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Beilstein Journal of Organic Chemistry

Thaís A Rossa, Nícolas S Suveges, Marcus M Sá, David Cantillo, C Oliver Kappe
An efficient three-step protocol was developed to produce 2-(azidomethyl)oxazoles from vinyl azides in a continuous-flow process. The general synthetic strategy involves a thermolysis of vinyl azides to generate azirines, which react with bromoacetyl bromide to provide 2-(bromomethyl)oxazoles. The latter compounds are versatile building blocks for nucleophilic displacement reactions as demonstrated by their subsequent treatment with NaN3 in aqueous medium to give azido oxazoles in good selectivity. Process integration enabled the synthesis of this useful moiety in short overall residence times (7 to 9 min) and in good overall yields...
2018: Beilstein Journal of Organic Chemistry
Mi-Hai Luo, Yang-Ye Jiang, Kun Xu, Yong-Guo Liu, Bao-Guo Sun, Cheng-Chu Zeng
An efficient electrocatalytic functionalization of N -arylglycine esters is reported. The protocol proceeds in an undivided cell under constant current conditions employing the simple, cheap and readily available n -Bu4 NI as the mediator. In addition, it is demonstrated that the mediated process is superior to the direct electrochemical functionalization.
2018: Beilstein Journal of Organic Chemistry
Vajinder Kumar, W Bruce Turnbull
Cholera is a diarrheal disease caused by a protein toxin released by Vibrio cholera in the host's intestine. The toxin enters intestinal epithelial cells after binding to specific carbohydrates on the cell surface. Over recent years, considerable effort has been invested in developing inhibitors of toxin adhesion that mimic the carbohydrate ligand, with particular emphasis on exploiting the multivalency of the toxin to enhance activity. In this review we introduce the structural features of the toxin that have guided the design of diverse inhibitors and summarise recent developments in the field...
2018: Beilstein Journal of Organic Chemistry
Fabio Tonin, Isabel W C E Arends
Ursodeoxycholic acid (UDCA) is a pharmaceutical ingredient widely used in clinics. As bile acid it solubilizes cholesterol gallstones and improves the liver function in case of cholestatic diseases. UDCA can be obtained from cholic acid (CA), which is the most abundant and least expensive bile acid available. The now available chemical routes for the obtainment of UDCA yield about 30% of final product. For these syntheses several protection and deprotection steps requiring toxic and dangerous reagents have to be performed, leading to the production of a series of waste products...
2018: Beilstein Journal of Organic Chemistry
Françoise Debart, Christelle Dupouy, Jean-Jacques Vasseur
Oligonucleotides (ONs) have been envisaged for therapeutic applications for more than thirty years. However, their broad use requires overcoming several hurdles such as instability in biological fluids, low cell penetration, limited tissue distribution, and off-target effects. With this aim, many chemical modifications have been introduced into ONs definitively as a means of modifying and better improving their properties as gene silencing agents and some of them have been successful. Moreover, in the search for an alternative way to make efficient ON-based drugs, the general concept of prodrugs was applied to the oligonucleotide field...
2018: Beilstein Journal of Organic Chemistry
Zi Liu, Hui Xu, Guan-Wu Wang
A solvent-free palladium-catalyzed ortho -iodination of acetanilides using N -iodosuccinimide as the iodine source has been developed under ball-milling conditions. This present method avoids the use of hazardous organic solvents, high reaction temperature, and long reaction time and provides a highly efficient methodology to realize the regioselective functionalization of acetanilides in yields up to 94% in a ball mill. Furthermore, the current methodology can be extended to the synthesis of ortho -brominated and ortho -chlorinated products in good yields by using the corresponding N -halosuccinimides...
2018: Beilstein Journal of Organic Chemistry
Antony J Fairbanks
N -Glycan oxazolines have found widespread use as activated donor substrates for endo-β- N -acetylglucosaminidase (ENGase) enzymes, an important application that has correspondingly stimulated interest in their production, both by total synthesis and by semi-synthesis using oligosaccharides isolated from natural sources. Amongst the many synthetic approaches reported, the majority rely on the fabrication (either by total synthesis, or semi-synthesis from locust bean gum) of a key Manβ(1-4)GlcNAc disaccharide, which can then be elaborated at the 3- and 6-positions of the mannose unit using standard glycosylation chemistry...
2018: Beilstein Journal of Organic Chemistry
Lizeth Bodero, Paula López Rivas, Barbara Korsak, Torsten Hechler, Andreas Pahl, Christoph Müller, Daniela Arosio, Luca Pignataro, Cesare Gennari, Umberto Piarulli
RGD-α-amanitin and isoDGR-α-amanitin conjugates were synthesized by joining integrin ligands to α-amanitin via various linkers and spacers. The conjugates were evaluated for their ability to inhibit biotinylated vitronectin binding to the purified αV β3 receptor, retaining good binding affinity, in the same nanomolar range as the free ligands. The antiproliferative activity of the conjugates was evaluated in three cell lines possessing different levels of αV β3 integrin expression: human glioblastoma U87 (αV β3 +), human lung carcinoma A549 (αV β3 -) and breast adenocarcinoma MDA-MB-468 (αV β3 -)...
2018: Beilstein Journal of Organic Chemistry
Ruth Suchsland, Bettina Appel, Sabine Müller
The preparation of protein libraries is a key issue in protein engineering and biotechnology. Such libraries can be prepared by a variety of methods, starting from the respective gene library. The challenge in gene library preparation is to achieve controlled total or partial randomization at any predefined number and position of codons of a given gene, in order to obtain a library with a maximum number of potentially successful candidates. This purpose is best achieved by the usage of trinucleotide synthons for codon-based gene synthesis...
2018: Beilstein Journal of Organic Chemistry
Shunsuke Kuribayashi, Tomoyuki Kurioka, Shinsuke Inagi, Ho-Jung Lu, Biing-Jiun Uang, Toshio Fuchigami
We herein report that the regioselective anodic fluorination of S -alkyl benzothioate and its derivatives in various aprotic solvents using Et3 N· n HF ( n = 3-5) and Et4 NF· n HF ( n = 3-5) as supporting electrolyte and a fluorine source successfully provided the corresponding α-fluorinated products in moderate yields. Dichloromethane containing Et4 NF·4HF was found to be the most suitable combination as electrolytic solvent and supporting salt as well as fluorine source for the anodic fluorination. The electrochemical fluorination of cyclic benzothioates such as benzothiophenone was also achieved...
2018: Beilstein Journal of Organic Chemistry
Ido Azuri, Anna Hirsch, Anthony M Reilly, Alexandre Tkatchenko, Shai Kendler, Oded Hod, Leeor Kronik
We present a computational analysis of the terahertz spectra of the monoclinic and the orthorhombic polymorphs of 2,4,6-trinitrotoluene. Very good agreement with experimental data is found when using density functional theory that includes Tkatchenko-Scheffler pair-wise dispersion interactions. Furthermore, we show that for these polymorphs the theoretical results are only weakly affected by many-body dispersion contributions. The absence of dispersion interactions, however, causes sizable shifts in vibrational frequencies and directly affects the spatial character of the vibrational modes...
2018: Beilstein Journal of Organic Chemistry
Anna-Lena Dreier, Andrej V Matsnev, Joseph S Thrasher, Günter Haufe
Aldol reactions belong to the most frequently used C-C bond forming transformations utilized particularly for the construction of complex structures. The selectivity of these reactions depends on the geometry of the intermediate enolates. Here, we have reacted octyl pentafluoro-λ6 -sulfanylacetate with substituted benzaldehydes and acetaldehyde under the conditions of the silicon-mediated Mukaiyama aldol reaction. The transformations proceeded with high diastereoselectivity. In case of benzaldehydes with electron-withdrawing substituents in the para -position, syn -α-SF5 -β-hydroxyalkanoic acid esters were produced...
2018: Beilstein Journal of Organic Chemistry
Prajwalita Das, Etsuko Tokunaga, Hidehiko Akiyama, Hiroki Doi, Norimichi Saito, Norio Shibata
Conscious of the potential bioactivity of fluorine, an investigation was conducted using various fluorine-containing diaryliodonium salts in order to study and compare their biological activity against human lymphoma U937 cells. Most of the compounds tested are well-known reagents for fluoro-functionalized arylation reactions in synthetic organic chemistry, but their biological properties are not fully understood. Herein, after initially investigating 18 fluoro-functionalized reagents, we discovered that the ortho -fluoro-functionalized diaryliodonium salt reagents showed remarkable cytotoxicity in vitro...
2018: Beilstein Journal of Organic Chemistry
Huangguan Chen, Jianwei Han, Limin Wang
With a strategy of the formation of benzynes by using diaryliodonium salts, a cycloaddition reaction of N -arylpyrroles with benzynes was reported. A wide range of bridge-ring amines with various substituents have been synthesized in moderate to excellent yields (35-96%). Furthermore, with a catalytic amount of TsOH·H2 O, these amines can be converted into the corresponding N -phenylamine derivatives easily, which are potentially useful in photosensitive dyes.
2018: Beilstein Journal of Organic Chemistry
Teppei Sasaki, Katsuhiko Moriyama, Hideo Togo
Various 4-aryl-3-bromocoumarins were smoothly obtained in moderate yields in one pot by treating 3-aryl-2-propynoic acids with diaryliodonium triflates and K2 CO3 in the presence of CuCl, followed by the reaction with tetrabutylammonium bromide (TBAB) and Na2 S2 O8 . The obtained 3-bromo-4-phenylcoumarin was transformed into 4-phenylcoumarin derivatives bearing C-H, C-S, C-N, and C-C bonds at 3-position.
2018: Beilstein Journal of Organic Chemistry
Hélène Pellissier
This review collects the most important developments in asymmetric Reformatsky-type reactions published since the beginning of 2013, including both diastereoselective methodologies based on the use of chiral substrates and enantioselective catalytic procedures.
2018: Beilstein Journal of Organic Chemistry
Imane Nekkaa, Márta Palkó, István M Mándity, Ferenc Fülöp
The syntheses of various pyrimidinones as potentially bioactive products by means of the highly controlled continuous-flow retro-Diels-Alder reaction of condensed pyrimidinone derivatives are presented. Noteworthy, the use of this approach allowed us to rapidly screen a selection of conditions and quickly confirm the viability of preparing the desired pyrimidinones in short reaction times. Yields typically higher than those published earlier using conventional batch or microwave processes were achieved.
2018: Beilstein Journal of Organic Chemistry
Lingjun Xu, Shuwen Han, Linjie Yan, Haifeng Wang, Haihui Peng, Fener Chen
A family of novel chloramphenicol base-amide organocatalysts possessing a NH functionality at C-1 position as monodentate hydrogen bond donor were developed and evaluated for enantioselective organocatalytic alcoholysis of meso -cyclic anhydrides. These structural diversified organocatalysts were found to induce high enantioselectivity in alcoholysis of anhydrides and was successfully applied to the asymmetric synthesis of ( S )-GABOB.
2018: Beilstein Journal of Organic Chemistry
Thanh-Tuân Bui, Fabrice Goubard, Malika Ibrahim-Ouali, Didier Gigmes, Frédéric Dumur
The design of highly emissive and stable blue emitters for organic light emitting diodes (OLEDs) is still a challenge, justifying the intense research activity of the scientific community in this field. Recently, a great deal of interest has been devoted to the elaboration of emitters exhibiting a thermally activated delayed fluorescence (TADF). By a specific molecular design consisting into a minimal overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) due to a spatial separation of the electron-donating and the electron-releasing parts, luminescent materials exhibiting small S1 -T1 energy splitting could be obtained, enabling to thermally upconvert the electrons from the triplet to the singlet excited states by reverse intersystem crossing (RISC)...
2018: Beilstein Journal of Organic Chemistry
Tirayut Vilaivan
Fluorogenic oligonucleotide probes that can produce a change in fluorescence signal upon binding to specific biomolecular targets, including nucleic acids as well as non-nucleic acid targets, such as proteins and small molecules, have applications in various important areas. These include diagnostics, drug development and as tools for studying biomolecular interactions in situ and in real time. The probes usually consist of a labeled oligonucleotide strand as a recognition element together with a mechanism for signal transduction that can translate the binding event into a measurable signal...
2018: Beilstein Journal of Organic Chemistry
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