Formation of an unexpected 3,3-diphenyl-3H-indazole through a facile intramolecular [2 + 3] cycloaddition of the diazo intermediate

• Andrew T. King,
• Hugh G. Hiscocks,
• Lidia Matesic,
• Mohan Bhadbhade,
• Roger Bishop and
• Alison T. Ung

Beilstein J. Org. Chem. 2019, 15, 1347–1354, doi:10.3762/bjoc.15.134

• chemical reagents and analytical grade solvents were obtained from commercial sources such as Sigma-Aldrich, Cambridge Isotope Laboratories Inc. and Merck Millipore. All reactions were monitored using either TLC aluminium oxide 60 F254 neutral or TLC Silica gel 60 F254 with UV detection at 254 nm. 1H NMR

N-doped carbon dots covalently functionalized with pillar[5]arenes for Fe³⁺ sensing

• Jia Gao,
• Ming-Xue Wu,
• Dihua Dai,
• Zhi Cai,
• Yue Wang,
• Wenhui Fang,
• Yan Wang and
• Ying-Wei Yang

Beilstein J. Org. Chem. 2019, 15, 1262–1267, doi:10.3762/bjoc.15.123

• , symmetrical structures, superior host–guest properties, supramolecular assembly characteristics, and versatile functionalities [11][15][16]. Carboxylatopillar[5]arene (CP[5]) is one of the most popular functional pillarenes that has been exploited in many research areas, especially in sensing and detection

• ) through covalent bonds formed by EDC-NHS coupling reaction. The comparison of CCDs with single CN-dots without CP[5], revealed that the CCDs exhibit a higher selectivity for Fe3+ detection (Scheme 1). Fe3+ ions play an important role in the living organism and is related to many diseases, thus it is vital

• a good linear correlation (R2 = 0.992) and the lowest detection limit (LOD) was determined to be 1.2 μM [16][24][25]. Subsequently, the quenching mechanism of Fe3+ toward CCDs was investigated. As demonstrated in Figure 3e, the UV–vis absorption of Fe3+ overlaid with the emission peak of CCDs, thus

Understanding the unexpected effect of frequency on the kinetics of a covalent reaction under ball-milling conditions

• Ana M. Belenguer,
• Adam A. L. Michalchuk,
• Giulio I. Lampronti and
• Jeremy K. M. Sanders

Beilstein J. Org. Chem. 2019, 15, 1226–1235, doi:10.3762/bjoc.15.120

• the phase composition by Rietveld refinement is ±3 mol % of the absolute and estimated sensitivity while the limit of detection (LOD) is 3 mol %. The estimated sensitivity of the HPLC analysis resulting in the chemical composition of the samples is 0.1 mol % relative to the main component. Therefore

Ugi reaction-derived prolyl peptide catalysts grafted on the renewable polymer polyfurfuryl alcohol for applications in heterogeneous enamine catalysis

• Alexander F. de la Torre,
• Gabriel S. Scatena,
• Oscar Valdés,
• Daniel G. Rivera and
• Márcio W. Paixão

Beilstein J. Org. Chem. 2019, 15, 1210–1216, doi:10.3762/bjoc.15.118

• reactor coupled to a HPLC system and the retention times of each substrate within the reactor were measured by UV detection at a wavelength of 210 nm. A retention time of 70 min for β-nitrostyrene at a flow rate of 0.1 mL/min into the reactor was observed. Then, this preferential occupancy of the packing

• flash column chromatography (EtOAc/hexane 1:9, v/v). The spectroscopic data are in agreement with the published data [15]. The enantiomeric excess was determined by chiral-stationary phase HPLC (Chiralpak OD-H, hexane/iPrOH 99:1, v/v, 25 °C) at 1.00 mL/min, UV detection at 210 nm: tR: (syn, major

Mechanochemical synthesis of hyper-crosslinked polymers: influences on their pore structure and adsorption behaviour for organic vapors

• Sven Grätz,
• Sebastian Zink,
• Hanna Kraffczyk,
• Marcus Rose and
• Lars Borchardt

Beilstein J. Org. Chem. 2019, 15, 1154–1161, doi:10.3762/bjoc.15.112

• contents below the limit of detection (Supporting Information File 1, Figure S3). Scattering electron microscopy also revealed an agglomerated morphology of the samples (Supporting Information File 1, Figure S4). After successfully establishing the occurrence of the cross-linking reaction and investigating

Molecular recognition using tetralactam macrocycles with parallel aromatic sidewalls

• Dong-Hao Li and
• Bradley D. Smith

Beilstein J. Org. Chem. 2019, 15, 1086–1095, doi:10.3762/bjoc.15.105

• tetralactams with parallel aromatic sidewalls are well-suited for various practical supramolecular applications such as molecular machines [72], optical imaging [73], organocatalysis [55], detection [74], and separations [24]. X-ray crystal structures of various squaraine rotaxanes show that the macrocycle

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

• 100% acetonitrile. Monitoring and collection based on UV–vis absorbance at 210 nm and 254 nm, respectively. Purity analysis was performed using UPLC–MS with UV–vis detection on a Waters Acquity UPLC + Waters XEVO-G2 system using a Waters Acquity CSH C18, 1.7 µm, 2.1 × 100 mm column. Samples were run

• % acetonitrile, 3 or 6 µL injection, detection 190–300 nm. MS parameters: Cap voltage 3.0 kV, cone voltage 40 kV, Ext 4, source temperature 120 °C, desolvation temperature 500 °C, cone gas 50, desolvation gas 800, centroid resolution mode, m/z interval 50–1200, lockspray. Calibration: Leu-enkephalin m/z 556.2771

• HPLC, UV–vis detection: 98.4%. 1,2-Dideoxy-1-[4-(4-fluorophenyl)-1H-1,2,3-triazol-1-yl]-β-D-galactoheptulose (1b): Compound 10b (50 mg, 0.147 mmol) was dissolved in cyclohexene/ethanol 2:1 (3 mL), palladium(II) hydroxide on charcoal (40 mg, 20 wt %) was added, and the mixture refluxed overnight at 80

New terpenoids from the fermentation broth of the edible mushroom Cyclocybe aegerita

• Frank Surup,
• Florian Hennicke,
• Nadine Sella,
• Maria Stroot,
• Steffen Bernecker,
• Sebastian Pfütze,
• Marc Stadler and
• Martin Rühl

Beilstein J. Org. Chem. 2019, 15, 1000–1007, doi:10.3762/bjoc.15.98

• , flow rate = 0.6 mL min−1, UV detection at 200–600 nm]. Fermentation in shaking flasks A culture of the strain C. aegerita AAE-3 with a total volume of 4 L was prepared in ZM ½ medium [molasses 47% (Nord Zucker AG Schladen, Germany) 5.00 g/L, oatmeal (Herrnmühle, Harald Feick OHG, Reichelsheim, Germany

• performed in triplicates using the CFX Connect™ RT-PCR Detection System (Bio-Rad Laboratories, Hercules, CA, USA). The following conditions were applied: enzyme activation at 94 °C for 20 s followed by 40 cycles of 94 °C for 30 s, 58 °C for 30 s and 72 °C for 10 s. Structures of the isolated metabolites

Diaminoterephthalate–α-lipoic acid conjugates with fluorinated residues

• Leon Buschbeck,
• Aleksandra Markovic,
• Gunther Wittstock and
• Jens Christoffers

Beilstein J. Org. Chem. 2019, 15, 981–991, doi:10.3762/bjoc.15.96

• sequence including one deprotection reaction. One functional unit is α-lipoic acid (ALA) for binding the dye to gold surfaces. It was introduced to the DAT scaffold by an amidation reaction. The other functional unit is a para-(trifluoromethyl)benzyl group for facile detection of the surface-bound material

• indicated that trifluoromethylation is an excellent tool for the detection of surface-bound materials by XPS. Keywords: chromophore; diaminoterephthalate; fluorine surface marker; fluorescence dye; lipoic acid; self-assembled monolayers; Introduction Diaminoterephthalates (DATs) are powerful fluorescence

• with soft ionizations are not applicable; and (3) the total amount of material is extremely small (i.e., about 10−9 mol·cm−2) [39]. X-ray photoelectron spectroscopy (XPS) is one of the few suitable methods for detection of surface-immobilized compounds and changes on the surfaces. However, due to

Mechanochemical synthesis of poly(trimethylene carbonate)s: an example of rate acceleration

• Sora Park and
• Jeung Gon Kim

Beilstein J. Org. Chem. 2019, 15, 963–970, doi:10.3762/bjoc.15.93

• transform NMR spectrometer and all signals were referenced to residual protonated solvent. Gel permeation chromatography (GPC) analyses with refractive index (RI) detection were used to determine the number-averaged molecular weights (Mn), weight-averaged molecular weights (Mw), and polydispersities (Mw/Mn

Photochemical generation of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical from caged nitroxides by near-infrared two-photon irradiation and its cytocidal effect on lung cancer cells

• Ayato Yamada,
• Manabu Abe,
• Yoshinobu Nishimura,
• Shoji Ishizaka,
• Masashi Namba,
• Taku Nakashima,
• Kiyofumi Shimoji and
• Noboru Hattori

Beilstein J. Org. Chem. 2019, 15, 863–873, doi:10.3762/bjoc.15.84

• also observed (Figure 5). To evaluate whether the cytocidal effect was due to photochemical radical generation, cells exposed to 360 nm light for 1 min and the unexposed congeners were stained by using a ROS-ID oxidative stress detection kit (Enzo Life Sciences, Farmingdale, NY, U.S.A.). Reactive

• , 90, 120, and 150 s) using a fluorescence microscope (BIOREVO BZ-9000, Keyence, Osaka, Japan), cell viability was determined by trypan blue exclusion. Bars represent the mean ± standard deviation (n = 4). Detection of intracellular ROS in irradiated LLC cells with 2a-containing medium Fifty thousand

• light using a fluorescence microscope (BIOREVO BZ-9000, Keyence, Osaka, Japan), intracellular ROS were detected using the ROS-ID Oxidative Stress Detection Kit (Enzo Life Sciences, Farmingdale, NY, USA) in conjunction with fluorescence microscopy. Intracellular ROS was detected in the form of green

Efficient synthesis of 4-substituted-ortho-phthalaldehyde analogues: toward the emergence of new building blocks

• Clémence Moitessier,
• Ahmad Rifai,
• Pierre-Edouard Danjou,
• Isabelle Mallard and
• Francine Cazier-Dennin

Beilstein J. Org. Chem. 2019, 15, 721–726, doi:10.3762/bjoc.15.67

• -aminobutyric acid by high-performance liquid chromatography with molecular fluorescence detection [5]. In addition to the above manipulations, OPA and its derivatives are also valuable reagents [6] in organic chemistry, used to generate phthalimidine [7], imines [8], isoindole [9], 3-hydroxyindanone [10

Design and synthesis of multivalent α-1,2-trimannose-linked bioerodible microparticles for applications in immune response studies of Leishmania major infection

• Chelsea L. Rintelmann,
• Tara Grinnage-Pulley,
• Kathleen Ross,
• Daniel E. K. Kabotso,
• Angela Toepp,
• Anne Cowell,
• Christine Petersen,
• Balaji Narasimhan and
• Nicola Pohl

Beilstein J. Org. Chem. 2019, 15, 623–632, doi:10.3762/bjoc.15.58

• feasible targets for both parasite detection and vaccine development [3]. Leishmania, an obligate intracellular parasite with varying surface glycoconjugates, infects an estimated 12 million people worldwide and has 350 million people at risk in endemic areas (predominately in underdeveloped countries

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

• ) [29][30][31]. As described earlier [20], DMB selectively reacts with α-keto acids such as N-acetylneuraminic acid (Neu5Ac), the most abundant natural sialic acid in human cells [1], forming a fluorophore. Analysis by RP-HPLC equipped with a fluorescence detector allows the detection of natural and

• Ac4GlcNCyoc [25][26] were synthesized according to published procedures. AlexaFluor 555-labeled streptavidin and Hoechst 33342 were purchased from Invitrogen. Reactions were monitored by TLC using aluminum sheets pre-coated with silica gel 60 F254 (Merck) with detection by UV light (λ = 254 nm). Additionally

• negative mode. The ionization method was electrospray (ESI) and for detection the time of flight (TOF) method was used. Analysis of recorded mass spectra was performed using the software Xcalibur by Thermo Fischer Scientific. 2,5-Dioxopyrrolidin-1-yl 2-methylcyclopropane-1-carboxylate (3): N

A chemoenzymatic synthesis of ceramide trafficking inhibitor HPA-12

• Seema V. Kanojia,
• Sucheta Chatterjee,
• Subrata Chattopadhyay and
• Dibakar Goswami

Beilstein J. Org. Chem. 2019, 15, 490–496, doi:10.3762/bjoc.15.42

• reused the recovered lipase in ionic liquid at least three times without any significant loss of enzyme activity. The % ee of the (R)-5 and (S)-4 were determined from chiral HPLC analyses (150 mm × 4.6 mm, 5 μm, chiral AD-H column, 5% isopropanol/hexane @ 1.0 mL min−1, UV detection at 254 nm). The

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

• as cell imaging tools [31][32], biosensors and sensors for detection of heavy metals [33]. The tendency of these structures to form hydrogen bonds, to respond to medium effects (solvatochromism) [34] and to certain impurities (e.g., coordination complexes with metal ions) make these compound classes

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

• the detection of ethylene in live cells [91]. BODIPY fluorophores bearing the isopropyloxybenzylidene moiety (101 and 103) reacted with the G-II catalyst to form the HG-II derivatives 102 and 104, respectively (Scheme 21). The resulting compounds are Ru-based profluorescent probes that become

• -metathesis reaction of allyl sulfide 99. Preparation of BODIPY-containing profluorescent probes 102 and 104. Metathesis-based ethylene detection in live cells. First example of stapled peptides via olefin metathesis. RCM of challenging substrate 17 in air and in the presence of water. RCM of N,N

Unexpected loss of stereoselectivity in glycosylation reactions during the synthesis of chondroitin sulfate oligosaccharides

• Teresa Mena-Barragán,
• José L. de Paz and
• Pedro M. Nieto

Beilstein J. Org. Chem. 2019, 15, 137–144, doi:10.3762/bjoc.15.14

• reaction mixture and aided in the detection of a significant amount of the undesired α-anomer. This unexpected stereochemical outcome was also observed in [2 + 2] and [2 + 4] glycosylation reactions between building blocks lacking the fluorous tail. For the GlcA moieties of the CS chains, we chose a 2,3-di

Asymmetric synthesis of a high added value chiral amine using immobilized ω-transaminases

• Antonella Petri,
• Valeria Colonna and
• Oreste Piccolo

Beilstein J. Org. Chem. 2019, 15, 60–66, doi:10.3762/bjoc.15.6

• performed in an Eppendorf ThermoMixer C which combines temperature control and mixing. Chromatographic analysis Analyses of the reactions were performed on a Jasco HPLC system with a Gemini C18 column (150 × 4.6 mm). Elution was carried out at 1 mL/min with detection at 220 nm and a column temperature of 25

• , filtered and after evaporation of the solvent diluted with the mobile phase. Enantiomer separation was achieved on a Jasco HPLC system and a Lux-Cellulose 3 (250 × 4.6 mm) column with a flow rate of 0.5 mL/min, detection at 216 nm and column temperature of 25 °C. The eluent was hexane/isopropanol 9:1. The

Mechanistic studies of an L-proline-catalyzed pyridazine formation involving a Diels–Alder reaction with inverse electron demand

• Anne Schnell,
• J. Alexander Willms,
• S. Nozinovic and
• Marianne Engeser

Beilstein J. Org. Chem. 2019, 15, 30–43, doi:10.3762/bjoc.15.3

• intermediates mimic single steps of the proposed catalytic cycle in the gas phase. Thus, the charge-tagged catalyst proved one more time its superior effectiveness for the detection and study of reactive intermediates at low concentrations. Keywords: charge-tag; electrospray ionization; enamine organocatalysis

• for the Diels–Alder reaction to proceed. Mechanistic studies: ESIMS experiments As ESIMS has a lower limit of detection than NMR, we also studied the proceeding reaction with ESIMS. In its simplest version, i.e., without charge-tagged components (R1, Scheme 3) and at a low concentration (0.005 mmol/mL

• aldol reaction [17]. In our case, it unfortunately does not accumulate in sufficient amounts for detection. Thus, the reaction was setup differently: instead of premixing L-proline (0.05 equiv) and tetrazine substrate 2 (1 equiv) in solution and then adding acetone (4 equiv) to start the reaction as

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

• glycosaminoglycan-binding proteins to date. However, agglutination-inhibition and adhesion assays, genome analyses, and immunological studies have provided the first indications that glycan-binding proteins might be important mediators of TB infections and Mtb pathogenesis. Detection of appendages on the

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

• ). Reaction mixtures were incubated at 70 °C. Substrate and product quantities were determined using HPLC (Waters 1525, column Ascentis Express C18, 2.7 μm, 3.0 × 75 mm, eluent A 0.1% aqeous TFA, eluent B 0.1% TFA / 70% acetonitrile in water, detection at 254 nm, Waters 2489). Kinetic parameters determination

Repurposing the anticancer drug cisplatin with the aim of developing novel Pseudomonas aeruginosa infection control agents

• Mingjun Yuan,
• Song Lin Chua,
• Yang Liu,
• Daniela I. Drautz-Moses,
• Joey Kuok Hoong Yam,
• Thet Tun Aung,
• Roger W. Beuerman,
• May Margarette Santillan Salido,
• Stephan C. Schuster,
• Choon-Hong Tan,
• Michael Givskov,
• Liang Yang and
• Thomas E. Nielsen

Beilstein J. Org. Chem. 2018, 14, 3059–3069, doi:10.3762/bjoc.14.284

• . Student’s t-test was performed for testing differences between groups. *P ≤ 0.05. Cisplatin treatment attenuates P. aeruginosa infections. CFU mL−1 of PAO1 obtained from corneas with and without cisplatin treatment. Dotted horizontal lines represent limit of detection. The mean and s.d. from six experiments

Volatiles from the hypoxylaceous fungi Hypoxylon griseobrunneum and Hypoxylon macrocarpum

• Jan Rinkel,
• Alexander Babczyk,
• Tao Wang,
• Marc Stadler and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2018, 14, 2974–2990, doi:10.3762/bjoc.14.277

• ). Small amounts of matsutake alcohol (3) were also found. This volatile is frequently accompanied by other C8 metabolites [1], which is reflected for H. griseobrunneum by the detection of octan-3-one (8). Trace amounts of a series of alkylated pyrazines including methylpyrazine (9), 2,5-dimethylpyrazine

N-Acylated amino acid methyl esters from marine Roseobacter group bacteria

• Hilke Bruns,
• Lisa Ziesche,
• Nargis Khakin Taniwal,
• Laura Wolter,
• Thorsten Brinkhoff,
• Jennifer Herrmann,
• Rolf Müller and
• Stefan Schulz

Beilstein J. Org. Chem. 2018, 14, 2964–2973, doi:10.3762/bjoc.14.276

• analysis, and structural proposals were derived from the mass spectra and by derivatization. Verification of compound structures was performed by synthesis. NABMEs, NAVMEs and NAGMEs are produced in low amounts only, making mass spectrometry the method of choice for their detection. The analysis of both EI

• and ESI mass spectra revealed fragmentation patterns helpful for the detection of similar compounds derived from other amino acids. Some of these compounds showed antimicrobial activity. The structural similarity of N-acylated amino acid methyl esters and similar lipophilicity to AHLs might indicate a

• them have been characterized so far [14][15][16][17][18]. Such signalling compounds as well as many other unknown metabolites often occur in small amounts, which renders trace detecting methods like GC/MS a suitable approach for their detection and structure elucidation, provided their polarity falls