New polyunsaturated organosilicon dendrimers

Spherical dendrimer of regular structure with the spatial characteristic S = 5, tetrakis[tris-(trimethylsilylethynyl)silyl-2-vinyldimethylsilylethynyl]silane, and the unsymmetrical binuclear dendrimer containing simultaneously groups (−CH₂CH₂−), (−CH=CH−), (−C≡C−) and combining the branches of the zero order (G0) and of the second generation (G2), 2-tris(trimethyl-silylethynyl)silyl-1-tris[tris(trimethylsilylethynyl)silylvinyldimethylsilylethynyl]silylethane were isolated from the reaction of hydrosilylation of tetrakis (dimethylethynylsilylethynyl)silane and vinyltris(dimethylethynylsilylethynyl)silane with trichlorosilane and a subsequent treatment of the reaction products with trimethylsilylethynylmagnesium bromide. NMR spectra of the synthesized compounds were studied.     

Novel acyclic and macrocyclic highly unsaturated silahydrocarbons

Two novel silicon-containing acetylenic synthons, 1-[dimethyl(ethynyl)silyl]-2-[ethynyl(methyl)-(vinyl)silyl]ethyne and bis[(ethynyldimethylsilyl)ethynyl](methyl)vinylsilane, were obtained by the reaction of diethynyl(methyl)vinylsilane with ethylmagnesium bromide and ethynylfluorodimethylsilane. The reaction of magnesium derivatives of the products and diethynyl(methyl)vinylsilane with organylhalosilanes gave macrocyclic polyunsaturated silahydrocarbons containing numerous endo- and exocyclic miltiple bonds.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1612–1616.Original Russian Text Copyright © 2004 by O. Yarosh, Zhilitskaya, N. Yarosh, Istomina, Albanov, Chuvashev, Voronkov.This revised version was published online in April 2005 with a corrected cover date.     

New polyunsaturated organosilicon dendrimers based on 1,1-diethynyl-and 1-vinyl-1-ethynylsilacycloalkanes

1,1-Dichloro-and 1-vinyl-1-chlorosilacyclanes were prepared by reactions of tetrachlorosilane or vinyltrichlorosilane with magnesium and 1,4-dibromobutane or 1,5-dibromopentane. The reactions of the products obtained with ethynylmagnesium bromide or bis(bromomagnesio)acetylene yield the corresponding ethynylsilacyclanes. Condensation of 1,1-diethynylsilacyclanes or bis(ethynylsilacyclopentyl)ethyne with an equimolar amount of ethylmagnesium bromide and methylbis(trimethylsilylethynyl)fluorosilane gave the corresponding highly unsaturated mono-and binuclear first-generation dendrimers with the cores formed by the silicon atoms incorporated in silacycloalkane fragments. The ¹H, ¹³C, and ²⁹Si NMR spectra of all the compounds obtained were studied. The key parameters and the chemical graph of the new dendrimers are presented.     

Binulcear polyunsaturated organosilicon dendrimers

Binuclear polyunsaturated organosilicon dendrimers of the zero and first generations, whose central silicon atoms are linked by-CH₂-Ch₂-,-CH=CH-, or-C≡C-bridges, and also containing internal (C≡C) and (CH=CH) groups are prepared. NMR spectra of all the compounds obtained are studied. Their molecular weights were calculated and evaluated experimentally. Key parameters of new dendrimers are presented.     

Hydrosilylation of methylenecyclopropane and methylenecyclobutane with dichloro(methyl)silane and synthesis of novel acetylenic silahydrocarbons from the reaction products

Hydrosilylation of methylenecyclopropane with dichloro(methyl)silane involves not only addition to the multiple bond, but also results in opening of the three-membered ring to form dichloro(cyclopropylmethyl)methylsilane and 1,4-bis(dichloromethylsilyl)butane. Dichloro(cycloalkylmethyl)methylsilanes were converted into the corresponding (cycloalkylmethyl)(diethynyl)methylsilanes by reaction with ethynylmagnesium bromide. The reaction of bis(bromomagnesioethynyl)(cyclobutylmethyl)methylsilane with dichlorodimethylsilane leads to cyclotetrasilaethyne framed with methyl and cyclobutyl groups. From 1,4-bis-[dichloro(methyl)silyl]butane and bis[(bromomagnesioethynyl)dimethylsilyl]ethyne or -ethene, 22-membered macrobicyclic highly unsaturated silahydrocarbons with an endocyclic tetramethylene bridge were synthesized.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1608–1611.Original Russian Text Copyright © 2004 by O. Yarosh, Zhilitskaya, N. Yarosh, Albanov, Voronkov.This revised version was published online in April 2005 with a corrected cover date.     

Potential sources of polyunsaturated fatty acids

All-Union Scientific-Research Institute of the Technology of Blood Substitute and Hormone Preparations, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, p. 592, July–August, 1988.     

Ene-yne metathesis of polyunsaturated norbornene derivatives

Norbornene derivatives bearing endo-substituents in the 5- and 6-positions were studied as substrates for ene-yne metathesis cascades. Substrates which contained an internal alkyne and a terminal alkene or alkyne in each sidechain were found to undergo a metathesis cascade leading to pentacyclic bis-dienes and bis-trienes. Attempts to extend the chemistry further to sidechains containing two internal alkynes or two internal alkynes and a terminal alkene were not successful with the first generation Grubbs' catalyst. However, the substrate containing two internal alkynes did react with the second generation Grubbs' catalyst to give a tetra-diene containing product.     

Three branch polyunsaturated organosilicon and organogermanium dendrimers

3-Branch dendrimers of the first generation possessing at the focal point, the silicon atom, a trimethylsilylvinyl or trimethylsilylethynyl group, and at the central germanium atom an isopropyl group have been synthesized using a combined approach or a convergent reaction scheme. NMR spectra of all synthesized compounds are studied, and their molecular masses are calculated and experimentally determined. The key parameters of new dendrimers are given.     

Direction of epoxidation of esters of polyunsaturated acids

Conclusions The direction of the epoxidation of a number of polyunsaturated acids was studied and it was shown that the epoxidation proceeds at the double bonds furthest away from the carbethoxyl group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 943–947, April, 1977.     

Photoelectron spectra of polyunsaturated [4,4,2]propellanes

The photoelectron spectra of the six propellanes 1 to 6 have been recorded. Those bands which correspond to ejection of an electron from a π-orbital have been assigned, using the concept of through bond and through space interaction. Homoconjugative interaction between the π-systems of the two butadiene moieties of 6 is of the same order as that of the π-orbitals in norbornadiene.     

Enzymatic hydrogen atom abstraction from polyunsaturated fatty acids

The oxidation of polyunsaturated fatty acids such as arachidonic and linoleic acid initiates a plethora of cell signaling pathways in animals and plants. The chemistry of the enzymatic oxidation has been investigated for several enzymes, most notably prostaglandin synthase and the lipoxygenases, revealing many surprises and impressive examples of enzymatic control of hydrogen atom abstraction and subsequent oxygenation.     

Oxidative degradation of eicosapentaenoic acid into polyunsaturated aldehydes

Eicosapentaenoic acid is converted in good overall yield to an α,β-ethylenic epoxide derivative. The oxidative cleavage of the epoxide ring with periodic acid in ether proceeded in part with acid-catalyzed rearrangement of the vinyl epoxide moiety prior to cleavage. Among the products were 2E- and 2Z, 5Z, 8Z, 11Z-tetradecatetraenal, 4-hydroxy-2E,6Z,9Z,12Z-pentadecatetraenal and (all-Z)-2-methoxy-3,6,9,12-pentadecatetraenal.     

Synthesis of polyunsaturated fatty acid-containing glucuronosyl-diacylglycerol through direct glycosylation

We describe a total synthesis of a polyunsaturated fatty acid (PUFA)-containing glucuronosyldiacylglycerol (GlcADG), which is a surrogate glycolipid whose synthesis is remarkably upregulated in plant membranes under phosphorus-depleted conditions. Glycosylation between the glucuronide donor bearing 3,4-dimethoxybenzyl (DMPM) protecting groups and di-acylglycerol acceptor proceeded smoothly in the presence of gold(I) catalyst to provide the protected α-isomer of GlcADG as the major product.     

Synthesis of silanes and germanes with polyunsaturated aliphatic substituents

Hydrosilylation of alkynes R₃MC≡CH (M = Si, Ge) afforded adducts whose subsequent treatment with ethynylmagnesium bromide gives polyunsaturated silanes and germanes R₃MCH=CHSi(C≡CH)₃. The latter can be subjected to the same transfomations to result in the unsaturated chain growth.     

A simplified method for analysis of polyunsaturated fatty acids

Background  

Analysis of fatty acid composition of biological materials is a common task in lipid research. Conventionally, preparation of samples for fatty acid analysis by gas chromatography involves two separate procedures: lipid extraction and methylation. This conventional method is complicated, tedious and time consuming. Development of a rapid and simple method for lipid analysis is warranted.     

Regioselective metathesis reactions of various polyunsaturated ketones and alcohols

The reactivity for metathesis reaction of some polyunsaturated cyclopentanols, and of a polyunsaturated ketone bearing vinyl groups or vinyl and propenyl groups has been examined. In the presence of two of these reactants, depending on the ruthenium catalyst employed, either the ring closing metathesis or the cross‐coupling metathesis was observed. Copyright © 2010 John Wiley & Sons, Ltd.