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European Journal of Organic Chemistry

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https://www.readbyqxmd.com/read/28736501/design-of-radioiodinated-pharmaceuticals-structural-features-affecting-metabolic-stability-towards-in-vivo-deiodination
#1
REVIEW
Lorenzo Cavina, Dion van der Born, Peter H M Klaren, Martin C Feiters, Otto C Boerman, Floris P J T Rutjes
Radioiodinated pharmaceuticals are convenient tracers for clinical and research investigations because of the relatively long half-lives of radioactive iodine isotopes (i.e., (123)I, (124)I, and (131)I) and the ease of their chemical insertion. Their application in radionuclide imaging and therapy may, however, be hampered by poor in vivo stability of the C-I bond. After an overview of the use of iodine in biology and nuclear medicine, we present here a survey of the catabolic pathways for iodinated xenobiotics, including their biodistribution, accumulation, and biostability...
June 30, 2017: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28529446/synthesis-of-chiral-tetrahydrofurans-and-pyrrolidines-by-visible-light-mediated-deoxygenation
#2
Daniel Rackl, Viktor Kais, Eugen Lutsker, And Oliver Reiser
The synthesis of chiral tetrahydrofurans and pyrrolidines starting from 1,2-diols or β-amino alcohols, respectively, by visible-light-mediated deoxygenation is described. Easily accessible monoallylated/propargylated substrates were activated either as inexpensive ethyl oxalates or as recyclable 3,5-bis(trifluoromethyl)benzoates to generate alkyl radicals suitable for 5-exo-trig/5-exo-dig cyclizations under visible-light irradiation.
April 18, 2017: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28533701/local-desymmetrization-through-diastereotopic-group-selection-an-enabling-strategy-for-natural-product-synthesis
#3
Matthew A Horwitz, Jeffrey S Johnson
The application of desymmetrization strategies in chemical synthesis has allowed fundamentally new synthetic sequences that efficiently create dense and polyfunctional stereochemical arrays. Enantiotopic group discrimination has become a well-established method of global desymmetrization, while the conceptually unique strategy of local desymmetrization by diastereotopic group discrimination has its own advantages. This microreview focuses on the application of local desymmetrization in natural product synthesis and places a particular emphasis on the efficiency engendered by diastereotopic group discrimination...
March 17, 2017: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28344504/stereoselective-synthesis-of-functionalized-bicyclic-scaffolds-by-passerini-3-center-2-component-reactions-of-cyclic-ketoacids
#4
Răzvan C Cioc, Verónica Estévez, Daan J van der Niet, Christophe M L Vande Velde, Nikolaus G Turrini, Mélanie Hall, Kurt Faber, Eelco Ruijter, Romano V A Orru
We report the use of bifunctional starting materials (ketoacids) in a diastereoselective Passerini three-center-two-component reaction. Study of the reaction scope revealed the required structural features for stereoselectivity in the isocyanide addition. In this system, an interesting isomerization of the primary Passerini product - the α-carboxamido lactone - into an atypical product, an α-hydroxy imide, was found to occur under acidic conditions. Furthermore, enantioenriched Passerini products can be generated from an enantioenriched ketoacid obtained by chemoenzymatic synthesis...
March 3, 2017: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28344503/metal-catalysed-azidation-of-organic-molecules
#5
REVIEW
Monalisa Goswami, Bas de Bruin
The azide moiety is a desirable functionality in organic molecules, useful in a variety of transformations such as olefin aziridination, C-H bond amination, isocyanate synthesis, the Staudinger reaction and the formation of azo compounds. To harness the versatility of the azide functionality fully it is important that these compounds be easy to prepare, in a clean and cost-effective manner. Conventional (non-catalysed) methods to synthesise azides generally require quite harsh reaction conditions that are often not tolerant of functional groups...
February 24, 2017: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28286413/optimising-terpene-synthesis-with-flow-biocatalysis
#6
Xiaoping Tang, Rudolf K Allemann, Thomas Wirth
Sesquiterpenes are an important family of natural products, many of which exhibit important pharmaceutical and agricultural properties. They are biosynthesised from farnesyl diphosphate in sesquiterpene synthase catalysed reactions. Here, we report the development of a highly efficient segmented flow system for the enzyme-catalysed continuous flow production of sesquiterpenes. Design of experiment (DoE) methods were used to optimise the performance of the flow biocatalysis, and quantitative yields were achieved by using an operationally simple but highly effective segmented flow system...
January 10, 2017: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28479872/a-cu-catalysed-radical-cross-dehydrogenative-coupling-approach-to-acridanes-and-related-heterocycles
#7
Timothy E Hurst, Richard J K Taylor
The synthesis of acridanes and related compounds through a Cu-catalysed radical cross-dehydrogenative coupling of simple 2-[2-(arylamino)aryl]malonates is reported. This method can be further streamlined to a one-pot protocol involving the in situ fomation of the 2-[2-(arylamino)aryl]malonate by α-arylation of diethyl malonate with 2-bromodiarylamines under Pd catalysis, followed by Cu-catalysed cyclisation.
January 3, 2017: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28111524/divergent-synthesis-of-quinolone-natural-products-from-pseudonocardia-sp-cl38489
#8
Stephen M Geddis, Laura Carro, James T Hodgkinson, David R Spring
Two divergent synthetic routes are reported offering access to four quinolone natural products from Pseudonocardia sp. CL38489. Key steps to the natural products involved a regioselective epoxidation, an intramolecular Buchwald-Hartwig amination and a final acid-catalysed 1,3-allylic-alcohol rearrangement to give two of the natural products in one step. This study completes the synthesis of all eight antibacterial quinolone natural products reported in the family. In addition, this modular strategy enables an improved synthesis towards two natural products previously reported...
December 2016: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28111523/native-serine-peptide-assembly-scope-and-utility
#9
Michael C Pirrung, Ryan S Schreihans
This work develops serine peptide assembly (SPA), which complements and contrasts with classic native chemical ligation (NCL). Advances in reagent-less peptide bond formation have been applied to serine (and serine models) and a range of C-terminal amino acids, including bulky residues that are not amenable to NCL. The particular appeal of SPA is preparative-scale segment condensations with zero racemization risk and favourable process mass intensity (PMI). Mechanistic studies support a previously proposed reaction pathway via an initial trans-esterification step...
December 2016: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27917069/stereochemical-control-of-enzymatic-carbon-carbon-bond-forming-michael-type-additions-by-substrate-engineering
#10
Yufeng Miao, Pieter G Tepper, Edzard M Geertsema, Gerrit J Poelarends
The enzyme 4-oxalocrotonate tautomerase (4-OT) promiscuously catalyzes the Michael-type addition of acetaldehyde to β-nitrostyrene derivatives to yield chiral γ-nitroaldehydes, which are important precursors for pharmaceutically active γ-aminobutyric acids. In this study, we investigated the effect of different substituents at the aromatic ring of the Michael acceptor on the catalytic efficiency and stereoselectivity of the 4-OT-catalyzed acetaldehyde addition reactions. Highly enantioenriched (R)- and (S)-γ-nitroaldehydes and 4-substituted chroman-2-ol could be obtained in good to excellent yields by applying different substituents at appropriate positions of the aromatic substrate...
November 2016: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28082832/asymmetric-dearomatization-cyclization-enables-access-to-polycyclic-chemotypes
#11
Mikayo Hayashi, Lauren E Brown, John A Porco
Enantioenriched, polycyclic compounds were obtained from a simple acylphloroglucinol scaffold. Highly enantioselective dearomatization was accomplished using a Trost ligand-palladium(0) complex. A computational DFT model was developed to rationalize observed enantioselectivities and revealed a key reactant-ligand hydrogen bonding interaction. Dearomatized products were used in visible light-mediated photocycloadditions and oxidative free radical cyclizations to obtain novel polycyclic chemotypes including tricyclo[4...
October 2016: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28042283/synthesis-of-a-ribose-incorporating-medium-ring-scaffold-via-a-challenging-ring-closing-metathesis-reaction
#12
Stuart S Rankin, John J Caldwell, Nora B Cronin, Rob L M van Montfort, Ian Collins
A practical synthesis of a novel oxabicyclo[6.2.1]undecenetriol useful as a medicinal chemistry scaffold has been developed starting from l-ribose. The sequence involves an oxidation/Grignard addition sequence and a challenging ring-closing metathesis (RCM) reaction as the ring forming step. Exploration of the RCM substrate protecting groups revealed the key factor for successful nine-membered medium ring formation to be conformational bias of the reacting alkenes of the RCM substrate by very bulky silyl ether protecting groups...
September 2016: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27840588/the-amadori-rearrangement-for-carbohydrate-conjugation-scope-and-limitations
#13
Cornelia Hojnik, Anne Müller, Tobias-Elias Gloe, Thisbe K Lindhorst, Tanja M Wrodnigg
The Amadori rearrangement was investigated for the synthesis of C-glycosyl-type neoglycoconjugates. Various amines including diamines, amino-functionalized glycosides, lysine derivatives, and peptides were conjugated with two different heptoses to generate non-natural C-glycosyl-type glycoconjugates of the d-gluco and d-manno series. With these studies, the scope and limitations of the Amadori rearrangement as a conjugation method have been exemplified with respect to the carbohydrate substrate, as well as the amino components...
September 2016: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27840587/efficient-o-acylation-of-alcohols-and-phenol-using-cp2ticl-as-a-reaction-promoter
#14
María Jesús Durán-Peña, José Manuel Botubol-Ares, James R Hanson, Rosario Hernández-Galán, Isidro G Collado
A method has been developed for the conversion of primary, secondary, and tertiary alcohols, and phenol, into the corresponding esters at room temperature. The method uses a titanium(III) species generated from a substoichiometric amount of titanocene dichloride together with manganese(0) as a reductant, as well as methylene diiodide. It involves a transesterification from an ethyl ester, or a reaction with an acyl chloride. A radical mechanism is proposed for these transformations.
July 2016: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27840586/strigolactone-analogues-with-a-d-ring-modified-at-c-2
#15
Alinanuswe S Mwakaboko, Binne Zwanenburg
Strigolactones (SLs) are important new plant hormones that receive much attention in current plant science. SLs are produced by many plants and are exuded by the root system. SLs are, amongst others, germination stimulants for seed of parasitic weeds. Naturally occurring SLs invariably contain three annelated rings, the ABC-scaffold, connected to a butenolide (the D-ring) via an enol ether unit. The synthesis of natural SLs requires many steps, therefore there is a continuous search for SL analogues with a simpler structure but with retention of bioactivity...
July 2016: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27774038/synthesis-of-a-crushed-fullerene-c60h24-through-sixfold-palladium-catalyzed-arylation
#16
Ruth Dorel, Paula de Mendoza, Pilar Calleja, Sergio Pascual, Esther González-Cantalapiedra, Noemí Cabello, Antonio M Echavarren
The synthesis of a new C3v -symmetric crushed fullerene C60H24 (5) has been accomplished in three steps from truxene through sixfold palladium-catalyzed intramolecular arylation of a syn-trialkylated truxene precursor. Laser irradiation of 5 induces cyclodehydrogenation processes that result in the formation of C60, as detected by LDI-MS.
July 2016: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28670172/new-three-component-bicyclization-leading-to-densely-functionalized-pyrazolo-3-4-d-thiazolo-3-2-a-pyrimidines
#17
Wen-Juan Hao, Peng Zhou, Fei-Yue Wu, Bo Jiang, Shu-Jiang Tu, Guigen Li
A novel three-component bicyclization for the efficient synthesis of densely functionalized pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidines has been established from readily accessible aryl aldehydes, α-thiocyanate ketones and pyrazol-5-amines. The reaction pathway involves nucleophilic addition/5-exo-trig /6-endo-trig bicyclization sequence, resulting in continuous multiple bond-forming events including C-N and C-C bonds to rapidly a molecular complexity.
April 2016: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28090188/enantioselective-synthesis-of-caprolactam-and-enone-precursors-to-the-heterocyclic-defg-ring-system-of-zoanthenol
#18
Jeffrey T Bagdanoff, Douglas C Behenna, Jennifer L Stockdill, Brian M Stoltz
The enantioselective synthesis of both caprolactam and enone synthons for the DEFG ring system of zoanthenol are described. The evolution of this synthetic approach proceeds first through a synthesis using the chiral pool as a starting point. Challenges in protecting group strategy led to the modification of this approach beginning with (±)-glycidol. Ultimately, an efficient approach was developed by employing an asymmetric hetero-Diels-Alder reaction. The caprolactam building block can be converted by an interesting selective Grignard addition to the corresponding enone synthon...
April 2016: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28663711/gap-peptide-synthesis-via-design-of-new-gap-protecting-group-an-fmoc-tbu-synthesis-of-thymopentin-free-from-polymers-chromatography-and-recrystallization
#19
Cole W Seifert, Armando Paniagua, Gabrielle A White, Lucy Cai, Guigen Li
A novel method for Fmoc/tBu solution-phase peptide synthesis and the development of a new benzyl-type GAP protecting group is reported. This new GAP protecting group is utilized in place of a polymer support, facilitating C→N Fmoc peptide synthesis without chromatography, recrystallization, or polymer supports. The GAP group can be added and removed in high yield, and was used to synthesize over 1 gram of the immunostimulant, thymopentin, in high overall yield (83%) and purity (99%).
March 2016: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27790071/macrosteres-the-deltic-guanidinium-ion
#20
Kenji Mishiro, Fanghao Hu, Daniel W Paley, Wei Min, Tristan H Lambert
The "deltic guanidinium" ion is described here as a "macrostere" of the guanidinium ion. The use of the 2,4-dimethoxybenzyl protecting group allows for the synthesis of the fully unsubstituted parent compound and a variety of derivatives bearing multiple N-H functions for the first time. Deltic urea, deltic thiourea, and deltic benzamidine are also synthesized. A comparison of the physical properties of guanidinium and deltic guanidinium ions is provided. The use of a deltic guanidinium dendrimer for cell transport is demonstrated...
March 2016: European Journal of Organic Chemistry
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