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Beilstein Journal of Organic Chemistry

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https://read.qxmd.com/read/30745997/synthesis-of-nonracemic-hydroxyglutamic-acids
#1
REVIEW
Dorota G Piotrowska, Iwona E Głowacka, Andrzej E Wróblewski, Liwia Lubowiecka
Glutamic acid is involved in several cellular processes though its role as the neurotransmitter is best recognized. For detailed studies of interactions with receptors a number of structural analogues of glutamic acid are required to map their active sides. This review article summarizes syntheses of nonracemic hydroxyglutamic acid analogues equipped with functional groups capable for the formation of additional hydrogen bonds, both as donors and acceptors. The majority of synthetic strategies starts from natural products and relies on application of chirons having the required configuration at the carbon atom bonded to nitrogen (e...
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30745996/olefin-metathesis-in-multiblock-copolymer-synthesis
#2
REVIEW
Maria L Gringolts, Yulia I Denisova, Eugene Sh Finkelshtein, Yaroslav V Kudryavtsev
Multiblock copolymers constitute a basis for an emerging class of nanomaterials that combine various functional properties with durability and enhanced mechanical characteristics. Our mini-review addresses synthetic approaches to the design of multiblock copolymers from unsaturated monomers and polymers using olefin metathesis reactions and other ways of chemical modification across double C=C bonds. The main techniques, actively developed during the last decade and discussed here, are the coupling of end-functionalized blocks, sequential ring-opening metathesis polymerization, and cross metathesis between unsaturated polymers, or macromolecular cross metathesis...
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30745995/first-synthesis-of-cryptands-with-sucrose-scaffold
#3
Patrycja Sokołowska, Michał Kowalski, Sławomir Jarosz
Cryptands with sucrose scaffold, an unknown class of such derivatives, were prepared from the readily available 2,3,3',4,4'-penta- O -benzylsucrose and 1',2,3,3',4,4'-hexa- O -benzylsucrose.
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30745994/catalysis-of-linear-alkene-metathesis-by-grubbs-type-ruthenium-alkylidene-complexes-containing-hemilabile-%C3%AE-%C3%AE-diphenyl-monosubstituted-pyridin-2-yl-methanolato-ligands
#4
Tegene T Tole, Johan H L Jordaan, Hermanus C M Vosloo
Four new Grubbs-type precatalysts [RuCl(H2 IMes)(O^N)(=CHPh)], where [O^N = α,α-diphenyl-(3-methylpyridin-2-yl)methanolato, α,α-diphenyl-(4-methylpyridin-2-yl)methanolato, α,α-diphenyl-(5-methylpyridin-2-yl)methanolato and α,α-diphenyl-(3-methoxypyridin-2-yl)methanolato] were synthesized and tested for their activity, stability and selectivity in the 1-octene metathesis reaction. Overall the precatalysts showed good activity and high stability for the metathesis of 1-octene at temperatures above 80 °C and up to 110 °C...
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30745993/synthesis-and-biological-activity-of-methylated-derivatives-of-the-pseudomonas-metabolites-hhq-hqno-and-pqs
#5
Sven Thierbach, Max Wienhold, Susanne Fetzner, Ulrich Hennecke
Selectively methylated analogues of naturally occurring 2-heptyl-4(1 H )-quinolones, which are alkaloids common within the Rutaceae family and moreover are associated with quorum sensing and virulence of the human pathogen Pseudomonas aeruginosa , have been prepared. While the synthesis by direct methylation was successful for 3-unsubstituted 2-heptyl-4(1 H )-quinolones, methylated derivatives of the Pseudomonas quinolone signal (PQS) were synthesized from 3-iodinated quinolones by methylation and iodine-metal exchange/oxidation...
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30745992/silanediol-versus-chlorosilanol-hydrolyses-and-hydrogen-bonding-catalyses-with-fenchole-based-silanes
#6
Falco Fox, Jörg M Neudörfl, Bernd Goldfuss
Biphenyl-2,2'-bisfenchyloxydichlorosilane ( 7 , BIFOXSiCl2 ) is synthesized and employed as precursor for the new silanols biphenyl-2,2'-bisfenchyloxychlorosilanol ( 8 , BIFOXSiCl(OH)) and biphenyl-2,2'-bisfenchyloxysilanediol ( 9 , BIFOXSi(OH)2 ). BIFOXSiCl2 ( 7 ) shows a remarkable stability against hydrolysis, yielding silanediol 9 under enforced conditions. A kinetic study for the hydrolysis of dichlorosilane 7 shows a 263 times slower reaction compared to reference bis-(2,4,6-tri- tert -butylphenoxy)dichlorosilane ( 14 ), known for its low hydrolytic reactivity...
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30745991/ammonium-tagged-ruthenium-based-catalysts-for-olefin-metathesis-in-aqueous-media-under-ultrasound-and-microwave-irradiation
#7
Łukasz Gułajski, Andrzej Tracz, Katarzyna Urbaniak, Stefan J Czarnocki, Michał Bieniek, Tomasz K Olszewski
The influence of microwave and ultrasonic irradiation on the performance of ammonium-tagged Ru-based catalysts in olefin metathesis transformations in aqueous media was studied. Differences in the catalytic activity in correlation with the nature of the present counter ion and the size of the N -heterocyclic carbene (NHC) ligand were revealed. The presented methodology allows for preparation of a variety of polar and non-polar metathesis products under environmentally friendly conditions.
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30745990/computational-characterization-of-enzyme-bound-thiamin-diphosphate-reveals-a-surprisingly-stable-tricyclic-state-implications-for-catalysis
#8
Ferran Planas, Michael J McLeish, Fahmi Himo
Thiamin diphosphate (ThDP)-dependent enzymes constitute a large class of enzymes that catalyze a diverse range of reactions. Many are involved in stereospecific carbon-carbon bond formation and, consequently, have found increasing interest and utility as chiral catalysts in various biocatalytic applications. All ThDP-catalyzed reactions require the reaction of the ThDP ylide (the activated state of the cofactor) with the substrate. Given that the cofactor can adopt up to seven states on an enzyme, identifying the factors affecting the stability of the pre-reactant states is important for the overall understanding of the kinetics and mechanism of the individual reactions...
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30745989/unexpected-loss-of-stereoselectivity-in-glycosylation-reactions-during-the-synthesis-of-chondroitin-sulfate-oligosaccharides
#9
Teresa Mena-Barragán, José L de Paz, Pedro M Nieto
Here, we present an exploratory study on the fluorous-assisted synthesis of chondroitin sulfate (CS) oligosaccharides. Following this approach, a CS tetrasaccharide was prepared. However, in contrast to our previous results, a significant loss of β-selectivity was observed in [2 + 2] glycosylations involving N -trifluoroacetyl-protected D-galactosamine donors and D-glucuronic acid (GlcA) acceptors. These results, together with those obtained from experiments employing model monosaccharide building blocks, highlight the impact of the glycosyl acceptor structure on the stereoselectivity of glycosylation reactions...
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30745988/systematic-synthetic-study-of-four-diastereomerically-distinct-limonene-1-2-diols-and-their-corresponding-cyclic-carbonates
#10
Hiroshi Morikawa, Jun-Ichi Yamaguchi, Shun-Ichi Sugimura, Masato Minamoto, Yuuta Gorou, Hisatoyo Morinaga, Suguru Motokucho
In order to produce versatile and potentially functional terpene-based compounds, a ( R )-limonene-derived diol and its corresponding five-membered cyclic carbonate were prepared. The diol (cyclic carbonate) comprises four diastereomers based on the stereochemical configuration of the diol (and cyclic carbonate) moiety. By choosing the appropriate starting compounds ( trans - and cis -limonene oxide) and conditions, the desired diastereomers were synthesised in moderate to high yields with, in most cases, high stereoselectivity...
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30680045/adhesion-forces-and-the-stability-of-interfaces
#11
Robin Guttmann, Johannes Hoja, Christoph Lechner, Reinhard J Maurer, Alexander F Sax
Weak molecular interactions (WMI) are responsible for processes such as physisorption; they are essential for the structure and stability of interfaces, and for bulk properties of liquids and molecular crystals. The dispersion interaction is one of the four basic interactions types - electrostatics, induction, dispersion and exchange repulsion - of which all WMIs are composed. The fact that each class of basic interactions covers a wide range explains the large variety of WMIs. To some of them, special names are assigned, such as hydrogen bonding or hydrophobic interactions...
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30680044/synthesis-of-a-tubugi-1-toxin-conjugate-by-a-modulizable-disulfide-linker-system-with-a-neuropeptide-y-analogue-showing-selectivity-for-hy1r-overexpressing-tumor-cells
#12
Rainer Kufka, Robert Rennert, Goran N Kaluđerović, Lutz Weber, Wolfgang Richter, Ludger A Wessjohann
Tubugi-1 is a small cytotoxic peptide with picomolar cytotoxicity. To improve its cancer cell targeting, it was conjugated using a universal, modular disulfide derivative. This allowed conjugation to a neuropeptide-Y (NPY)-inspired peptide [K4 (C-βA-),F7 ,L17 ,P34 ]-hNPY, acting as NPY Y1 receptor (hY1R)-targeting peptide, to form a tubugi-1-SS-NPY disulfide-linked conjugate. The cytotoxic impacts of the novel tubugi-1-NPY peptide-toxin conjugate, as well as of free tubugi-1, and tubugi-1 bearing the thiol spacer (liberated from tubugi-1-NPY conjugate), and native tubulysin A as reference were investigated by in vitro cell viability and proliferation screenings...
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30680043/fabrication-of-supramolecular-cyclodextrin-fullerene-nonwovens-by-electrospinning
#13
Hiroaki Yoshida, Ken Kikuta, Toshiyuki Kida
Direct electrospinning of small molecules has great potential to fabricate a new class of fiber materials because this approach realizes the creation of various functional materials through the numerous molecular combinations. In this paper, we demonstrate a proof-of-concept to fabricate supramolecular fiber materials composed of cyclodextrin (CD)-fullerene inclusion complexes by electrospinning. Similar to the molecular state of fullerenes in solution, the resulting fibers include molecularly-dispersed fullerenes...
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30680042/synthesis-biophysical-properties-and-rnase-h-activity-of-6-difluoro-4-3-0-bicyclo-dna
#14
Sibylle Frei, Adam K Katolik, Christian J Leumann
Here we present the synthesis, the biophysical properties, and the RNase H profile of 6'-difluorinated [4.3.0]bicyclo-DNA (6'-diF-bc4,3 -DNA). The difluorinated thymidine phosphoramidite building block was synthesized starting from an already known gem -difluorinated tricyclic glycal. This tricyclic siloxydifluorocyclopropane was converted into the [4.3.0]bicyclic nucleoside via cyclopropane ring-opening through the addition of an electrophilic iodine during the nucleosidation step followed by reduction. The gem -difluorinated bicyclic nucleoside was then converted into the corresponding phosphoramidite building block which was incorporated into oligonucleotides...
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30680041/regioselective-addition-of-grignard-reagents-to-n-acylpyrazinium-salts-synthesis-of-substituted-1-2-dihydropyrazines-and-%C3%AE-5-2-oxopiperazines
#15
Valentine R St Hilaire, William E Hopkins, Yenteeo S Miller, Srinivasa R Dandepally, Alfred L Williams
The regioselective addition of Grignard reagents to mono- and disubstituted N -acylpyrazinium salts affording substituted 1,2-dihydropyrazines in modest to excellent yields (45-100%) is described. Under acidic conditions, these 1,2-dihydropyrazines can be converted to substituted Δ5 -2-oxopiperazines providing a simple and efficient approach towards their preparation.
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30680040/gold-catalyzed-ethylene-cyclopropanation
#16
Silvia G Rull, Andrea Olmos, Pedro J Pérez
Ethylene can be directly converted into ethyl 1-cyclopropylcarboxylate upon reaction with ethyl diazoacetate (N2 CHCO2 Et, EDA) in the presence of catalytic amounts of IPrAuCl/NaBArF 4 (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene; BArF 4 = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate).
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30680039/asymmetric-synthesis-of-a-high-added-value-chiral-amine-using-immobilized-%C3%AF-transaminases
#17
Antonella Petri, Valeria Colonna, Oreste Piccolo
Chiral N-heterocyclic molecules and in particular compounds with an amino functional group such as 3-aminopiperidine are valuable intermediates for the production of a large number of bioactive compounds with pharmacological properties. In this paper, the synthesis of both enantiomers of 3-amino-1-Boc-piperidine by amination of the prochiral precursor 1-Boc-3-piperidone using immobilized ω-transaminases (TAs-IMB), isopropylamine as amine donor and pyridoxal-5'-phosphate (PLP) as cofactor is described. Compared to other methods, the present approach affords the target compound in just one step with high yield and high enantiomeric excess starting from a commercial substrate...
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30680038/-n-arylphenothiazines-as-strong-donors-for-photoredox-catalysis-pushing-the-frontiers-of-nucleophilic-addition-of-alcohols-to-alkenes
#18
Fabienne Speck, David Rombach, Hans-Achim Wagenknecht
A new range of N -phenylphenothiazine derivatives was synthesized as potential photoredox catalysts to broaden the substrate scope for the nucleophilic addition of methanol to styrenes through photoredox catalysis. These N -phenylphenothiazines differ by their electron-donating and electron-withdrawing substituents at the phenyl group, covering both, σ and π-type groups, in order to modulate their absorbance and electrochemical characteristics. Among the synthesized compounds, alkylaminylated N -phenylphenothiazines were identified to be highly suitable for photoredox catalysis...
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30680037/selective-ring-opening-metathesis-polymerization-romp-of-cyclobutenes-unsymmetrical-ladderphane-containing-polycyclobutene-and-polynorbornene-strands
#19
Yuan-Zhen Ke, Shou-Ling Huang, Guoqiao Lai, Tien-Yau Luh
At 0 °C in THF in the presence of Grubbs first generation catalyst, cyclobutene derivatives undergo ROMP readily, whereas norbornene derivatives remain intact. When the substrate contains both cyclobutene and norbornene moieties, the conditions using THF as the solvent at 0 °C offer a useful protocol for the selective ROMP of cyclobutene to give norbornene-appended polycyclobutene. Unsymmetrical ladderphane having polycyclobutene and polynorbornene as two strands is obtained by further ROMP of the norbornene appended polycyclobutene in the presence of Grubbs first generation catalyst in DCM at ambient temperature...
2019: Beilstein Journal of Organic Chemistry
https://read.qxmd.com/read/30680036/mechanistic-studies-of-an-l-proline-catalyzed-pyridazine-formation-involving-a-diels-alder-reaction-with-inverse-electron-demand
#20
Anne Schnell, J Alexander Willms, S Nozinovic, Marianne Engeser
The mechanism of an L-proline-catalyzed pyridazine formation from acetone and aryl-substituted tetrazines via a Diels-Alder reaction with inverse electron demand has been studied with NMR and with electrospray ionization mass spectrometry. A catalytic cycle with three intermediates has been proposed. An enamine derived from L-proline and acetone acts as an electron-rich dienophile in a [4 + 2] cycloaddition with the electron-poor tetrazine forming a tetraazabicyclo[2.2.2]octadiene derivative which then eliminates N2 in a retro-Diels-Alder reaction to yield a 4,5-dihydropyridazine species...
2019: Beilstein Journal of Organic Chemistry
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