Isoprene derivatives

The isoprene-derived molecule whose structure is shown here is known alternately as Coumarin and warfarin. By the former name, it is a widely prescribed anticoagulant. By the latter name, it is a component of rodent poisons. How can the same chemical species be used for such disparate purposes The key to both uses lies in its ability to act as an antagonist of vitamin K in the body. 

Prenylation (covalent attachment of an isoprenoid see Fig. 27-30) is a common mechanism by which proteins are anchored to the inner surface of cellular membranes in mammals (see Fig. 11-14). In some of these proteins the attached lipid is the 15-carbon farnesyl group others have the 20-carbon geranylgeranyl group. Different enzymes attach the two types of lipids. It is possible that prenylation reactions target proteins to different membranes, depending on which lipid is attached. Protein prenylation is another important role for the isoprene derivatives of the pathway to cholesterol. 

A similar intermolecular cyclization was recently utilized in the synthesis of highly substituted dihydropyrrole derivatives [133 -135]. In a specific example, the addition of pentadienyltosylamide derivatives 177 to propynyl(phenyl)iodo-nium triflate initiates a sequence of transformations that furnishes the complex, highly functionalized cyclopentene-annelated dihydropyrrole products 178 in moderate yields with complete stereoselection (Scheme 66). Under similar reaction conditions, the isomeric isoprene-derived tosylamide 179 reacts with propynyl(phenyl)iodonium triflate to give azabicyclo[3.1.0]hexane 180 as the final product [134]. 

Organic Syntheses and Organic Reactions, Jack and his students published research papers on organo-boron compounds, furan derivatives, dienes, ketene derivatives, the structure of gliotoxin, and biosynthesis of isoprene derivatives. 

Reaction of AUSCeHsls with an a,/3-unsaturated ester results in a l,l,3-tris(phenyIthio)-l-alkene such as 3, which was converted into the isoprene derivative 5, as shown in equation (I). 

The isoprene derivative 272 reacts with dpk to afford 273 . Complexes 274 react with dpk to give 275 . 

Using an aliphatic monoterpene like myrcene as reaction partner for 1 the formation of silacylobutanes E/Z-1 and E/Z-S in a ratio of 34 30 22 14 is observed an ene product could not be detected. In this case myrcene behaves like an isoprene derivative, which forms only [2+2] cycloadducts with 1 [8]. The reaction with 2, however, yields a product mixture containing the silacyclobutanes E/Z-9 and E/Z-10, the Diels-Alder compounds 11 and 12, the ene product 13, and the silene dimer 7Z-14 [14, 15] (Fig. 2). 

A final example of the kind of specificity exhibited by enzymes is provided by squalene oxidocyclase. As shown in Fig. 4.65, this enz)nne catalyzes the conversion of the 30-carbon isoprene derivative squalene 2,3-epoxide, which contains only one asymmetric carbon atom, to the steroid lanosterol in a single step that forms four new carbon-carbon bonds and seven new chiral centres in 100% yield and with no isomeric impurities. 

The alkylation of phenols with isoprene and isoprene derivatives can be catalyzed over rhodium complexes of TPPTS [22], In the case where the isoprene derivative is myrcene, methanol is added to the reaction mixture. The apparent benefit is to increase reaction rates with the highly water-soluble myrcene substrate. The alkylation of 2-naphthol with myrcene is shown in Eq. (2). In 2 h at 100 °C in aqueous methanol a 40% conversion of myrcene is observed (160 turnovers). 

Cholesterol serves as the biosynthetic precursor for several vital compounds, including a variety of steroid hormones and bile acids. Many of these compounds, and many other polyisoprenoid compounds biosynthetically related to cholesterol, act biologically as important regulatory compounds [105]. In mammals such regulatory compounds include steroid hormones and vitamins A and D. Steroids and other isoprene derivatives also play important regulatory roles in other phyla. Several insect hormones, for example, are isoprenoid derivatives [106] (cf. Chapter 8). Memy of the floral scents of plants are isoprene derivatives. 

In the presence of tricyclohexylphosphine, Ni-diene condensations form Cg-containing ( -bis(a]lyl) complexes. Treatment of the tricyclohexylphosphine adduct of (cyclododecatriene)Ni with 1,3-dienes affords thermally stable complexes having the stoichiometry Ni(diene)2P(C6Hu)3 From IR and NMR studies and the structure of the isoprene derivative , these complexes contain the S)j -bis(allyl) structure, both in the solid state and in solution ... 

The C—C bond formation in these complexes is reversible. Treatment of the butadiene or isoprene derivatives with molten triphenylphosphine leads to diene evolution, in moderate yields, but reductive coupling of the M—C bonds occurs when the complexes are reacted with CO at low T since 4-vinylcyclohexene is formed . An unstable olefin complex can be formed from divinylcyclobutane and (cyclododecatriene)Ni(tricyclohexylphosphine) that liberates divinylcyclobutane when... 

A major problem for the use of natural plant-derived matter in the chemical industry occurs when molecules are under-functionalized because they have only one group that can be easily modified or used for chemical linkage formation. Especially fatty acid- or isoprene-derived molecules need the introduction of one or two functionalized groups. 

Hayakawa et al. 1991a,b) as an antibiotic, although it has alkaloidal attributes. We chose to include this compound here to illustrate an interesting utilization of HMBC data to establish the structure of a long, isoprene-derived chain connecting two portions of the molecular structure. 

Ubiquinones have a long, isoprene-derived side chain (see Spedal Topic E in WileyPLUS and Section 23.3). Ten isoprene units are present in the side chain of human ubiquinones. This part of their structure is highly nonpolar, and it serves to solubilize the ubiquinones within the hydrophobic bilayer of the mitochondrial inner membrane. Solubility in the membrane environment facilitates their lateral diffusion from one component of the electron transport chain to another. In the electron transport chain, ubiquinones function by accepting two electrons and two hydrogen atoms to become a hydroquinone. The hydroquinone form carries the two electrons to the next acceptor in the chain ... 

Reviews (in Japanese) on the synthesis of terpene derivatives from isoprene (1) and on isoprene-derived chemicals have been published. Picture grammars bounded by a finite set of rules have... 

Terpene compounds were also examined for inducing activity because they, like the steroids, are isoprene derivatives, although representing simpler molecules than the steroids. The basic structural... 

The compound of simplest structure which had inducing activity several times that of AIA was cyclopentadecanone (14), otherwise known as Exaltone, the perfumery fixative. This compound consists of a large saturated ring with one carbonyl group, and may be written to resemble a steroid in configuration. The most active of the isoprene derivatives was -ionone (15) it was about ten times as active as AIA in porphyrin induction. 

Harrison has suggested that fumitremorgin B and austamide may arise bio-synthetically from an isoprene-derived imine such as that shown in Scheme 14 [23]. Cyclization of the imine either via path A or path B result in the formation of the fumitremorgin B and deoxyaustamide ring systems, respectively. 

Structural studies of polymer surfaces. Materials that have been studied include PMMA [239], PMMA-polypyrrole composites [240], polyfchloromethyl styrene) honnd 1,4,8,11-tetrazacyclotetradecane, polyfchloromethyl styrene) honnd thenoyl triflnoroacetone [241], poly(dimethyl siloxane)-polyamide copolymers [242], PS [243], ion-implanted PE [244], monoazido-terminated polyethylene oxide [245], polynrethanes [246], polyaniline [247], flnorinated polymer films [248], poly(o-tolnidine) [249], polyetherimide and poly benzimidazole [250], polyfnllerene palladinm [251], imidazole-containing imidazolylethyl maleamic acid-octadecyl vinyl ether copolymer [252], polyphenylene vinylene ether [253], thiophene oligomers [254], flnorinated styrene-isoprene derivative of a methyl methacrylate-hydroxyethyl methacrylate copolymer [255], polythiophene [256], dibromoalkane-hexaflnorisopropylidene diphenol and bisphenol A [257], and geopolymers [258]. 

Nitriles can be used as starting material for the bisdithioesters (62 n = 4, 5, lO), whereas the derivatives with shorter chain lengths (62 n = l-3), as well as methyl dithiocinnamate (63), are accessible from /VA -disubstituted thioamides via the corresponding imidothioate iodides. Methyl di-thioacrylate (65), the simplest unsaturated dithioester, was prepared by flash vacuum thermolysis of a precursor dithioester (64), which had been obtained from the corresponding nitrile (equation 64). It can be isolated as a red monomeric compound at 77 K but dimerizes rapidly at room temperature. The p,7-unsaturated isoprene derivative (66) and the methyl 2-arylpropanedithioates (67) were prepared from phenyl isothiocyanate and used as educts for syntheses of lavandulal and ar-curcumene. Also ethyl furane 3-carbodithioate (68), as prepared from the nitrile, has found application in syntheses of the natural products egona ketone and ar-turmerone. ... 

Only a few papers describe the polymerization of unsaturated monomers with a covalent M-O bond. Ziegler-Natta copolymerization of the diisobutylaluminium-alkoxy-isopren derivative 35 with butadiene occurs by a neodynium catalyst in a hydrocarbon solvent [180]. Mainly the monomer 35 in, A-cis configuration is found in the copolymer. A chiral monomer based on ethyleneglycolmonomethacrylat being substituted by alkoxy derivatives of Ti(IV) and different chiralic substituents was polymerized [181]. Such polymers are interesting as chiralic catalysts. 

In this chapter we examine the mechanism for the OH initiated oxidation of isoprene under low NO levels (NO < 50 ppt). At higher NO levels, although it is likely that there are still processes that are missing within atmospheric models (e.g. [3]), isoprene oxidation chemistry is simplified somewhat by the loss of the isoprene-derived peroxy radicals being dominated by reaction with NO. Under low NO c conditions the fate of these peroxy radicals is much less certain. New insights into the isoprene mechanism have been derived using a combinatirHi of ... 

While the initial epoxide production from ISOPOOH is OH-neutral, and will thus have little impact on modelled OH concentrations in low NO environments, the discovery of lEPOX species highlights significant gaps in our understanding of isoprene oxidation chemistry. Moreover, the fate of the lEPOX species may be important in terms of understanding field observations of OH and formation of SOA. It is expected that the hfetime of lEPOX with respect to OH addition is of the order of 18-22 h, and that reactive uptake of lEPOX to aerosol surfaces and subsequent SOA formation could be important [35]. If lEPOX are involved in SOA formation then isoprene-derived carbon will be sequestered from the gas phase, potentially reducing the expected impact of isoprene on atmospheric OH concentrations. 

Froyd KD, Murphy SM, Murphy DM, de (jouw JA, Eddingsaas NC, Wennberg PO (2010) Contribution of isoprene-derived organosulfates to free tropospheric aerosol mass. Proc Natl Acad Sci USA 107 21360-21365... 

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