Geometric Isomers Of Methyl Research Articles

Field Trapping of the Invasive Brown Marmorated Stink Bug, Halyomorpha halys, with Geometric Isomers of Methyl 2,4,6-Decatrienoate

The brown marmorated stink bug, Halyomorpha halys (Stål), is a polyphagous pest indigenous to northeastern Asia where it damages various trees, vegetables, and leguminous crops. The bug was recently introduced into the U.S. and could potentially become a pest. In its native range, H. halys was reportedly attracted to the aggregation pheromone of the brown-winged green bug, Plautia stali, methyl (2 E,4 E,6 Z)-decatrienoate. We also observed that traps baited with this compound are attractive to H. halys. We additionally found that methyl (2 E,4 E,6 Z)-decatrienoate (as well as other isomeric methyl 2,4,6-decatrienoates) exposed to daylight in solutions and/or on dispensers used for field trapping can readily isomerize to form complex mixtures of isomers, thus causing a concern about lure stability and longevity. However, our studies demonstrated that preventing isomerization of methyl (2 E,4 E,6 Z)-decatrienoate in dispensers was not essential for field trapping of H. halys males, females, and nymphs. We also present evidence that traps baited with methyl (2 Z,4 E,6 Z)-decatrienoate and methyl (2 E,4 Z,6 Z)-decatrienoate (pheromone of Thyanta spp. pentatomids), as well as the mixtures of geometric isomers, attract H. halys. The ZEZ isomer, unknown in nature, as well as the EEZ isomer, elicited electrophysiological responses from antennae of H. halys males. The field data suggest that the presence of the EEZ but not ZEZ isomer in the lure is essential for attraction of H. halys, and that other isomers are not antagonistic and may even be needed for maximum attraction. Because the pheromone of H. halys is unknown at present, lures containing methyl (2 E,4 E,6 Z)-decatrienoate without protection from daylight are suitable for monitoring populations of H. halys late in the season.

The geometric isomers of methyl-2,4,6-decatrienoate, including pheromones of at least two species of stink bugs

All eight geometric isomers of methyl 2,4,6-decatrienoate were synthesized from readily accessible starting materials by fully exploiting Wittig-type olefinations, and taking advantage of an easy separation of 2 E and 2 Z unsaturated esters. The aggregation pheromone of the brown-winged green bug, Plautia stali, methyl ( E, E, Z)-2,4,6-decatrienoate (also a cross-attractant for the brown marmorated stink bug, Halyomorpha halys), was expediently produced in two easy steps from ( E)-4,4-dimethoxy-2-butenal in 55% yield. The sex pheromone of the red-shouldered stink bug, Thyanta pallidovirens, methyl ( E, Z, Z)-2,4,6-decatrienoate, was conveniently synthesized from 2,4-octadiyn-1-ol in 32% yield using in situ manganese dioxide oxidation–Wittig condensation in a key step.

Determination of the (2E,4E)-Geometryof the 3,5-Dimethyl-2,4-diene System of Antibiotic 1233A by NMR Comparison with the Four Geometrical Isomers of Methyl 3,5-Dimethyl-2,4-heptadienoate

(2E,4E)-geometry was assigned to 1233A [(7R,2ʹR,3ʹR)-11-[3ʹ-(hydroxymethyl)-4ʹ-oxo-2ʹ-oxetanoyl]-3,5,7-trimethyl-2,4-undecadienoic acid (1a)], an inhibitor of cholesterol biosynthesis. Both the 1H- and 13C-NMR spectra of 1a and methyl ester 1b were compared with those of the four geometrical isomers of methyl 3,5-dimethyl-2,4-heptadienoate (2). NOE experiments on 1b revealed the presence of a remarkable NOE between the proton at C-2 and those of the C-17 methyl group. Similar NOE was also observed with (2E,4E)-2. This fact suggests the predominant existence of stable s-cis-rotamers at the single bond between C-3 and C-4 of 1b and of (2E,4E)-2. Some MM2 calculations were attempted to show the presence of two types of stable conformers in the case of the 3,5-dimethyl-2,4-dienoate system.

Stéréochimie De L'Électroréduction De Bromocyclopropanes. IV. Nouvel Exemple De L'Influence De La Composition De L'Électrolyte Sur La Stéréosélectivité De La Réaction

AbstractThe stereochemistry of the electroreduction of the two geometrical isomers of methyl 1‐bromocyclopropane 1,2‐dicarboxylate has been investigated:‐ for the trans isomer, electrolysis carried out in the presence of NH4+ ions give rise to a 90% retention ratio while 90% of inversion is attained when Bu4N+ cations are present.‐ preferential inversion of configuration always occurs for the reduction of the cis isomer and stereospecificity (i.e. 100% inversion) is achieved in the presence of Bu4N+ cations.These results are compared with those observed in the study of electroreduction of cis methyl 1‐bromo 2‐methoxymethyl cyclopropane 1,2‐dicarboxylate.

Synthesis and properties of Mono‐, Di‐ and trienoic fatty esters containing a 12,13 double bond

AbstractMethyl trans‐12‐octadecenoate‐9, 10‐d2 was obtained from methyl threo‐12, 13‐dihydroxy‐cis‐9‐octadecenoate by a sequence of reactions involving formation of an ethoxydioxolane, catalytic deuteration of the double bond, and conversion of the ethoxydioxolane group to an ethylenic bond. Methyl cis‐ and trans‐12‐octadecenoate‐15, 15, 16, 16‐d4 and methyl cis‐ and trans‐12‐octadecenoate‐9, 10, 15, 15, 16, 16‐d6 were obtained from the Wittig coupling of hexyl‐3, 3, 4, 4‐d4‐triphenylphosphonium bromide with methyl 12‐oxododecanoate and methyl 12‐oxododecanoate‐9, 10‐d2, respectively. The four geometrically isomeric methyl 12, 15‐octadecadienoates‐9, 10‐d2 were prepared by the Wittig reaction between cis‐ or trans‐3‐hexenyltriphenylphosphonium bromide and methyl 12‐oxododecanoate‐9,‐10‐d2 with butyl lithium in ethyl ether. The Wittig reaction between hexyl‐3, 3, 4, 4‐d4 ‐triphenylphosphonium bromide and methyl 12‐oxo‐cis‐ or trans‐9‐dodecenoate was used to prepare the four geometric isomers of methyl 9, 12‐octadecadienoate‐15, 15, 16, 16‐d4, whereas the same reaction between eis‐ or trans‐3‐hexenyltriphenyl‐phosphonium bromide and methyl 12‐oxo‐cis‐ or trans‐9‐dodecenoate afforded the eight geometrically isomeric methyl 9, 12, 15‐octadecatrienoates. In each case, the stereochemistry of the double bond formed in the Wittig reaction was controlled by choice of reaction conditions. Pairs of isomers formed during each synthesis were separated by partial silver resin chromatography. Physical constants presented include13C nuclear magnetic resonance chemical shifts, melting points, equivalent chain lengths and percentage trans by infrared spectroscopy.

Silver nitrate‐high performance liquid chromatography of fatty methyl esters

AbstractLong chain fatty methyl esters have been separated by high performance liquid chromatography on the basis of number, position, and geometric configuration of double bonds with a silver nitrate‐silicic acid column and benzene solvent. Saturated esters are eluted first, followed by methyl elaidate and then methyl oleate. Geometric isomers of methyl 9,12‐octadecadienoate and of methyl 9,15‐octadecadienoate are also well separated. Methyl linolenate is retained strongly on the column and its elution has not been observed, but thetrans, trans, trans andtrans, cis, trans isomers are separated.

Hydrogen sulfide adducts of methyltrans,trans‐ 9,11‐octadecadienoate

AbstractHydrogen sulfide was added to methyltrans, trans‐ 9,11‐octadecadienoate in benzene solution at 25 C with ultraviolet radiation. GC‐MS and GLC analysis of the reaction product showed the presence of methyl oleate, methyl stearate, geometric isomers of methyl 9,11‐octadecadienoate, methyl 9,12‐epoxy‐octadeca‐9, 11‐dienoate, an unknown compound with an apparent molecular weight of 306, methyl 8‐(2′,5′‐hexylthienyl) octanoate, an unidentified sul‐fur] containing C18 ester with an apparent molecular weight of 326, methyl 9,12‐epithiostearate, an adduct of methyltrans,trans‐ 9,11‐octadecadienoate and ben‐zene [bicyclo (4.4.0)‐deca‐2,5,7‐triene‐l‐(Ω‐carboxy‐methyl heptyl)‐4 hexyl] and a probable mixture of methyl 9,11‐epidithiostearate, methyl 9,12‐epidithio‐stearate, and methyl 10,12‐epidithiostearate.

Reductive dimerization of (+)-(R)-pulegone. Part 10. Absolute configuration of the spiro-atom of the resulting hydroxyperhydroindene-1-spirocyclohexanones

The reductive dimerization of (+)-(R)-pulegone [p-menth-4(8)-en-3-one] has been shown to produce two series of ketols which are derivatives of perhydroindene-1-spirocyclohexane. In this paper the absolute configuration of the spiro-carbon atom, different for the two series, has been determined by degradation of the ketols to the two geometric isomers of methyl 3-(1-methoxycarbonyl-4-methylcyclohexyl)-2,2,3-trimethylbutyrate [(13) and (14)], whose conformations are fixed by the bulkiest substituent; the 4-methyl group is axial in one of the isomers and equatorial in the other, and they show different and characteristic n.m.r. spectra.

Preparation and study of geometric isomers of methyl 2-nitro-3-[2-(5-X-furyl)]acrylates

Preparation and study of geometric isomers of methyl 2-nitro-3-[2-(5-X-furyl)]acrylates

ChemInform Abstract: THE INFRARED SPECTRA AND CONFORMATION OF METHYL AND ETHYL PROPENYL ETHERS

Abstract The infrared spectra of the cis and trans geometric isomers of methyl and ethyl propenyl ethers have been recorded in the liquid and vapour phase, in the region 4000-200 cm −1 . Solid phase spectra have also been recorded for all but trans methyl propenyl ether. Evidence is given for the existence of two rotameric forms for both the trans compounds, in each case the more stable conformer being planar s-cis; but a single non-planar conformation is suggested for the two cis isomers. The enthalpy difference between the two rotameric forms in trans ethyl propenyl ether was found to be 4.6 ± 1.0 kJ mol −1 (1100 ± 250 cal mol −1 ).

Separation and identification of geometrical isomers of 9,12-octadecadienoic and 9,12,15-octadecatrienoic acids

Geometrical isomers of methyl 9,12-octadecadienoate and methyl 9,12,15-octadecatrienoate were fractionated by thin-layer chromatography on Silica Gel G modified with silver nitrate and ammonium hydroxide. Dienoic esters were completely separated into three classes: (1) all trans; (2) trans-cis and cis-trans; and (3) all cis. Trienoic esters were similarly separated into four classes: (1) all trans; (2) di- trans, mono- cis; (3) di- cis, mono- trans; and (4) all cis. Complete separation of the cis, trans isomers of methyl octadecadienoate and of the mono- cis, di- trans and mono- trans, di- cis isomers of methyl octadecatrienoate was achieved by gas-liquid chromatography on glass capillary columns (Apiezon L).