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Search for "concentration" in Full Text gives 1388 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.

Tautomerism and switching in 7-hydroxy-8-(azophenyl)quinoline and similar compounds

  • Lidia Zaharieva,
  • Vera Deneva,
  • Fadhil S. Kamounah,
  • Nikolay Vassilev,
  • Ivan Angelov,
  • Michael Pittelkow and
  • Liudmil Antonov

Beilstein J. Org. Chem. 2025, 21, 1404–1421, doi:10.3762/bjoc.21.105

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  • crystal was used and the samples were scanned 128 times. The UV–vis spectra were measured on a Jasco V-570 UV–vis–NIR spectrophotometer using spectral grade solvents in the concentration range ≈10−5 mol/L. The steady-state fluorescence spectra were recorded with a FluoroLog 3-22 (HORIBA
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Published 10 Jul 2025

N-Salicyl-amino acid derivatives with antiparasitic activity from Pseudomonas sp. UIAU-6B

  • Joy E. Rajakulendran,
  • Emmanuel Tope Oluwabusola,
  • Michela Cerone,
  • Terry K. Smith,
  • Olusoji O. Adebisi,
  • Adefolalu Adedotun,
  • Gagan Preet,
  • Sylvia Soldatou,
  • Hai Deng,
  • Rainer Ebel and
  • Marcel Jaspars

Beilstein J. Org. Chem. 2025, 21, 1388–1396, doi:10.3762/bjoc.21.103

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  • show modest activity against L. major. All the remaining compounds (1–3 and 5–7) tested in this assay showed no activity at the highest concentration very likely due to the free carboxylic acid moiety present in some compounds (1, 3 and 7), prevent uptake into the parasites. This could also explain the
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Published 04 Jul 2025

Oxetanes: formation, reactivity and total syntheses of natural products

  • Peter Gabko,
  • Martin Kalník and
  • Maroš Bella

Beilstein J. Org. Chem. 2025, 21, 1324–1373, doi:10.3762/bjoc.21.101

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Published 27 Jun 2025

Recent advances and future challenges in the bottom-up synthesis of azulene-embedded nanographenes

  • Bartłomiej Pigulski

Beilstein J. Org. Chem. 2025, 21, 1272–1305, doi:10.3762/bjoc.21.99

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  • regioselective functionalization at the periphery of the PAHs. Besides triflyloxylation (42, 43), the introduction of one or two dichlorovinylene groups (43, 44) was observed. As in previous cases, the exact ratio of the products depended on the amount of DDQ and concentration of the precursor. Analysis of NICS
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Published 26 Jun 2025

Optimized synthesis of aroyl-S,N-ketene acetals by omission of solubilizing alcohol cosolvents

  • Julius Krenzer and
  • Thomas J. J. Müller

Beilstein J. Org. Chem. 2025, 21, 1201–1206, doi:10.3762/bjoc.21.97

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  • addition, since condensations are affected by the bimolecular addition as an elementary step, special attention to the concentration of the nucleophiles has to be paid. According to Mayr’s nucleophilicity scales [8][9][10], a nucleophilicity parameter N for the specific S,N-ketene acetal intermediate 4 can
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Published 20 Jun 2025

Synthesis of β-ketophosphonates through aerobic copper(II)-mediated phosphorylation of enol acetates

  • Alexander S. Budnikov,
  • Igor B. Krylov,
  • Fedor K. Monin,
  • Valentina M. Merkulova,
  • Alexey I. Ilovaisky,
  • Liu Yan,
  • Bing Yu and
  • Alexander O. Terent’ev

Beilstein J. Org. Chem. 2025, 21, 1192–1200, doi:10.3762/bjoc.21.96

Graphical Abstract
  • ) sulfate under an argon atmosphere afforded 3a in 33% yield. These results indicate, that copper(II) at high loading is capable of oxidizing H-phosphonate even in inert conditions [72]; however, a balanced concentration of oxygen in the reaction mixture is required for recycling of copper catalyst and
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Published 20 Jun 2025

Investigations of amination reactions on an antimalarial 1,2,4-triazolo[4,3-a]pyrazine scaffold

  • Henry S. T. Smith,
  • Ben Giuliani,
  • Kanchana Wijesekera,
  • Kah Yean Lum,
  • Sandra Duffy,
  • Aaron Lock,
  • Jonathan M. White,
  • Vicky M. Avery and
  • Rohan A. Davis

Beilstein J. Org. Chem. 2025, 21, 1126–1134, doi:10.3762/bjoc.21.90

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  • -PfATP4 activity would be required to definitively assess the tolerability of tertiary alkylamines at position 8. Whilst compounds 1, 2 and 4–12 showed no cytotoxicity against HEK293 cells at the top concentration tested (80 µM), for those compounds with concomitant antimalarial activity (1, 10–12), their
  • . Meaningful selectivity indices for these compounds could, therefore, likewise not be calculated. Hence, the mean % growth inhibition (duplicate, n = 1) at the top concentration is indicated in Table 1. Conclusion A modified approach for amine substitution of 5-chloro-3-(4-chlorophenyl)-[1,2,4]triazolo[4,3-a
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Published 10 Jun 2025

Gold extraction at the molecular level using α- and β-cyclodextrins

  • Susana Santos Braga

Beilstein J. Org. Chem. 2025, 21, 1116–1125, doi:10.3762/bjoc.21.89

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  • several methods, with highlight to gravity concentration (based on the higher density of gold), cyanidation, and mercury amalgam [15]. The gravity method is a simple and, from the viewpoint of the environment, relatively harmless process that works well as a stand-alone for high-density gold particles and
  • networks to optimize the chemical parameters of the extraction. An optimal value of gold removal, lying between 98 and 98.9%, was found to occur with a contact time of 40 minutes, a concentration of α-CD of 11.61 g/L and KOH was added in enough quantity to raise the solution pH to 5 [47][48]. Complexes of
  • , containing 0.6 mg of gold) were mixed for 30 minutes with increasing amounts of α-CD (concentrations ranging from 1–10% w/v) [49]. Extraction yields were shown to increase with concentration of α-CD. The highest concentration tested, 10%, afforded 19% yield in gold. Competitive extraction tests with gold and
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Published 06 Jun 2025

Supramolecular assembly of hypervalent iodine macrocycles and alkali metals

  • Krishna Pandey,
  • Lucas X. Orton,
  • Grayson Venus,
  • Waseem A. Hussain,
  • Toby Woods,
  • Lichang Wang and
  • Kyle N. Plunkett

Beilstein J. Org. Chem. 2025, 21, 1095–1103, doi:10.3762/bjoc.21.87

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  • in this HIM system, the 1H NMR titration data was used to determine the association constants for metal coordination. Two stock solutions were prepared with one containing a concentration of 2.83 mM of the macrocycle (HIM) in a mixture of deuterated chloroform and acetone 1:2. The second stock
  • solution contained the metal BArF20 or BArF24 at a concentration of 10 times that of the HIM concentration. Gradually adding the metal BArF20 or BArF24 stock solution to the HIM stock solution in an NMR tube allowed the host-to-guest ratio to be varied while keeping the host concentration constant. With
  • fluctuation of the concentration of the host and the guest, which contribute to the x-axis in the fitting process. The isothermal fitting to 2:1 models is often prone to overfitting with NMR data and is noticeable with the fit for 1. However, the general trend does correlate with the strength of the
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Published 30 May 2025

On the photoluminescence in triarylmethyl-centered mono-, di-, and multiradicals

  • Daniel Straub,
  • Markus Gross,
  • Mona E. Arnold,
  • Julia Zolg and
  • Alexander J. C. Kuehne

Beilstein J. Org. Chem. 2025, 21, 964–998, doi:10.3762/bjoc.21.80

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Published 21 May 2025

Recent advances in controllable/divergent synthesis

  • Jilei Cao,
  • Leiyang Bai and
  • Xuefeng Jiang

Beilstein J. Org. Chem. 2025, 21, 890–914, doi:10.3762/bjoc.21.73

Graphical Abstract
  • , tetrabutylammonium iodide (TBAI), and water significantly accelerated aryne generation, thereby increasing its local concentration. This favored aryne coordination to the palladium center, followed by CO insertion and reductive elimination to furnish phenanthridinones. In contrast, when dppm was introduced
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Published 07 May 2025

4-(1-Methylamino)ethylidene-1,5-disubstituted pyrrolidine-2,3-diones: synthesis, anti-inflammatory effect and in silico approaches

  • Nguyen Tran Nguyen,
  • Vo Viet Dai,
  • Luc Van Meervelt,
  • Do Thi Thao and
  • Nguyen Minh Thong

Beilstein J. Org. Chem. 2025, 21, 817–829, doi:10.3762/bjoc.21.65

Graphical Abstract
  • drug dexamethasone (IC50 = 13.25 ± 1.39 µM). At a concentration of 100 µM, the NO inhibition of pyrrolidine-2,3-dione derivatives 5a, 5b, and 5e was 53.65%, 50.22%, and 63.65%, respectively, as compared to 85.04% of dexamethasone. It is clear that the presence of a nitro group or halogen atom on the
  • benzene ring at the 5-position of pyrrolidine-2,3-dione core in compounds 5c and 5d could relate to the lower inhibitory activity of 23.76% and 38.41% at the concentration of 100 µM, respectively, as compared to 5a and 5b. However, the existence of a nitro group on the aromatic ring attached to the 1
  • -position of that heterocyclic core in compound 5e resulted in a dramatic increase in the NO inhibitory capability. More importantly, all studied compounds 5a–e did not show cytotoxicity to macrophage cells; 90.35–95.74% cells survived at the concentration of 100 µM of 5a–e (Table S3 in Supporting
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Published 24 Apr 2025

Recent advances in the electrochemical synthesis of organophosphorus compounds

  • Babak Kaboudin,
  • Milad Behroozi,
  • Sepideh Sadighi and
  • Fatemeh Asgharzadeh

Beilstein J. Org. Chem. 2025, 21, 770–797, doi:10.3762/bjoc.21.61

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  • concentration, with a decrease in efficiency observed at lower concentrations. The reaction proceeded well under nitrogen, indicating that the oxidation process is unrelated to the presence or absence of oxygen. The yields of some products are likely due to the strong electron-withdrawing effects of the
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Published 16 Apr 2025

Orthogonal photoswitching of heterobivalent azobenzene glycoclusters: the effect of glycoligand orientation in bacterial adhesion

  • Leon M. Friedrich and
  • Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2025, 21, 736–748, doi:10.3762/bjoc.21.57

Graphical Abstract
  • . Supporting Information File 1, Figures S13–S16). DMSO is known for its bactericidal effect and still, the use of this organic solvent in bioassays is common [42]. In general, a DMSO concentration of less than 10% (v/v) is accepted as nontoxic [43]. In any case, the effect of DMSO in the assays was carefully
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Published 08 Apr 2025

Synthesis of HBC fluorophores with an electrophilic handle for covalent attachment to Pepper RNA

  • Raphael Bereiter and
  • Ronald Micura

Beilstein J. Org. Chem. 2025, 21, 727–735, doi:10.3762/bjoc.21.56

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  • concentrations of the reaction mixture were: 2.5 µM RNA, 50 µM ligand, 50 mM HEPES, 100 mM KCl and 2.0 mM MgCl2. After incubation (37 °C, 5 hours), the reaction was quenched by adding 40 µL of a Na2H2EDTA solution (200 mM) to reach a final concentration of 80 mM Na2H2EDTA in a volume of 100 µL. Each sample was
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Published 04 Apr 2025

Acyclic cucurbit[n]uril bearing alkyl sulfate ionic groups

  • Christian Akakpo,
  • Peter Y. Zavalij and
  • Lyle Isaacs

Beilstein J. Org. Chem. 2025, 21, 717–726, doi:10.3762/bjoc.21.55

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  • temperature overnight. Afterwards, the mixture was centrifuged (4400 rpm, 10 min) to pellet excess insoluble C1. An aliquot of the supernatant and a solution of dimethyl malonic acid as a non-binding internal standard of known concentration were transferred to an NMR tube followed by collection of a 1H NMR
  • monitored the chemical shift of Ha (Supporting Information File 1, Figure S14). Over this dilution range, the resonance for Ha remains a sharp singlet at 6.94 ppm. Accordingly, we conclude that C1 remains monomeric at the low concentration (100 μM) typically employed for isothermal titration calorimetry
  • achieved by changing the concentration of host in the ITC cell [76][77][78]. Figure 7a presents the thermogram recorded when a solution of C1 (100 μM) in phosphate-buffered saline (PBS) in the ITC cell was titrated with a solution of CHDA (1 mM) from the ITC injection syringe. The DP versus time data in
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Published 03 Apr 2025

Asymmetric synthesis of fluorinated derivatives of aromatic and γ-branched amino acids via a chiral Ni(II) complex

  • Maurizio Iannuzzi,
  • Thomas Hohmann,
  • Michael Dyrks,
  • Kilian Haoues,
  • Katarzyna Salamon-Krokosz and
  • Beate Koksch

Beilstein J. Org. Chem. 2025, 21, 659–669, doi:10.3762/bjoc.21.52

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  • fluorinated alkyl iodide precursor 10, the corresponding alkylation reaction with the Ni(II) complex 1 was conducted under previously optimized conditions for the synthesis of Fmoc-TfIle [13] in terms of base (NaH) and solvent (DMF) and thoroughly screened in terms of base equivalents, concentration and
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Published 21 Mar 2025

Entry to 2-aminoprolines via electrochemical decarboxylative amidation of N‑acetylamino malonic acid monoesters

  • Olesja Koleda,
  • Janis Sadauskis,
  • Darja Antonenko,
  • Edvards Janis Treijs,
  • Raivis Davis Steberis and
  • Edgars Suna

Beilstein J. Org. Chem. 2025, 21, 630–638, doi:10.3762/bjoc.21.50

Graphical Abstract
  • observed (see Supporting Information File 1, page S3). Decrease in supporting electrolyte concentration led to a drop in yields (Table 1, entry 9 vs entry 8), whereas current density deviations from 12 mA/cm2 did not affect the outcome of 6a (see Supporting Information File 1, page S4). Interestingly
  • (0.1 M, electrochemical grade) was employed as the supporting electrolyte in 5:1 MeCN/H2O solution. The electrolyte was purged with argon for at least 3 min prior to recording. Compounds 6a and 9a were analyzed at a concentration of 3 mM or 6 mM and at a scan rate of 100 mV s−1. The peak potential Ep
  • mM concentration, respectively, in 5:1 MeCN/H2O (0.1 M Et4N–BF4). B) Anodic oxidation of pyrrolidine 6a. Plausible mechanism for formation of pyrrolidine 6a and hemiaminal 10a. Preparation of malonic acid monoester 9a. Electrolysis of acid 9d in deuterated solvents. Scope of the decarboxylative
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Published 19 Mar 2025

Semisynthetic derivatives of massarilactone D with cytotoxic and nematicidal activities

  • Rémy B. Teponno,
  • Sara R. Noumeur and
  • Marc Stadler

Beilstein J. Org. Chem. 2025, 21, 607–615, doi:10.3762/bjoc.21.48

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  • added to 120 µL aliquots of a cell suspension (5 × 104 cells/mL) in 96-well microplates. After 5 days incubation, an MTT assay was performed, and the absorbance measured at 590 nm using an ELISA plate reader (Victor). The concentration at which the growth of cells was inhibited to 50% of the control
  • (100, 50, 25 and 12.5 μg/mL). Ivermectin was used as a positive control at the same concentration ranges as the tested compounds and MeOH was used as a negative control. Percentages of mortality were calculated, then the results were expressed as a LD90 and LD50. Preparation of massarilactone D
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Published 17 Mar 2025

Asymmetric synthesis of β-amino cyanoesters with contiguous tetrasubstituted carbon centers by halogen-bonding catalysis with chiral halonium salt

  • Yasushi Yoshida,
  • Maho Aono,
  • Takashi Mino and
  • Masami Sakamoto

Beilstein J. Org. Chem. 2025, 21, 547–555, doi:10.3762/bjoc.21.43

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  • chiral halonium salt. Next, the reaction temperature was optimized, and −40 °C was found to be optimal (Table 1, entries 7–9). Further optimization of the reaction conditions (amounts of potassium carbonate and pre-nucleophile, catalyst loading, and concentration) were conducted, and the reaction with
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Published 12 Mar 2025

Binding of tryptophan and tryptophan-containing peptides in water by a glucose naphtho crown ether

  • Gianpaolo Gallo and
  • Bartosz Lewandowski

Beilstein J. Org. Chem. 2025, 21, 541–546, doi:10.3762/bjoc.21.42

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  • – a chemoselective receptor for aromatic amino acid esters in water. Fluorescence emission spectra of receptor 1 (25 μM in H2O) upon addition of increasing amounts of tripeptide 2. The concentration of the guest corresponding to each curve is indicated on the right. The arrow marks the quenching of
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Published 10 Mar 2025

Deep-blue emitting 9,10-bis(perfluorobenzyl)anthracene

  • Long K. San,
  • Sebastian Balser,
  • Brian J. Reeves,
  • Tyler T. Clikeman,
  • Yu-Sheng Chen,
  • Steven H. Strauss and
  • Olga V. Boltalina

Beilstein J. Org. Chem. 2025, 21, 515–525, doi:10.3762/bjoc.21.39

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  • photoproducts were insoluble resulting in decreased concentration of 9,10-ANTH(BnF)2 in the irradiated solution or new photoproducts had similar absorption features. To identify the photoproducts in the irradiated solutions of ANTH and 9,10-ANTH(BnF)2, complementary NMR analyses were carried out (Figures S6 and
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Published 07 Mar 2025

Unprecedented visible light-initiated topochemical [2 + 2] cycloaddition in a functionalized bimane dye

  • Metodej Dvoracek,
  • Brendan Twamley,
  • Mathias O. Senge and
  • Mikhail A. Filatov

Beilstein J. Org. Chem. 2025, 21, 500–509, doi:10.3762/bjoc.21.37

Graphical Abstract
  • fluorescence spectra are presented in Supporting Information File 1 (Figures S12–S14). For the fluorescence quantum yield measurements, solutions of each bimane were prepared, and the concentration was adjusted so that the absorbance at the right shoulder of the band at 360 nm falls within the range of 0.03
  • using UV–vis spectroscopy, where the concentration was adjusted such that the absorbance is 2.164 at the λmax. The solution was added into a quartz fluorescence cuvette, and irradiated for 15 minutes at a time using the same 405 nm LEDs in a turntable chamber. Structures of a) the unfunctionalized
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Published 05 Mar 2025

Synthesis of N-acetyl diazocine derivatives via cross-coupling reaction

  • Thomas Brandt,
  • Pascal Lentes,
  • Jeremy Rudtke,
  • Michael Hösgen,
  • Christian Näther and
  • Rainer Herges

Beilstein J. Org. Chem. 2025, 21, 490–499, doi:10.3762/bjoc.21.36

Graphical Abstract
  • neurotransmitters [10][11] or as switching units for potential dependent potassium channels [12]. Compared to the Z → E conversion rate of 92% (in n-hexane) of the parent diazocine the conversion in water/DMSO mixtures is decreasing with increasing water concentration (73% in water/DMSO 9:1) [8][9][10][11][12
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Published 04 Mar 2025

Synthesis of electrophile-tethered preQ1 analogs for covalent attachment to preQ1 RNA

  • Laurin Flemmich and
  • Ronald Micura

Beilstein J. Org. Chem. 2025, 21, 483–489, doi:10.3762/bjoc.21.35

Graphical Abstract
  • . PreQ1 riboswitches sense the cellular concentration of preQ1 and regulate the expression of downstream located genes associated with the biosynthesis or transport of Q in a feedback-like manner. Binding of PreQ1 to the mRNA causes the riboswitch to commit an altered folding pathway, which affects the
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Published 04 Mar 2025
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