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Beilstein Journal of Organic Chemistry

Lisa Pecher, Sebastian Schmidt, Ralf Tonner
The chemistry of organic adsorbates on surfaces is often discussed in terms of Pauli repulsion as limiting factor regarding the packing of molecules. Here we show that the attractive part of the van der Waals potential can be similarly decisive. For the semiconductor surface Si(001), an already covalently bonded molecule of cyclooctyne steers a second incoming molecule via dispersion interactions onto the neighbouring adsorption site. This helps in understanding the nonstatistical pattern formation for this surface-adsorbate system and hints toward an inclusion of dispersion attraction as another determining factor for surface adsorption...
2018: Beilstein Journal of Organic Chemistry
Ritabrata Datta, Subrata Ghosh
The metathesis of norbornene derivatives with alkynyl side-chain with Grubbs' ruthenium alkylidine as catalyst has been investigated with the objective of constructing condensed polycyclic structures. This investigation demonstrated that the generally observed domino reaction course involving a ring-opening metathesis of the norbornene unit and a ring-closing enyne metathesis is influenced to a great extent by the nature of the functional group and the substrate structure and may follow a different reaction course than what is usually observed...
2018: Beilstein Journal of Organic Chemistry
Zsanett Benke, Melinda Nonn, Márton Kardos, Santos Fustero, Loránd Kiss
Ring-opening metathesis (ROM) of various unsaturated, constrained bicyclic ring systems has been investigated with the use of commercial ruthenium-based catalysts. Starting from various cyclodienes, the corresponding derived bicyclic lactone, lactam, and isoxazoline derivatives were submitted to ROM under ethenolysis. These functionalized, strained bicyclic systems afforded novel highly-functionalized diolefinated heterocyclic scaffolds in ROM reactions with stereocontrol, through the conservation of the configuration of the stereogenic centers of the starting compounds...
2018: Beilstein Journal of Organic Chemistry
Robby Vroemans, Yenthel Verhaegen, My Tran Thi Dieu, Wim Dehaen
A new metal-free one-pot three-component procedure towards fully substituted triazolochromenes has been developed, starting from commercially available materials. Salicylaldehydes and nitroalkenes were reacted under solvent-free conditions, followed by a 1,3-dipolar cycloaddition of the intermediate 3-nitro-2 H -chromenes with organic azides in a one-pot two-step sequence. The triazolochromenes were formed with complete regioselectivity and new biologically relevant structures were synthesized via extension of the developed procedure and via postfunctionalization...
2018: Beilstein Journal of Organic Chemistry
Stephen M Geddis, Teodora Coroama, Suzanne Forrest, James T Hodgkinson, Martin Welch, David R Spring
A series of analogues of Pseudonocardia sp. natural products were synthesized, which have been reported to possess potent antibacterial activity against Helicobacter pylori and induce growth defects in Escherichia coli and Staphylococcus aureus . Taking inspiration from a methodology used in our total synthesis of natural products, we applied this methodology to access analogues possessing bulky N-substituents, traditionally considered to be challenging scaffolds. Screening of the library provided valuable insights into the structure-activity relationship of the bacterial growth defects, and suggested that selectivity between bacterial species should be attainable...
2018: Beilstein Journal of Organic Chemistry
Sagnik Sengupta, Mena Asha Krishnan, Premansh Dudhe, Ramesh B Reddy, Bishnubasu Giri, Sudeshna Chattopadhyay, Venkatesh Chelvam
In this article, we have successfully designed and demonstrated a novel continuous process for assembling targeting ligands, peptidic spacers, fluorescent tags and a chelating core for the attachment of cytotoxic molecules, radiotracers, nanomaterials in a standard Fmoc solid-phase peptide synthesis in high yield and purity. The differentially protected Fmoc-Lys-(Tfa)-OH plays a vital role in attaching fluorescent tags while growing the peptide chain in an uninterrupted manner. The methodology is versatile for solid-phase resins that are sensitive to mild and strong acidic conditions when acid-sensitive side chain amino protecting groups such as Trt (chlorotrityl), Mtt (4-methyltrityl), Mmt (4-methoxytrityl) are employed to synthesise the ligand targeted fluorescent tagged bioconjugates...
2018: Beilstein Journal of Organic Chemistry
Matthew J Styles, Helen E Blackwell
Quorum sensing (QS) allows many common bacterial pathogens to coordinate group behaviors such as virulence factor production, host colonization, and biofilm formation at high population densities. This cell-cell signaling process is regulated by N - acyl L-homoserine lactone (AHL) signals, or autoinducers, and LuxR-type receptors in Gram - negative bacteria. SdiA is an orphan LuxR-type receptor found in Escherichia, Salmonella, Klebsiella, and Enterobacter genera that responds to AHL signals produced by other species and regulates genes involved in several aspects of host colonization...
2018: Beilstein Journal of Organic Chemistry
Abed Tarapdar, James K S Norris, Oliver Sampson, Galina Mukamolova, James T Hodgkinson
Siderophore-antibiotic conjugates consist of an antibiotic covalently linked by a tether to a siderophore. Such conjugates can demonstrate enhanced uptake and internalisation to the bacterial cell resulting in significantly reduced MIC values and extended spectrum of activity. Phenothiazines are a class of small molecules that have been identified as a potential treatment for multidrug resistant tuberculosis and latent TB. Herein we report the design and synthesis of the first phenothiazine-siderophore conjugate...
2018: Beilstein Journal of Organic Chemistry
Christian Schütz, Martin Empting
The Gram-negative opportunistic pathogen Pseudomonas aeruginosa causes severe nosocomial infections. It uses quorum sensing (QS) to regulate and coordinate population-wide group behaviours in the infection process like concerted secretion of virulence factors. One very important signalling network is the Pseudomonas quinolone signal (PQS) QS. With the aim to devise novel and innovative anti-infectives, inhibitors have been designed to address the various potential drug targets present within pqs QS. These range from enzymes within the biosynthesis cascade of the signal molecules PqsABCDE to the receptor of these autoinducers PqsR (MvfR)...
2018: Beilstein Journal of Organic Chemistry
Lidia A Smyshliaeva, Mikhail V Varaksin, Pavel A Slepukhin, Oleg N Chupakhin, Valery N Charushin
The direct C-H functionalization methodology has first been applied to perform transition metal-free C-H/C-Li cross-couplings of 2 H -imidazole 1-oxides with carboranyllithium. This atom- and step-economical approach, based on one-pot reactions of nucleophilic substitution of hydrogen (SN H ) in non-aromatic azaheterocycles, affords novel imidazolyl-modified carboranes of two types ( N -oxides and their deoxygenative analogues), which are particularly of interest in the design of advanced materials.
2018: Beilstein Journal of Organic Chemistry
Matthew B Calvert, Varsha R Jumde, Alexander Titz
The rapid development of antimicrobial resistance is threatening mankind to such an extent that the World Health Organization expects more deaths from infections than from cancer in 2050 if current trends continue. To avoid this scenario, new classes of anti-infectives must urgently be developed. Antibiotics with new modes of action are needed, but other concepts are also currently being pursued. Targeting bacterial virulence as a means of blocking pathogenicity is a promising new strategy for disarming pathogens...
2018: Beilstein Journal of Organic Chemistry
Pavel Yanev, Plamen Angelov
Ethylenediamine-derived β-enamino amides are used as equivalents of amide enolate synthons in C -acylation reactions with N -protected amino acids. Domino fragmentation of the obtained intermediates leads to functionalised β-keto amides, bearing a protected amino group in their side chain.
2018: Beilstein Journal of Organic Chemistry
Gisela V Saborit, Carlos Cativiela, Ana I Jiménez, Josep Bonjoch, Ben Bradshaw
A straightforward synthetic entry to functionalized hydrindane compounds based on a rapid assembly of the core nucleus by a Danheiser cycloaddition is reported. Valuable bicyclic building blocks containing the fused five and six-membered carbocyclic ring system can be achieved in only four steps from a simple acyclic β-keto ester.
2018: Beilstein Journal of Organic Chemistry
Gergő Mótyán, László Mérai, Márton Attila Kiss, Zsuzsanna Schelz, Izabella Sinka, István Zupkó, Éva Frank
Multistep syntheses of novel 17β-pyrazol-5'-ones in the Δ5 -androstane series were efficiently carried out from pregnenolone acetate. A steroidal 17-carboxylic acid was first synthesized as a norpregnene precursor by the bromoform reaction and subsequent acetylation. Its CDI-activated acylimidazole derivative was then converted to a β-ketoester containing a two carbon atom-elongated side chain than that of the starting material. A Knorr cyclization of the bifunctional 1,3-dicarbonyl compound with hydrazine and its monosubstituted derivatives in AcOH under microwave heating conditions led to the regioselective formation of 17- exo -heterocycles in good to excellent yields...
2018: Beilstein Journal of Organic Chemistry
Carmen Curutiu, Florin Iordache, Veronica Lazar, Aurelia Magdalena Pisoschi, Aneta Pop, Mariana Carmen Chifiriuc, Alina Maria Hoban
Pseudomonas aeruginosa relies on the quorum sensing (QS) signaling system as a central regulator mechanism of virulence expression that contributes to the formation and maintenance of biofilms and tolerance to conventional antimicrobials. QS Signaling molecules (QSSMs) may be recognized and may function also within the host cells, being potentially involved in the progression of the infectious process. In this study we evaluate the expression of adhesion and inflammatory molecules in endothelial cells treated with P...
2018: Beilstein Journal of Organic Chemistry
Xiaochen Du, Jianjun Huang, Anton A Nechaev, Ruwei Yao, Jing Gong, Erik V Van der Eycken, Olga P Pereshivko, Vsevolod A Peshkov
A series of propargylamides containing an electron-rich benzene ring was prepared through the Ugi reaction of 3,5-dimethoxyaniline with various propiolic acids, aldehydes and isocyanides. Subjecting these adducts to a gold-catalyzed intramolecular alkyne hydroarylation process allowed to efficiently construct the 2-quinolone core bearing a branched substituent on the nitrogen atom.
2018: Beilstein Journal of Organic Chemistry
Daniel Blanco-Ania, Floris P J T Rutjes
The nomenclature of cations R1 C(=O+ R3 )R2 (R1 , R2 , R3 = H or organyl) has been examined and shown to be in a state of immeasurable confusion: a pragmatic recommendation is made that the generic term "carbonylonium ions" should be adopted for these intermediates, which comprises the terms "aldehydium" (R1 = H, R2 , R3 = H or organyl) and "ketonium ions" (R1 , R2 = organyl, R3 = H or organyl) for the corresponding aldehyde- and ketone-based intermediates, respectively.
2018: Beilstein Journal of Organic Chemistry
Keishiro Tahara, Ling Pan, Toshikazu Ono, Yoshio Hisaeda
Cobalamins (B12 ) play various important roles in vivo. Most B12 -dependent enzymes are divided into three main subfamilies: adenosylcobalamin-dependent isomerases, methylcobalamin-dependent methyltransferases, and dehalogenases. Mimicking these B12 enzyme functions under non-enzymatic conditions offers good understanding of their elaborate reaction mechanisms. Furthermore, bio-inspiration offers a new approach to catalytic design for green and eco-friendly molecular transformations. As part of a study based on vitamin B12 derivatives including heptamethyl cobyrinate perchlorate, we describe biomimetic and bioinspired catalytic reactions with B12 enzyme functions...
2018: Beilstein Journal of Organic Chemistry
Nisachon Khunnawutmanotham, Cherdchai Laongthipparos, Patchreenart Saparpakorn, Nitirat Chimnoi, Supanna Techasakul
A series of 3-amino-6,7-dimethoxycoumarins conjugated with the N -benzylpyridinium moiety through an amide-bond linkage was synthesized and evaluated for their acetylcholinesterase inhibitory activity. A number of the benzylpyridinium derivatives exhibited potent activities with inhibitory concentration (IC50 ) values in the nanomolar concentration range. Among them, the 2,3-difluorobenzylpyridinium-containing compound was the most potent inhibitor with an IC50 value of 1.53 ± 0.01 nM. Docking studies revealed that the synthesized compounds inhibit the target enzyme by a dual binding site mechanism whereby the coumarin portion binds with the peripheral anionic site while the N -benzylpyridinium residue binds with the catalytic anionic site of the enzyme...
2018: Beilstein Journal of Organic Chemistry
Sambasivarao Kotha, Saidulu Todeti, Vikas R Aswar
We have developed an efficient synthetic strategy to assemble C 3 -symmetric molecules containing propellane moieties as end groups and a benzene ring as a central core. The synthesis of these C 3 -symmetric molecules involves simple starting materials. Our approach to C 3 -symmetric compounds relies on a Diels-Alder reaction, cyclotrimerization and ring-closing metathesis as key steps.
2018: Beilstein Journal of Organic Chemistry
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