Resolution of Pheromonal Epoxydienes by Chiral HPLC, Stereochemistry of Separated Enantiomers, and Their Field Evaluation

Resolution of insect pheromonal cis-epoxydiene racemates derived from (Z,Z,Z)-3,6,9-trienes with a C₁₈–C₂₃ chain was examined utilizing chiral HPLC columns, and the result showed that a Chiralpak AS column was suitable to separate enantiomers of the 3,4-epoxides, and a Chiralpak AD column was indispensable for the resolution of the racemic 6,7- and 9,10-epoxides. The absolute configuration of the enantiomers of the 3,4- and 9,10-epoxides separated by HPLC was studied after methanolysis of their epoxy rings. Examination of the ¹H NMR data from esters of the methoxyalcohols produced by a modified Mosher's method with (S)- and (R)--methoxy--(trifluoromethyl)phenylacetic acid indicated that the dextrorotatory parent epoxides with a shorter R _t were 3S,4R and 9S,10R isomers and the levorotatory enantiomers having a longer R _t possessed 3R,4S and 9R,10S configuration. Field tests with both enantiomers of (Z,Z)-6,9-cis-3,4-epoxynonadecadiene separated by HPLC with the chiral column revealed new specific attraction of geometrid forest defoliators, Pachyerannis obliquaria, to the 3R,4S isomer and Zethenia albonotaria nesiotis to the 3S,4R isomer.     

Responses of the Aphids Phorodon humuli and Rhopalosiphum padi to Sex Pheromone Stereochemistry in the Field

Gynoparous female and male damson-hop aphids, Phorodon humuli (Schrank), were caught in the field by water traps that were releasing the sex pheromone of this species, (1RS,4aR,7S,7aS)-nepetalactol. No behavioral activity was elicited by (4aS,7S,7aR)-nepetalactone, the major sex pheromone component of other aphid species such as Megoura viciae Buckton, even though olfactory cells were found in the secondary rhinaria on the third antennal segment of P. humuli that responded strongly to this compound. Gynoparous female P. humuli in the field responded less strongly to (1R,4aS,7S,7aR)-nepetalactol, the sex pheromone of the bird cherry-oat aphid, Rhopalosiphum padi (L.), than they did to the (4aR,7S,7aS)-nepetalactols, but males responded only to the latter. The (4aR,7S,7aS)-nepetalactone showed no electrophysiological activity so was not used in field trials. Releasing either the (4aS,7S,7aR)-nepetalactone or the (1R,4aS,7S,7aR)-nepetalactol with the (4aR,7S,7aS)-nepetalactols did not inhibit the response of P. humuli gynoparous females and males to the latter. Males of R. padi responded as strongly to the (4aR,7S,7aS)-nepetalactols as they did to (1R,4aS,7S,7aR)-nepetalactol. Males of P. humuli and R. padi responded positively to an increased concentration of the (4aR,7S,7aS)-nepetalactols released from two vials compared with that from a single vial, as did P. humuli (in one of two experiments) and R. padi to the (1RS,4aR,7S,7aS)- and (1R,4aS,7S,7aR)-nepetalactols when released together.     

酶法手性化合物的合成与拆分

综述了酶法手性化合物合成与拆分的最新研究进展,主要对酶法制备手性物质的应用、提高对映选择性的方法进行了介绍。     

Identification of Chiral Sex Pheromone Secreted by Giant Geometrid Moth, Biston robustum Butler

Biston robustum Butler, a polyphagous defoliator, multiplied on Hachijo-jima Island in 1997–1998. Based on GC-MS data of authentic standards, an analysis of a pheromone gland extract of the females indicated that it included (Z,Z)-6,9–nonadecadiene (I), (Z,Z,Z)-3,6,9–nonadecatriene (II), cis-(Z)-6,7–epoxy-9–nonadecene (III), and cis-(Z,Z)-6,7–epoxy-3,9–nonadecadiene (IV) in a ratio of 13 : 2 : 70 : 15. The structure of III was confirmed by a GC-MS analysis of another extract treated with dimethyl disulfide (DMDS). This epoxymonoene was successfully converted into the corresponding DMDS adduct that showed diagnostic ions fragmented at an epoxy ring and at thiomethoxy groups reflecting the position of an original double bond. Furthermore, the 6S,7R configuration was assigned for the epoxy ring of III by chiral HPLC analysis. Field examination of synthetic lures revealed that the two epoxy compounds (III and IV) with the 6S,7R configuration were essential components and that the two unsaturated hydrocarbons (I and II) showed a synergistic effect on male attraction.     

Subtleties in Perception and Discrimination by Cabbage Looper Moths, Trichoplusia ni, of the two 14-carbon Acetate Sex Pheromone Components

Three compounds that are emitted by virgin female cabbage looper moths, Trichoplusia ni, (Z)-7-dodecenyl acetate (Z7–12:Ac), (Z)-7-tetradecenyl acetate (Z7–14:Ac), and (Z)-9-tetradecenyl acetate (Z9–14:Ac), are detected by antennal olfactory receptor neurons specialized to detect sex pheromone components. The principal evidence signifying that either or both of Z7–14:Ac and Z9–14:Ac have an effect on male behavior comes from an observed reduction in the numbers of males trapped by Z7–12:Ac paired with a six-component mixture. The evidence conforms to a hypothesis that either or both of these compounds are the basis for discrimination between the two mixtures. However, scant evidence for this hypothesis was obtained in paired-source laboratory wind-tunnel assays, even at airborne concentrations of Z7–14:Ac and Z9–14:Ac that ranged up to 1000× that emitted by a female. Furthermore, there was little evidence from single-source laboratory or field trap assays confirming that Z7–14:Ac and Z9–14:Ac at or above natural stimulus strengths modify the moth's perception of Z7–12:Ac. The data suggest that discrimination of small mixture differences may not be resolvable within the confines of a wind tunnel.     

Synthesis and Characterization of 2,13- and 3,13-Octadecadienals for the Identification of the Sex Pheromone Secreted by a Clearwing Moth

In addition to 2,13- and 3,13-octadecadien-1-ols and their acetates, aldehyde analogs have been identified from lepidopteran species in the family Sesiidae. To establish a reliable analytical method for determining the positions and configurations of the two double bonds in natural pheromone components, all geometric isomers of the 2,13- and 3,13-octadecadienals were synthesized by Dess-Martin oxidation of the corresponding alcohols with limited isomerization of the double bond at the 2- or 3-position. GC-MS analysis of these aldehydes showed isomerization of (Z)-2-, (Z)-3-, and (E)-3-double bonds to an (E)-2-double bond, even with a cool on-column injection. In contrast, HPLC analysis with an ODS column was accomplished without isomerization. The geometric isomers of each dienal eluted in the order ZZ → EZ → ZE → EE. The conjugated 2,13-dienals were detectable in nanogram amounts with a UV detector at 235 nm. Whereas the detection of 3,13-dienals was difficult because of the lack of a chromophore, a highly sensitive analysis was achieved after derivatization with 2,4-dinitrophenylhydrazine. LC-MS with atmospheric pressure chemical ionization showed a strong [M-1]^- at m/z 443 for the derivatives. Based on these analytical data, a pheromone extract of a sesiid moth, Macroscelesia japona, was examined by HPLC and LC-MS, and it was confirmed that the octadecadienal tentatively identified by a previous GC-MS analysis did indeed have the 2E,13Z configuration. Furthermore, field evaluation of four synthetic geometric isomers of the 2,13-dienal revealed specific attraction to a lure with the (2E,13Z)-isomer as a main component.     

Cuticular Hydrocarbons as Sex Pheromone of the Bee <Emphasis Type="Italic">Colletes cunicularius</Emphasis> and the Key to its Mimicry by the Sexually Deceptive Orchid, <Emphasis Type="Italic">Ophrys exaltata</Emphasis>

Male Colletes cunicularius bees pollinate the orchid, Ophrys exaltata, after being sexually deceived by the orchid’s odor-mimicry of the female bee’s sex pheromone. We detected biologically active volatiles of C. cunicularius by using gas chromatographic–electroantennographic detection (GC-EAD) with simultaneous flame ionization detection. After identification of the target compounds by coupled gas chromatography–mass spectrometry (GC-MS), we performed behavioral tests using synthetic blends of the active components. We detected 22 EAD active compounds in cuticular extracts of C. cunicularius females. Blends of straight chain, odd-numbered alkanes and (Z)-7-alkenes with 21–29 carbon atoms constituted the major biologically active compounds. Alkenes were the key compounds releasing mating behavior, especially those with (Z)-7 unsaturation. Comparison of patterns of bee volatiles with those of O. exaltata subsp. archipelagi revealed that all EAD-active compounds were also found in extracts of orchid labella. Previous studies of the mating behavior in C. cunicularius showed linalool to be an important attractant for patrolling males. We confirmed this with synthetic linalool but found that it rarely elicited copulatory behavior, in accordance with previous studies. A blend of active cuticular compounds with linalool elicited both attraction and copulation behavior in patrolling males. Thus, linalool appears to function as a long-range attractant, whereas cuticular hydrocarbons are necessary for inducing short-range mating behavior.