Amino acid-based surfactants: sustainable synthesis and antimicrobial mechanisms

• Rafaela Gomes Bezerra,
• Lourdes Pérez and
• Francisco Fábio Oliveira de Sousa

Beilstein J. Org. Chem. 2026, 22, 1067–1085, doi:10.3762/bjoc.22.85

• inhibitory concentration (MIC) or hemolytic potential (HC50: refers to the concentration of a substance that causes 50% hemolysis of red blood cells) or toxicity in cells (IC50: refers to the concentration of a substance that inhibits a biological or biochemical function by 50%). After this selection process

• important as these surfactants demonstrate membrane-disruptive antimicrobial activity that can also affect mammalian cells. In other words, a high therapeutic index means a safer usage [107]. Hemolytic activity and structural dependence The HC50 reflects erythrocyte compatibility, with human red blood cells

Synthesis of functionalized, 13-alkyl-substituted coralyne derivatives and investigation of their interactions with duplex and abasic site-containing DNA

• Laurin Beckmann,
• Jason Lennard Kunze,
• Hannah Karola Strunk,
• Maurice Michel and
• Heiko Ihmels

Beilstein J. Org. Chem. 2026, 22, 1057–1066, doi:10.3762/bjoc.22.84

• -solubility of 2e. Upon addition of DNA, the absorption of the long-wavelength band (λmax = 433 nm) of coralyne derivative 2e decreased with a significant red shift of the absorption maximum. Moreover, two isosbestic points at 335 nm and 440 nm formed initially during DNA titration, but they faded with

• absorption (A) or emission (B) versus cDNA. CD (C) and LD (D) spectra of 2e (c = 10 µM) in the presence of ct DNA in BPE buffer (cNa+ = 16 mM, pH 7.0; with 10% v/v DMSO) at LDR = 0.0–2.0. Red: DNA in the absence of ligand, blue: LDR = 2.0. The arrows indicate the development of the bands during DNA titration

Synthesis and optical resolution of 4,5-diaminohomoadamantane: a promising scaffold for chiral ligands and bioactive compounds

• Polina A. Man’kova,
• Vadim A. Shiryaev,
• Olga S. Podlipnova,
• Marat M. Khisyamov,
• Dmitry S. Nikerov,
• Alexander N. Reznikov and
• Yuri N. Klimochkin

Beilstein J. Org. Chem. 2026, 22, 1013–1022, doi:10.3762/bjoc.22.80

• with LiAlH4, the trans-isomer 15 was isolated. However, the removal of the protecting group in 15 by the known method [90] (sequential action of chloroacetonitrile and Cs2CO3) was unsuccessful. Therefore, we decided to use Red-Al [91][92] for simultaneous reduction and deprotection of 14 yielding only

• diamines. The results of C4–C5–N–H dihedrals scan for staggered conformations with C5–C4–N–H dihedrals 50.66, −61.16, and 178.95 degrees. Red lines in the graphics represent the energy of 10 kJ/mol. The scans were performed using HF/6-31G(d) method. Synthetic route to homoadamantane oximes 3–5. Reduction

The role of spacer length and flexibility in peptide self-assembly

• Julian Link,
• Albin Lahu,
• Manfred Wagner,
• Tanja Weil and
• David Y. W. Ng

Beilstein J. Org. Chem. 2026, 22, 986–996, doi:10.3762/bjoc.22.77

• of H- and J-aggregates. H-type aggregates typically exhibit a hypsochromic (blue) shift of the absorption maximum [49][50], whereas J-type aggregates display a bathochromic (red) shift [51][52]. To evaluate the influence of spacer length on the spectroscopic properties of the otherwise identical

• emit at 546 nm, indicating a slightly different microenvironment of the fluorophore in 8 even under non-assembling conditions (Figure 3A). Upon transitioning to the aqueous buffer system, 6 and 7 exhibit mild blue shifts of their emission maximum, whereas 8 shows a red shift (Figure 3C). Additionally

• enhanced fluorescence likely reflects suppression of non-radiative decay pathways upon self-assembly, potentially due to conformational restriction of the fluorophore, including reduced flexibility of the piperidine unit. In contrast, the red shift observed for 8 under aqueous conditions may arise from

A practical CO₂-mediated synthesis of 5,6-carboxylated silicon-rhodamines for targeted probe development

• Dongjie Hou,
• Shaowei Wu,
• Ning Xu,
• Pengjun Bao,
• Wenhao Jia,
• Qinglong Qiao and
• Zhaochao Xu

Beilstein J. Org. Chem. 2026, 22, 915–924, doi:10.3762/bjoc.22.72

• .22.72 Abstract Silicon-rhodamine (SiR) dyes are among the most important fluorophores for super-resolution imaging owing to their far-red emission, high photostability, and tunable lactone–zwitterion equilibrium. However, their broader application in targeted probe development has been limited by the

• switching and fluorogenic responses, making rhodamines particularly valuable for advanced imaging beyond the optical diffraction limit [14][15][16][17][18][19]. Replacement of the conventional bridging oxygen atom with silicon shifts the emission of rhodamines from red to the far-red region (typically λem

• molecular design framework (Figure 1a). Conformational restriction and optimization of amino substituents have been widely employed to enhance brightness and photostability [8][37][38][39], whereas extension of π-conjugation and electronic tuning have expanded the emission of SiR dyes from the far-red to

Site-specific labelling of native peptides and proteins: chemical and enzymatic strategies

• Antonio Angelastro,
• Jonathan Bargh,
• Subhajit Guria,
• Victor Laserna and
• Louis Luk

Beilstein J. Org. Chem. 2026, 22, 857–881, doi:10.3762/bjoc.22.67

• ], whereas tosylation is one of the few procedures compatible with red blood cells and animal labelling [51]. Alternatively, benzophenone 18, which can be incorporated in the form of an unnatural amino acid, can form a UV-induced diradical for protein modifications (Scheme 7b) [52][53][54][55]. Proteins

Knoevenagel condensation of 4,5- and 1,8-diazafluorenes

• Darya S. Cheshkina,
• Christina S. Becker,
• Alina A. Sonina and
• Maxim S. Kazantsev

Beilstein J. Org. Chem. 2026, 22, 803–812, doi:10.3762/bjoc.22.62

• hexafluorophosphate was used as supporting electrolyte. Pt, Pt wire, and Ag/AgCl were used as working, counter, and reference electrodes, respectively. The measurements were standardized by measuring the red/ox potential of ferrocene after each compound analysis. All potentials are reported vs Fc/Fc+ red/ox couple

• . LUMO energies were estimated using the onset red/ox potentials according to the equation: Elumo= −(Eredonset + 4.8) (eV) X-ray study. Neat compounds were crystallized by a slow vapor diffusion method from the CHCl3/hexane (4,5-DPDAF) and toluene/iPrOH (1,8-DPDAF) systems. The crystal growth time was

• crystallographic axes. The red line shows the (001) plane. The schematic packing motifs are shown in blue, whereas linking [ZnCl]+ moieties are illustrated by blue dots. Voids are shown as brown contact surfaces created using a probe radius of 1.2 Å. Knoevenagel reaction of 1 and 2 under basic conditions

Halogenated azobenzene acrylates: from efficient solution photoswitching to stable solid-state photochromic materials

• Martina Vachtlová,
• Michaela Fecková,
• Vítězslav Zima,
• Jan Podlesný,
• Milan Klikar,
• Oldřich Pytela,
• Patrik Pařík,
• Jakub Opršal,
• Eliška Juhaňáková,
• Veronika Chrtová and
• Filip Bureš

Beilstein J. Org. Chem. 2026, 22, 782–794, doi:10.3762/bjoc.22.60

• of the different halogen atoms, attaching a second halogen atom (e.g., mono/dichloro derivatives 1c and 1d in Figure 5) has more pronounced effect (red-shift). The shape of the obtained spectra is as expected for azobenzene derivatives with the E-isomers featuring a dominant band appearing at 270–400

• absorption maxima of the disubstituted Z-isomers are red-shifted by ≈5 nm. Considering very similar ϕZ values for all three investigated pairs, λZmax is influenced rather electronically via the second halogen atom. The UV–vis absorption spectra were further predicted via TD-DFT and using B3LYP and CAM-B3LYP

• functionals (Table 3 and Supporting Information File 1, Figures S65–88). Both methods afforded the spectra that are similar in shape but either red or blue-shifted compared to the experimental data. The range-separated CAM-B3LYP functional was used to better describe the excited states and charge-transfer

Design, synthesis, and biological evaluation of FXR/ASK1 dual-target modulators

• Xi Zhang,
• Jingyan Wang,
• Ziqiang Zhao,
• Caiyi Wang,
• Zenghui Ye,
• Wei-Yuan Ma,
• Jian-Xing Xu and
• Fengzhi Zhang

Beilstein J. Org. Chem. 2026, 22, 771–781, doi:10.3762/bjoc.22.59

• accumulation. The presence of lipid droplets was confirmed through direct visualization using Oil Red O staining (Figure 3A). The combined treatment with GW4064 and GS4997 exerted a stronger lipolytic effect than either positive control alone, and its activity was comparable to that of Z8. As anticipated, both

• , selonsertib, Z8, Z30, or the combination of GW4064 and selonsertib for 2 h prior to OA stimulation (600 μM). (A) Representative Oil Red O staining images (40×). (B) Quantification of staining intensity by ImageJ. Data are presented as mean ± SD (n = 3). Statistical significance was analyzed by one-way ANOVA

Anti-invasive and cytotoxic evaluation of a (+)-pinoresinol-based semisynthetic library against glioblastoma

• Chen Zhang,
• Kah Yean Lum,
• Jonathan M. White,
• Paul I. Forster,
• Nicholas Booth,
• Sunita A. Ramesh and
• Rohan A. Davis

Beilstein J. Org. Chem. 2026, 22, 691–704, doi:10.3762/bjoc.22.54

• converting resazurin to resorufin, i.e., blue to pink /red in color [40]. Changes in cell viability were detected using fluorescence (excitation at 530–560 and emission at 590 nm) or absorbance (detected at 570 and 600 nm) in a plate reader (FLUOstar Omega, BMG Labtech). In this study, cell viability was

Regioselective approach to 5-arylsulfonylisoxazoles and their antimicrobial activity

• Artem S. Sazonov,
• Dmitry A. Vasilenko,
• Denis V. Porfiriev,
• Yuri K. Grishin,
• Rimma A. Gazzaeva,
• Alisa P. Chernyshova,
• Maxim A. Kryakvin,
• Anna A. Baranova,
• Vera A. Alferova and
• Elena B. Averina

Beilstein J. Org. Chem. 2026, 22, 592–602, doi:10.3762/bjoc.22.45

• the expression of the katushka2S gene. When scanning, the signal from the RFP protein was displayed in green pseudocolor, and from Katushka2S in red. Most of the studied compounds demonstrated low antibacterial activity against the reporter strains, however, 3-nitrosulfonylisoxazoles 3h, 3g and

• red pseudocolor, respectively. Inhibition of Klenow fragment of E. coli DNA polymerase I. A) The principal scheme of the Klenow fragment test. If DNA polymerase I is inhibited by antibiotic doxorubicin, the synthesis of the full-length product will be compromised, and a complete product will not be

Kinetic resolution of racemic planar-chiral vinylcymantrenes by molybdenum-catalyzed asymmetric metathesis dimerization

• Haruna Imazu,
• Hitoshi Izu,
• Yasuhiro Ohki and
• Masamichi Ogasawara

Beilstein J. Org. Chem. 2026, 22, 568–574, doi:10.3762/bjoc.22.42

• ) presence of a substituent (Br or Me) at the position adjacent to the vinyl group in the clockwise direction, (2) absence of a substituent other than hydrogen at the position adjacent to the vinyl group in the counterclockwise direction (CH or P). The substituent adjacent to the vinyl group (marked in red

Molecular tweezer–peptide conjugates disrupt the protein–protein interaction between survivin and histone H3 essential in mitosis

• Catherine Gsell,
• Philipp Rebmann,
• Karina Opara,
• Christine Beuck,
• Peter Bayer,
• David Bier,
• Ingrid R. Vetter and
• Thomas Schrader

Beilstein J. Org. Chem. 2026, 22, 557–567, doi:10.3762/bjoc.22.41

• the peptide tweezer 1 on either K-121 or K-129 (bottom). The positive residues of the H3 peptide are bound to the negatively charged area (red) whereas the phosphorylated threonine contacts a positively charged area, as known from the existing crystal structures. The tweezer moiety can associate with

• complex. A) Lewis structure of the truncated tweezer peptide monophosphate 2b. B) Close-up of the binding motif formed by 2b (tweezer: green, butynyl ester: red) on the survivin surface encapsulating Lys-121 after MD simulation (Desmond, 100 ns, 300 K, 0.15 mM NaCl) using explicit water solvent. A

• red, tweezer green. A) Lewis structures of the new slightly extended binding peptide 3b and the respective click conjugates with butynyl tweezer, mono- and diphosphate 2c and 2d. B) Lewis structures of the new binding peptide 3c and the resulting mono- and diphosphate tweezer conjugates 2e and 2f

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

• variation often leads to a red-shifted absorption, the half-lives of the corresponding quadricyclanes are often decreased at the same time. In particular, the addition of an acetylene unit between the linking aromatic part and the norbornadiene often leads to short half-lives [29][30][31]. As arene-linked

• the photoreaction of 1f; blue: 1f; purple: 2f2,1; pink: 2f1,2; red: 2f0,3. Photochromic reaction of norbornadiene (1a) and quadricyclane (2a) and selected physicochemical properties; λonset = low-energy zero onset of absorption of 1a; t1/2 = half-life of 2a; ΔH = reaction enthalpy of the

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

• using thin-layer chromatography, with the appearance of the characteristic red spot upon treatment with FeCl3 confirming the presence of the hydroxamic acid functionality. Moreover, the formation of the tetra-hydroxamic acid product was confirmed by 1H NMR spectroscopy in deuterated DMSO, as evidenced

• leaching into water was confirmed by depositing a drop of the aqueous supernatant on a TLC plate, which showed no formation of the characteristic red iron-hydroxamate complex upon treatment with FeCl3. These physicochemical properties precluded standard liquid–liquid extraction but were suitable for a

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

• . Error bars represent ± S.E.M. (n = 3). For full assay conditions see Supporting Information File 1. Final round of 2D classification of the cross-linked CoREST complex in the presence of Au–(CI-994) (87,649 particles). Red arrows indicate the position of the Au–(CI-994) probe localized with the CoREST

Synthesis and stereochemical analysis of dynamic planar chiral oxa[7]orthocyclophene

• Yukiho Hashimoto,
• Yuuya Kawasaki,
• Kazunobu Igawa and
• Katsuhiko Tomooka

Beilstein J. Org. Chem. 2026, 22, 436–442, doi:10.3762/bjoc.22.30

• alkyne 6. Subsequent preparation of the lithium acetylide using n-BuLi, followed by treatment with formaldehyde, afforded propargyl alcohol 3a in 70% yield over three steps. The reaction of 3a with Red-Al generated a vinyl aluminum species, which was then treated with iodine to provide the iodinated Z

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

• analysis provides vital insights into the electronic characteristics of atoms within a molecule [61]. In the MEP maps, the colour distribution follows the order blue, green, and red, representing increasing electrostatic potential. The blue regions correspond to more electropositive areas, while the red

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

• ]arenes by joining propargyl/2-azidoethyl and p-amino groups on a common platform. Parts of 1H,13C HMBC spectra of calixarenes 12 (a) and 13 (b) recorded in CDCl3 solutions at 600 MHz. Red lines show the key correlations between signals from the calixarene narrow-rim substituents and aromatic units

Electrosynthetic access to unsymmetrical oxaza[8]helicenes with high chiral stability and strong circularly polarized luminescence (CPL)

• Tin Zar Aye,
• Rubal Sharma,
• Muthu Karuppasamy,
• Daiya Suzuki,
• Haruka Nakajima,
• Yoshitane Imai,
• Mitsuhiro Arisawa,
• Mohamed S. H. Salem and
• Shinobu Takizawa

Beilstein J. Org. Chem. 2026, 22, 372–382, doi:10.3762/bjoc.22.25

• ]helicenes 5a and 5b in chloroform (1 × 10−5 M) were recorded and compared with those of the corresponding oxaza[7]helicenes 6a and 6b (Figure 4A and 4B). As expected, extension of the helical π-systems in 5 leads to enhanced conjugation relative to 6, manifested in red-shifted absorption and emission bands

• and second fractions of the chiral HPLC analysis were assigned as the (P)- and (M)-enantiomers, respectively, for all 5a,b and 6a,b. As expected, the increase in helical length (n) from 7 to 8, 5a and 5b exhibited more red-shifted maximum |gabs| values at around 350 nm, whereas 6a and 6b showed values

• dashed lines for (P)-configuration of 5a (black), 5b (blue), 6a (green), and 6b (red). Recent examples of hetero[8]helicenes: (A) symmetric hetero[8]helicenes; (B) unsymmetrical hetero[8]helicenes; (C) short-step electrosynthetic access to new unsymmetrical oxaza[8]helicenes. Short-step synthesis of

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

• CrystalExplorer 21.5 [55]. On the Hirshfeld surface, color coding indicates the nature of intermolecular interactions: red highlights contacts shorter than the van der Waals radius, white represents distances equal to the van der Waals radius, and blue denotes contacts longer that the van der Waals radius. Figure

•  4 shows front and back views of the Hirshfeld surfaces (dnorm) for compounds 4b and 4c. The Hirshfeld surface for compound 4b with dnorm map plotted (ranging from −0.8499 (red) to 1.4229 (blue) a.u.) is presented in Figure 5. Analysis of the HS revealed the presence of several intermolecular

• one of the water hydrogens interacts with a carbonyl group of the barbiturate ring (C=O···H–O = 2.867 Å). The HS for compound 4c with dnorm map plotted (ranging from −0.6673 (red) to 1.4313 (blue) a.u.), is shown in Figure 6. The dnorm map highlights key intermolecular interactions (marked in red

Conformational analysis of difluoromethylornithine: factors influencing its gas-phase and bioactive conformations

• Matheus P. Freitas

Beilstein J. Org. Chem. 2026, 22, 237–243, doi:10.3762/bjoc.22.17

• )/CBS level of theory. Color labels: H = white, C = grey, N = blue, O = red, F = electric blue. (S)-DFMO bound within the active site of human arginase I obtained from the Protein Data Bank (3GN0) (https://doi.org/10.2210/pdb3gn0/pdb, [21]). Dotted lines represent hydrogen-bonding interactions with

• amino acid residues and water molecules, while the ligand is delineated by a contour line to distinguish it from the binding cavity. Lowest-energy type-I, type-II, and type-III conformers of the zwitterionic form of (S)-DFMO. Color labels: H = blue, C = pink, N = orange, O = red, F = yellow. DFT

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

• essentially unchanged, whereas its fluorescence emission undergoes a monotonic red shift with increasing solvent polarity (or polarizability), accompanied by an enlarged Stokes shift – a typical solvatochromic behavior. The weak solvent dependence of the absorption spectra indicates that the difference in

• the ground state, lowering the excited-state energy and thus the photon energy, which manifests macroscopically as a red-shifted emission. In polar media, the oriented polar solvent shell stabilizes the CT state more effectively than the ground or locally excited (LE) state, further decreasing the

• a result of RTP, as the sub-second lifetime and the pronounced thermal quenching behavior are characteristic features of RTP. Additionally, the red shift observed in the delayed emission spectrum compared to the steady-state emission is consistent with the behavior of lower-energy emissions that are

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

• recrystallized from ethanol (Figure 3, purple), a similar pattern is observed, indicating a high degree of crystallinity. Furthermore, samples of 1·HCl prepared either by rapid precipitation in organic solvents, as described in the Experimental section (red), or material isolated from a saturated solution of 1

• , oxygen atoms red, and chloride ion green. b) The crystal packing reveals alternating layers, a polar layer with hydrogen bonds (black dashed lines), and a hydrophobic layer with π–π-stacking (grey dashed lines). SCXRD and XRPD spectra of different preparations of 1·HCl. Blue: SCXRD spectrum of 1·HCl. Red

• , green, and purple: XRPD spectra of 1·HCl after recrystallization (red), directly as synthesized (green), and of a slurry obtained by stirring excess solid in ultrapure water for 3 days (purple). TGA and DSC thermograms of 1·HCl. Calculated pH-dependent species distribution curves for 25CN-NBOH (1). a

A new synthesis of Tyrian purple (6,6’-dibromoindigo) and its corresponding sulfonate salts

• Holly Helmers,
• Mark Horton,
• Julie Concepcion,
• Jeffrey Bjorklund and
• Nicholas C. Boaz

Beilstein J. Org. Chem. 2026, 22, 167–174, doi:10.3762/bjoc.22.10

• red shift by 16 and 15 nm with a moderate increase in molar absorptivity, respectively, for compounds 9 and 10 [29]. This means that to the human eye, di- and trisulfonated derivatives of 1 appear blue, not purple. A smaller shift in λmax is observed when indigo is sulfonated, allowing for its blue