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European Journal of Organic Chemistry

Iosune Arrastia, Ana Arrieta, Fernando P Cossío
The (3+2) cycloaddition between azomethine ylides and alkenes is an efficient, convergent and stereocontrolled method for the synthesis of unnatural pyrrolidine and proline scaffolds. In this review, the application of this reaction to the synthesis of enantiopure organometallic ligands for asymmetric catalysis is presented first. These new EhuPhos ligands can participate in a second generation of 1,3-dipolar reactions that generate an offspring of unnatural proline derivatives that behave as efficient organocatalysts...
November 25, 2018: European Journal of Organic Chemistry
Ivan Bernar, Daniel Blanco-Ania, Sophie J Stok, Lia Sotorríos, Enrique Gómez-Bengoa, Floris P J T Rutjes
A completely regioselective and highly stereoselective palladium-catalyzed intramolecular hydroarylation of arenesulfonyl ynamines to benzothiazoles was developed. The presence of an electron-withdrawing group on the triple bond of the sulfonyl ynamine was crucial for the success of the reaction and our mechanistic studies suggest an alkyne-directed 5- exo -dig cyclization pathway. The products easily underwent photoinduced rearrangement to 3-amino-1-benzothiophene-1,1-diones (up to 35 % yields after two steps)...
October 24, 2018: European Journal of Organic Chemistry
Mariia V Ishutkina, Alice R Berry, Rohanah Hussain, Olga G Khelevina, Giuliano Siligardi, Eugen Stulz
The formation of chromophore arrays using a DNA templating approach leads to the creation of supramolecular assemblies, where the optical properties of the overall system can be fine-tuned to a large extent. In particular, porphyrin derivatives have been shown to be versatile building blocks; mostly covalent chemistry was used for embedding the units into DNA strands. Self-assembly of porphyrin modified nucleosides, on the other hand, has not been investigated as a simplified approach. We report on the synthesis of a magnesium(II) tetraaza porphine (MgTAP) coupled to deoxyuridine, and array formation on DNA templates which contain well-defined oligo(dA) segments showing strong fluorescence enhancement which is significantly larger than that with a Zn-porphyrin...
September 30, 2018: European Journal of Organic Chemistry
Rene Ebule, Gerald B Hammond, Bo Xu
We report a novel method for the chlorothiolation of alkenes using HCl and sulfoxides to achieve the 1,2-difunctionalization of unactivated alkenes. The combination of our new HCl reagent (HCl/DMPU) with sulfoxides forms a unique chlorothiolation system. Both terminal and internal alkenes are suitable substrates. This method works at gram scale and is applicable in further synthetic elaborations.
September 16, 2018: European Journal of Organic Chemistry
Ilaria Calloni, Luca Unione, Gonzalo Jiménez-Osés, Francisco Corzana, Linda Del Bino, Alessio Corrado, Olimpia Pitirollo, Cinzia Colombo, Luigi Lay, Roberto Adamo, Jesús Jiménez-Barbero
Neisseria meningitidis serogroup A (MenA) is an aerobic diplococcal Gram-negative bacterium responsible for epidemic meningitis disease. Its capsular polysaccharide (CPS) has been identified as the primary virulence factor of MenA. This polysaccharide suffers from chemical lability in water. Thus, the design and synthesis of novel and hydrolytically stable structural analogues of MenA CPS may provide additional tools for the development of therapies against this disease. In this context, the structural features of the natural phosphorylated monomer have been analyzed and compared to those of its carba-analogue, where the endocyclic oxygen has been replaced by a methylene moiety...
September 9, 2018: European Journal of Organic Chemistry
Tyler J Potter, Yuantao Li, Michael D Ward, Jonathan A Ellman
The Rh(III)-catalyzed synthesis of 4-substituted isoquinolones and 2-pyridones by the annulation of N -methoxyamides and nitroalkenes has been developed. Both aliphatic and aromatic nitroalkenes were effective inputs. Annulations also proceeded for aromatic, alkenyl, and heteroaromatic C-H bond starting materials. Moreover, benzoic acid provided a novel nitrodihydroisocoumarin. The structure and relative stereochemistry of this compound, which is an oil at room temperature, was determined unambiguously by single crystal X-ray diffraction of its inclusion complex with a hydrogen-bonded host framework...
August 31, 2018: European Journal of Organic Chemistry
Samantha M Gibson, Jarryl M D'Oyley, Joe I Higham, Kate Sanders, Victor Laserna, Abil E Aliev, Tom D Sheppard
In this paper we outline how dihalohydration reactions of propargylic alcohols can be used to access a wide variety of useful halogenated building blocks. A novel procedure for dibromohydration of alkynes has been developed, and a selection of dichloro and dibromo diols and cyclic ethers were synthesized. The dihalohydration of homo-propargylic alcohols provides a useful route to 3-halofurans, which were shown to readily undergo cycloaddition reactions under mild conditions. Finally, a novel ring expansion of propargylic alcohols containing a cyclopropylalkyne provides access to halogenated alkenylcyclobutanes...
August 7, 2018: European Journal of Organic Chemistry
Anna Sadurní, Ryan Gilmour
A systematic study of the addition of C -based nucleophiles to fluorinated lactones based on 2-deoxy-2-fluoro-d-pyranoses is disclosed. This high yielding, α-selective process was found to be independent on the nature or configuration [( R )-C(sp3 )-F, ( S )-C(sp3 )-F] of the substituent at C2 . Representative, fluorinated analogues of Trehalose, Carminic acid, and the spirocyclic cores of Tofogliflozin and Papulacandin D are also reported. These glycomimics constitute a valuable series of 19 F NMR active probes for application in structural biology...
August 1, 2018: European Journal of Organic Chemistry
Fabian Fischer, Marko Hapke
The robust CoI precatalyst [CpCo(P{OEt}3 )( trans -MeO2 CHC=CHCO2 Me)] was investigated in cyclotrimerizations, furnishing benzenes and pyridines from triynes, diynes and nitriles, comparing the influence of different ways of energy supply; namely, irradiation and conventional (thermal) or microwave heating. The precatalyst was found to work under all conditions, including the possibility to catalyze cyclotrimerizations at room temperature under photochemical conditions at longer reaction times. Performance of the reactions in a microwave reactor proved to be the most time-efficient way to rapidly assemble the expected reaction products; however, careful selection of reaction conditions can be required...
June 29, 2018: European Journal of Organic Chemistry
Julia Weber, Markus Schwarz, Andrea Schiefer, Christian Hametner, Georg Häubl, Johannes Fröhlich, Hannes Mikula
The synthesis of (2-nitrophenyl)acetyl (NPAc)-protected glucosyl donors is described that were designed for the neighboring-group assisted glucosylation of base-labile natural products also being sensitive to hydrogenolysis. Glycosylation conditions were optimized using a trichloroacetimidate glucosyl donor, and cyclohexylmethanol and (+)-menthol as model acceptors. The approach was then extended to a one-pot procedure for the synthesis of 1,2- trans -glycosides. This method was finally applied for improved synthesis of the masked mycotoxin T2- O -β,d-glucoside...
June 7, 2018: European Journal of Organic Chemistry
Sarah H Hewitt, Andrew J Wilson
Dynamic combinatorial chemistry (DCC) represents an approach, whereby traditional supramolecular scaffolds used for protein surface recognition might be exploited to achieve selective high affinity target recognition. Synthesis, in situ screening and amplification under selection pressure allows the generation of ligands, which bear different moieties capable of making multivalent non-covalent interactions with target proteins. Generic tetracarboxyphenyl porphyrin scaffolds bearing four hydrazide moieties have been used to form dynamic combinatorial libraries (DCLs) using aniline-catalyzed reversible hydrazone exchange reactions, in 10 % DMSO, 5 mm NH4 OAc, at pH 6...
April 30, 2018: European Journal of Organic Chemistry
Xiao Lu, Myunghoon Kim, Meghan J Orr, Hao Li, Wenwei Huang
An acid-promoted cascade reaction of 4-chloroquinolin-3-yl carbamates with amines is described. This method achieves the formation of two new C-N bonds through an intermolecular amination/intramolecular cyclization reaction sequence. In combination with subsequent Suzuki coupling, this three-component telescopic procedure provides rapid access to various bioactive imidazo[4,5- c ]quinolin-2-one derivatives.
April 9, 2018: European Journal of Organic Chemistry
Jennifer C Walters, Anthony F Tierno, Aimee H Dubin, Sarah E Wengryniuk
Herein, we report a simplified approach to the synthesis of medium-ring ethers through the electrophilic activation of secondary alcohols with (poly)cationic λ3 -iodanes ( N -HVI). Excellent levels of selectivity are achieved for C-O bond migration over established α-elimination pathways, enabled by the unique reactivity of a novel 2-OMe-pyridine-ligated N -HVI. The resulting HFIP-acetals are readily derivatized with a range of nucleophiles, providing a versatile functional handle for subsequent manipulations...
March 29, 2018: European Journal of Organic Chemistry
Markus Menke, Kristina Melnik, Pardha S Peram, Iris Starnberger, Walter Hödl, Miguel Vences, Stefan Schulz
Some amphibians use chemical signals in addition to optical and acoustical signals to transmit information. Males of mantellid frogs from Madagascar and hyperoliid frogs from Africa emit complex, species- and sex-specific bouquets of volatiles from their femoral or gular glands. We report here on the identification, synthesis, and determination of the absolute configuration of a macrocyclic lactone occurring in several species of both families, ( S )-3,7,11-dodec-6,10-dien-12-olide ( S - 14 , frogolide). Macrolides are a preferred compound class of frog volatiles...
March 24, 2018: European Journal of Organic Chemistry
Bo Yang, Weizhun Yang, Sherif Ramadan, Xuefei Huang
Due to the wide presence of carbohydrates in nature and their crucial roles in numerous important biological processes, oligosaccharides have attracted a lot of attention in synthetic organic chemistry community. Many innovative synthetic methods have been developed for oligosaccharide synthesis, among which the pre-activation based glycosylation is particularly noteworthy. Traditionally, glycosylation reactions are carried out when the glycosyl donor and the acceptor are both present when the promoter is added...
March 7, 2018: European Journal of Organic Chemistry
Michael Winter, Christina Gaunersdorfer, Lukas Roiser, Katharina Zielke, Uwe Monkowius, Mario Waser
The use of carbonyl-stabilized ammonium- and sulfonium ylides allows for the synthesis of highly-functionalized trifluoroacetyl-substituted cyclopropanes. It turned out that the diastereoselectivities strongly depend on the nature of the chosen ylide and the employed base. The products could be obtained in good yields under operationally simple conditions.
January 23, 2018: European Journal of Organic Chemistry
Francesco Mecozzi, Jia Jia Dong, Pattama Saisaha, Wesley R Browne
α-Hydroxy ketones are valuable synthons in organic chemistry. Here we show that oxidation of vic -diols to α-hydroxy ketones with H2 O2 can be achieved with an in situ prepared catalyst based on manganese salts and pyridine-2-carboxylic acid. Furthermore the same catalyst is effective in alkene epoxidation, and it is shown that alkene oxidation with the MnII catalyst and H2 O2 followed by Lewis acid ring opening of the epoxide and subsequent oxidation of the alkene to α-hydroxy ketones can be achieved under mild (ambient) conditions...
December 15, 2017: European Journal of Organic Chemistry
Robert D Armstrong, Benson M Kariuki, David W Knight, Graham J Hutchings
Glucaric acid has potential applications in food, pharmaceutical and polymer industries yet no methodology exists within the public domain for isolation of this key bio-derived platform molecule as a pure, crystalline solid. Here we demonstrate the difficulties, which arise in doing so and report development of a process for derivation of free-glucaric acid from its Ca2+ /K+ glucarate salts, which are both commercially available. Employing Amberlyst-15 (H+ ) exchange resin and azeotrope drying, powdered glucaric acid is prepared at > 99...
December 8, 2017: European Journal of Organic Chemistry
Gregory R Naumiec, Lisheng Cai, Shuiyu Lu, Victor W Pike
Positron emission tomography (PET) is an important molecular imaging technique for medical diagnosis, biomedical research and drug development. PET tracers for molecular imaging contain β+ -emitting radionuclides, such as carbon-11 ( t 1/2 = 20.4 min) or fluorine-18 ( t 1/2 = 109.8 min). The [18 F]2-fluoro-pyridyl moiety features in a few prominent PET radiotracers, not least because this moiety is usually resistant to unwanted radiodefluorination in vivo. Various methods have been developed for labeling these radiotracers from cyclotron-produced no-carrier-added [18 F]fluoride ion, mainly based on substitution of a leaving group, such as halide (Cl or Br), or preferably a better leaving group, such as nitro or trimethylammonium...
December 8, 2017: European Journal of Organic Chemistry
Ihsan Erden, Christian Gärtner, Jingxiang Ma, Gabriel Cabrera, Kate Markham, Saeed Azimi, Scott Gronert
Aldonitrones derived from spiro[2.4]hepta-4,6-diene-1-carbaldehyde and its benzo analog undergo a tandem uncatalyzed intramolecular cyclopropane-nitrone cyclization-5,6-dihydro-1,2-oxazine cycloreversion to give cyclopentadienones. Similarly, the NH-nitrone generated in situ from spiro[cyclopropane-1,1'-indene]carbaldehyde oxime leads to benzocyclopentadienone (1 H -inden-1-one) by the same mechanism. DFT calculations are in favor of a concerted yet highly asynchronous pathway for the cyclizations. Control experiments with the dihydro and tetrahydro derivatives show that the spirocyclopentadiene unit is essential for the success of the reaction, invoking spiroconjugative effects for increased cyclopropane reactivity...
September 15, 2017: European Journal of Organic Chemistry
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