| 111. |
- Nordin, Ove, et al.
(författare)
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Kinetic Resolution of Primary 2-methylalcohols via Pseudomonas cepacia Lipase Catalysed Enantioselective Acylation
- 2000
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Ingår i: Journal of The Chemical Society. Perkin Transactions 1. - : Royal Society of Chemistry (RSC). - 1472-7781 .- 1470-4358 .- 1364-5463. ; , s. 367-376
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Tidskriftsartikel (refereegranskat)abstract
- The enantioselectivities of lipases from Pseudomonas cepacia (PFL, Amano PS, etc.) towards a series of primary 2-methyl-substituted alcohols using vinyl acetate as the acyl donor in transesterifications in organic solvents were studied. In terms of enantioselectivity, the best results were found for 3-aryl-2-methylpropan-1-ols with enantiomeric ratios (E-values) over 100 in most cases, whereas other 3-substituted primary 2-methylpropan-1-ols generally displayed lower enantioselectivities: 3-cycloalkyl-2-methylpropan-1-ols (E ≈ 20) and 2-methylalkan-1-ols (E ≈ 10). Moving the aryl group closer or further away from the chiral centre resulted in low enantioselectivities: 2-arylpropan-1-ols (E < 10), 2-methyl-4-(2-thienyl)butan-l-ol (E = 12), 2-methyl-5-(2-thienyl)pentan-l-ol (E=3.2) and 2-methyl-6-(2-thienyl)hexan-l-ol (E=3.8).
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| 112. |
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| 113. |
- Persson, Gerd, et al.
(författare)
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Phase Behavior of 1-Alkylpyridinium Octane-1-sulfonates : Effect of the 1-Alkylpyridinium Counterion Size
- 2004
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 20:4, s. 1168-1179
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Tidskriftsartikel (refereegranskat)abstract
- The temperature-versus-composition phase diagrams of eight different 1-alkylpyridinium octane-1-sulfonates (APOSs) in water were studied by 1H NMR, 2H NMR, pulsed gradient spin−echo NMR, small-angle X-ray diffraction, differential scanning calorimetry, surface tension and conductivity measurements, and polarizing microscopy. The number of carbons (nc) in the hydrocarbon chain of the pyridinium counterions was varied from nc = 1 to nc = 8 to study how the phase behavior of the APOS/2H2O systems was affected by a change in the chain length of the counterion. The sodium octane-1-sulfonate (NaOS)/water system was used as a reference. This system formed an isotropic micellar solution (L1) phase and a normal hexagonal (HI) phase. All APOSs were readily soluble in water and formed L1 phases. The surface tension above the critical micelle concentration for nc between 1 and 3 was higher than that for NaOS, and it decreased steadily for the different APOSs with increasing chain length. The area per molecule at the air/solution interfaces was rather constant at 68 Å2 for nc between 1 and 7. For 1-octylpyridinium octane-1-sulfonate (OPOS), it was about 5 Å2 smaller, which was just outside the estimated error. However, the smallest area was obtained for NaOS. At higher surfactant concentrations, liquid crystalline phases formed. Both cubic and HI phases were found for nc = 1 and 2, while for nc between 3 and 5 only an HI phase was observed. HI and lamellar liquid crystalline (Lα) phases formed for nc = 6 and 7. The only liquid crystalline phase found in the OPOS system was a Lα phase. The NaOS HI phase was the only liquid crystalline phase that showed a linear relation between the 2H2O NMR quadrupolar splitting (ΔW) and Xsurf/XW, where Xsurf and XW are the mole fractions of surfactant and water. The OPOS lamellae were found to be much thinner than expected, indicating a defect lamellar structure. This was further supported by the behavior of the quadrupolar splitting of deuterated OPOS. The anomalous behaviors of the 2H2O NMR quadrupolar splitting observed in the Lα phases of 1-heptylpyridinium octane-1-sulfonate and OPOS were interpreted in terms of changes in the population of the water molecules residing in different sites combined with a continuous rearrangement of the lamellae surface with the possible development of holes. The appearances of the phase diagrams were discussed in terms of surfactant molecular geometry and the packing of the amphiphiles in the aggregates formed.
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| 114. |
- Persson, Per Valdemar, et al.
(författare)
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Selective organocatalytic ring-opening polymerization : A versatile route to carbohydrate-functionalized poly(e-caprolactenes)
- 2004
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 37:16, s. 5889-5893
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Tidskriftsartikel (refereegranskat)abstract
- Cationic catalysis using simple carboxylic acids to combine the ring-opening polymerization of c-caprolactone and the regioselective acylation of carbohydrates has been investigated. L-Lactic acid catalyzed the acylation of methyl beta-D-glucopyranoside and sucrose with epsilon-caprolactone in high yield by bulk polymerization at 120 degreesC. The main products were regioselectively acylated on the primary hydroxyl groups of the carbohydrate end groups. The overall conversion to methyl beta-D-glucopyranoside-functionalized poly(epsilon-caprolactone) was more than 90%, M-w 2000 and polydispersity index 1.5, with one major product methyl 6-O-poly(epsilon-caprolactone)-beta-D-glucopyranoside, in agreement with the corresponding Candida antarctica lipase B-catalyzed acylation
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| 115. |
- Pokorny, T., et al.
(författare)
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Acquisition of species-specific perfume blends : Influence of habitat-dependent compound availability on odour choices of male orchid bees (Euglossa spp.)
- 2013
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 172:2, s. 417-425
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Tidskriftsartikel (refereegranskat)abstract
- Male orchid bees (Euglossini, Apidae, Hymenoptera) expose species-specific blends of volatile chemicals (perfume bouquets) during their courtship display. The perfumes are acquired by collecting fragrant substances from environmental sources, which are then accumulated in specialised hind leg pouches. To balance the perfume composition, the males need to find and collect the required substances in specific relative amounts while facing seasonal, local or habitat-dependent differences in compound availability. Experience-dependent choice of odours, i.e. 'learned avoidance' of recently collected components, has been proposed as the mechanism that mediates the accumulation of the stereotypical compound ratios. In the present study, we used the presence of certain compounds in male hind leg pouches as proxy for the respective local compound availability, and investigated whether differences in content are correlated with differences in chemical choice assays. Our results suggest that volatile availability differs between localities (n = 16) as well as habitats (n = 2; coastal vs. inland) across the Yucatán peninsula, Mexico, for both studied species. Male Euglossa dilemma showed a pronounced preference for benzyl benzoate and eugenol at locations where those compounds were rare in hind leg extracts, as predicted by the learned avoidance model. No equivalent correlations were found for Euglossa viridissima. This is the first study to combine chemical analyses of perfumes with bioassays of odour choice. It strengthens the view that negative feedback from collected odours modifies future chemical choice and helps males to acquire specific perfume blends. © 2013 Springer-Verlag Berlin Heidelberg.
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| 116. |
- Rahmani, Rizan, et al.
(författare)
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Identification and Field Assay of Two Aggregation Pheromone Components Emitted by Males of the Bark Beetle Polygraphus punctifrons (Coleoptera: Curculionidae)
- 2019
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Ingår i: Journal of Chemical Ecology. - : Springer Science and Business Media LLC. - 0098-0331 .- 1573-1561. ; 45:4, s. 356-365
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Tidskriftsartikel (refereegranskat)abstract
- The bark beetle Polygraphus punctifrons (Coleoptera: Curculionidae) is a species that feeds on Norway spruce (Picea abies) and is found in the Northern parts of Europe and Russia. The release of volatile organic compounds (VOCs) produced by males and females of P. punctifrons when the beetles bore into spruce stem sections in a laboratory environment was studied using solid phase microextraction (SPME). The sampled VOCs emitted by boring beetles were analysed by gas chromatography and mass spectrometry (GCMS). (+)-2-[(1R,2S)-1-Methyl-2-(prop-1-en-2-yl)cyclobutyl]ethanol [(+)-(1R,2S)-grandisol] and (−)-(R)-1-isopropyl-4-methyl-3-cyclohexen-1-ol [(−)-(R)-terpinen-4-ol] were identified to be male specific volatiles. The identity of the compounds was confirmed by comparison with synthetic samples. Field trials with synthetic compounds in Sweden showed that racemic grandisol per se was strongly attractive for both males and females, while (−)-(R)-terpinen-4-ol was not. Further, when adding (−)-(R)-terpinen-4-ol to rac-grandisol, a synergistic effect was observed as the trap catch of P. punctifrons was fourfold. (−)-(R)-Terpinen-4-ol by its own did not attract P. punctifrons but Polygraphus poligraphus, and the latter was also attracted to traps baited with a 10:90 mixture of the two compounds. Thus, we have identified (+)-(1R,2S)-grandisol as a main component and (−)-(R)-terpinen-4-ol as a minor component of the aggregation pheromone of P. punctifrons. This opens future possibilities to monitor and, if necessary, manage populations of P. punctifrons.
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| 117. |
- Rahmani, Rizan, et al.
(författare)
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Identification and synthesis of putative pheromone components of the threatened salt marsh bagworm moth, Whittleia retiella (Lepidoptera: Psychidae)
- 2020
-
Ingår i: Journal of Chemical Ecology. - : Springer Science and Business Media LLC. - 0098-0331 .- 1573-1561. ; 46, s. 115-127
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Tidskriftsartikel (refereegranskat)abstract
- Whittleia retiella (Newman, 1847) is a threatened salt marsh species of the bagworm moth family Psychidae. For its preservation it is necessary to develop efficient tools to survey its distribution and habitat requirements in order to use appropriate conservation methods. Such tools may be pheromone-based monitoring systems, which have documented efficacy in establishing the occurrence of cryptic insect species in nature. By using gas chromatography combined with electroantennographic detection (GC-EAD), we found two compounds in female W. retiella headspace samples and whole-body extracts that elicited electrophysiological activity in male antennae. Gas chromatograpy coupled with mass spectrometry (GC-MS) operating in electron impact (EI) mode and comparison of the analytical data with those of synthetic reference compounds showed the chemical structures of these putative pheromone components to be (1S)-1-methylpropyl (5Z)-dec-5-enoate and 1-methylethyl (5Z)-dec-5-enoate. Field assays using baits loaded with synthetic compounds revealed that conspecific males were attracted to (1S)-1-methylpropyl (5Z)-dec-5-enoate alone or in combination with 1-methylethyl (5Z)-dec-5-enoate, whereas 1-methylethyl (5Z)-dec-5-enoate neither attracted nor repelled males in the field assays when tested alone. This study shows the potential of using (1S)-1-methylpropyl (5Z)-dec-5-enoate for monitoring W. retiella to gather more detailed information about the geographic distribution and habitat needs of this rare moth.
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| 118. |
- Rahmani, Rizan, et al.
(författare)
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Identification of sesquisabinene B in carrot (Daucus carota L.) leaves as a compound electrophysiologically active to the carrot psyllid (Trioza apicalis Förster)
- 2019
-
Ingår i: Chemoecology. - : Springer Science and Business Media LLC. - 0937-7409 .- 1423-0445. ; 29:3, s. 103-110
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Tidskriftsartikel (refereegranskat)abstract
- The Carrot psyllid, Trioza apicalis Förster (Homoptera: Psylloidea: Triozidae) is one of the major insect pests of carrots (Daucus carota L.) in parts of northern and central Europe. Gas chromatography–single-sensillum recording (GC–SSR) previously confirmed several active compounds in a carrot leaf extract, but the most active compound remained unidentified. Mass fragmentation patterns observed from the unidentified active compound when analyzed by gas chromatography and mass spectrometry (GC–MS) was used to propose β-sesquiphellandrene and α-cis-bergamotene to be candidates as the unidentified compound. The compounds were synthesized and their mass spectra were nearly identical with the unknown active compound. But, the retention times differed from the compound in the carrot leaf extract. Thus, to obtain the unidentified compound pure enough and in adequate amounts for nuclear magnetic resonance (NMR) analysis, preparative gas chromatography was applied to separate and concentrate this biologically active compound. Analysis by liquid chromatography quadrupole time of flight mass spectrometry (LC–QTOF) confirmed the unidentified compound to be a compound with the formula of C 15 H 24 and together with GC–MS, 1 H and 13 C NMR analysis sesquisabinene B was identified as the unidentified compound in the extract. GC–SSR was then used to finally confirm the biological activity of sesquisabinene B isolated from the carrot leaf extract via preparative GC.
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| 119. |
- Rahmani, Rizan, et al.
(författare)
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SPME collection and GC-MS analysis of volatiles emitted during the attack of male Polygraphus poligraphus (Coleoptera, Curcolionidae) on Norway spruce
- 2015
-
Ingår i: Zeitschrift für Naturforschung C - A Journal of Biosciences. - : Walter de Gruyter GmbH. - 0939-5075 .- 1865-7125. ; 70:9-10, s. 265-273
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Tidskriftsartikel (refereegranskat)abstract
- Tree mortality caused by bark beetles has increased in recent decades in both Europe and North America. In a large recent outbreak in central Sweden the bark beetle Polygraphus poligraphus was often found together with the spruce bark beetle Ips typographus in killed trees. To increase the understanding of the aggregation behavior of P. poligraphus we used solid phase microextraction (SPME) to collect volatile organic compounds (VOCs) released from single P. poligraphus males, with and without added females, colonizing Norway spruce stem sections and analyzed the sampled compounds by combined gas chromatography and mass spectrometry (GC-MS). High amounts of terpinen-4-ol, a substance found in the hindguts of P. poligraphus males in earlier studies, were released by colonizing males. The emission of both enantiomers of terpinen-4-ol was monitored by GC-MS over time as the males aged in the absence and presence of females. Single males emitted (R)-(-)-terpinen-4-ol for up to 60 days in high enantiomeric purity but the enantiomeric excess (ee) varied between males, and also for the same individual, over time from 96.3% to 99.3% ee. In the presence of females, males also emitted terpinen-4-ol for up to 50 days but now in lower amounts and with lower enantiomeric purity varying from 67.7% ee to 99.3% ee. Small quantities of other volatile compounds were emitted from the colonizing beetles including cis-and trans-4-thujanol, both of which were previously shown to be present in the hindguts of males. In earlier studies frontalin was found to attract P. poligraphus, but in our study it was not identified among emitted compounds from colonizing beetles.
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| 120. |
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