Mid Sweden University

A GC-MS method to analyze the stereoisomeric composition of chiral secondary alcohols found in whole body extracts of pine sawfly females was developed. The tested alcohols were derivatized with optically pure (S)-2-acetoxypropionyl chloride prior to GC-MS analysis. Baseline separation was obtained for all sixteen stereoisomers of 3,7,9-trimethyltridecan-2-ol and for the four 3-methylpentadecan-2-ol stereoisomers. For 3,7-dimethyltridecan-2-ol, 3,7-dimethyltetradecan-2-ol and 3,7-dimethylpentadecan-2-ol baseline separation was obtained for 6 of the possible 8 stereoisomers. When a mixture of 16 stereoisomers of 3,7,11-trimethyltridecan-2-ol was tested, baseline separation of 7 peaks out of 16 possible was obtained. The investigated alcohols are pheromone precursors for some pine sawfly species that are severe defoliators of pine. Females from several Diprion, Neodiprion, Macrodiprion, Microdiprion, and Gilpinia species emit esters of such secondary alcohols as sex pheromones that attract males for mating. To quantify the small amounts of the precursor alcohol and its stereoisomeric composition found in whole body extracts from female pine sawflies, a purification method was optimized. An extract of 20 females of D. pini contained about 8 ng of (2 S,3 R,7 R)-3,7-dimethyltridecan-2-ol per female, and three extracts of 18, 20, and 90 females of N. sertifer contained between 5 and 13 ng of (2 S,3 S,7 S)-3,7-dimethylpentadecan-2-ol per female.

Latex-based coatings for protection of tree seedlings against pest insect feeding are evaluated with respect to surface-, mechanical-, and release properties and antifeedant activity. The latex dispersion Eudragit copolymer (EC) was used to form the coatings, 2,6-di-tert-butyl-4-methylphenol (BHT) and cis-dihydropinidine (Alk) as antifeedants, and a thickener and a alkylglucoside based nonionic surfactant were used as additives to optimize the release- and mechanical properties of coatings. Coating characterization was performed with respect to surface morphology (atomic force microscopy, AFM) and surface wetting (contact angle), as well as to mechanical (tensile stress- and tensile strain at break) properties. Surface smoothness and wettability as well as elasticity increased with addition of the surfactant. The optimized coatings were found to be elastic and water resistant at 3-6 wt.% of BHT and 3 wt.% of surfactant. BHT was released into SDS/water at very low rates. Several formulations of BHT and Alk were efficient in preventing the feeding on conifer bark by a pine insect, Hylobius abietis both in laboratory (no-choice) and in held Q months) tests.

Thiophenol was added to racemic cryptone (4-isopropyl-2-cyclohexene-1-one) and the resulting 1,4-addition products, cis- and trans-4-isopropyl-3-(phenylsulfanyl)cyclohexanone) were separated and the latter reduced to rac-1,3-cis-1,4-trans-4-isopropyl-3-(phenylsulfanyl)cyclo¬he¬xanol which was subjected to lipase catalysed resolution by acylation catalysed by CAL-B (Candida antarctica lipase B). The remaining alcohol was separated from the produced acetate, which was hydrolysed to the alcohol. The enantiomeric alcohols so obtained were oxidised. The initial products, probably sulfoxidoketones spontaneously decomposed to furnish enantiomerically enriched (R)- and (S)-cryptone with up to 76% and 98% ee, respectively.

A medium-length, straight-chain alkanoic acid, nonanoic acid, is known from laboratory microassays to be an antifeedant in adults of the large pine weevil, Hylobius abietis (L.) (Coleoptera: Curculionidae). Our hypothesis was that we could find new, less volatile alkanoic acids or related compounds suitable for field application and with improved long-term duration. Alkanoic acids of varying chain lengths (C6-C13) were tested for antifeedant activity in H. abietis adults. Microassay choice tests showed that straight-chain (C6-C11) alkanoic acids were active. However, high activities were restricted to the (C6-C10) acids, with the C9 (nonanoic acid) at 4 μmol cm-2 being the most active one. In a no-choice test on pine twigs, the antifeedant effect of C10 acid was lower than that of the C8 and C9 acids. In microassays, less volatile methyl-branched alkanoic acids exhibited lower antifeedant activities than did the corresponding straight-chain ones. However, the most active of the methyl-branched acids, 2-methyldecanoic acid, had an activity similar to that of nonanoic acid. Compounds related to nonanoic acid were either active (1-nonanol), weakly active (nonanoic anhydride), or inactive (nonanal, sodium nonanoate). The anhydride was highly active in the microassay, but less active on twigs. The antifeedant effects of the straight chain (C8-C10) alkanoic acids against pine weevil feeding were tested in the field. In contrast to the results from the twig tests, the less volatile C10 acid was more active in the field for the protection of transplants on fresh clear cuts over a 3-month period than both the C8 and C9 acids. Phytotoxic effects of the alkanoic acids were observed both in the field and in laboratory studies. If a protective layer of paraffin was applied to the stem prior to application of the alkanoic acids, these undesired side effects were reduced.

The enantiomers of the naturally occurring alkaloid dihydropinidine 1, potential antifeedants against the pine weevil, Hylobius abietis, were prepared by diastereoselective, dimethylzinc mediated addition of pinacolyl 2-propenylboronate 14 to nitrones (R)- and (S)-2-methyl tetrahydropyridine-N-oxide 3, prepared from d- and l-alanine, respectively.

Linden (Tilia cordata) bark contains antifeedants effective against the large pine weevil, Hylobius abietis. Soxhlet extraction of inner and outer bark resulted in an extract which showed antifeedant activity in a micro-feeding assay. The extract was fractionated by chromatography on silica gel using gradient elution with solvents of increasing polarity. The content of the fractions obtained was monitored by thin layer- and gas chromatography. Fractions of similar chemical composition were merged. Two of the 17 fractions showed antifeedant activity in the micro feeding assay. Nonanoic acid was identified in both of these fractions. Subsequent testing in the micro feeding assay showed that nonanoic acid possessed strong antifeedant activity against H. abietis adults.

The monoterpenoid carvone (1) has been shown to have strong antifeedant effects on Hylobius spp. However, because of the high volatility of carvone, long-time protection of conifer seedlings in the field using this compound has not been possible. We demonstrate, in several bioassay steps, that less-volatile, heavier analogues retain their pre-ingestive feeding inhibition activity in the large pine weevil, Hylobius abietis (L.) for a longer time. The first step in the evaluation of the biological activity of 12 carvone analogues was a micro-assay, a choice test lasting 4 h. Compounds active at 100 nmol/cm(2) were further dose-response tested to give the effective dose needed to inhibit feeding by 50% (ED50). Of the 14 compounds tested, including both carvone enantiomers, seven heavier analogues were active at low doses (had low ED50 values). As expected from their lower vapour pressure compared with carvone, the heavier analogues proved more resistant to evaporation before testing. Thus, whereas the effect of 8-hydroxy-p-menth-en-6-one 4 declined after 2 days, some of the compounds with high molar masses, such as the alkylhydroxymenthenones 6 and 8, retained a stable activity for 4 days. The retained activity at 4 days was strongly correlated to molecular mass and boiling point. When tested on natural material (host Pinus sylvestris L. twig sections for 48 h), the heavier analogues showed a rather low activity. Probably, the activity of the more volatile compound carvone (1) is due to a repellent effect (olfactory mode) rather than the deterrent effects (gustatory mode) of the heavier compounds. In agreement with the relatively low activity on twigs in the laboratory, the hydroxymenthenone 4 was not active in the field when tested for 2 months as a 1 : 9 mixture with a polar wax.