Semiochemicals Mediating Spacing Behavior of Bird Cherry-Oat Aphid, Rhopalosiphum padi Feeding on Cereals

Olfactometry using an apterous individual of Rhopalosiphum padi (L.) showed an arresting effect by volatiles from a wheat seedling and a repellent effect by volatiles from a wheat seedling infested with aphids at a high population density (ca. 9 aphids/cm²). Four compounds, 6-methyl-5-hepten-2-one, (?)- and (+)-6-methyl-5-hepten-2-ol, and 2-tridecanone, were identified by GC-MS in air entrainments from the wheat seedlings with high aphid density but not from the wheat seedlings alone. The mixture of the four compounds in the natural proportion counteracted the attractivity of the volatiles from the intact uninfested wheat seedling. The likely role of these compounds in the spacing behavior of this aphid species, when present in high densities on wheat, is discussed.     

Catalytic esterolysis of p-nitrophenyl esters by optically active polymeric oximes

An optically active polymer containing oxime groups was prepared by partial quaternization of a copolymer of 4-vinyl pyridine and (+)(S)-4-methyl-1-hexen-3-one, with phenacyl bromide and subsequent reaction with hydroxylamine hydrochloride. This polymer was used as a catalyst for the esterolysis of esters of p-nitrophenol with aliphatic and aromatic carboxylic acids characterized by different steric and hydrophobic features. The detailed evaluation of kinetic parameters permitted identification of the main factors responsible for the catalytic behaviour.     

Identification of new components from anal glands ofTapinoma simrothi pheonicium

In addition to 2-methyl-4-heptanone, 6-methyl-5-hepten-2-one, and iridodials, the anal gland exudate of the dolichoderine ant,Tapinoma simrothi, contains 4-heptanone and 4-hydroxy-4-methyl-2-pentanone. The secretion functions as an alarm pheromone.     

Highly selective asymmetric synthesis of 2-hydroxy fatty acid methyl esters through chiral oxazolidinone carboximides

Highly selective asymmetric synthesis of 2-hydroxy fatty acid methyl esters has been accomplioshed through chiral imide enolates. Five chiral oleic acid imides were prepared by reaction of oleioc acid with pivaloyl chloride followed by reaction with five different lithiated chiral oxazolidinones including (R)-(+)-4-benzyl-2-, (S)-(-)-4-benzyl-2-, (4R,5S)-(+)-4-methyl-5-phenyl-2-, (4S,5R)-(-)-4-methyl-5-phenyl-2-, and (R)-(+)-4-isopropyl-2-oxazolidinones in 88–92% yileds. The chiral imides were reacted with NaN(Me₃Si)₂ at −78°C to give enolates, which subsequently reacted with 2-(phenylsulfonyl)-3-phenyloxaziridine to give hydroxylated products in 78–83% yields. Methanolysis of the hydroxylated products with magnesium methoxide gave methyl 2-hydroxyoleate. Enantiomeric excesses (ee) of the products were determined to be very high (98–99% ee) by ¹H nuclear magnetic resonance study after esterification of the hydroxy group with (S)-(+)-O-acetylmandelic acid. Enantioselective hydroxylation of other fatty acids including elaidic, petroselinic, vaccenic, and linoleic was evaluated under the similar conditions using (4R, 5S)-(+)-4-methyl-5-phenyl-2-oxazolidinone as a chiral auxiliary to give 98% ee values for all cases.     

Headspace Analysis in Chemical Ecology: Effects of Different Sampling Methods on Ratios of Volatile Compounds Present in Headspace Samples

The effects that different headspace sampling methods have on the analysis of the ratios of compounds present in the headspace of a synthetic mixture and a biological sample were evaluated using the following methods: solid-phase microextraction (SPME), a syringe, and the porous polymers Porapak Q, Tenax TA, and Hayesep Q (thermal and solvent desorption). The performance of each method was only evaluated for a certain sampling period and under given experimental conditions. The test mixture comprised pentan-3-ol, 4-penten-1-ol, (E)-2-hexenal, hexan-1-ol, heptanal, (1S,5S)-(–)--pinene, 6-methyl-5-hepten-2-one, hexyl acetate, (R)-(+)-limonene, and undecane. SPME gave significantly different ratios of pentan-3-ol, 4-penten-l-ol, hexan-1-ol, heptanal, (1S,5S)-(–)--pinene, 6-methyl-5-hepten-2-one, hexyl acetate, limonene, and undecane compared with the other methods. No significant differences were observed between the syringe and the porous polymers or between the three different porous polymers used. The method of release of the trapped analytes from the polymers, thermal or solvent desorption, did not affect the ratios of compounds. The effects that different sampling methods have on the ratios of compounds present in the headspace of a biological sample, ripe banana, were evaluated. The headspace was sampled using SPME and the porous polymers Porapak Q and Tenax TA (thermal desorption). The following compounds were identified in the headspace of ripe bananas: 2-methylbutyl acetate, pentyl acetate, 2-methylbutyl propanoate, butyl butanoate, and pentyl butanoate. SPME gave significantly different ratios of 2-methylbutyl acetate, pentyl acetate, butyl butanoate, and pentyl butanoate when compared to Porapak Q and Tenax TA. No significant differences on the ratios of compounds present in the headspace of ripe banana were observed when the two polymers were compared. The use of different sampling methods in headspace analysis of biological samples is dicussed.     

Enantiomer Separation of a Novel Ca-Sensitizing Drug by simulated moving bed (SMB) – chromatography

The continuous chromatographic seperation by maens of Simulated Moving Bed (SMB) – Chromatography was used to produce the enantiomers of 5-(1,2,3,4-tetrahydroquinoline-6-yl)-6-methyl-3,6-dihydro-1,3,4-thiadiazin-2-one (EMD 53986), a precursor of the novel Ca-sensitizing drug 5-(1-(3,4-dimethoxybenzoyl)-1,2,3,4-tetrahydroquinoline-6-yl)-6-methyl-3,6-dihydro-1,3,4-thiadiazin-2-one (EMD 57033). The (+)-enantiomer EMD 57033 is a potent Ca-sensitizing drug, whereas its (−)-antipode is a pure phosphodiesterase-(PDE)-inhibitor without any Ca-sensitizing activity. A chromatographic seperation of the enantiomers was developed on two different chiral stationary phases: a cellulose-tri-(p-methyl-benzoate) phase and a polymeric silica based stationary phases. A process simulation software was used to calculate the starting parameters for the SMB-system. For both stationary phases the SBM-parameters were optimized and pure enantiomers were produced using a system with 8 columns of 26 mm internal diameter. A comparison of the purities and throughput achieved with both stationary phases is given.     

Exocrine glands ofPolyrhachis simplex: Chemistry and function

The mandibular glands of the Israeli weaver ant,Polyrhachis simplex, contain a mixture of 4-heptanone, 6-methyl-5-hepten-2-one and 6-methyl-5-hepten-2-ol;its Dufour's gland secretion consists mainly ofn-tridecane. The significance of these glandular secretions in the biology of the weaver ant is discussed.     

Chemistry and functions of exocrine secretions of the antsTapinoma melanocephalum and T. erraticum

Volatile constituents produced by ant workers belonging to the speciesTapinoma melanocephalum andT. erraticum have been analyzed by gas chromatography-mass spectrometry. The pygidial (=anal) gland secretion ofT. melanocephalum is fortified with 6-methyl-5-hepten-2-one and actinidine (the mass spectrum of which is corrected in this paper). An unidentified compound was detected in cephalic extracts. The pygidial gland secretion ofT. erraticum was also dominated by 6-methyl-5-hepten-2-one, in addition to two isomers of iridodial, and iridomyrmecin. The sternal glands contained iridodial and C₁₅-C₂₀ hydrocarbons. Workers ofT. melanocephalum effectively utilize their pygidial gland secretions as an alarm-defense system during aggressive encounters with workers ofSolenopsis geminata. 6-Methyl-5-hepten-2-one is active as a releaser of alarm behavior, and actinidine is repellent to workers ofT. melanocephalum. Cephalic extracts possessed attractant and arrestant properties for workers of this species.     

Tailor made liquid crystalline networks exhibiting a chiral smectic C (S C * ) mesophase via living cationic copolymerization

Summary Living cationic copolymerization of (2S, 3S)-(+)-2-chloro-3-methylpentyl 4-(8-vinyloxyoctyloxy)biphenyl-4-carboxylate (15-8) with 2-vinyloxyethyloxy methacrylate (16-2) leads to reactive copolymers poly[(15-8)-co-(16-2)]X/Y (where X/Y is the mol ratio between the two monomers in the copolymer) containing methacryloyl side groups. The thermally crosslinked copolymers with X/Y=5/5 to 9/1 display an enantiotropic chiral smectic C (S _C ^* ) mesophase.This paper is part 28 in the series: Molecular engineering of liquid-crystalline polymers by living polymerization. Part 27: V. Percec, Q. Zheng: Polym. Bull., previous paper in the issue     

Semiochemicals from bark beetles: New results,remarks, and reflections

A brief survey is given about recent results in the identification of semiochemicals in bark beetles: Males ofIps sexdentatus (Boern.), stressed by the attack on resinous trees produce large amounts of 3(S)-1-methyl-5-(1-hydroxyl-1-methylethyl)-cyclohexa-1,3-diene. The compound appears to be derived from ³-carene and acts as a repellent. Males ofIps typographus (L.), stressed through the attack on unsuitable host material release 3-methyl-7-methylene-1,3(E), 8-nonatriene, which seems to act as a repellent. The odor bouquet of three species ofPityogenes is described. The occurrence of (+)-grandisol and other compounds related to weevil pheromones points to a close relation between Scolytidae and Curculionidae. Females ofDendroctonus simplex (Le Conte) use (–)-frontalin as the main pheromone. 6-Methyl-6-hepten-2-one, a minor component among the volatile compounds released by the females, is regarded as a possible precursor of frontalin. Similarly, (2R,5S)-2(1-hydroxyl-1-methylethyl)-5-methyltetrahydrofuran, pityol, a pheromone ofPityophthorus spp., is regarded to at least share a common biogenetic precursor with 6-methyl-5-hepten-2-ol, sulcatol. A new bicylic acetal, 2-ethyl-1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane, is described as an aggregation pheromone of the beech bark beetle,Taphrorychus bicolor (Herbst). Structural relationships between bark beetle pheromones and plant volatiles are discussed.     

Novel chemistry of abdominal defensive glands of nymphalid butterfly Agraulis vanillae

Abdominal defensive glands of both sexes of the Gulf fritillary butterfly, Agraulis vanillae (Linnaeus) (Nymphalidae:Heliconiinae)emit a pronounced odor when disturbed. We have identified 6-methyl-5-hepten-2-one; oleic, palmitic, and stearic esters of the corresponding alcohol 6-methyl-5-hepten-2-ol; hexadecyl acetate; 1,16-hexadecanediol diacetate; and 1,15-hexadecanediol diacetate in the glandular exudate. Since we have determined that free-flying birds or birds in a butterfly conservatory discriminate against A. vanillaeas prey, we suggest that the constituents in the glands may play a defensive role against potential avian predators.     

Mandibular Gland Secretion in Different Castes of the Leaf-Cutter Ant Atta laevigata

Gas chromatography analyses and behavioral assays showed that Atta laevigata, a highly polymorphic ant species, has a mandibular gland secretion that varies with castes. All castes contain 4-methyl-3-heptanone as the main component and its concentration is proportional to head size. Small workers and soldiers, but not medium size workers, also contain 4-methyl-3-heptanol. Queens show variations in their chemical composition after mating, as virgin males contain a secretion dominated by 4-methyl-3-heptanol, and, in a lesser proportion, 4-methyl-3-heptanone. In mated males these proportions are inverted. The compounds 4-methyl-6-hepten-3-one, 4-methyl-4-hepten-3-one, 6-methyl-tetradecene, and 2,6-dimethyl-2-dodecene are found only in queens. The behavioral response elicited by the secretion is mainly alarm, which is elicited more strongly by glands of larger workers. The results suggest that chemical castes, behavioral castes, and morphological castes overlap in this species.     

Field response of the dutch elm disease vectors,Scolytus multistriatus (Marsham) andS. scolytus (F.) (Coleoptera: Scolytidae) to 4-methyl-3-heptanol baits containing α-, β-,δ-, or δ-multistriatin

The field responses of English populations of the Dutch elm disease vectors,Scolytus multistriatus andS. scolytus to baits containing 4-methyl-3-heptanol, a host synergist [(?)-α-cubebene or (?)-limonene] and (±)-α-, (+)-β-, (?)-β-, (±)-γ-, or (±)-δ-multistriatin were examined. (±)-α-Multistriatin, released at 5–10 μg/day, enhanced the response ofS. multistriatus to baits containing 4-methyl-3-heptanol and either of the host synergists but had no effect on the capture ofS. scolytus. The release of larger amounts (57 or 365 μg/day) of (±)-α-multistriatin interrupted the response of both species to the 4-methyl-3-heptanol baits. It appears that α-multistriatin has multiple functions as a behavior-modifying substance for the two beetles. The (+)-β-, (?)-β-, (±)-γ-, and (±)-δ-multistriatins were inactive when released at 5–10 μg/day. The results of these field experiments suggest that one bait can be formulated to capture both species.     

Interaction between poly(vinyl pyridine) and poly(2,6-dimethyl-1,4-phenylene oxide): A copolymer blend miscibility study

The phase behavior of blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) with random copolymers of styrene and 2-vinyl pyridine, Poly(S-co-2VP), as well as with random copolymers of styrene and 4-vinyl pyridine, Poly(S-co-4VP), has been investigated in order to estimate the values of the Flory-Huggins parameters χPPO,2VP and χPPO,4VP between PPO and 2-vinyl pyridine, resp. 4-vinyl pyridine. Using previously estimated values for the Flory-Huggins parameters 0.09<χS,2VP<0.11 and 0.30<χS,4VP<0.35, together with the literature value of χS,PPO=−0.043, the phase behavior observed as a function of the copolymer composition results in 0.11≤χPPO,2VP≤0.12 and 0.46≤χPPO,4VP≤0.48. Insight in the interaction between PPO and poly(vinyl pyridine) is of considerable interest for several nanotechnology developments, since PPO is used to improve the mechanical properties of e.g. PS-block-P4VP nanorods.     

Formation of formaldehyde and malonaldehyde by photooxidation of squalene

Formaldehyde and malonaldehyde were identified upon exposure of squalene to ultraviolet (UV) irradiation at 300 nm. Formaldehyde was derivatized by reaction with cysteamine to form thiazolidine; malonaldehyde was derivatized by reaction withN-methylhdyrazine to produceN-methylpyrazole. The derivatives were subsequently analyzed with a gas chromatography equipped with a fused silica capillary column and a nitrogen/phosphorus detector. The levels of formaldehyde and malonaldehyde produced increased with irradiation time. The amount of formaldehyde produced reached a maximum of 3.40 nmol/mg squalene after 7 hr irradiation; the maximum amount of malonaldehyde generated, 0.92 nmol/mg, was found after 5 hr of irradiation. Prior to this study, formaldehyde had not been reported as a photoproduct of squalene. Acetaldehyde and acetone were also detected in the irradiated squalen,, which may be formedvia a 6-methyl-5-hepten-2-one intermediate. 6-Methyl-5-hepten-2-one can also undergo breakdown to form malonaldehyde.     

二聚脱氢芳樟醇碱分解反应制备6-甲基-5-庚烯-2-酮

以脱氢芳樟醇水蒸气蒸馏残液为原料,反应压力为常压,反应温度为103~142℃,残液中的二聚脱氢芳樟醇和脱氢芳樟醇在浓KOH或NaOH水溶液催化作用下进行分解反应,生成6-甲基-5-庚烯-2-酮和乙炔。考察了碱浓度、温度、油碱质量比对残液分解反应的影响,提出了反应历程。以w(KOH)=50%的水溶液为催化剂,反应温度124~127℃,残液与碱液质量比15∶1,残液中的二聚脱氢芳樟醇、脱氢芳樟醇质量分数分别为60.1%、33.6%,搅拌速度100~200 r/min,反应5 h,脱氢芳樟醇水蒸气蒸馏残液分解生成6-甲基-5-庚烯-2-酮的反应收率为94.3%,反应液中的6-甲基-5-庚烯-2-酮质量分数为92.1%。     

The effect of polystyrene-block-poly(4-vinylpyridine) prepared by a RAFT method in the dispersion polymerization of MMA

The dispersion polymerization of methyl methacrylate (MMA) has been carried out using polystyrene-block-poly(4-vinylpyridine) copolymer [P(S-b-4VP)], which was prepared by a reversible addition-fragmentation chain transfer (RAFT) method, as a steric stabilizer in an alcohol media. The stable polymer particles were obtained when the block copolymer concentrations increased from 1 to 10 wt% relative to the monomer and the average particle sizes decreased from 5.3 to 3.4 μm with the increasing concentration of the block copolymer. In particular, the incorporation of 2 wt% polystyrene-block-poly(4-vinylpyridine) produced 4.3 μm of monodisperse PMMA particles with 2.14% of C_v. Thus, the P(S-b-4VP) block copolymer prepared by the RAFT method is working not only as a steric stabilizer, but also in providing monodisperse micron-sized PMMA particles.     

Solvent extraction and separation of light lanthanoids with mixtures of two chelating extractants: Benzene vs. ionic liquid

Solvent extraction of lanthanoids (La-Gd) with mixtures of a chelating extractants (HL), either 4-(4-fluorobenzoyl)-3-methyl-1-phenyl-pyrazol-5-one(HPMFBP) or 3-methyl-4-(4-methylbenzoyl)-1-phenyl-pyrazol-5-one (HPMMBP) and 1-(2-thienyl)-4,4,4-trifluoro-1,3-butanedione (thenoyltrifluoroacetone, HTTA) has been studied in benzene. The composition of the extracted species was established as LnL₃·HL with the two para-substituted 4-aroyl-3-methyl-1-phenyl-pyrazol-5-ones. It was found that, in the presence of a thenoyltrifluoroacetone, the lanthanoids were extracted as LnL₃·HTTA. The separation factors between adjacent metals were evaluated. The extraction of Eu(III) ions was investigated by use of ionic liquid, 1-methyl-1,3-butylimidazolium-bis(trifluoromethanesulfonyl)imide instead of benzene in order to make comparison without looking at the mechanism aspects.     

Effect of the Chiral Center Position of an Optically Active Terminal Group on the Induction of Optical Activity in Polysilanes

Summary Polysilanes with an optically active alkoxy group, i.e., (S)-(+)-2-butoxy, (R)-(-)-2-butoxy, (S)-(-)-2-methyl-1-butoxy, and (S)-(+)-3,7-dimethyl-1-octoxy, at the terminal positions, the chiral carbon centers of which were located at the α, β, and γ positions relative to the oxygen, respectively, were prepared, and the effect of the position of chiral center of the terminal optically active group on the induction of optical activity in polysilanes was investigated. The circular dichroism (CD) spectra of these polymers showed positive Cotton signals around 340 nm at temperatures below -20 °C, but the intensities were small, indicating that the optically active groups at the terminal positions have some ability, albeit small, to induce optical activity to the polysilanes. Further, the optically active (S)-(+)-2-butoxy and (R)-(-)-2-butoxy groups did not control the helical sense direction of the polymers, despite the different chiral stimuli from the 2-butoxy groups introduced to the terminal positions. To control the helical structure of polysilanes by the use of optically active terminal groups, appropriate optically active groups are required.     

Dynamic study of polystyrene-block-poly(4-vinylpyridine) copolymer in bulk and confined in cylindrical nanopores

AAO template is highly recommended to nanostructure polymers and to study polymer properties under confinement. The dynamic properties of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) under confinement using broadband dielectric spectroscopy are investigated in this work and the results compared to those of the bulk. Anodized aluminum oxide (AAO) membranes, having pore diameters from tens to hundreds of nanometers in size, were used to confine PS-b-P4VP. Moreover, the influence of gold nanoparticles (AuNPs) in the copolymer matrix was also studied. The morphology and structure of the bulk copolymer and the copolymer confined in the AAO templates were characterized by transmission electron microscopy, scanning electron microscopy and Small Angle X-Ray Scattering. For PS-b-P4VP in bulk, dielectric relaxation techniques allowed studying selectively the P4VP segmental dynamics within the diblock. At high temperature this copolymer presents a dominant peak (MWS relaxation), most likely originated by the relatively high conductivity combined with the presence of interfaces emerging in the nanostructured samples. Moreover, a pronounced β-relaxation is observed for the copolymer compared with that of pure P4VP. This is likely due to a non-negligible contribution from the α-relaxation of the PS component. The γ-relaxation is markedly different in the copolymer, which is evidenced by a distinct temperature dependence of the resulting relaxation times. When the copolymer is embedded in alumina nanopores with small pore diameters (25 and 35 nm) there are significant changes, where the tendency is going to a faster dynamics when the pore diameter decreases more likely related to the relevance of surface effects. The presence of the AuNPs in the system enhances this effect. These results are in agreement with segregated structures found in the block copolymer by TEM and SAXS.