Get a better glimpse on sequential photoreactions of trisnorbornadienes with ¹⁹F NMR spectroscopy

• Julian Felix Maria Hebborn,
• Ben Eric Merten,
• Thomas Paululat and
• Heiko Ihmels

Beilstein J. Org. Chem. 2026, 22, 527–534, doi:10.3762/bjoc.22.38

• , that is, from monoquadricyclane 2f2,1 to bisquadricyclane 2f1,2 and eventually the trisquadricyclane 2f0,3. The latter was only formed after a sufficient concentration of the intermediates was present (5 min). From this point onwards, the fraction of the starting material 1f and the intermediates 2f2,1

Synthesis and uranyl(VI) extraction performance of a calix[4]pyrrole–tetrahydroxamic acid receptor

• Sara Karnib,
• Rana Baydoun,
• Wissam Zaidan,
• Nancy AlHaddad,
• Omar El Samad,
• Bilal Nsouli,
• Francine Cazier-Dennin and
• Pierre-Edouard Danjou

Beilstein J. Org. Chem. 2026, 22, 486–494, doi:10.3762/bjoc.22.36

• from the decrease in activity concentration. It is important to note that the extraction efficiency of PCP HA was evaluated based solely on the quantification of 238U. Uranium is a naturally occurring radionuclide that exists predominantly as a mixture of three isotopes: 238U, 235U and 234U. Among

Synthesis of a HDAC inhibitor–nanogold probe for cryo-EM visualization in class I HDAC co-repressor complexes

• Wiktoria A. Pytel,
• John W. R. Schwabe and
• James T. Hodgkinson

Beilstein J. Org. Chem. 2026, 22, 480–485, doi:10.3762/bjoc.22.35

• , followed by centrifugation (see Supporting Information File 1 for full details). The resulting Au–(CI-994) conjugate was concentrated to a final volume of 1 mL. The concentration of Au–(CI-994) was determined by UV–vis spectroscopy, using absorbance at 420 nm – a characteristic wavelength for nanogold [19

• ]. Based on the Beer–Lambert law, the concentration was calculated to be 2.69 μM. Attempts at further concentration led to precipitation, indicating limited solubility at higher concentrations. The HDAC inhibitor–nanogold probe inhibits HDAC enzymatic activity in the CoREST complex We first wanted to

• nanogold particle (Au–NH2). Left: Single point concentration HDAC assay. Concentration of Au–NH2 and Au–(CI-994) = 0.54 µM. Concentration of CI-994 = 20 µM. Right: Dose response inhibition of HDAC activity in the CoREST complex with Au–(CI-994). Boc-(Ac)Lys-AMC substrate = 100 µM; CoREST complex = 12.5 nM

Structural reassignment of compound 968, an allosteric glutaminase inhibitor

• Lindsey A. Albertelli,
• Sainabou Jallow,
• Chun Li and
• Scott M. Ulrich

Beilstein J. Org. Chem. 2026, 22, 455–460, doi:10.3762/bjoc.22.33

• cloned into pQE80 were grown at 37 °C overnight in LB supplemented with 100 µg/mL ampicillin. These cultures were diluted 1:100 into 2 L of LB media supplemented with 100 µg/mL ampicillin and grown at 37 °C with shaking at 225 rpm until the OD600 reached 0.6. IPTG was added to a final concentration of

• 9.4), NAD+ (2 mM), glutamate dehydrogenase (1 µL of a 50% glycerol solution, 15 mg/mL), and hydrazine (0.5 µL) and incubated at room temperature for 40 min. The absorbance at 340 nm was measured and converted to glutamate concentration using the extinction coefficient for NADH of 6220 M−1 cm−1. The

Synthesis and anti-cancer activity of naphthalimide–organylselanyl conjugates

• Rajkumar Ravi and
• Selvakumar Karuthapandi

Beilstein J. Org. Chem. 2026, 22, 416–435, doi:10.3762/bjoc.22.29

• concentration of 2 × 10−5 M, as shown in Supporting Information File 1, Figure S21. Both compounds have slightly similar absorption bands. Compound 7 shows an absorption maximum at 395 nm as a broad band peak. In comparison to compound 7, compound 8 displays a slight bathochromic (red) shift, with absorption

• compounds exhibited significant, dose-dependent cytotoxicity, with cell viability decreasing as the concentration increased. Notably, both compounds demonstrated comparable cytotoxic effects against the tested cancer cell line. To assess the significance of variations between concentration and cell

• viability, one-way ANOVA was performed using GraphPad Prism software [64], as shown in Figure 8, comparing the control group to each test concentration of the compound 7 (Figure 8a) and compound 8 (Figure 8b). The results showed no significant differences between the control and 6.12 µM concentrations

Cone p-aminocalix[4]arenes enriched with ‘clickable’ alkyne or azide functionalities

• Ilia Korniltsev,
• Vasily Bazhenov,
• Alexander Gorbunov,
• Dmitry Cheshkov,
• Stanislav Bezzubov,
• Vladimir Kovalev and
• Ivan Vatsouro

Beilstein J. Org. Chem. 2026, 22, 399–415, doi:10.3762/bjoc.22.28

• spectra. Upon tuning the reaction conditions, it was found that a more complete nitration of calixarene 6 along with some suppression of the undesired side reactions could be achieved by decreasing the nitric acid excess (to ≈10 equiv per calixarene aromatic unit) and its concentration in dichloromethane

• (to ≈1 M), reducing the content of acetic acid in the mixture (to 1 mol per mol of HNO3) and extending the room-temperature reaction time to 72 h. Yet, under these conditions, the desired calix[4]arene 11 was obtained in only 31% yield (Scheme 2), and further variations in reagent excess/concentration

• conditions. In line with this, compounds 8–10 having less sterically hindered narrow-rim substitution patterns were found to be more resistant to side reactions during wide-rim nitration as well as to the target exhaustive nitration itself. These reactions required a higher nitric acid concentration of ≈2.5

Design, synthesis and biological evaluation of 2,5-diaryloxazolo[4,5-d]pyrimidin-7-ylamines as selective cytotoxic agents against HeLa cells

• Maryna V. Kachaeva,
• Agnieszka B. Olejniczak,
• Marta Denel-Bobrowska,
• Victor V. Zhirnov,
• Yevheniia S. Velihina,
• Stepan G. Pilyo and
• Volodymyr S. Brovarets

Beilstein J. Org. Chem. 2026, 22, 390–398, doi:10.3762/bjoc.22.27

• antiproliferative and cytotoxic activity against the tested NCI60 cancer cell lines. Also, several other 7-(1,4-diazepan)- and 7-piperazine-substituted [1,3]oxazolo[4,5-d]pyrimidines (structures A and B in Scheme 1) showed cytotoxic activity in the micromolar concentration range against most breast cancer cell

• cells. Therefore, regardless of the concentration in effect, the compound with greater selectivity should be favored. According to this criterion, compounds 1, 7, and 9 show the most significant appeal for further testing as potential agents against cervical cancer. Unfortunately, none of these

• of 670 nm was measured in an ELISA reader (VarioskanLux, Thermo Scientific) and CC50 (50% cytotoxic concentration) was calculated. ADMET analysis Available online web sites of an integrated online platform for Windows: ADMETlab 3.0 [24] and Deep-PK [25] were applied to explore ADMET properties of the

Spirobarbiturates with a pyrrolizidine moiety: synthesis, structure and biological evaluation

• Arthur A. Puzyrkov,
• Andrew S. Drachuk,
• Ekaterina A. Popova,
• Alexander V. Stepakov and
• Vitali M. Boitsov

Beilstein J. Org. Chem. 2026, 22, 274–288, doi:10.3762/bjoc.22.20

• compounds against human cervical carcinoma (HeLa), erythroleukemia (K562), and melanoma (Sk-mel-2) cell lines. It was found that the studied spiro-fused adducts reduced the cell proliferation in a time- and concentration-dependent manner. The results of these investigations for 24 h and 72 h are presented

• tryptanthrin, 11H-benzo[4,5]imidazo[1,2-a]indol-11-one or indolin-2-one instead of the barbituric moiety [58][59][60]. The most interesting effect however, was the increased Sk-mel-2 cell viability under treatment with compounds 4f and 4g at the lowest concentration tested (5 µg/mL). Actin cytoskeleton changes

Configuration–packing synergy enabling integrated crystalline-state RTP and amorphous-state TADF

• Ruiyan Wang and
• Yunan Wu

Beilstein J. Org. Chem. 2026, 22, 224–236, doi:10.3762/bjoc.22.16

• tetrahydrofuran (THF) solution at a concentration of 1.0 × 10−5 M, the steady-state fluorescence spectrum of 1 was recorded, and its phosphorescence spectrum was subsequently measured at a temperature of 77 K to investigate its low-temperature behavior (Figure 3). Following the established spectroscopic

• carbonate (K2CO3) with a concentration of 1 g/mL (3 mL) was added. Subsequently, tetrakis(triphenylphosphine)palladium(0) (0.07 g, 0.06 mmol) was introduced to the reaction mixture to promote the coupling reaction. The mixture was then heated to reflux and maintained at this temperature for an overnight

Synthesis of diaryl phosphates using phytic acid as a phosphorus source

• Kazuya Asao,
• Seika Matsumoto,
• Haruka Mori,
• Riku Yoshimura,
• Takeshi Sasaki,
• Naoya Hirata,
• Yasuyuki Hayakawa and
• Shin-ichi Kawaguchi

Beilstein J. Org. Chem. 2026, 22, 213–223, doi:10.3762/bjoc.22.15

• potassium peroxodisulfate aqueous solution (4.0 w/v %, 5 mL) was added to the diluted phytic acid solution (25 mL), and the resulting mixture was autoclaved (121 °C, 30 min). Thereafter, the solution was diluted with deionized water to a concentration of approximately 1 µg P/mL. Step 3 (measurements): The

• total P concentration was measured via absorption spectrophotometry. The coloring agent (2 mL) was added to the diluted samples (25 mL), thoroughly mixed, and left for 15 min. After 15 min, the absorbance of each sample was measured at 880 nm using a V-650 spectrophotometer (JASCO, Tokyo, Japan). A

Streptoquinolines A and B, new antibacterial meroterpenoids produced by Streptomyces sp. TMPU-A0679

• Akiho Yagi,
• Hitomi Tomura,
• Ami Konno and
• Ryuji Uchida

Beilstein J. Org. Chem. 2026, 22, 185–191, doi:10.3762/bjoc.22.12

• incubated at 37 °C for 24 hours. Bacterial growth was assessed by measuring turbidity at 550 nm using a spectrophotometer. The MIC was defined as the lowest concentration of the test compound that inhibited ≥90% of bacterial growth relative to the control (no compound). Structures of streptoquinolines A (1

Improved synthesis and physicochemical characterization of the selective serotonin 2A receptor agonist 25CN-NBOH

• Adrian G. Rossebø,
• Hannah G. Kolberg,
• Anders E. Tønder,
• Louise Kjaerulff,
• Poul Erik Hansen,
• Karla A. Frydenvang,
• Jesper Østergaard and
• Jesper L. Kristensen

Beilstein J. Org. Chem. 2026, 22, 175–184, doi:10.3762/bjoc.22.11

• sufficient for most biological applications given the high potency of the compound both in vitro and in vivo [6]. Here, we show that if solutions with a higher concentration are needed, pure water could be considered. According to HPLC analysis, 1·HCl was found to be stable in solution in phosphate buffer at

• aqueous solutions of 1·HCl may be prepared and stored well in advance of any application or investigation. Subsequently, the apparent pKa values (concentration-based) for 1 were determined to be 8.4 ± 0.1 and 10.7 ± 0.1 for the protonated amine and phenol, respectively, and the calculated pH-dependent

• h in a temperature-controlled incubator at 25 °C. The concentration of 1 in the buffer solution before and after partitioning, ci and cw, respectively, was determined by HPLC, from which distribution coefficients, D, were calculated according to where Vw and Vo are the volume of the buffer solution

Symmetrical D–π–A–π–D indanone dyes: a new design for nonlinear optics and cyanide detection

• Ergin Keleş,
• Alberto Barsella,
• Nurgül Seferoğlu,
• Zeynel Seferoğlu and
• Burcu Aydıner

Beilstein J. Org. Chem. 2026, 22, 131–142, doi:10.3762/bjoc.22.6

• −, signals of 2b protons have completely disappeared, and the protons of the new species become apparent. An increase in cyanide concentration did not cause any further changes in spectra. This result indicates that cyanide gives a mono-addition to the vinyl group (Scheme 2). DFT results To further confirm

Synthesis and applications of alkenyl chlorides (vinyl chlorides): a review

• Daniel S. Müller

Beilstein J. Org. Chem. 2026, 22, 1–63, doi:10.3762/bjoc.22.1

• caliche deposits in Chile [2]. This concentration of supply raises potential concerns regarding long-term availability and geopolitical vulnerability. Recent interest in alkenyl chlorides has been driven by their occurrence in bioactive natural products (Figure 1) [3][4][5], pharmaceuticals (Figure 2) [6

Chemoenzymatic synthesis of the cardenolide rhodexin A and its aglycone sarmentogenin

• Fuzhen Song,
• Mengmeng Zheng,
• Dongkai Wang,
• Xudong Qu and
• Qianghui Zhou

Beilstein J. Org. Chem. 2025, 21, 2637–2644, doi:10.3762/bjoc.21.204

• , affording 4 in 64% yield (Table 1, entry 2). However, at a higher concentration (0.5 g/L), a significant amount of starting compound 5 remained unconverted even after 4 days, and only 30% of 4 was isolated (Table 1, entry 3). To our delight, upon adding 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) [29] as the

• (Table 1, entry 5). Delightfully, after adding 1% Tween 80 to the above fermentation broth, a complete conversion was observed in 4 days, and compound 4 was obtained in 64% yield (Table 1, entry 6). However, further increasing the substrate concentration to 2.0 g/L resulted in a much lower conversion

Thiazolidinones: novel insights from microwave synthesis, computational studies, and potentially bioactive hybrids

• Luan A. Martinho,
• Victor H. J. G. Praciano,
• Guilherme D. R. Matos,
• Claudia C. Gatto and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2025, 21, 2618–2636, doi:10.3762/bjoc.21.203

• scans) and 151 MHz for 13C NMR (20,480 scans), using an overnight experiment in DMSO-d6 at a concentration of 0.1 M. Specifically, the spectra showed either an absence of expected signals or a lack of signal multiplicity, which was apparent in both the 1H NMR and, more prominently, in the 13C NMR

Efficient solid-phase synthesis and structural characterization of segetalins A–H, J and K

• Liangyu Liu,
• Wanqiu Lu,
• Quanping Guo and
• Zhaoqing Xu

Beilstein J. Org. Chem. 2025, 21, 2612–2617, doi:10.3762/bjoc.21.202

• , successful macrocyclization was achieved by employing benzotriazol-1-yloxytripyrrolidinophosphonium hexafluorophosphate (PyBOP) as the coupling reagent in DMF at a concentration of 10−3 M. After cleavage from the resin and global side-chain deprotection, the crude cyclic peptides were purified by preparative

Silica gel with covalently attached bambusuril macrocycle for dicyanoaurate sorption from water

• Michaela Šusterová and
• Vladimír Šindelář

Beilstein J. Org. Chem. 2025, 21, 2604–2611, doi:10.3762/bjoc.21.201

• concentration in solution reached equilibrium after 15 minutes, consistent with the equilibration time previously established for the non-covalent system SG-BnBU (Supporting Information File 1, Figure S5). Therefore, all subsequent sorption experiments were performed with an equilibration time of 15 minutes

• carried out in nitrogen atmosphere. The dicyanoaurate concentration in solution was determined according to UV–vis spectra recorded with a CARY 60 spectrophotometer (Agilent Technologies). NMR spectra were recorded on a Bruker Avance III 300 spectrometer (300.15 Hz, 298.15 K). Preparation of SG-NHCO-BU1

• min at 250 rpm. Afterwards, SG-NHCO-BU1 or SG-BU1 was left to settle and the supernatant was analyzed. The actual concentration of the anion left in the solution was calculated from a calibration curve. A) Thermogravimetric analyses of BU1, SG, a-SG, and SG-NHCO-BU1. B) UV–vis titration of K[Au(CN)2

Synthesis and characterization of a isothiouronium-calix[4]arene derivative: self-assembly and anticancer activity

• Giuseppe Granata,
• Loredana Ferreri,
• Claudia Giovanna Leotta,
• Giovanni Mario Pitari and
• Grazia Maria Letizia Consoli

Beilstein J. Org. Chem. 2025, 21, 2535–2541, doi:10.3762/bjoc.21.195

• responsiveness to conventional chemotherapy. To the best of our knowledge, calixarene derivatives have not been previously tested as anticancer agents against human renal carcinoma cells. Compound 3 suppressed the proliferation of the renal cancer cells (Figure 3) with a calculated 50% inhibitory concentration

Pentacyclic aromatic heterocycles from Pd-catalyzed annulation of 1,5-diaryl-1,2,3-triazoles

• Kaylen D. Lathrum,
• Emily M. Hanneken,
• Katelyn R. Grzelak and
• James T. Fletcher

Beilstein J. Org. Chem. 2025, 21, 2524–2534, doi:10.3762/bjoc.21.194

• sharing structural similarity regarding N center placement showed antimicrobial activity, as measured by minimum inhibitory concentration assays. MIC values of 2–16 μM towards Gram-positive bacteria Staphylococcus epidermidis and Bacillus subtilis and 8–16 μM towards Saccharomyces cerevisiae yeast were

• bacteria Escherichia coli and Klebsiella aerogenes, and yeast Candida albicans and Saccharomyces cerevisiae was determined using minimum inhibitory concentration (MIC) assays [55][56]. As summarized in Table 4, only five of the twenty-four compounds tested displayed an ability to suppress microbial growth

• control compounds 37–42 (blue lines) in acetonitrile solvent. Synthesis of pentacyclic aromatic heterocycles from varying alkynes.a Synthesis of pentacyclic aromatic heterocycles from varying azides.a Summary of UV–vis absorbance/emission signals. Minimum inhibitory concentration assay results.a

Effect of a photoswitchable rotaxane on membrane permeabilization across lipid compositions

• Udyogi N. K. Conthagamage,
• Lilia Lopez,
• Zuliah A. Abdulsalam and
• Víctor García-López

Beilstein J. Org. Chem. 2025, 21, 2498–2512, doi:10.3762/bjoc.21.192

• structure, and saturation, can result in different membrane mechanics, hydration, thickness, intermolecular spacing, and non-covalent interactions with the rotaxane. For example, EYPC bilayer thickness increases linearly with cholesterol concentration and can induce the formation of nanodomains [16]. Such

• S13, respectively. We investigated whether reducing the concentration of rotaxane 1 from 10 mol % to 5 mol % could provide better control over membrane changes in the more fluid bilayers, specifically in pure EYPC and EYPC/Chol 8:2 LUVs. In pure EYPC, both rotaxanes 1 and 2 induced similar levels of

• release at 5 mol % and 10 mol %, reflecting the high intrinsic permeability of this membrane and the difficulty in modulating it (Supporting Information File 1, Table S30 and Figure S21a). As expected, total release in EYPC/Chol 8:2 LUVs decreased significantly at the lower concentration of the molecules

Ex-situ generation of gaseous nitriles in two-chamber glassware for facile haloacetimidate synthesis

• Nikolai B. Akselvoll,
• Jonas T. Larsen and
• Christian M. Pedersen

Beilstein J. Org. Chem. 2025, 21, 2465–2469, doi:10.3762/bjoc.21.188

• is not easily done as the system is now under pressure. The chamber was then opened to release excess gas (on small scale) and the product in chamber B can be obtained by concentration and purification. The use of other bases than DBU, was also investigated. Similar to the synthesis of

An Fe(II)-catalyzed synthesis of spiro[indoline-3,2'-pyrrolidine] derivatives

• Elizaveta V. Gradova,
• Nikita A. Ozhegov,
• Roman O. Shcherbakov,
• Alexander G. Tkachenko,
• Larisa Y. Nesterova,
• Elena Y. Mendogralo and
• Maxim G. Uchuskin

Beilstein J. Org. Chem. 2025, 21, 2383–2388, doi:10.3762/bjoc.21.183

• synthesized spiro[indoline-3,2'-pyrrolidine] derivatives 4 were evaluated for antimicrobial activity via serial dilution assays across a concentration range of 0.5–1000 µg/mL. The minimum inhibitory concentration (MIC) and minimum bactericidal (fungicidal) concentration (MBC/MFC) against a diverse spectrum of

Conformational effects on iodide binding: a comparative study of flexible and rigid carbazole macrocyclic analogs

• Guang-Wei Zhang,
• Yong Zhang,
• Le Shi,
• Chuang Gao,
• Hong-Yu Li and
• Lei Xue

Beilstein J. Org. Chem. 2025, 21, 2369–2375, doi:10.3762/bjoc.21.181

• spectroscopy. Results and Discussion Partial 1H NMR spectra of PBG and WDG after binding to tetrabutylammonium iodide (TBAI) are presented in Figure 2a and 2b, respectively. All 1H NMR titrations were conducted at a fixed concentration of 8.7 mM. With the addition of 2 equivalents TBAI, the NH peak on the PBG

• shifts down by 0.1902 ppm. When the concentration was increased to 5 equivalents, the NH signal peak of carbazole continued to move towards downfield, with a displacement of 0.4004 ppm to 8.3929 ppm. When the concentration was increased to 10 equivalents, the NH signal peak of carbazole continued to move

• the acceptor. For WDG, the carbazole NH peak on WDG was shifted 0.1725 ppm downfield when 2 equivalents TBAI was added. When the concentration increased to 5 equivalents, the NH signal peak of carbazole continued to move downfield, with a displacement of 0.3649 ppm to 8.2273 ppm, while proton signals

Insoluble methylene-bridged glycoluril dimers as sequestrants for dyes

• Suvenika Perera,
• Peter Y. Zavalij and
• Lyle Isaacs

Beilstein J. Org. Chem. 2025, 21, 2302–2314, doi:10.3762/bjoc.21.176

• , rhodamine 6G, methyl violet 6B; 7500 rpm, 5 min for acridine orange and methylene violet), and the supernatants were analyzed by UV–vis spectroscopy. To determine the dye concentration remaining in the aqueous solutions, appropriate calibration curves were employed (Figure S12 in Supporting Information File

•  1). The removal efficiency was calculated using Equation 1, where c0 is the initial dye concentration, and ct is the dye concentration after sequestration. The results of these experiments are shown in Figure 4. Quite disappointingly, Figure 4 shows that the benzene, naphthalene, and triphenylene

• could be successfully fitted into the Langmuir isotherm model. Figure 7c shows a plot of the data fitted using Equation 2, where qe (mg g−1) represents the amount of methylene violet adsorbed at equilibrium, c (mol L−1) denotes the residual methylene violet concentration at equilibrium, and K (mol−1