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Beilstein Journal of Organic Chemistry

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https://www.readbyqxmd.com/read/28326145/polyketide-stereocontrol-a-study-in-chemical-biology
#1
REVIEW
Kira J Weissman
The biosynthesis of reduced polyketides in bacteria by modular polyketide synthases (PKSs) proceeds with exquisite stereocontrol. As the stereochemistry is intimately linked to the strong bioactivity of these molecules, the origins of stereochemical control are of significant interest in attempts to create derivatives of these compounds by genetic engineering. In this review, we discuss the current state of knowledge regarding this key aspect of the biosynthetic pathways. Given that much of this information has been obtained using chemical biology tools, work in this area serves as a showcase for the power of this approach to provide answers to fundamental biological questions...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28326144/correction-inherently-chiral-calix-4-arenes-via-oxazoline-directed-ortholithiation-synthesis-and-probe-of-chiral-space
#2
Simon A Herbert, Laura J van Laeren, Dominic C Castell, Gareth E Arnott
[This corrects the article DOI: 10.3762/bjoc.10.291.].
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28326143/posttranslational-isoprenylation-of-tryptophan-in-bacteria
#3
REVIEW
Masahiro Okada, Tomotoshi Sugita, Ikuro Abe
Posttranslational isoprenylation is generally recognized as a universal modification of the cysteine residues in peptides and the thiol groups of proteins in eukaryotes. In contrast, the Bacillus quorum sensing peptide pheromone, the ComX pheromone, possesses a posttranslationally modified tryptophan residue, and the tryptophan residue is isoprenylated with either a geranyl or farnesyl group at the gamma position to form a tricyclic skeleton that bears a newly formed pyrrolidine, similar to proline. The post-translational dimethylallylation of two tryptophan residues of a cyclic peptide, kawaguchipeptin A, from cyanobacteria has also been reported...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28326142/continuous-n-alkylation-reactions-of-amino-alcohols-using-%C3%AE-al2o3-and-supercritical-co2-unexpected-formation-of-cyclic-ureas-and-urethanes-by-reaction-with-co2
#4
Emilia S Streng, Darren S Lee, Michael W George, Martyn Poliakoff
The use of γ-Al2O3 as a heterogeneous catalyst in scCO2 has been successfully applied to the amination of alcohols for the synthesis of N-alkylated heterocycles. The optimal reaction conditions (temperature and substrate flow rate) were determined using an automated self-optimising reactor, resulting in moderate to high yields of the target products. Carrying out the reaction in scCO2 was shown to be beneficial, as higher yields were obtained in the presence of CO2 than in its absence. A surprising discovery is that, in addition to cyclic amines, cyclic ureas and urethanes could be synthesised by incorporation of CO2 from the supercritical solvent into the product...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28326141/-z-selective-takai-olefination-of-salicylaldehydes
#5
Stephen M Geddis, Caroline E Hagerman, Warren R J D Galloway, Hannah F Sore, Jonathan M Goodman, David R Spring
The Takai olefination (or Takai reaction) is a method for the conversion of aldehydes to vinyl iodides, and has seen widespread implementation in organic synthesis. The reaction is usually noted for its high (E)-selectivity; however, herein we report the highly (Z)-selective Takai olefination of salicylaldehyde derivatives. Systematic screening of related substrates led to the identification of key factors responsible for this surprising inversion of selectivity, and enabled the development of a modified mechanistic model to rationalise these observations...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28326140/synthesis-and-optical-properties-of-new-5-aryl-substituted-2-5-bis-3-decyl-2-2-bithiophen-5-yl-1-3-4-oxadiazoles
#6
Anastasia Sergeevna Kostyuchenko, Tatyana Yu Zheleznova, Anton Jaroslavovich Stasyuk, Aleksandra Kurowska, Wojciech Domagala, Adam Pron, Alexander S Fisyuk
New photoluminescent donor-acceptor-donor (DAD) molecules, namely 5'-aryl-substituted 2,5-bis(3-decyl-2,2'-bithiophen-5-yl)-1,3,4-oxadiazoles were prepared by palladium-catalyzed coupling from readily available compounds such as ethyl 3-decyl-2,2'-bithiophene-5-carboxylate and aryl halides. The obtained compounds feature increasing bathochromic shifts in their emission spectra with increasing aryl-substituent size yielding blue to bluish-green emissions. At the same time, their absorption spectra are almost independent from the identity of the terminal substituent with λmax values ranging from 395 to 405 nm...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28326139/a-chemoselective-and-continuous-synthesis-of-m-sulfamoylbenzamide-analogues
#7
Arno Verlee, Thomas Heugebaert, Tom van der Meer, Pavel I Kerchev, Frank Van Breusegem, Christian V Stevens
For the synthesis of m-sulfamoylbenzamide analogues, small molecules which are known for their bioactivity, a chemoselective procedure has been developed starting from m-(chlorosulfonyl)benzoyl chloride. Although a chemoselective process in batch was already reported, a continuous-flow process reveals an increased selectivity at higher temperatures and without catalysts. In total, 15 analogues were synthesized, using similar conditions, with yields ranging between 65 and 99%. This is the first automated and chemoselective synthesis of m-sulfamoylbenzamide analogues...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28326138/correction-synthesis-dynamic-nmr-characterization-and-xrd-studies-of-novel-n-n-substituted-piperazines-for-bioorthogonal-labeling
#8
Constantin Mamat, Marc Pretze, Matthew Gott, Martin Köckerling
[This corrects the article DOI: 10.3762/bjoc.12.242.].
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28326137/nmr-reaction-monitoring-in-flow-synthesis
#9
REVIEW
M Victoria Gomez, Antonio de la Hoz
Recent advances in the use of flow chemistry with in-line and on-line analysis by NMR are presented. The use of macro- and microreactors, coupled with standard and custom made NMR probes involving microcoils, incorporated into high resolution and benchtop NMR instruments is reviewed. Some recent selected applications have been collected, including synthetic applications, the determination of the kinetic and thermodynamic parameters and reaction optimization, even in single experiments and on the μL scale. Finally, software that allows automatic reaction monitoring and optimization is discussed...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28326136/the-reductive-decyanation-reaction-an-overview-and-recent-developments
#10
REVIEW
Jean-Marc R Mattalia
This review presents an overview of the reductive decyanation reaction with a special interest for recent developments. This transformation allows synthetic chemists to take advantages of the nitrile functional group before its removal. Mechanistic details and applications to organic synthesis are provided.
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28326135/regiochemistry-of-cyclocondensation-reactions-in-the-synthesis-of-polyazaheterocycles
#11
Patrick T Campos, Leticia V Rodrigues, Andrei L Belladona, Caroline R Bender, Juliana S Bitencurt, Fernanda A Rosa, Davi F Back, Helio G Bonacorso, Nilo Zanatta, Clarissa P Frizzo, Marcos A P Martins
The syntheses of several polyazaheterocycles are demonstrated. The cyclocondensation reactions between β-enaminodiketones [CCl3C(O)C(=CNMe2)C(O)-CO2Et] and aromatic amidines resulted in glyoxalate-substituted pyrido[1,2-a]pyrimidinone, thiazolo[3,2-a]pyrimidinone and pyrimido[1,2-a]benzimidazole. Pyrazinones and quinoxalinones were obtained through the reaction of these glyoxalates with ethylenediamine and 1,2-phenylenediamine derivatives. On the other hand, the reaction of glyoxalates with amidines did not lead to the formation of imidazolones, but rather N-acylated products were obtained...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28326134/revaluation-of-biomass-derived-furfuryl-alcohol-derivatives-for-the-synthesis-of-carbocyclic-nucleoside-phosphonate-analogues
#12
Bemba Sidi Mohamed, Christian Périgaud, Christophe Mathé
The racemic synthesis of new carbocyclic nucleoside methylphosphonate analogues bearing purine bases (adenine and guanine) was accomplished using bio-sourced furfuryl alcohol derivatives. All compounds were prepared using a Mitsunobu coupling between the heterocyclic base and an appropriate carbocyclic precursor. After deprotection, the compounds were evaluated for their activity against a large number of viruses. However, none of them showed significant antiviral activity or cytotoxicity.
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28326133/versatile-synthesis-of-the-signaling-peptide-glorin
#13
Robert Barnett, Daniel Raszkowski, Thomas Winckler, Pierre Stallforth
We present a versatile synthesis of the eukaryotic signaling peptide glorin as well as glorinamide, a synthetic analog. The ability of these compounds to activate glorin-induced genes in the social amoeba Polysphondylium pallidum was evaluated by quantitative reverse transcription PCR, whereby both compounds showed bioactivity comparable to a glorin standard. This synthetic route will be useful in conducting detailed structure-activity relationship studies as well as in the design of chemical probes to dissect glorin-mediated signaling pathways...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28326132/continuous-flow-synthesis-of-highly-functionalized-imidazo-oxadiazoles-facilitated-by-microfluidic-extraction
#14
Ananda Herath, Nicholas D P Cosford
A versatile continuous-flow synthesis of highly functionalized 1,2,4-oxadiazoles starting from carboxylic acids is reported. This process was applied to the multistep synthesis of imidazo[1,2-a]pyridin-2-yl-1,2,4-oxadiazoles, using a three reactor, multistep continuous-flow system without isolation of intermediates. This continuous-flow method was successfully combined with a single-step liquid-liquid microextraction unit to remove high boiling point polar solvents and impurities and provides the target compounds in high purity with excellent overall yields...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28326131/spectral-and-dft-studies-of-anion-bound-organic-receptors-time-dependent-studies-and-logic-gate-applications
#15
Srikala Pangannaya, Neethu Padinchare Purayil, Shweta Dabhi, Venu Mankad, Prafulla K Jha, Satyam Shinde, Darshak R Trivedi
New colorimetric receptors R1 and R2 with varied positional substitution of a cyano and nitro signaling unit having a hydroxy functionality as the hydrogen bond donor site have been designed, synthesized and characterized by FTIR, (1)H NMR spectroscopy and mass spectrometry. The receptors R1 and R2 exhibit prominent visual response for F(-) and AcO(-) ions allowing the real time analysis of these ions in aqueous media. The formation of the receptor-anion complexes has been supported by UV-vis titration studies and confirmed through binding constant calculations...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28228862/highly-bulky-and-stable-geometry-constrained-iminopyridines-synthesis-structure-and-application-in-pd-catalyzed-suzuki-coupling-of-aryl-chlorides
#16
Yi Lai, Zhijian Zong, Yujie Tang, Weimin Mo, Nan Sun, Baoxiang Hu, Zhenlu Shen, Liqun Jin, Wen-Hua Sun, Xinquan Hu
A series of bulky geometry-constrained iminopyridylpalladium chlorides were developed. The steric environment adjacent to the nitrogen atom in the pyridine rings and diimine parts enhanced the thermal stability of the palladium species. Bulkier groups at the imino group stabilized the palladium species and the corresponding palladium chlorides showed high activities in the coupling reaction of aryl chlorides.
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28228861/interactions-between-photoacidic-3-hydroxynaphtho-1-2-b-quinolizinium-and-cucurbit-7-uril-influence-on-acidity-in-the-ground-and-excited-state
#17
Jonas Becher, Daria V Berdnikova, Darinka Dzubiel, Heiko Ihmels, Phil M Pithan
3-Hydroxynaphtho[1,2-b]quinolizinium was synthesized by cyclodehydration route and its optical properties in different media were investigated. The absorption and emission spectra of this compound depend on the pH of the solution. Thus, at higher pH values the deprotonation yields a merocyanine-type dye that exhibits significantly red-shifted absorption bands and causes a dual emisson, i.e., a combination of emission bands of the hydroxyquinolizinium and its deprotonated form. Whereas this compound is a weak acid in the ground state (pKa = 7...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28228860/efficient-access-to-%C3%AE-vinylporphyrin-derivatives-via-palladium-cross-coupling-of-%C3%AE-bromoporphyrins-with-n-tosylhydrazones
#18
Vinicius R Campos, Ana T P C Gomes, Anna C Cunha, Maria da Graça P M S Neves, Vitor F Ferreira, José A S Cavaleiro
This work describes a new approach to obtain new β-vinylporphyrin derivatives through palladium-catalyzed cross-coupling reaction of 2-bromo-5,10,15,20-tetraphenylporphyrinatozinc(II) with N-tosylhydrazones. This is the first report of the use of such synthetic methodology in porphyrin chemistry allowing the synthesis of new derivatives, containing β-arylvinyl substituents.
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28228859/dynamics-and-interactions-of-ibuprofen-in-cyclodextrin-nanosponges-by-solid-state-nmr-spectroscopy
#19
Monica Ferro, Franca Castiglione, Nadia Pastori, Carlo Punta, Lucio Melone, Walter Panzeri, Barbara Rossi, Francesco Trotta, Andrea Mele
Two different formulations of cyclodextrin nanosponges (CDNS), obtained by polycondensation of β-cyclodextrin with ethylenediaminetetraacetic acid dianhydride (EDTAn), were treated with aqueous solutions of ibuprofen sodium salt (IbuNa) affording hydrogels that, after lyophilisation, gave two solid CDNS-drug formulations. (1)H fast MAS NMR and (13)C CP-MAS NMR spectra showed that IbuNa was converted in situ into its acidic and dimeric form (IbuH) after freeze-drying. (13)C CP-MAS NMR spectra also indicated that the structure of the nanosponge did not undergo changes upon drug loading compared to the unloaded system...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28228858/a-novel-method-for-heterocyclic-amide-thioamide-transformations
#20
Walid Fathalla, Ibrahim A I Ali, Pavel Pazdera
In this paper, we introduce a novel and convenient method for the transformation of heterocyclic amides into heteocyclic thioamides. A two-step approach was applied for this transformation: Firstly, we applied a chlorination of the heterocyclic amides to afford the corresponding chloroheterocycles. Secondly, the chloroherocycles and N-cyclohexyl dithiocarbamate cyclohexylammonium salt were heated in chloroform for 12 h at 61 °C to afford heteocyclic thioamides in excellent yields.
2017: Beilstein Journal of Organic Chemistry
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