen. [Copyright &y& Elsevier]

ENANTIOMERS, STEREOCHEMISTRY, and ORGANIC synthesis

A single enantiomer of a (stereo)chemically labile allylic-homoallylic alcohol was obtained in 91% e.e. and 96% yield from the racemate by employing a lipase-catalysed kinetic resolution coupled to in situ inversion under carefully controlled (Mitsunobu) conditions in order to suppress side reactions, such as elimination and racemisation. This technique was successfully applied to an enantio-convergent asymmetric total synthesis of the algal fragrance component (S)-dictyoprolene. [Copyright &y& Elsevier]

THIOPHENES, CHEMICAL reagents, and DITHIOLE

A detailed study of the reactions of phosphorus pentasulfide and Lawesson''s reagent with a series of 4,5-bis(RCOCH2S)-1,3-dithiole-2-thiones (R=Ph, 4-MeOC6H4, 4-Br C6H4, Me) has been carried out. These reactions lead to fusion of either an unsaturated 1,4-dithiin ring or a thiophene to the dithiole; the former in higher yield, while the latter is a significant product in the reactions with Lawesson''s reagent; as well as small amounts of minor products. A mechanistic rationalization of these products is discussed in some detail. The new fused dithioles have been converted to novel series of fused TTF derivatives. [Copyright &y& Elsevier]

KETONES, ACETONE, OXIDATION, and ORGANIC compounds

For the development of a ‘green’ oxidation method, the transformation of 4-(p-hydroxyphenyl)butan-2-ol (rhododendrol) into 4-(p-hydroxyphenyl)butan-2-one (raspberry ketone) was used as a model reaction. Different lyophilized cells of Rhodococcus spp. have been screened for their ability to perform the desired oxidation. Rhodococcus equi IFO 3730 and R. ruber DSM 44541 were able to use acetone as a hydrogen acceptor in a hydrogen transfer-like process. The oxidation can be performed at substrate concentrations up to 500 g/L. [Copyright &y& Elsevier]

DIELS-Alder reaction, CHEMICAL reactions, HETEROCYCLIC compounds, LEWIS acids, ACID-base chemistry, and ORGANIC chemistry

Asymmetric Diels-Alder reactions with 2H-azirines as dienophiles have been studied. Diastereoselective reactions with an enantiopure azirine 1b, bearing a chiral auxiliary, gave substituted biand tricyclic tetrahydropyridines in high yield and stereoselectivity, under the influence of a Lewis acid. The novel enantioselective [4+2] cycloaddition reaction of 3-benzyl-2H-azirine carboxylate with cyclopentadiene was investigated with various chiral Lewis acid complexes and provided the corresponding tetrahydropyridines in moderate to low yield and enantioselectivity. [ABSTRACT FROM AUTHOR]

HYDROLYSIS, BIOTRANSFORMATION (Metabolism), ETHYLENE oxide, and METABOLISM

Asymmetric biohydrolysis of trisubstituted terpenoid oxiranes (rac-1a–rac-3a) was accomplished by employing the epoxide hydrolase activity Rhodococcus and Streptomyces spp. Depending on the biocatalyst, the biohydrolysis proceeded in an enantio-convergent fashion and gave the corresponding vic-diols in up to 97% ee at conversions beyond the 50%-threshold. In order to avoid a depletion of the ee of product by further oxidative metabolism, bioconversions had to be conducted in an inert atmosphere with exclusion of molecular oxygen. The synthetic applicability of this method was demonstrated by the asymmetric total synthesis of the monoterpenoid coumarin (R)-(+)-Marmin in 95% ee. [Copyright &y& Elsevier]

TITANIUM dioxide, SOLAR cells, ETHER (Anesthetic), SURFACES (Technology), THIN films, and SOLID state physics

We report for the first time the preparation method of compact TiO2 film using titanium butoxide-petroleum ether solution, by means of dipping and sintering. Our estimation of the component of this thin film was confirmed by XPS test. Studies of AFM showed the influence of preparation condition upon surface morphology. The transmitted spectrum of this compact TiO2 film was also investigated, which presented an excellent transmittance of this film in the visible light region. We arrive at a conclusion, according to the I-V characteristics of solid-state Grätzel solar cells utilizing this kind of compact film, that this compact TiO2 film functions well in secluding the conducting substrate from the hole-conducting material. [ABSTRACT FROM AUTHOR]

SICK building syndrome, PRINCIPAL components analysis, PHYSIOLOGICAL effects of humidity, VOLATILE organic compounds, and INDOOR air pollution

In this study, we were able to separate buildings with high and low prevalence of sick building syndrome (SBS) using principal component analysis. The prevalence of SBS was defined by the presence of at least one typical skin, mucosal and general (headache and fatigue) symptom. Data from the Swedish Office Illness Study describing the presence and level of chemical compounds in outdoor, supply, and room air, respectively, were evaluated together with information about the buildings in six models. When all data were included the most complex model was able to separate 71% of the high prevalence buildings from the low prevalence buildings. The most important variable that separates the high prevalence buildings from the low prevalence buildings was a more frequent occurrence or a higher concentration of compounds with shorter retention time in the high prevalence buildings. Elevated relative humidity in supply and room air and higher levels of total volatile organic compounds in outdoor and supply air were more common in high prevalence buildings. Ten building variables also contributed to the separation of the two classes of low and high prevalence buildings. Principal component analysis (PCA) can be a tool to evaluate variables that may cause Sick Building Syndrome. The method is promising, but more development of the technique, and a deeper understanding of how different type and specificity of input variables influence the modeling result are needed before PCA can be used as a practical tool. [ABSTRACT FROM AUTHOR]

CARBOXYPEPTIDASES, GUANIDINE, PROPIONIC acid, and GUANIDINES

A series of 3-mercapto-propionic acid derivatives that function as reversible inhibitors of carboxypeptidase U have been prepared. We present a successful design strategy using cyclic, low basicity guanidine mimetics resulting in potent, selective and bioavailable inhibitors of carboxypeptidase U (TAFIa). [Copyright &y& Elsevier]

RESEARCH institutes, ORGANIC chemistry, ANNIVERSARIES, SCIENTISTS, and HETEROCYCLIC chemistry

Reports that the N. D. Zelinsky Institute of Organic Chemistry (IOC), a large scientific center in Russia in the field of organic chemistry, organic catalysis, and the chemistry of natural and biologically active compounds, has turned 70 years old on February 23, 2004. Institute's concentration of highly qualified scientists on its staff; Major scientific results achieved by several institute; Studies in heterocyclic chemistry.

HYDROLYSIS, SPECTRUM analysis, MASS (Physics), and MASS spectrometry

Primary amino groups of di- or triaminoaryl compounds add a remarkably stable dioxinyl-α-oxoketene affording bis- or tris-[trioxabicyclo[3.3.1]nona-3,7-dienyl (bridged bisdioxine)] systems which can be converted into the corresponding bis- or tris-[2,4,6,8-tetraoxadamantanes] by acidic hydrolysis. Stereochemical peculiarities as well as preliminary host–guest abilities of these molecules are investigated with aid of NMR-spectroscopy, an X-ray analysis and ESI-mass spectrometry. [Copyright &y& Elsevier]

ALCOHOL, OXIDATION, DEHYDROGENASES, ENZYMES, CARBONYL reductase, and PLANT cells & tissues

To improve the efficiency and applicability of biocatalytic redox-reactions for asymmetric ketone-reduction and enantioselective alcohol-oxidation catalyzed by nicotinamide-dependent dehydrogenases/reductases, several achievements for cofactor-recycling have been made during the last two years. First, the use of hydrogenases for NADPH recycling in a two enzyme system. Second, preparative transformations with alcohol dehydrogenases coupled with NADH oxidases for NAD+/NADP+ recycling. Third, an exceptional chemo-stable alcohol dehydrogenase can efficiently use i-propanol and acetone as cosubstrates for reduction and oxidation, respectively, in a single-enzyme system. Novel carbonyl reductases and dehydrogenases derived from plant cells are particularly suited for sterically demanding substrates. [Copyright &y& Elsevier]

MONOMOLECULAR films, GOLD, SCIENTIFIC experimentation, ORGANIC chemistry, TEACHING, and LABORATORIES

The article presents a report on green materials chemistry in the teaching laboratory. In developing new educational materials for a greener organic chemistry laboratory curriculum the scholars aimed to design new laboratory exercises that emphasized the applications of organic chemistry to complement recently introduced greener synthesis laboratories. In particular, laboratories that focus on organic materials chemistry were a high priority. Authors of this article have described a convenient experiment that demonstrates self-assembled monolayer chemistry, organic thin-film patterning and the use of molecular functionality to control macroscopic properties.

HEPATITIS C virus, PROTEASE inhibitors, IMMUNOSPECIFICITY, and CHYMOTRYPSIN

The selectivity of hepatitis C virus (HCV) non-structural protein 3 (NS3) protease inhibitors was determined by evaluating their inhibitory effect on other serine proteases (human leukocyte elastase (HLE), porcine pancreatic elastase (PPE), bovine pancreatic chymotrypsin (BPC)) and a cysteine protease (cathepsin B). For these peptide inhibitors, the P1-side chain and the C-terminal group were the major determinants of selectivity. Inhibitors with electrophilic C-terminal residues were generally non-selective while compounds with non-electrophilic C-terminal residues were more selective. Furthermore, compounds with P1 aminobutyric acid residues were non-selective, while 1-aminocyclopropane-1-carboxylic acid (ACPC) and norvaline-based inhibitors were generally selective. The most potent and selective inhibitors of NS3 protease tested contained a non-electrophilic phenyl acyl sulfonamide C-terminal residue. HLE was most likely to be inhibited by the HCV protease inhibitors, in agreement with similar substrate specificities for these enzymes. The identified structure–activity relationships for selectivity are of significance for design of selective HCV NS3 protease inhibitors. [Copyright &y& Elsevier]

ORGANIC compounds, KETONES, SOLUTION (Chemistry), and PLASTICIZERS

Diaryl ketones are reduced selectively to the corresponding benzhydrols in good yield by aluminium powder in the presence of sodium hydroxide in the solvent system MeOH:H2O=2:1 whereas dialkyl ketones, α-tetralone, aryl alkyl ketones and cycloalkanones remain mostly unaffected. Interestingly, diaryl ketones remain totally unchanged by the present reagent combination in the absence of water, that is in anhydrous methanol. [Copyright &y& Elsevier]

SURFACE active agents, MONOMOLECULAR films, HYDROXYLATION, STEREOCHEMISTRY, STEREOISOMERS, and ORGANIC chemistry

Herein is described the synthesis of surfactants featuring polyhydroxylated head groups. Three head groups were prepared via consecutive stereoselective dihydroxylations of a diene. By coupling of these with lipophilic tail groups six novel surfactants have been prepared. The monolayers prepared from four of these have been investigated at the air-water interface. Significant differences were observed between monolayers consisting of enantiomerically pure surfactants contra racemates as well as between diastereomers. [ABSTRACT FROM AUTHOR]

ORGANOSULFUR compounds, SPECTRUM analysis, NITROSATION, NITROSO compounds, ZINC, and METALLURGY

Metallothioneins (MTs) release bound metals when exposed to nitric oxide. At inflammatory sites, both metallothionein and inducible nitric oxide synthase (iNOS) are induced by the same factors and the zinc released from metallothionein by NO suppresses both the induction and activity of iNOS. In a search for a possible modulatory mechanism of this coexpression of counteracting proteins, we investigated the role of the glutathione redox state in vitro because the oxidation state of thiols is involved in the metal binding in Cd-S or Zn-S clusters found in metallothioneins, and NO also binds to reduced glutathione via S-nitrosation. Using a variety of techniques, we found that NO and also ONOO–-mediated metal release from purified MTs is suppressed by reduced glutathione (GSH), but not by oxidized glutathione. Considering the millimolar concentrations of GSH present in mammalian cells, the metal release from MTs by NO should play no role in living systems. Therefore, the fact that it has been observed in vivo points to a hitherto unknown mechanism or additional compound(s) being involved in this physiologically relevant reaction and as long as this additional factor is not found experimental results on the MT–NO interaction should be treated with caution. Contrary to the peroxynitrite-induced activation of guanylyl cyclase, where GSH is needed, we found that the metal release from metallothionein by peroxynitrite is not enhanced, but also suppressed by reduced glutathione. In addition, we show that zinc, the major natural metal ligand in mammalian MTs and suppressor of iNOS, is released more readily under the influence of NO than cadmium, but in contrast to the MT isoform 1, the amount of metal released from the β-domain of MT-2 is comparable to that from the α-domain. [ABSTRACT FROM AUTHOR]

ALCOHOL, COORDINATES, LINEAR algebra, LINE geometry, MATHEMATICAL transformations, MOLYBDENUM, METALS, MAGNETIC susceptibility, and COLD (Temperature)

Two interesting neutral tetrasupporting heteropolyoxometalates: [MoVI7MoVVIV8O40(PO4)][M(phen)2(OH)]2[M(phen)2(OEt)]2·xH2O (phen=1,10-phenanthroline, EtOH=ethanol, M=Co, x=7, 1; M=Ni, x=6, 2) were hydrothermally prepared and structurally characterized. The mixed molybdenum–vanadium polyoxoanion [MoVI7MoVVIV8O40(PO4)]4- exist in both two complexes, which acts as a bridge to covalently link two pairs of transition metal complex fragments, generating neutral windmill-like trimetallic nanocluster polyoxometalates. Variable-temperature magnetic susceptibility measurements of complexes 1 and 2 reveal that antiferromagnetic exchange interaction exists in this type of trimetallic tetrasupporting heteropolyoxometalates. [Copyright &y& Elsevier]

PYRIDINE, HALOGENS, AMINO acids, and ALDEHYDES

The synthesis of 2,3,4-substituted pyridine derivatives useful as scaffolds in the development of peptidomimetics is described. The use of a variety of electrophiles in a halogen-dance reaction to produce 3-alkyl-2-fluoro-4-iodo-pyridine derivatives as ‘functionalized scaffolds’ and the possibility to differentiate between the reactivities of the two halogen handles have been explored. Coupling of amino acid derivatives in the 4-position of the pyridine was found to proceed efficiently by conversion of iodo-pyridine to a Grignard derivative, which was allowed to react with a protected amino aldehyde. Substitution of fluorine in the 2-position of the pyridine was found to be facile with alkoxide nucleophiles, whereas amines were much less reactive. [Copyright &y& Elsevier]

PROTON transfer reactions, SPECTRUM analysis, ELECTRON distribution, and EXCITED state chemistry

We studied the mechanisms of excited-state intramolecular proton transfer (ESIPT) and ground-state back proton transfer (BPT) in 3-hydroxyflavone (3HF) at cryogenic temperatures. The focus was on substituents that change the distribution of electronic density on the chromophore and their influence on these reaction rates. Shpol'skii spectroscopy was applied for comparative studies of three compounds: 3HF, 3-hydroxy-4-methoxyflavone (3HF-4OMe), and 2-furyl-3-hydroxychromone (3HC-F). By comparing the spectral bandwidths with those of deuterated analogues, we could distinguish the lifetime broadening components in the high-resolution excitation and emission spectra, from which the time constants of the ESIPT and BPT reactions were calculated. The time constants for the ESIPT reaction were 0.093 ps for 3HF, 0.21 ps for 3HF-4OMe, and slower than 0.6 ps for 3HC-F. For the same compounds, the BPT rates were 0.21, 0.47, and >2 ps, respectively. No change in bandwidth was observed over the temperature range 4-20 K, in agreement with a tunneling mechanism. Estimates for the barrier heights and proton-transfer distances are given. In addition, a systematic change in O-H bond strengths between ground and excited states was calculated from the isotope effect, observed as the shifts of the 0-0 bands in the excitation and emission spectra upon deuteration. The substantial effect of electron donating substituents on the rates of ESIPT and BPT reactions is in agreement with these changes. [ABSTRACT FROM AUTHOR]

TELLURIDES, TELLURIUM compounds, ORGANIC compounds, CARBON compounds, ORGANIC chemistry, and MICROWAVES

Primary and secondary-alkyl aryl tellurides, prepared by arenetellurolate ring-opening of epoxides/ O-allylation, were found to undergo rapid (3-10 min) grouptransfer cyclization to afford tetrahydrofuran derivatives in 60-74% yield when heated in a microwave cavity at 250° C in ethylene glycol or at 180° C in water. To go to completion, similar transformations had previously required extended photolysis in refluxing benzene containing a substantial amount of hexabutylditin. The only drawback of the microwave-assisted process was the loss in diastereoselectivity which is a consequence of the higher reaction temperature. Substitution in the Te-aryl moiety of the secondary-alkyl aryl tellurides (4-OMe, 4-H, 4-CF3) did not affect the outcome of the group-transfer reaction in ethylene glycol. However, at lower temperature, using water as a solvent, the CF3 derivative failed to react. The microwave-assisted grouptransfer cyclization was extended to benzylic but not to primary-and secondary-alkyl phenyl selenides.

ENZYME analysis, GLUTATHIONE transferase, ENZYMES, ESTERASES, CATALYSTS, HYDROLYSIS, and ENZYME kinetics

A strategy for rational enzyme design is reported and illustrated by the engineering of a protein catalyst for thiol-ester hydrolysis. Five mutants of human glutathione (GSH; γ-Glu-Cys-Gly) transferase A1-1 were designed in the search for a catalyst and to provide a set of proteins from which the reaction mechanism could be elucidated. The single mutant A216H catalyzed the hydrolysis of the S-benzoyl ester of GSH under turnover conditions with a kcat/KM of 156 M-1 x min-1, and a catalytic proficiency of >107 M-1 when compared with the first-order rate constant of the uncatalyzed reaction. The wild-type enzyme did not hydrolyze the substrate, and thus, the introduction of a single histidine residue transformed the wild-type enzyme into a turnover system for thiol-ester hydrolysis. By kinetic analysis of single, double, and triple mutants, as well as from studies of reaction products, it was established that the enzyme A216H catalyzes the hydrolysis of the thiol-ester substrate by a mechanism that includes an acyl intermediate at the side chain of Y9. Kinetic measurements and the crystal structure of the A216H GSH complex provided compelling evidence that H216 acts as a general-base catalyst. The introduction of a single His residue into human GSH transferase A1-1 created an unprecedented enzymatic function, suggesting a strategy that may be of broad applicability in the design of new enzymes. The protein catalyst has the hallmarks of a native enzyme and is expected to catalyze various hydrolytic, as well as transesterification, reactions. [ABSTRACT FROM AUTHOR]

GLYCOSYLTRANSFERASES, ENZYMES, AMINO acid sequence, PROTEIN analysis, ESCHERICHIA coli, and GENOMICS

Glycosyltransferases (GTs) are among the largest groups of enzymes found and are usually classified on the basis of sequence comparisons into many families of varying similarity (CAZy systematics). Only two different Rossman-like folds have been detected (GT-A and GT-B) within the small number of established crystal structures. A third uncharacterized fold has been indicated with transmembrane organization (GT-C). We here use a method based on multivariate data analyses (MVDAs) of property patterns in amino acid sequences and can with high accuracy recognize the correct fold in a large data set of GTs. Likewise, a retaining or inverting enzymatic mechanism for attachment of the donor sugar could be properly revealed in the GT-A and GT-B fold group sequences by such analyses. Sequence alignments could be correlated to important variables in MVDA, and the separating amino acid positions could be mapped over the active sites. These seem to be localized to similar positions in space for the α/β/α binding motifs in the GT-B fold group structures. Analogous, active-site sequence positions were found for the GT-A fold group. Multivariate property patterns could also easily group most GTs annorated in the genomes of Escherichia coli and Synechocystis to proper fold or organization group, according to benchmarking comparisons at the MetaServer. We conclude that the sequence property patterns revealed by the multivariate analyses seem more conserved than amino acid types for these GT groups, and these patterns are also conserved in the structures. Such patterns may also potentially define substrate preferences. [ABSTRACT FROM AUTHOR]

CARBORANES, COBALT, PYRIDINE, and MAGNESIUM

Abstract: The Pd-catalyzed cross-coupling reactions of B–I bond in m- and p-carboranes and cobalt bis(1,2-dicarbollide) anion with organomagnesium and organozinc compounds were studied. Carboranyl derivatives of furan, thiophene, indole, pyridine and quinoline were synthesized. 2-Pyridylethynyl and 3-quinolylethynyl derivatives of p-carborane were prepared by Pd-catalyzed cross-coupling reactions using corresponding alkynes or their magnesium derivatives. [Copyright &y& Elsevier]

METALLOTHIONEIN, NEUROSPORA crassa, FUNGI, SPECTRUM analysis, CYSTEINE proteinases, and ORGANOMETALLIC compounds

The 3D-solution structure ofNeurospora crassaCu6-metallothionein (NcMT) polypeptide backbone was determined using homonuclear, multidimensional1H-NMR spectroscopy. It represents a new metallothionein (MT) fold with a protein chain where the N-terminal half is left-handed and the C-terminal half right-handedly folded around a copper(I)-sulfur cluster. As seen with other MTs, the protein lacks definable secondary structural elements; however, the polypeptide fold is unique. The metal coordinationand the cysteine spacing defines this unique fold. NcMT is only the second MT in the copper-bound form to be structurally characterized and the first containing the -CxCxxxxxCxC- motif. This motif is found in a variety of mammalian MTs and metalloregulatory proteins. Thein vitroformation of the Cu6NcMT identical to the native Cu6NcMT was dependent upon the prior formation of the Zn3NcMT and its titration with Cu(I). The enhanced sensitivity and resolution of the 800 MHz1H-NMR spectral data permitted the 3D structure determination of the polypeptide backbone without the substitution and utilization of the NMR active spin 1/2 metals such as113Cd and109Ag. These restraints have been necessary to establish specific metal to cysteine restraints in 3D structural studies on this family of proteins when using lower field, less sensitive1H-NMR spectral data. The accuracy of the structure calculated without these constraints is, however, supported by the similarities of the 800 MHz structures of theα-domain of mouse MT1 compared to the one recalculated without metal–cysteine connectivities. [ABSTRACT FROM AUTHOR]

AROMATIC compounds, ENERGY levels (Quantum mechanics), ANNULENES, QUANTUM theory, MOLECULAR orbitals, and AROMATIC fluorine compounds

This article presents information on several aromatic compounds. In 1972, scientists used perturbational molecular orbital theory to show that annulenes which are aromatic in their singlet ground states are antiaromatic in their lowest triplet state, and vice versa for annulenes that are antiaromatic in so-called S0 state. Aromatic stabilization energies and nucleus-independent chemical shifts, supported the theory, when going from So to T1. Influence of aromaticity should further stabilize the fulvene T1 states and the fulvalene and azulene Q1 states so that these are of lower, energy than analogous states in isoelectronic molecules that are aromatic in S0 and antiaromatic in T1/Q1.

MICROREACTORS, CHEMICAL reactors, CATALYSTS, and CHEMICAL inhibitors

A T-shaped micro reactor was used for the optimisation of reaction conditions for the enantioselective silylcyanation of benzaldehyde catalysed by lanthanide–pybox complexes. Compared to a conventional batch procedure, higher conversion was observed within shorter reaction time. The micro reactor process involving Lu(III) afforded essentially the same enantioselectivity as the batch process (73 vs 76% ee), whereas the enantioselectivity was lower in the micro reactor for catalysts containing Yb(III) (53 compared to 72%). Ce(III) provided very low selectivity in both types of processes (1 and 11% ee, respectively). A study of the effect of additives showed that the enantioselectivity in the Yb catalysed reaction performed in the micro reactor could be increased to 66%, whereas only a minor improvement, to 78% ee, was observed in the reaction with Lu. [Copyright &y& Elsevier]

ENZYMES, VASOPRESSIN, KETONES, and ALCOHOLS (Chemical class)

Biocatalytic reduction of the keto-moiety of α,β-unsaturated ketones (enones) was achieved with absolute chemo- and stereo-selectivity employing whole lyophilized cells of Rhodococcus ruber DSM 44541 to furnish the corresponding allylic alcohols in e.e. up to >99%. It was shown that a stereocenter in γ-position of the ketone moiety to be reduced is too distant from the reaction center to induce any significant diastereoselectivity, thus no kinetic resolution of an racemic ketone occurred. [Copyright &y& Elsevier]

ORCHIDS, LILIES, INSECT pollinators, and INSECT behavior

Pollinators such as bees are attracted to flowers by their visual display and their scent. Although most flowers reinforce visits by providing pollen and/or nectar, there are species—notably from the orchid family—that do not but do resemble rewarding species. These mimicry relationships provide ideal opportunities for investigating the evolution of floral signals and their impact on pollinator behavior. Here, we have reanalyzed a case of specialized food mimicry between the orchid Orchis israelitica and its model, the lily Bellevalia flexuosa. Based on current knowledge of insect sensory physiology, we were able to characterize both the visual and olfactory signals of model and mimic, as well as of two phylogenetically related orchids. By using a color vision model, we mapped each species' visual signals to the perceptual space of honeybees and found an apparent shift of the mimic's visual signals towards the model. We confirm that visual mimicry is present. We analyzed the flower odors by using gas chromatography/mass spectroscopy. We related these signals to the perceptual space of the pollinators by testing the scent extracts physiologically, using in vivo brain imaging. We found no evidence of olfactory mimicry. The results indicate that evolutionary pressure acts on the visual, but not olfactory, traits of O. israelitica toward a higher similarity to its model. Apparently, odor mismatch does not prevent a bee from landing on a flower that has the expected visual display. The results therefore argue for the dominance of visual stimuli in short-distance flower choice. The orchid may still depend on long-distance olfactory attraction originating from neighboring model plants. [ABSTRACT FROM AUTHOR]

RADIOCHEMISTRY, RADIOACTIVE substances, NUCLEAR engineering, NUCLEAR science, and CHEMISTRY education

Given the mismatch between supply of and demand for nuclear scientists, education in nuclear and radiochemistry has become a serious concern. The Nuclear and Radiochemistry in Chemistry Education (NRIChEd) Curriculum Project was undertaken to reintroduce the topics normally covered in a one-semester radiochemistry course into the traditional courses of a four-year chemistry major: general chemistry, organic chemistry, quantitative and instrumental analysis, and physical chemistry. NRIChEd uses a three-pronged approach that incorporates radiochemistry topics when related topics in the basic courses are covered, presents special topics of general interest as a vehicle for teaching nuclear and radiochemistry alongside traditional chemistry, and incorporates the use of non-licensed amounts of radioactive substances in demonstrations and student laboratory experiments. This approach seeks not only to reestablish nuclear science in the chemistry curriculum, but to use it as a tool for elucidating fundamental and applied aspects of chemistry as well. Moreover, because of its relevance in many academic areas, nuclear science enriches the chemistry curriculum by encouraging interdisciplinary thinking and problem solving. [ABSTRACT FROM AUTHOR]

AMINO acids, ASYMMETRY (Chemistry), ENANTIOMERS, and CHIRALITY

Abstract: The enantiomers of the highly lipophilic α-amino acid m-carboranyl-alanine [3-(1,7-dicarba-closo-dodecaborane(12)-1-yl)-2-aminopropanoic acid], a carborane containing analogue of phenylalanine, have been synthesised via hydroxyamination of the N-acyl derivative formed from 3-(m-carboranyl)propionic acid [3-(1,7-dicarba-closo-dodeca-borane(12)-1-yl)-2-propanoic acid] and Oppolzer''s camphor sultam. The enantiomeric excess of both enantiomers of the amino acid was >98%. (S)-Configuration was assigned to the (+)-enantiomer (CH3OH, 589nm). [Copyright &y& Elsevier]

OLFACTORY receptors, STRAWBERRY-weevil, HERBIVORES, GAS chromatography, and ELECTROPHYSIOLOGY

Plants release hundreds of volatiles that are important in the interaction with herbivorous animals, but which odorants are detected by which species? In this study, single receptor neurons on the antenna of the oligophagous strawberry blossom weevil Anthonomus rubi were screened for sensitivity to naturally produced plant compounds by the use of gas chromatography linked to electrophysiological recordings from single cells. The narrow tuning of the neurons was demonstrated by responses solely to a few structurally related sesquiterpenes, aromatics or monoterpene hydrocarbons out of hundreds of plant constituents tested. We present five olfactory receptor neuron types, identified according to one primary odorant i.e. the compound to which the neurons are most sensitive. These odorants, (−)-germacrene D, (−)-β-caryophyllene, methyl salicylate, E-β-ocimene and (3E)-4,8-dimethyl-1,3,7-nonatriene, present in the intact strawberry plant, are induced in higher amounts by weevil feeding. This suggests that these compounds can provide information about the presence of conspecifics. We used protocols especially designed to allow comparison with previously investigated species. Striking similarities, but also differences, are demonstrated between receptor neuron specificity in the strawberry weevil and moths. [ABSTRACT FROM AUTHOR]

ESTERS, ORGANIC compounds, HYDROLYSIS, and ELIMINATION reactions

Abstract: An optimised method for the stereoselective hydrolysis of sec-alkylsulfate monoesters with absolute retention of configuration was developed. Under optimised conditions, clean hydrolysis of (R)-2-octyl sulfate was achieved in aqueous t-butyl methyl ether (3:97) using 0.6equiv of p-toluenesulfonic acid as catalyst and 0.33equiv of dioxane as mediator to give (R)-2-octanol as the sole product in the absence of side reactions, such as racemisation or elimination. [Copyright &y& Elsevier]

EPIDERMAL growth factor, CELLULAR control mechanisms, LEAVENING agents, and CELL differentiation

Abstract: The protein dlk, encoded by the Dlk1 gene, belongs to the Notch epidermal growth factor (EGF)-like family of receptors and ligands, which participate in cell fate decisions during development. The molecular mechanisms by which dlk regulates cell differentiation remain unknown. By using the yeast two-hybrid system, we found that dlk interacts with Notch1 in a specific manner. Moreover, by using luciferase as a reporter gene under the control of a CSL/RBP-Jk/CBF-1-dependent promoter in the dlk-negative, Notch1-positive Balb/c 14 cell line, we found that addition of synthetic dlk EGF-like peptides to the culture medium or forced expression of dlk decreases endogenous Notch activity. Furthermore, the expression of the gene Hes-1, a target for Notch1 activation, diminishes in confluent Balb/c14 cells transfected with an expression construct encoding for the extracellular EGF-like region of dlk. The expression of Dlk1 and Notch1 increases in 3T3-L1 cells maintained in a confluent state for several days, which is associated with a concomitant decrease in Hes-1 expression. On the other hand, the decrease of Dlk1 expression in 3T3-L1 cells by antisense cDNA transfection is associated with an increase in Hes-1 expression. These results suggest that dlk functionally interacts in vivo with Notch1, which may lead to the regulation of differentiation processes modulated by Notch1 activation and signaling, including adipogenesis. [Copyright &y& Elsevier]

PHYSICAL & theoretical chemistry, HYDROCARBONS, ORGANIC compounds, and SURFACE chemistry

Abstract: Complexes of bis(2-pyridylamides) with most metal ions have been described. A variety of coordination modes, with the neutral or the deprotonated amide functions binding either via the carbonyl oxygen atom or the amide nitrogen atom have been identified. The modular technique used for the preparation of the compounds permits facile access to ligands with substituted pyridine nuclei and ligands with different backbones. Moreover, symmetric as well as asymmetric compounds, with equal or different pyridine rings and with symmetric or non-symmetric amines, can conveniently be prepared. Chiral derivatives are easily obtained starting from chiral diamines. Several metal complexes have been studied as mimics of biological systems. In recent years a variety of metal complexes have also been employed in catalysis. Oxidations of alkanes and alkenes have been particularly well studied, although modest reactivity has usually been encountered. Other applications include their use as ligands in Lewis acid catalyzed processes. Recently, it was shown that complexes with molybdenum catalyze highly regio- and enantioselective allylic alkylations. [Copyright &y& Elsevier]

THYROID hormones, HORMONES, LINE geometry, and ORGANIC compounds

Abstract: An approach to thyroid hormone analogues was proposed involving sequential substitution of cationic cyclopentadienyl(1,4-dichlorobenzene)iron(II) complexes with phenoxide/thiophenoxide and hydroxide/amine, followed by decomplexation. Although the selectivity for monosubstitution with phenolates and thiophenolates was poorer than previously observed, it was often possible to control the reaction with sterically less demanding phenolates of intermediate nucleophilicity. The subsequent introduction of a polar substituent into the monosubstituted product was successful with amine nucleophiles. A modified approach, based on the reverse order of substitution was also attempted. Whereas clean monosubstitution with hydroxide/hydroxide equivalents was unsuccessful, cyclopentadienyl(N-alkyl-1-chloro-4-aminobenzene)iron(II) complexes could be prepared in fair yields and further substituted with nucleophiles such as thiophenolates. [Copyright &y& Elsevier]

BIOTECHNOLOGY, HYDROLYSIS, ESTERS, ORGANIC compounds, and EPOXY compounds

Several novel bioprocesses that have little or no counterpart in traditional methodology have recently been reported. The stereoselective and enantioselective hydrolysis of sec-alkyl sulfate esters by alkyl sulfatases proceeds with inversion of configuration and furnishes a homochiral product mixture. Haloalcohol dehalogenases were shown to accept various non-natural nucleophiles, such as azide, cyanide and nitrite for the asymmetric opening of epoxides giving rise to the corresponding azido-, cyano-, and nitro-alcohols as non-natural products. Asymmetric carbon–carbon bond formation via the acyloin- and benzoin-reaction was successfully catalyzed in water by novel lyases, such as benzoylformate decarboxylase and benzaldehyde lyase. New methods for the production of chiral nonracemic α-l-amino acids and amines were recently reported. Enantioselective stereoinversion of racemic α-aryl- and α-aryloxycarboxylic acids via epimerase-catalyzed inversion led to a single stereoisomeric product from the racemate. [Copyright &y& Elsevier]

POPLARS, GENETIC code, TRANSCRIPTION factors, NUCLEAR magnetic resonance spectroscopy, BIOTECHNOLOGY, and PLANT growth

High-resolution, magic angle spinning, proton nuclear magnetic resonance (1H HR/MAS NMR) spectroscopy and multivariate data analysis using batch processing (BP) were applied to the analysis of two different genotypes of poplar tree (Populus tremulaL. x tremuloidesMichx.) containing an antisense construct ofPttMYB76and control (wild-type). A gene encoding a MYB transcription factor, with unknown function,PttMYB76, was selected from a cambial expressed sequence tag (EST) library of poplar tree (Populus tremulaL. x tremuloidesMichx.) for metabonomic characterization. ThePttMYB76gene is believed to affect different paths in the phenyl propanoid synthetic pathway. This pathway leads to the formation of S- and G-lignin, flavonoids and sinapate esters. Milled poplar samples collected at the internodes of the tree were analysed using1H HR/MAS NMR spectroscopy. The application of multivariate BP of the NMR results revealed a growth-related gradient in the plant internode direction, as well as the discrimination between the trees with down-regulatedPttMYB76expression and wild-type populations. This paper focuses on the potential of a new analytical multivariate approach for analysing time-related plant metabonomic data. The techniques used could, with the aid of suitable model compounds, be of high relevance to the detection and understanding of the different lignification processes within the two types of poplar tree. Additionally, the findings highlight the importance of applying robust and organized multivariate data analysis approaches to facilitate the modelling and interpretation of complex biological data sets. [ABSTRACT FROM AUTHOR]

CARBONYL compounds, OXIMES, ALDEHYDES, KETONES, and HYDROLYSIS

Chemoselective regeneration of aryl alkyl ketone, a-tetralone, and cycloalkanone by hydrolysis of their oximes and semicarbazones has been accomplished using aqueous phosphoric acid without involvement of any organic cosolvent in the reaction medium, where the similar derivatives of aryl aldehyde, diaryl ketone, aliphatic acyclic aldehyde and ketone remain mostly inert. [ABSTRACT FROM AUTHOR]

QUINOLINE, HYDROXYQUINOLINE, PALLADIUM compounds, ORGANIC synthesis, CHEMICAL reactions, and CHEMICAL processes

Biologically active 4-aryl-3-alkenyl-substituted quinolin-2(1H)-ones have been synthesized in a short and concise manner employing readily available 4-hydroxyquinolin-2(1H)-ones as intermediates. Key steps in the synthesis include the derivatization of the quinolin-2(1H)-one cores using palladium-catalyzed Suzuki and Heck reactions, installing the 4-aryl and 3-alkenyl substituents. All synthetic transformations (six steps) required for the synthesis of the desired target quinolin-2(1H)-one were carried out using controlled microwave-assisted organic synthesis. [ABSTRACT FROM AUTHOR]

RACEMIZATION, ACIDS, LACTOBACILLUS, CARBOXYLIC acids, STERIC hindrance, and CHEMICAL reactions

Biocatalytic racemization of a range of aliphatic, (aryl)aliphatic, and aromatic α-hydroxycarboxylic acids was accomplished by using whole resting cells of a range of Lactobacillus spp. The mild (physiological) reaction conditions ensured an essentially ‘clean’ isomerization in the absence of side reactions, such as elimination or decomposition. Whereas straight-chain aliphatic 2-hydroxy-carboxylic acids were racemized with excellent rates (up to 85% relative to lactate), steric hindrance was observed for branched-chain analogues. Good rates were observed for aryl-alkyl derivatives, such as 3-phenyllactic acid (up to 59%) and 4-phenyl-2-hydroxybutanoic acid (up to 47%). In addition, also mandelate and its o-chloro analogue were accepted at a fair rate (45%). This biocatalytic racemization represents an important tool for the deracemization of a number of pharmaceutically important building blocks. [ABSTRACT FROM AUTHOR]

ORGANIC compounds, CARBON compounds, ORGANIC chemistry, and ANIONS

Abstract: Reactions of decaborane with various aldehydes in alkaline media were studied. The reactions with HCOH and 2-MeOC6H4CHO give the corresponding arachno-carboranes [6-R-arachno-CB9H13]− (R=H, C6H4-2-OMe), whereas the reactions with C6H5CHO, 4-BrC6H4CHO, 4-MeCONHC6H4CHO, and 2-SC4H3CHO result in the nido-carboranes [6-R-nido-CB9H11]− (R=C6H5, C6H4-4-Br, C6H4-4-NHCOMe, 2-SC4H3). Both the arachno- and nido-carboranes can be easily oxidized with elemental iodine in an alkaline aqueous solution giving the corresponding closo-derivatives [2-R-closo-2-CB9H9]−. These closo-2-isomers, under heating in solution, undergo rearrangement to more thermodynamically favorable closo-1-isomers [1-R-closo-1-CB9H9]−. The structure of (Bu4N)[1-(4-BrC6H4)-1-CB9H9] was determined using single crystal X-ray diffraction. [Copyright &y& Elsevier]

CHARGE transfer, LIGANDS, BIPYRIDINE, and ANISOTROPY

It is known that the relaxed excited state of [Ru(bpy)3]2+ is best described as a metal to ligand charge transfer (MLCT) state having one formally reduced bipyridine and two neutral. Previous reports have suggested [Malone, R. et al. J. Chem. Phys. 1991, 95, 8970] that the electron hops from ligand to ligand in the MLCT state with a time constant of about 50 ps in acetonitrile. However, we have done transient absorption anisotropy measurements indicating that already after one picosecond the molecule has no memory of which bipyridine was initially photoselected, which suggests an ultrafast interligand randomization of the MLCT state. [ABSTRACT FROM AUTHOR]

SPECTRUM analysis, RESONANCE, RAMAN spectroscopy, and RAYLEIGH scattering

Abstract: Copolymers of aniline and either 2-aminonaphthalene-4,8-disulfonic acid, or 2-aminonaphthalene-6,8-disulfonic acid, have been electrodeposited at a gold electrode, and studied by the means of in situ surface enhanced resonant Raman spectroelectrochemistry. Characteristic Raman features have been identified, and their dependencies on the electrode potential have been discussed. The nature of Raman band, observed at ca. 1630cm¿1 with the red He¿Ne laser excitation (632.8nm), is discussed. The intensity of this band grows during a positive potential shift up to a maximum, located at ca. 0.4¿0.5V vs. Ag/AgCl, and then decreases with a further potential shift up to 1.0V. Based on this, a possible alternate structure of electrogenerated copolymers has been discussed, which includes a ladder-type phenazin-like molecular unit. The ¿ortho-coupling¿ instead or parallel to the usual ¿para-coupling¿ has been suggested to proceed during electrocopolymerization of the monomers studied with aniline. [Copyright &y& Elsevier]

ALCOHOLS (Chemical class), OXIDATION, PALLADIUM, PYRIDINE, CATALYSTS, and HYDRIDES

The experimental and computational mechanistic details of the Pd(OAc)2/TEA-catalyzed aerobic alcohol oxidation system are disclosed. Measurement of various kinetic isotope effects and the activation parameters as well as rate law derivation support rate-limiting deprotonation of the palladium-coordinated alcohol. Rate-limiting deprotonation of the alcohol is contrary to the majority of related kinetic studies for Pd-catalyzed aerobic oxidation of alcohols, which propose rate-limiting β-hydride elimination. This difference in the rate-limiting step is supported by the computational model, which predicts the activation energy for deprotonation is 3 kcal/mol higher than the activation energy for β-hydride elimination. The computational features of the similar Pd(OAc)2/pyridine system were also elucidated. Details of the study illustrate that the use of TEA results in an active catalyst that has only one ligand bound to the Pd, resulting in a significant lowering of the activation energy for β-hydride elimination and, therefore, a catalyst that is active at room temperature. [ABSTRACT FROM AUTHOR]

The accuracy of theoretical approaches to describe electronic absorption spectra of N-(hydroxy)- and N-(methoxy)- derivatives of pyridine-2(1H)-thione and thiazole-2(3H)-thione are examined with the aim to identify methods that are applicable for a rational design of new photochemically active oxyl radical precursors. In addition, the mechanism of the photochemically induced methoxyl radical formation from N-(methoxy)pyridine-2(1H)-thiones and of N-(methoxy)thiazole-2(3H)-thiones is investigated by means of theoretical methods. The results of the study are applied in order to explain differences in photoreactions of N-(alkoxy)pyridine-2(1H)-thiones and the corresponding thiazole-2(3H)-thiones. [ABSTRACT FROM AUTHOR]

LIGANDS, CRYSTAL growth, CRYSTALLIZATION, and CRYSTAL grain boundaries

Anderson type heteropolymolybdates containing tris(alkoxo) ligands {MnMo6O18[(OCH2)3CR]2}3- (R = −CH2OH, −CH2CH3, and −NH2) have been successfully utilized as anions to generate the bis(ethylenedithio)tetrathiafulvalene (ET) radical cation salts:  (ET)5{MnMo6O18[(OCH2)3CCH2OH]2} (5H2O) 1, (ET)5{MnMo6O18[(OCH2)3CCH2CH3]2}·(2CH3CN) 2, and (ET)6{MnMo6O18[(OCH2)3CNH2]2}·(2CH2Cl2) 3. Compound 1 shows a metallic conducting property, but compound 2 presents semiconducting behavior although both compounds possess β  phase packing of ET molecules, while ET molecules in compound 3 exhibit &agr; phase packing. [ABSTRACT FROM AUTHOR]

PYRROLIDINE, PHOTOSENSITIZERS, ENANTIOSELECTIVE catalysis, and LIGANDS

Abstract: A catalyst-photosensitizer binuclear Mn(III)Ru(II) complex was prepared, in which the catalyst moiety of the Mn(III) unit with a chiral pyrrolidine salen ligand was covalently linked to a photosensitizer of the Ru(II) tris(bipyridyl) fragment. The electrochemical and photophysical properties of the Mn(III)Ru(II) complex were studied. [Copyright &y& Elsevier]

HYDROLYSIS, LIPASES, CHEMICAL reactions, and CHEMICAL processes

Abstract: The enzymatic kinetic resolution of 1-(3-furyl)-3-buten-1-ol was investigated via the enantioselective hydrolysis of the corresponding acetate. Pseudomonas fluorescens (Fluka) was found to give the highest enantiomeric ratios of the 11 lipases screened. At 51% conversion, the ee value (eep) for the product was found to be 89%, giving an enantiomeric ratio (E p) of 58, while the ee value (ees) for the substrate was 89%, giving an enantiomeric ratio (E p) of 38. [Copyright &y& Elsevier]

PHEROMONES, AGROMYZIDAE, PHYLLONORYCTER, INSECTS, SEX recognition (Zoology), and ENTOMOLOGY

The major sex pheromone compound of the spotted tentiform leafminer, Phyllonorycter blancardella (F.) (Lepidoptera: Gracillariidae), from Ontario, Canada, was identified as (10 E)-dodecen-1-yl acetate ( E10-12:Ac) using chemical analysis and field trapping experiments. The minor compounds (10 E)-dodecen-1-ol ( E10-12:OH) (4.6%), dodecan-1-ol (12:OH) (2.3%), and (10 Z)-dodecen-1-yl acetate ( Z10-12:Ac) 1.6% were also identified. The dienic acetate (4 E,10 E)-dodecadien-1-yl acetate ( E4, E10-12:Ac), a compound reported to be attractive to P. blancardella, was not found in the glands of this population. A two-component blend of the major and one of each the three minor compounds, in ratios similar to those found in the sex pheromone gland, did not increase the attractiveness of traps baited with synthetic pheromone. The minor compounds E10-12:OH and 12:OH were not attractive to P. blancardella when tested individually. Z10-12:Ac was attractive to P. blancardella, although traps baited with this compound captured only 2% of the moths that were captured in traps baited with the main compound. A four-component blend of the major and each of the three minor compounds (100 : 1 : 1 : 1) was not more attractive than the major compound alone. The related species Phyllonorycter mespilella was captured in traps baited with E10-12:Ac. [ABSTRACT FROM AUTHOR]

LINEAR algebra, UNIVERSAL algebra, SEDIMENTARY rocks, and ASYMMETRY (Chemistry)

Abstract: In search for new conglomerates, seven stereochemically labile complexes between MCl2 (M=Co, Cu, Ni, Zn) and bidentate ligands, the commercially available N,N,N′-trimethylethane-1,2-diamine (trimeda) and the somewhat bulkier N-isopropyl-N,N′,N′-trimethylethane-1,2-diamine (itmeda), have been synthesized and characterized using single crystal X-ray diffraction. The trimeda and itmeda ligands exhibit chirogenic nitrogen centers and may form chiral metal complexes that are candidates for total spontaneous resolution. Copper(II) chloride forms the dimeric meso complexes [{CuCl2(trimeda)}2] (1) and [{CuCl2(itmeda)}2] (2), while [CoCl2(trimeda)2] (3) and [NiCl2(trimeda)2] (4) exhibit six-coordinate but chiral (R,R)- and (S,S)-complexes. Three examples of the chiral target complex, comprising four-coordinate stereochemically labile monomers, was successfully prepared, viz. [NiCl2(itmeda)] (5), [ZnCl2(itmeda)] (6), and [CoCl2(itmeda)] (7). In all seven complexes, the λ-conformation of the five-membered trimeda-metal chelate ring corresponds to the (S)-configuration at nitrogen, and vice versa. Supramolecular interactions in 3 and 4 form hydrogen-bonded heterochiral ribbons. However, crystals of 5–7 display homochiral interactions resulting in polar phases. Weak CH–Cl interactions in 5 and 6 form homochiral layers. In 7, interactions form homochiral helices along the a-axis. [Copyright &y& Elsevier]

CHEMICAL reactions, CRYSTALS, EUCLID'S elements, and TEMPERATURE

Abstract: In search for conglomerates of stereochemically labile organometallic reagents, three new complexes between diethylzinc and diamine ligands have been synthesized and structurally characterized by single-crystal X-ray diffraction methods. Ligands include N,N,N′,N′-tetraethylethylenediamine (teeda), N-isopropyl-N,N′,N′-trimethylethylenediamine (itmeda), and (−)-sparteine (spa). Diethylzinc forms monomeric complexes, exhibiting a distorted tetrahedral coordination geometry around zinc in all three complexes, viz. [ZnEt2(teeda)] (1), [ZnEt2(itmeda)] (2), and [ZnEt2(spa)] (3). Both 1 and 2 are stereochemically labile and exhibit chiral complexes, displaying different types of conformational chirality, but they form racemic crystals. By using the chiral crystals of 3 in a nucleophilic addition to benzaldehyde in the absence of solvent at low temperature, an increase in ee from approximately 8 to 10% was obtained (compared to the same reaction in solution). It thus seems feasible, not only to retain the enantioselectivity obtained in solution, but perhaps even to increase the ee by using solventless reactions. [Copyright &y& Elsevier]

AMINO acids, ORGANIC acids, LEWIS acids, ACID-base chemistry, CATALYSIS, and ORGANIC chemistry

A highly efficient and environmentally more benign synthesis o f Fmoc-N-methyl-α-amino acids from the corresponding Fmoc-amino acid, via intermediate 5-oxazolidinones, has been developed by using Lewis acid catalysis for the reductive opening of the oxazolidinone ring. [ABSTRACT FROM AUTHOR]

LEWIS acids, ACID-base chemistry, ENANTIOSELECTIVE catalysis, ALDEHYDES, CYANIDES, and ESTERS

The article reports on dual lewis acid-lewis base activation in enantioselective cyanation of aldehydes using acetyl cyanide and cyanoformate as cyanide sources. Lewis acid activation of an electrophile and Lewis base activation of a nucleophile have been achieved in cyanations employing silyl cyanide and cyanoformic esters as well as in other types of catalytic processes. Reaction with only base as catalyst resulted in low conversion and for the chiral bases low enantioselectivity, demonstrating that dual activation is required for the reaction to proceed efficiently.

LEWIS acids, ACID-base chemistry, RADICALS, and ACIDS

Abstract: The asymmetric addition of alkyl radicals to (1R,2S,5R)-2-(1-methyl-1-phenylethyl)-5-methylcyclohexyl-2H-azirine-3-carboxylate ( 1 ) yielding the corresponding 2-alkylaziridine-2-carboxylates has been investigated. High diastereoselectivities and good yields were obtained in the addition of primary alkyl radicals to azirine 1 , while secondary radicals gave a lower dr. The influence of Lewis acids was also investigated; 10mol% of CuCl were found to increase the dr. [Copyright &y& Elsevier]

ORGANOZIRCONIUM compounds, ORGANOTRANSITION metal compounds, COMPLEX compounds, and ETHYLENE

Abstract: A series of salen-type zirconium complexes of the general formula LZrCl2 (L= N,N′-ethylenebis(salicylideneiminate), 3a; N,N′-ethylenebis(3,5-di-tert-butylsalicylideneiminate), 3b; N,N′-ethylenebis(5-methoxysalicylideneiminate), 3c; N,N′-ethylenebis(5-chlorosalicylideneiminate), 3d; N,N′-ethylenebis(5-nitrosalicylideneiminate), 3e; N,N′-o-phenylenebis(salicylideneiminate), 4a; N,N′-o-phenylenebis(3,5-di-tert-butylsalicylideneiminate), 4b; N,N′-o-phenylenebis(5-methoxysalicylideneiminate), 4c; N,N′-o-phenylenebis(5-chloro-salicylideneiminate), 4d) were prepared. The crystal structures of 6- and 7-coordinate zirconium complexes 4b and [4b ·OCMe2] were determined by X-ray crystallography, which reveals that a salen-type zirconium complex possesses a labile coordination site on the Zr center with a relatively stable framework and that the coordination and the dissociation of O-donor molecules occur readily at this site. The catalytic properties of 3(a–e) and 4(a–d) were studied for ethylene oligomerization in combination with Et2AlCl as co-catalyst. Complex 3c featuring a methoxy-substituted salen ligand displayed higher activity than its analogous precursors having chloro and nitro groups as substituents. The catalytic reactions by 3(a–e) and 4(a–d) gave C4–C10 olefins and low-carbon linear α-olefins in good selectivity. [Copyright &y& Elsevier]

PHOTOSENSITIZERS, PHOTOCHEMOTHERAPY, PORPHYRINS, CANCER cells, and ENDOPLASMIC reticulum

Abstract: Several strategies have been proposed to improve the efficiency of photosensitizers used in photodynamic therapy (PDT). In this context, the synthesis of mono- (1) and di-glucosylated (2) porphyrins, and mono-glucosylated chlorin (3) was performed. HT29 human adenocarcinoma cells were significantly more sensitive to asymmetric and less hydrophobic glucosylated photosensitizers-mediated PDT (1, 3), compared to tetraphenylporphyrin (TPP). The lowest photosensitivity observed for TPP was consistent with the lowest uptake. Moreover, the most pronounced photodynamic activity measured for 3 was in relation with the improvement of cellular uptake, the singlet oxygen quantum yield and the high extinction coefficient value at 650 nm compared to porphyrins. Cellular localization analysis showed that 1 and 3 accumulated mainly inside the endoplasmic reticulum. [Copyright &y& Elsevier]

WOOD chemistry, INDUSTRIAL chemistry, EXPERIMENTAL design, PINACEAE, and SPRUCE

Wood discs from 67 pine and 79 spruce logs were collected from a forest clearing. Three different 24-bit red-green-blue (RGB) images were acquired from the radial surface of each disc. The first image contained bark, the second image was a mixture of bark and wood surface, and the third image consisted only of wood surface. The image texture was compressed into vectors of Fourier-transformed wavelet coefficients. These were assembled in matrices and analysed by principal component analysis (PCA) and partial least-squares projections to latent structures (PLS). Classification using Fourier-transformed wavelet scales showed that the wood species could be predicted with 90% accuracy. A thorough examination of this classification showed that the predicting power of these models was mostly due to wavelet scales that represented the mean value of each colour channel. The prediction accuracy that could be obtained from coefficients representing image texture was generally low. The use of grey-level co-occurrence matrices prior to the wavelet transformation showed, however, that it is possible to classify the wood species of pine and spruce with an accuracy approaching 100%. [ABSTRACT FROM AUTHOR]