Rhodopyran, a carboxylated hexahydrocyclopenta[b]pyran from Rhodococcus

• Enjuro Harunari,
• Sara Fushimi and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2026, 22, 1107–1113, doi:10.3762/bjoc.22.89

• correlations and key HMBC correlations. The dashed blue arrow indicates the weak but observed HMBC correlation from H-7a to C-4. Selected vicinal 3JHH values and key NOESY correlations used to assign the relative configuration of rhodopyran (1). Tentative biosynthetic scenarios for rhodopyran (1

Controlled supramolecular assemblies of luminescent tridentate cyclometalated alkynylgold(III) amphiphiles in aqueous media

• Kelvin Sze-Yim Cai,
• Brian Boyan Liu and
• Franco King-Chi Leung

Beilstein J. Org. Chem. 2026, 22, 1097–1106, doi:10.3762/bjoc.22.88

• intensity upon the addition of 1.0–2.0 equiv of sodium tosylate (Figure 2c red line and blue line). However, the vibronic-structured emission band diminished upon the addition of 4.0 equiv of sodium tosylate (Figure 2c, green line). The time-dependent UV–vis adsorption spectra of the annealed solution of GA

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

• inhibitor of APE1-mediated repair of AP sites. Taken together these results provide a blue-print for the development of selective coralyne-based AP–DNA ligands. Even though only one example was made available, so far, the approach may be easily varied to obtain different linker lengths and linking units, so

• 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 of novel 1,2,4-oxadiazole-isoxazoline hybrids and their in silico potential with adenosine receptors

• Pshtiwan S. Mohammed,
• Mohammed K. S. Dalo,
• Onur C. Yazıcı,
• Muhammet Yildirim and
• Akın Sağırlı

Beilstein J. Org. Chem. 2026, 22, 1033–1047, doi:10.3762/bjoc.22.82

• compounds (7x-(S), 7x-(R), 7j-(S), 7aw-(S), 7aw-(R), 7ah-(S)) and reference (co-crystallized) ligand with A1 adenosine receptor. Green arrows: conventional hydrogen bonds; pink region: alkyl connections; light pink region: pi-alkyl connections; blue region: halogen interactions; light green region: carbon

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

• substantial blue shifts observed for compounds 6 and 7 are consistent with excitonic H-type coupling arising from π–π-stacking interactions within ordered assemblies, as also suggested by the CD data (Supporting Information File 1, Figure S41). The magnitude of these shifts suggests the formation of

• 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

Recent advances in copper-catalyzed direct hydroamination of alkenes with (hetero)aromatic amines

• Hyejeong Lee and
• Yunmi Lee

Beilstein J. Org. Chem. 2026, 22, 925–947, doi:10.3762/bjoc.22.73

• %) and LiOt-Bu in CH3CN under blue LED irradiation enabled the coupling of alkenes 49 with carbazoles, indoles, and aniline derivatives to afford the corresponding amination products 50 with Markovnikov regioselectivity. Various styrene derivatives bearing electron-donating or electron-withdrawing

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

• (Figure 4c). Segmental reconstruction using continuously acquired image sequences enabled real-time tracking of filopodial growth and wiggling dynamics (Figure 4d). During the first 0–160 s, the filopodium indicated by the blue arrow underwent slight retraction, followed by gradual extension. Its length

The trans-influence in gold chemistry from a catalytic perspective

• Manfred Bochmann

Beilstein J. Org. Chem. 2026, 22, 838–856, doi:10.3762/bjoc.22.66

• intense blue on warming and appears to be the first case of a gold(III) complex emitting by a thermally activated delayed fluorescence (TADF) process, where excited singlet and triplet states are of comparable energy, which allows effective triplet harvesting and high quantum yields. Luminescence

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

• ). Layers of dimers alternate with layers of ZnCl3(H2O)− anions containing free solvent accessible volume 284 Å3 with removed disordered water molecules (Figure 2g). Figure 2 also shows a schematic representation of the packing difference of the compounds in blue, showing that the dimers in 4,5-DPDAF

• ) and C–H···π interactions (c); crystal structure fragments of Zn-4,5-DPDAF with π-stacking between dimers (e), their top view (f) and the layered packing of the compound depicting the voids (g). Dashed blue lines represent noncovalent interactions. The arrows indicate the orientation of

• 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

• nm (the π–π* electronic transition) accompanied by a weak band at 400–510 nm (the n–π* electronic transition). The absorption spectra of the Z-isomers comprise a blue-shifted π–π* band (250–350 nm) with a diminished molar absorption coefficient and a slightly pronounced n–π* band (350–530 nm). An

• nonplanar arrangement of the latter results in a diminished extent of conjugation, which accounts for the blue-shifted maxima (λEmax of 1b, d and f in Table 3). On the contrary, the differences in λZmax are rather minor (see Supporting Information File 1, Table S1 for ϕZ) but the longest-wavelength

• 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

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

• aliquot (10 µL) of the harvested cells was counted in a haemocytometer after the addition of 10 µL of trypan blue to determine the cell count. The remaining cells were centrifuged at 1,100 rpm for 5 min. Based on the cell count, the spun cells were resuspended in the appropriate volume of complete medium

• 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

• to count the number of viable cells after the addition of an equal volume of trypan blue. Depending on the cell count, the cell pellet in the tube was resuspended in a volume of FBS-free medium to give 450,000 cells/mL, such that each insert would contain 45,000 cells/100 µL. Assay setup An aliquot

Photoorganocatalytic trifluoromethylation of (het)arenes in green conditions

• Egor N. Boronin,
• Svetlana E. Kaurkina,
• Milena M. Svetlakova,
• Anton S. Bolshakov,
• Maxim V. Arsenyev,
• Vasilii F. Otvagin,
• Alexey Yu. Fedorov,
• Timothy Noël and
• Alexander V. Nyuchev

Beilstein J. Org. Chem. 2026, 22, 662–671, doi:10.3762/bjoc.22.50

• conditions using an inexpensive and atom-efficient CF3 source, trifluoroacetic anhydride, in ethyl acetate as a green solvent. An organic cyanoarene photocatalyst enables efficient CF3 radical generation under blue-light irradiation, providing a broad range of trifluoromethylated arenes and heteroarenes. The

• for the photochemical trifluoromethylation of (hetero)arenes using an Ir-based photocatalyst under blue-light irradiation (Scheme 1c) [16]. Although these approaches employed inexpensive CF3 sources, they relied on costly noble-metal catalysts with loadings of up to 3 mol %. Moreover, all of these

• ) under blue-light irradiation in acetonitrile (Scheme 1d) [17]. Also, photoelectrochemical trifluoromethylation procedures using trifluoroacetic acid or its salt were published recently [18][19]. Inspired by these methodologies, we sought to combine their advantages to develop a metal- and base-free

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

• of the CPC (PDB ID: 2QFA, https://doi.org/10.2210/pdb2QFA/pdb) [5] with the typical α-helix bundle from survivin (orange), borealin10–109 (green) und INCENP1–58 (blue). Ribbon model of crystal structure PDB ID 4A0J (https://doi.org/10.2210/pdb4A0J/pdb) [8] of survivin (orange) bound to the N-terminal

• lysines in the C-terminal helix of survivin (positively charged blue area). Crystal structure of the survivin dimer with complexed tweezer H3 conjugate 2a. To distinguish both survivin molecules their surfaces (light grey) have been presented with a different degree of transparency. Lysines in the

Melifoliox B, a novel phloroglucin derivative isolated from Melicope barbigera (Rutaceae) and synthesis of new oxidation products from melifoliones A and B

• Horst Weber,
• Kim-Thao Tran-Cong,
• Bernhard Mayer,
• Guido J. Reiss,
• Iryna S. Konovalova,
• Marc S. Appelhans,
• Kenneth R. Wood and
• Claus M. Passreiter

Beilstein J. Org. Chem. 2026, 22, 535–546, doi:10.3762/bjoc.22.39

• dichromate in acidic solution or with potassium permanganate in acidic or alkaline solution led to complete decomposition of the melifoliones. A solution of the melifoliones in methanol with addition of methylene blue decomposed completely into undefined products within 24 hours when exposed to sunlight and

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

• mass, indicating decomposition above this temperature (see Supporting Information File 1, Figure S3). The cycloreversion of trisquadricyclane 2f0,3 was also initiated in a ground-state reaction with magic blue (5), which has already been shown to be an effective catalyst for this reaction [46][47][48

• ]. Upon addition of magic blue (5, 7.5 mol %) to a solution of quadricyclane 2f0,3 in CDCl3, the norbornadiene 1f was formed almost quantitatively in addition to very small traces of tri(4-bromophenyl)amine, i.e., the reduced catalyst (see Supporting Information File 1, Figure S12). Discussion A

• 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 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

• 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

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

• 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

Ring contraction and ring expansion reactions in terpenoid biosynthesis and their application to total synthesis

• Nicolas Kratena,
• Nicolas Heinzig and
• Peter Gärtner

Beilstein J. Org. Chem. 2026, 22, 289–343, doi:10.3762/bjoc.22.21

• 29d (presilphiperfolan-8-yl cation), a precursor which was invoked to be involved in the biosynthesis of various sesquiterpenes. Two noteworthy examples are given here: either of the two 1,2-alkyl shifts of the cyclohexane accomplishes ring contraction. Following the blue arrow in the structure of 29d

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

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

• ·HCl in ultrapure water (blue), gave comparable diffractograms, indicating the presence of a single polymorph. Differential scanning calorimetry (DSC) showed a sharp endothermic peak corresponding to a melting point of 219.0 ± 0.1 °C (with ΔfusH = 50.4 ± 1.1 kJ/mol) for 1·HCl (Figure 4), and

• , Et3N, 4 Å molecular sieves, EtOH, rt, 1.5 h, then NaBH4, 0 °C to rt, 1.2 h, then HCl, 74%. a) Single-crystal X-ray structure of 1·HCl. Displacement ellipsoids of the nonhydrogen atoms are shown at the 50% probability level. Hydrogen atoms are shown as spheres of arbitrary size. Nitrogen atoms are blue

• , 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

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

• indigo derivatives, an increasing number of sulfonic acid groups results in greater solubility of the 6,6’-dibromoindigo derivative (e.g., 10 has greater solubility in water than 9) [25]. When dissolved in aqueous solution, both 9 and 10 yield a bright blue solution. As shown in Figure 1A, salt 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

Design and synthesis of an axially chiral platinum(II) complex and its CPL properties in PMMA matrix

• Daiki Tauchi,
• Sota Ogura,
• Misa Sakura,
• Kazunori Tsubaki and
• Masashi Hasegawa

Beilstein J. Org. Chem. 2026, 22, 143–150, doi:10.3762/bjoc.22.7

• (LL’CT) and metal-to-ligand charge transfer (MLCT) character. Photoluminescence measurements in CH2Cl2 solution revealed dual emission peaks at 427 nm and 596 nm, with a quantum yield of 3%. In PMMA matrix, the emission peaks were blue-shifted to 408 nm and 558 nm, and the quantum yield slightly

• blue-shifted by 38 nm, and the shorter-wavelength emission peak (408 nm) was blue-shifted by 19 nm. These blue shifts are attributed to the hydrophobic environment in the PMMA matrix. In such low‐polarity surroundings, the excited state is less stabilized, resulting in a higher excited‐state energy and

• thus a blue‐shifted emission. The PLQY in the PMMA matrix was 4%, comparable to that observed in solution. In the film, the emission lifetimes could be fitted with double- or triple-exponential functions, resulting in fluorescence components of 0.49 ns (50%) and 0.48 ns (50%) at 408 nm, and

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

• also showed significant color changes with increasing polarity. Color changes of 2a; from purple to blue, 2b; blue to green, and 2c; pale orange to pale pink (Figure 2d). Dyes do not show any significant emission. Chemosensor properties Cyanide selectivity study The dyes 2a–c could have the ability to

• groups is disrupted. These results strongly suggest the addition of cyanide to the vinyl bridge. Furthermore, the color of dyes 2a–c, blue, green, and pink, respectively, under ambient light changed to yellow when interacting with cyanide. The interaction mechanism was determined by 1H NMR, and the

Sustainable electrochemical synthesis of aliphatic nitro-NNO-azoxy compounds employing ammonium dinitramide and their in vitro evaluation as potential nitric oxide donors and fungicides

• Alexander S. Budnikov,
• Nikita E. Leonov,
• Michael S. Klenov,
• Andrey A. Kulikov,
• Igor B. Krylov,
• Timofey A. Kudryashev,
• Aleksandr M. Churakov,
• Alexander O. Terent’ev and
• Vladimir A. Tartakovsky

Beilstein J. Org. Chem. 2025, 21, 2739–2754, doi:10.3762/bjoc.21.211

• ]/CPCM(MeCN) level of theory (in the case of >15 conformers, 15 most stable according to GFN2-xTB were analyzed). CV-curves of 0.01 M solutions of a) 1a (blue), b) 1f (azure), c) 1c (pink), d) 1i (yellow), e) S4 (red), f) S3 (green), g) S2 (brown), and h) S1 (orange) in 0.1 M n-Bu4NBF4 solution in MeCN

• on a working glassy-carbon electrode (d = 3 mm) under a scan rate of 0.1 V/s at 298 K. CV-curves of 0.01 M solutions of a) 1a (blue), b) ADN (red), c) the mixture of 1a and ADN (green), d) 2a (pink) in 0.1 M n-Bu4NBF4 solution in MeCN on a working glassy-carbon electrode (d = 3 mm) under a scan rate