- Synthesis of isotopically labeled all-trans retinals for DNP-enhanced solid-state NMR studies of retinylidene proteins
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Three all-trans retinals containing multiple 13C labels have been synthesized to enable dynamic nuclear polarization enhanced solid-state magic angle spinning NMR studies of novel microbial retinylidene membrane proteins including proteorhodpsi
- Leeder, Alexander J.,Brown, Lynda J.,Becker-Baldus, Johanna,Mehler, Michaela,Glaubitz, Clemens,Brown, Richard C.D.
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- Cyclofarnesoids and methylhexanoids produced from β-carotene in Phycomyces blakesleeanus
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The oxidative cleavage of β-carotene in the Mucorales produces three fragments of 18, 15, and 7 carbons, respective heads of three families of apocarotenoids: The methylhexanoids, the trisporoids, and the cyclofarnesoids (named after their 1,6-cyclofarnes
- Alcalde, Eugenio,Medina, Humberto R.,Herrador, M. Mar,Barrero, Alejandro F.,Cerdá-Olmedo, Enrique
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- Method for preparing vitamin A
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The invention relates to a process for making vitamin A from ethynyl-retro-α-ionol using an allene acetate as intermediate.
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Page column 6 - 7
(2010/01/31)
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- Stereoselective syntheses of 13E and 13Z retinoic acids via a new intermediate C-15 β-methylenealdehyde
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The methylene-de-oxo-bisubstitution reaction between dimethyl isopropylidene malonate and the C-15 β-methylenealdehyde 1 which could serve as substitute for E β-ionylideneacetaldehyde 2, produces stereoselectively the E,E olefin. Hence, new stereoselective syntheses of 13 E and 13 Z retinoic acids were described. (C) 2000 Elsevier Science Ltd.
- Valla, Alain,Andriamialisoa, Zo,Prat, Virginie,Laurent, Alain,Giraud, Michel,Labia, Roger,Potier, Pierre
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p. 7211 - 7215
(2007/10/03)
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- A novel aldol condensation alternative: α,β-unsaturated aldehydes from 3-hydroxy-1-alkynes via dihydrodioxepins
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The controlled aldol condensation between an aliphatic ketone and an acetaldehyde equivalent remains a challenge. One solution to this evergreen problem consists of the nucleophilic addition of acetylene to the ketone and the subsequent isomerization of the resulting 3-hydroxy-1-alkyne to the corresponding 2-alkenal. So far, however, the latter Step could only be executed with acid-insensitive substrates. We now present a milder, three-step method which extends the scope of the procedure considerably. In the first step, the 3-hydroxy-1-alkynes are converted into 2-propynyl ethylene glycol monoethers; these then undergo base-catalyzed cyclization to give the dihydro-1,4-dioxepins, which are hydrolyzed in acidic medium in the third and final step.
- Wei, Heng-Xu,Schlosser, Manfred
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p. 1738 - 1743
(2007/10/03)
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- Obtention of 2,2-(diethoxy) vinyl lithium and 2-methyl-4-ethoxy butadienyl lithium by Arene-catalysed lithiation of the corresponding chloro derivatives. Synthetic applications
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Vinylic lithium reagents 1 and 2 could be obtained by the title procedure from their chloro precursors 5 and 6 instead of the less stable corresponding bromo derivatives 3 and 4. Condensation with carbonyl compounds leads to interesting synthetic applications such as a two steps synthesis of retinal 13 from β-cyclocitral 10.
- Si-Fodil, Mohamed,Ferreira, Humberto,Gralak, Jean,Duhamel, Lucette
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p. 8975 - 8978
(2007/10/03)
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- Polyvinylogation Reagents: 1-Lithio-4-trimethylsiloxy-penta-1,3-diene and 1-Lithio-4-ethoxy-2-methyl-buta-1,3-diene
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Title products, lithiodienol ethers 6a and 7a, synthetic equivalents of 4-lithio pent-3-ene-2-one and 4-lithio-senecialdehyde were obtained by bromine-lithium exchange.They are choice reagents for the transformations 1 -> 2 and 1 -> 3, respectively.
- Duhamel, Lucette,Ancel, Jean-Erick
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p. 9237 - 9250
(2007/10/02)
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- Synthesis of three retinal models, including the 10-s-cis-locked retinal, all-E-12,19-methanoretinal
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All-E-12,19-methanoretinal (1) is distinguished by the presence of the locked 10-s-cis conformation in the cyclohexadiene ring in the conjugated chain. 1 has been prepared together with its 13-Z isomer in an overall yield of 0.5percent. 1 and 13-Z-1 photochemically interconvert in a clean way.In this system, only photoisomerization around the C13=C14 double bond is observed.In the photostationary state, the 13-Z isomer is predominant.All-E-12-ethyl-19-methylretinal (2) and all-E-12-ethylretinal (3) were prepared in good overall yields (20percent and 30percent) from β-ionone using the novel synthon, 3-methyl-4-(diethylphosphono)-2-hexenenitrile (11).The photochemistry of these retinal derivatives is very similar to that of retinal.The 9-Z, 11-Z and 13Z isomers of 2 and 3 were photochemically prepared.The 13C NMR spectra of these new compounds gave information about the structural elements of alkyl groups in conjugated systems and about the conformation of the conjugated chain.
- Groesbeek, M.,Steen, R. van der,Vliet, J. C. van,Vertegaal, L. B. J.,Lugtenburg, J.
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p. 427 - 436
(2007/10/02)
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