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Beilstein Journal of Organic Chemistry

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https://www.readbyqxmd.com/read/27829932/a-new-and-expeditious-synthesis-of-all-enantiomerically-pure-stereoisomers-of-rosaprostol-an-antiulcer-drug
#1
Wiesława Perlikowska, Remigiusz Żurawiński, Marian Mikołajczyk
Four enantiomerically pure stereoisomers of rosaprostol (1), an antiulcer drug, were efficiently synthesized from the enantiomers of 2-(dimethoxyphosphoryl)-3-hexylcyclopentanone (3) as chiral substrates. The latter were obtained by resolution of racemic 3 with (+)-(R)-1-(1-naphthyl)ethylamine. The conversion of (+)-3 into rosaprostol stereoisomer (-)-1a was accomplished in four steps in 56% overall yield. According to the same protocol, the second stereoisomer (+)-1c was obtained from (-)-3 in 55% overall yield...
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829931/tunable-microwave-assisted-method-for-the-solvent-free-and-catalyst-free-peracetylation-of-natural-products
#2
Manuela Oliverio, Paola Costanzo, Monica Nardi, Carla Calandruccio, Raffaele Salerno, Antonio Procopio
Background: The peracetylation is a simple chemical modification that can be used to enhance the bioavailability of hydrophilic products and to obtain safe and stable pro-drugs. Results: A totally green, solvent-free and catalyst-free microwave (MW)-assisted method for peracetylation of natural products such as oleuropein, alpha-hederin, quercetin and rutin is presented. By simply tuning the MW heating program, polyols with chemical diverse -OH groups or thermolabile functionalities can be peracetylated to improve the biological activity without degradation of the natural starting molecules...
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829930/organometallic-chemistry
#3
EDITORIAL
Bernd F Straub, Rolf Gleiter, Claudia Meier, Lutz H Gade
No abstract text is available yet for this article.
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829929/determination-of-the-absolute-stereostructure-of-a-cyclic-azobenzene-from-the-crystal-structure-of-the-precursor-containing-a-heavy-element
#4
Reji Thomas, Nobuyuki Tamaoki
Single crystal X-ray diffraction has been used as one of the common methods for the unambiguous determination of the absolute stereostructure of chiral molecules. However, this method is limited to molecules containing heavy atoms or to molecules with the possibility of functionalization with heavy elements or chiral internal references. Herein, we report the determination of the absolute stereostructure of the enantiomers of molecule (E)-2, which lacks the possibility of functionalization, using a reverse method, i...
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829928/stereoselective-synthesis-of-fused-tetrahydroquinazolines-through-one-pot-double-3-2-dipolar-cycloadditions-followed-by-5-1-annulation
#5
Xiaofeng Zhang, Kenny Pham, Shuai Liu, Marc Legris, Alex Muthengi, Jerry P Jasinski, Wei Zhang
The one-pot [3 + 2] cycloaddition of an azomethine ylide with a maleimide followed by another [3 + 2] cycloaddition of an azide with the second maleimide gives a 1,5-diamino intermediate which is used for a sequential aminomethylation reaction with formaldehyde through [5 + 1] annulation to afford a novel polycyclic scaffold bearing tetrahydroquinazoline, pyrrolidine, pyrrolidinedione, and N-substituted maleimide in stereoselective fashion.
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829927/regiocontroled-pd-catalysed-c5-arylation-of-3-substituted-thiophene-derivatives-using-a-bromo-substituent-as-blocking-group
#6
Mariem Brahim, Hamed Ben Ammar, Jean-François Soulé, Henri Doucet
The use of a bromo-substituent as blocking group at the C2-position of 3-substituted thiophenes allows the regioselective introduction of aryl substituents at C5-position via Pd-catalysed direct arylation. With 1 mol % of a phosphine-free Pd catalyst, KOAc as the base and DMA as the solvent and various electron-deficient aryl bromides as aryl sources, C5-(hetero)arylated thiophenes were synthesized in moderate to high yields, without cleavage of the thienyl C-Br bond. Moreover, sequential direct thienyl C5-arylation followed by Pd-catalysed direct arylation or Suzuki coupling at the C2-position allows to prepare 2,5-di(hetero)arylated thiophenes bearing two different (hetero)aryl units in only two steps...
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829926/palladium-catalyzed-ring-opening-reactions-of-cyclopropanated-7-oxabenzonorbornadiene-with-alcohols
#7
Katrina Tait, Oday Alrifai, Rebecca Boutin, Jamie Haner, William Tam
Palladium-catalyzed ring-opening reactions of cyclopropanated 7-oxabenzonorbornadiene derivatives using alcohol nucleophiles were investigated. The optimal conditions were found to be 10 mol % PdCl2(CH3CN)2 in methanol, offering yields up to 92%. The reaction was successful using primary, secondary and tertiary alcohol nucleophiles and was compatible with a variety of substituents on cyclopropanated oxabenzonorbornadiene. With unsymmetrical C1-substituted cyclopropanated 7-oxabenzonorbornadienes, the regioselectivity of the reaction was excellent, forming only one regioisomer in all cases...
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829925/diels-alder-reactions-in-confined-spaces-the-influence-of-catalyst-structure-and-the-nature-of-active-sites-for-the-retro-diels-alder-reaction
#8
Ángel Cantín, M Victoria Gomez, Antonio de la Hoz
Diels-Alder cycloaddition between cyclopentadiene and p-benzoquinone has been studied in the confined space of a pure silica zeolite Beta and the impact on reaction rate due to the concentration effect within the pore and diffusion limitations are discussed. Introduction of Lewis or Brønsted acid sites on the walls of the zeolite strongly increases the reaction rate. However, contrary to what occurs with mesoporous molecular sieves (MCM-41), Beta zeolite does not catalyse the retro-Diels-Alder reaction, resulting in a highly selective catalyst for the cycloaddition reaction...
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829924/silica-supported-sulfonic-acids-as-recyclable-catalyst-for-esterification-of-levulinic-acid-with-stoichiometric-amounts-of-alcohols
#9
Raimondo Maggi, N Raveendran Shiju, Veronica Santacroce, Giovanni Maestri, Franca Bigi, Gadi Rothenberg
Converting biomass into value-added chemicals holds the key to sustainable long-term carbon resource management. In this context, levulinic acid, which is easily obtained from cellulose, is valuable since it can be transformed into a variety of industrially relevant fine chemicals. Here we present a simple protocol for the selective esterification of levulinic acid using solid acid catalysts. Silica supported sulfonic acid catalysts operate under mild conditions and give good conversion and selectivity with stoichiometric amounts of alcohols...
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829923/evidence-for-an-iterative-module-in-chain-elongation-on-the-azalomycin-polyketide-synthase
#10
Hui Hong, Yuhui Sun, Yongjun Zhou, Emily Stephens, Markiyan Samborskyy, Peter F Leadlay
The assembly-line synthases that produce bacterial polyketide natural products follow a modular paradigm in which each round of chain extension is catalysed by a different set or module of enzymes. Examples of deviation from this paradigm, in which a module catalyses either multiple extensions or none are of interest from both a mechanistic and an evolutionary viewpoint. We present evidence that in the biosynthesis of the 36-membered macrocyclic aminopolyol lactones (marginolactones) azalomycin and kanchanamycin, isolated respectively from Streptomyces malaysiensis DSM4137 and Streptomyces olivaceus Tü4018, the first extension module catalyses both the first and second cycles of polyketide chain extension...
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829922/comparing-blends-and-blocks-synthesis-of-partially-fluorinated-diblock-polythiophene-copolymers-to-investigate-the-thermal-stability-of-optical-and-morphological-properties
#11
Pierre Boufflet, Sebastian Wood, Jessica Wade, Zhuping Fei, Ji-Seon Kim, Martin Heeney
The microstructure of the active blend layer has been shown to be a critically important factor in the performance of organic solar devices. Block copolymers provide a potentially interesting avenue for controlling this active layer microstructure in solar cell blends. Here we explore the impact of backbone fluorination in block copolymers of poly(3-octyl-4-fluorothiophene)s and poly(3-octylthiophene) (F-P3OT-b-P3OT). Two block co-polymers with varying block lengths were prepared via sequential monomer addition under Kumada catalyst transfer polymerisation (KCTP) conditions...
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829921/synthesis-of-medronic-acid-monoesters-and-their-purification-by-high-performance-countercurrent-chromatography-or-by-hydroxyapatite
#12
Elina Puljula, Jouko Vepsäläinen, Petri A Turhanen
We achieved the synthesis of important medronic acid monoalkyl esters via the dealkylation of mixed trimethyl monoalkyl esters of medronic acid. Two methods were developed for the purification of medronic acid monoesters: 1) small scale (10-20 mg) purification by using hydroxyapatite and 2) large scale (tested up to 140 mg) purification by high-performance countercurrent chromatography (HPCCC).
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829920/dna-functionalization-by-dynamic-chemistry
#13
Zeynep Kanlidere, Oleg Jochim, Marta Cal, Ulf Diederichsen
Dynamic combinatorial chemistry (DCC) is an attractive method to efficiently generate libraries of molecules from simpler building blocks by reversible reactions under thermodynamic control. Here we focus on the chemical modification of DNA oligonucleotides with acyclic diol linkers and demonstrate their potential for the deoxyribonucleic acid functionalization and generation of libraries of reversibly interconverting building blocks. The syntheses of phosphoramidite building blocks derived from D-threoninol are presented in two variants with protected amino or thiol groups...
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829919/superelectrophilic-activation-of-5-hydroxymethylfurfural-and-2-5-diformylfuran-organic-synthesis-based-on-biomass-derived-products
#14
Dmitry S Ryabukhin, Dmitry N Zakusilo, Mikhail O Kompanets, Anton A Tarakanov, Irina A Boyarskaya, Tatiana O Artamonova, Mikhail A Khohodorkovskiy, Iosyp O Opeida, Aleksander V Vasilyev
The reaction of 5-hydroxymethylfurfural (5-HMF) with arenes in superacidic trifluoromethanesulfonic acid (triflic acid, TfOH) as the solvent at room temperature for 1-24 h gives rise to 5-arylmethylfurfurals (yields of 17-91%) and 2-arylmethyl-5-(diarylmethyl)furans (yields of 10-37%). The formation of these two types of reaction products depends on the nucleophilicity of the arene. The same reactions under the action of acidic zeolites H-USY in high pressure tubes at 130 °C for 1 h result in the formation of only 5-arylmethylfurfurals (yields of 45-79%)...
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829918/correction-recent-advances-in-n-heterocyclic-carbene-nhc-catalysed-benzoin-reactions
#15
Rajeev S Menon, Akkattu T Biju, Vijay Nair
[This corrects the article DOI: 10.3762/bjoc.12.47.].
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829917/the-direct-oxidative-diene-cyclization-and-related-reactions-in-natural-product-synthesis
#16
REVIEW
Juliane Adrian, Leona J Gross, Christian B W Stark
The direct oxidative cyclization of 1,5-dienes is a valuable synthetic method for the (dia)stereoselective preparation of substituted tetrahydrofurans. Closely related reactions start from 5,6-dihydroxy or 5-hydroxyalkenes to generate similar products in a mechanistically analogous manner. After a brief overview on the history of this group of transformations and a survey on mechanistic and stereochemical aspects, this review article provides a summary on applications in natural product synthesis. Moreover, current limitations and future directions in this area of chemistry are discussed...
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829916/chiral-ammonium-betaine-catalyzed-asymmetric-mannich-type-reaction-of-oxindoles
#17
Masahiro Torii, Kohsuke Kato, Daisuke Uraguchi, Takashi Ooi
A highly diastereo- and enantioselective Mannich-type reaction of 3-aryloxindoles with N-Boc aldimines was achieved under the catalysis of axially chiral ammonium betaines. This catalytic method provides a new tool for the construction of consecutive quaternary and tertiary stereogenic carbon centers on biologically intriguing molecular frameworks with high fidelity.
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829915/diastereoselective-synthesis-of-3-4-dihydro-2h-pyran-4-carboxamides-through-an-unusual-regiospecific-quasi-hydrolysis-of-a-cyano-group
#18
Mikhail Yu Ievlev, Oleg V Ershov, Mikhail Yu Belikov, Angelina G Milovidova, Viktor A Tafeenko, Oleg E Nasakin
An efficient diastereoselective approach for the synthesis of functionalized 3,4-dihydro-2H-pyran-4-carboxamides with variable frame was developed based on the reaction of available 4-oxoalkane-1,1,2,2-tetracarbonitriles (adducts of TCNE and ketones) with aldehydes in an acidic media. An unusual process of quasi hydrolysis of the cyano group was observed in the course of the described regio- and diastereoselective transformation.
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829914/p-nitrophenyl-carbonate-promoted-ring-opening-reactions-of-dbu-and-dbn-affording-lactam-carbamates
#19
Madhuri Vangala, Ganesh P Shinde
The amidine bases DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) and DBN (1,5-diazabicyclo[4.3.0]non-5-ene) display nucleophilic behaviour towards highly electrophilic p-nitrophenyl carbonate derivatives with ring opening of the bicyclic ring to form corresponding substituted ε-caprolactam and γ-lactam derived carbamates. This simple method presents a unified strategy to synthesize structurally diverse ε-caprolactam and γ-lactam compounds with a large substrate scope.
2016: Beilstein Journal of Organic Chemistry
https://www.readbyqxmd.com/read/27829913/new-furoisocoumarins-and-isocoumarins-from-the-mangrove-endophytic-fungus-aspergillus-sp-085242
#20
Ze'en Xiao, Senhua Chen, Runlin Cai, Shao'e Lin, Kui Hong, Zhigang She
The chemical investigation of the mangrove endophytic fungus Aspergillus sp. 085242 afforded eight isocoumarin derivatives 1-8 and one isoquinoline 9. Asperisocoumarins A and B (1 and 2) were new furoisocoumarins, and asperisocoumarins E and F (5 and 6) were new isocoumarins. Their structures were established by analysis of their spectroscopic data and the absolute configuration of compound 2 was unambiguously determined by X-ray structure analysis and ECD calculation. Moreover, the absolute configurations of compounds 3-5 were assigned by comparison of their ECD spectra with isocoumarins described in the literature...
2016: Beilstein Journal of Organic Chemistry
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