- A convenient access to thermodynamically nonstabilised spiroketal isomers: The first synthesis of (Z)-7-methyl-1,6-dioxaspiro[4.5]decane
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Functionalised hydroxy α-alkynones were transformed to the corresponding spiroketals by a one-pot cascade consisting of palladium-catalysed hydrogenation of the triple bond, hydroxyl group deprotection and spirocyclisation under mild nonacidic conditions. The reaction does not rely upon thermodynamic control to set the configuration of the ketal stereocentre so that both the anomerically stabilised and nonstabilised isomers are similarly accessible.
- Doubsky, Jan,?aman, David,Zedník, Ji?í,Va?í?ková, Soňa,Koutek, Bohumír
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- Alkynyltrifluoroborates as versatile tools in organic synthesis: A new route to spiroketals
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(Chemical Equation Presented) A simple and efficient two-step approach to spiroketals is described. Key steps include the preparation of functionalized hydroxyl α-alkynones by ring-opening reactions of lactones with lithium alkynyltrifluoroborates followed by a palladium-catalyzed hydrogenation/ spirocyclization of the prespiroketal intermediate.
- Doubsky, Jan,Streinz, Ludvik,Saman, David,Zednik, Jiri,Koutek, Bohumir
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p. 4909 - 4911
(2007/10/03)
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- Lipase mediated resolution of 1,3-butanediol derivatives: Chiral building blocks for pheromone enantiosynthesis. Part 3
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(R,S)-1,3-Butanediol 5 was kinetically resolved by enzymatic acetylation with vinyl acetate under the presence of Chirazyme L-2, c-f, yielding (S)-1-O-acetyl-1,3-hydroxybutane 6 and (R)-1,3-di-O-acetyl-1,3-butanediol 7 with enantiomeric excesses of 91% (E = 67.3). Compounds 6 and 7 were easily transformed into the corresponding (S)-3-O-(2-methoxyethoxymethyl)-3-hydroxybutanal 10 and (R)-3-benzyloxybutanal 19, through a protection-deprotection and functional group interchange methodology. Subsequent reaction of 10 and 19 with 3-(methoxycarbonylpropionylmethylene)triphenylphosphorane afforded methyl (E,S)-8-O-(2-methoxyethoxymethyl)-4-oxo-5-nonenoate 12 and (E,R)-8-benzyloxy-4-oxo-5-nonenoate 20. The alkenes 19 and 20 were then catalytically hydrogenated to the corresponding saturated esters 13 and 21. Treatment of 13 and 21 with 1,2-ethanedithiol/F3B·OEt2 afforded dithioketals 14 and 22, which were respectively reduced to (S)-1,8-dihydroxy-4-nonanone ethylidenedithioketal 15 and (R)-8-O-benzyl-1,8-dihydroxy-4-nonanone ethylidenedithioketal 23. Finally, deprotection of 15 by catalytic hydrogenation under acidic conditions gave the expected (5S,7S)-(-)-7-methyl-1,6-dioxaspiro[4.5]decane 1. The (5R,7R)-(+)-1 enantiomer was analogously prepared from 23. Both compounds were formed by this procedure with an e.e. of 91%.
- Izquierdo, Isidoro,Plaza, Maria T.,Rodriguez, Miguel,Tamayo, Juan A.,Martos, Alicia
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p. 293 - 300
(2007/10/03)
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- Spiroacetals and other venom constituents as potential wasp attractants
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The major volatile spiroacetals from the venom of both the common wasp, Vespula vulgaris and the German wasp V. germanica, viz. 7-methyl-1,6-dioxaspiro[4,5]decane and 7-ethyl-2-methyl-1,6-dioxaspiro[4,5]decane, respectively, were synthesized by known methods. These acetals, along with N-isopentylacetamide (the major volatile amide from wasp venom), 2-heptanone (a honeybee pheromone), 2-methyl-3-buten-2-ol (a component of hornet venom), cuticle wax from V. vulgaris, and venom sacs from both wasp species were assayed by EAG and olfactory bioassay for attractancy to V. vulgaris workers. Antennal responses to all test chemicals were recorded. Acetal isomers (±)-2 and (±)-3,N-isopentylacetamide, and 2-heptanone were attractive to V. vulgaris workers at levels of 1 μmol. Greater quantities of the same compounds were repellent to V. vulgaris workers.
- Weston, Roderick J.,Woolhouse, Anthony D.,Spurr, Eric B.,Harris, Richard J.,Suckling, D. Max
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p. 553 - 568
(2007/10/03)
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- Chemistry of Fruit-flies. Spiroacetal-rich Secretions in several Bactrocera species from the South-West Pacific Region
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The male rectal glandular secretions from the fruit-fly pest species Bactrocera (Notodacus) xanthodes (Broun) and Bactrocera (Bactrocera) kirki (Froggatt) and the non-pest species, Bactrocera (Bactrocera) kraussi (Hardy) are rich in spiroacetals.In B. xanthodes, (5R,7S)-7-methyl-1,6-dioxaspiordecane is prominent, whereas in B. kirki (2S,6R,8S)-2,8-dimethyl-1,7-dioxaspiroundecane is the single major volatile component.B. kraussi, although rich (ca. 40percent) in (2S,6R,8S)-2,8-dimethyl-1,7-dioxaspiroundecane, contains other spiroacetals and a number of compounds that may be biosynthetically related to the spiroacetals.The ab- solute configurations have been determined by enantioselective syntheses and chiral gas-chromatographic determinations.The results of examinations of Bactrocera (Bactrocera) passiflorae (Froggatt) and Bactrocera (Bactrocera) facialis (Coquillett) are also reported.
- Fletcher, Mary T.,Wells, Jaqueline A.,Jacobs, Mark F.,Krohn, Sabine,Kitching, William,et al.
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p. 2827 - 2832
(2007/10/02)
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- CHEMICO-ENZYMATIC SYNTHESES OF RACEMIC AND CHIRAL ISOMERS OF 7-METHYL-1,6-DIOXASPIRODECANE
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Porcine pancreatic lipase (PPL) mediated resolution of 6-heptene-2-ol afforded the enantiomers in high optical purities.Alkylation products of the dianion of the 2-4'-hydroxypentyl-1,3-dithiane prepared from the enantiomers, followed by alkylative hydrolysis, afforded 97percent optically pure E-7-methyl-1,6-dioxaspirodecane.
- Ramaswamy, Sowmianarayanan,Oehlschlager, Allan C.
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p. 1157 - 1162
(2007/10/02)
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- Synthesis of spiroacetal pheromones via metalated hydrazones
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The synthesis of simple alkyl substituted spiroacetals by α,α'-alkylation of metalated acetone dimethylhydrazone with appropriate electrophiles and subsequent acid catalyzed cleavage and ring closure of the products is described.
- Enders,Dahmen,Dederichs,Gatzweiler,Weuster
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p. 1013 - 1019
(2007/10/02)
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- FUNCTIONALIZED NITROALKANES IN SYNTHESIS OF 1,6-DIOXASPIRO(4.5)DECANE COMPONENTS OF PARAVESPULA VULGARIS PHEROMONE
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(E)-2-, (Z)-2-, and (E)-7-methyl-1,6-dioxa(4.5)decane isomers which are components of odours of Papavespula vulgaris have been prepared by two practical and efficient procedures starting from easily available functionalized nitroalkanes.
- Rosins, Goffredo,Ballini, Roberto,Marotta, Emanuela
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p. 5935 - 5942
(2007/10/02)
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- WITTIG AND HORNER-WITTIG COUPLING REACTIONS OF 2-SUBSTITUTED CYCLIC ETHERS AND THEIR APPLICATION TO SPIROKETAL SYNTHESIS
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Wittig and Horner-Wittig coupling reactions of tetrahydropyran or tetrahydrofuran 2-triphenylphosphonium salts or 2-diphenylphosphine oxides with aldehydes and lactols affords good yields of the corresponding enol ethers.In selected examples these enol ether products may be further converted to spiroketals some of which are natural pheromones derived from Dacus oleae and Paravespula vulgaris.
- Ley, Steven V.,Lygo, Barry,Organ, Helen M.,Wonnacott, Anne
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p. 3825 - 3836
(2007/10/02)
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- Synthesis of Spiroacetals using Organoselenium-mediated Cyclisation Reactions. X-Ray Molecular Structure of (2S,8R)-8-Methyl-2-phenyl-1,7-dioxaspiroundecan-4(R)-ol
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Alkenyl hydroxyketones undergo cyclisation via their hemiacetal form, in the presence of N-phenylselenophthalimide (NPSP) and a Lewis acid, to give the corresponding phenylseleno-substituted spiroacetals.Using this methodology the synthesis of trans- and cis-2-methyl-1,6-dioxaspirononane (1), trans- and cis-2-ethyl-1,6-dioxaspirononane (chalcogran)(2), trans- and cis-2-methyl-1,6-dioxaspirodecane(3), trans-7-methyl-1,6-dioxaspirodecane (4), trans-2-methyl-1,7-dioxaspiroundecane (5), and (2S,8R)-8-methyl-2-phenyl-1,7-dioxaspiroundecane-4-one(6) has been achieved, after reductive removal of selenium using Raney-nickel in diethyl ether.Compound (2) is the principal aggregation pheromone from Pityogenes chalcographus (L), whilst compounds (3) and (4) constitute the pheromone components of the common wasp, Paravespula vulgaris.The structure of the spiroacetal (6) was determined as a result of X-ray crystallography of a later derivative, obtained by sodium borohydride reduction of (6).
- Doherty, Annette M.,Ley, Steven V.,Lygo, Barry,Williams, David J.
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p. 1371 - 1378
(2007/10/02)
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- SYNTHESIS OF METHYL-1,6-DIOXASPIRODECANES USING ORGANOSELENIUM MEDIATED CYCLIZATION REACTIONS
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Three naturally occuring methyl-1,6-dioxaspirodecanes have been prepared in good yield using organoselenium mediated reactions during the crucial cyclization process.
- Ley, Steven V.,Lygo, Barry
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p. 4625 - 4628
(2007/10/02)
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- Synthesis of optically active 2s-, and 7s-methyl-1.6-dioxa-spiro[4.5] decane, the pheromone components of Paravespula vulgaris (L.), from S-ethyl lactate.
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(-)-2S, 5RS-1 and (-]-7S, 5S-2 are obtained from S-ethyl lactate 4 and their absolute configuration is thus directly correlated. Accurate enantiomeric compositions of intermediates and products were measured by complexation gas chromatography on nickel-, and manganese-bis-3-heptafluorobutyryl-1R-camphorate, 3. It could be conclusively established that the syntheses proceed with a high degree of preservation of configuration.
- Hintzer,Weber,Schurig
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