Synthesis of (2Z,6Z,10Z,14E,18E)-farnesylfarnesol,

Nine-step synthesis of the title triterpenol from (E,E)-farnesol using a two-stage cis-C₅-homologation procedure is descrilaed.     

Conformational Properties of (Z,Z)-, (E,Z)-, and (E,E)-Cycloocta-1,4-dienes

Summary.  Ab initio calculations at the HF/6-31G^* level of theory for geometry optimization and the MP2/6-31G^*//HF/6-31G^* level for a single point total energy calculation are reported for (Z,Z)-, (E,Z)-, and (E,E)-cycloocta-1,4-dienes. The C ₂-symmetric twist-boat conformation of (Z,Z)-cycloocta-1,4-diene was calculated to be by 3.6 kJ·mol⁻¹ more stable than the C _S-symmetric boat-chair form; the calculated energy barrier for ring inversion of the twist-boat conformation via the C _S-symmetric boat-boat geometry is 19.1 kJ·mol⁻¹. Interconversion between twist-boat and boat-chair conformations takes place via a half-chair (C ₁) transition state which is 43.5 kJ·mol⁻¹ above the twist-boat form. The unsymmetrical twist-boat-chair conformation of (E,Z)-cycloocta-1,4-diene was calculated to be by 18.7 kJ·mol⁻¹ more stable than the unsymmetrical boat-chair form. The calculated energy barrier for the interconversion of twist-boat-chair and boat-chair is 69.5 kJ·mol⁻¹, whereas the barrier for swiveling of the trans-double bond through the bridge is 172.6 kJ·mol⁻¹. The C _S symmetric crown conformation of the parallel family of (E,E)-cycloocta-1,4-diene was calculated to be by 16.5 kJ·mol⁻¹ more stable than the C _S-symmetric boat-chair form. Interconversion of crown and boat-chair takes place via a chair (C _S) transition state which is 37.2 kJ·mol⁻¹ above the crown conformation. The axial- symmetrical twist geometry of the crossed family of (E,E)-cycloocta-1,4-diene is 5.9 kJ·mol⁻¹ less stable than the crown conformation. Corresponding author. E-mail: isayavar@yahoo.com Received March 25, 2002; accepted April 3, 2002     

An ab Initio study of conformational properties of (Z,Z)-, (E,Z)- and (E,E)-cycloocta-1,5-diene

Ab initio calculations at HF/6-31G* level of theory for geometry optimization and MP2/6-31G*//HF/6-31G* for a single point total energy calculation are reported for the three geometrical isomers of cycloocta-l,5-diene 1–3.     

Stereoselective syntheses of substituted methyl (Z,E,E)-deca-2,7.9-trienoates and substituted methyl (Z,E,E)-undeca-2,8,10-trienoates

Lindlar hydrogenation of substituted methyl ($\text{E}$,$\text{E}$)-deca-7,9-dien-2-ynoates and substituted methyl ($\text{E}$,$\text{E}$)-undeca-8,10-dien-2-ynoates affords selectively the corresponding ($\text{Z}$,$\text{E}$,$\text{E}$)-trienes.     

Candidate Trail Attractants of Reticultermes lucifugus: Stereoselective Syntheses of (3Z, 6E,BE)-(3Z, 6E, 8Z)-and (3Z, 6Z, 8Z)-3,6,8 -Dodecatrien-1-OL1

Stereoselective syntheses on a gram scale of (3Z,6E,8E)-, (3Z,6E,8Z)-and (3Z,6Z,8Z)-3,6,8-dodecatrien-1-ol, 8, 9 and 10, respectively, are described. A key step of the synthesis of 8 consisted of a copper-mediated coupling reaction between 4-(2-tetrahydropyranyloxy)-1-butynylmagnesium bromide (15) and the mesyl ester of (2E,4E)-2,4-octadien-1-ol (14). A similar copper-mediated reaction between 15 and the mesyl ester of (E)-2-octen-4-yn-1-ol (19) was used to construct the C-12 carbon skeleton of 9. On the other hand, the synthesis of 10 was based on a palladium-promoted reaction between (Z)-1-bromo-1-pentene (23) and the organozinc bromide derived from 3,6-heptadiyn-1-yl acetate (27).     

Characterization of posticlure and the structure-related sex pheromone candidates prepared by epoxidation of (6Z,9Z,11E)-6,9,11-trienes and (3Z,6Z,9Z,11E)-3,6,9,11-tetraenes

trans-11,12-Epoxy-(6Z,9Z)-6,9-henicosadiene (posticlure) has been identified from a pheromone gland of the lymantriid species, Orgyia postica. Since the diversity of Lepidoptera suggests that some species utilize the structure-related epoxy compound as a sex pheromone component, epoxydienes and epoxytrienes derived from (6Z,9Z,11E)-6,9,11-trienes and (3Z,6Z,9Z,11E)-3,6,9,11-tetraenes with a C₁₉–C₂₁ chain were systematically synthesized and the chemical data were accumulated in order to contribute to a new pheromone research. Peracid oxidation of each triene and each tetraene produced, respectively, a mixture of three epoxydienes (cis-6,7-epoxy-9,11-diene; cis-9,10-epoxy-6,11-diene; and trans-11,12-epoxy-6,9-diene) and four epoxytrienes (cis-3,4-epoxy-6,9,11-triene; cis-6,7-epoxy-3,9,11-triene; cis-9,10-epoxy-3,6,11-triene; and trans-11,12-epoxy-3,6,9-triene). While the 9,10-epoxy compounds were unstable and, interestingly, converted into 9-ketone derivatives after chromatography over SiO₂, each positional isomer was isolated by HPLC equipped with an ODS column, and the chemical structure was determined by NMR analysis. On the GC-MS analysis with a DB-23 column, the positional isomers were also eluted separately and characteristic mass spectra were proposed. By comparing the spectral data of the epoxy compounds with a different carbon chain, diagnostic fragment ions reflecting the chemical structure were determined as follows: m/z 79, 109, 113, and M-114 for the 6,7-epoxydienes; m/z 69, 97, 111, 139, and M-111 for the 9,10-epoxydienes; m/z 57, 79, 109, 136, M-151, and M-111 for the 11,12-epoxydienes; m/z 79, 91, 105, and 119 for the 3,4-epoxytrienes; m/z 79, 124, M-124, M-96, and M-69 for the 6,7-epoxytrienes; m/z 79, 95, 109, 137, and M-108 for the 9,10-epoxytrienes; and m/z 79, 134, M-149, M-109, and M-95 for the 11,12-epoxytrienes.     

Synthese der (1Z,3E) und (1Z,3Z)-isomeren des wisanins

The (1Z,3E)- and (1Z,3Z)-isomers of wisanine were synthesized and characterized by their spectroscopic data.     

Julia-Kocienski reaction-based 1,3-diene synthesis: aldehyde-dependent (E,E/E,Z)-selectivity

A new modification of Julia-Kocienski olefination reaction based on the use of cation-specific chelating agents that yields 1,3-dienes with predictable (E/Z)-selectivity on newly created double bond was developed. The influence of the aldehyde structure on reaction (E/Z) selectivity is discussed and rationalized.     

Two (E,E)- and (Z,E)-thiazol-5-ylpenta-2,4-dienones

In order to characterize the structural elements that might play a role in non-covalent DNA binding by the antitumor antibiotic leinamycin, we have solved the crystal structures of the two leinamycin analogs, methyl (R)-5-{2-[1-(tert-butoxy­carbonyl­amino)­ethyl]­thia­zol-4-yl}penta-(E,E)-2,4-dienoate, C₁₆H₂₂N₂O₄S, (II), and 2-methyl-8-oxa-16-thia-3,17-di­aza­bicyclo­[12.2.1]­heptadeca-(Z,E)-1(17),10,12,14-tetraene-4,9-di­one, C₁₄H₁₆N₂O₃S, (III). The penta-2,4-dienone moiety in both of these analogs adopts a conformation close to planarity, with the thia­zole ring twisted out of the plane by 12.9 (2)° in (II) and by 21.4 (4)° in (III).     

Straightforward Preparation of (2E,4Z)-2,4-Heptadien-1-ol and (2E,4Z)-2,4-Heptadienal

Abstract

A concise synthesis of (2E,4Z)-2,4-heptadien-1-ol and (2E,4Z)-2,4-heptadienal is presented. Commercially available (Z)-2-penten-1-ol was converted to ethyl-(2E,4Z)-2,4-heptadienoate by reaction with activated MnO₂ and (carboethoxymethylene)triphenylphosphorane in the presence of benzoic acid as a catalyst. Ethyl-(2E,4Z)-2,4-heptadienoate was converted to (2E,4Z)-2,4-heptadien-1-ol with LiAlH₄. The alcohol was partially oxidized to (2E,4Z)-2,4-heptadienal with MnO₂. The title compounds are male-specific, antennally active volatile compounds from the Saltcedar leaf beetle, Diorhabda elongata Brulle (Coleoptera: Chrysomelidae) and have potential use in the biological control of the invasive weed saltcedar (Tamarix spp).     

Diepoxy[18]annulene(10.0) : (Z,E,Z,E,Z)‐Diepoxy[18]annulen(10.0) – ein hochdynamisches Annulen

Diepoxy[18]annulenes(10.0): ( Z , E , Z , E , Z )‐Diepoxy[18]annulene(10.0) – a Highly Dynamic Annulene The McMurry reaction of (all‐E)‐5,5′‐([2,2′‐bifuran]‐5,5′‐diyl)bis[penta‐2,4‐dienal] ( 13 ) only occurs intramolecularly to give a mixture of the diepoxy[18]annulenes(10.0) 6 and 7 . Tetraepoxy[36]annulene(10.0.10.0) resulting from an intermolecular McMurry reaction is not formed. According to spectroscopic data, 6 is (Z,E,Z,E,Z)‐ and 7 (Z,E,E,Z,E)‐configured. The ¹H‐NMR data confirm that in 6 the (E)‐ethene‐1,2‐diyl bonds (C(11)=C(12) and C(15)=C(16)) rotate around the adjacent σ‐bonds. Beginning at −70°, this rotation freezes, and 6 is becoming a diatropic aromatic ring system. Beside [18]annulene itself, (Z,E,Z,E,Z)‐diepoxy[18]annulene(10.0) 6 is the only hitherto known [18]annulene derivative with dynamic properties.     

Synthesis and reactivity of E,Z butadiene-iron tricarbonyl complexes.

The synthesis, structure and thermal stability of the E,Z butadiene-iron tricarbonyl complex 1 is reported. This complex reacts with organometallic nucleophiles in a stereoselective synthesis of functionalized E,Z dienes.     

Le systeme Z α, β-dinitrostilbene — E α, β-dinitrostilbene

Z-α,β-dinitrostilbène (Z-DNS) is employed as amine reagent. The absence of isomerization into E-DNS by heating was verified using DTA. The Z-DNS-E-DNS phase diagram was established, and the following data obtained:

for E-DNS,T _f =459 K, ΔH _f =15 kJ·mpl^?1, and solid-solid phase transition atT=439 K.

for Z-DNS,T _f =380 K, ΔH _f =20 kJ·mol^?1.

The binary phase diagram exhibits a eutectic equilibrium at 368 K with the liquid composition 89相似文献   

Stereospecific synthesis of 11S, 12S-oxido 5Z, 7E, 9E, 14Z-eicosatetraenoic acid

The first stereospecific synthesis of 11S,12S-oxido 5Z, 7E, 9E, 14Z-eicosatetraenoic acid has been achieved from 2-deoxy-D-ribose using either a Horner-Emmons or Wittig condensation to form the 9,10-trans or the 5,6-cis-double bond respectively.