Syntheses of (Z,E)-5,7-dodecadienol and (E,Z)-10,12-hexadecadienol,lepidoptera pheromone components,via zinc reduction of enyne precursors. test of pheromone efficacy against the Siberian moth

Efficient syntheses of (Z,E)-5,7-dodecadienol, a pheromone component of the Siberian moth, Dendrolimus superans sibiricus, and (E,Z)-10,12-hexadecadienol, a pheromone component of various Lepidoptera pheromones, were accomplished by cis reduction of the corresponding enynols with activated zinc. The most energetic reagent was zinc galvanized with copper and silver (Zn/Cu/Ag) that achieved rapid and high-yield reduction in methanol-water. The stereoselectivity of semi-hydrogenation was > or =98%. A process whereby zinc dust was continuously activated throughout the reduction with an acid was also satisfactory (95-98% cis). Field evaluation of the 1:1 mixture of (Z,E)-5,7-dodecadienol and (Z,E)-5,7-dodecadienal with the Siberian moth in Russia showed that the rubber septa pretreated with compound and stored at -80 degrees C were as effective as freshly treated septa. Moth responses to septa aged in open air indicated that lure effectiveness declined significantly after 2 weeks of aging. Thus, if rubber septa are used as pheromone dispensers in Siberian moth traps monitoring, they should be replaced biweekly with fresh septa for optimal trap effectiveness.     

Sex pheromone of browntail moth, Euproctis chrysorrhea (L.): synthesis and field deployment

The browntail moth, Euproctis chrysorrhea (L.), is native to Eurasia, where periodic outbreaks result in defoliation of forest, shade, and ornamental trees. In addition to the damage caused by defoliation, human contact with larval urticating hairs often results in severe dermatitis. Hence, tools for monitoring and controlling the moth populations are desirable. The female-produced sex pheromone of the browntail moth was identified previously, but the synthesis had not been published. This paper reports the synthesis of the pheromone of the browntail moth, (7Z,13Z,16Z,19Z)-docosatetraenyl isobutyrate, using in a key step a Wittig olefination of (6Z)-13-(tetrahydo-2H-pyran-2-yloxy)tridecenal. Field trapping studies were conducted with rubber septa and string formulations of the pheromone and included dose-response, pheromone purity, and dispenser-aging trials. It was found that traps baited with 250 microg of pheromone of 91-94% isomeric purity (main impurity presumably being the 13E isomer) on rubber septa are suitable for monitoring moth populations during the entire flight season.     

Behavioral responses of the diamondback moth, Plutella xylostella, to green leaf volatiles of Brassica oleracea subsp. capitata

Green leaf volatiles (GLVs) from Brassica oleracea subsp. capitata L. have been identified as 1-hexanol, (Z)-3-hexen-1-ol, 1-hexen-3-ol, hexanal, (E)-2-hexenal, hexyl acetate, and (Z)-3-hexenyl acetate, by their mass spectra and retention times in comparison with authentic samples. No isothiocyanates were found in the extract. The activity of these chemicals has been determined on mated and unmated males and females of the diamondback moth (DBM) Plutella xylostella in the laboratory (wind tunnel) and in the field. On unmated males, mixtures of (Z)-3-hexenyl acetate, (E)-2-hexenal, and (Z)-3-hexen-1-ol with the pheromone induced attractant/arresting behavior in 80-100% of the males tested, significantly higher than the effect induced by the pheromone alone. On mated males and unmated females the effect of the GLVs alone or in combination with the pheromone was poor, while on mated females these compounds elicited upwind flight and arresting behavior in 40-60% of the females assayed. There was no synergism when these chemicals were mixed with the pheromone. In the field, (Z)-3-hexenyl acetate, the most active GLV in laboratory tests, when mixed with the pheromone in 1:1 ratio, enhanced 6-7-fold the number of females and 20-30% the number of males caught by traps over those baited with the pheromone alone. Our results indicate that the enhancement of the attraction of both males and females of the DBM to traps baited with pheromone blended with the relatively inexpensive and environmentally safe (Z)-3-hexenyl acetate may be important for future control strategies of the pest.     

Specificity of codling moth (Lepidoptera: Tortricidae) for the host plant kairomone, ethyl (2E,4Z)-2,4-decadienoate: field bioassays with pome fruit volatiles, analogue, and isomeric compounds

Codling moth, Cydia pomonella (L.), is a severe pest of apples, pears, and walnuts worldwide, and new approaches for precise monitoring and management would be beneficial. Ninety-two pome fruit volatiles were formulated in 23 distinct blends, of which a single 4-component blend of 10-carbon esters showed the only significant attraction of moths in field bioassays conducted in both walnut and apple orchards. A single constituent of this blend, ethyl (2E,4Z)-2,4-decadienoate--the "pear ester", was the major contributing attractant. The pear ester attracted both male and female moths in combined numbers that were comparable to the attractiveness of conspecific sex pheromone. Structure-activity tests were conducted in a series of orchard trials to determine the specificity of attraction of codling moths to the pear ester kairomone. No analogue 10-carbon alcohols, aldehydes, acetates, or other esters elicited significant moth capture responses. Tests with various analogue esters with alcohol chain length moiety substitutions of the (2E,4Z)-2,4-decadienoic acid elicited differential capture responses, with the ethyl exceeding the propyl, methyl, butyl, and hexyl analogues. The (E,Z) geometric isomers of this series of (2E,4Z)-2,4-decadienoic acid esters far exceeded the attractiveness of the (E,E) isomers. The pear ester is a potent attractant of both males and females, and codling moths are highly discriminating and specific in their structure-activity-based attraction to this pear-derived kairomone. These specificity attributes should allow this host plant kairomone to contribute to new abilities for female monitoring and the potential of development of novel and highly selective control practices that should decrease the current dependence on the use of broad-spectrum insecticides.     

Facile and efficient syntheses of (3Z,6Z,9Z)-3,6,9-nonadecatriene and homologues: pheromone and attractant components of lepidoptera

Facile and efficient chemical syntheses of (3Z,6Z,9Z)-3,6,9-nonadecatriene and homologues from commercially available alpha-linolenic acid [(9Z,12Z,15Z)-9,12,15-octadecatrienoic acid] are reported. These straight-chain homoconjugated trienes are common sex pheromone and attractant components for many lepidopterous insect pests. The metal-catalyzed cross-coupling reactions between (9Z,12Z,15Z)-9,12,15-octadecatrienyl triflate and the appropriate Grignard reagents proceed very rapidly under notable mild conditions using Li(2)CuCl(4) as catalyst in diethyl ether, and the resulting (3Z,6Z,9Z)-3,6,9-trienes with retention of geometrical configuration were in >92% isolated yield.     

Sex pheromone of the oak processionary moth Thaumetopoea processionea. Identification and biological activity

The sex pheromone of the oak processionary moth Thaumetopoea processionea has been characterized from female gland extracts as a mixture of (Z,Z)-11,13-hexadecadienyl acetate (1), (E,Z)-11,13-hexadecadienyl acetate (3) and (Z,Z)-11,13-hexadecadienol (2) in 88:7:5 ratio. The amount of the major compound 1 was 20-30 ng/gland. No trace of (Z,Z)-11,13-hexadecadienal was found in the extract, and therefore, T. processionea appears to be the only "summer" processionary moth lacking this compound as a pheromone compound. The alcohol 2 had also been previously found but is electrophysiologically inactive, and in wind tunnel assays it lowers the number of contacts with the source when mixed with the major compound 1. The major component 1 elicited males to display the complete behavioral sequence, but the amount of chemical needed was unexpectedly high in comparison to the activity displayed by virgin females and gland extracts. (E,E)-11,13-hexadecadienyl acetate (5) inhibits the attractant activity of the major component 1 when mixed with 1 in 1:10 and 1:1 ratios. The main constituent 1 is active in the field, but its tendency to isomerize into the corresponding E,E isomer (5) must be considered if effective formulations are to be prepared.     

Analysis of a model reaction system containing cysteine and (E)-2-methyl-2-butenal, (E)-2-hexenal, or mesityl oxide

Cysteine conjugates, resulting from the addition of cysteine to alpha,beta-unsaturated carbonyl compounds, are important precursors of odorant sulfur compounds in food flavors. The aim of this work was to better understand this chemistry in the light of the unexpected double addition of cysteine to two unsaturated aldehydes. These reactions were studied as a function of pH. When (E)-2-methyl-2-butenal (tiglic aldehyde, 4) was treated with cysteine in water at pH 8, the major product formed was the new compound (4R)-2-(2-[[(2R)-2-amino-2-carboxyethyl]thio]methylpropyl)-1,3-thiazolidine-4-carboxylic acid (6). Under acidic conditions (pH 1), we also observed a double addition, but the second cysteine was linked by a vinylic sulfide bond to form the previously unreported major product, (2R,2'R,E)-S,S'-(2,3-dimethyl-1-propene-1,3-diyl)bis-cysteine (7). When (E)-2-hexenal (12) was treated with cysteine under acidic conditions, the major product was the novel (4R,2' 'R)-2-[2'-(2' '-amino-2' '-carboxyethylthio)pentyl]-1,3-thiazolidine-4-carboxylic acid (13), and the formation of an vinylic sulfide compound analogous to 7 was not observed. Reduction of the acidic crude reaction mixture with NaBH(4) afforded 13 and the cysteine derivative (R)-S-[1-(2-hydroxyethyl)butyl]cysteine (14) in 14% yield. Treating (E)-2-hexenal with cysteine at pH 8 followed by NaBH(4) reduction yielded the new product (3R)-7-propylhexahydro-1,4-thiazepine-3-carboxylic acid (15). Addition of cysteine to mesityl oxide (16), at pH 8, followed by reduction with NaBH(4) furnished (R)-S-(3-hydroxy-1,1-dimethylbutyl)cysteine (3) and the new compound (3R)-hexahydro-5,7,7-trimethyl-1,4-thiazepine-3-carboxylic acid (18).     

Concise preparation of the (3E,5Z)-alkadienyl system. New approach to the synthesis of principal insect sex pheromone constituents

A new rapid and low-cost preparation of the (3E,5Z)-3,5-alkadienyl system, encountered in several insect pheromone constituents, was developed. Knoevenagel condensation of (E)-2-alkenals with ethyl hydrogen malonate in dimethyl sulfoxide, in the presence of a catalytic amount of piperidinium acetate, led to a mixture of geometrical isomers of ethyl 3,5-alkadienoates and ethyl 2,4-alkadienoates, from which the (3E,5Z)-3,5-alkadienoate was conveniently separated, by the use of urea inclusion complex formation. The importance of this procedure has been illustrated by the preparation of the (3E,5Z)-3,5-tetradecadienoic acid (megatomoic acid) 1, the (3E,5Z)-3,5-dodecadienyl acetate 2, and the (3E,5Z)-3,5-tetradecadienyl acetate 3. These compounds are the main components of insect sex pheromones and constitute synthetic targets of considerable interest for the semiochemical community.     

Reduction of Carpophilus freemani dobson (Coleoptera: nitidulidae) aggregation pheromone response by synthetic analogues.

Analogues of (2E,4E,6E)-5-ethyl-3-methyl-2,4,6-nonatriene, the major component of the aggregation pheromone of Carpophilus freemani Dobson (Coleoptera: Nitidulidae), were synthesized and the potency of these compounds in suppressing the response of C. freemani to its pheromone in a wind tunnel bioassay was determined. The most potent compounds reduced behavioral response to pheromone 83-96% when the inhibitors were present in 10-fold excess. These compounds are (1Z, 3E,5E)-1-methoxy-3-ethyl-5-methyl-1,3,5-heptatriene, (1E,3E, 5E)-1-cyclopropyl-3-ethyl-5-methyl-1,3,5-heptatriene, and (1Z,3E, 5E)-1-cyclopropyl-3-ethyl-5-methyl-1,3,5-heptatriene. In the presence of fermenting bread dough (a pheromone synergist), the most potent inhibitory compound, (1Z,3E, 5E)-1-cyclopropyl-3-ethyl-5-methyl-1,3,5-heptatriene, was less effective in reducing mean landings (69% vs 99%) than when dough was absent. This inhibitory compound causes a reduction of response to pheromone but does not cause a reduction of response to fermenting food-type volatiles such as fermenting bread dough. Analogues of pheromones that strongly reduce response to pheromones by insects might be useful as biochemical probes to study the pharmacophoric (three-dimensional structure) requirements for pheromone perception.     

Degradation studies on benzoxazinoids. Soil degradation dynamics of (2R)-2-O-beta-D-glucopyranosyl-4-hydroxy-(2H)- 1,4-benzoxazin-3(4H)-one (DIBOA-Glc) and its degradation products, phytotoxic allelochemicals from Gramineae

Wheat (Triticum aestivum L.) has been found to possess allelopathic potential and studies have been conduced to apply wheat allelopathy for biological weed control. 2,4-Dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one (DIBOA) is a common product found in wheat, corn, and rye exudates and it can be released to the environment by that way. In this report, the stability of DIBOA is studied in two soils from crop lands of wheat cv. Astron and cv. Ritmo. These varieties were selected by their concentrations of DIBOA and 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (DIMBOA) from aerial parts and by the bioactivities of their aqueous extracts in the growth of wheat coleoptile sections. The degradation rate of DIBOA in these soils was measured in laboratory tests during 90 h by high-pressure liquid chromatography methods. These analyses demonstrate that DIBOA was transformed primarily into 2-benzoxazolinone (BOA). This transformation was similar in both soil types with an average half-life of 43 h. The degradation studies for BOA show its biotransformation to 2-aminophenoxazin-3-one (APO) with a half-life of 2.5 days. Therefore, BOA is an intermediate product in the biotransformation from DIBOA to APO in these wheat crop soils and is consistent with previous findings. APO was not degraded after three months in soil, suggesting that its degradation rate in soil is very slow.     

Metabolism of 7-fluoro-6-(3,4,5,6-tetrahydrophthalimido)-4- (2-propynyl)-2H-1,4-benzoxazin-3(4H)-one (S-53482, flumioxazin) in the rat: II. Identification of reduced metabolites

On single oral administration of (14)C-S-53482 [7-fluoro-6-(3,4,5, 6-tetrahydrophthalimido)-4-(2-propynyl)-2H-1,4-benzoxazin-3( 4H)-one, Flumioxazin] labeled at the 1- and 2-positions of tetrahydrophthaloyl group to rats at 1 (low dose) or 100 (high dose) mg/kg, the radiocarbon was almost completely eliminated within 7 days after administration in both groups with generally very low residual (14)C tissue levels. The predominant excretion route was via the feces. The major fecal and urinary metabolites involved reduction or sulfonic acid addition reactions at the 1,2-double bond of the 3,4,5,6-tetrahydrophthalimide moiety and hydroxylation of the cyclohexene or cyclohexane ring. One urinary and four fecal metabolites were identified using chromatographic techniques and spectroanalyses (NMR and MS). Three of five identified metabolites were unique forms, reduced at the 1,2-double bond of the 3,4,5, 6-tetrahydrophthalimide moiety. On the basis of the metabolites identified in this study, the metabolic pathways of S-53482 in rats are proposed. To specify tissues forming reduced metabolites, an in vitro study was conducted. Reduction was found to take place in red blood cells.     

Metabolism of 7-fluoro-6-(3,4,5,6-tetrahydrophthalimido)-4- (2-propynyl)-2H-1,4-benzoxazin-3(4H)-one (S-53482) in rat. 1. Identification of a sulfonic acid type conjugate

To examine the metabolic fate of 7-fluoro-6-(3,4,5, 6-tetrahydrophthalimido)-4-(2-propynyl)-2H-1,4-benzoxazin-3( 4H)-one (S-53482), rats were given a single oral dose of [phenyl-(14)C]-S-53482 at 1 (low) or 100 (high) mg/kg. The radiocarbon was almost completely eliminated within 7 days after administration in both groups. (14)C recoveries (expressed as percentages relative to the dosed (14)C) in feces and urine were 56-72 and 31-43%, respectively, for the low dose and 78-85 and 13-23%, respectively, for the high dose. S-53482 and seven metabolites were identified in urine and feces. Six of them were purified by several chromatographic techniques and identified by spectroanalyses (NMR and MS). Alcohol derivatives and an acetoanilide derivative were isolated from urine. Three sulfonic acid conjugates having a sulfonic acid group incorporated into the double bond of the 3,4,5,6-tetrahydrophthalimide moiety were isolated from feces. On the basis of the metabolites identified in this study, the metabolic pathways of S-53482 in rats are proposed.     

Identification of potent odorants formed by autoxidation of arachidonic acid: structure elucidation and synthesis of (E,Z,Z)-2,4,7-tridecatrienal.

The aroma composition of autoxidized arachidonic acid was characterized by aroma extract dilution analysis. The most potent odorant was trans-4,5-epoxy-(E)-2-decenal followed by 1-octen-3-one, (E,Z)-2,4-decadienal, (E,Z,Z)-2,4,7-tridecatrienal, (E,E)-2,4-decadienal, and hexanal. (E,Z,Z)-2,4,7-Tridecatrienal was unequivocally identified by mass spectrometry and nuclear magnetic resonance (NMR) data. The stereochemistry of its extended double-bond system was elucidated on the basis of NMR measurements. The target compound was synthesized in four steps starting with bromination of 2-octyn-1-ol, followed by copper-catalyzed coupling of the bromide with ethylmagnesium bromide and (E)-2-penten-4-yn-1-ol. Partial hydrogenation of the resulting C(13)-compound with triple bonds in the positions C-4 and C-7 gave rise to (E,Z,Z)-2,4,7-tridecatrien-1-ol, which was finally oxidized to the target compound. It exhibits a typical egg-white-like, marine-like odor at low concentrations, and an intense orange-citrus, animal-like odor at higher concentrations. Its odor threshold was estimated by gas chromatography-olfactometry to be 0.07 ng/L air, which is of the same order of magnitude as that reported for 1-octen-3-one and (E,E)-2,4-decadienal.     

Ovine metabolism of lithogenic sapogenins. Synthesis of [2,2,4,4-(2)h(4)]sarsasapogenone, [2,2,4,4-(2)h(4)]sarsasapogenin,and [2,2,4,4-(2)h(4)]episarsasapogenin and evaluation of deuterium retention in a sheep-dosing trial

The suitability of [2,2,4,4-(2)H(4)]sarsasapogenone (1b), [2,2,4,4-(2)H(4)]sarsasapogenin (2b), and [2,2,4,4-(2)H(4)]episarsasapogenin (3b) as isotopically labeled dosing substrates to determine the levels of free and conjugated sapogenins present in feces from sheep grazing saponin-containing plants implicated in the development of ovine heptagenous photosentization diseases was investigated. A 1:4 mixture of [2,2,4,4-(2)H(4)]sarsasapogenin (2b) and [2,2,4,4-(2)H(4)]episarsasapogenin (3b), obtained by reduction of [2,2,4,4-(2)H(4)]sarsasapogenone (1b), was found to retain 94% of incorporated deuterium, when dosed to one sheep. The recovery of the dosed mixture of genins 2b and 3b was calculated to be 85%. Considerable loss of deuterium and a lower recovery of genin material were observed when [2,2,4,4-(2)H(4)]sarsasapogenone (1b) was dosed.     

Synthesis and herbicidal activity of 2-cyano-3-(2-chlorothiazol-5-yl)methylaminoacrylates

A series of 2-cyano-3-(2-chlorothiazol-5-yl)methylaminoacrylates were synthesized as herbicidal inhibitors of PSII electron transport. All of these compounds exhibited good herbicidal activities. In particular, (Z)-ethoxyethyl 2-cyano-3-isopropyl-3-(2-chlorothiazol-5-yl)methylaminoacrylate showed excellent herbicidal activities even at a dose of 75 g/ha. A suitable group at the 3-position of acrylate was essential for high herbicidal activity. 2-Cyanoacrylates containing a 2-chloro-5-thiazolyl group are a novel class of herbicides and display herbicidal activities comparable to existing analogues bearing chloropyridyl or chlorophenyl.     

Structure-Activity Relationships (SAR) studies of benzoxazinones, their degradation products and analogues. phytotoxicity on standard target species (STS)

Benzoxazinones 2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (DIMBOA) and 2,4-dihydroxy-(2H)-1,4-benzoxazin-3(4H)-one (DIBOA) have been considered key compounds for understanding allelopathic phenomena in Gramineae crop plants such as corn (Zea mays L.), wheat (Triticum aestivum L.), and rye (Secale cereale L.). The degradation processes in the environment observed for these compounds, in which soil microbes are directly involved, could affect potential allelopathic activity of these plants. We present in this work a complete structure-activity relationships study based on the phytotoxic effects observed for DIMBOA, DIBOA, and their main degradation products, in addition to several synthetic analogues of them. Their effects were evaluated on standard target species (STS), which include Triticum aestivum L. (wheat) and Allium cepa L. (onion) as monocots and Lepidium sativum L. (cress), Lactuca sativa L. (lettuce), and Lycopersicon esculentum Will. (tomato) as dicots. This permitted us to elucidate their ecological role and to propose new herbicide models based on their structures. The best phytotoxicity results were shown by the degradation chemical 2-aminophenoxazin-3-one (APO) and several 2-deoxy derivatives of natural benzoxazinones, including 4-acetoxy-(2H)-1,4-benzoxazin-3(4H)-one (ABOA), 4-hydroxy-(2H)-1,4-benzoxazin-3(4H)-one (D-DIBOA), and 4-hydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one (D-DIMBOA). They showed high inhibitory activity over almost all species growth. The fact that APO is a degradation product from DIBOA with high phytotoxicity and stability makes it possible to assign an important ecological role regarding plant defense mechanisms. 2-Deoxy derivatives of natural benzoxazinones display a wide range of activities that allow proposing them as new leads for natural herbicide models with a 1,4-benzoxazine skeleton.     

Synthesis and herbicidal activity of 2-(7-fluoro-3-oxo- 3,4-dihydro-2H-benzo[b][1,4]oxazin-6-yl)isoindoline-1,3-diones

The mode of action of 2-(7-fluoro-3-oxo-3,4-dihydro-2H-benzo[b][1,4]oxazin-6-yl)-4,5,6,7-tetrahydro-2H-isoindoline-1,3-diones, including the commercial herbicide flumioxazin, had been identified as inhibition of protoporphyrinogen oxidase (protox). As part of continuous efforts to search for new herbicides with high efficacy, broad-spectrum activity, and safety to crops, flumioxazin and its iodo analogue (B2055) were used as lead compounds for further optimization. Series of novel compounds were prepared by multistep synthetic procedures starting from 5-fluoro-2-nitrophenol. All of the test compounds were structurally confirmed by 1H NMR, IR, mass spectroscopy, and elemental analysis. Preliminary bioassay data showed that some of them possess commercial levels of herbicidal activity comparable to those of other protox-inhibiting herbicides. One of the best compounds, 5-fluoro-2-(7-fluoro-3-oxo-4-(prop-2-ynyl)-3,4-dihydro-2H-benzo[b][1,4]oxazin-6-yl)isoindoline-1,3-dione (8e), has IC50 values for velvetleaf (Abutilon theophrasti Medic) and crabgrass (Digitaria sanguinalis) comparable to thos of B2055. With respect to crop selectivity, compound 8e is similar to flumioxazin. Compound 8e is safe to cotton and maize at a rate of 150 g of active ingredient (ai)/ha or less when applied at pre-emergent stage, and it has the best safety to wheat among the tested crops, showing no injury after post-emergent application at 7.5-30 g of ai/ha.     

Field trapping of the invasive brown marmorated stink bug, Halyomorpha halys, with geometric isomers of methyl 2,4,6-decatrienoate

The brown marmorated stink bug, Halyomorpha halys (St?l), is a polyphagous pest indigenous to northeastern Asia where it damages various trees, vegetables, and leguminous crops. The bug was recently introduced into the U.S. and could potentially become a pest. In its native range, H. halys was reportedly attracted to the aggregation pheromone of the brown-winged green bug, Plautia stali, methyl (2 E,4 E,6 Z)-decatrienoate. We also observed that traps baited with this compound are attractive to H. halys. We additionally found that methyl (2 E,4 E,6 Z)-decatrienoate (as well as other isomeric methyl 2,4,6-decatrienoates) exposed to daylight in solutions and/or on dispensers used for field trapping can readily isomerize to form complex mixtures of isomers, thus causing a concern about lure stability and longevity. However, our studies demonstrated that preventing isomerization of methyl (2 E,4 E,6 Z)-decatrienoate in dispensers was not essential for field trapping of H. halys males, females, and nymphs. We also present evidence that traps baited with methyl (2 Z,4 E,6 Z)-decatrienoate and methyl (2 E,4 Z,6 Z)-decatrienoate (pheromone of Thyanta spp. pentatomids), as well as the mixtures of geometric isomers, attract H. halys. The ZEZ isomer, unknown in nature, as well as the EEZ isomer, elicited electrophysiological responses from antennae of H. halys males. The field data suggest that the presence of the EEZ but not ZEZ isomer in the lure is essential for attraction of H. halys, and that other isomers are not antagonistic and may even be needed for maximum attraction. Because the pheromone of H. halys is unknown at present, lures containing methyl (2 E,4 E,6 Z)-decatrienoate without protection from daylight are suitable for monitoring populations of H. halys late in the season.     

Alpha-mercaptoketone formation during the maillard reaction of cysteine and [1-(13)C]ribose

The volatiles formed from [1-(13)C]-ribose and cysteine during 4 h at 95 degrees C in aqueous phosphate buffer (pH 5) were analyzed by headspace SPME in combination with GC-MS. The extent and position of the labeling were determined using MS data. The identified volatiles comprised sulfur compounds such as 2-[(13)C]methyl-3-furanthiol, 2-[(13)CH(2)]furfurylthiol, [1-(13)C]-3-mercaptopentan-2-one, [1-(13)C]-3-mercaptobutan-2-one, [4-(13)C]-3-mercaptobutan-2-one, and 3-mercaptobutan-2-one. The results confirm furan-2-carbaldehyde as an intermediate of 2-furfurylthiol, as well as 1,4-dideoxypento-2,3-diulose as an intermediate of 2-methyl-3-furanthiol and 3-mercaptopentan-2-one. Loss of the C-1 and C-5 carbon moieties during the formation of 3-mercaptobutan-2-one suggests two different mechanisms leading to the key intermediate butane-2,3-dione.