- ELECTRO-ORGANIC REACTIONS ON ORGANIC ELECTRODES. PART 2. ELECTROCHEMICAL ASYMMETRIC REDUCTION OF CITRACONIC AND MESACONIC ACIDS ON OPTICALLY-ACTIVE POLY(AMINO ACID)-COATED ELECTRODES.
-
Influence of a number of electrolytic conditions on the asymmetric yield of methylsuccinic acid (2) formed in the electrochemical reduction of citraconic acid (1) on poly(amino acid)-coated electrodes was examined. The asymmetric yield was greatly affected by the conditions, while the absolute configuration of an excess enantiomer((S)-( minus )-2) remained unchanged even when a polymer with the reversed configuration of the monomer unit was used. The configuration of the excess enantiomer was also unchanged in the asymmetric reduction of mesaconic acid which is the geometrical isomer of 1.
- Nonaka,Abe,Fuchigami
-
-
Read Online
- Vicinal C,H Spin Coupling Constants in Determining Alkene Stereochemistry
-
Further examples of the diagnostic vicinal C,H coupling constants of trisubstituted alkenes are reported, and the application of the method confirms the structures of four dimethyl acetylenedicarboxylate adducts.
- Letcher, R. M.,Acheson, R. M.
-
-
Read Online
- A Br?nsted acidic, ionic liquid containing, heteropolyacid functionalized polysiloxane network as a highly selective catalyst for the esterification of dicarboxylic acids
-
A Br?nsted acidic, ionic liquid containing, heteropolyanion functionalized polysiloxane network was formed by self-condensation of dodecatungstophosphoric acid and a zwitterionic organosilane precursor containing both imidazolinium and sulfonate groups. The resulting hybrid material POS-HPA-IL was investigated as a catalyst for the selective esterification of dicarboxylic acids.
- Rajabi, Fatemeh,Wilhelm, Christian,Thiel, Werner R.
-
supporting information
p. 4438 - 4444
(2020/08/10)
-
- Study of the Oxidative Cleavage Proposed in the Biogenesis of Transtaganolides/Basiliolides: Pyran-2-one Aromaticity-Mediated Regioselective Control and Biogenetic Implications
-
The synthetic feasibility of the oxidative cleavage: epoxidation of 7-O-geranylscopoletin followed by electrocyclic ring-opening, proposed in the biogenesis of transtaganolides/basiliolides is studied. Unlike the proposed pericyclic reactions, this pathway has not yet been addressed. Three synthetic strategies have been tested consisting of: i) Baeyer–Villiger oxidation of p-quinoids, ii) hydrolysis of quinone monoketals, or iii) direct fragmentation by using oxygen donors. Oxidation of the benzene ring of hydroxylated coumarins has been achieved using peroxyacids, but cleavage took place between undesired positions. The aromaticity conservation of the pyran-2-one cycle during oxidation is the controlling factor of these observed regioselectivities. The use of a 4,5-dihydroxy-2-methoxycinnamate model, in which the pyran-2-one ring does not exert influence on oxidation, has allowed the design of a synthetic sequence toward an analogue of the natural pyran-2-one isolated from Thapsia transtagana, key in the biogenesis. Mechanistic proposals for the obtained results as well as their biogenetic implications are raised.
- álvarez, José María,Jorge, Zacarías D.,Massanet, Guillermo M.
-
-
- Asymmetric hydrogenation of maleic acid diesters and anhydrides
-
Asymmetric hydrogenation of maleic and fumaric acid derivatives with iridium catalysts based on N,P ligands provides an efficient route to chiral enantioenriched succinates. A new catalyst derived from a 2,6-difluorophenyl- substituted pyridine-phosphinite ligand was developed and enables the conversion of a wide range of 2-alkyl and 2-arylmaleic acid diesters into the corresponding succinates in high enantiomeric purity. Mixtures of cis/trans substrates can be hydrogenated in an enantioconvergent fashion with high enantioselectivity, and further enhances the scope of this transformation. The products are valuable chiral building blocks with a structural motif found in many bioactive compounds, such as metalloproteinase inhibitors. An attractive enantioselective route to 2-alkyl- and 2-aryl-substituted succinic acid derivatives is opened up by the asymmetric hydrogenation of maleic and fumaric acid derivatives, using the new catalyst [Ir(cod)L]BArF, derived from a 2,6-difluorophenyl-substituted pyridine-phosphinite ligand. The products are valuable chiral building blocks having a structural motif found in many bioactive compounds. cod=1,5-cyclooctadiene.
- Bernasconi, Maurizio,Mueller, Marc-Andre,Pfaltz, Andreas
-
supporting information
p. 5385 - 5388
(2014/06/09)
-
- A fully integrated continuous-flow system for asymmetric catalysis: Enantioselective hydrogenation with supported ionic liquid phase catalysts using supercritical CO2 as the mobile phase
-
A continuous-flow process based on a chiral transition-metal complex in a supported ionic liquid phase (SILP) with supercritical carbon dioxide (scCO 2) as the mobile phase is presented for asymmetric catalytic transformations of low-volatility organic substrates at mild reaction temperatures. Enantioselectivity of >99 % ee and quantitative conversion were achieved in the hydrogenation of dimethylitaconate for up to 30 h, reaching turnover numbers beyond 100 000 for the chiral QUINAPHOS-rhodium complex. By using an automated high-pressure continuous-flow setup, the product was isolated in analytically pure form without the use of any organic co-solvent and with no detectable catalyst leaching. Phase-behaviour studies and high-pressure NMR spectroscopy assisted the localisation of optimum process parameters by quantification of substrate partitioning between the IL and scCO2. Fundamental insight into the molecular interactions of the metal complex, ionic liquid and the surface of the support in working SILP catalyst materials was gained by means of systematic variations, spectroscopic studies and labelling experiments. In concert, the obtained results provided a rationale for avoiding progressive long-term deactivation. The optimised system reached stable selectivities and productivities that correspond to 0.7 kg L-1 h -1 space-time yield and at least 100 kg product per gram of rhodium, thus making such processes attractive for larger-scale application. Copyright
- Hintermair, Ulrich,Francio, Giancarlo,Leitner, Walter
-
p. 4538 - 4547
(2013/05/08)
-
- Nicotinamide-dependent Ene reductases as alternative biocatalysts for the reduction of activated alkenes
-
Four NAD(P)H-dependent non-flavin ene reductases have been investigated for their ability to reduce activated C=C bonds in an asymmetric fashion by using 20 structurally diverse substrates. In comparison with flavin-dependent Old Yellow Enzyme homologues, a higher degree of electronic activation was required, because the best activities were obtained with enals and nitroalkenes rather than enones and carboxylic esters. Although FaEO from Fragaria x ananassa (strawberry) and its homologue SlEO from Solanum lycopersicum (tomato) exhibited a narrow substrate spectrum, progesterone 5β-reductase (At5β-StR) from Arabidopsis thaliana (thale cress) and leukotriene B4 12-hydroxydehydrogenase (LTB4DH/PGR) from Rattus norvegicus (rat) appear to be promising candidates, in particular for the asymmetric bioreduction of open-chain enals, nitroalkenes and α,β-unsaturated γ-butyrolactones. Competing nitro reduction and non-enzymatic Weitz-Scheffer epoxidation were largely suppressed. Electronically activated alkenes have been stereoselectively reduced by using a single-enzyme-cofactor system employing nicotinamide-dependent non-flavin ene reductases. Copyright
- Durchschein, Katharina,Wallner, Silvia,MacHeroux, Peter,Schwab, Wilfried,Winkler, Thorsten,Kreis, Wolfgang,Faber, Kurt
-
supporting information
p. 4963 - 4968
(2013/01/14)
-
- A three-enzyme system involving an ene-reductase for generating valuable chiral building blocks
-
The use of ene-reductase (ERED) enzymes for the asymmetric reduction of olefins offers a green, renewable alternative to metal-catalysed asymmetric reduction. We report herein the first example of an ERED-catalysed enantiospecific reduction carried out at large scale using a carbonyl reductase (CRED) enzyme in the cofactor recycle. This reaction has been paired with a hydrolase-mediated regioselective ester hydrolysis to generate a valuable chiral building block using a straightforward one-pot process. Copyright
- Mangan, David,Miskelly, Iain,Moody, Thomas S.
-
p. 2185 - 2190,6
(2020/09/02)
-
- A convenient procedure for bis-esterification of cyclic anhydrides
-
Aromatic and aliphatic cyclic anhydrides are chemoselectively and conveniently transformed to the corresponding diesters by the use of DBU and appropriate alkyl/allyl halides. This bis-esterification reaction has been exemplified mostly with dimethyl esters. But in some cases, mixed dialkyl esters are also prepared.
- Jana, Amit Kumar,Karmakar, Raju,Dinda, Bidyut Kumar,Mitra, Prithiba,Ghosh, Ketaki,Karmakar, Rajdip,Mal, Dipakranjan
-
p. 975 - 979
(2012/10/29)
-
- Synthesis and biological properties of tensyuic acids B, C, and E, and investigation of the optical purity of natural tensyuic acid B
-
The first, concise total synthesis of (±)-tensyuic acids B, C, and E, using chemoselective formal SN2′ type Grignard reactions and selective esterification, is described. In addition, the optical purity of natural (±)-tensyuic acid B was determined using Chirabite-AR. Synthetic tensyuic acids, together with their intermediate compounds, were found to possess useful bioactive properties, with some of them showing potent activity against Trypanosoma brucei brucei strain GUTat 3.1.
- Matsumaru, Takanori,Sunazuka, Toshiaki,Hirose, Tomoyasu,Ishiyama, Aki,Namatame, Miyuki,Fukuda, Takashi,Tomoda, Hiroshi,Otoguro, Kazuhiko,Omura, Satoshi
-
p. 7369 - 7377
(2008/12/20)
-
- Asymmetric bioreduction of activated C=C bonds using Zymomonas mobilis NCR enoate reductase and old yellow enzymes OYE 1-3 from yeasts
-
The asymmetric bioreduction of C=C-bonds bearing an electron-withdrawing group, such as an aldehyde, ketone, imide, nitro, carboxylic acid, or ester moiety by a novel enoate reductase from Zymomonas mobilis and Old Yellow Enzymes OYE 1-3 from yeasts furnished the corresponding saturated products in up to >99%ee. Depending on the substrate type, stereocontrol was achieved by variation of the substrate structure, by switching the (E/Z) geometry of the alkene or by choice of the appropriate enzyme. This substrate- or enzyme-based stereocontrol allowed access to the opposite enantiomeric products. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Hall, Melanie,Stueckler, Clemens,Hauer, Bernhard,Stuermer, Rainer,Friedrich, Thomas,Breuer, Michael,Kroutil, Wolfgang,Faber, Kurt
-
supporting information; experimental part
p. 1511 - 1516
(2009/04/11)
-
- Stereocomplementary bioreduction of α,β-unsaturated dicarboxylic acids and dimethyl esters using enoate reductases: Enzyme- And substrate-based stereocontrol
-
Asymmetric bioreduction of α,β-unsaturated dicarboxylic acids, such as 2-methylmaleic/fumaric and 2-methylenesuccinic acid, as well as the corresponding dimethyl esters, using three cloned enoate reductases furnished 2-methylsuccinic acid or dimethyl 2-methylsuccinate, respectively. Opposite stereoisomeric products were obtained in up to >99% ee either by choice of the enzyme or by using E/Z-configurated substrates. Cofactor-recycling systems (NADH/FDH/formate, NADH/GDH/glucose or NADPH/G6PDH/glucose-6-phosphate) only worked in presence of a divalent metal ion, such as Ca2+, Mg 2+, or Zn2+.
- Stueckler, Clemens,Hall, Melanie,Ehammer, Heidemarie,Pointner, Eva,Kroutil, Wolfgang,Macheroux, Peter,Faber, Kurt
-
p. 5409 - 5411
(2008/09/18)
-
- A hemiterpene glucoside as a probing deterrent of the bean aphid, Megoura crassicauda, from a non-host vetch, Vicia hirsuta
-
The bean aphid, Megoura crassicauda Mordvilko, feeds selectively on plants belonging to the genus Vicia (Fabaceae). However, it never infests the tiny vetch, V. hirsuta (L.) Gray. The aphid appeared to discriminate between host and non-host plants by tasting specific chemicals during penetration of its stylet into the plant tissues. The aphid, after being stimulated by specific probing stimulants, deposited characteristic proteinous stylet sheaths through a parafilm membrane, which has one side in contact with an extract solution of Vicia angustifolia. However, an addition of a V. hirsuta extract to the medium strongly inhibited the salivary sheath formation. A specific probing deterrent was isolated from a V. hirsuta extract by monitoring the inhibitory effect, and identified as (E)-2-methyl-2-butene-1,4-diol 4-O-β-D-glucopyranoside. A mixture of the glycoside and the stimulatory V. angustifolia fraction in the same equivalency found in plants significantly decreased the probing activity in M. crassicauda. Since the stylet insertion process is a crucial step for the aphid's settlement on a plant, the glycoside seems to act as an effective chemical barrier for V. hirsuta.
- Ohta, Naohiro,Mori, Naoki,Kuwahara, Yasumasa,Nishida, Ritsuo
-
p. 584 - 588
(2008/02/09)
-
- Synthesis of potassium 2,3,4-trihydroxy-2-methylbutanoate: A leaf-closing substance of Leucaena leucocephalam
-
Starting from citraconic anhydride (2), a six step synthesis of leaf closing substance (±)-erythro potassium 2,3,4-trihydroxy-2-methyl- butanoate (1) has been described with 29% overall yield via diesterification, OsO4-dihydroxylation, acetonide protection, regioselective mono hydrolysis of unhindered ester moiety, borane-dimethylsulfide induced chemoselective reduction of carboxylic group and hydrolysis pathway. Surprisingly, the sodium borohydride reduction of monoester 5 and lithium borohydride reduction of 11 furnished the undesired regioisomer 7.
- Gogoi, Sanjib,Argade, Narshinha P.
-
p. 9093 - 9097
(2007/10/03)
-
- Identification and quantification of aerosol polar oxygenated compounds bearing carboxylic or hydroxyl groups. 1. Method development
-
In this study, a new analytical technique was developed for the identification and quantification of multifunctional compounds containing simultaneously at least one hydroxyl or one carboxylic group, or both. This technique is based on derivatizing first the carboxylic group(s) of the multifunctional compound using an alcohol (e.g., methanol, 1-butanol) in the presence of a relatively strong Lewis acid (BF3) as a catalyst. This esterification reaction quicldy and quantitatively converts carboxylic acids to their ester forms. The second step is based on silylation of the ester compounds using bis(trimethylsilyl) trifluoroacetamide (BSTFA) as the derivatizing agent. For compounds bearing ketone groups in addition to carboxylic and hydroxyl groups, a third step was used based on PFBHA derivatization of the carbonyls. Different parameters including temperature, reaction time, and effect due to artifacts were optimized. A GC/MS in EI and in methane-CI mode was used for the analysis of these compounds. The new approach was tested on a number of multifunctional compounds. The interpretation of their EI (70 eV) and CI mass spectra shows that critical information is gained leading to unambiguous identification of unknown compounds. For example, when derivatized only with BF3-methanol, their mass spectra comprise primary ions at m/z M .+ + 1, M.+ + 29, and M.- - 31 for compounds bearing only carboxylic groups and M.- + 1, M.+ + 29, M.+ - 31, and M+. - 17 for those bearing hydroxyl and carboxylic groups. However, when a second derivatization (BSTFA) was used, compounds bearing hydroxyl and carboxylic groups simultaneously show, in addition to the ions observed before, ions at m/z M.+ + 73, M .+ - 15, M.+ - 59, M.+ - 75, M.+ - 89, and 73. To the best of our knowledge, this technique describes systematically for the first time a method for identifying multifunctional oxygenated compounds containing simultaneously one or more hydroxyl and carboxylic acid groups.
- Jaoui,Kleindienst,Lewandowski,Edney
-
p. 4765 - 4778
(2007/10/03)
-
- A facile synthesis of natural products chaetomellic acid A and 1,7(Z)-nonadecadiene-2,3-dicarboxylic acid
-
Synthesis of recently isolated bioactive natural products chaetomellic acid A anhydride (1) and a novel 1,7- (Z)-nonadecadiene-2,3-dicarboxylic acid (2) have been described. Chemoselective carbon-carbon SN2′ coupling reactions of appropriate Grignard reagents with dimethyl bromomethylfumarate (7) in diethyl ether in the presence of HMPA at room temperature furnished the corresponding diesters 8 and 15 in 60-62% yields. The formed diesters 8 and 15 on hydrolysis gave respectively the corresponding desired diacids 9 and 2 in quantitative yields. Acetic anhydride induced ring closure of diacids 9 and 2 respectively gave the chaetomellic acid A anhydride (1) and isochaetomellic acid B anhydride (16) with 38-39% overall yields in five steps.
- Kar, Anirban,Argade, Narshinha P.
-
p. 7131 - 7134
(2007/10/03)
-
- A rapid entry to natural and unnatural disubstituted maleic anhydrides
-
Copper-mediated tandem vicinal difunctionalisation of dimethyl acetylenedicarboxylate, followed in selected cases by oxidation of one of the substituents, provides a versatile and rapid route to a variety of natural and unnatural disubstituted maleic anhydrides.
- Adlington, Robert M.,Baldwin, Jack E.,Cox, Rhona J.,Pritchard, Gareth J.
-
p. 820 - 822
(2007/10/03)
-
- FACILE ESTERIFICATION OF CARBOXYLIC ACIDS WITH ORGANOPHOSPHORUS REAGENTS. NOVEL APPLICATION OF ALKYLPHOSPHORIC ESTERS (APE)
-
A mixture of alkyl phosphate esters (APE) obtained from P4O10 and alkanols taken in 1:6 mole ratio is an excellent esterification reagent for several classes of carboxylic acids.This new reagent offers several advantages compared to conventional reagents.
- Balasubramaniyan, V.,Bhatia, V. G.,Wagh, S. B.
-
p. 1475 - 1485
(2007/10/02)
-
- Method for preparation of citraconic acid and derivatives thereof
-
A method of preparing citraconic acid and derivatives thereof comprising reacting methylsuccinic acid and derivatives thereof (such as an acid halide, an acid anhydride, a monoester and a diester) with chlorine in the absence of or in the presence of a catalyst at a temperature ranging from about 100° to 500°C.
- -
-
-
