Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• substrates under 23 W CFL (compact fluorescent lamp) irradiation, affording the desired imidazole derivative 10 by utilizing DMSO as the solvent at room temperature (Scheme 4). It is worth noting that, unlike most reported intermolecular electron-transfer via an EDA complex pathway, this approach transfers

DNA with zwitterionic and negatively charged phosphate modifications: Formation of DNA triplexes, duplexes and cell uptake studies

• Yongdong Su,
• Maitsetseg Bayarjargal,
• Tracy K. Hale and
• Vyacheslav V. Filichev

Beilstein J. Org. Chem. 2021, 17, 749–761, doi:10.3762/bjoc.17.65

• synthesised possessing four or five N+ or four Ts modifications and a fluorescent label (6-FAM) at the 3ʼ-end (Table 1) was tested. Asynchronously growing NIH3T3 mouse fibroblasts were incubated with the ONs for 12 hours, fixed in 4% paraformaldehyde before the cells were processed for fluorescent confocal

Synthesis of dibenzosuberenone-based novel polycyclic π-conjugated dihydropyridazines, pyridazines and pyrroles

• Ramazan Koçak and
• Arif Daştan

Beilstein J. Org. Chem. 2021, 17, 719–729, doi:10.3762/bjoc.17.61

• classic organic dyestuffs. In that study, two highly fluorescent dibenzosuberenone-based dihydropyridazine dyes, 3a,b, were synthesized, and it was found that they can be used as a selective and sensitive sensor of fluoride anions (Scheme 1, Table 1) [55]. In another work, we reported the design

• fluorescent dyes 3a,b in detail. In the present study, the effects of functional groups with different conjugations on maximum absorbance (λmax, abs) and emission (λmax, ems), and wavelengths of dihydropyridazines 3c–f and 3k were investigated. Compounds 3c,d, with high conjugation, show the highest

Biochemistry of fluoroprolines: the prospect of making fluorine a bioelement

• Vladimir Kubyshkin,
• Rebecca Davis and
• Nediljko Budisa

Beilstein J. Org. Chem. 2021, 17, 439–460, doi:10.3762/bjoc.17.40

• intrinsically disordered proteins remains unclear. 6 Fluoroprolines in crystal structures of proteins Several high-resolution crystal structures have been reported for proteins containing fluoroprolines. In a study of enhanced green fluorescent protein from Aquorea victoria, fluoroprolines were incorporated at

• ten proline positions [117]. The incorporation of R-Flp resulted in an insoluble protein, indicating associated folding issues. In contrast, the protein containing S-Flp produced a well-structured fluorescent protein, exhibiting faster folding kinetics and producing crystals suitable for diffraction

• subdomain [129], T. thermohydrosulfuricus lipase [130][131][132], human ubiquitin [133], single-chain Fv format protein [134], KlenTag DNA polymerase [135], thioredoxin A [120], β2-microglobulin [136], red fluorescent protein [137][138], Pin1 WW domain [139], bacteriophage T4 fibritin C-terminal domain [106

1,2,3-Triazoles as leaving groups: S_NAr reactions of 2,6-bistriazolylpurines with O- and C-nucleophiles

• Dace Cīrule,
• Irina Novosjolova,
• Ērika Bizdēna and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 410–419, doi:10.3762/bjoc.17.37

• 6-O-analogues are less common [61]. Azolylpurine derivatives are important due to their potential as drug candidates. They can be used as agonists and antagonists of adenosine receptors [58][64][65][66] and against Mycobacterium tuberculosis [60]. They also show useful fluorescent properties [11][67

¹⁹F NMR as a tool in chemical biology

• Diana Gimenez,
• Aoife Phelan,
• Cormac D. Murphy and
• Steven L. Cobb

Beilstein J. Org. Chem. 2021, 17, 293–318, doi:10.3762/bjoc.17.28

Exploring the possibility of using fluorine-involved non-conjugated electron-withdrawing groups for thermally activated delayed fluorescence emitters by TD-DFT calculation

• Dongyang Chen and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2021, 17, 210–223, doi:10.3762/bjoc.17.21

• % for fluorescent compounds [1][2][3][4]. For TADF materials, a small energy gap between the lowest singlet and triplet excited states (ΔEST) is essential to permit the efficient up-conversion of triplet excitons to singlet excitons via reverse intersystem crossing (rISC) [5][6][7]. The rISC process can

Tuning the solid-state emission of liquid crystalline nitro-cyanostilbene by halogen bonding

• Subrata Nath,
• Alexander Kappelt,
• Matthias Spengler,
• Bibhisan Roy,
• Jens Voskuhl and
• Michael Giese

Beilstein J. Org. Chem. 2021, 17, 124–131, doi:10.3762/bjoc.17.13

• Subrata Nath Alexander Kappelt Matthias Spengler Bibhisan Roy Jens Voskuhl Michael Giese Organic Chemistry, University of Duisburg Essen, Universitätsstraße 7, 45141 Essen, Germany 10.3762/bjoc.17.13 Abstract The first example of halogen-bonded fluorescent liquid crystals based on the interaction

• derivatives. Therefore, tetrafluoroiodostilbene (F4St) and a series of fluoroiodoazobenzenes (F4Az, F3Az, F2Az, F2’Az) were employed as halogen bond donors and combined with nitro-cyanostilbene (NO2-Cn) as fluorescent halogen bond acceptor (see Figure 1) to form halogen-bonded liquid crystals. The series of

• -induced emission properties were combined with alkoxystilbazoles to form hydrogen-bonded mesogens. Since NO2-Cn is known to be fluorescent, we were curious how the formation of the halogen-bonded complexes affects the AIE behaviour of NO2-Cn. Therefore, we studied the photophysical properties of 1:1

Circularly polarized luminescent systems fabricated by Tröger's base derivatives through two different strategies

• Cheng Qian,
• Yuan Chen,
• Qian Zhao,
• Ming Cheng,
• Chen Lin,
• Juli Jiang and
• Leyong Wang

Beilstein J. Org. Chem. 2021, 17, 52–57, doi:10.3762/bjoc.17.6

• luminescence with glum values of +0.0021, and −0.0025, respectively. The second way to fabricate the rac-TBPP-based CPL-active material is to co-gel the fluorescent rac-TBPP with a chiral ᴅ-glutamic acid gelator DGG by co-assembly strategy. At the molar ratio of rac-TBPP/DGG = 1:80, the glum value of the co

• and applied in practice [4][5][6]. Among them, the fluorescent materials emitting circularly polarized luminescence (CPL) have attracted intensive interest owing to their wide applications in various researching fields including 3D displays, chiroptical materials, and so on [7][8][9][10]. Circular

• dichroism (CD) absorption spectra reflect the chirality of the fluorescent materials in the ground state, and circularly polarized luminescence (CPL) spectra reflect the chirality of fluorescent materials in the excited electronic state. Therefore, the CD and CPL spectrum are the two most important tools to

The fluorescence of a mercury probe based on osthol

• Guangyan Luo,
• Zhishu Zeng,
• Lin Zhang,
• Zhu Tao and
• Qianjun Zhang

Beilstein J. Org. Chem. 2021, 17, 22–27, doi:10.3762/bjoc.17.3

• electrophoresis [7]. However, the application of these analytical methods in mercury detection is limited due to the complex sample pretreatment procedures, expensive instruments, and other factors [8][9]. Fluorescent-probe instruments have been widely used due to the advantages of the simple operation, low cost

• , and high sensitivity [10][11][12]. In recent years, many fluorescent molecular probes have been reported. Because Hg2+ has a very strong quenching effect on fluorescence, most of the fluorescent molecular Hg2+ probes are of the fluorescence-quenching type and are easily interfered with by other

• probe [23], OST as a probe for the detection of mercury has not been reported. In this paper, OST was used as a fluorescent probe since the fluorescence intensity of OST at 406 nm increased significantly when Hg2+ was added. The probe had a high selectivity and sensitivity for Hg2+ recognition and can

Metal-free synthesis of biarenes via photoextrusion in di(tri)aryl phosphates

• Hisham Qrareya,
• Lorenzo Meazza,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 3008–3014, doi:10.3762/bjoc.16.250

• phosphates examined were barely fluorescent in methanol, with an emission quantum yield (Φem) in the 0.005–0.06 range (see Table 2 and Supporting Information File 1 for further details). We thus focused on compounds 1e, 1h, 3a and 3c as the model substrates. In the case of compounds 1e and 1h, we observed

Selected peptide-based fluorescent probes for biological applications

• Debabrata Maity

Beilstein J. Org. Chem. 2020, 16, 2971–2982, doi:10.3762/bjoc.16.247

• fluorescence techniques have attracted immense interest. Synthetic peptide-based fluorescent probes are advantageous over protein-based sensors, since they are synthetically accessible, more stable, and can be easily modified in a site-specific manner for selective biological applications. Peptide receptors

• labeled with environmentally sensitive/FRET fluorophores have allowed direct detection/monitoring of biomolecules in aqueous media and in live cells. In this review, key peptide-based approaches for different biological applications are presented. Keywords: fluorescent probe; fluorophores; molecular

• organic fluorophore (reporter) with a specific peptide sequence is the common approach for designing peptide-based fluorescent probes [16]. Fluorophores on peptidic arms perform as reporter during the interaction with biomolecules [17][18]. The interaction with biomolecules will alter the fluorescence

Incorporation of a metal-mediated base pair into an ATP aptamer – using silver(I) ions to modulate aptamer function

• Marius H. Heddinga and
• Jens Müller

Beilstein J. Org. Chem. 2020, 16, 2870–2879, doi:10.3762/bjoc.16.236

• present. System B functions in a similar manner (Figure 4B), but instead of the aptamer carrying the fluorescent label, it utilizes two complementary sequences, one carrying fluorescein (2f) and the other carrying DABCYL (2q). First, the change in fluorescence was investigated for all sequences of the

• , Figure S7b). This strongly suggests that the modified aptamers are still specific. The binding assays were repeated using the respective aptamers lacking the fluorescein label (1a, 1b, 1c, and 1d; Figure S8 in Supporting Information File 1). Without the fluorescent marker, a quantification of the eluted

Synthesis and investigation of quadruplex-DNA-binding, 9-O-substituted berberine derivatives

• Jonas Becher,
• Daria V. Berdnikova,
• Heiko Ihmels and
• Christopher Stremmel

Beilstein J. Org. Chem. 2020, 16, 2795–2806, doi:10.3762/bjoc.16.230

• derivatives. Notably, a clear relationship between the binding affinity of the ligands with the length of the alkyl linker chain, n, was not observed. However, depending on the structure, the ligands exhibited different effects when bound to the G4-DNA, such as fluorescent light-up effects and formation of

• bound to the G4-DNA, such as fluorescent light-up effects and the formation of ICD bands, which are mostly pronounced with linker length of n = 4 (with a2) and n = 5 (with 22AG). This significant influence of the complex structure on the optical properties of the ligand provides some evidence that each

Encrypting messages with artificial bacterial receptors

• Pragati Kishore Prasad,
• Naama Lahav-Mankovski,
• Leila Motiei and
• David Margulies

Beilstein J. Org. Chem. 2020, 16, 2749–2756, doi:10.3762/bjoc.16.225

• information protection at the molecular level. Keywords: artificial receptors; cell surface modification; fluorescent probes; molecular cryptography; Introduction In living cells, information is processed and transferred via a series of recognition and signaling events, which normally begin by the binding

• selectively bind a hexa-histidine tag (His-tag). ODN-1 can also be modified with a second functional group (X), such as a fluorescent dye, to afford X-ODN-1 (Figure 1A and Figure 1B). In this way, the binding of X-ODN-1 to the bacteria will lead to the presentation of X on the cell surface (Figure 1A). A

• labeled bacteria during cell division (Figure 2B). Another research direction in our group, which also involves the development of unconventional fluorescent probes, is the information protection at the molecular level [4][5][6]. In such studies [4][5][6], the emission patterns generated by the probes are

Enzyme-instructed morphological transition of the supramolecular assemblies of branched peptides

• Dongsik Yang,
• Hongjian He and
• Bing Xu

Beilstein J. Org. Chem. 2020, 16, 2709–2718, doi:10.3762/bjoc.16.221

• nanofibers in the HeLa cells. Then, we used confocal laser scanning microscopy (CLSM) to examine whether these compounds deliver RPE into HeLa cells. After mixing R-phycoerythrin (RPE) [49], a red fluorescent protein, with 1 or 2 at different concentrations, we incubated the mixtures with HeLa cells for 2 h

• and 4 h. While the control cells (without adding 1 or 2) showed little fluorescence, the cells treated with RPE and 1 or 2 started to show many red fluorescent puncta inside the cells after 2 h. The puncta remained inside the cells at 4 h and showed little change (Figure 6). These results indicate

Dawn of a new era in industrial photochemistry: the scale-up of micro- and mesostructured photoreactors

• Emine Kayahan,
• Mathias Jacobs,
• Leen Braeken,
• Leen C.J. Thomassen,
• Simon Kuhn,
• Tom van Gerven and
• M. Enis Leblebici

Beilstein J. Org. Chem. 2020, 16, 2484–2504, doi:10.3762/bjoc.16.202

Styryl-based new organic chromophores bearing free amino and azomethine groups: synthesis, photophysical, NLO, and thermal properties

• Anka Utama Putra,
• Deniz Çakmaz,
• Nurgül Seferoğlu,
• Alberto Barsella and
• Zeynel Seferoğlu

Beilstein J. Org. Chem. 2020, 16, 2282–2296, doi:10.3762/bjoc.16.189

• /deprotonation processes [23][24][25]. Fluorescent dyes as chemosensors offer unique merits such as low energy consumption, ease of handling, high selectivity, and notable sensitivity [26][27]. Moreover, some fluorescent dyes demonstrate remarkable ICT characteristics, and could therefore serve as NLO dyes [11

• ][12][13][14]. Among dyestuffs classes, the push-pull fluorescent dyes are renowned to own such special behaviors. The push-pull dyes generate higher charge delocalization upon excitation, thus enhance both polarizability and fluorescence emission [12][13][14][18]. The charge delocalization upon

• maximum emission wavelengths with increasing polarity parameters of the solvents. However, the largest bathochromic shifts of the emission maxima for both series of dyes were observed in DMSO. This phenomenon is observed when highly fluorescent polar excited states of push-pull dyes are stabilized by

The B & B approach: Ball-milling conjugation of dextran with phenylboronic acid (PBA)-functionalized BODIPY

• Patrizia Andreozzi,
• Lorenza Tamberi,
• Elisamaria Tasca,
• Gina Elena Giacomazzo,
• Marta Martinez,
• Mirko Severi,
• Marco Marradi,
• Stefano Cicchi,
• Sergio Moya,
• Giacomo Biagiotti and
• Barbara Richichi

Beilstein J. Org. Chem. 2020, 16, 2272–2281, doi:10.3762/bjoc.16.188

• , Poland 10.3762/bjoc.16.188 Abstract Mechanochemistry is an emerging and reliable alternative to conventional solution (batch) synthesis of complex molecules under green and solvent-free conditions. In this regard, we report here on the conjugation of a dextran polysaccharide with a fluorescent probe, a

• biocompatibility while remaining fluorescent. Keywords: ball milling; boronic ester; dextran; bodipy; nanoparticles; Introduction In the last few decades, mechanochemistry has gathered a great deal of attention and a lot of efforts have been focused on its use in organic synthesis, catalysis, biotransformation

• the mechanochemical approach (the B & B, ball milling for boronic acid conjugation) as bioconjugation strategy for the labeling of biocompatible carbohydrates. Fluorescent labeling is of key importance to follow up the fate of molecules and (nano)materials inside cells and in the human body. In this

Tools for generating and analyzing glycan microarray data

• Akul Y. Mehta,
• Jamie Heimburg-Molinaro and
• Richard D. Cummings

Beilstein J. Org. Chem. 2020, 16, 2260–2271, doi:10.3762/bjoc.16.187

• the primary analyte was not fluorescently labeled, for example a fluorescent secondary antibody or streptavidin. After washing the slide to remove unbound material, the bound material is then identified and measured by scanning using a fluorescence microarray scanner. The image produced can then be

Naphthalene diimide bis-guanidinio-carbonyl-pyrrole as a pH-switchable threading DNA intercalator

• Poulami Jana,
• Filip Šupljika,
• Carsten Schmuck and
• Ivo Piantanida

Beilstein J. Org. Chem. 2020, 16, 2201–2211, doi:10.3762/bjoc.16.185

• -fluorescent at experimental conditions and addition. Since NDI dyes are known to emit fluorescence, we also tried fluorimetric titrations with the hope that the initially non-emissive compound 4 becomes fluorescent upon binding to DNA (for instance cyanine dyes and many other behave that way). However, we did

• not observe any emission, neither for single dye binding to DNA, nor in crowding conditions (excess of dye over DNA binding sites) at which eventually fluorescent excimers could be formed. Interactions with DNA/RNA Because of significant differences in the protonation states of compound 4, studies

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

• -light irradiation by a household (19 W) compact fluorescent light (CFL) bulb (emitting variable wavelengths in the range of ≈365–625 nm) [195] and under mild conditions. Control reactions revealed that both the PS and light were essential for the reaction to occur. According to their report, benzylic C

Clustering and curation of electropherograms: an efficient method for analyzing large cohorts of capillary electrophoresis glycomic profiles for bioprocessing operations

• Ian Walsh,
• Matthew S. F. Choo,
• Sim Lyn Chiin,
• Amelia Mak,
• Shi Jie Tay,
• Pauline M. Rudd,
• Yang Yuansheng,
• Andre Choo,
• Ho Ying Swan and
• Terry Nguyen-Khuong

Beilstein J. Org. Chem. 2020, 16, 2087–2099, doi:10.3762/bjoc.16.176

• bracketing standards in the electropherograms, the variation of GU values for glycan peaks generally were within a very small range (Figure 1A and 1B) allowing for consistent database matching against a GU CE database (APTS fluorescent labelled) [10]. HappyTools was used to calibrate the migration times of

• needed to identify what glycans were eluted at each peak. Glycan identification for all 11 bioreactor runs Glycan identifications to all peaks in all 391 electropherograms were confirmed using evidence from two orthogonal approaches, UPLC-MS (RFMS fluorescent label) analysis and a CE-LIF analysis (APTS

• Capillary electrophoresis of the released and APTS-labelled antibody N-glycans was performed on a CESI8000 CE instrument (Sciex) equipped with a solid state laser-induced fluorescent detector (excitation 488 nm, emission 520 nm). Separations were made across a 20 cm effective length (30 cm total length), 50

Naphthalene diimide–amino acid conjugates as novel fluorimetric and CD probes for differentiation between ds-DNA and ds-RNA

• Annike Weißenstein,
• Myroslav O. Vysotsky,
• Ivo Piantanida and
• Frank Würthner

Beilstein J. Org. Chem. 2020, 16, 2032–2045, doi:10.3762/bjoc.16.170

• Chemistry (CNC), Universität Würzburg, Theodor-Boveri-Weg, 97074 Würzburg, Germany 10.3762/bjoc.16.170 Abstract Two novel unnatural amino acids, prepared by linking a dicationic purple-coloured and fluorescent naphthalene diimide (NDI) at core position to amino acid side chains of variable length, strongly

• colourless and non-fluorescent core-unsubstituted NDI with a new charge transfer band with an absorption maximum in the visible spectral range and a high fluorescence quantum yield (up to 58%) [23][25]. Further, the 2-amino substituent offers the possibility to connect various amino acid side chains, thus

• –polynucleotide systems, thereby providing insight into the aromatic core position within the intercalative binding site. Conclusion The new amino acid conjugates 3a, 3b, and reference compound 5 bearing the fluorescent NDI tag molecules showed moderate absorbance in the mid-visible range (λabs 520–540 nm) and

pH- and concentration-dependent supramolecular self-assembly of a naturally occurring octapeptide

• Goutam Ghosh and
• Gustavo Fernández

Beilstein J. Org. Chem. 2020, 16, 2017–2025, doi:10.3762/bjoc.16.168

• ]. The band at 1678 cm−1 was the characteristic feature of an antiparallel conformation of the sheet structure or the β-turn structure [61]. To further confirm the β-sheet formation, we performed a ThT fluorescence spectroscopy assay. ThT is a widely used fluorescent dye that is amyloid-specific and can