Selective ring-opening metathesis polymerization (ROMP) of cyclobutenes. Unsymmetrical ladderphane containing polycyclobutene and polynorbornene strands

• Yuan-Zhen Ke,
• Shou-Ling Huang,
• Guoqiao Lai and
• Tien-Yau Luh

Beilstein J. Org. Chem. 2019, 15, 44–51, doi:10.3762/bjoc.15.4

• recorded on a Varian 400 Unity Plus NMR spectrometer using CDCl3 as solvent at ambient temperature. Chemical shifts were expressed in parts per million using residual solvent protons as internal standards (1H: chloroform: 7.26 ppm). Gel permeation chromatography (GPC) was performed on a Waters GPC

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

• was accomplished with H,H-COSY, HMBC or HSQC spectra. Deuterated solvents chloroform-d1 and DMSO-d6 were obtained from Deutero GmbH and the remaining non-deuterated solvent signals were used as internal standards as references for the 1H shifts and 13C shifts which are all reported on the δ [ppm

New standards for collecting and fitting steady state kinetic data

• Kenneth A. Johnson

Beilstein J. Org. Chem. 2019, 15, 16–29, doi:10.3762/bjoc.15.2

• rate to fall off as substrate is consumed but account for the deviation from linearity by fitting the data using computer simulation. Product inhibition can also be resolved if it contributes significantly to the data [11]. Standards for data collection When it is possible, data should be collected at

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

• diastereomers usually also produce very similar mass spectra [16], a phenomenon that is also reported for E and Z stereoisomers and can lead to wrong structural assignments, if no authentic standards are used for comparison [17]. We have recently reported on two chlorinated aromatic compounds from an endophytic

• elucidation commercially available standards of 9–11 were used, while a synthesis of 12 was performed in our earlier study [24]. Furthermore, a group of monoterpenes and the sesquiterpene alcohol pogostol (19) that was previously reported from other fungi [29][30] were observed. Monoterpenes were comprised of

• (Scheme 1). Comparison of the GC retention index of the natural product (I = 1225) to the retention indices of all six standards narrowed the possible structures down to those of 2,4,5-trimethylanisole (I = 1225) and 2,3,5-trimethylanisole (I = 1227), while all other isomers could be ruled out. The final

Enhanced single-isomer separation and pseudoenantiomer resolution of new primary rim heterobifunctionalized α-cyclodextrin derivatives

• Iveta Tichá,
• Gábor Benkovics,
• Milo Malanga and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2018, 14, 2829–2837, doi:10.3762/bjoc.14.261

• ] (reaction 4) were used as standards. The regioisomeric pattern was thus concluded: the AD regioisomer eluted first, the AC regioisomer second and the AB regioisomer last. Synthesis and large-scale separation of heterobifunctionalized α-CDs After elucidating the homofunctionalized regioisomeric pattern, we

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

• recent years, attempts to raise public awareness on antimicrobial resistance (AMR) and the large threat that it poses towards modern health standards have been made [1]. It is an alarming notion that at an increasing rate of available treatment options proves ineffective in eradicating bacterial

Synthesis of a leopolic acid-inspired tetramic acid with antimicrobial activity against multidrug-resistant bacteria

• Luce Mattio,
• Loana Musso,
• Leonardo Scaglioni,
• Andrea Pinto,
• Piera Anna Martino and
• Sabrina Dallavalle

Beilstein J. Org. Chem. 2018, 14, 2482–2487, doi:10.3762/bjoc.14.224

• Laboratory Standards Institute guidelines [30]. All the strains were treated with a panel of antimicrobial molecules belonging to five pharmacological categories: amoxicillin + clavulanic acid, cephalexin, cefovecin, clindamycin, doxycycline, enrofloxacin and marbofloxacin. Only for S. pseudintermedius

A general and atom-efficient continuous-flow approach to prepare amines, amides and imines via reactive N-chloramines

• Katherine E. Jolley,
• Michael R. Chapman and
• A. John Blacker

Beilstein J. Org. Chem. 2018, 14, 2220–2228, doi:10.3762/bjoc.14.196

• reaction using 16 (15 minutes vs 24 hours in batch mode; Supporting Information File 1, Table S1, entry 2 and Table 2, entries 1–5. The products 14 and 15, prepared in batch, were isolated in 78 and 68% yield, respectively, and characterized (see Supporting Information File 1, S4). These standards enabled

Synthesis and photophysical studies of a multivalent photoreactive Ru^II-calix[4]arene complex bearing RGD-containing cyclopentapeptides

• Sofia Kajouj,
• Lionel Marcelis,
• Alice Mattiuzzi,
• Adrien Grassin,
• Damien Dufour,
• Pierre Van Antwerpen,
• Didier Boturyn,
• Eric Defrancq,
• Mathieu Surin,
• Julien De Winter,
• Pascal Gerbaux,
• Ivan Jabin and
• Cécile Moucheron

Beilstein J. Org. Chem. 2018, 14, 1758–1768, doi:10.3762/bjoc.14.150

• solvents were used as internal standards for 1H NMR (7.26 ppm for CDCl3, 3.31 for CD3OD, 4.79 for D2O, 2.50 for DMSO-d6 and 1.94 ppm for CD3CN) and 13C NMR (77.16 ppm for CDCl3, 49.00 for CD3OD, 39.52 for DMSO-d6 and 118.26 ppm for CD3CN) chemical shift referencing. Abbreviations: s = singlet, d = doublet

Are dispersion corrections accurate outside equilibrium? A case study on benzene

• Tim Gould,
• Erin R. Johnson and
• Sherif Abdulkader Tawfik

Beilstein J. Org. Chem. 2018, 14, 1181–1191, doi:10.3762/bjoc.14.99

• the full potential energy curves. This simple test is not designed to be comprehensive, but rather to interrogate the predictive ability of different approaches. Note that the benchmark set, while slightly inaccurate by modern standards, is predicted to be within 0.1 kcal/mol of more recent benchmarks

Methyl isocyanide as a convertible functional group for the synthesis of spirocyclic oxindole γ-lactams via post-Ugi-4CR/transamidation/cyclization in a one-pot, three-step sequence

• Amarendar Reddy Maddirala and
• Peter R. Andreana

Beilstein J. Org. Chem. 2018, 14, 875–883, doi:10.3762/bjoc.14.74

• chromatographically and spectroscopically pure compounds. 1H and 13C NMR were recorded using a Bruker Avance III 600 MHz. The residual DMSO-d6 1H quintet at δ 2.50 ppm and residual 13C septet at δ 39.51 ppm, CDCl3 1H singlet at δ 7.27 ppm and 13C triplet at δ 77.23 ppm were used as standards for 1H NMR and 13C NMR

Synthesis and in vitro biochemical evaluation of oxime bond-linked daunorubicin–GnRH-III conjugates developed for targeted drug delivery

• Sabine Schuster,
• Beáta Biri-Kovács,
• Bálint Szeder,
• Viktor Farkas,
• László Buday,
• Zsuzsanna Szabó,
• Gábor Halmos and
• Gábor Mező

Beilstein J. Org. Chem. 2018, 14, 756–771, doi:10.3762/bjoc.14.64

• ][49]. Due to this, the usage of internal standards during the evaluation of new potential candidates might be necessary to ensure comparability with previous results. The cytostatic effect of the novel GnRH-III bioconjugates was determined on HT-29 human colon cancer and MCF-7 human breast cancer cell

• lines by alamarBlue® assay. For a better comparison, the well-studied bioconjugates GnRH-III–[8Lys(Dau=Aoa)] (K1) and GnRH-III–[4Lys(Bu), 8Lys(Dau=Aoa)] (K2) were used as positive controls and internal standards. The corresponding IC50 values were calculated by using nonlinear regression (sigmoidal dose

• standards displayed a higher cellular uptake than the new candidates. This became particularly obvious at lower concentrations (2.5 µM and 10 µM). In accordance with our previous data, the cellular uptake of K2 by HT-29 cells is enhanced in comparison to K1 [29][38]. Furthermore, the cellular uptake by HT

Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)

• Thanh-Tuân Bui,
• Fabrice Goubard,
• Malika Ibrahim-Ouali,
• Didier Gigmes and
• Frédéric Dumur

Beilstein J. Org. Chem. 2018, 14, 282–308, doi:10.3762/bjoc.14.18

• to the National Television Standards Committee standard (NTSC) blue values of (0.14, 0.08) [36]. Upon ortho-substitution of the dimesitylphenylboron acceptor with a carbazole, a mutual steric hindrance could be exerted between the donor and the acceptor resulting in the large dihedral angle of 72.6

Volatiles from the tropical ascomycete Daldinia clavata (Hypoxylaceae, Xylariales)

• Tao Wang,
• Kathrin I. Mohr,
• Marc Stadler and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2018, 14, 135–147, doi:10.3762/bjoc.14.9

• , because its erection did not follow good taxonomic standards [14]. The only comparative study available on the production of volatiles that used taxonomically well-characterised Xylariales relied on a panel of strains of the genera Daldinia and Hypoxylon and some allied genera that were previously

• indices, including 4-methylhexan-3-one (6), oct-1-en-3-ol (1), octan-3-one (7), 1-phenylethanol (8), and pogostol (16), which was further confirmed by comparison to authentic standards for 1, 7 and 8 (Table 1 and Scheme 2). Furthermore, the two structurally and biosynthetically related compounds 2-methyl

• to an authentic standard and to synthetic standards of all possible positional isomers. These isomers have been made accessible during our previous work that resulted in the identification of 1,5-dichloro-2,3-dimethoxybenzene as a headspace constituent of an endophytic Geniculosporium sp. [35]. The

Synthesis of ergostane-type brassinosteroids with modifications in ring A

• Vladimir N. Zhabinskii,
• Darya A. Osiyuk,
• Yuri V. Ermolovich,
• Natalia M. Chaschina,
• Tatsiana S. Dalidovich,
• Miroslav Strnad and
• Vladimir A. Khripach

Beilstein J. Org. Chem. 2017, 13, 2326–2331, doi:10.3762/bjoc.13.229

• as standards for identification purposes. Typically, such syntheses were carried out by sequential introduction of functional groups into the starting molecule leading to more complex products [3]. This is a suitable approach for the preparation of one or a limited number of BS, but it rapidly

Diosgenyl 2-amino-2-deoxy-β-D-galactopyranoside: synthesis, derivatives and antimicrobial activity

• Henryk Myszka,
• Patrycja Sokołowska,
• Agnieszka Cieślińska,
• Andrzej Nowacki,
• Maciej Jaśkiewicz,
• Wojciech Kamysz and
• Beata Liberek

Beilstein J. Org. Chem. 2017, 13, 2310–2315, doi:10.3762/bjoc.13.227

• according to Clinical and Laboratory Standards Institute (CLSI) recommendations (for details see Supporting Information File 1). The MICs values are grouped in Table 1 and Table 2. The presented results indicate that some of the tested saponins are characterized by selective activity. Thus, the

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

• remain unreported, since only 15 countries regularly report data to the WHO [3]. In addition, infections might often remain unrecognized, due to poor healthcare standards in most of the affected countries [12]. The first suspected case of a M. ulcerans infection was reported in the early 1860s by Captain

Kinetic analysis of mechanoradical formation during the mechanolysis of dextran and glycogen

• Naoki Doi,
• Yasushi Sasai,
• Yukinori Yamauchi,
• Tetsuo Adachi,
• Masayuki Kuzuya and
• Shin-ichi Kondo

Beilstein J. Org. Chem. 2017, 13, 1174–1183, doi:10.3762/bjoc.13.116

• Instruments Chromato-PRO, Runtime Instruments Ltd., Tokyo, Japan). The following conditions were applied: elution solvent, distilled water containing 0.05 wt/vol % NaCl; flow rate, 0.7 mL/min; column temperature, 40 °C. Calibration was carried out with pullulan standards (peak top molecular weight [Mpeak

Expression, purification and structural analysis of functional GABA transporter 1 using the baculovirus expression system

• Jing Hu,
• Chris Weise,
• Christoph Böttcher,
• Hua Fan and
• Jian Yin

Beilstein J. Org. Chem. 2017, 13, 874–882, doi:10.3762/bjoc.13.88

• molecular weight of approximately 70 kDa, and the overlapping peak 2 (14.7 mL) corresponds to a molecular weight of 45 kDa, which was determined by comparison with the protein standards (Figure 4B). Transmission electron microscopy (TEM) analysis Cryogenic TEM (cryo-TEM) was employed to analyze both peaks

• equilibrium buffer at a flow rate of 0.3 mL/min. The molecular weight of the obtained protein was determined based on the elution profile of proteins standards obtained under the same buffer conditions. TEM analysis Negative staining preparation Sample droplets (5 μL) of the sample were placed onto

Cyclodextrins tethered with oligolactides – green synthesis and structural assessment

• Cristian Peptu,
• Mihaela Balan-Porcarasu,
• Alena Šišková,
• Ľudovít Škultéty and
• Jaroslav Mosnáček

Beilstein J. Org. Chem. 2017, 13, 779–792, doi:10.3762/bjoc.13.77

• precolumn and three PPS PFG columns (d = 8 mm, l = 300 mm) filled with particles with a size of 7 μm and pore sizes of 100, 300 and 1000 Å, respectively. 2,2,2-Trifluoroethanol was used as an eluent. Poly(methyl methacrylate) standards were used for the internal calibration. Methods Bulk polymerization of L

Fluorescent carbon dots from mono- and polysaccharides: synthesis, properties and applications

• Stephen Hill and
• M. Carmen Galan

Beilstein J. Org. Chem. 2017, 13, 675–693, doi:10.3762/bjoc.13.67

• . Environmental Protection Agency standards. Having shown that chemical doping with heteroatoms within the CD synthesis can lead to materials with improved PL and physicochemical properties, this has encouraged research groups to focus their efforts to study the effect of using different heteroatoms

Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis

• Flavio Fanelli,
• Giovanna Parisi,
• Leonardo Degennaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2017, 13, 520–542, doi:10.3762/bjoc.13.51

• hydrochloride. Remarkably, for future applications of the platform, the produced medicines also met the U.S. Pharmacopeia standards. The future use of this kind of platform would concern the “on-demand” production or the “instantaneous” production of short-lived pharmaceuticals (Figure 4). Other advantageous

Polyketide stereocontrol: a study in chemical biology

• Kira J. Weissman

Beilstein J. Org. Chem. 2017, 13, 348–371, doi:10.3762/bjoc.13.39

• group because it mimics the terminal portion of the phosphopantetheine cofactor to which the chain extension intermediates are normally tethered. The stereochemistry of the reduction products was typically established by GC–MS and comparison to authentic synthetic standards, or alternatively by LC–MS

Continuous N-alkylation reactions of amino alcohols using γ-Al₂O₃ and supercritical CO₂: unexpected formation of cyclic ureas and urethanes by reaction with CO₂

• Emilia S. Streng,
• Darren S. Lee,
• Michael W. George and
• Martyn Poliakoff

Beilstein J. Org. Chem. 2017, 13, 329–337, doi:10.3762/bjoc.13.36

• Aldrich and used as standards. 1d,e [50], 6 [51], 7 [52], and 11 [53] were identified as previously described in the literature. GC analysis was carried out using the following instrument and conditions: Online Shimadzu GC-2014 with a high pressure sample loop and an OPTIMA delta-3 column (30 m, 0.25 mm

NMR reaction monitoring in flow synthesis

• M. Victoria Gomez and
• Antonio de la Hoz

Beilstein J. Org. Chem. 2017, 13, 285–300, doi:10.3762/bjoc.13.31

• be coupled in different configurations and the authors used them to prepare from hundreds to thousands of doses of pharmaceuticals that fulfilled the quality standards of the pharmacopeia [10]. In research laboratories that focus on rapid, reproducible and efficient analysis and optimization, and on