Reaction of oxiranes with cyclodextrins under high-energy ball-milling conditions

• László Jicsinszky,
• Federica Calsolaro,
• Katia Martina,
• Fabio Bucciol,
• Maela Manzoli and
• Giancarlo Cravotto

Beilstein J. Org. Chem. 2019, 15, 1448–1459, doi:10.3762/bjoc.15.145

• experiments; a very hazy solution was obtained, which was inseparable by centrifugation, after dialysis. Filtration through a 0.22 µm hydrophilic membrane showed poor resistance, meaning that particle sizes were low and dominantly <0.2 µm. Experiments to clarify the situation and determine the composition of

Stereo- and regioselective hydroboration of 1-exo-methylene pyranoses: discovery of aryltriazolylmethyl C-galactopyranosides as selective galectin-1 inhibitors

• Alexander Dahlqvist,
• Axel Furevi,
• Niklas Warlin,
• Hakon Leffler and
• Ulf J. Nilsson

Beilstein J. Org. Chem. 2019, 15, 1046–1060, doi:10.3762/bjoc.15.102

• -linked glycans on the cell surface. Surface proteins such as integrins [6][7], vascular endothelial growth factor receptor [8], and lysosome-associated membrane proteins [9] are known to be crosslinked by galectins, giving galectins a modulating role in cell adhesion, blood vessel growth and cellular

Fabrication, characterization and adsorption properties of cucurbit[7]uril-functionalized polycaprolactone electrospun nanofibrous membranes

• Changzhong Chen,
• Fengbo Liu,
• Xiongzhi Zhang,
• Zhiyong Zhao and
• Simin Liu

Beilstein J. Org. Chem. 2019, 15, 992–999, doi:10.3762/bjoc.15.97

• . Compared to the neat PCL nanofibrous membrane, all the PCL/CB[7] nanofibrous membranes exhibit increased adsorption capability for MB, indicating that the incorporation of CB[7] plays a positive role in the promotion of adsorption capability. Meanwhile, there is an obvious tendency that the equilibrium

• at 293 K was investigated, and PCL/CB[7] (100:100) nanofibrous membrane was selected as the typical research object here. There are two well-known adsorption isotherm models to examine the equilibrium isotherm of adsorbates by adsorbents: the Langmuir isotherm model and Freundlich isotherm model (the

• place at specific homogeneous sites within the nanofibrous membrane and formed a monolayer coverage of MB at the surface of the nanofibrous membrane [34]. The morphology of PCL and PCL/CB[7] nanofibers after the absorption experiment are shown in Figure S9 (Supporting Information File 1). It is found

Heck- and Suzuki-coupling approaches to novel hydroquinone inhibitors of calcium ATPase

• Robert J. Kempton,
• Taylor A. Kidd-Kautz,
• Soizic Laurenceau and
• Stefan Paula

Beilstein J. Org. Chem. 2019, 15, 971–975, doi:10.3762/bjoc.15.94

• convey specificity for prostate cancer cells. Keywords: calcium ATPase inhibitors; Heck- and Suzuki-coupling reactions; hydroquinones; prostate cancer; tethered amino acid; Introduction Sarco/endoplasmic reticulum calcium ATPase (SERCA) is an integral protein that resides in the membrane of the

Towards the preparation of synthetic outer membrane vesicle models with micromolar affinity to wheat germ agglutinin using a dialkyl thioglycoside

• Dimitri Fayolle,
• Nathalie Berthet,
• Bastien Doumeche,
• Olivier Renaudet,
• Peter Strazewski and
• Michele Fiore

Beilstein J. Org. Chem. 2019, 15, 937–946, doi:10.3762/bjoc.15.90

• vesicles, alone or in mixture with phospholipids, mimicking bacterial outer membrane vesicles (OMV) with potential antiadhesive properties. Keywords: glycolipids; outer membrane vesicles; synthetic vaccines; Introduction Outer membrane vesicles (OMV) [1], lipid bilayer vesicles released from the outer

• membrane of Gram-negative bacteria, are considered today as attractive candidates for vaccine delivery. However, they have some disadvantages, they are not easy to produce and are difficult to characterize [2][3]. Moreover, toxic lipopolysaccharides (LPS) present in the outer membrane of most of Gram

• ). Moreover, a thin layer of compounds 5 or 8 without POPC, hydrated in the same conditions, gave similar giant vesicles (Figure 3, images f,g and i). Microscopic observation suggested that those supramolecular assemblies microscopically resemble the well-known outer membrane vesicles (OMV) [1]. The tentative

Synthesis of acylglycerol derivatives by mechanochemistry

• Karen J. Ardila-Fierro,
• Andrij Pich,
• Marc Spehr,
• José G. Hernández and
• Carsten Bolm

Beilstein J. Org. Chem. 2019, 15, 811–817, doi:10.3762/bjoc.15.78

• in the catalytic action of various membrane-related enzymes, such as protein kinase C (PKC) isoforms [45]. Therefore, the development of strategies for visualization of acylglycerols in cellular environments by their fusion with fluorescent molecular labels is in high demand [46]. As a result, once

Cyclopropene derivatives of aminosugars for metabolic glycoengineering

• Jessica Hassenrück and
• Valentin Wittmann

Beilstein J. Org. Chem. 2019, 15, 584–601, doi:10.3762/bjoc.15.54

• , are not comparable. Additionally, the influence of the sugar derivative on the reaction rate has not been taken into account. Ac4ManNCyoc as well as Ac4ManNCp were shown to give after MGE a better membrane staining than Ac4ManNCyc [25][27]. A direct comparison of Ac4ManNCyoc and Ac4ManNCp in one

• of the deacetylated (water-soluble) sugars, the performance of the sugars in MGE, and the assessment of their metabolic acceptance. The studies uncovered that Ac4ManNCp is much better accepted than Ac4ManNCyoc although their membrane staining intensity after MGE is comparable. The high metabolic

• acceptance of the Cp-modified sugar inspired us to develop novel derivatives of glucosamine and galactosamine containing this cyclopropene modification and to explore their behavior in MGE both for membrane-bound and intracellular glycoproteins. Results and Discussion Kinetic studies The second-order rate

Synthesis of the polyketide section of seragamide A and related cyclodepsipeptides via Negishi cross coupling

• Jan Hendrik Lang and
• Thomas Lindel

Beilstein J. Org. Chem. 2019, 15, 577–583, doi:10.3762/bjoc.15.53

• cytotoxicity [3]. A photoreactive derivative of the cytotoxic jasplakinolides, geodiamolides [4][5], or seragamides (2–6, seragamides A–E) [6] could also enable the search for additional targets in the cell, including proteins involved in transport or even membrane components. For this purpose, the 2

Synthesis and SAR of the antistaphylococcal natural product nematophin from Xenorhabdus nematophila

• Frank Wesche,
• Hélène Adihou,
• Thomas A. Wichelhaus and
• Helge B. Bode

Beilstein J. Org. Chem. 2019, 15, 535–541, doi:10.3762/bjoc.15.47

• hydrophobicity influences the passive membrane diffusion and therefore might influence how the compounds get to their actual target [30]. Moreover, a specific minimal size of the cyclic moiety must be fulfilled as, e.g., 2 with a phenyl moiety is less active in vitro. Conclusion Despite their lower bioactivities

Synthesis and fluorescent properties of N(9)-alkylated 2-amino-6-triazolylpurines and 7-deazapurines

• Andrejs Šišuļins,
• Jonas Bucevičius,
• Yu-Ting Tseng,
• Irina Novosjolova,
• Kaspars Traskovskis,
• Ērika Bizdēna,
• Huan-Tsung Chang,
• Sigitas Tumkevičius and
• Māris Turks

Beilstein J. Org. Chem. 2019, 15, 474–489, doi:10.3762/bjoc.15.41

• several reasons: a) they help to solubilize the target compounds in the organic medium; b) they are considered as a good compromise to achieve both “membrane-like character”, which helps for cell membrane permeability, and sufficient solubility in the aqueous (biological) media [49]. With the key

• File 1). Bearing in mind fluorescent properties and low cytotoxicity of the newly obtained compounds, we tested their potential application in cell staining. The preliminary experiments revealed that the compounds went through the cell membrane after 1 h or 2 h incubation period and localized uniformly

• were replaced with 500 μL of cell culture medium containing the compound, and then further cultured for an additional 1 h. Those cells were washed twice with 1× PBS and fixed to the membrane using 4% paraformaldehyde in 5.0 mM sodium phosphate buffer (pH 7.4; 1.0 mL) for 10 min. The fluorescence images

Aqueous olefin metathesis: recent developments and applications

• Valerio Sabatino and
• Thomas R. Ward

Beilstein J. Org. Chem. 2019, 15, 445–468, doi:10.3762/bjoc.15.39

• leader sequence to the N-terminus of streptavidin (Sav) allowed the secretion and assembly of functional tetrameric Sav in the periplasm of E. coli. The passive diffusion of the biotinylated Hoveyda–Grubbs catalyst 60 through the outer membrane of E. coli containing Sav in its periplasm then affords the

Catalysis of linear alkene metathesis by Grubbs-type ruthenium alkylidene complexes containing hemilabile α,α-diphenyl-(monosubstituted-pyridin-2-yl)methanolato ligands

• Tegene T. Tole,
• Johan H. L. Jordaan and
• Hermanus C. M. Vosloo

Beilstein J. Org. Chem. 2019, 15, 194–209, doi:10.3762/bjoc.15.19

• with GxF/0.45 µm GHP membrane (PALL) was used to filter the lithium salt from the precatalyst. Experimental procedures Precatalyst synthesis: The well-established methods of Herrmann et al. [23] and Van Der Schaaf et al. [7] were used to synthesize precatalysts 6–9. This is illustrated in Scheme 2

Synthesis of a tubugi-1-toxin conjugate by a modulizable disulfide linker system with a neuropeptide Y analogue showing selectivity for hY1R-overexpressing tumor cells

• Rainer Kufka,
• Robert Rennert,
• Goran N. Kaluđerović,
• Lutz Weber,
• Wolfgang Richter and
• Ludger A. Wessjohann

Beilstein J. Org. Chem. 2019, 15, 96–105, doi:10.3762/bjoc.15.11

• tumor-targeting therapeutics [7][8]. Such targeted therapeutics are able to address transformed cells selectively by recognition of disease-associated membrane structures, e.g., dysregulated membrane proteins, or by modulation of metabolic or regulatory characteristics that are specific or at least

• cells’ membrane by unspecific, receptor-independent pathways, not discriminating between normal and transformed cells. For that reason it is very difficult to adjust a practicable therapeutic window for these toxins. All the more, it is important to mask the high toxicity of tubulysin A and tubugi-1

• towards tubugi-1-SH and the entire conjugate tubugi-1–SS–NPY. When compared with HT-29 and PC-3 cells, the IC50 value of tubugi-1-SH is by factor 10 higher in Colo320. Since the membrane passage of tubugi-1-SH is not depending on a NPY receptor, there have to be other explanations for the reduced

Lectins of Mycobacterium tuberculosis – rarely studied proteins

• Katharina Kolbe,
• Sri Kumar Veleti,
• Norbert Reiling and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2019, 15, 1–15, doi:10.3762/bjoc.15.1

• modifications of glycocalyx proteins are N-glycans (asparagine-linked) and O-glycans (serine- or threonine-linked), while glycosphingolipids are the major subclass of glycosylated lipids in the cell membrane of human cells (Figure 2). While many core elements of glycocalyx oligosaccharides are conserved between

• membrane is surrounded by a peptidoglycan layer (PG) consisting of multiple, parallel glycan chains of alternating (1→4)-linked subunits of N-acetyl-β-D-glucosamine and N-acetyl- or N-glycolyl-β-D-muramic acid, crosslinked via short conserved oligopeptide stems [44][45]. The PG is covalently attached to

• calcium-dependent manner. The ligand specificity is highly diverse, including fucosides, mannosides, glucosides, N-acetylglucosamines, galactosides, and N-acetylgalactosamines. While some of the C-type lectins are known to be secreted, others are membrane-associated proteins. They often oligomerize into

Thermophilic phosphoribosyltransferases Thermus thermophilus HB27 in nucleotide synthesis

• Ilja V. Fateev,
• Ekaterina V. Sinitsina,
• Aiguzel U. Bikanasova,
• Maria A. Kostromina,
• Elena S. Tuzova,
• Larisa V. Esipova,
• Tatiana I. Muravyova,
• Alexei L. Kayushin,
• Irina D. Konstantinova and
• Roman S. Esipov

Beilstein J. Org. Chem. 2018, 14, 3098–3105, doi:10.3762/bjoc.14.289

• 8.0 (4 CV, flow rate 2 mL/min). Pooled fractions were concentrated by a polysulfonic membrane PBGC 10 kDa (Millipore, USA). The resulting solution was applied to a column with HiLoad 16/60 Superdex 75pg (GE Healthcare, USA), equilibrated by 20 mM Tris-HCl, 50 mM NaCl, 0.04% NaN3, and 10% glycerol, pH

• , contained the target enzyme, were pooled and concentrated on polysulphonic membrane PBGC 10 kDa. The resulting solution was applied to column with HiLoad 16/60 Superdex 200, equilibrated by 20 mM Tris-HCl, 50 mM NaCl, 0.04% NaN3, and 5% glycerol, pH 8.0. Fractions, contained the target enzyme with purity

6’-Fluoro[4.3.0]bicyclo nucleic acid: synthesis, biophysical properties and molecular dynamics simulations

• Sibylle Frei,
• Andrei Istrate and
• Christian J. Leumann

Beilstein J. Org. Chem. 2018, 14, 3088–3097, doi:10.3762/bjoc.14.288

• polarizability of the modified nucleotide, and therefore influences the metabolic stability, the membrane permeability, the RNA- and protein-binding affinity of the AON [25][26][27][28][29]. Over the last almost two decades, fluorinated oligonucleotide analogs like 2’-deoxy-2’-fluoro-RNA (F-RNA) [26][30][31], 2

Protein–protein interactions in bacteria: a promising and challenging avenue towards the discovery of new antibiotics

• Laura Carro

Beilstein J. Org. Chem. 2018, 14, 2881–2896, doi:10.3762/bjoc.14.267

• also determined the growth suppressive effects on model Gram-positive (B. subtilis) and Gram-negative (E. coli imp4213) bacteria. The MIC values against B. subtilis were found to be 40, 11, 16 μM for CFAM, BCBP and MPTA, respectively, while the MIC values against the membrane-compromised E. coli were

• microorganisms which included Gram-positive pathogens Staphylococcus aureus, Streptococcus pneumoniae, Bacillus subtilis, Enterococcus faecalis and the Gram-negative bacterium Escherichia coli (wt and an outer membrane permeable strain). Gratifyingly, the antibacterial screening showed that improved IC50 values

• correlated with improved minimal inhibitory concentrations and that Gram-positive microorganisms are more susceptible, likely due to the inability of molecules to permeate the outer membrane of Gram-negative pathogens [88]. In a follow-up study, a combinatorial synthesis approach was utilized to generate a

Olefin metathesis catalysts embedded in β-barrel proteins: creating artificial metalloproteins for olefin metathesis

• Daniel F. Sauer,
• Johannes Schiffels,
• Takashi Hayashi,
• Ulrich Schwaneberg and
• Jun Okuda

Beilstein J. Org. Chem. 2018, 14, 2861–2871, doi:10.3762/bjoc.14.265

• ]. Characterized by an amphiphilic nature with either hydrophobic “barrel” interiors and hydrophilic surfaces (as in globulins, carriers of hydrophobic molecules and fluorescent proteins) or hydrophilic cores and hydrophobic surfaces (as in membrane-bound β-barrels like porins and channel proteins), they can be

• NO transport, storage and sensing as well as heme metabolism [36]) usually constitute eight to ten antiparallel β-strands and tightly packed hydrophobic or hydrophilic barrel interiors [37]. Membrane-bound β-barrels are confined to mitochondrial and chloroplast membranes and the outer membranes of

• Gram-negative bacteria [38]. They constitute up to 24 strands, require sophisticated assembly machineries for membrane integration [39] and are usually “plugged” by hydrophilic loops and helices that either ensure the binding of small molecules, or their (energy-dependent) transport across the outer

Pd-Catalyzed microwave-assisted synthesis of phosphonated 13α-estrones as potential OATP2B1, 17β-HSD1 and/or STS inhibitors

• Rebeka Jójárt,
• Szabolcs Pécsy,
• György Keglevich,
• Mihály Szécsi,
• Réka Rigó,
• Csilla Özvegy-Laczka,
• Gábor Kecskeméti and
• Erzsébet Mernyák

Beilstein J. Org. Chem. 2018, 14, 2838–2845, doi:10.3762/bjoc.14.262

• and Economics, H-1521 Budapest, Hungary 1st Department of Medicine, University of Szeged, Korányi fasor 8–10, H-6720 Szeged, Hungary Membrane protein research group, Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, H-1117 Budapest

• phenolic hydroxy function. On the other hand, estrone sulfate is not able to cross the cell membrane passively; therefore, a carrier is needed to mediate its transport across the lipid bilayer. These carriers are certain representatives of the solute carrier superfamily (SLC), including members of the

• estrone derivatives, including estrone-3-sulfate could be blocked. Inhibitors based on the estrane core could have multiple inhibitory properties concerning the two enzymatic steps of the sulfatase pathway and OATP2B1-mediated membrane transport of estrone-sulfate. The inhibitor design is usually based on

Novel solid-phase strategy for the synthesis of ligand-targeted fluorescent-labelled chelating peptide conjugates as a theranostic tool for cancer

• Sagnik Sengupta,
• Mena Asha Krishnan,
• Premansh Dudhe,
• Ramesh B. Reddy,
• Bishnubasu Giri,
• Sudeshna Chattopadhyay and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2018, 14, 2665–2679, doi:10.3762/bjoc.14.244

• membrane antigen (PSMA) expressed on prostate, breast, bladder and brain cancers and pteroate rhodamine B, targeting folate receptor positive cancers such as ovarian, lung, endometrium as well as inflammatory diseases have been synthesized. In vitro studies using LNCaP (PSMA +ve), PC-3 (PSMA −ve, FR −ve

• membrane antigen (PSMA) [7][8][9] and the folate receptor [10][11][12][13] are well characterized and most attractive cancer biomarkers present in primary and metastatic stages of prostate and ovarian cancers, respectively. PSMA belongs to a family of type II membrane bound glycoprotein over-expressed on

• the cell surface of prostate, brain, bladder and breast cancers. Whereas folate receptors are attached to the cell membrane by a glycophosphatidylinositol anchor and over-expressed on several cancers as well as activated macrophages during inflammation. Moreover, folate receptors were also discovered

The design and synthesis of an antibacterial phenothiazine–siderophore conjugate

• Abed Tarapdar,
• James K. S. Norris,
• Oliver Sampson,
• Galina Mukamolova and
• James T. Hodgkinson

Beilstein J. Org. Chem. 2018, 14, 2646–2650, doi:10.3762/bjoc.14.242

• antibiotics to the bacterial cell [3]. Iron is essential for bacterial survival and bacteria secrete high affinity iron chelating molecules to scavenge and solubilise Fe3+ from the extracellular environment [3]. The siderophore–Fe complex is recognised by specific receptor proteins on the outer membrane of

• the bacteria and internalised into the bacterium cell by active transport [4]. Siderophore–antibiotic conjugates consist of an antibiotic covalently linked by a ‘tether' to a siderophore. Such conjugates overcome the bacterial membrane permeability barrier and facilitate active transport of the

• achieved with beta-lactam-based siderophore conjugates targeting membrane associated penicillin binding proteins (PBPs) [7]. Cefiderocol (S-649266) is a beta-lactam–siderophore conjugate currently in phase III clinical trials which demonstrates enhanced potency against Gram-negative bacteria including

Targeting the Pseudomonas quinolone signal quorum sensing system for the discovery of novel anti-infective pathoblockers

• Christian Schütz and
• Martin Empting

Beilstein J. Org. Chem. 2018, 14, 2627–2645, doi:10.3762/bjoc.14.241

• machineries consisting of several protein components, which in total span from the inner to the outer side of the cell membrane. Their function is to expel a wide range of xenobiotics, among them antibiotics from the cephalosporin, carbapenem, fluroquinolone and aminoglycoside classes [13]. Through this

• molecule [34]. This autoinducer has been described to mediate iron acquisition, cytotoxicity, outer-membrane vesicle biogenesis, and to exert host immune modulatory effects [34][35]. Interestingly, PQS as well as HHQ are able to interfere with nuclear transcription factor-κB and hypoxia-inducible factor 1

• . aeruginosa quorum quenching assays was observed [56]. This highlights a notable issue when addressing intracellular targets of this Gram-negative bacterium, as permeating the outer and inner membrane while escaping efflux and enzymatic deactivation may represent a true challenge. The elucidation of the

Impact of Pseudomonas aeruginosa quorum sensing signaling molecules on adhesion and inflammatory markers in endothelial cells

• Carmen Curutiu,
• Florin Iordache,
• Veronica Lazar,
• Aurelia Magdalena Pisoschi,
• Aneta Pop,
• Mariana Carmen Chifiriuc and
• Alina Maria Hoban

Beilstein J. Org. Chem. 2018, 14, 2580–2588, doi:10.3762/bjoc.14.235

• , and this effect appears to be related to NFκB activation. These autoinducers (AIs) stimulate the production of membrane-associated prostaglandin E (PGE) and PGE2 but not PGE from cytosol. It is known that PGE2 plays a role in inducing mucus secretion, vasodilatation and edema, acting as a lipid

Comparative cell biological study of in vitro antitumor and antimetastatic activity on melanoma cells of GnRH-III-containing conjugates modified with short-chain fatty acids

• Eszter Lajkó,
• Sarah Spring,
• Rózsa Hegedüs,
• Beáta Biri-Kovács,
• Sven Ingebrandt,
• Gábor Mező and
• László Kőhidai

Beilstein J. Org. Chem. 2018, 14, 2495–2509, doi:10.3762/bjoc.14.226

• different enzymatic stability and cellular uptake because these conjugates were found to have similar octanol–water partition index and membrane permeability. Nevertheless, the higher hydrophobicity (lower solubility) of the conjugate with myristic acid seemed to correlate with its increased stability

• (Ac)]-GnRH-III(Dau=Aoa). Dau served as a positive control in this experiment and showed a high level of intracellular fluorescence. Considering that Dau is a small molecule and can diffuse through the plasma membrane while the conjugates can enter the cells by receptor-mediated endocytosis with low

• of conjugates requires their receptor-mediated internalization and the lysosomal degradation, while Dau could diffuse through the plasma membrane and exerts its antitumor activity by intercalating directly to DNA. Furthermore, it was previously demonstrated that the smallest Dau-containing fragment

Rational design of boron-dipyrromethene (BODIPY) reporter dyes for cucurbit[7]uril

• Mohammad A. Alnajjar,
• Jürgen Bartelmeß,
• Robert Hein,
• Pichandi Ashokkumar,
• Mohamed Nilam,
• Werner M. Nau,
• Knut Rurack and
• Andreas Hennig

Beilstein J. Org. Chem. 2018, 14, 1961–1971, doi:10.3762/bjoc.14.171

• dye are regenerated. This principle has enabled, for example, real-time monitoring of enzymatic activity [18][19][20], the detection of membrane-transport activity [21] and membrane fusion [22], and even cellular imaging appears to be a potential future prospect [23][24]. However, most combinations of

• fluorescence from biological samples, and it would have a high fluorescence quantum yield in either bound or unbound state with a large difference in fluorescence intensity between both. In addition, a tuneable hydrophobicity to render the dye–CB complex membrane permeable or not, and a tuneable affinity for