Mixture Of Stereoisomers Research Articles

One-Pot Synthesis of 2,3,4,4a,10,10a-Hexahydro-1H-phenoxazines

A procedure has been proposed for the synthesis of 2,3,4,4a,10,10a-hexahydro-1H-phenoxazines by reductive cyclization of 2-(2-nitrophenoxy)cyclohexan-1-ones over palladium catalysts under mild conditions (ethanol, 318 K, pH 2 = 0.1 MPa). The product structure and ratio were determined by 1H and 13C NMR spectra, X-ray analysis, and GC/MS data. The reductive cyclization of 2-(2-nitrophenoxy)cyclohexan-1-one and 2-(4-methyl-2-nitrophenoxy)cyclohexan-1-one has been shown to produce 2,3,4,4a,10,10a-hexahydro-1H-phenoxazine and its 8-methyl analog as mixtures of stereoisomers with trans and cis-junction of the cyclo-hexane and morpholine rings at ratios of 1:3 and 3:1, respectively.

SMAX1/SMXL2 regulate root and root hair development downstream of KAI2-mediated signalling in Arabidopsis.

Karrikins are smoke-derived compounds presumed to mimic endogenous signalling molecules (KAI2-ligand, KL), whose signalling pathway is closely related to that of strigolactones (SLs), important regulators of plant development. Both karrikins/KLs and SLs are perceived by closely related α/β hydrolase receptors (KAI2 and D14 respectively), and signalling through both receptors requires the F-box protein MAX2. Furthermore, both pathways trigger proteasome-mediated degradation of related SMAX1-LIKE (SMXL) proteins, to influence development. It has previously been suggested in multiple studies that SLs are important regulators of root and root hair development in Arabidopsis, but these conclusions are based on phenotypes observed in the non-specific max2 mutants and by use of racemic-GR24, a mixture of stereoisomers that activates both D14 and KAI2 signalling pathways. Here, we demonstrate that the majority of the effects on Arabidopsis root development previously attributed to SL signalling are actually mediated by the KAI2 signalling pathway. Using mutants defective in SL or KL synthesis and/or perception, we show that KAI2-mediated signalling alone regulates root hair density and root hair length as well as root skewing, straightness and diameter, while both KAI2 and D14 pathways regulate lateral root density and epidermal cell length. We test the key hypothesis that KAI2 signals by a non-canonical receptor-target mechanism in the context of root development. Our results provide no evidence for this, and we instead show that all effects of KAI2 in the root can be explained by canonical SMAX1/SMXL2 activity. However, we do find evidence for non-canonical GR24 ligand-receptor interactions in D14/KAI2-mediated root hair development. Overall, our results demonstrate that the KAI2 signalling pathway is an important new regulator of root hair and root development in Arabidopsis and lay an important basis for research into a molecular understanding of how very similar and partially overlapping hormone signalling pathways regulate different phenotypic outputs.

Scientific Opinion on Flavouring Group Evaluation 5, Revision 3 (FGE.05Rev3): Branched‐ and straight‐chain unsaturated aldehydes, dienals, unsaturated and saturated carboxylic acids and related esters with saturated and unsaturated aliphatic alcohols and a phenylacetic acid related ester from chemical groups 1, 2, 3, 5 and 15

The EFSA Panel on Food Additives and Flavourings (FAF) was requested to evaluate 54 flavouring substances attributed to the Flavouring Group Evaluation 05 (FGE.05), using the Procedure as referred to in the Commission Regulation (EC) No 1565/2000. This Revision 3 includes 17 additional substances which have been cleared with respect to genotoxicity in FGE.200Rev1 ([FL‐no: 02.192, 02.231, 05.072, 05.144, 05.184, 05.189, 05.190, 05.191, 05.195, 09.247, 09.400, 09.866, 09.948]) and in FGE.203Rev2 ([FL‐no: 05.081, 05.186, 05.194, 05.196]). The substances were evaluated through a stepwise approach that integrates information on the structure–activity relationships, intake from current uses, toxicological threshold of concern (TTC), and available data on metabolism and toxicity. The Panel concluded that none of the 54 substances gives rise to safety concern at their levels of dietary intake, estimated on the basis of the ‘Maximised Survey‐derived Daily Intake’ (MSDI) approach. Besides the safety assessment of the flavouring substances, the specifications for the materials of commerce have also been considered and found adequate, except for 10 substances ([FL‐no: 08.072, 08.083, 08.101, 08.119, 08.120, 09.181, 09.329, 09.335, 09.379 and 09.637]) for which quantitative figures on the composition of stereoisomeric mixtures are missing and for [FL‐no: 09.578] complete specifications should be provided. Normal and maximum use levels were not available for [FL‐no: 08.072, 08.083, 08.101, 08.119, 08.120, 09.287, 09.326 and 09.578]. Except for flavouring substances [FL‐no: 05.072, 05.081, 05.186, 05.194, 05.196, 09.934 and 09.942], more reliable intake data should be requested for all the 46 flavouring substances, for which use levels were submitted, as their modified Theoretical Added Maximum Daily Intake (mTAMDI) exposure estimates are above the threshold of concern for structural classes I and II. This would include more reliable intake data and then, if required, additional toxicological data.

Scientific Opinion on Flavouring Group Evaluation 70, Revision 1 (FGE.70Rev1): consideration of aliphatic, linear, α,β‐unsaturated, di‐ and trienals and related alcohols, acids and esters evaluated by JECFA (61st‐68th‐69th meeting)

The EFSA Panel on Food Additives and Flavourings was requested to evaluate 29 flavouring substances attributed to the Flavouring Group Evaluation 70 (FGE.70), using the Procedure in Commission Regulation (EC) No 1565/2000. Seven substances have already been considered in FGE.70 [FL‐no: 08.085, 09.194, 09.260, 09.300, 09.371, 09.639 and 09.840]. The remaining 22 substances [FL‐no: 02.049, 05.058, 05.111, 05.120, 05.172, 09.947, 02.139, 02.153, 02.162, 02.188, 05.057, 05.064, 05.071, 05.084, 05.101, 05.108, 05.125, 05.127, 05.140, 05.141, 05.173 and 09.573] have been cleared with respect to genotoxicity in FGE.200Rev1 and FGE.203Rev2 and are considered in this revision. The substances were evaluated through a stepwise approach that integrates information on the structure–activity relationships, intake from current uses, toxicological threshold of concern (TTC), and available data on metabolism and toxicity. The Panel concluded that none of the 29 substances gives rise to safety concerns at their levels of dietary intake, estimated on the basis of the ‘Maximised Survey‐derived Daily Intake’ (MSDI) approach. Besides the safety assessment of the flavouring substances, the specifications for the materials of commerce have also been considered and found adequate, except for [FL‐no: 09.371 and 09.840]. For these two substances, data on the composition of the stereoisomeric mixture should be requested. Data on the identity and contents of secondary components should be requested for [FL no: 09.260]. Normal and maximum use levels should be provided for seven flavouring substances [FL‐no: 08.085, 09.194, 09.260, 09.300, 09.371, 09.639 and 09.840]. For six flavouring substances [FL‐no: 05.057, 05.058, 05.111, 05.120, 05.172 and 09.947] further information is required based on the comparison of the ‘modified Theoretical Added Maximum Daily Intakes’ (mTAMDIs) with the TTCs. This includes more reliable data on use and use levels and then, if required, additional toxicological data.

Molecular Docking and Preclinical Study of Five-Membered S,S-Palladaheterocycle as Hepatoprotective Agent.

Purpose: In order to investigate mechanisms underlying the hepatoprotective action of S,Spalladaheterocycle, inhibition of cytochromes P450 has been modeled by molecular docking of four palladaheterocycle stereoisomers to the active sites of an enzymatic oxidase system. To obtain a deeper insight into biochemical aspects providing a basis for the therapeutic effects of five-membered palladacycles (as mixture of stereoisomers), a number of preclinical trials has been conducted Methods: 2D and 3D structures of palladaheterocycle stereoisomers were obtained via converting into SDF files by means of software MarvinSketch. Binding of palladaheterocycle at the active sites of cytochromes P450 2E1 and P450 2C9 has been studied by molecular docking using LeadIT 2.3.2. Hepatoprotective activity of palladaheterocycle at 2.5, 25 and 250 mg/kg doses has been studied based on a model of acute intoxication by CCl4 using in vivo methods. Results: By molecular docking it was identify amino acid fragments responsible for binding with palladacyclic isomers. The tested compound is comparable, in terms of its activity to the hepatoprotective drug SAM according to the in vivo and in vitro experiments such as animal survival data, the efficiency of correction of the cytolytic syndrome, the liver excretory function, carbohydrate, protein and lipid metabolism, and the correction efficiency of the liver antitoxic function (the latter has been determined based on the results of a hexobarbital control experiment). Conclusion: Taking into account results obtained in vivo, in vitro and in silico, it can be concluded that the five-membered S,S-palladaheterocycle effectively protect the liver against acute damage caused by CCl4 , via activation of catalase and glucuronyltransferase, as well as via inhibition of the oxidative stress enzymes.

Rate Coefficients for the Gas-Phase Reaction of ( E)- and ( Z)-CF3CF═CFCF3 with the OH Radical and Cl-Atom.

The rate coefficients, k, for the gas-phase reaction of the OH radical and Cl-atom with ( E)- and ( Z)-CF3CF═CFCF3 were measured using a relative rate technique over a range of temperature (240-375 K) and bath gas pressure (50-630 Torr, He). The obtained rate coefficients were found to be independent of pressure under these conditions. The obtained rate coefficients for the reaction of Cl-atom with ( E)- and ( Z)-CF3CF═CFCF3 at 296 K were k1(296 K) = (7.23 ± 0.3) × 10-12 cm3 molecule-1 s-1 and k2(296 K) = (6.70 ± 0.3) × 10-12 cm3 molecule-1 s-1, respectively, with the temperature dependence described by the Arrhenius expressions: k1( T) = (3.47 ± 0.35) × 10-12 exp[(210 ± 25)/ T] cm3 molecule-1 s-1 and k2( T) = (3.37 ± 0.35) × 10-12 exp[(199 ± 25)/ T] cm3 molecule-1 s-1. The rate coefficients for the OH radical reaction with ( E)- and ( Z)-CF3CF═CFCF3 were found to be k3(296-375 K) = (4.34 ± 0.45) × 10-13 cm3 molecule-1 s-1 and k4(296-375 K) = (3.30 ± 0.35) × 10-13 cm3 molecule-1 s-1, respectively. The quoted rate coefficient uncertainties are 2σ (95% confidence level) and include estimated systematic errors. The rate coefficients for the reaction of OH with a mixture of the two stereoisomers were determined using a pulsed laser photolysis-laser-induced fluorescence (PLP-LIF) technique for comparison with previous kinetic measurements using stereoisomer mixtures. The effective rate coefficient for the 0.7/0.3 ( E)/( Z) stereoisomer sample was found to be nearly independent of temperature over the range 222-375 K with a value of (4.47 ± 0.36) × 10-13 cm3 molecule-1 s-1. The atmospheric lifetimes for ( E)- and ( Z)-CF3CF═CFCF3 due to OH-reactive loss are estimated to be 25 and 35 days, respectively. The lifetime-corrected radiative efficiencies (W m-2 ppb-1) and 100 year time horizon global warming potentials derived in this work are 0.05 and 1.2 for ( E)-CF3CF═CFCF3 and 0.13 and 4.1 for ( Z)-CF3CF═CFCF3. The photochemical ozone creation potentials for ( E)- and ( Z)-CF3CF═CFCF3 are estimated to be 2.5 and 2.1, respectively.

Analysis by RP-HPLC and Purification by RP-SPE of the C-Tetra(p-hydroxyphenyl)resorcinolarene Crown and Chair Stereoisomers.

A method for the separation of stereoisomer mixture of the octol C-tetra(p-hydroxyphenyl)calix[4]resorcinarene that was obtained by an acid cyclocondensation reaction between resorcinol and benzaldehyde is reported in this paper. A crude product from octol formation reaction was analyzed by reverse-phase high-performance liquid chromatography (RP-HPLC), and two well-resolved signals corresponding to the crown and chair isomers were found. A reverse phase in solid-phase extraction (RP-SPE) protocol allowed the separation of the two stereoisomers with high purity of each isomer. Finally, the crude and purified stereoisomers were characterized by using FT-IR, 1H-NMR, and 13C-NMR techniques, confirming the chemical identity of the two isomers and the efficiency in the separation process.

Stereoselective Synthesis of Vinylboronates by Rh‐Catalyzed Borylation of Stereoisomeric Mixtures

Summary of main observation and conclusionThe stereoselective preparation of vinylboronates via rhodium‐catalyzed borylation of E/Z mixtures of vinyl actetates is described, and this method was also extended to synthesis of vinyldiboronates. These transformations feature high functional group compatibility and mild reaction conditions. Control experiments support a mechanism that involved a Rh‐catalyzed borylation‐isomerization sequence. The isomerization of (Z)‐vinylboronates to (E)‐isomers was also demonstrated.

Aza‐Henry Reaction with Nitrones, an Under‐Explored Transformation

Nitromethylation of nitrones occurred efficiently in CH3NO2 in the presence of tetramethylammonium fluoride or triazabicyclodecene as promoters. The obtained adducts might be conveniently transformed into vicinal diamines. The process was extended to nitroethane and nitropropane affording mixtures of syn and anti stereoisomers with low diastereoselectivity.

Computational analysis of intermolecular Diels–Alder reactions of methyl 2-(methyl(phenyl)carbamoyl)acrylate with cyclic dienes

abstract The synthetic method recently established by Spivey and co-workers describes the intermolecular Diels–Alder reactions between α-aminoacrylate(s) dienophiles and cyclic dienes. These reactions gave stereoisomeric mixtures of endo and exo products. A computational study was undertaken in an effort to identify a method of analysis that would yield results similar to those of the synthetic experiments. Starting materials, transition state estimates, and products were subjected to conformational analysis (MMFF) using the Spartan molecular modeling program (Spartan’16). The low-energy conformations produced for each molecule were subjected to density functional theory calculations at the B3LYP 6-31+G(d) level of theory using the Gaussian09 program. The results of this computational study are described. These calculations provide information about molecular geometry and energy values of the reaction that will be compared with the experimental results in an effort to verify whether computational analysis supports the stereoselectivity observed in physical experimentation.

Cooperative Kinetic Model to Describe Crystallization in Solid Solution Forming Systems

The crystallization kinetics was determined for mixtures of stereoisomers which revealed solid–solution phase behavior in the crystalline phase. Two model systems of pharmaceutically active compoun...

Solid-Phase Conversion of Four Stereoisomers into a Single Enantiomer.

Viedma ripening is an emerging method for the solid‐phase deracemization of mixtures of enantiomers. Up to now, the scope of the method has remained limited to molecules with a single stereocenter. We show here that this method can be extended to obtain a single enantiomer from a mixture of stereoisomers with two different stereocenters. In addition, we show that by using tailor‐made chiral additives, the conversion time can be reduced by a factor of 100.

Solid‐Phase Conversion of Four Stereoisomers into a Single Enantiomer

AbstractViedma ripening is an emerging method for the solid‐phase deracemization of mixtures of enantiomers. Up to now, the scope of the method has remained limited to molecules with a single stereocenter. We show here that this method can be extended to obtain a single enantiomer from a mixture of stereoisomers with two different stereocenters. In addition, we show that by using tailor‐made chiral additives, the conversion time can be reduced by a factor of 100.

ω-Hydroxylation of α-tocopheryl quinone reveals a dual function for cytochrome P450-4F2 in vitamin E metabolism.

α-Tocopherol (α-TOH) is the primary lipophilic radical trapping antioxidant in human tissues. Oxidative catabolism of α-tocopherol (αTOH) is initiated by ω-hydroxylation of the terminal carbon (C-13) of the isoprenoid sidechain followed by oxidative transformations that sequentially truncate the chain to yield the 2,5,7,8-tetramethyl(3'carboxyethyl)-6-hydroxychroman (α-CEHC). After conjugation to glucuronic acid, 3'-carboxyethyl-6-hydroxychroman glucuronide is excreted in urine. We report here that the same enzyme that accomplishes this task, the cytochrome P450 monooxygenase CYP-4F2, can also ω-hydroxylate the terminal carbon of α-tocopheryl quinone. A standard sample of ω-OH-α-tocopheryl quinone (ω-OH-α-TQ) was synthesized as a mixture of stereoisomers by allylic oxidation of α-tocotrienol using SeO2 followed by double-bond reduction and oxidation to the quinone. After incubating human liver microsomes or insect cell microsomes expressing only recombinant human CYP-4F2, cytochrome b5, and NADPH P450 reductase with d6-α-tocopheryl quinone (d6-αTQ), we showed that the ω-hydroxylated (13-OH) d6-α-TQ was produced. We further identified the production of the terminal carboxylic acid d6-13-COOH-αTQ. The ramifications of this discovery to the understanding of tocopherol utilization and metabolism, including the quantitative importance of the αTQ-ω-hydroxylase pathway in humans, are discussed.

Impact of 2-Ethylhexyl Stereoisomers on the Electrical Performance of Single-Crystal Field-Effect Transistors.

Many organic semiconductors (OSCs) inherit chiral alkyl chains, which ensure the desirable high solubility for solution-processing but may also lead to disorder, inhomogeneous film-formation, as well as interfacial defects due to the presence of mixtures of stereoisomers or diastereomers, which impair their peak performance. Here, single-crystal field-effect transistors (SCFETs) of a diketopyrrolopyrrole-based organic semiconductor with chiral 2-ethylhexyl substituents by sublimation in air and organic ribbon mask method are fabricated. Devices of the mesomer (R/S), both enantiomers (R/R, S/S), as well as mixtures of these three stereoisomers measured under ambient conditions exhibit all appreciable p-channel charge carrier mobilities of > 0.1 cm2 V-1 s-1 despite different packing arrangement in the R/S, R/R (or S/S), and racemate crystal structures. These results suggest a surprising tolerance for isomeric impurities. The highest literature-reported p-channel mobility so far for a diketopyrrolopyrrole-based OSC of 3.4 cm2 V-1 s-1 (Ion /Ioff of 1 × 106 ) is, however, only obtained for the pure R/S mesomer, illustrating the inherent potential of stereochemical purity. These results on SCFETs are further substantiated by studies on organic thin-film transistors (OTFTs) of pure and mixed thin films of the different stereoisomers.

Methinylogation Approach in Chiral Pharmacophore Design: from Alkynyl- to Allenyl-carbinol Warheads against Tumor Cells.

Extension of a structure-activity relationship study of the antitumor cytotoxicity of lipidic dialkynylcarbinols (DACs) is envisaged by formal methinylogation of one of the ethyndiyl moieties of the DAC warhead into the corresponding allenylalkynylcarbinol (AllAC) counterpart. External AllACs were directly obtained by methinylation of the parent DACs with formaldehyde in either the racemic or scalemic series. Isomers containing external progargyl and propynyl motifs were also prepared. Internal AllACs were obtained as racemic statistical mixtures of stereoisomers in two steps from the key C5 -DAC rac-TIPS-C≡C-CH(OH)-C≡CH and aldehydes. Kinetic resolution of the (S)-C5 -DAC in 97 % ee and (R)-C5 -DAC in 99 % ee was achieved by sequential lipase-mediated acetylation/hydrolysis using the Candida antartica lipase (Novozyme 435). The four internal AllAC stereoisomers were prepared by asymmetric methinylation with (R)- or (S)-diphenylprolinol as chiral auxiliary. Cytotoxicity assays on HCT116 cancer cells showed that the most active (eutomeric) external or internal AllAC exhibits an S configuration, a fatty chain length of n=12, and a 50 % inhibitory concentration IC50 ≈1.0 μm.

Stereoselective bioactivity, acute toxicity and dissipation in typical paddy soils of the chiral fungicide propiconazole

Propiconazole is a widely used systemic agricultural triazole fungicide with two chiral centers. In the present study, systemic assessments of propiconazole stereoisomers are reported for the first time, including absolute configuration, stereoselective bioactivity toward pathogens (Ustilaginoidea virens, Magnaporthe oryzae, Fusarium moniliforme, Thanatephorus cucumeris, and Rhizoctonia solani), and stereoselective acute toxicity toward aquatic organisms (Scenedesmus obliquus, and Daphnia magna). Moreover, the stereoselective dissipation of propiconazole in three types of paddy soil under laboratory-controlled conditions (aerobic, anaerobic and sterile) was investigated. The degree of bioactivity and acute toxicity of the propiconazole stereoisomers differed depending on the type of target pathogens and non-target organisms. There were 2.43–23.47 and 1.48–2.13 fold differences between the best and worst stereoisomer in bioactivity and toxicity, respectively. Under aerobic conditions, (2S,4S)-propiconazole and (2S,4R)-propiconazole were preferentially degraded in the three types of soils. However, no significant stereoselectivity was observed under anaerobic and sterile conditions. Propiconazole was configurationally stable throughout the study. In comprehensive consideration of bioactivity, toxicity and environmental behavior, using stereoisomer mixture rather than pure stereoisomer may help to control more species of disease in practical application, and the stereoselectivity should be taken into consideration in risk assessment.

One-Dimensional 13C NMR Is a Simple and Highly Quantitative Method for Enantiodiscrimination.

The discrimination of enantiomers of mandelonitrile by means of 1D 13C NMR and with the aid of the chiral solvating agent (S)-(+)-1-(9-anthryl)-2,2,2-trifluoroethanol (TFAE) is presented. 1H NMR fails for this specific compound because proton signals either overlap with the signals of the chiral solvating agent or do not show separation between the (S)-enantiomer and the (R)-enantiomer. The 13C NMR method is validated by preparing artificial mixtures of the (R)-enantiomer and the racemate, and it is shown that with only 4 mg of mandelonitrile a detection limit of the minor enantiomer of 0.5% is obtained, corresponding to an enantiomeric excess value of 99%. Furthermore, the method shows high linearity, and has a small relative standard deviation of only 0.3% for the minor enantiomer when the relative abundance of this enantiomer is 20%. Therefore, the 13C NMR method is highly suitable for quantitative enantiodiscrimination. It is discussed that 13C NMR is preferred over 1H NMR in many situations, not only in molecules with more than one chiral center, resulting in complex mixtures of many stereoisomers, but also in the case of molecules with overlapping multiplets in the 1H NMR spectrum, and in the case of molecules with many quaternary carbon atoms, and therefore less abundant protons.

Endo/Exo Reactivity Ratios in Living Vinyl Addition Polymerization of Substituted Norbornenes

AbstractSubstituted norbornenes may be enchained by vinyl addition polymerization (VAP), through the norbornene double bond. Such monomers are generally prepared by Diels–Alder cycloaddition of cyclopentadiene and the corresponding olefin, which leads to a mixture of endo and exo stereoisomers with potentially very different reactivity, but these differences have not previously been quantified (e.g., as copolymerization reactivity ratios rendo and rexo). A living Pd‐based VAP initiator is employed and the consumption of endo and exo monomers to high conversions is measured to determine rendo and rexo; since the polymerization is living, the products are gradient copolymers. For norbornenes bearing n‐butyl, norbornyl, or methylhexafluoroisopropanol substituents, rexo = 1–4, and rexo rendo = 0.2–0.8, indicating only moderate deviations from ideal copolymerization behavior. By contrast, for norbornene bearing a pentamethyldisiloxane substituent, rendo is indistinguishable from zero, indicating that the endo isomer is effectively incapable of homopropagation. However, since the polymerization is living, propagation resumes (and chain extension proceeds) when additional exo monomer is charged.

Aggregation Pheromone of the Bearded Weevil, Rhinostomus barbirostris (Coleoptera: Curculionidae): Identification, Synthesis, Absolute Configuration and Bioactivity.

The bearded weevil, Rhinostomus barbirostris (Coleoptera: Curculionidae: Dryophthorinae), attacks coconut trees, oil palms and other species of Arecaceae. Besides direct damage, R. barbirostris may be a vector of diseases in coconut and oil palms, such as stem bleeding (resinosis) and red ring disease. Currently, the only method to control this weevil is by visual observation of damage and removal of infected plants. Semiochemical-based trapping could improve the effectiveness of monitoring and management of R. barbirostris. In comparisons of volatiles released by R. barbirostris males and females by gas chromatography (GC) two male-specific compounds were observed. GC-mass spectrometry (MS) and GC-Fourier transform-infrared (FTIR) analyses of the natural compounds suggested these were diastereoisomers of 5-hydroxy-4-methylheptan-3-one, also known as sitophilure, a pheromone component of other dryophthorine species. Synthesis of the mixture of all four stereoisomers of sitophilure was performed in two steps, and the chemical structures were confirmed by comparing GC retention times and MS and FTIR spectra of natural and synthetic compounds. The absolute configurations of the two male-specific compounds were elucidated by enantioselective GC; the major component was the (4S,5R)-isomer, and the minor component (4S,5S)-sitophilure. In analyses by GC-electroantennography (EAG) the antennae of male and female R. barbirostris only responded to the (4S,5R)-isomer of the synthetic sitophilure. The stereoisomeric mixture of sitophilure was attractive to both sexes of R. barbirostris in laboratory experiments in the presence of sugar cane volatiles, and a similar result was obtained in a preliminary field trapping test.