- Asymmetric synthesis of long chain β-hydroxy fatty acid methyl esters as new elastase inhibitors
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Herein, β-hydroxy methyl esters with an even carbon chain length of 12-20 1b-5b were synthesized by three different asymmetric reduction methods I, II III from their corresponding β-keto methyl esters 1a-5a with the aim of determining their elastase activities. In method I, chiral catalyst A was prepared from chiral ligand (R)-binaphthol 1, while in method II, chiral catalyst B was synthesized from (2R,3R)-diisopropyl tartrate 2. Chiral catalyst B has not previously been used in asymmetric borane reductions or in the asymmetric synthesis of chiral β-hydroxy methyl esters. In method III, an asymmetric reduction was catalysed by (R)-Me-CBS oxazaborolidine 3. Hydride transfer was carried out in all of these methods by BH3· SMe2. Chiral hydroxy methyl esters with an (S)-configuration were synthesized by method I and with an (R)-configuration via methods II and III. The chiral hydroxy methyl esters obtained were analysed by chiral HPLC for their ee % values. Methods I, II and III were applied to long chain β-keto methyl esters for the first time. The reduction methods I, II and III were examined in terms of reaction yield and enantiomeric excess according to carbon chain length and the variable ratio of chiral catalysts to β-keto methyl ester. The highest enantiomeric excess of 90% ee was found in method III for 12 and 14 carbon numbers.
- Hasdemir, Belma,Onar, Huelya Elik,Yusufolu, Aye
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- Non-volatile floral oils of Diascia spp. (Scrophulariaceae)
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The floral oils of Diascia purpurea, Diascia vigilis, Diascia cordata, Diascia megathura, Diascia integerrima and Diascia barberae (Scrophulariaceae) were selectively collected from trichome elaiophores. The derivatized floral oils were analyzed by gas chromatography-mass spectrometry (GC-MS), whilst the underivatized samples were analysed by electrospray ionization mass spectrometry (ESI-MS) and Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS). The most common constituents of the floral oils investigated are partially acetylated acylglycerols of (3R)-acetoxy fatty acids (C14, C16, and C18), as was proven with non-racemic synthetic reference samples. The importance of these oils for Rediviva bees is discussed in a co-evolutionary context.
- Dumri, Kanchana,Seipold, Lars,Schmidt, Juergen,Gerlach, Guenter,Doetterl, Stefan,Ellis, Allan G.,Wessjohann, Ludger A.
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- Chemical synthesis of burkholderia lipid a modified with glycosyl phosphodiester-linked 4-amino-4-deoxy-β-L-arabinose and its immunomodulatory potential
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Modification of the Lipid A phosphates by positively charged appendages is a part of the survival strategy of numerous opportunistic Gram-negative bacteria. The phosphate groups of the cystic fibrosis adapted Burkholderia Lipid A are abundantly esterified by 4-amino-4-deoxy-b-larabinose (β-L-Ara4N), which imposes resistance to antibiotic treatment and contributes to bacterial virulence. To establish structural features accounting for the unique pro-inflammatory activity of Burkholderia LPS we have synthesised Lipid A substituted by β-L-Ara4N at the anomeric phosphate and its Ara4N-free counterpart. The double glycosyl phosphodiester was assembled by triazolyl-tris-(pyrrolidinyl)phosphonium-assisted coupling of the β-L-Ara4N H-phosphonate to α-lactol of β(1→6) diglucosamine, pentaacylated with (R)-(3)-acyloxyacyl-and Alloc-protected (R)-(3)-hydroxyacyl residues. The intermediate 1,1'-glycosyl-H-phosphonate diester was oxidised in anhydrous conditions to provide, after total deprotection, β-L-Ara4N-substituted Burkholderia Lipid A. The β-L-Ara4N modification significantly enhanced the pro-inflammatory innate immune signaling of otherwise non-endotoxic Burkholderia Lipid A.
- Hollaus, Ralph,Ittig, Simon,Hofinger, Andreas,Haegman, Mira,Beyaert, Rudi,Kosma, Paul,Zamyatina, Alla
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supporting information
p. 4102 - 4114
(2015/10/19)
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- Asymmetric reduction of monoketo hexadecanoic acid methyl esters
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Methyl 2-,3-,6-,8-,14- and 15-keto hexadecanoates were reduced by using NaBH4 in presence of 1,2;5,6-di-O-isopropilydene-Dglucofuranose [DIPGH], R(+)-1,1′-binaphthyl-2,2′-diol [RBND] and pivalic acid [PA]. The reduction of 2- and 3-keto esters in the presence of (+)-1,1′-binaphthyl-2,2′-diol results in considerably higher stereoselectivities (95 % ee). Enantiometric excess (ee %) was determined by 1H and 13C NMR analyses using a shift reagent, Eu(tfc)3. Copyright
- Türker, Gülen,Yusufoglu, Ayse
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p. 1531 - 1535
(2013/06/26)
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- Termination of the structural confusion between plipastatin A1 and fengycin IX
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Plipastatin A1 and fengycin IX were experimentally proven to be identical compounds, while these had been considered as diastereomers due to the permutation of the enantiomeric pair of Tyr in most papers. The 1H NMR spectrum changed to become quite similar to that of plipastatin A1, when the sample which provided resembled spectrum of fengycin IX was treated with KOAc followed by LH-20 gel filtration. Our structural investigations disclosed that the structures of these molecules should be settled into that of plipastatin A1 by Umezawa (l-Tyr4 and d-Tyr10).
- Honma, Miho,Tanaka, Kazuaki,Konno, Katsuhiro,Tsuge, Kenji,Okuno, Toshikatsu,Hashimoto, Masaru
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experimental part
p. 3793 - 3798
(2012/08/28)
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- BETA-LACTONE COMPOUNDS
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The present invention provides compounds having the general structure A, or a pharmaceutically acceptable derivatives thereof: wherein R is an alkyl group, and R1 comprises at least one moiety selected from a group consisting of an alkyl, an alkenyl, an aryl, a heterocycle, hydroxyl, ester, amido, aldehyde, and a halogen.
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Page/Page column 11-12
(2009/05/28)
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- General enantioselective synthesis of butyrolactone natural products via ruthenium-SYNPHOS-catalyzed hydrogenation reactions
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Enantioselective syntheses of several paraconic acids have been achieved using catalyzed asymmetric hydrogenation of β-keto esters with SYNPHOS as a ligand. This strategy allowed the short synthesis of biologically active (-)-methylenolactocin 1, (-)-protolichesterinic acid 2, (-)-phaseolinic acid 3 and (+)-roccellaric acid 4.
- Blanc, Delphine,Madec, Jonathan,Popowyck, Florence,Ayad, Tahar,Phansavath, Phannarath,Ratovelomanana-Vidal, Virginie,Genet, Jean-Pierre
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p. 943 - 950
(2008/03/27)
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- Enantioselective Hydrogenation of β-Keto Esters using Chiral Diphosphine-Ruthenium Complexes: Optimization for Academic and Industrial Purposes and Synthetic Applications
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Enantioselective hydrogenation using chiral complexes between atropisomeric diphosphines and ruthenium is a powerful tool for producing chiral compounds. Using a simple and straightforward in situ catalyst preparation, the conditions were optimized using molecular hydrogen for both academic and industrial purposes. This led to the best conditions and the lowest catalytic ratio required for the pressure used. Hydrogenation of various β-keto esters was efficiently performed at atmospheric and higher pressures, leading to the use of very low catalyst-substrate ratios up to 1/20,000. Asymmetric hydrogenations were used in key-steps towards the total synthesis of corynomycolic acid, Duloxetine and Fluoxetine.
- Ratovelomanana-Vidal,Girard,Touati,Tranchier,Ben Hassine,Genet
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p. 261 - 274
(2007/10/03)
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- Synthesis of (S)- and (R)-3-hydroxyhexadecanoic acid
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Diol (R)-(+)-3 is prepared either from the hydroxyketone 2 by reduction with fermenting baker's yeast or by hydrolysis of the dioxolane (R)-(+)-1 which is available from dimethyl D-malate as starting material. (R)-(+)-3 could be converted stereoselectively into (R)-(+)-4. Reaction of (+)-4 with dodecylmagnesium bromide yielded the alcohol (S)-(-)-5 with >99% ee. Its acetylation gave (S)-(+)-6 and hydrogenolysis gave the primary alcohol (S)-(+)-7 which could be oxidized selectively to (S)-(+)-8 wih NaIO4/RuCl3. Alkaline hydrolysis of (+)-8 yielded 3-hydroxyhexadecanoic acid (S)-(+)-9 which could be esterified to give the methyl ester (S)-(+)-10 with >99% ee. Starting with the dioxolane (S)-(-)-1, derived from dimethyl L-malate, the 3-hydroxyhexadecanoic acid (R)-(-)-10 could be synthesised via the intemediates (S)-(-)-3, (S)-(-)-4, (R)-(+)-5, (R)-(-)-6, (R)-(-)-7 and (R)-(-)-8. Copyright (C) Elsevier Science Ltd.
- Jakob, Barbara,Voss, Gundula,Gerlach, Hans
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p. 3255 - 3262
(2007/10/03)
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- Asymmetric Reduction of Aliphatic Short- to Long-Chain β-Keto Acids by Use of Fermenting Bakers' Yeast
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Eleven β-keto acids, ranging from 3-oxobutanoic to 3-oxooctanoic acids, were reduced with fermenting bakers' yeast to the corresponding optically active β-hydroxy acids, which were isolated as the methyl esters.In all cases, the (R)-hydroxy acids were obtained in >/=98percent ee, except for 3-oxobutanoic acid, which afforded the (S)-hydroxy acid in 86percent ee.Inhibition of fermentation was observed for 3-oxoundecanoic to 3-oxotetradecanoic acids, leading to no reduction.Lowering of the substrate concentration was found to be appreciably effective in avoiding inhibition.
- Utaka, Masanori,Watabu, Hisashi,Higashi, Hiroshi,Sakai, Takashi,Tsuboi, Sadao,Torii, Sigeru
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p. 3917 - 3921
(2007/10/02)
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- Pahutoxin: Synthesis and Determination of Its Absolute Configuration
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Optically pure pahutoxin and its antipode were synthesized from (S)- and (R)-3-hydroxyhexadecanoic acids, which were obtained by the enantio-differentiating hydrogenation of methyl 3-oxohexadecanoate over asymmetrically modified Raney nickel catalyst.By an optical correlation with synthetic materials, dextrorotatory natural pahutoxin was determined to be of (S)-configuration.
- Yoshikawa, Masato,Sugimura, Takashi,Tai, Akira
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- The Preparation of Optically Pure 3-Hydroxyalkanoic Acid. The Enantioface-differentiating Hydrogenation of the C=O Double Bond with Modified Raney Nickel. XXXVII
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The enantioface-differentiating hydrogenation of methyl 3-oxoalkanoate (CH3(CH2)nCOCH2COOCH3, n=0, 6, 8, 10, 12) over the (R,R)-tartaric acid-NaBr-modified Raney nickel catalyst ((R,R)-TA-NaBr-MRNi) gave methyl (R)-3-hydroxyalkanoate (CH3(CH2)nCH(OH)CH2COOCH3, n=0, 6, 8, 10, 12) in an average optical yield of 85percent.After the methyl ester had been converted to dicyclohexylammonium salt of 3-hydroxyalkanoic acid, the salt was recrystallized three times from acetonitrile and then treated with acid to give optically pure (R)-3-hydroxyalkanoic acid (CH3(CH2)nCH(OH)CH2COOH, n=0, 6, 8, 10, 12) in a reasonable yield.From the hydrogenation product with (S,S)-TA-NaBr-MRNi, optically pure (S)-3-hydroxyalkanoic acid was obtained by the same process as above.
- Nakahata, Masaaki,Imaida, Motomasa,Ozaki, Hiroshi,Harada, Tadao,Tai, Akira
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p. 2186 - 2189
(2007/10/02)
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