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

• binds free tryptophan selectively in aqueous media. Furthermore, it is capable of binding to tryptophan within model tripeptides. The naphthalene functionality in the glucose-derived receptor enables the study of guest binding using fluorescence spectroscopy. Keywords: amino acids; macrocyclic

• in water [21]. Crown ether 1 is particularly suited for the sensing of Trp methyl ester, which it binds with a higher affinity than the Phe and Tyr esters. Additionally, the binding of Trp-OMe results in a highly efficient fluorescence quenching of the naphthalene unit in the receptor. Herein, we

• acids in H2O by 1 was investigated by ITC measurements and titration experiments monitored by fluorescence spectroscopy. The results are summarized in Table 1. Receptor 1 binds tryptophan with the highest affinity among the investigated amino acids (entry 1, Table 1). The Ka of the complex between 1 and

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

• photostability compared to ANTH and 9,10-ANTH derivatives, and a simple synthetic access makes it an attractive material as a deep-blue OLED emitter and an efficient fluorescent probe. Keywords: anthracene; dibromoanthracene; electron poor polyaromatic systems; fluorescence; perfluoroalkylation

• to suppress undesirable fluorescence self-quenching [15]. Not only do bulky substituents disrupt intermolecular interactions of this type, they can also provide higher chemical stability and reduce or prevent the photodimerization and photo-oxidation to which all acenes are prone [13]. Furthermore

• because isolated electronically excited molecules are more likely to undergo fluorescence instead of non-radiative relaxation, as discussed in some literature [13]. At the same time, it should be noted that emission properties in the crystalline phase and amorphous films, which are often used in OLED

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

• promising strategy for synthesizing substituted cyclobutanes without the need for ultraviolet irradiation. Keywords: bimane; [2 + 2] cycloaddition; fluorescence; topochemical polymerization; X-ray crystallography; Introduction Topochemical polymerizations refer to polymerization reactions occurring in the

• "bimanes" is derived from the Latin ‘bi’ (two) and ‘manus’ (hand). syn-Bimanes are often characterized by high fluorescence quantum yields, ranging from 60% to 100% [17], while anti-isomers typically exhibit phosphorescence [18]. Figure 1b illustrates the two isomers along with their simplified naming

• ¹H NMR spectra remained unchanged compared to the neat compounds (Figures S1, S3, and S5, Supporting Information File 1), confirming that the reaction occurs selectively in the solid state. Cl2B was also irradiated in DCM with the same 405 nm LEDs, in a quartz fluorescence cuvette. A UV–vis spectrum

Synthesis, structure, ionochromic and cytotoxic properties of new 2-(indolin-2-yl)-1,3-tropolones

• Yurii A. Sayapin,
• Eugeny A. Gusakov,
• Inna O. Tupaeva,
• Alexander D. Dubonosov,
• Igor V. Dorogan,
• Valery V. Tkachev,
• Anna S. Goncharova,
• Gennady V. Shilov,
• Natalia S. Kuznetsova,
• Svetlana Y. Filippova,
• Tatyana A. Krasnikova,
• Yanis A. Boumber,
• Alexey Y. Maksimov,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2025, 21, 358–368, doi:10.3762/bjoc.21.26

• -(1,1-Dimethyl-1H-benzo[e]indolin-2-yl)-5,6,7-trichloro-1,3-tropolone exhibited high in vitro cytotoxic activity against A431 skin cancer and H1299 lung cancer cell lines. Keywords: cytotoxic activity; fluorescence; o-chloranil; quantum chemical DFT calculations; 1,3-tropolones; X-ray diffraction

• (0.84) Å, H···O = 1.79 (1.83) Å, and N···O = 2.513 (2.518) Å, angle N–H–O 140.4° (138.0°). The electronic absorption spectra of compounds 7a,b and 8a,b in acetonitrile have long wavelength bands in the region of 425–432 nm (Table 2). They exhibit dual-maxima fluorescence at 476–530 nm with normal and

• -n-butylammonium salts (TBAX: F, Cl, Br, I, CN). Exclusively cyanide and fluoride anions lead to a naked-eye effect due to a change of the solution’s colour from yellow-orange to pale yellow (Figure 5). At the same time, a new fluorescence band appears at 420–440 nm. The Stokes shifts of fluorescence

Red light excitation: illuminating photocatalysis in a new spectrum

• Lucas Fortier,
• Corentin Lefebvre and
• Norbert Hoffmann

Beilstein J. Org. Chem. 2025, 21, 296–326, doi:10.3762/bjoc.21.22

• unsaturated ring structure derived from squaric acid [47], has attracted attention due to its ability to promote single-electron transfer [48]. These compounds exhibit significant NIR fluorescence, making them valuable in applications such as biomolecule probing. Additionally, squaraine derivatives are well

Synthesis and characterizations of highly luminescent 5-isopropoxybenzo[rst]pentaphene

• Islam S. Marae,
• Jingyun Tan,
• Rengo Yoshioka,
• Zakaria Ziadi,
• Eugene Khaskin,
• Serhii Vasylevskyi,
• Ryota Kabe,
• Xiushang Xu and
• Akimitsu Narita

Beilstein J. Org. Chem. 2025, 21, 270–276, doi:10.3762/bjoc.21.19

• properties were investigated by UV–vis absorption and fluorescence spectroscopy in compassion to pristine BPP and its oxidation product, benzo[rst]pentaphene-5,8-dione (BPP-dione). BPP-OiPr exhibited a significantly enhanced photoluminescence quantum yield (PLQY), reaching 73% in comparison to pristine BPP

• micrometers, as demonstrated by SEM. These results provide not only an easy access to highly emissive BPP derivatives with potential as organic fluorescent materials, but also an insight to design derivatives of other PAHs with enhanced fluorescence and charge transfer character. Single crystal structure of

Effect of substitution position of aryl groups on the thermal back reactivity of aza-diarylethene photoswitches and prediction by density functional theory

• Misato Suganuma,
• Daichi Kitagawa,
• Shota Hamatani and
• Seiya Kobatake

Beilstein J. Org. Chem. 2025, 21, 242–252, doi:10.3762/bjoc.21.16

• Molecular photoswitches have been studied for a long time because their physicochemical properties such as refractive index [1][2], dipole moment [3][4], conductivity [5][6], magnetism [7][8], and fluorescence [9][10][11] can be spatiotemporally modulated by light without physical contact. Therefore

Streamlined modular synthesis of saframycin substructure via copper-catalyzed three-component assembly and gold-promoted 6-endo cyclization

• Asahi Kanno,
• Ryo Tanifuji,
• Satoshi Yoshida,
• Sota Sato,
• Saori Maki-Yonekura,
• Kiyofumi Takaba,
• Jungmin Kang,
• Kensuke Tono,
• Koji Yonekura and
• Hiroki Oguri

Beilstein J. Org. Chem. 2025, 21, 226–233, doi:10.3762/bjoc.21.14

• degassed solvent and light-shielding flask, the oxidative conversion of 12 to the imidate 18 proceeded smoothly. Notably, the transient intermediate 18, exhibiting a sky-blue fluorescence, further underwent a ring opening to afford the tetracyclic 14 with the simultaneous regeneration of both a nitrile and

Heteroannulations of cyanoacetamide-based MCR scaffolds utilizing formamide

• Marios Zingiridis,
• Danae Papachristodoulou,
• Despoina Menegaki,
• Konstantinos G. Froudas and
• Constantinos G. Neochoritis

Beilstein J. Org. Chem. 2025, 21, 217–225, doi:10.3762/bjoc.21.13

• , showing similar profiles across all the different scaffolds (Figure 2 and Supporting Information File 1). The compounds 5–7 exhibited a maximum absorbance (λmax) at 330 nm, 284 nm and 310 nm, respectively, which also corresponded to their excitation wavelength (λex). Upon excitation, fluorescence emission

• pyrimidine scaffold. Representative fluorescence spectrum of compounds 5b (λex = 330 nm) and 6e (λex = 430 nm) at 0.2 M in DMSO. Molecular geometry observed within the crystal structure of compound 7b (CCDC 2376493). Strategies towards targeted adducts: A) Niementowski quinazoline synthesis utilizing

• materials. The colored frames indicate the different scaffold types. Synthesis of N-substituted thienopyrimidones 5a–e by a Gewald three-component reaction employing 2-aminothiophenes 2a–e and formamide as C1 source. A characteristic fluorescence for compound 5a was reported (365 nm in DMSO). The reported

Hot shape transformation: the role of PSar dehydration in stomatocyte morphogenesis

• Remi Peters,
• Levy A. Charleston,
• Karinan van Eck,
• Teun van Berlo and
• Daniela A. Wilson

Beilstein J. Org. Chem. 2025, 21, 47–54, doi:10.3762/bjoc.21.5

• decreased slightly during the heating cycle, indicative of membrane dehydration (Figure 3c). Further proof for the changing membrane properties was shown by a fluorescence measurement of pyrene-PEG-OH in the presence of the PSar-PBLG vesicles. Pyrene is well-known for its sensitivity to environmental

• the PSar corona in which the pyrene resided. This change shifted the ratio between I1/I3 of pyrenes fluorescence, going down from 1.50 to 1.31 (Figure 3b). This is a clear indication of the environment of the pyrene probe becoming more hydrophobic. The information obtained from DSC, accompanied by the

Synthesis, characterization, and photophysical properties of novel 9‑phenyl-9-phosphafluorene oxide derivatives

• Shuxian Qiu,
• Duan Dong,
• Jiahui Li,
• Huiting Wen,
• Jinpeng Li,
• Yu Yang,
• Shengxian Zhai and
• Xingyuan Gao

Beilstein J. Org. Chem. 2024, 20, 3299–3305, doi:10.3762/bjoc.20.274

• ]. Compared to the traditional PO-containing moieties, PhFlOP possesses an enhanced rigid structure to reduce the possibility of nonradiative decay processes, which would improve optoelectronic properties [17][27]. Thermally activated delayed fluorescence (TADF) materials and devices have emerged rapidly in

Efficient synthesis of fluorinated triphenylenes with enhanced arene–perfluoroarene interactions in columnar mesophases

• Yang Chen,
• Jiao He,
• Hang Lin,
• Hai-Feng Wang,
• Ping Hu,
• Bi-Qin Wang,
• Ke-Qing Zhao and
• Bertrand Donnio

Beilstein J. Org. Chem. 2024, 20, 3263–3273, doi:10.3762/bjoc.20.270

• fluorescence emission spectroscopies reveal green photoluminescence with fluorescence quantum yields of up to 33% for the Fn derivatives. The J-aggregation for the inner fluorine-substituted dimers Gnm is energetically and stereoelectronically more favorable and G66 exhibits thin-film fluorescence with a large

• . Photophysical properties: UV–vis absorption and photoluminescence UV–vis absorption and fluorescence spectra of the synthesized fluorine polycyclic aromatic hydrocarbons Fn and Gnm were measured in solution (in various solvents) and thin film and the results are summarized in Figure 6 and Table S7 in Supporting

• (λem = 402 nm for PH8) and 460–500 nm for G66, with absolute quantum yields of 30% and 32%, respectively. Further, their fluorescence spectra in solutions show some solvent polarity influence, with a substantial red shift as the solvent polarity is increased. In thin film, the single luminescence

Discovery of ianthelliformisamines D–G from the sponge Suberea ianthelliformis and the total synthesis of ianthelliformisamine D

• Sasha Hayes,
• Yaoying Lu,
• Bernd H. A. Rehm and
• Rohan A. Davis

Beilstein J. Org. Chem. 2024, 20, 3205–3214, doi:10.3762/bjoc.20.266

• cultures were withdrawn, and the plates were washed twice with sterile water. Then, 50 µL of diluted RSZ solution (0.2% w/v) in LB medium was added into each well followed by incubation at 37 °C for 5 h. A microplate reader (iD5 Multi-Mode) was used to measure the fluorescence intensity (excitation 530 nm

Multicomponent reactions driving the discovery and optimization of agents targeting central nervous system pathologies

• Lucía Campos-Prieto,
• Aitor García-Rey,
• Eddy Sotelo and
• Ana Mallo-Abreu

Beilstein J. Org. Chem. 2024, 20, 3151–3173, doi:10.3762/bjoc.20.261

• carboxylic building block. The obtained molecules were evaluated for their ability to inhibit β-amyloid aggregation by the interaction with two β‐amyloid peptides, Aβ1‐42 and AβpE3‐42. The aggregation inhibition experiment, which measures the decrease of fluorescence, was carried out with the thioflavin T

• methodology highlighting compounds 4a (Aβ1‐42 = 65% and AβpE3-42 = 53% of fluorescence) and 4b (Aβ1‐42 = 50% and AβpE3‐42 = 90% of fluorescence) from the first publication and compound 4c (Aβ1‐42 = 74% and AβpE3‐42 = 51% of fluorescence) from the second one (Figure 6). The latter was able to slightly improve

• conducted at a concentration of 10 μM, with donepezil serving as a positive control. To measure their impact on cellular tau oligomerization, the fluorescence resonance energy transfer (FRET) signal intensity was quantified in a cellular tau FRET assay at the same 10 μM concentration, using MK-886, a known

Cyclodextrin-based rotaxanes for polymer materials: challenge on simultaneous realization of inexpensive production and defined structures

• Yosuke Akae

Beilstein J. Org. Chem. 2024, 20, 3026–3049, doi:10.3762/bjoc.20.252

• ratio. Namely, the inclusion of CD prevented the aggregate formation of the conjugative polymer backbone, which usually induces a change in the absorption wavelength. Similarly, in fluorescence spectroscopy, the restriction of the nonradiative deactivation was caused by the inclusion structure

• , increasing the fluorescence intensity. This system could be described as an example in which the nature of the CD having a thickness along the cavity was effectively used on the polyrotaxane structure to improve the polymer properties. The same results would not be observed when wheel components having a

• crosslinking moiety, resulting in the de-crosslinking of the entire network structure without damaging the trunk polymer backbone. Furthermore, when the fluorescence active moiety was integrated with the dumbbell structure, this de-crosslinking process was monitored by the time-course change of the

Tunable full-color dual-state (solution and solid) emission of push–pull molecules containing the 1-pyrindane moiety

• Anastasia I. Ershova,
• Sergey V. Fedoseev,
• Konstantin V. Lipin,
• Mikhail Yu. Ievlev,
• Oleg E. Nasakin and
• Oleg V. Ershov

Beilstein J. Org. Chem. 2024, 20, 3016–3025, doi:10.3762/bjoc.20.251

• solid state). Emission maxima ranged from 469 to 721 nm in solution depending on the solvent and type of donor substituent, and from 493 to 767 nm in the solid state. For the arylidene derivative of pyrindane with a dimethylamino group, it was shown that fluorescence can be changed by the action of an

• , full-color fluorescence of organic molecules is achieved by extending π-conjugated systems or by introducing combinations of donor and acceptor groups, which changes the electronic properties and consequently the emission spectra [35][36][37][38][39][40][41][42][43][44]. This approach is synthetically

• challenging since it requires optimization of the reaction conditions for each modification step of the conjugated system. In this work, full-color fluorescence has been achieved solely by changing the donor groups, while the conjugated system and the multiacceptor part of the molecule were left unchanged

Recent advances in transition-metal-free arylation reactions involving hypervalent iodine salts

• Ritu Mamgain,
• Kokila Sakthivel and
• Fateh V. Singh

Beilstein J. Org. Chem. 2024, 20, 2891–2920, doi:10.3762/bjoc.20.243

• sulfonylation was confirmed as no product was found when carrying out the reaction in the presence of radical scavengers. Stern–Volmer studies indicated a significant fluorescence emission quenching of methylene blue by DIPEA, suggesting a reductive quenching of methylene blue during the reaction. Experiments

Synthesis of pyrrole-fused dibenzoxazepine/dibenzothiazepine/triazolobenzodiazepine derivatives via isocyanide-based multicomponent reactions

• Marzieh Norouzi,
• Mohammad Taghi Nazeri,
• Ahmad Shaabani and
• Behrouz Notash

Beilstein J. Org. Chem. 2024, 20, 2870–2882, doi:10.3762/bjoc.20.241

• , and triazolobenzodiazepine under solvent- and catalyst-free conditions. Purposefully, this approach produced various bioactive scaffolds using environmentally friendly, mild, and simple conditions. Due to their bioactive moieties, these compounds with exclusive fluorescence properties may attract

Investigation of a bimetallic terbium(III)/copper(II) chemosensor for the detection of aqueous hydrogen sulfide

• Parvathy Mini,
• Michael R. Grace,
• Genevieve H. Dennison and
• Kellie L. Tuck

Beilstein J. Org. Chem. 2024, 20, 2818–2826, doi:10.3762/bjoc.20.237

• eliminating short-lived background fluorescence. This unique capability enhances the sensitivity and reliability of trivalent lanthanide-based chemosensors, making them invaluable tools for our application in the detection of hydrogen sulfide. Our previously reported trivalent lanthanide-based chemosensors

• were measured at room temperature utilizing a Varian Cary 1E UV–vis spectrophotometer with a quartz cell of 10 mm path length. Luminescence emission spectra of aqueous solutions were captured at 23 °C using a Varian Cary-Eclipse fluorescence spectrophotometer set to phosphorescence mode, employing a

• Information Supporting Information File 16: Copies of HRMS, 1H NMR and fluorescence emission spectra. Acknowledgements The authors acknowledge the support of the School of Chemistry, Monash University and the Australian Department of Defence and Defence Science and Technology Group.

Access to optically active tetrafluoroethylenated amines based on [1,3]-proton shift reaction

• Yuta Kabumoto,
• Eiichiro Yoshimoto,
• Bing Xiaohuan,
• Masato Morita,
• Motohiro Yasui,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2024, 20, 2776–2783, doi:10.3762/bjoc.20.233

•  1a, 1, 2) [10][11][12], liquid crystals (Figure 1b, 3, 4) [13][14][15][16][17], fluorescence materials (Figure 1c, 5) [18][19], and so on, have been developed in recent years. In sharp contrast to the major development of such non-chiral tetrafluoroethylenated compounds, there have been only few

Interaction of a pyrene derivative with cationic [60]fullerene in phospholipid membranes and its effects on photodynamic actions

• Hayato Takagi,
• Çetin Çelik,
• Ryosuke Fukuda,
• Qi Guo,
• Tomohiro Higashino,
• Hiroshi Imahori,
• Yoko Yamakoshi and
• Tatsuya Murakami

Beilstein J. Org. Chem. 2024, 20, 2732–2738, doi:10.3762/bjoc.20.231

• physiologically relevant media [15]. The interaction between catC60 and PyBA in the liposomes was assessed by the fluorescence spectra of PyBA in catC60-lip [16]. The catC60-lip containing catC60 at 0, 5.4, and 54 µM were mixed with PyBA (50 µM) in PBS(–), and the fluorescence spectra were measured. As shown in

• Figure 4a, the intensity decreased upon increasing the concentration of the catC60 in the liposomes, showing the quench of PyBA fluorescence by catC60, presumably by interacting in the liposome membrane. The incomplete quenching after the addition of PyBA at a concentration comparable to that of catC60

• may be attributed to the presence of unembedded PyBA in the dispersion. To this PyBA-embedded catC60-lip system, methanol was added to completely destroy the liposome structures, resulting in the regain of the fluorescence intensity (Figure 4b). The results clearly demonstrate that PyBA interacts with

Synthesis of benzo[f]quinazoline-1,3(2H,4H)-diones

• Ruben Manuel Figueira de Abreu,
• Peter Ehlers and
• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 2708–2719, doi:10.3762/bjoc.20.228

• was studied by UV–vis and fluorescence spectroscopy. Keywords: cross-coupling; cyclization; heterocycles; palladium; Introduction Nucleobases contain the coded information and give DNA and RNA their typical structure. As a nucleobase, uracil is involved in numerous vital processes and is therefore a

• -based benzo[f]quinazoline-1,3(2H,4H)-diones C [65]. Furthermore, optical properties were analysed by UV–vis and fluorescence spectroscopy. Results and Discussion Synthesis Our strategy for the synthesis of benzo[f]quinazoline-1,3(2H,4H)-diones is based on a four-step sequence and relies on a combination

• properties All synthesized compounds exhibit photoluminescence by excitation with UV light. Hence, we studied the photophysical properties of all obtained derivatives 5 by steady-state absorption and fluorescence spectroscopy. The influence of the substitution pattern on the photophysical properties is

5th International Symposium on Synthesis and Catalysis (ISySyCat2023)

• Anthony J. Burke and
• Elisabete P. Carreiro

Beilstein J. Org. Chem. 2024, 20, 2704–2707, doi:10.3762/bjoc.20.227

• fluorescence quantum yield, which is an important property for their potential application in the field of optoelectronics (particularly for energy and biological chemistry applications). In this thematic issue, Nieto et al. contributed a timely Review article on the chemical space of 2-phenethylamines

Photoluminescence color-tuning with polymer-dispersed fluorescent films containing two fluorinated diphenylacetylene-type fluorophores

• Kazuki Kobayashi,
• Shigeyuki Yamada,
• Motohiro Yasui and
• Tsutomu Konno

Beilstein J. Org. Chem. 2024, 20, 2682–2690, doi:10.3762/bjoc.20.225

• luminescent materials, particularly after the 2001 discovery of aggregation-induced emission. This study focuses on fluorinated diphenylacetylene-based luminescent molecules, revealing that specific molecular modifications can enhance fluorescence and achieve a wide range of photoluminescence colors. A simple

• diphenylacetylene structure as the π-conjugated core. As a part of our research projects, we have begun to explore diphenylacetylene-based luminescent molecules despite diphenylacetylene not exhibiting fluorescence at room temperature because it undergoes a πσ* excited state that rapidly forms a trans-bend

• short-axis direction of the electron-deficient aromatic ring significantly retards the internal conversion via the formation of H···F hydrogen bonds, leading to a marked blue fluorescence in the crystalline state (Figure 1b) [17][18][19][20]. Recently, the introduction of N,N-disubstituted amino groups

Applications of microscopy and small angle scattering techniques for the characterisation of supramolecular gels

• Connor R. M. MacDonald and
• Emily R. Draper

Beilstein J. Org. Chem. 2024, 20, 2608–2634, doi:10.3762/bjoc.20.220

• structures. Some of the key features and capabilities of these techniques are summarised in Table 1. CLSM is a fluorescence microscopy technique capable of acquiring high-resolution optical images at selected depths of the sample. This is achieved by exciting compounds with laser light and, by using a

• pinhole to select focal planes, allows fluorescence at various depths to be focused and imaged. The resulting 2D focal plane images can be stacked to yield a 3D fluorescence image of high resolution, allowing complex morphologies to be visualised (Figure 2) [11]. While CLSM provides in situ 3D imaging

• attached to the molecules themselves or is interacting with them. Introducing fluorescent dyes to self-assembling systems affects their chemical and mechanical stability as the hydrophobic features can destabilise the self-assembled network [18]. This reliance on fluorescence labels or dyes leading to a