Peter Baeckström

Differences in attraction to semiochemicals present in sympatric pine shoot beetles,Tomicus minor andT. piniperda.

The chemical ecology of host- and mate-finding in the pine shoot beetles,Tomicus minor andT. piniperda, was studied in southern Sweden. Beetles were collected in the field from defined attack phases on Scots pine. Using gas chromatography-mass spectroscopy, a number of oxygen-containing monoterpenes, e.g., 3-carene-10-ol, myrtenol,trans-verbenol, and verbenone, were identified from hindgut extracts of both sexes of both species. Compared toT. minor,T. piniperda contained additional compounds and in larger amounts. The amounts were highest in both species at the time when the beetles had bored into contact with the resin-producing xylem-phloem tissue. The synthesis of (1S,6R)-3-carene-10-ol by photooxidatipn of (+)-(1S,6R)-3-carene is described. In comparative electroantennogram (EAG) measurements on males and females of both species, the most active of the tested compounds wastrans-verbenol. Laboratory bioassays of walking beetles showed thatT. piniperda was attracted to uninfestèd pine logs.T. minor was more strongly attracted to pine logs infested with females than to uninfested pine logs, indicating a female-produced aggregation pheromone. Field tests confirmed thatT. piniperda was strongly attracted to pine logs. The attraction ofT. minor to logs was significant only when logs were combined with racemictrans-verbenol and (1S,6R)-3-carene-10-ol.T. minor was also attracted to a combination of these monoterpene alcohols alone. We suggest that host and mate location inT. piniperda is achieved by means of a kairomone composed of host monoterpenes, whileT. minor utilizes a primitive pheromone synergized by host odors. Evolution of host colonization strategies of the two beetles are discussed.

Tick repellent substances in the essential oil of Tanacetum vulgare

Abstract The repellent effect of the essential oils of flower heads of the aromatic plant tansy, Tanacetum vulgare L. (Asteraceae), originating from Sweden, was tested against host-seeking nymphs of the common tick Ixodes ricinus (L.). The essential oils were obtained by steam distillation (SD) and by using an online solvent extraction separation setup. Further fractionations of the SD oils were obtained by medium-pressure liquid chromatography on silica gel. The volatiles of the essential oils and the fractions that exhibited strong tick repellency (90–100%) were collected by solid phase microextraction and identified by gas chromatography-mass spectrometry. The chemical analyses of the oils show that the populations of T. vulgare from Uppsala and Stockholm may represent different chemotypes, but that they exhibited similar tick repellency. Main volatiles detected from oils of T. vulgare collected at Uppsala were &agr;-pinene (27%), &bgr;-pinene (11%), pinocamphone (11%), 1,3,3-trimethylcyclohex-1-ene-4-carboxaldehyde (11%), and 1,8-cineole (10%). In the sample collected in Stockholm, the main components were &bgr;-thujone (39%) and camphor (23%) followed by &agr;-thujone (11%) and 1,8-cineole (8%). When constituents in the oils, e.g., &agr;-terpineol, 4-terpineol, &agr; + &bgr;-thujone, 1,8-cineol, verbenol, and verbenone, were tested separately (each diluted 0.5%, vol:vol), 64–72% tick repellency was obtained.

Synthesis and characterization of all four isomers of methyl 2,4-decadienoate for an investigation of the pheromone components of Pityogenes chaicographus

Synthesis and Characterization of All 4 Isomers of Methyl 2,4-Decadienoate for an Investigation of the Pheromone Components of Pityogenes-Chalcographus

Photochemical formation of chrysanthemic acid and cyclopropylacrylic acid derivatives: A case of multiplicity-dependent regiospecificity in the di-π-methane rearrangement

Abstract Photochemical transformations of methyl E- and Z - 4,4,6 - trimethyl - 2,5 - dienoate ( 5a ) and of the corresponding acids ( 5b ) have been investigated. In contrast to similar pure hydrocarbon di-π-methanes, these aliphatic α,β-unsaturated car☐ylic acid derivatives react from both the singlet and the triplet excited states and form different types of vinylcyclopropanes depending on multiplicity. When irradiated in acetone, both 5aE and 5aZ give methyl E - 3(2,2,3,3 - tetramethylcyclopropyl)prop - 2 - enoate ( 8aE ). The same is observed for the corresponding acids. Direct irradiation of 5aE , but not of 5aZ , readily gives methyl E-chrysanthemate ( 4aE ). Only singlet excited 5Z reacts by internal hydrogen abstraction to cyclopropylacetic add derivatives ( 7 ). Procedures for independent synthesis of 7 and 8 are described.

Field response of the pine sawflyNeodiprion sertifer to controlled release of diprionyl acetate, diprionyl propionate andtrans-perillenal

Two dispenser types for pine sawfly (Hymenoptera: Diprionidae) pheromones—glass capillaries and dental cotton rolls—are described, and release rates reported. Glass capillaries of different diameters were used in field tests to determine dose-response relationships of (2S,3S,7S)-3,7-dimethylpentadecan-2-yl acetate (diprionyl acetate), diprionyl propionate, andtrans-perillenal on the trap catch of maleNeodiprion sertifer. A linear relationship between the logarithm of the capillary cross-sectional area and the logarithm of the release rate was found. However, capillaries of the same diameter could vary in the amount released by as much as a factor of 10. Both the acetate and propionate were attractive alone, but no synergistic effect was found.trans-Perillenal did not show any behavioral activity. Dental cotton rolls have been used extensively in diprionid pheromone research without knowledge about release rates. The release rate from rolls loaded with different amounts of diprionyl acetate was determined by extracting rolls after different times under constant temperature and wind conditions or after use in field tests. Quantification of diprionyl acetate was done on GC. The release rate was found to be proportional to the amount applied over several orders of magnitude, and persisted for several weeks. Capillaries and rolls with similar release rates caught similar numbers of sawflies.

Structures, absolute configurations, and syntheses of volatile signals from three sympatric ant-lion species,Euroleon nostras, Grocus bore, andMyrmeleon formicarius (Neuroptera: Myrmeleontidae).

The thoracic gland of the ant-lionEuroleon nostras was found to contain nerol oxide (1a) and (Z)-6-undecen-2-ol (nostrenol,3) while the speciesGrocus bore contained 10-homonerol oxide (1b) and nostrenol (3). Nerol (2a) and 10-homonerol (2b) were found in a third species,Myrmeleon formicarius. 10-Homonerol, racemic 10-homonerol oxide, and racemic as well as (R)- and (S)-nostrenol were synthesized. The nerol oxide ofE. nostras and the 10-homonerol oxide ofG. bore were found to be racemic, while both species contained optically pure (R)-nostrenol (28).

A Synthesis of Trans-β-Farnesene from Myrcene which Includes a Modified Work up Method for DIBAH Reductions of Esters to Aldehydes

Abstract A simple synthesis of trans-β-farnesene, an alarm pheromone for aphids, from myrcene is described and a reliable procedure for working up of DIBAH reduction from esters to aldhydes is introduced.

A One Pot Procedure for the Deoxygenation of α, β-Unsaturated Ketones and a Synthesis of the Mealybug Pheromone

Abstract An improved one pot reaction that achieves the deoxygenation of α,β-unsaturated ketone with concomitant migration of the double bond is introduced, and applied to the synthesis of racemic 3-acetoxy-2,6-dimethyl-1,5-heptadiene, a pheromone component of Pseudococcus comstocki.

Isoprenoid chain elongations by Claisen rearrangements using acetals as precursors of vinyl ethers

Abstract Claisen rearrangements of allyl vinyl ethers, formed in situ by the acid catalyzed reaction of dimethyl acetals of acetaldehyde, acetone and isopropeny] methyl ketone with different types of allylic alcohols, have been compared. The primary, secondary and tertiary allylic alcohols used in the investigation were selected to serve as models for isoprenoid synthesis. The basis for two feasible methods that can be iterated to create isoprenoid chains has been investigated.

Studies on essential oil-bearing plants from mozambique: Part II. volatile leaf oil of needles of Pinus elliottii engelm. and Pinus taeda L

Abstract Essential oil composition of fresh needles from Pinus elliottii (slash pine) and Pinus taeda L. (loblolly pine) grown in Mozambique were investigated by a combination of GC and GC/MS. The present investigation revealed the following composition of P. elliottii and P. taeda: tricyclene (2.1% and 3.8%), α-pinene (43.0% and 62.3%), β-pinene (27.1% and 7.1%), limonene (2.9% and 2.0%), myrcene (2.3% and 1.8%) and β-phellandrene (1.1% and 3.7%), respectively. Among the oxygenated monoterpenes present, the most significant was α-terpineol (9.6% and 2.3%, respectively). Expected regional variability on the chemical composition of the corresponding tree species was examined.