Mesoionic tetrazolium-5-aminides: Synthesis, molecular and crystal structures, UV–vis spectra, and DFT calculations

• Vladislav A. Budevich,
• Sergei V. Voitekhovich,
• Alexander V. Zuraev,
• Vadim E. Matulis,
• Vitaly E. Matulis,
• Alexander S. Lyakhov,
• Ludmila S. Ivashkevich and
• Oleg A. Ivashkevich

Beilstein J. Org. Chem. 2021, 17, 385–395, doi:10.3762/bjoc.17.34

• strong blue shift, observed in methanol and water solution. So, in the ground state, the N5 atom of 8a has a large negative charge (Figure 5) and strongly interacts with polar solvents. Therefore, polar solvents significantly decrease the ground state energy. When the excited state emerges, the strong CT

• energy of S0→S1 transition increases, and a blue shift is observed in polar media. Conclusion Mesoionic tetrazolium-5-aminides can be easily prepared by the alkylation of readily available 5-aminotetrazole and its N-alkyl derivatives in a t-BuOH/HClO4 system followed by the treatment of the tetrazolium

• ) and MESP contour map (right) for the molecule of 8a. The calculated plots in n-hexane of a) HOMO, b) LUMO, c) electron density difference between the S1 and S0 states, and d) the S0→S1 CT. Green (blue) regions (for c and d) indicate an increase (decrease) in the electron density upon the electronic

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

Regioselective chemoenzymatic syntheses of ferulate conjugates as chromogenic substrates for feruloyl esterases

• Olga Gherbovet,
• Fernando Ferreira,
• Apolline Clément,
• Mélanie Ragon,
• Julien Durand,
• Sophie Bozonnet,
• Michael J. O'Donohue and
• Régis Fauré

Beilstein J. Org. Chem. 2021, 17, 325–333, doi:10.3762/bjoc.17.30

• ] and (ii) spontaneous oxidation and subsequent dimerization forming the insoluble blue 5-bromo-4-chloro-substituted indigo dye [15]. In an alternative demonstration, 1a was also used for colony level detection of FAE using yeast cells (Yarrowia lipolytica [30]) that actually coexpressed AnFaeA and

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

• , respectively. The compounds 2CzCF3, 2CzSCF3, and 2CzSF5, from Type I molecules, show significant promise as deep blue TADF emitters, possessing high calculated singlet energies in the gas phase (3.62 eV, 3.66 eV, and 3.51 eV, respectively) and small, ΔESTs, of 0.17 eV, 0.22 eV, and 0.07 eV, respectively. For

• compounds 5CzSCF3 and 5CzSF5, from Type II molecules, the singlet energies are stabilized to 3.24 eV and 3.00 eV, respectively, while ΔESTs are 0.27 eV and 0.12 eV, respectively, thus both show promise as blue or sky-blue TADF emitters. All these six molecules possess a dense number of intermediate excited

• carbazoles was disposed meta or para to the cyano acceptor [19]. OLEDs fabricated using 2,6-2CzBN as the emitter exhibited deep blue emission with λEL = 418 nm and CIE coordinate of (0.15, 0.05); however, due to the low photoluminescence quantum yields (ΦPLs) (28% in 10 wt % DPEPO films) and relatively slow

Multiswitchable photoacid–hydroxyflavylium–polyelectrolyte nano-assemblies

• Alexander Zika and
• Franziska Gröhn

Beilstein J. Org. Chem. 2021, 17, 166–185, doi:10.3762/bjoc.17.17

• protonated state. For cycle II, the changes upon the addition of HCl are the same as for the Flavy only solution, suggesting the presence of AH+. At a pH value of 5.0 the intensity of the band at λ = 550 nm decreases (blue curve) meaning that AH+ transforms to form B from Flavy leading to state D. This can

Supramolecular polymers with reversed viscosity/temperature profile for application in motor oils

• Jan-Erik Ostwaldt,
• Christoph Hirschhäuser,
• Stefan K. Maier,
• Carsten Schmuck and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2021, 17, 105–114, doi:10.3762/bjoc.17.11

• -complementary [14] binding units (BU, blue) and a connecting linker unit (LU, green) to connect the BUs. In this case, the BUs are ureidopyrimidone units, which dimerize due to a fourfold hydrogen bond, thus allowing for strong supramolecular interactions [15]. Due to the flexibility of the LUs, the BUs can

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

• spectra of rac-TBPP/DGG co-gel (red line) and rac-TBPP/LGG (blue line) co-gel at the molar ratio of 1:80. (a) UV–vis absorption spectra of rac-TBPP and rac-TBPP/DGG co-gel (rac-TBPP/DGG = 1:80). (b) FTIR spectra of DGG and rac-TBPP/DGG co-gels at molar ratios of 1:80 and 1:16, respectively. SEM images of

Recent progress in the synthesis of homotropane alkaloids adaline, euphococcinine and N-methyleuphococcinine

• Dimas J. P. Lima,
• Antonio E. G. Santana,
• Michael A. Birkett and
• Ricardo S. Porto

Beilstein J. Org. Chem. 2021, 17, 28–41, doi:10.3762/bjoc.17.4

• ), isolated from the Colorado blue spruce Picea pungens, are members of this alkaloid family. Their unique bicyclic system with a quaternary stereocenter, and the potent biological activity exerted by these homotropane alkaloids, make them attractive synthetic targets. This work aims briefly to review the

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

• that the probe had a high selectivity for Hg2+. At the same time, under irradiation with 365 nm ultraviolet light, it was found that the OST solution was colorless and transparent when metal ions other than mercury were added. Only after Hg2+ was added, it showed a bright blue fluorescence (Figure 1B

Synthesis, crystal structures and properties of carbazole-based [6]helicenes fused with an azine ring

• Daria I. Tonkoglazova,
• Anna V. Gulevskaya,
• Konstantin A. Chistyakov and
• Olga I. Askalepova

Beilstein J. Org. Chem. 2021, 17, 11–21, doi:10.3762/bjoc.17.2

• electroactive materials [52][53][54]. Carbazole-based [6]helicenes [42] and [7]helicenes [50] showed deep blue electroluminescence and have been investigated in OLED devices. Some carbazole-based [5]- and [6]helicenes have been used as visible light photoinitiators for cationic and radical polymerization [41

• ]helicenes 10 only weak fluorescence in the solution under UV irradiation was observed (Table 7, see also Supporting Information File 1, Figures S42–S45). Helicenes 10b and 10c exhibited blue emission with emission peaks at 481 and 440 nm, respectively. Quinoxaline-fused helicene 10a demonstrated a yellow

Synthesis of tetrafluorinated piperidines from nitrones via a visible-light-promoted annelation reaction

• Vyacheslav I. Supranovich,
• Igor A. Dmitriev and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2020, 16, 3104–3108, doi:10.3762/bjoc.16.260

• photocatalyst activated by blue light. The annelation is a result of a radical addition at the nitrone, intramolecular nucleophilic substitution, and reduction of the N–O bond. Keywords: difluoroalkylation; nitrones; organofluorine compounds; photocatalysis; radical addition; Introduction Nitrogen-containing

• fluorinated piperidines based on an accidentally discovered annelation reaction proceeding under reductive conditions. Results and Discussion Nitrone 1a was selected as a model substrate and it was combined with commercially available dibromide 2a under blue light irradiation in the presence of an iridium

Chemical constituents of Chaenomeles sinensis twigs and their biological activity

• Joon Min Cha,
• Dong Hyun Kim,
• Lalita Subedi,
• Zahra Khan,
• Sang Un Choi,
• Sun Yeou Kim and
• Chung Sub Kim

Beilstein J. Org. Chem. 2020, 16, 3078–3085, doi:10.3762/bjoc.16.257

• which the results were expressed as a percentage of the control group (untreated cells). Chemical structures of compounds 1–13. Structure elucidation of compound 1. (A) Key COSY (blue bold) and HMBC (red arrows) correlations of 1. (B) Key NOESY (black dashed) correlations of 1. The 3D structure of 1 was

Semiautomated glycoproteomics data analysis workflow for maximized glycopeptide identification and reliable quantification

• Steffen Lippold,
• Arnoud H. de Ru,
• Jan Nouta,
• Peter A. van Veelen,
• Magnus Palmblad,
• Manfred Wuhrer and
• Noortje de Haan

Beilstein J. Org. Chem. 2020, 16, 3038–3051, doi:10.3762/bjoc.16.253

• glycopeptide clusters detected by GlycopeptideGraphMS. Representative GlycopeptideGraphMS output for peptides of interest. Assigned compositions were identified using MS/MS data via Byonic (green) or manual assignment (blue) or by MS1 only (red, GlycopeptideGraphMS with additional accurate-mass and isotopic

• pattern check of the raw data). The assignment of the compositions is based on information from all replicates. Lines between compositions indicate the mass difference for Hex (yellow), HexNAc (blue), HexHexNAc (green), Fuc (red), and NeuAc (purple). * Indicates potential deconvolution errors and

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• ] (Scheme 13B). Exposure of ester 159 to PhSH [75], p-toluidine and a catalytic amount of Ir(dF(CF3)ppy)2(dtbbpy)PF6 under the irradiation of blue LED light [76][77] afforded tricycle 162 in 50% yield. The authors suggested that this process involves an intramolecular 5-exo-conjugated addition of a radical

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

• Figure 3) and their relative intensity was solvent dependent. Indeed, the band at 360 nm is favored and slightly blue shifted when increasing the proticity of the medium (see the comparison of the fluorescence spectra obtained in methanol and in a methanol/TFE 4:1 mixture, Figure 3). A similar behavior

Selected peptide-based fluorescent probes for biological applications

• Debabrata Maity

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

• enhanced and blue-shifts after affinity/recognition in a polar solvent. Several computational studies confirmed that the spectral change is caused by the insertion of the environment-sensitive fluorophore in the hydrophobic domains/grooves of the target protein/DNA (Figure 1A). The major problem of these

• ). Fluorescence resonance energy transfer (FRET) relies on the distance-dependent transfer of energy from a donor fluorophore to an acceptor fluorophore. Genetically encoded fluorophores, such as green fluorescent protein (GFP) and related blue, cyan, yellow and red fluorescent proteins have provided the ability

• use of pyrene as a fluorophore has two major disadvantages such as poor quantum yield and an emission in the blue region, which is unfavorable for potential applications in biological systems. The Schmuck group successfully developed several peptide-based probes using these approaches for targeting

Naphthalonitriles featuring efficient emission in solution and in the solid state

• Sidharth Thulaseedharan Nair Sailaja,
• Iván Maisuls,
• Jutta Kösters,
• Alexander Hepp,
• Andreas Faust,
• Jens Voskuhl and
• Cristian A. Strassert

Beilstein J. Org. Chem. 2020, 16, 2960–2970, doi:10.3762/bjoc.16.246

• scattering (DLS). The steady-state and time-resolved photoluminescence spectroscopy studies revealed that all the molecules show intense fluorescence both in solution and in the aggregated state. In THF solutions, a blue emission was observed for the unsubstituted (H), methyl- (Me) and tert-butyl- (t-Bu

• -electron donating capability. Interestingly, upon aggregation in water-containing media, H, Me and t-Bu show a slight red-shift of the emission and a blue-shift is observed for OMe, SMe and NMe2. The crystal structure of Me allowed a detailed discussion of the structure–property relationship. Clearly, N

• , the π-donor nature of the substituents on the phenyl ring constitutes the main parameter that influences the photophysical properties, such as excited state lifetimes and photoluminescence quantum yields. Hence, a series of highly luminescent materials from deep blue to red emission depending on

Construction of pillar[4]arene[1]quinone–1,10-dibromodecane pseudorotaxanes in solution and in the solid state

• Xinru Sheng,
• Errui Li and
• Feihe Huang

Beilstein J. Org. Chem. 2020, 16, 2954–2959, doi:10.3762/bjoc.16.245

• , chloroform-d, 298 K). Normalized UV–vis spectra: H (black); H upon adding 0.5 equiv of G (red); and H upon adding 1 equiv of G (blue). [H] = 3.00 mM. Chemical structures and schematic representation of (a) the pillar[4]arene[1]quinone H; (b) 1,10-dibromodecane (G); and (c) schematic representation of the

UV resonance Raman spectroscopy of the supramolecular ligand guanidiniocarbonyl indole (GCI) with 244 nm laser excitation

• Tim Holtum,
• Vikas Kumar,
• Daniel Sebena,
• Jens Voskuhl and
• Sebastian Schlücker

Beilstein J. Org. Chem. 2020, 16, 2911–2919, doi:10.3762/bjoc.16.240

• sufficiently blue-shifting the UVRR spectrum away from the UV-excited autofluorescence [20][21]. This is illustrated in Figure 2 for the UVRR spectra of a 1 mM solution of toluene in acetonitrile acquired with 240, 258, and 266 nm laser excitation. The spectra are plotted as a function of the wavelength

• (rather than the relative wavenumber/Raman shift) to illustrate the blue-shifting of the UVRR spectral range of interest (0–3000 cm−1) when moving towards the lower excitation wavelengths. It can be seen that the spectral position of the UV-excited autofluorescence is independent of the choice of the

• the first experiment, the UVRR spectrum of a 1:1 mixture of benzoic acid and GCI ethyl amide (both 200 µM) was acquired with 244 nm laser excitation (shown as blue curve in Figure 7). This spectrum is compared to the UVRR spectra of the corresponding binding partners GCI ethyl amide (200 µM, black

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

• ): 1af (red), 1bf (yellow), 1cf (green), and 1df (blue) (n = 3). Conditions: 1 μM oligonucleotide, 300 mM NaClO4, 5 mM Mg(ClO4)2, and 20 mM MOPS buffer (pH 7.4). Elution of the aptamers from the ATP-agarose gel in the presence of 1 equiv of Ag(I): 1af (red), 1bf (yellow), 1cf (green), and 1df (blue) (n

Changed reactivity of secondary hydroxy groups in C8-modified adenosine – lessons learned from silylation

• Jennifer Frommer and
• Sabine Müller

Beilstein J. Org. Chem. 2020, 16, 2854–2861, doi:10.3762/bjoc.16.234

• various Pd-catalyzed reactions. Comparing the two reaction paths, the overall yield of the desired adenosine derivative 8 was increased from 2% to 12% over 7 reaction steps by changing the protecting group strategy. Characterization and assignment of the TBDMS isomers via HSQC (red) and HMBC (blue) NMR

Dirhamnolipid ester – formation of reverse wormlike micelles in a binary (primerless) system

• David Liese,
• Hans Henning Wenk,
• Xin Lu,
• Jochen Kleinen and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2020, 16, 2820–2830, doi:10.3762/bjoc.16.232

• controlled and adjusted with a Peltier element. Chemical structure of dirhamnolipid 1. Solubility of the dirhamnolipid esters in various solvents (+ = soluble, − = insoluble, G = gel). Phase transition temperature for the dirhamnolipid esters in toluene while heating (TGS, blue) and cooling (TSG, orange

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

• ) spectroscopy. Upon the addition of the ligands to 22AG the positive CD band of the DNA at 295 nm remained essentially unchanged, whilst the blue-shifted shoulder to this band disappeared and a negative signal at 260 nm formed, whose intensity depended on the chain length between the berberine and the adenine

• compound 4c in the absence (left) and the presence (right) of 22AG. Melting temperatures, ΔTm, of G4-DNA (cDNA = 0.2 µM) F21T (black), F21T plus ds26 (15 equiv, red), FkrasT (blue), FmycT (green), FkitT (light blue), and Fa2T (magenta) in the presence of 4e at different LDR = 0.00, 1.25, 2.50, 5.00 in Na

• ; ds26: d(CA2TCG2ATCGA2T2CGATC2GAT2G). CD spectra of 22AG (A) and a2 (B) in the presence of the ligands 4c (in K+-phosphate buffer (pH 7.0 with 10% v/v DMSO) at LDR 0.00 (black), 0.05 (red), 0.20 (blue), 0.50 (magenta), and 1.00 (green); cDNA = 20 µM; T = 20 °C. The arrows indicate the development of the

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

• HeLa cells treated with a mixture of RPE (8 μg/mL) and A) 1 (400 μM) or B) 2 (400 μM) after 2 h and 4 h of incubation. Blue: nucleus, red: RPE. Synthetic route to the branched peptides. (i) HBTU, DIPEA, DMF, 12 h, rt, (ii) TFA, 2 h, rt, and (iii) 20% piperidine in DMF, 2 h, rt. Supporting Information