- Spirastrellolides C to G: Macrolides obtained from the marine sponge Spirastrella coccinea
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(Chemical Equation Presented) Five new macrolides, spirastrellolides C (3) to G (7), have been isolated from extracts of the marine sponge Spirastrella coccinea collected in Dominica. Their structures have been elucidated by a combination of spectroscopic analysis and chemical transformations.
- Williams, David E.,Keyzers, Robert A.,Warabi, Kaoru,Desjardine, Kelsey,Riffell, Jenna L.,Roberge, Michel,Andersen, Raymond J.
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Read Online
- Constituents of Agave americana and Agave barbadensis
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An investigation of Agave americana and Agave barbadensis resulted in the isolation of a new homoisoflavanoid, 7-hydroxy-3-(4-methoxybenzyl)-chroman (3), together with known compounds 7-hydroxy-3-(4-methoxybenzyl)-chroman-4-one (1), 5,7-dihydroxy-3-(4-methoxybenzyl)-chroman-4-one (2), cantalasaponin-1 (4), and 2-hydroxy-butanedioic acid-1-methyl ester (5).
- Tinto,Simmons-Boyce,McLean,Reynolds
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Read Online
- Total Synthesis of (+)-Cornexistin
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Herein, we describe the first total synthesis of (+)-cornexistin as well as its 8-epi-isomer starting from malic acid. The robust and scalable route features a Nozaki–Hiyama–Kishi reaction, an auxiliary-controlled syn-Evans-aldol reaction, and a highly efficient intramolecular alkylation to form the nine-membered carbocycle. The delicate maleic anhydride moiety of the nonadride skeleton was constructed from a β-keto nitrile. The developed route enabled the synthesis of 165 mg (+)-cornexistin.
- Barber, David M.,Magauer, Thomas,Steinborn, Christian,Wildermuth, Raphael E.
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supporting information
p. 17282 - 17285
(2020/08/21)
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- USE OF PHENOLIC COMPOUNDS FROM OLEA EUROPAEA
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A series of phenolic compounds with similar inhibitory COX-1 and COX-2 properties as oleocanthal and oleuropein is described here. The phenolic compounds disclosed here were also found to be MAO and LSD-1 inhibitors. Also provided are methods of using these phenolic compounds in various formulations and compositions including food additives, pharmaceuticals, cosmetics, and animal repellants.
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Page/Page column 48-49
(2019/02/25)
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- CHIRAL BINUCLEAR METAL COMPLEXES FOR STEREOSELECTIVE GLYCOSIDE HYDROLYSIS OF SACCHARIDES
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Disclosed herein is a class of chiral binuclear metal complexes for stereoselective glycoside hydrolysis of saccharides, and more particular chiral binuclear transition metal complex catalysts that discriminate epimeric glycosides and α- and β-glycosidic bonds of saccharides in aqueous solutions at near physiological pHs. The chiral binuclear metal complexes include a Schiff-base-type ligand derived from a chiral diamino building block, and a binuclear transition metal core, each which can be varied for selectivity. The metal core is a Lewis-acidic metal ion, such as copper, zinc, lanthanum, iron and nickel. The Schiff-base may be a reduced or non-reduced Schiff-base derived from aliphatic linear, aliphatic cyclic diamino alcohols or aromatic aldehydes. The ligand can be a penta- or heptadentate ligand derived from pyridinecarbaldehydes, benzaldehydes, linear or cyclic diamines or diamino alcohols.
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Paragraph 0044; 0045
(2017/10/13)
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- Binuclear copper(II) complexes discriminating epimeric glycosides and α- And β-glycosidic bonds in aqueous solution
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Two chiral binuclear copper(II) complexes were synthesized and characterized for the first time as efficient chemoselective catalysts for the hydrolysis of aryl glycosides and disaccharides in aqueous solution at near neutral pH. Under these conditions, discrimination of epimeric aryl α-glycopyranosides was observed by both 29-fold different reaction rates and 3-fold different proficiency of the catalyst. Additionally, large differentiation of the nature of α- and β-glycosidic bond in aryl glycosides as model compounds is apparent, but also noted in selected disaccharides. The influence of the chirality of the complexes and the role of the configuration of the carbohydrate upon interaction with the catalyst is discussed in detail. Lastly, a putative mechanism for the metal complex-catalyzed hydrolysis is derived from the experimental evidence pointing at deprotonation of the hydroxyl group at C-2 as a pre-requisite for glycoside hydrolysis.
- Striegler, Susanne,Fan, Qiu-Hua,Rath, Nigam P.
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p. 349 - 364
(2016/05/24)
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- Sesquiterpene dimers esterified with diverse small organic acids from the seeds of Sarcandra glabra
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11 new sesquiterpene dimers, sarglabolides A-K (1-11), and five known ones were isolated from the seeds of Sarcandra glabra. Their structures were elucidated by spectroscopic data analysis and chemical evidence. Sarglabolide A (1) was verified to exclusively possess a seventeen-membered macrocyclic ester ring formed by the scaffold of the sesquiterpene dimer and small organic acids, different from the eighteen-membered rings of the other reported analogues. The chiral small organic acid moieties were assigned to l-malic acid, d-malic acid, and d-tartaric acid based on the combination of spectroscopy, chemical derivatization and HPLC analysis. Dimers 1, 12 and 13 can significantly inhibit NO production in LPS-induced macrophages with IC50 values at 3.04, 4.65 and 2.33 μmol/L, respectively.
- Wang, Peng,Luo, Jun,Zhang, Yang-Mei,Kong, Ling-Yi
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p. 5362 - 5370
(2015/07/15)
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- Concise total synthesis of (-)-erinapyrone b from d-(+)-malic acid
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A convenient and facile enantioselective synthesis of (-)-erinapyrone B from commercially available D-(+)-malic acid has been achieved in seven steps. One of the key steps in this synthesis was the one-pot reaction of palladium(II)-mediated Wacker-type oxidative cyclization in the presence of a catalytic amount of p-toluenesulphonic acid (p-TsOH) which has been found to be effective for the preparation of enantiopure 2,3-dihydro-4H-pyran-4-one from the corresponding enantiopure β-hydroxyenone via enantio-enriched diketohydroxy intermediate.
- Samala, Ramakrishna,Gurram, Venkateshwarlu,Patro, Balaram,Pottabathini, Narender,Mukkanti
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supporting information
p. 500 - 506
(2014/01/23)
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- Palladium phthalocyaninesulfonate functionalized mesoporous polymer: A highly efficient photocatalyst for degradation of 4-chlorophenol under visible light irradiation
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A novel sulfonated palladium phthalocyanine (PdPcS) modified FDU-15 mesoporous polymer (FDU-PdPcS) has been prepared by rationally chemical modification process. The PdPcS molecules were highly dispersed inside the confined mesopores, and were further stabilized through a π-π interaction with mesopolymer, which may prevent the PdPcS molecules from agglomerating and deactivating in photodegradation reactions. The physicochemical properties of thus prepared FDU-PdPcS material were characterized by XRD, N2 adsorption-desorption, UV-vis and inductively coupled plasma techniques. FDU-PdPcS proved to be highly efficient heterogeneous photocatalyst for the degradation of 4-chlorophenol (4-CP) in the presence of H2O 2 under visible light irradiation. The photodegradation of 4-CP with an initial concentration 0.6 mM was completed within 5 h at pH 11 using a dose of 0.2 g/L of the 0.12 wt% FDU-PdPcS photocatalyst. The photodegradation intermediates were identified by GC-MS. A possible mechanism involved in the photodegradation of 4-CP has also been discussed.
- Xing, Rong,Wu, Lin,Fei, Zhenghao,Wu, Peng
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- The formal total synthesis of FR252921-An immunosuppressant
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The formal total synthesis of FR252921 is described. The key steps include the preparation of three fragments starting from 1,4-butanediol, (R)-malic acid, and prenol, respectively, followed by two consecutive peptide couplings of the three fragments. Other key steps involve an allene-type rearrangement or enyne isomerization to install the triene moiety, a Seebach methylation, a Julia olefination to construct the trisubstituted diene unit, and an enzymatic resolution strategy to generate the C-18 stereocenter.
- Yadav,Sengupta, Sandip
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p. 376 - 388
(2013/03/13)
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- Studies directed towards the total synthesis of koshikalide: Stereoselective synthesis of the macrocyclic core
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The stereoselective synthesis of the macrolactone core of the natural product koshikalide is described. Starting with readily available 1,4-butanediol and malic acid as synthons, our synthetic strategy involved the reiterative application of Gilman's reaction, Swern oxidation and Sharpless asymmetric epoxidation to establish the required stereocentres. Other key steps in the synthesis include Negishi cross coupling and Horner-Wadsworth-Emmons (HWE) reactions for construction of the main fragments. The 14-membered lactone ring was prepared by a selective Mitsunobu macrolactonization approach.
- Venkanna, Arramshetti,Sreedhar, Eppakayala,Siva, Bandi,Babu, Katragadda Suresh,Prasad, Kothakonda Rajendra,Rao, Janaswamy Madhusudana
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p. 1010 - 1022
(2013/09/23)
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- An approach to the chemotaxonomic differentiation of two European Dog's mercury species: Mercurialis annua L. and M. perennis L.
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Mercurialis annua and M. perennis are medicinal plants used in complementary medicine. In the present work, analytical methods to allow a chemotaxonomic differentiation of M. annua and M. perennis by means of chemical marker compounds were established. In addition to previously published compounds, the exclusive presence of pyridine-3-carbonitrile and nicotinamide in CH2Cl2 extracts obtained from the herbal parts of M. annua was demonstrated by GC/MS. Notably, pyridine-3-carbonitrile was identified for the first time as a natural product. Further chromatographic separation of the CH2Cl2 extracts via polyamide yielded a MeOH fraction exhibiting a broad spectrum of side-chain saturated n-alkylresorcinols. While the n-alkylresorcinol pattern was similar for both plant species, some specific differences were observed for particular n-alkylresorcinol homologs. Finally, the investigation of H2O extracts by LC/MS/MS revealed the presence of depside constituents. Whereas, in M. perennis, a mixture of mercurialis acid (=(2R)-[(E)-caffeoyl]-2-oxoglutarate) and phaselic acid (=(E)-caffeoyl-2-malate) could be detected, in M. annua solely phaselic acid was found. By comparison with synthesized enantiomerically pure (2R)- and (2S)-phaselic acids, the configuration of the depside could be determined as (2S) in M. annua and as (2R) in M. perennis.
- Lorenz, Peter,Duckstein, Sarina,Conrad, Juergen,Knoedler, Matthias,Meyer, Ulrich,Stintzing, Florian C.
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experimental part
p. 282 - 297
(2012/05/04)
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- Investigating the role of the hydroxyl groups of substrate erythrose 4-phosphate in the reaction catalysed by the first enzyme of the shikimate pathway
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3-Deoxy-d-arabino-heptulosonate 7-phosphate (DAH7P) synthase catalyses the first step of the shikimate pathway, which is responsible for the biosynthesis of aromatic amino acids in microorganisms and plants. This enzyme catalyses an aldol reaction between phosphoenolpyruvate and d-erythrose 4-phosphate to generate DAH7P. Both 2-deoxyerythrose 4-phosphate and 3-deoxyerythrose 4-phosphate were synthesised and tested as alternative substrates for the enzyme. Both compounds were found to be substrates for the DAH7P synthases from Escherichia coli, Pyrococcus furiosus and Mycobacterium tuberculosis, consistent with an acyclic mechanism for the enzyme for which neither C2 nor C3 hydroxyl groups are required for catalysis. The enzymes all showed greater tolerance for the loss of the C2 hydroxyl group than the C3 hydroxyl group.
- Tran, David,Pietersma, Amy L.,Schofield, Linley R.,Rost, Matthias,Jameson, Geoffrey B.,Parker, Emily J.
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supporting information; experimental part
p. 6838 - 6841
(2012/01/03)
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- Novel glucagon receptor antagonists with improved selectivity over the glucose-dependent insulinotropic polypeptide receptor
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Optimization of a new series of small molecule human glucagon receptor (hGluR) antagonists is described. In the process of optimizing glucagon receptor antagonists, we counter-screened against the closely related human gastric inhibitory polypeptide receptor (hGIPR), and through structure activity analysis, we obtained compounds with low nanomolar affinities toward the hGluR, which were selective against the hGIPR and the human glucagon-like peptide-1 receptor (hGLP-1R). In the best cases, we obtained a >50 fold selectivity for the hGluR over the hGIPR and a >1000 fold selectivity over the hGLP-1R. A potent and selective glucagon receptor antagonist was demonstrated to inhibit glucagon-induced glycogenolysis in primary rat hepatocytes as well as to lower glucagon-induced hyperglycemia in Sprague - Dawley rats. Furthermore, the compound was shown to lower blood glucose in the ob/ob mouse after oral dosing.
- Kodra, János T.,J?rgensen, Anker Steen,Andersen, Birgitte,Behrens, Carsten,Brand, Christian Lehn,Christensen, Inger Th?ger,Guldbrandt, Mette,Jeppesen, Claus Bekker,Knudsen, Lotte B.,Madsen, Peter,Nishimura, Erica,Sams, Christian,Sidelmann, Ulla G.,Pedersen, Raymon A.,Lynn, Francis C.,Lau, Jesper
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experimental part
p. 5387 - 5396
(2009/07/01)
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- MODULATORS OF CYSTIC FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR
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The present invention relates to modulators of cystic fibrosis Transmembrane Conductance Regulator ("CFTR"), compositions thereof, and methods therewith. The present invention also relates to methods of treating CFTR mediated diseases using such modulators.
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Page/Page column 67
(2010/11/26)
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- A method for preparation of unnatural (R)-malic acid derivatives with phenylsilanes
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Enantiomerically pure unnatural (R)-malic acid derivatives were prepared from (R,R)-tartrates via their cyclic thionocarbonate derivatives using phenylsilanes in high isolated yields.
- Cho, Dae Hyan,Song, Seong Ho,Jang, Doo Ok
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p. 515 - 519
(2007/10/03)
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- Synthesis and SAR of thrombin inhibitors incorporating a novel 4-amino-morpholinone scaffold: Analysis of X-ray crystal structure of enzyme inhibitor complex
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A 4-amino-2-carboxymethyl-3-morpholinone structural motif derived from malic acid has been used to mimic D-Phe-Pro in the thrombin inhibiting tripeptide D-Phe-Pro-Arg. The arginine in D-Phe-Pro-Arg was replaced by the more rigid P1 truncated p-amidinobenzylamine (Pab). These new thrombin inhibitors were used to probe the inhibitor binding site of α-thrombin. The best candidate in this series of thrombin inhibitors exhibits an in vitro IC50 of 0.130 μM. Interestingly, the stereochemistry of the 4-amino-2-carboxymethyl-3-morpholinone motif is reversed for the most active compounds compared to that of a previously reported 2-carboxymethyl-3-morpholinone series. The X-ray crystal structure of the lead inhibitor cocrystallized with α-thrombin is discussed.
- Nilsson, Jonas W.,Kvarnstr?m, Ingemar,Musil, Djordje,Nilsson, Ingemar,Samulesson, Bertil
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p. 3985 - 4001
(2007/10/03)
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- Glucagon antagonists/inverse agonists
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A novel class of compounds, which act to antagonize the action of the glucagon hormone on the glucagon receptor. Owing to their antagonizing effect of the glucagon receptor the compounds may be suitable for the treatment and/or prevention of any diseases and disorders, wherein a glucagon antagonistic action is beneficial, such as hyperglycemia, Type 1 diabetes, Type 2 diabetes, disorders of the lipid metabolism, such as dyslipidemia, and obesity.
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- C(2)-symmetric Sc(III)-complexes as chiral Lewis acids. Catalytic enantioselective aldol additions to glyoxylate esters.
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Cationic Lewis acid complexes [Sc(pyridyl-bis(oxazolinyl)](Cl(2))SbF(6) 1a and 1b catalyze aldol reactions with ethyl glyoxylate with enantioselectivities ranging from 90 to 99% ee and syn reaction diastereoselections ranging from 90:10 to 95:5. [reaction: see text]
- Evans, David A,Masse, Craig E,Wu, Jimmy
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p. 3375 - 3378
(2007/10/03)
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- Novel morpholinone-based D-Phe-Pro-Arg mimics as potential thrombin inhibitors: design, synthesis, and X-ray crystal structure of an enzyme inhibitor complex.
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A morpholinone structural motif derived from D(+)- and L(-)-malic acid has been used as a mimic of D-Phe-Pro in the thrombin inhibiting tripeptide D-Phe-Pro-Arg. In place of Arg the more rigid P1 truncated p-amidinobenzylamine (Pab) or 2-amino-5-aminomethyl-3-methyl-pyridine have been utilized. The synthetic strategy developed readily delivers these novel thrombin inhibitors used to probe the alpha-thrombin inhibitor binding site. The best candidate in this series of thrombin inhibitors exhibits an in vitro IC(50) of 720 nM. The X-ray crystal structure of this candidate co-crystallized with alpha-thrombin is discussed.
- Dahlgren, Anders,Johansson, Per Ola,Kvarnstroem, Ingemar,Musil, Djordje,Nilsson, Ingemar,Samuelsson, Bertil
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p. 1829 - 1839
(2007/10/03)
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- Facile synthesis of enantiopure (R)-malates
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(R)-Malates were synthesized from cyclic thionocarbonates of (R,R)- tartrates by reacting with hypophosphorous acid in high isolated yields.
- Jang, Doo Ok,Song, Seong Ho
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p. 247 - 249
(2007/10/03)
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- Enzymatic methods for the preparation of enantiopure malic and aspartic acid derivatives in organic solvents
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The kinetic resolution of malic and aspartic acid diesters as well as of its N-butanoyl dimethyl ester by highly regioselective lipases and acylase I enzymes were studied. Candida antarctica lipase A on Celite catalyzed the enantioselective acylation of the hydroxyl and amino groups. Acylase I from Aspergillus melleus and Candida antarctica lipase B catalyzed the enantioselective alcoholyses of the ester groups at the α- and β-positions, respectively. (C) 1999 Elsevier Science Ltd.
- Liljeblad, Arto,Kanerva, Liisa T.
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p. 4405 - 4415
(2007/10/03)
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- Baker's Yeast-Mediated Reductions of α-Keto Esters and an α-Keto-β-Lactam. Two Routes to the Paclitaxel Side Chain
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Baker's yeast (Saccharomyces cerevisiae) has been used to reduce a series of alkyl esters derived from pyruvate and benzoylformate. Both the yield and enantioselectivities of these reductions were maximized when methyl esters were used, and the (R)-alcohols were isolated in all instances. Yeast-mediated ester hydrolysis was a significant side reaction for products derived from long-chain alcohols. In the case of ethyl benzoylformate, the addition of methyl vinyl ketone increased the enantioselectivity of the reduction. These reductions were applied to two syntheses of the paclitaxel C13 side chain [(2R,3S)-N-benzoyl-3-phenylisoserine]. In the first, a racemic α-keto-β-azido ester was reduced by whole cells of Baker's yeast to afford a diastereomeric mixture in which the desired product predominated and could be isolated chromatographically. In the second, an easily synthesized α-keto-β-lactam was reduced by yeast cells to afford the desired eis isomer as well as the undesired trans diastereomer. Substituting a yeast strain deficient in fatty acid synthase in this reduction suppressed formation of the trans diastereomer. These results suggest that a single enzyme is responsible for both the D- and L-cis-alcohols resulting from reduction of the α-keto-β-lactam. All of the yeast strains used in this project are available commercially, and these biocatalytic reductions require only common laboratory equipment.
- Kayser, Margaret M.,Mihovilovic, Marko D.,Kearns, Jeff,Feicht, Anton,Stewart, Jon D.
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p. 6603 - 6608
(2007/10/03)
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- Enantiomerically pure tetrahydro-5-oxo-2-furancarboxylic esters from dialkyl 2-oxoglutarates
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Enantiomerically pure tetrahydro-5-oxo-2-furancarboxylic esters can be prepared either by enzymatic resolution of the racemic γ-lactones themselves or by bioreduction with baker's yeast of dialkyl 2-oxoglutarates and subsequent cyclization of the resulting dialkyl 2-hydroxyglutarates. The best results were obtained by the former route, by which the desired compounds were isolated in high enantiomeric excess. Bioreductions were less satisfactory. In fact the hydroxyester intermediates were initially formed as racemic mixtures and their final enantiomeric enrichment was reached by asymmetric destruction, occurring in the bioreaction medium, however at the same time large amounts of alkyl 4-hydroxybutanoates were formed as side products.
- Drioli, Sara,Nitti, Patrizia,Pitacco, Giuliana,Tossut, Laura,Valentin, Ennio
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p. 2713 - 2728
(2007/10/03)
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- Application of [Ru((R)-BINAP)(MeCN)(1-3:5,6-η-C8H11)](BF4) as a catalyst precursor for enantioselective hydrogenations
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A catalyst system employing [Ru((R)-BINAP)(MeCN)(1-3:5,6-η- C8H11)](BF4) as catalyst precursor was evaluated using the enantioselective hydrogenations of tiglic acid, α-acetamidocinnamic acid, itaconic acid, methyl tiglate, dimethyl itaconate, geraniol, ethyl acetoacetate, and dimethyl oxaloacetate as a series of typical substrates. Acetone and MeOH were used as model aprotic and protic solvents, respectively. The hydrogenation of substrates containing an α,β-unsaturated carboxylic acid functionality required stoichiometric quantities of NEt3 to occur at reasonable rates in acetone solution, while in MeOH solution it did not. The enantioselectivities were typically higher in acetone than in MeOH. This catalyst system is among the more enantioselective ruthenium-BINAP type systems reported for the catalytic hydrogenation of substrates containing an α,β-unsaturated acid or ester functionality. The enantioselectivities for the hydrogenation of ketones ranged from poor (15%) to moderate (74%). 1,4- Dicarboxylate substrates with the prochiral olefin or ketone at the 2- position were all hydrogenated in good to high ee with the same enantioface selectivity both with our system and other catalysts reported in the literature. This raised the possibility that these substrates were hydrogenated through intermediates with similar structural features.
- Daley, Christopher J.A.,Wiles, Jason A.,Bergens, Steven H.
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p. 1447 - 1456
(2007/10/03)
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- Synthesis of unnatural (R)-malates from L-tartrates
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The cyclic thionocarbonates of L-tartrates were cleanly converted to (R)-malates by treating with magnesium iodide or magnesium and iodine.
- Rho, Ho-Sik
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p. 843 - 847
(2007/10/03)
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- A mild, efficient, and selective method for the desilylation of more common trialkylsilyl ethers by cerium(III) chloride heptahydrate and sodium iodide in acetonitrile
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Treatment of trialkylsilyl ethers with cerium(III) chloride heptahydrate and sodium iodide in acetonitrile provides a simple, convenient, and chemoselective process for desilylation, and the parent alcohol was obtained in high yield. The trialkylsilyl ethers have been cleaved selectively in the presence of acetate, benzyl and tetrahydropyranyl ethers.
- Bartoli, Giuseppe,Bosco, Marcella,Marcantoni, Enrico,Sambri, Letizia,Torregiani, Elisabetta
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p. 209 - 211
(2007/10/03)
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- Synthesis of medium ring ethers. 5. The synthesis of (±)-laurencin
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The enantioselective synthesis of (+)-laurencin 1 has been achieved in 27 steps from (R)-malic acid 20. The key steps involved methylenation of the lactone 49 followed by intramolecular hydrosilation of the enol ether 14 (Scheme 11) and one carbon homologation of the diol 13 to give the key ethyl substituted cyclic ether 59 (Scheme 13). The lactone 49 was obtained by two efficient routes, namely a Claisen ring expansion (Scheme 3) followed by cl-hydroxylation (Scheme 6) and a Yamaguchi lactonization (Scheme 11). Elaboration of the (E)-pentenynyl side chain (Scheme 18) and introduction of bromine (Scheme 19) completed the synthesis of (+)-laurencin 1.
- Burton, Jonathan W.,Clark, J. Stephen,Derrer, Sam,Stork, Thomas C.,Bendall, Justin G.,Holmes, Andrew B.
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p. 7483 - 7498
(2007/10/03)
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- Structure and stereochemistry of constanolactones A-G, lactonized cyclopropyl oxylipins from the red marine alga Constantinea simplex
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Extracts of the Oregon marine alga Constantinea simplex were found to contain a mixture of ω6 and ω3 unsaturated constanolactones, lactonized cyclopropyl-containing metabolites that logically derive from arachidonic and eicosapentaenoic acids, respectively. Detailed spectroscopic analysis of the isolated compounds, as natural products and various ester derivatives, afforded the planar structures of seven structurally related constanolactones. Constanolactones A-D possess 1,4-diol functionalities while constanolactones E-G contain a vicinal diol functionality. The absolute stereochemistry at all stereocenters in constanolactones A-D and at two stereocenters in constanolactones E and F were determined by chiral chromatography of fragments and chiroptical measurements of various mono- and dibenzoate derivatives and by comparable rotations within the two series (A-D and E-G). Isolation of these various diastereomeric diols, as well as of two presumed methanol adducts from CHCl3/MeOH extraction of C. simplex, leads us to speculate on the occurrence of highly unstable allylic epoxides in this red alga.
- Nagle,Gerwick
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p. 7227 - 7237
(2007/10/02)
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- Synthetic Studies on Oligomycins. Enantiospecific Synthesis of the Oligomycin B Spiroketal Portion and Establishment of the Absolute Stereochemistry of Oligomycin B
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The enantiospecific synthesis of the oligomycin B degradation product 2, corresponding to the C19-C34 spiroketal portion, has been achieved by sequential coupling of the C19-C21, C22-C27, and C28-C34 subunits, establishing the absolute stereochemistry of oligomycin B.
- Nakata, Masaya,Ishiyama, Takashi,Hirose, Youichi,Maruoka, Hiroshi,Tatsuta, Kuniaki
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p. 8439 - 8442
(2007/10/02)
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- A Biocatalytic Approach to the Enantioselective Synthesis of (R)- and (S)-Malic Acid
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(S)-Diethyl malate 1a was prepared (70-80percent yield; >98percent optical purity) by an enantioselective reduction of sodium diethyl oxalacetate 2 by fermenting baker's yeast (Saccharomyces cerevisiae).Other microorganisms were tested for their capability of reducing 2.Most of them afforded (S)-1a with ee from 8 to 94percent and only Candida utilis, Aspergillus niger and Lactobacillus fermentum ILC G18D preferentially reduced compound 2 to (R)-1a. (R)-Dimethyl malate 1b was obtained from (R,S)-malate 1b by hydrolysis with pig liver esterase (PLE), the highest ee (93percent) being realized at 0 deg C in 20percent aqueous methanol.Enzymatic hydrolyses of protected malates 1d and 1e did not lead to improvement of the ee.
- Santaniello, Enzo,Ferraboschi, Patrizia,Grisenti, Paride,Aragozzini, Fabrizio,Maconi, Elisabetta
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p. 601 - 605
(2007/10/02)
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- A practical synthesis of D-malate esters from L-tartrate esters
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D-malate esters were synthesized in one-pot from L-tartrate esters in 70-80% overall yields via the corresponding tartrate cyclic sulfites.
- Gao,Zepp
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p. 3155 - 3158
(2007/10/02)
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- Hydrogenolysis of α,β-Epoxyketone and Ester to Aldol in Pd(0)/HCOOH/Et3N and H2/Pd/C Reduction Media
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Hydrogenation of α,β-epoxycarbonyl compounds by using several catalysts and hydride sources was studied to obtain the corresponding β-hydroxy substrates.
- Torii, Sigeru,Okumoto, Hiroshi,Nakayasu, Seizo,Kotani, Takayuki
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p. 1975 - 1978
(2007/10/02)
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- A NEW CHIRAL HOST COMPOUND 10,10'-DIHYDROXY-9,9'-BIPHENANTHRYL. OPTICAL RESOLUTION OF PROPIONIC ACID DERIVATIVES, BUTYRIC ACID DERIVATIVES, AND 4-HYDROXYCYCLOPENT-2-EN-1-ONE DERIVATIVES BY COMPLEXATION
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Optically active 10,10'-dihydroxy-9,9'-biphenanthryl was designed as a new chiral host compound for optical resolution of guest compounds, and was found to be wery effective for resolution of the title guest compounds.
- Toda, Fumio,Tanaka, Koichi
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p. 1807 - 1810
(2007/10/02)
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- Interconversion of (R) and (S)-α-hydroxy esters: precursors of (S) and (R)-O-benzyl-α-hydroxylamino acid esters of high optical purity.
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(R)- and (S)-α-hydroxy esters 5 are interconverted via their triflates 6 in high chemical as well as optical yields by reaction with dimethylformamide.The same triflates are efficiently converted into N-hydroxy-α-amino acid derivatives 7 of high optical purity.
- Feenstra, R. W.,Stokkingreef, E. H. M.,Nivard, R. J. F.,Ottenheijm, H. C. J.
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p. 5583 - 5596
(2007/10/02)
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- Leiopathic Acid, a Novel Optically Active Hydroxydocosapentaenoic Acid, and Related Compouds, from the Black Coral Leiopathes sp. of Saint Paul Island (S. Indian Ocean)
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The antipatharian Leiopathes sp., collected around Saint Paul Island, is shown here to contain, in relatively high amounts, the novel fatty acid leiopathic acid (=(+)-(10R,7Z,11E,13Z,16Z,19Z)-10-hydroxy-7,11,13,16,19-docosapentaenoic acid; (+)-1), besides (+)-(8R,5Z,9E,11Z,14Z,17Z)-8-hydroxy-5,9,11,14,17-icosapentaenoic acid ((+)-11) and (+)-(8R, 5Z,9E,11Z,14Z)-8-hydroxy-5,9,11,14-icosatetraenoic acid ((+)-16) and their ethyl esters (+)-2, (+)-12, and (+)-17.
- Guerriero, Antonio,D'Ambrosio, Michele,Pietra, Francesco
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p. 1094 - 1100
(2007/10/02)
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- STEREOCHEMICAL STUDIES ON BORONOLIDE, AN α-PYRONE FROM TETRADENIA BARBERAE
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Key Word Index-Tetradenia barberae; Lamiaceae; α-pyrone; boronolide. The structure of boronolide isolated from Tetradenia barberae has been confirmed as 6R--5,6-dihydro-2H-pyran-2-one by chemical degradation.
- Davies-Coleman, Michael T.,Rivett, Douglas E. A.
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p. 3047 - 3050
(2007/10/02)
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- Enantiomerically Pure Synthetic Building Blocks with Four C-Atoms and Two or Three Functional Groups from β-Hydroxy-butanoic, Malic, and Tartaric Acid
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The pool of chiral, non-racemic electrophilic building blocks, which are available from simple natural products in both enantiomeric forms is enlarged by the epoxides 3, 5, and 10, by the tosylate 12a, and by the aldehydes 18 (cf. symbols A-D, 14, and Scheme 1).Key steps of the conversions leading from hydroxyacids to the building blocks are: epoxide-opening by triethylborohydride (1 --> 2a) and tosylate reduction (12a --> 12b); the Mitsunobu inversion (2a --> 4a); the reduction of (R,R)-tartaric ester to (R)-malic ester by NBS (N-bromosuccinimide) opening of the benzaldehyde acetal 8 and tin hydride reduction (6c -->7c); the enantiomer enrichment of optically active ethyl β-hydroxy-butanoate through the crystalline dinitrobenzoate 21b.Detailed procedures are given for large scale preparations of the key intermediates.The enantiomeric purities of the building blocks are secured by correlations.
- Hungerbuehler, Ernst von,Seebach, Dieter,Wasmuth, Daniel
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p. 1467 - 1487
(2007/10/02)
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