- Asymmetric Synthesis of Serricornin via Boronic Esters
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Highly stereoselective boronic ester chemistry has been used for the synthesis of (4S,6S,7S)-7- hydroxy-4,6-dimethylnonanone (1), the pheromone of the cigarette beetle. 2-Bromo-1-butene (8) was made from 1-butyne via bromoboration and protodeboronation, and was converted to 1-ethylethenylmagnesium bromide. (R,R)-1,2-Dicyclohexyl-1,2-ethanediol ["(R)-DICHED"] methylboronate was treated with (dichloromethyl)lithium to yield (R)-DICHED (S)-1-chloroethylboronate (9), which with 1-ethylethenylmagnesium bromide yielded (R)-DICHED (R)-(2-ethyl-1-methyl-2- propenyl)boronate (10). Further chain extensions with (chloromethyl)lithium, (dichloromethyl)- lithium followed by methylmagnesium bromide, and (dichloromethyl)lithium followed by ethyl- magnesium bromide completed assembly of the carbon skeleton. Deboronation with hydrogen peroxide yielded (3S,5S,6S)-2-ethyl-3,5-dimethylocten-6-ol (14), which with osmium tetraoxide and sodium periodate yielded 1.
- Matteson, Donald S.,Singh, Rajendra Prasad,Schafman, Bonnie,Yang, Jing-Jing
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p. 4466 - 4469
(2007/10/03)
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- Stereocontrolled synthesis of serricornin
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Serricornin, the attractant pheromone of the cigarette beetle, is synthesized in high enantiomeric and diastereomeric purity via a series of reactions of asymmetric 2-(1-haloalkyl)-1,3,2-dioxaborolanes with Grignard reagents, which lead to the key intermediate ?,S-(R*,R*,R*)!-2-ethyl-3,5-dimethyl-l-octen-6-ol. Oxidative cleavage of the carbon-carbon double bond of ?S-(R*,R*,R*)!-2-ethyl-3,5-dimethyl-l-octen -6-ol with osmium tetroxide and sodium periodate yields serricornin.
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- Structure based interference with insect behaviour - Cyclopropene analogues of pheromones containing Z-alkenes
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Analogues of the pheromones of three insect species (Musca domestica L., Plutella xylostella L. and Ephestia elutella Hbn.) in which a Z-alkene has been replaced by a 1,2-disubstituted cyclopropene have been synthesized. The analogues interfere with normal mating behaviour for each species.
- Al Dulayymi, Juma'a R.,Baird, Mark S.,Simpson, Michael J.,Nyman, Susan,Port, Gordon R.
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p. 12509 - 12520
(2007/10/03)
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- Structure-Activity Relationships of Cyclopropene Compounds, Inhibitors of Pheromone Biosynthesis in Bombyx mori
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According to the synthetic route for 11,12-methylenehexadec-11-enoic acid [10-(2-butyl-1-cyclopropenyl)decanoic acid] and the amide, their related cyclopropene compounds, which possessed a propene ring at the 7,8-, 9,10-, or 13,14-position in a C16 chain and the 11,12-position in a C14 or C18 chain, were synthesized via the corresponding 1-alkyl-1,2,2-tribromocyclopropane. Their activities as biosynthetic inhibitors of bombykol [(10E, 12Z)-10,12-hexadecadien-1-ol; sex pheromone of the silkworm moth Bombyx mori L.] were measured with virgin female silkworm moths in vivo. The 7,8-methylene compounds were inactive even at the dose of 10 μg/gland, but other compounds at 1 μg/gland inhibited the conversion of [16,16,16-2H3]hexadecanoic acid to bombykol to some extent. Each amide showed stronger inhibitory activity than the corresponding acid, and the 11,12-methylene amide with a C16 chain was the strongest (I50 = 0.016 μg/gland) among the tested compounds. Furthermore, experiments comparing the incorporation of [1-14C]hexadecanoic acid into bombykol and another alcohol component in the pheromone gland, (Z)-11-hexadecen-1-ol, suggested that the Δ11-desaturation was blocked by 9,10- and 11,12-methylene compounds and the subsequent Δ10,-12-desaturation by 11,12- and 13,14-methylene compounds.
- Ando, Tetsu,Ohno, Ryuta,Ikemoto, Kazuhisa,Yamamoto, Masanobu
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p. 3350 - 3354
(2007/10/03)
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- Alkyl Bromide Photobromination: Catalysis by Hydrogen Bromide and the Elimination-Readdition Pathway
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In the photobromination of alkyl bromides, hydrogen bromide is shown to act as a catalyst and a kinetic study implies that two molecules of the acid are involved in catalysis.The catalysis is specific in two ways: only HBr is effective and it operates only with alkyl bromides having a β-hydrogen available for substitution.HBr favours the formation of 1,2-dibromides.This catalytic pathway is superimposed on the classical, uncatalysed mechanism.Isotopic labelling experiments show that an elimination-readdition pathway may also account for part of the reaction (maximum 20percent) but cannot explain the migration of bromine which is observed in the formation of β-dibromides.
- Soumillion, Jean-Ph.,Ronneau, Claude,Dejaifve, Pierre
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p. 1907 - 1914
(2007/10/02)
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