Organoboranes. 36. A Simple,General Synthesis of Alkynyl Ketones1 and [E]-1,3-Alkenynes via Thexylchloroborane-Dimethyl Sulfide

Thexylchloroborane-dimethyl sulfide ( 1 ) hydroborates representative 1-bromo-1-alkynes in the presence of 10% boron tribromide as a catalyst to afford thexyl-(cis-1-bromo-1-alkenyl)-chloroboranes ( 2 ). Treatment of these intermediates with isopropyl alcohol provides the corresponding isopropyl thexyl(cis-1-bromo-1-alkenyl)borinates ( 3B ). Subsequent treatment with alkynyllithium gives the corresponding “ate” complexes ( 4 ) which undergo intramolecular migration of the alkynyl group from boron to the adjacent carbon, displacing the bromine, producing the corresponding cis-vinylboranes ( 5 ). These intermediates ( 5 ) provide the corresponding alkynyl ketones ( 6 ) on oxidation and the corresponding stereodefined conjugated enynes ( 7 ) of high isomeric purity on protonolysis. Yields in the range of 60–65% were realized.     

A New Chiral P,N‐Ligand Derived from 1‐Phenylphospholane‐2‐carboxylic Acid (Phenyl‐P‐proline) for Palladium‐Catalyzed Asymmetric Allylic Substitution Reactions

New types of P,N‐ligands, cis‐ and trans‐ 3 , containing a tetrahydroisoquinoline skeleton as an N‐donor were synthesized from (1R,2S)‐1‐phenylphospholane‐2‐carboxylic acid (phenyl‐P‐proline, 1 ). The cis isomer, cis‐ 3 , was found to act as an excellent ligand in palladium‐catalyzed asymmetric allylic substitution reactions. The reactions of 1,3‐diphenyl‐2‐propenyl acetate ( 5 ) with several nucleophiles in the presence of [Pd(π‐allyl)Cl]₂, cis‐ 3 (Pd : ligand=1 : 2), and a base afforded the desired products in high yields with high enantioselectivity. It was suggested that these ligands did not serve as P,N‐bidentate ligands but as P‐monodentate ligands in these reactions.     

Fatty Acid Desaturation and Elongation Reactions of <Emphasis Type="Italic">Trichoderma</Emphasis> sp. 1-OH-2-3

The fatty acid desaturation and elongation reactions catalyzed by Trichoderma sp. 1-OH-2-3 were investigated. This strain converted palmitic acid (16:0) mainly to stearic acid (18:0), and further to oleic acid (c9-18:1), linoleic acid (c9,c12-18:2), and α-linolenic acid (c9,c12,c15-18:3) through elongation, and Δ9, Δ12, and Δ15 desaturation reactions, respectively. Palmitoleic acid (c9-16:1) and cis-9,cis-12-hexadecadienoic acid were also produced from 16:0 by the strain. This strain converted n-tridecanoic acid (13:0) to cis-9-heptadecenoic acid and further to cis-9,cis-12-heptadecadienoic acid through elongation, and Δ9 and Δ12 desaturation reactions, respectively. trans-Vaccenic acid (t11-18:1) and trans-12-octadecenoic acid (t12-18:1) were desaturated by the strain through Δ9 desaturation. The products derived from t11-18:1 were identified as the conjugated linoleic acids (CLAs) of cis-9,trans-11-octadecadienoic acid and trans-9,trans-11-octadecadienoic acid. The product derived from t12-18:1 was identified as cis-9,trans-12-octadecadienoic acid. cis-6,cis-9-Octadecadienoic acid was desaturated to cis-6,cis-9,cis-12-octadecatrienoic acid by this strain through Δ12 desaturation. The broad substrate specificity of the elongation, and Δ9 and Δ12 desaturation reactions of the strain is useful for fatty acid biotransformation.     

Cyclopinolenic acids: Synthesis,derivatives and thermal properties

The two isomeric cyclopinolenic acids (CP-1 and CP-2), components of distilled tall oil, have been synthesized by means of an intramolecular Diels-Alder reaction of isomers of 5,10,12-octadecatrienoic esters, themselves synthesized in a stereocontrolled manner. The 5cis,10-trans,12trans isomer cyclizes at 200°C to a 1:3 mixture of esters of CP-1 and CP-2. At 200°C, the 5cis,10trans,12cis isomer is unreactive, but at 240°C it gives the same CP-1 + CP-2 ester mixture, presumably by way of prior isomerization to the 5cis,10trans,12trans isomer. A subambient thermal study of CP-1 and CP-2 and their derivatives shows that the compounds, excluding CP-1, lack crystalline structures or melting points, and display glass transitions only, below −80°C for esters and below −50°C for the carboxylic acids.     

Transition Structures of the Electrocyclic Reactions of cis,cis,cis-1,3,5-Cyclooctatriene

The electrocyclic reactions of cis,cis,cis-1,3,5-cyclooctatriene have been studied using ab initio molecular orbital theory. cis,cis,cis-1,3,5-cyclooctatriene can undergo an electrocyclic ring opening in a conrotatory fashion to form cis,cis-1,3,5,7-octatetraene and a disrotatory electrocyclization to form bicyclo[4.2.0]octa-2,4-diene. The transition structures for these electrocyclic reactions have been located. Geometry optimizations employed restricted Hartree-Fock calculations and the 3–21G and 6–31G* basis sets. Electron correlation energies were calculated using second-order, and in some cases fourth-order, Møller-Plesset theory. Scaled RHF/6–31G* force constants were employed in the prediction of secondary deuterium isotope effects for the conrotatory ring opening. The ground state of cis,cis,cis-1,3,5-cyclooctatriene exists in a twist-boat conformation with staggering at the saturated linkage. The transition structure for the conrotatory electrocyclic ring opening to form cis,cis-1,3,5,7-octatetraene has a helical structure, which has implications for the stereoselectivities of ring closure of 1-substituted-cis,cis-1,3,5,7-octatetraenes. The disrotatory transition structure for the electrocyclization to form bicyclo[4.2.0]octa-2,4-diene is strongly distorted from C_s symmetry, in contrast to the transition structure for the disrotatory electrocyclization of cis-1,3,5-hexatriene. This distortion is caused by staggering about the saturated linkage.     

Synthesis of Sodium (+)-(12S,13R)-Epoxy-cis-9-octadecenyl Sulfonate from Vernonia Oil

A water-soluble, foaming epoxyalkene sulfonate, sodium (+)-(12S,13R)-epoxy-cis-9-octadecenyl sulfonate, was synthesized from vernonia oil (VO) by a series of simple reactions that include transesterification, metal hydride reduction, tosylation, and S_N2 reactions. Conversion of VO into vernonia oil methyl esters (VOME) using sodium methoxide was quantitative. Subsequent reduction of VOME with lithium aluminum hydride yielded (+)-(12S,13R)-epoxy-cis-9-octadecenol (94%), along with minor amounts of hexadecenol, octadecenol, cis-9-octadecenol, and cis-9,12-octadecandienol. The (+)-(12S,13R)-epoxy-cis-9-octadecenol, was tosylated with p-toluenesulfonyl chloride to give (+)-(12S,13R)-epoxy-cis-9-octadecenyl tosylate at 96% yield. Iodination of the tosylate with sodium iodide and subsequent S_N2 reaction with sodium sulfite afforded (+)-(12S,13R)-epoxy-cis-9-octadecenyl sulfonate (63% yield). This study demonstrates the ability to produce an epoxyalkenyl sulfonate, belonging to a class of anionic surfactants, from VO without destroying the epoxy functionality in the (+)-(12S,13R)-epoxy-cis-9-octadecenyl moiety of VO. The critical micelle concentration of the synthesized sulfonate was also determined.     

Gas-liquid chromatography-mass spectrometry of the 4,4-dimethyloxazoline derivatives of Δ5-unsaturated polymethylene-interrupted fatty acids from conifer seed oils

The fatty acids from the seed oils of three Conifer species (one Pinaceae,Pinus pinaster, and two Cupressaceae,Chamaecyparis lawsoniana andBiota orientalis) have been analyzed as their 4,4-dimethyloxazoline (DMOX) derivatives by gas-liquid chromatography coupled with mass spectrometry. The structures of six Δ5-unsaturated polymethylene-interrupted fatty acids (Δ5-UPIFA) were established, confirming previous studies in which they were identified by their equivalent chainlengths (ECL) and by comparison with related authentic standards. These acids were:cis-5,cis-9 18∶2,cis-5,cis-9,cis-12 18∶3 (P. pinaster),cis-5,cis-9,cis-12,cis-15 18∶4 (C.lawsoniana),cis-5,cis-11 20∶2,cis-5,cis-11,cis-14 20∶3 (all species),cis-5,cis-11,cis-14,cis-17 20∶4 (B. orientalis) acids. In addition,cis-9 18∶1,cis-9,cis-12 18∶2 (all species) andcis-9,cis-12,cis-15 18∶3 (Cupressaceae) acids, together with their elongation products [cis-11 20∶1,cis-11,cis-14 20∶2 (all species) andcis-11,cis-14,cis-17 20∶3 (B. orientalis) acids] were also identified. In the mass spectra, DMOX derivatives of all Δ5-UPIFA showed an intense peak atm/z 153, which is a diagnostic ion of fatty acid derivatives with a Δ5-ethylenic bond. Other double bonds were localized by ion pairs that differed by 12 atomic mass units. The present study fully justifies the use of ECL to identify Δ5-UPIFA in Conifer seed oils, in which they are ordinary components.     

Regiospecific analysis of conifer seed triacylglycerols by gas-liquid chromatography with particular emphasis on Δ5-olefinic acids

Dibutyroyl derivatives of monoacylglycerols (DBMAG) from conifer seed oil triacylglycerols (TAG) were prepared by partial deacylation of TAG with ethylmagnesium bromide followed by diesterification with n-butyryl chloride. The resulting mixtures were analyzed by gas-liquid chromatography (GCL) with 65% phenylmethyl silicon open tubular fused-silica capillary column operated under optimal conditions and separated according to both their fatty acid structures and their regiospecific distribution. Seed oils of 18 species from 5 conifer families (Pinaceae, Taxaceae, Cupressaceae, Cephalotaxaceae, and Podocarpaceae) were analyzed. The chromatograms showed a satisfactory resolution of DBMAG containing palmitic (16∶0) stearic (18∶0), taxoleic (cis-5, cis-9 18∶2), oleic (cis-9 18∶1), cis-vaccenic (cis-11 18∶1), pinolenic (cis-5, cis-9, cis-12 18∶3), linoleic (cis-9, cis-12 18∶2), α-linolenic (cis-9 cis-12, cis-15 18∶3), and an almost baseline resolution of DBMAG containing gondoic (cis-11 20∶1), cis-5, cis-11 20∶2, sciadonic (cis-5, cis-11, cis-14 20∶3), dihomolinoleic (cis-11 cis-14 20∶2), juniperonic (cis-5, cis-11, cis-14, cis-17 20∶4), and dihomo-α-linolenic (cis-11, cis-14, cis-17 20∶3) acids. We have observed that results for Pinus pinaster and P. koraiensis seed oils obtained with this new simple method compared favorably with literature data established with other usual regiospecific analytical techniques. Δ5-Olefinic acids are esterified mainly at the external positions of the glycerol backbone in all cases, in agreement with data obtained by other methodologies allowing validation of the GLC regiospecific method. To date, 45 gymnosperm species (mostly Coniferophytes) from 21 genera belonging to 9 families have been analyzed, all of them showing a definite enrichment of Δ5-olefinic acids in the external positions of TAG. These fatty acids (FA), with one exception only, represent between-2 and 8% of FA esterified to the internal positions. For some species, i.e., P. koraiensis and P. pinaster, this asymmetrical distribution was established by at least three analytical procedures and confirmed by stereospecific analysis of their seed TAG.     

New synthesis ofcis-3,cis-5- andtrans-3,cis-5-tetradecadienoic acids,pheromone constituents ofattagenus elongatulus andA. megatoma

A new method for the synthesis ofcis-3,cis-5- andtrans-3,cis-5-tetradecadienoic acids, pheromone constituents of the dermestid beetlesAttagenus elongatulus andA. megatoma, was developed. The syntheses are based upon the formation oftrans-2-tetradecen-5-ynoic acid by reaction of 4-bromo-2-butenoic acid with 1-decynylmagnesium bromide. The enynoic acid undergoes alkali-induced isomerization to yield a mixture of acids from whichcis-3- andtrans-3-tetradecen-5-ynoic acids were separated in 31% and 34% yields, respectively. Methyltrans-2-tetradecen-5-ynoate was similarly prepared and isomerized to furnish methylcis-3-tetradecen-5-ynoate in 8% yield. Reduction of the tetradecenynoic acids with dicyclohexylborane gavecis-3,cis-5-andtrans-3,cis-5-tetradecadienoic acids in 4% and 39% yields, respectively. A better yield (49%) in the reduction ofcis-3-tetradecen-5-ynoic acid tocis-3,cis-5-tetradecadienoic acid was obtained by hydrogenation over Lindlar's catalyst. Similarly, reduction of methylcis-3-tetradecen-5-ynoate with disiamylborane gave 22% methylcis-3,cis-5-tetradecadienoate.     

Trans-10,Cis-12 conjugated linoleic acid reduces triglyceride content while differentially affecting peroxisome proliferator activated receptor γ2 and aP2 expression in 3T3-L1 preadipocytes

A series of experiments was conducted using 3T3-L1 preadipocytes as the cell model to determine: (i) whether the triglyceride (TG)-lowering effects of a crude mixture of conjugated linoleic acid (CLA) isomers were due to a specific isomer of CLA and the timing of treatment, (ii) if CLA reduced TG content by inhibiting a key regulator of adipogenesis, (iii) if CLA incorporated into either neutral lipid or phospholipid cell fractions, and (iv) whether the effects of CLA treatment were reversible. Trans-10,cis-12 CLA reduced TG content, whereas the cis-9,trans-11 isomer increased TG content compared to vehicle [bovine serum albumin (BSA)] controls. Treatment with 50 μM trans-10,cis-12 CLA during the entire 6 d of differentiation reduced TG content to a greater extent than treatment during either the first 3 d or last 3 d of differentiation. Trans-10,cis-12 CLA treatment of preadipocyte cultures for 48 h increased peroxisome proliferator activated receptor γ2 (PPARγ2) protein expression compared to cultures treated with linoleic acid (LA) or the BSA controls. CLA had no effect on adipose P2 (aP2), a fatty acid-binding protein regulated by PPARγ2. Both the cis-9,trans-11 and the trans-10,cis-12 isomers of CLA were incorporated into neutral lipids and phospholipids. However, cis-9,trans-11 CLA levels were one- to twofold higher than trans-10,cis-12 CLA levels. Moreover, trans-10,cis-12 CLA treatment reduced cis-11 18∶1 concentrations in both neutral lipids and phospholipids while increasing cis-9 18∶1 and 18∶2 concentrations. Palmitoleic acid (16∶1) levels were also lower in the neutral lipid fraction of cultures treated with trans-10,cis-12 CLA. Supplementing trans-10,cis-12 CLA-treated cultures (50 μM) with increasing levels of LA resulted in a dose-dependent increase in TG content compared to cultures treated with 50 μM CLA alone. LA supplementation also prevented some of the morphological changes associated with trans-10,cis-12 CLA treatment as seen with scanning electron microscopy. Treatment with 50μM trans-10,cis-12 CLA for 6 d decreased PPARγ2 levels, and supplementation of CLA-treated cultures with LA increased PPARγ2 levels compared with cultures treated with CLA alone. Taken together, these data indicate that in cultures of 3T3-L1 preadipocytes: (i) trans-10,cis-12 CLA is the TG-lowering isomer of CLA, and its effects are dependent on dose, duration of treatment, and the amount of LA in the cultures; (ii) trans-10,cis-12 CLA treatment alters the monounsaturated fatty acid profile of neutral- and phospholipids of the cultures; and (iii) although acute (2−d) trans-10,cis-12 CLA treatment increased PPARγ2 protein levels, chronic (6−d) treatment decreased PPARγ2 levels.     

Synthesis of fatty 2-oxazolines from fatty methyl 2,3-epoxy ester

Reaction of methyltrans-2,3-epoxyhexadecanoate (I) with benzonitrile in presence of boron trifluoride-etherate (BF₃-etherate) as catalyst has yieldedcis-2-phenyl-4-tridecyl-5-carbomethoxy-2-oxazoline (II), methyl 2-hydroxy-3-benzamidohexadecanoate (IV) and methyl 2,3-dihydroxyhexadecanoate (III). On the other hand, reactions of I with acetonitrile and acrylonitrile have resulted in the formation of their corresponding hydroxyamides, methyl 2-hydroxy-3-acetamidohexadecanoate (VI) and methyl 2-hydroxy-3-acryloamido hexadecanoate (VII), respectively, along with the product (III) only. Pyrolysis of hydroxyamides (IV), (VI) and (VII) afforded their corresponding 2-oxazolines,cis-2-phenyl-4-tridecyl-5-carboxy-2-oxazoline (V),cis-2-methyl-4-tridecyl-5-carboxy-2-oxazoline (VIII) andcis-2-vinyl-4-tridecyl-5-carboxy-2-oxazoline (IX), respectively, in good yields. The products have been characterized with the help of spectral and microanalyses. Presented at the 4th Annual Convention of the Indian Council of Chemists held in December 1984 at Gorakhpur University, India.     

Effect of phosphatidylcholine structure on the adenylate cyclase activity of a murine fibroblast cell line

To determine which structural characteristics of membrane phospholipids influence adenylate cyclase activity, we measured basal and sodium fluoride- or forskolin-stimulated activity in a murine fibroblast cell line,i.e., Balb/c3T3 cells grown in media supplemented with fetal calf serum (FCS), lipid-depleted FCS (LD-FCS) or LD-FCS complexed with different phosphatidylcholine (PC) molecular species. Cells grown in the presence of LD-FCS showed a substantial decrease in their basal and NaF-stimulated adenylate cyclase activities; however, their forskolin-stimulated activity was not altered, suggesting that the enzyme's catalytic site is not affected by changes in membrane lipids. Media supplemented with different LD-FCS/PC complexes were shown to prevent the LD-FCS-mediated reduction of basal and NaF-stimulated adenylate cyclase activity to different extents. Addition ofcis-9-16∶1/cis-9-16∶1,cis-9-18∶1/cis-9-18∶1 orcis-9-18∶1/cis-9,12-18∶2sn-glycerophosphocholine (GPC) completely restored adenylate cyclase activity, whilecis-11-18∶1/cis-11-18∶1 GPC was not effective and only a partial recovery was observed with 16∶0/16∶0, 16∶0/cis-9-18∶1 andtrans-9-18∶1 GPC. Considering the structural features of these seven PC molecular species, the findings suggest that an optimal lipid environment is conferred to the enzyme by the presence of thecis double bonds, each located in Δ9 position of the PC acyl chains. The limited effect ofcis-9-16∶1/cis-9-18∶1 GPC andcis-9-18∶1/cis-9-16∶1 GPC suggests that an equal length of the terminal hydrocarbon chains extending bevond the Δ9 double bonds is also important. Moreover, complete restoration of adenylate cyclase activity in cells exposed to 16∶0/cis-9,12-18∶2 GPC suggests that twocis-9,12 double bonds located on the same chain are as effective as twocis-9 double bonds each located on two different chains of PC. As the four double bonds of 16∶0/cis-5,8,11,14-20∶4 GPC had no effect, a mere increase in the number of double bonds seems insufficient to build an optimal lipid microenvironment for the enzyme.     

Enantioselective Construction of Chiral 2,3‐cis‐Dimethyldihydrobenzofuran with an All‐Carbon Quaternary Center: An Efficient Approach to (+)/(−)‐PI‐220 and (+)‐3‐epi‐Furaquinocin C

A new strategy for the enantioselective construction of chiral 2,3‐cis‐dimethyldihydrobenzofurans has been developed by a ruthenium‐catalyzed asymmetric hydrogenation of racemic α‐aryloxybutanone via dynamic kinetic resolution (DKR), combined with a palladium‐catalyzed intramolecular reductive Heck cyclization. Starting from optically active 2,3‐cis‐dimethyldihydrobenzofuran, the natural products (+)/(−)‐PI‐220 and (+)‐3‐epi‐furaquinocin C were synthesized in high yields.

     

Biological enantioselective reduction of methylcyclohexanones by Glomerella cingulata

Biological reduction of alkylcyclohexanones by Glomerella cingulata was studied. With this organism regioisomeric 2-, 3- or 4-methylcyclohexanone gave the corresponding cis- and trans-methylcyclohexanols. The major metabolites of (±)-2- and (±)-3-methylcyclohexanone were cis-2- and cis-3-methylcyclohexanol. On the other hand, 4-methylcyclohexanone yielded mainly the trans-4-methylcyclohexanol. In addition, the metabolites from (±)-2- and (±)-3-methylcyclohexanone indicated enantioselective reduction by specific optical rotation of the products. The enantiomeric excesses of the microbiological reduction products were determined by NMR spectra of (+)-MTPA-esters of the alcohols produced. The reduction of (±)-2-methylcyclohexanone was stereospecific, with the (2R)-ketone being converted to the corresponding (+)-cis-2-methylcyclohexanol (1S-2R); absolute configuration, 92% e.e. On the other hand, the enantiomeric excess of the major metabolite of (±)-3-methylcyclohexanone was (−)-cis-3-methylcyclohexanol (1S-3R); absolute configuration, 33% e.e.     

Lipase-catalyzed fractionation of conjugated linoleic acid isomers

The abilities of lipases produced by the fungus Geotrichum candidum to selectively fractionate mixtures of conjugated linoleic acid (CLA) isomers during esterification of mixed CLA free fatty acids and during hydrolysis of mixed CLA methyl esters were examined. The enzymes were highly selective for cis-9,trans-11–18∶2. A commercial CLA methyl ester preparation, containing at least 12 species representing four positional CLA isomers, was incubated in aqueous solution with either a commercial G. candidum lipase preparation (Amano GC-4) or lipase produced from a cloned high-selectivity G. candidum lipase B gene. In both instances selective hydrolysis of the cis-9,trans-11–18∶2 methyl ester occurred, with negligible hydrolysis of other CLA isomers. The content of cis-9,trans-11–18∶2 in the resulting free fatty acid fraction was between 94 (lipase B reaction) and 77% (GC-4 reaction). The commercial CLA mixture contained only trace amounts of trans-9,cis-11–18∶2, and there was no evidence that this isomer was hydrolyzed by the enzyme. Analogous results were obtained with these enzymes in the esterification in organic solvent of a commercial preparation of CLA free fatty acids containing at least 12 CLA isomers. In this case, G. candidum lipase B generated a methyl ester fraction that contained >98% cis-9,trans-11–18∶2. Geotrichum candidum lipases B and GC-4 also demonstrated high selectivity in the esterification of CLA with ethanol, generating ethyl ester fractions containing 96 and 80%, respectively, of the cis-9,trans-11 isomer. In a second set of experiments, CLA synthesized from pure linoleic acid, composed essentially of two isomers, cis-9,trans-11 and trans-10,cis-12, was utilized. This was subjected to esterification with octanol in an aqueous reaction system using Amano GC-4 lipase as catalyst. The resulting ester fraction contained up to 97% of the cis-9,trans-11 isomer. After adjustment of the reaction conditions, a concentration of 85% trans-10,cis-12–18∶2 could be obtained in the unreacted free fatty acid fraction. These lipase-catalyzed reactions provide a means for the preparative-scale production of high-purity cis-9,trans-11–18∶2, and a corresponding CLA fraction depleted of this isomer.     

Caltha palustris L. Seed Oil. A source of four fatty acids withcis-5-unsaturation

The seed oil ofCaltha palustris L. yields two unusual polyunsaturated components, all-cis-5,11,14-eicosatrienoic acid (23%) and all-cis-5,11,14,17-eicosatetraenoic acid (1%). The C₁₈ monoene fraction (26%) is a mixture ofcis-5- andcis-9-octadecenoic acids (2∶1). The C₂₀ monoene fraction (12%) is a mixture ofcis-11- andcis-5-isomers (3∶1). No. Utiliz. Res. Dev. Div., ARS, USDA.     

Evidence for [1,5] sigmatropic rearrangements of CLA in heated oils

Linoleic acid was heated at 200°C under helium. Analysis of degradation products by GC on a long polar open tubular capillary column showed the presence of CLA isomers. The identified mono trans CLA isomers were cis-9, trans-11, trans-9, cis-11, trans-10, cis-12, cis-10, trans-12, trans-8, cis-10, and cis-11, trans-13 18:2 acids. Oils containing different levels of linoleic acid (peanut, sesame seed, and safflower seed oils) were also heat treated, resulting in similar CLA distributions. Elution order was confirmed using cis-9, trans-11 and trans-10, cis-12 acid methyl esters standards and their respective configuration isomers (trans-9, cis-11, cis-10, trans-12), obtained after mild selenium-catalyzed isomerization. These results indicated that two conjugated mono trans isomers of 18:2 acid, cis-8, trans-10 and trans-11, cis-13 18:2 were absent from the series, thus strongly suggesting that some constraints were preventing their formation. By heating pure methyl rumenate (cis-9, trans-11 18:2) under similar conditions, isomerization resulted principally in a nearly equimolar mixture of methyl rumenate and trans-8, cis-10 18:2. Similarly, the methyl ester of trans-10, cis-12 18:2 acid was partially transformed into cis-11, trans-13 18:2 acid. Respective geometrical isomers were also formed in trace amounts. A concerted pericyclic isomerization mechanism, a [1,5] sigmatropic rearrangement, is proposed that limits the conjugated system to isomerization from a cis-trans acid to a trans-cis acid, and vice versa. This mechanism is consistent with undetected cis-8, trans-10 and trans-11, cis-13 18:2 isomers in heated oils containing linoleic acid.     

Specificity of the pheromone system ofAdoxophyes orana andClepsis spectrana

The pheromone system of the summer fruit tortrix mothAdoxophyes orana (Fischer von Röslerstamm) consists of a mixture ofcis-9- andcis-11-tetradecen-1-ol acetate (cis-9- andcis-11-TDA, respectively) in a ratio of 9:1. Substitution of one or both of these compounds by related unsaturated acetates reduced the attractancy. Onlycis-11-TDA could be replaced bycis-11-tridecen-1-ol acetate (cis-11-TriDA), although the 9:1 mixture ofcis-9-TDA andcis-11-TriDA was less attractive in the field than the pheromone system itself. The major component of the pheromone system of the leaf rollerClepsis spectrana (Treitschke)(cis-9-TDA:cis-11-TDA=1:9) could also be replaced bycis-11-TriDA, again with some reduction in attractancy.     

Iron‐Catalyzed Regio‐ and Stereoselective Conjugate Addition of Aryl‐Grignard Reagents to α,β,γ,δ‐Unsaturated Sulfones and its Synthetic Application

The iron‐catalyzed δ‐addition of aryl‐Grignard reagents to α,β,γ,δ‐unsaturated sulfones proceeded in a regio‐ and stereoselective manner to give cis‐4‐aryl‐2‐alkenyl sulfones. Allylic alkylation of the resultant products was performed without isomerization of the cis‐olefin to give cis‐4‐aryl‐1,1‐dialkyl‐2‐alkenyl sulfones, which upon intramolecular Friedel–Crafts reaction with aluminum chloride gave 1,4‐dihydronaphthalenes having a quaternary carbon center.     

Hydrogen pressure-dependence in the ring-opening reactions of substituted cyclopropanes over Rh/SiO2 catalyst

The hydrogen coverage and the structures of the reactants influence the selectivity and mechanism of the ring-opening reactions of ethyl-(ECP),cis-1,2-dimethyl-(cDMCP),trans1,2-dimethyl-(tDMCP), 1,1-dimethyl-(1, 1DMCP) and 1, 1, 2, 2-tetramethylcyclopropane (TMCP) over Rh/SiO₂ catalyst; a new phenomenon was observed for the transformations of ECP,tDMCP and 1, 1DMCP, viz. the turnover frequency vs. H₂ pressure functions pass through a minimum.