A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

• temperature and pressure range access, the potential for in-line purification, monitoring and telescoping, linear scalability and more efficient mixing. These applications are very attractive for a synthetic chemist in all settings, especially considering the current ever-increasing industrial pressure to

• direct diagnostics to be obtained facilitating rapid analysis of the content and assessment of the extent of reaction in real-time. Several in-line monitoring tools, for example, ReactIR [58][59][60][61][62] and flow based NMR [63][64][65][66] which allow for substrate specific, non-consuming analysis

• monitoring features such as pressure sensors that can both detect, assess, and if necessary, invoke emergency venting or diversion of material to auxiliary depressurisation stages, often without needing a full reactor shut down. There are numerous examples within the literature in which a flow synthesis has

Synthesis of 10-O-aryl-substituted berberine derivatives by Chan–Evans–Lam coupling and investigation of their DNA-binding properties

• Peter Jonas Wickhorst,
• Mathilda Blachnik,
• Denisa Lagumdzija and
• Heiko Ihmels

Beilstein J. Org. Chem. 2021, 17, 991–1000, doi:10.3762/bjoc.17.81

• monitoring of the temperature-dependent Förster resonance energy transfer (FRET) between the dyes [46]. The particular oligonucleotide sequences were chosen because they are known to be involved in biologically relevant processes, namely in the transcription regulation of myc (FmycT) [47][48], kit (FkitT

A chromatography-free and aqueous waste-free process for thioamide preparation with Lawesson’s reagent

• Ke Wu,
• Yichen Ling,
• An Ding,
• Liqun Jin,
• Nan Sun,
• Baoxiang Hu,
• Zhenlu Shen and
• Xinquan Hu

Beilstein J. Org. Chem. 2021, 17, 805–812, doi:10.3762/bjoc.17.69

• following the same procedure as described above for the EtOH treatment. To our surprise, the decomposition was much slower as expected (TLC monitoring, see Supporting Information File 1). It was assumed that the ring-opening could be influenced by water or by the in situ-generated thiophosphonic acid. Thus

• longer time for the reaction with LR was essential for the completion of the reaction according to TLC monitoring. Following the similar workup procedure as described for compound 4, the resulting crude product was recrystallized from toluene to afford the product as bright-yellow crystalline solid in 91

• a nitrogen atmosphere. The reaction was completed in 3 h by TLC monitoring. Then, to the cooled mixture, were added 100 mL of ethylene glycol (excess), together with 1.0 mL of water, and the resulting mixture was stirred at 95 °C. TLC monitoring of the toluene layer showed that the byproduct A from

Effective microwave-assisted approach to 1,2,3-triazolobenzodiazepinones via tandem Ugi reaction/catalyst-free intramolecular azide–alkyne cycloaddition

• Maryna O. Mazur,
• Oleksii S. Zhelavskyi,
• Eugene M. Zviagin,
• Svitlana V. Shishkina,
• Vladimir I. Musatov,
• Maksim A. Kolosov,
• Elena H. Shvets,
• Anna Yu. Andryushchenko and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2021, 17, 678–687, doi:10.3762/bjoc.17.57

• solubility [20]. Firstly, we used a procedure similar to described by I. Akritopoulou-Zanze et al. [13] for cyclization: compound 6aab was refluxed in benzene for 8 hours until TLC monitoring demonstrated the full transformation of starting material into a new compound. The evaporation of the solution gave a

Synthesis of (Z)-3-[amino(phenyl)methylidene]-1,3-dihydro-2H-indol-2-ones using an Eschenmoser coupling reaction

• Lukáš Marek,
• Lukáš Kolman,
• Jiří Váňa,
• Jan Svoboda and
• Jiří Hanusek

Beilstein J. Org. Chem. 2021, 17, 527–539, doi:10.3762/bjoc.17.47

• minimum amount of dry DMF and a saturated solution of 3-bromooxindole (1a–c, n1a–c) in dry DMF was added. The reaction mixture was stirred for 20 h at room temperature (TLC monitoring; silica gel plates/EtOAc/hexane) and then diluted with an aqueous NaHCO3 solution (5%, 50 mL). The suspension was

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

• both pathways. a3-step pathway. b1-step pathway. (A) Spectrometric monitoring (at 530 nm) of 4NTC released after the action of Fae on 12 in the presence of sodium periodate and (B) control reactions of the discontinuous assay of the Fae-mediated hydrolysis of 12. The optical density (OD) was measured

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

• inhibitors in situ using 19F NMR spectroscopy (Figure 6). For this, the activity of the membrane-bound FAAH enzyme was evaluated by monitoring the hydrolysis of a fluorinated anandamide analogue ARN1203, a previously reported FAAH substrate, to arachidonic acid and 1-amino-3-fluoropropanol in the presence

• Granqvist et al. [101], the 19F NMR signals observed when employing these probes to evaluate the thermal denaturation of a range of RNA hairpins were indeed found to be sensitive enough to allow the monitoring of their secondary structural changes with relatively wide shift dispersion. It also enabled to

• the detection of the new compounds in the complex supernatants of organisms producing non-ribosomal peptides and polyketides. It has been especially useful for monitoring the incorporation

Au(III) complexes with tetradentate-cyclam-based ligands

• Ann Christin Reiersølmoen,
• Thomas N. Solvi and
• Anne Fiksdahl

Beilstein J. Org. Chem. 2021, 17, 186–192, doi:10.3762/bjoc.17.18

• moderate to excellent yields of tetracoordinated 5a-Au(III) and 6a-Au(III) N,N,N,N-complexes with alternating five- and six-membered chelate rings (50% and 96%, respectively, Scheme 3). Monitoring the formation of complex 5a-Au(III), using 1H NMR, and 1H,15N-HMBC, clearly indicated a tetra-nitrogen

Supramolecular polymerization of sulfated dendritic peptide amphiphiles into multivalent L-selectin binders

• David Straßburger,
• Svenja Herziger,
• Katharina Huth,
• Moritz Urschbach,
• Rainer Haag and
• Pol Besenius

Beilstein J. Org. Chem. 2021, 17, 97–104, doi:10.3762/bjoc.17.10

• copper-catalyzed azide–alkyne cycloaddition (Scheme 2). The reaction took place in degassed DMSO at 50 °C with CuSO4 pentahydrate, sodium ascorbate and tris(benzyltriazolylmethyl)amine (TBTA) as chelating species. HPLC-monitoring of the reaction showed a full conversion after three days and the crude

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

• be used for the quantitative detection and monitoring of mercury ions in the environment. Results and Discussion OST fluorescence probe for Hg2+ identification Selectivity of the fluorescent OST probe to metal ions The specificity of a probe for metal ions is the key factor to evaluate the

Secondary metabolites of Bacillus subtilis impact the assembly of soil-derived semisynthetic bacterial communities

• Heiko T. Kiesewalter,
• Carlos N. Lozano-Andrade,
• Mikael L. Strube and
• Ákos T. Kovács

Beilstein J. Org. Chem. 2020, 16, 2983–2998, doi:10.3762/bjoc.16.248

• contained 13 genera with a relative abundance of >0.19% in at least one mock community. Furthermore, it was demonstrated that the addition of B. subtilis suppressed the genera Lysinibacillus and Viridibacillus. Additional optical density (OD)-based growth monitoring of the selected strain Lysinibacillus

• significance of pairs was determined with the Welch two-sample t-test, and the differences among groups >2 was determined with the one-way analysis of variance (ANOVA) test and the Tukey HSD test. The statistical significance was determined with an alpha level <0.05. Growth monitoring of L. fusiformis

Selected peptide-based fluorescent probes for biological applications

• Debabrata Maity

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

• 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

• detection The genetic information carrier nucleic acids are present in nearly all living organisms. Fluorescence monitoring of nucleic acids has become increasingly important in medical diagnosis, drug discovery, environmental monitoring, food safety etc. [40][41]. Schmuck et al. reported several

• excimer (490 nm) to monomer emission (406 nm, Figure 3B). Thus, monitoring the relative fluorescence intensities at two wavelengths (F406/F490) allowed the ratiometric detection of nucleic acids. Schmuck et al. reported a similar cationic peptide beacon 3 coupled with a FRET pair, a naphthalene donor and

Controlled decomposition of SF₆ by electrochemical reduction

• Sébastien Bouvet,
• Bruce Pégot,
• Stéphane Sengmany,
• Erwan Le Gall,
• Eric Léonel,
• Anne-Marie Goncalves and
• Emmanuel Magnier

Beilstein J. Org. Chem. 2020, 16, 2948–2953, doi:10.3762/bjoc.16.244

• monitoring the potential scan rate. By cyclic voltametry, unlike macroelectrodes, the polarization of microelectrodes with a low potential scan rate (≤25 mV/s) leads to a drastic decrease of Cottrel contribution which involves the disappearance of current waves. The resulting current becomes a stationary

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

• , Universitätsstrasse 7, 45141 Essen, Germany 10.3762/bjoc.16.240 Abstract Ultraviolet resonance Raman (UVRR) spectroscopy is a powerful vibrational spectroscopic technique for the label-free monitoring of molecular recognition of peptides or proteins with supramolecular ligands such as guanidiniocarbonyl pyrroles

• selectivity for monitoring the CBS, but the resulting UVRR spectrum overlaps with the UV-excited autofluorescence from the aromatic binding partners. This necessitates the use of a laser excitation <260 nm for spectrally separating the UVRR spectrum of the supramolecular ligand from the UV-excited

• strengths. Various spectroscopic techniques can be employed for monitoring these changes. For example, electronic absorption or fluorescence spectroscopy can probe the spectral differences due to the complexation of the supramolecular ligand with a peptide or protein. However, electronic spectroscopies

One-pot multicomponent green Hantzsch synthesis of 1,2-dihydropyridine derivatives with antiproliferative activity

• Giovanna Bosica,
• Kaylie Demanuele,
• José M. Padrón and
• Adrián Puerta

Beilstein J. Org. Chem. 2020, 16, 2862–2869, doi:10.3762/bjoc.16.235

• particularly positive effect. Since the presence of water was shown to be detrimental, the ammonium acetate (3) used was left to dry in a desiccator before use. Reaction monitoring was mostly done using thin-layer chromatography (TLC) and at times also GC. These techniques showed the occurrence of at least

Using multiple self-sorting for switching functions in discrete multicomponent systems

• Amit Ghosh and
• Michael Schmittel

Beilstein J. Org. Chem. 2020, 16, 2831–2853, doi:10.3762/bjoc.16.233

• innovative catch–release system with multiple functions combined the ON/OFF-adjustment of silver(I) catalysis and fluorescence monitoring [59]. Actually, the ratiometric luminescence response allowed the exact monitoring of the catalytic activity. In the initial incomplete self-sorting (state SelfSORT-I

Selective recognition of ATP by multivalent nano-assemblies of bisimidazolium amphiphiles through “turn-on” fluorescence response

• Rakesh Biswas,
• Surya Ghosh,
• Shubhra Kanti Bhaumik and
• Supratim Banerjee

Beilstein J. Org. Chem. 2020, 16, 2728–2738, doi:10.3762/bjoc.16.223

• presence of positive surface charges on the multivalent aggregates led to ATP binding which was accompanied by a significant increase in the excimeric emission intensity. This provided a convenient way of monitoring ATP binding in a “turn-on” mode and an efficient detection of ATP was achieved in aqueous

Activation of pentafluoropropane isomers at a nanoscopic aluminum chlorofluoride: hydrodefluorination versus dehydrofluorination

• Maëva-Charlotte Kervarec,
• Thomas Braun,
• Mike Ahrens and
• Erhard Kemnitz

Beilstein J. Org. Chem. 2020, 16, 2623–2635, doi:10.3762/bjoc.16.213

• =CHCH2C6D5 (9) and CF3CH=CHC6D5 (8, Scheme 11, middle). In neat silane, 5 and 6 were detected in a ratio of 1:4 (Scheme 11, bottom). Notably, for all conversions (C6D6 and silane, C6D12 and silane, or in neat silane), monitoring of the reaction by 19F NMR spectroscopy led to the observation of the early

Anion exchange resins in phosphate form as versatile carriers for the reactions catalyzed by nucleoside phosphorylases

• Julia N. Artsemyeva,
• Ekaterina A. Remeeva,
• Tatiana N. Buravskaya,
• Irina D. Konstantinova,
• Roman S. Esipov,
• Anatoly I. Miroshnikov,
• Natalia M. Litvinko and
• Igor A. Mikhailopulo

Beilstein J. Org. Chem. 2020, 16, 2607–2622, doi:10.3762/bjoc.16.212

• gently stirred at 47 °C for 48 h, with monitoring the product formation by HPLC. After 48 h, the conversion of the base into nucleoside reached equilibrium at 85% of the latter. The turbid (not reacted starting base according to TLC and barium phosphate) reaction mixture was filtered, the filtrate

• ; 1.2 mequiv/mL) in 15 mL of distilled water; pH 7.0), Ara-U (170 mg, 0.7 mmol) and MgCl2·6H2O (71 mg, 0.5 mmol of MgCl2 per 1 mmol of Ara-U), followed by UP (105 IU; 150 units per 1 mmol of substrate) were added, and the reaction mixture was gently stirred at 40 °C with monitoring the Ara-U

• reaction mixture was gently stirred at 47 °C for 48 h with monitoring the product formation by HPLC (HPLC system A, 5% H2O/MeCN), λ = 260 nm, 1 mL/min; tR 4.5 and 5.1 min for the base and nucleoside, respectively). After 48 h, the conversion of the base into nucleoside reached 85%. The turbid (not reacted

NMR Spectroscopy of supramolecular chemistry on protein surfaces

• Peter Bayer,
• Anja Matena and
• Christine Beuck

Beilstein J. Org. Chem. 2020, 16, 2505–2522, doi:10.3762/bjoc.16.203

• while titrating the other binding partner. However, for larger supramolecular hosts that encapsulate a large part of their (usually smaller) guest, it is advantageous to monitor the guest’s resonances. Monitoring binding with this simple spectrum requires at least one signal that does not overlap with

• supramolecular tweezers that bind to lysine or arginine, tweezers have been titrated to the free amino acids or short peptides, monitoring the Lys and Arg resonances [5][80]. While all resonances of the guest amino acid shift upon tweezer binding, the effect is most severe for the H atoms at the end of the side

• experiment, monitoring 15N,2H-labeled 14-3-3ΔC protein in 1H,15N-TROSY-HSQC experiments [103], was used to investigate the stabilizing effect of several compounds on the interaction of 14-3-3 with different unlabeled peptide epitopes derived from 14-3-3 cargo proteins [104][105][106]. E.g., a semi-synthetic

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

• monitoring for accurate printing. Between the printing of each probe (glycan), there is usually a wash step which is performed to prevent any carryover for the next ligand, and this would need to be determined empirically depending on the glycoconjugates used. After the entire print run, the slides are left

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

• molecules were dyes used for the DNA/RNA labelling or even monitoring or influencing DNA/RNA function [3][4]. However, due to the complexity of DNA-coded or RNA-coded processes, also including epigenetics, there is permanent need for novel dyes, differing in selectivity, colour, or method of monitoring [5

• monitoring, fluorescence is still the most popular method [8][9][10][11]. However, many new techniques or established ones with increased sensitivity are constantly improved or developed to report complementary to fluorescence. For instance, circular dichroism (CD) spectropolarimetry, highly sensitive to

Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

• Thomas Schneider,
• Michael Keim,
• Bianca Seitz and
• Gerhard Maas

Beilstein J. Org. Chem. 2020, 16, 2064–2072, doi:10.3762/bjoc.16.173

• °C, 19F NMR monitoring of the reaction’s progress indicated the appearance of a second product beside the 1,4-cyclohexadien-1-iminium salt 4-Ch. Further investigations revealed that the new product was the dihydrofluorene 7, resulting from 4-Ch by an intramolecular electrophilic aromatic substitution

Three new O-isocrotonyl-3-hydroxybutyric acid congeners produced by a sea anemone-derived marine bacterium of the genus Vibrio

• Dandan Li,
• Enjuro Harunari,
• Tao Zhou,
• Naoya Oku and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1869–1874, doi:10.3762/bjoc.16.154

• (10 × 250 mm), eluted by a gradient method (MeCN/0.1% HCOOH) at 4 mL/min, with monitoring at 254 nm, to give the (S)-PGME amide 4a (2.9 mg, 93%) as colorless oil. The PGME amides 1a/b–3a/b and 4b were prepared by the same procedure but replacing the starting material and the chiral reagent accordingly