Superacid cyclization of (2E,6E,10E,14E)-8-phenylsulfonylgeranylfarnesol tetrahydropyranyl ether

A mixture of (13E,17E)-12-phenylsulfonylbicyclogeranylfarnesol tetrahydropyranyl ether (8) and (13E,17E)-12-phenylsulfonylbicyclogeranylfarnesol (9) was formed by superacid low-temperature cyclization of exclusively trans-8-phenylsulfonylgeranylfarnesol tetrahydropyranyl ether (1). The structures of 8 and 9 were established using spectral data. The optically active form of 9 was also confirmed by retrosynthesis from (+)-sclareolide (10). __________ Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 224–228, May–June, 2007.     

Stereochemistry of nitrogen E lone pair in NH3E,NOFE, N2O3E2, AgNO2E,and NCl3E

We revisit nitrogen based simple fundamental molecules in their solid state structures, with the purpose of casting new light on the stereoactivity of valence lone pairs (LPs)—formally N(2s²)—in different crystal geometries. Based on coupled investigations of crystal chemistry and ab initio DFT calculations providing the electron localization function (ELF), LP behavior is analyzed precisely by finding its position E, orientation and “volume of influence” which consists in an electronic cloud generated around the so-called ‘centroïd’ Ec of the electronic doublet. The results show the paramount importance of the role of N(2s²) LP in the crystal network architecture through the different case studies pertaining to ammonia (NH₃), nitrosyl fluoride (NOF), nitrosyl nitrite (N₂O₃), silver nitrite (AgNO₂), and nitrogen trichloride (NCl₃). An unexpected direct ionic interaction between [NO]⁺ or Ag⁺ and the centroïd Ec of the [NO₂Ec]⁻ nitrite group has been evidenced in N₂O₃E₂ and AgNO₂, respectively.     

Efficient synthesis of 3E,13Z-octadecadienol,its acetate, 4E,6E,11Z-hexadecatrienal,and 4E,6E,11Z-hexadecatrienyl acetate,sex pheromones of some lepidopteran species

The title linear acetogenins have been synthesized by a strategy of joining acetylcyclopropane to 8Z-tridecenol or 5Z-decenol prepared after Julia, leading to the corresponding secondary cyclopropylcarbinols. The ZnBr₂/Me₃SiBrinitiated homoallylic rearrangement of the latter assures at a key step the stereospecific construction of transoid fragments of the target molecules.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2521–2529, November, 1991.     

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.     

Bioactive saponins and glycosides. XXIII. Triterpene saponins with gastroprotective effect from the seeds of Camellia sinensis--theasaponins E3, E4, E5, E6, and E7

The saponin fraction from the seeds of the tea plant [Camellia sinensis (L.) O. KUNTZE (Theaceae)] was found to exhibit potent protective effects on ethanol- and indomethacin-induced gastric mucosal lesions in rats. Five new triterpene saponins, theasaponins E3 (1), E4 (2), E5 (3), E6 (4), and E7 (5), were isolated together with 11 known saponins from the saponin fraction. The chemical structures of 1-5 were elucidated on the basis of chemical and physicochemical evidence. Among the isolated saponins, theasaponins E1 (6), E2 (7), and E5 (3) and assamsaponin C (10) showed an inhibitory effect on ethanol-induced gastric mucosal lesions at a dose of 5.0 mg/kg, p.o. and their activities were stronger than that of omeplazole. With regard to the structure-activity relationships of theasaponins, the following structural requirements for a protective effect on ethanol-induced gastric lesions were suggested; 1) the 21- and/or 22-acyl groups are essential for the activity, 2) acetylation of the 16-hydroxyl group reduce the activity.     

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.     

Nichtstationäre Kinetik bei SN1, SN2, E1, E2 und E1cb-Mechanismen

For the S_N1, S_N2, E₁, E₂, AND E₁cb mechanisms exact solutions of the kinetic equations are compared with solutions obtained under the hypothesis of stationarity. Exact integrals are calculated numerically for a set of the essential reaction rate constants. Comparison with the stationary state solution demonstrates that both types of solutions are approximately equal in many cases if the transient particle concentration remains low, whereas the conventional requirement | \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop x\limits^. $\end{document} | = 0 is unimportant. For approximation of exact kinetics by stationary kinetics, however, neither condition is sufficient nor necessary. Practical criterions for recognition of deviations from stationary kinetics are given.     

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     

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).     

HPV E6, E6AP and cervical cancer

Abstract

Every year, approximately 470,000 new cases of cervical cancer are diagnosed and approximately 230,000 women worldwide die of the disease, with the majority (~80%) of these cases and deaths occurring in developing countries. Human papillomaviruses (HPVs) are the etiological agents in nearly all cases (99.7%) of cervical cancer, and the HPV E6 protein is one of two viral oncoproteins that is expressed in virtually all HPV-positive cancers. E6 hijacks a cellular ubiquitin ligase, E6AP, resulting in the ubiquitylation and degradation of the p53 tumor suppressor, as well as several other cellular proteins. While the recent introduction of prophylactic vaccines against specific HPV types offers great promise for prevention of cervical cancer, there remains a need for therapeutics. Biochemical characterization of E6 and E6AP has suggested approaches for interfering with the activities of these proteins that could be useful for this purpose.

Publication history

Republished from Current BioData's Targeted Proteins database (TPdb; http://www.targetedproteinsdb.com).

     

Quantitative determination of prostaglandins E1, E2 and E3 in frog tissue

A method was developed for quantitative determination of endogenous production of prostaglandin (PG)E1, PGE2 and PGE3 by Rana temporaria lung, heart and urinary bladder homogenates, since these tissues contain the precursors, 8,11,14-eicosatrienoic, arachidonic and 5,8,11,14,17-eicosapentaenoic acids. Following homogenization and shaking at 22 degrees C for 30 min, media were extracted by XAD-2, treated with sodium hydroxide in order to convert PGE compounds into PGB compounds, purified by thin-layer chromatography, and analyzed by high-performance liquid chromatography with homo-PGE1 as an internal standard. The ratio of prostaglandins E1, E2 and E3 compared to the ratio of fatty acid precursors in tissue suggested that the tissue content of precursor is not the only factor determining the type of prostaglandin synthesized.     

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.     

Electrophilic cyclization of (E,E)-2-farnesylthiophene

Conclusions The electrophilic cyclization of (E, E)-2-farnesylthiophene has been studied for the first time, and it has been shown that the allylic thienyl group acts as a specific terminator which leads to the formation of a tetra cyclic molecule with a cis-hydrindane fragment.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1359–1362, June, 1981.Deceased.     

Highly stereoselective synthesis of (2E,4E)-dienamides and (2E,4E)-dienoates via a double elimination reaction

Highly stereoselective synthesis of (2E,4E)-dienamides and (2E,4E)-dienoates was achieved through a double elimination reaction of β-acetoxy sulfones.