617-54-9Relevant articles and documents
ELECTRO-ORGANIC REACTIONS ON ORGANIC ELECTRODES. PART 2. ELECTROCHEMICAL ASYMMETRIC REDUCTION OF CITRACONIC AND MESACONIC ACIDS ON OPTICALLY-ACTIVE POLY(AMINO ACID)-COATED ELECTRODES.
Nonaka,Abe,Fuchigami
, p. 2778 - 2783 (1983)
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.
Vicinal C,H Spin Coupling Constants in Determining Alkene Stereochemistry
Letcher, R. M.,Acheson, R. M.
, p. 316 - 318 (1981)
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.
Study of the Oxidative Cleavage Proposed in the Biogenesis of Transtaganolides/Basiliolides: Pyran-2-one Aromaticity-Mediated Regioselective Control and Biogenetic Implications
álvarez, José María,Jorge, Zacarías D.,Massanet, Guillermo M.
, (2020/03/05)
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.
A Br?nsted acidic, ionic liquid containing, heteropolyacid functionalized polysiloxane network as a highly selective catalyst for the esterification of dicarboxylic acids
Rajabi, Fatemeh,Wilhelm, Christian,Thiel, Werner R.
supporting information, p. 4438 - 4444 (2020/08/10)
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.
Asymmetric hydrogenation of maleic acid diesters and anhydrides
Bernasconi, Maurizio,Mueller, Marc-Andre,Pfaltz, Andreas
supporting information, p. 5385 - 5388 (2014/06/09)
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.
A fully integrated continuous-flow system for asymmetric catalysis: Enantioselective hydrogenation with supported ionic liquid phase catalysts using supercritical CO2 as the mobile phase
Hintermair, Ulrich,Francio, Giancarlo,Leitner, Walter
, p. 4538 - 4547 (2013/05/08)
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
A three-enzyme system involving an ene-reductase for generating valuable chiral building blocks
Mangan, David,Miskelly, Iain,Moody, Thomas S.
, p. 2185 - 2190,6 (2020/09/02)
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
A convenient procedure for bis-esterification of cyclic anhydrides
Jana, Amit Kumar,Karmakar, Raju,Dinda, Bidyut Kumar,Mitra, Prithiba,Ghosh, Ketaki,Karmakar, Rajdip,Mal, Dipakranjan
, p. 975 - 979 (2012/10/29)
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.
Nicotinamide-dependent Ene reductases as alternative biocatalysts for the reduction of activated alkenes
Durchschein, Katharina,Wallner, Silvia,MacHeroux, Peter,Schwab, Wilfried,Winkler, Thorsten,Kreis, Wolfgang,Faber, Kurt
supporting information, p. 4963 - 4968 (2013/01/14)
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
Synthesis and biological properties of tensyuic acids B, C, and E, and investigation of the optical purity of natural tensyuic acid B
Matsumaru, Takanori,Sunazuka, Toshiaki,Hirose, Tomoyasu,Ishiyama, Aki,Namatame, Miyuki,Fukuda, Takashi,Tomoda, Hiroshi,Otoguro, Kazuhiko,Omura, Satoshi
, p. 7369 - 7377 (2008/12/20)
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.
