Jan Vrkoč

Contents and Enantiomeric Compositions of Monoterpene Hydrocarbons in Xylem Oleoresins from Four Pinus Species Growing in Cuba. Comparison of Trees Unattacked and Attacked by Dioryctria horneana

Abstract Monoterpene hydrocarbons from the xylem oleoresins of Pinus tropicalis, P. caribaea var. caribaea, P. cubensis and P. maestrensis growing in Cuba were investigated. A large number of oleoresin samples from trees, attacked and unattacked by the moth Dioryctria horneana , as well as from trees growing in different localities, were analyzed. In each sample, the relative amounts of the volatiles and the enantiomeric compositions of six chiral monoterpene hydrocarbons were determined using a two-dimensional gas chromatographic (2D-GC) system. The GC-data were evaluated using two methods for multivariate data analysis, PCA (principal components analysis) and PLS-DA (projections to latent structures-discriminant analysis). PC-plots based on the relative amounts of the monoterpenes present in the volatile oleoresin fractions analyzed, showed that P. tropicalis and P. cubensis formed one group, separated from P. caribaea , while pines belonging to the species P. maestrensis were found in both groups. The species P. tropicalis and P. maestrensis , both of which are resistant to D. horneana , and the subgroups within the species P. caribaea and P. cubensis , that had not been attacked by D. horneana , showed no signs of constituting a chemical subgroup. No significant difference was found between the attacked and the unattacked P. cubensis trees. In P. caribaea , on the other hand, the composition of volatiles in attacked trees was significantly different from that in unattacked trees. However, an influence of monoterpenes on the oviposition of D. horneana was not proved.

Phenolic meroterpenoids from the basidiomycete Albatrellus ovinus

Abstract From the lipophilic fraction of fresh Albatrellus ovinus , the following substances were isolated and identified: E,E -5-methyl-2-(3,7,11 -trimet

Rubber substrates and their influence on isomerization of conjugated dienes in pheromone dispensers

Release rate and degree of isomerization of pheromones with conjugated double bonds were studied in dispensers prepared from several rubber substrates. The substrates compared were made of rubber, cured with elemental sulfur or accelerators based on organic sulfur compounds or organic peroxides. Isomerization of the double bonds occurs immediately after impregnation of the substrate, and the degree of isomerization increases during field use and/or storage. The propensity of the isomers to isomerize corresponds to their proportion in the equilibrium mixture. AnE,Z isomer is isomerized faster than theE,E isomer, and finally a near-equilibrium mixture of the four isomers is present. Minimal isomerization was found in non-sulfur-cured substrates which are the material of choice.

Chirality of the monoterpene alarm pheromones of termites

ity. Our results imply that the chromatographic determination of enantiomeric compositions is to be preferred to the traditional determination of optical purities by resorting to chiroptical methods (e.g., polarimetry [5]). For very complex matrices the enantiomer analysis may preferentially be performed by gas chromatography-mass spectrometry in the selected ion monitoring (SIM) mode [3]. Generous support of this work by the Deutsche Forschungsgemeinschaft and the Fonds der chemischen Industrie is gratefully acknowledged.

Biotransformations of γ-methyl-β-ketosulfones: stereoselectivity of 3-methyl-1-(phenylsulfonyl)hexan-2-one reductions by various yeasts

Abstract The stereoselectivity of the reduction of rac-3-methyl-1-(phenylsulfonyl)hexan-2-one (1) to 3-methyl-1-(phenylsulfonyl)hexan-2-ol (2) diastereomers by more than 20 yeasts was studied. Reduction of carbonyl group in 1 proceeds with a high Re-face enantioselectivity: Candida guillermondii (989% e.e.), C. zeylanoides (>99.9%) and Kloeckera apiculata (99.6%), respectively and the (R)- 1 enantiomer usually reacted faster. The enantioselectivity was determined by GC on chiral cyclodextrine phases and absolute configurations of products were assigned by NMR spectroscopy and a chemical correlation.

Vanillin: Possible sex phermone of an insect

22. Alizade, M.A., Bressler, R., Brendel, K. : ibid. (in press) 23. Alizade, M.A., Bressler, R., Brendel, K. : ibid. 370, 354 (1974) 24. Fidge, N.H., Goodman, D.W.S.: J. Biol. Chem. 243, 4372 (1968) 25. Englard, S., Kaysen, G., Avigad, G.:ibid. 245, 1311 (1970) 1. Likventov, A.V.: Proc. 13th Internat. Congr. Entomol. 1, 52i (1971) 2. Likventov, A.V., in: Insect Chemoreception, p. I73 (ed. P. Zajanckauskas, etaL); Vilnius, U.S.S.R. : Proc. 1st All Union Symp. on Chemoreception, 1971 3. ~dfirek, J., Kontev, Ch.: Acta entomol, bohemoslov. (in press) 4. Likventov, A.V. : Bull. V.I.Z.R. 25, 37 (1973)

Enantiomeric composition of monoterpene hydrocarbons from the liverwort Conocephalum conicum

Volatiles from the essential oil of the liverwort Conocephalum conicum were analysed. The chirality of the monoterpene hydrocarbons was studied by two-dimensional ps chromatography. All compounds e ...

Arenophthalide A: A new phthalide glycoside from Helichrysum arenarium roots

Abstract Spectral data and degradations were used to determine the structure of arenophthalide A, a glycoside of the formula C19H24O9, isolated from the roots of Helichrysum arenarium. Structure I was assigned to the compound.

Gas chromatographic determination of vapour pressures of pheromone-like acetates

Abstract The vapour pressures of nineteen Z and E monounsatured C 10 C 16 even-carbon acetates were determined using a method based on gas chromatographic (GC) retention data. Experimental measurements were carried out at six temperatures in the range 90–140°C on a 2-m HP-1 capillary column by utilizing n -C 18 and n -C 20 hydrocarbons as vapour pressure reference compounds. Corrections for the systematic errors were made by relating the experimentally determined vapour pressures P GC to the literature values P L through a linea regression relationship. Over a narrow temperature range of 25–45°C, the GC-measured vapour pressures were found to satisfy the Clausius-Clapeyron equation. Also, for structurally similar subseries of acetates, e.g. , for ω - 3 or ω - 5 unsaturated derivatives, the vapour pressures were shown to have a simple dependence on the number of carbon atoms per molecule. The vapour pressures at 25°C ranged from 2.633 Pa for ( Z )-5-decenyl acetate to 0.005 Pa ( E -13-hexadecenyl acetate.

Experimental device for electrokinetic micellar chromatography exploiting some components of capillary isotachophoresis instrumentation

The device constructed for electrokinetic micellar chromatography (EMC) consists of a quartz capillary tube (700 mm × 0.05 mm I.D.), a polypropylene test-tube electrode compartments, a constant-current, high-voltage power supply and a newly developed fixed-wavelength UV photometric on-column detector. The UV detector contains a high-frequency excited electrodeless low-pressure iodine discharge lamp, the chopped light of which at a wavelength 206 nm is selected by an interference filter. A silicon photovoltaic detector with a high gain keying amplifier is used for the detection of extremely low light power (10−12 W) in a 1.6-nl on-column detection cell. The detection limit is 67 fmol (6.3 pg) of phenol (for a signal-to-noise ratio of 2). Examples of EMC separations, confirming the high sensitivity and selectivity of the method, are given.