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Beilstein Journal of Organic Chemistry

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https://www.readbyqxmd.com/read/28546847/synthesis-of-tetrasubstituted-pyrazoles-containing-pyridinyl-substituents
#1
Josef Jansa, Ramona Schmidt, Ashenafi Damtew Mamuye, Laura Castoldi, Alexander Roller, Vittorio Pace, Wolfgang Holzer
A synthesis of tetrasubstituted pyrazoles containing two, three or four pyridinyl substituents is described. Hence, the reaction of 1,3-dipyridinyl-1,3-propanediones with 2-hydrazinopyridine or phenylhydrazine, respectively, affords the corresponding 1,3,5-trisubstituted pyrazoles. Iodination at the 4-position of the pyrazole nucleus by treatment with I2/HIO3 gives the appropriate 4-iodopyrazoles which served as starting materials for different cross-coupling reactions. Finally, Negishi cross-coupling employing organozinc halides and Pd catalysts turned out to be the method of choice to obtain the desired tetrasubstituted pyrazoles...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28546846/metal-free-hydroarylation-of-the-side-chain-carbon-carbon-double-bond-of-5-2-arylethenyl-3-aryl-1-2-4-oxadiazoles-in-triflic-acid
#2
Anna S Zalivatskaya, Dmitry S Ryabukhin, Marina V Tarasenko, Alexander Yu Ivanov, Irina A Boyarskaya, Elena V Grinenko, Ludmila V Osetrova, Eugeniy R Kofanov, Aleksander V Vasilyev
The metal-free reaction of 5-(2-arylethenyl)-3-aryl-1,2,4-oxadiazoles with arenes in neat triflic acid (TfOH, CF3SO3H), both under thermal and microwave conditions, leads to 5-(2,2-diarylethyl)-3-aryl-1,2,4-oxadiazoles. The products are formed through the regioselective hydroarylation of the side chain carbon-carbon double bond of the starting oxadiazoles in yields up to 97%. According to NMR data and DFT calculations, N(4),C-diprotonated forms of oxadiazoles are the electrophilic intermediates in this reaction...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28546845/expression-purification-and-structural-analysis-of-functional-gaba-transporter-1-using-the-baculovirus-expression-system
#3
Jing Hu, Chris Weise, Christoph Böttcher, Hua Fan, Jian Yin
The γ-aminobutyric acid (GABA) transporter 1 (GAT1) belongs to a family of Na(+) and Cl(-)-coupled transport proteins and possesses 12 putative transmembrane domains. To perform structural analyses of the GAT1 protein, the GAT1/green fluorescent protein (GFP) fusion protein was functionally expressed in insect Sf9 cells by the BAC-TO-BAC(®) baculovirus expression system. A two-step procedure to purify the GAT1/GFP fusion protein from insect Sf9 cells has been established and involves immunoaffinity chromatography using self-prepared anti-GFP antibodies and size-exclusion fast protein liquid chromatography (SE-FPLC)...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28546844/molecular-level-architectural-design-using-benzothiadiazole-based-polymers-for-photovoltaic-applications
#4
Vinila N Viswanathan, Arun D Rao, Upendra K Pandey, Arul Varman Kesavan, Praveen C Ramamurthy
A series of low band gap, planar conjugated polymers, P1 (PFDTBT), P2 (PFDTDFBT) and P3 (PFDTTBT), based on fluorene and benzothiadiazole, was synthesized. The effect of fluorine substitution and fused aromatic spacers on the optoelectronic and photovoltaic performance was studied. The polymer, derived from dithienylated benzothiodiazole and fluorene, P1, exhibited a highest occupied molecular orbital (HOMO) energy level at -5.48 eV. Density functional theory (DFT) studies as well as experimental measurements suggested that upon substitution of the acceptor with fluorine, both the HOMO and lowest unoccupied molecular orbital (LUMO) energy levels of the resulting polymer, P2, were lowered, leading to a higher open circuit voltage and short circuit current with an overall improvement of more than 110% for the photovoltaic devices...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28546843/first-total-synthesis-of-kipukasin-a
#5
Chuang Li, Haixin Ding, Zhizhong Ruan, Yirong Zhou, Qiang Xiao
In this paper, a practical approach for the total synthesis of kipukasin A is presented with 22% overall yield by using tetra-O-acetyl-β-D-ribose as starting material. An improved iodine-promoted acetonide-forming reaction was developed to access 1,2-O-isopropylidene-α-D-ribofuranose. For the first time, ortho-alkynylbenzoate was used as protecting group for the 5-hydoxy group. After subsequent Vorbrüggen glycosylation, the protecting group could be removed smoothly in the presence of 5 mol % Ph3PAuOTf in dichloromethane to provide kipukasin A in high yield and regioselectivity...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28546842/opportunities-and-challenges-for-the-sustainable-production-of-structurally-complex-diterpenoids-in-recombinant-microbial-systems
#6
REVIEW
Katarina Kemper, Max Hirte, Markus Reinbold, Monika Fuchs, Thomas Brück
With over 50.000 identified compounds terpenes are the largest and most structurally diverse group of natural products. They are ubiquitous in bacteria, plants, animals and fungi, conducting several biological functions such as cell wall components or defense mechanisms. Industrial applications entail among others pharmaceuticals, food additives, vitamins, fragrances, fuels and fuel additives. Central building blocks of all terpenes are the isoprenoid compounds isopentenyl diphosphate and dimethylallyl diphosphate...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28546841/the-effect-of-cyclodextrin-complexation-on-the-solubility-and-photostability-of-nerolidol-as-pure-compound-and-as-main-constituent-of-cabreuva-essential-oil
#7
Joyce Azzi, Pierre-Edouard Danjou, David Landy, Steven Ruellan, Lizette Auezova, Hélène Greige-Gerges, Sophie Fourmentin
Nerolidol (Ner), a major component of many plant essential oils, is known for its various biological properties. However, the low solubility of Ner in water and its susceptibility to degradation limit its application. The aim of our study was to improve the solubility and photostability of Ner through its encapsulation in different cyclodextrins (CDs). The formation constants of cis-, trans-Ner and their commercial mixture with various CDs (α-CD, β-CD, γ-CD, HP-β-CD, RAMEB, CRYSMEB and SBE-β-CD) were determined by phase solubility studies and confirmed by the spectral displacement UV-visible method...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28546840/nucleophilic-and-electrophilic-cyclization-of-n-alkyne-substituted-pyrrole-derivatives-synthesis-of-pyrrolopyrazinone-pyrrolotriazinone-and-pyrrolooxazinone-moieties
#8
Işıl Yenice, Sinan Basceken, Metin Balci
Intramolecular nucleophilic and electrophilic cyclization of N-alkyne-substituted pyrrole esters is described. Efficient routes towards the synthesis of pyrrolopyrazinone, pyrrolotriazinone and pyrrolooxazinone have been developed. First, N-alkyne-substituted pyrrole ester derivatives were synthesized. Introduction of various substituents into the alkyne functionality was accomplished by a copper-catalyzed cross-coupling reaction. Nucleophilic cyclization of N-alkyne-substituted methyl 1H-pyrrole-2-carboxylates with hydrazine afforded the 6-exo-dig/6-endo-dig cyclization products depending on the electronic nature of the substituents attached to the alkyne...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28546839/a-practical-and-efficient-approach-to-imidazo-1-2-a-pyridine-fused-isoquinolines-through-the-post-gbb-transformation-strategy
#9
Taofeng Shao, Zhiming Gong, Tianyi Su, Wei Hao, Chao Che
Diversity-oriented synthesis of the biologically intriguing imidazo[1,2-a]pyridine-fused isoquinoline systems from readily available starting materials was achieved through the Groebke-Blackburn-Bienaymé reaction followed by a gold-catalyzed cyclization strategy. The synthetic approach is characterized by mild reaction conditions and a broad substrate scope, allowing for the rapid construction of structurally complex and diverse heterocycles in moderate to good yields.
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28546838/dmap-assisted-sulfonylation-as-an-efficient-step-for-the-methylation-of-primary-amine-motifs-on-solid-support
#10
Johnny N Naoum, Koushik Chandra, Dorit Shemesh, R Benny Gerber, Chaim Gilon, Mattan Hurevich
Several multistep strategies were developed to ensure single methylation of amines on solid support. These strategies rely on the introduction of the o-NBS protecting/activating group as a key step. We found that the state-of-the-art strategies fail for the methylation of several primary amine motifs, largely due to inefficient sulfonylation. Here we show that using the superior nucleophilic base DMAP instead of the commonly used base collidine as a sulfonylation additive is essential for the introduction of the o-NBS group to these amine motifs...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28546837/new-approach-toward-the-synthesis-of-deuterated-pyrazolo-1-5-a-pyridines-and-1-2-4-triazolo-1-5-a-pyridines
#11
Aleksey Yu Vorob'ev, Vyacheslav I Supranovich, Gennady I Borodkin, Vyacheslav G Shubin
An efficient and operationally simple synthesis of 7-deuteropyrazolo[1,5-a]pyridine and 7-deutero-1,2,4-triazolo[1,5-a]pyridine derivatives using α-H/D exchange of 1-aminopyridinium cations in basic D2O followed by a 1,3-cycloaddition of acetylenes and nitriles is presented. A high regioselectivity and a high degree of deuterium incorporation were achieved. The procedure was applied for several 4-R-1-aminopyridinium cations (R = H, Me, OMe).
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28546836/synthesis-of-d-manno-heptulose-via-a-cascade-aldol-hemiketalization-reaction
#12
Yan Chen, Xiaoman Wang, Junchang Wang, You Yang
A [4 + 3] synthesis of D-manno-heptulose is described. The cascade aldol/hemiketalization reaction of a C4 aldehyde with a C3 ketone provides the differentially protected ketoheptose building block, which can be further reacted to furnish target D-manno-heptulose.
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28546835/lipids-fatty-acids-and-derivatives-polyketides-and-isoprenoids
#13
EDITORIAL
Jeroen S Dickschat
No abstract text is available yet for this article.
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28546834/cyclodextrins-tethered-with-oligolactides-green-synthesis-and-structural-assessment
#14
Cristian Peptu, Mihaela Balan-Porcarasu, Alena Šišková, Ľudovít Škultéty, Jaroslav Mosnáček
Biodegradable oligolactide derivatives based on α-, β- and γ-cyclodextrins (CDs) were synthesized by a green procedure in which CDs play the role of both the initiator and the catalyst. The synthetic procedure in which CDs and L-lactide (L-LA) are reacting in bulk at relatively high temperature of 110 °C was investigated considering the structural composition of the products. The obtained products were thoroughly characterized via mass spectrometry methods with soft ionization like matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI)...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28546833/energy-down-converting-organic-fluorophore-functionalized-mesoporous-silica-hybrids-for-monolith-coated-light-emitting-diodes
#15
Markus Börgardts, Thomas J J Müller
The covalent attachment of organic fluorophores in mesoporous silica matrices for usage as energy down converting phosphors without employing inorganic transition or rare earth metals is reported in this article. Triethoxysilylpropyl-substituted derivatives of the blue emitting perylene, green emitting benzofurazane, and red emitting Nile red were synthesized and applied in the synthesis of mesoporous hybrid materials by postsynthetic grafting to commercially available MCM-41. These individually dye-functionalized hybrid materials are mixed in variable ratios to furnish a powder capable of emitting white light with CIE chromaticity coordinates of x = 0...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28546832/phosphazene-catalyzed-desymmetrization-of-cyclohexadienones-by-dithiane-addition
#16
Matthew A Horwitz, Elisabetta Massolo, Jeffrey S Johnson
We report a desymmetrization of cyclohexadienones by intramolecular conjugate addition of a tethered dithiane nucleophile. Mild reaction conditions allow the formation of diversely functionalized fused bicyclic lactones. The products participate in facially selective additions from the convex surface, leading to allylic alcohol derivatives.
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28503210/synthesis-of-ribavirin-2-me-c-nucleoside-analogues
#17
Fanny Cosson, Aline Faroux, Jean-Pierre Baltaze, Jonathan Farjon, Régis Guillot, Jacques Uziel, Nadège Lubin-Germain
An efficient synthetic pathway leading to two carbonated analogues of ribavirin is described. The key-steps in the synthesis of these ribosyltriazoles bearing a quaternary carbon atom in the 2'-position are an indium-mediated alkynylation and a 1,3-dipolar cyclization.
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28503209/continuous-flow-processes-for-the-catalytic-partial-hydrogenation-reaction-of-alkynes
#18
REVIEW
Carmen Moreno-Marrodan, Francesca Liguori, Pierluigi Barbaro
The catalytic partial hydrogenation of substituted alkynes to alkenes is a process of high importance in the manufacture of several market chemicals. The present paper shortly reviews the heterogeneous catalytic systems engineered for this reaction under continuous flow and in the liquid phase. The main contributions appeared in the literature from 1997 up to August 2016 are discussed in terms of reactor design. A comparison with batch and industrial processes is provided whenever possible.
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28503208/fluorinated-cyclohexanes-synthesis-of-amine-building-blocks-of-the-all-cis-2-3-5-6-tetrafluorocyclohexylamine-motif
#19
Tetiana Bykova, Nawaf Al-Maharik, Alexandra M Z Slawin, David O'Hagan
This paper reports the synthesis of three amine stereoisomers 5a-c of the tetrafluorocyclohexyl ring system, as building blocks for discovery chemistry programmes. The synthesis starts from a Birch reduction of benzonitrile, followed by an in situ methyl iodide quench. The resultant 2,5-cyclohexadiene was progressed via double epoxidations and then hydrofluorination ring opening reactions. The resultant fluorohydrin moieties were then converted to different stereoisomers of the tetrafluorocyclohexyl ring system, and then reductive hydrogenation of the nitrile delivered three amine stereoisomers...
2017: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28503207/membrane-properties-of-hydroxycholesterols-related-to-the-brain-cholesterol-metabolism
#20
Malte Hilsch, Ivan Haralampiev, Peter Müller, Daniel Huster, Holger A Scheidt
Compared to cholesterol, hydroxycholesterols contain an additional hydroxy group in the alkyl chain and are able to efficiently cross the brain-blood barrier. Therefore, they are responsible for the sterol transfer between brain and circulation. The current study compares the membrane properties of several hydroxycholesterols with those of cholesterol using (2)H NMR spectroscopy, a membrane permeability assay, and fluorescence microscopy experiments. It is shown that hydroxycholesterols do not exert the unique impact on membrane properties characteristic for cholesterol with regard to the influence on lipid chain order, membrane permeability and formation of lateral domains...
2017: Beilstein Journal of Organic Chemistry
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