Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• electron transfer and internal barriers Sensitized generation of reactive intermediates such as radicals and conjugate acid [5] also followed in the case of NIR sensitive materials a photoinduced electron transfer (PET). However, it did not work as smooth as disclosed for UV systems [83] because there was

• often no reaction between a cationic sensitizer and an electron acceptor; i.e. an iodonium salt [5]. However, the use of stronger emitting LEDs resulted sometimes in successful PET [67]. Particularly, light sources with low emission intensity arose these issues. This supports the idea that the system

Synthesis of a dihalogenated pyridinyl silicon rhodamine for mitochondrial imaging by a halogen dance rearrangement

• Jessica Matthias,
• Thines Kanagasundaram,
• Klaus Kopka and
• Carsten S. Kramer

Beilstein J. Org. Chem. 2019, 15, 2333–2343, doi:10.3762/bjoc.15.226

• the use in multimodal (PET/OI) medical imaging of mitochondria in cancerous cells. Results: A dihalogenated fluorinatable pyridinyl rhodamine could be successfully synthesized with the high yield of 85% by application of a halogen dance (HD) rearrangement. The near-infrared dye shows a quantum yield

• optical properties for medical and bioimaging. As a compound with intrinsic mitochondria targeting ability, the radiolabelled analogue can be applied in multimodal (PET/OI) imaging of mitochondria for diagnostic and therapeutic use in, e.g., cancer patients. Keywords: halogen-dance reaction

• of the ester group in 2’-position, an isopropyl ester derivative; another one might be the effects of the fluorine atoms and the ester group on the HOMO energy level of the benzene moiety. Since our group is interested in PET-active near-infrared (NIR) dyes for bimodal medical imaging (PET/optical

Metal-free mechanochemical oxidations in Ertalyte^® jars

• Andrea Porcheddu,
• Francesco Delogu,
• Lidia De Luca,
• Claudia Fattuoni and
• Evelina Colacino

Beilstein J. Org. Chem. 2019, 15, 1786–1794, doi:10.3762/bjoc.15.172

• significantly by switching to an Ertalyte® jar (86%) [68] which could be further enhanced (93%) by slightly increasing the amount of the oxidant agent (1.5 equiv). Ertalyte® jars (Figure S1b, in Supporting Information File 1) are composed of polyethylene terephthalate (PET-P) and characterized by wear- and

Complexation of a guanidinium-modified calixarene with diverse dyes and investigation of the corresponding photophysical response

• Yu-Ying Wang,
• Yong Kong,
• Zhe Zheng,
• Wen-Chao Geng,
• Zi-Yi Zhao,
• Hongwei Sun and
• Dong-Sheng Guo

Beilstein J. Org. Chem. 2019, 15, 1394–1406, doi:10.3762/bjoc.15.139

• as well-demonstrated fluorescence quenchers acting through a photoinduced electron transfer (PET) mechanism [8][28][29], we hypothesize an electron transfer-induced quenching in the GC5A–Fl complex as underlying mechanism. The binding stoichiometry between GC5A and Fl was determined to be 1:1

• a PET pathway. The fluorescence lifetime of AlPcS4 remains unaltered after addition of GC5A, indicating the absence of dynamic quenching of the residual uncomplexed AlPcS4 and therefore confirming the formation of a statically quenched complex. UV–vis titration further verified the formation of a

• ground-state complex, with drastic changes in both, band shapes and intensities. The calculated rate constant of PET is faster than that of fluorescence and intersystem crossing, which makes it a more favorable deactivation pathway of the first excited singlet state leading to both fluorescence quenching

Formation of an unexpected 3,3-diphenyl-3H-indazole through a facile intramolecular [2 + 3] cycloaddition of the diazo intermediate

• Andrew T. King,
• Hugh G. Hiscocks,
• Lidia Matesic,
• Mohan Bhadbhade,
• Roger Bishop and
• Alison T. Ung

Beilstein J. Org. Chem. 2019, 15, 1347–1354, doi:10.3762/bjoc.15.134

• body. Synthons are becoming more prevalent in imaging modalities like positron emission tomography (PET) as there is a greater need to further investigate lesions, and disease tissues on the molecular level. However, issues with the stability of sulfonyl fluorides have been reported in the literature

Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• a few steps into (2S,5'S)-tricholomic acid [47]. The absolute configuration of (R)-(−)-carnitine was established by enzymatic decarboxylation of (2S,3R)-3-hydroxyglutamic acid followed by exhaustive methylation [121]. Fluoroglutamic acids are of special interest for PET imaging [122] and among other

Synthesis of a tubugi-1-toxin conjugate by a modulizable disulfide linker system with a neuropeptide Y analogue showing selectivity for hY1R-overexpressing tumor cells

• Rainer Kufka,
• Robert Rennert,
• Goran N. Kaluđerović,
• Lutz Weber,
• Wolfgang Richter and
• Ludger A. Wessjohann

Beilstein J. Org. Chem. 2019, 15, 96–105, doi:10.3762/bjoc.15.11

• -overexpressing breast cancers in a patients pilot study (n = 5) by using a PET tracer based on the hY1R-specific NPY analogue [F7,P34]-pNPY [35]. This study demonstrated that it is not to be expected that NPY-based diagnostic or therapeutic PDCs will pass the blood-brain barrier and therefore could induce

Thermophilic phosphoribosyltransferases Thermus thermophilus HB27 in nucleotide synthesis

• Ilja V. Fateev,
• Ekaterina V. Sinitsina,
• Aiguzel U. Bikanasova,
• Maria A. Kostromina,
• Elena S. Tuzova,
• Larisa V. Esipova,
• Tatiana I. Muravyova,
• Alexei L. Kayushin,
• Irina D. Konstantinova and
• Roman S. Esipov

Beilstein J. Org. Chem. 2018, 14, 3098–3105, doi:10.3762/bjoc.14.289

• thermophilic transferases in nucleotide synthesis. A scheme of purine nucleotide synthesis using TthAPRT and TthHPRT is shown in Figure 2. Results and Discussion Genes TT_RS08985 and TT_RS06315 from T. thermophilus HB27, coding TthHPRT and TthAPRT, were cloned into expression plasmid vectors pET 23a+ and pET

• ΔEcoRI-B int::(lacI::PlacUV5::T7 gene1) i21 Δnin5. Plasmid vector: pET 23a+, pET 23d+ (Merck Millipore, USA, MA). Enzymes: NdeI, XhoI, NcoI, T4 DNA-ligase (Thermo Scientific, USA, MA), Encyclo-polymerase (Eurogen, Russia). The protein concentration was determined by the Bradford method [17], using BSA as

• . thermophilus HB27 strain by a polymerase chain reaction (PCR) using synthetic primers. The genes were cloned into the expression vectors pET-23a+ and pET-23d+ respectively. The E. coli strains BL21(DE3)/pER- TthAPRT and C3030/pER- TthHPRT produced the target enzymes mainly in soluble form (culturing conditions

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• and redox reactions are possible. This process is called photoinduced electron transfer (PET). In this context, photoredox catalysis was developed. Light is used to excite the photoredox catalyst which allows electron transfer processes with additives. Both oxidation and reduction reactions can be

Novel solid-phase strategy for the synthesis of ligand-targeted fluorescent-labelled chelating peptide conjugates as a theranostic tool for cancer

• Sagnik Sengupta,
• Mena Asha Krishnan,
• Premansh Dudhe,
• Ramesh B. Reddy,
• Bishnubasu Giri,
• Sudeshna Chattopadhyay and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2018, 14, 2665–2679, doi:10.3762/bjoc.14.244

• tracking molecule to understand the destination of delivered cargos or biologics. For bioimaging of cancer and inflammatory diseases through specific biomarkers [2], several methods including single positron emission computed tomography (SPECT), positron emission tomography (PET) and magnetic resonance

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• excited state (S1) or a triplet excited state (T1), by absorption of a photon with energy hν, which then undergoes photoinduced electron transfer (PET). Following this, the photocatalyst is reduced or oxidised accordingly, such that it returns to its ground state and native oxidation state (Figure 1 and

• molecules have some UV absorbance, but little or no absorbance in the visible part of the spectrum, hence excitation of other reactants is unlikely. Visible light photons are high enough in energy to produce excited states of sufficient reactivity to undergo PET. Once a molecule is electronically excited

• likely to be involved in PET. A molecule with a low Φf will be unlikely to be found in the S1 state, as this state will be highly susceptible to other decay pathways in the timescale of PET. For a molecule to undergo PET when in the T1 state, the intersystem crossing quantum yield (ΦISC) must be

Rational design of boron-dipyrromethene (BODIPY) reporter dyes for cucurbit[7]uril

• Mohammad A. Alnajjar,
• Jürgen Bartelmeß,
• Robert Hein,
• Pichandi Ashokkumar,
• Mohamed Nilam,
• Werner M. Nau,
• Knut Rurack and
• Andreas Hennig

Beilstein J. Org. Chem. 2018, 14, 1961–1971, doi:10.3762/bjoc.14.171

• motifs for CB7. The unprotonated dyes show low fluorescence due to photoinduced electron transfer (PET), whereas the protonated dyes are highly fluorescent. Encapsulation of the binding motif inside CB7 positions the aniline nitrogen at the carbonyl rim of CB7, which affects the pKa value, and leads to a

• quenching by photoinduced electron transfer (PET), whereas the protonated form was brightly fluorescent [31]. We report herein the synthesis and photophysical characterization of BODIPY derivatives with an aniline substituent in the meso-position to which different anchor groups have been attached, and we

• accordance with the anticipated PET mechanism [31][45]. Further, the change in free energy, ∆G, associated with PET was calculated using the Rehm–Weller equation [46]. Therefore, we used a reduction potential of −1.55 V for the 1,3,7,9-tetramethyl-BODIPY core acceptor of 1, 2, and 5 [47] and of −1.81 V for

Synthesis and photophysical studies of a multivalent photoreactive Ru^II-calix[4]arene complex bearing RGD-containing cyclopentapeptides

• Sofia Kajouj,
• Lionel Marcelis,
• Alice Mattiuzzi,
• Adrien Grassin,
• Damien Dufour,
• Pierre Van Antwerpen,
• Didier Boturyn,
• Eric Defrancq,
• Mathieu Surin,
• Julien De Winter,
• Pascal Gerbaux,
• Ivan Jabin and
• Cécile Moucheron

Beilstein J. Org. Chem. 2018, 14, 1758–1768, doi:10.3762/bjoc.14.150

• DNA or the tryptophan (Trp) amino acid residue through a photoinduced electron-transfer (PET) process [16][17][18][19]. Interestingly, the two radical species generated by this PET can recombine to form a covalent photoadduct [20][21][22]. When this photoadduct is formed with the guanine base, the

• radical guanine generated after the photoinduced electron transfer (PET). In order to confirm the occurrence of PET, transient absorption measurements with conjugate 9 were performed in the absence and in the presence of GMP. The recorded transient absorption spectra are presented in Figure 5. In absence

• specific of a monoreduced RuII-TAP•− species [81], confirming that a PET occurs. To verify if a photoadduct can be obtained between the complex anchored on the calixarene platform and a guanine base, a continuous irradiation of a solution containing conjugate 9 and GMP was achieved. The crude irradiation

Cobalt–metalloid alloys for electrochemical oxidation of 5-hydroxymethylfurfural as an alternative anode reaction in lieu of oxygen evolution during water splitting

• Jonas Weidner,
• Stefan Barwe,
• Kirill Sliozberg,
• Stefan Piontek,
• Justus Masa,
• Ulf-Peter Apfel and
• Wolfgang Schuhmann

Beilstein J. Org. Chem. 2018, 14, 1436–1445, doi:10.3762/bjoc.14.121

• hence leads to an overall improved energy efficiency for H2 production. In addition, contrary to the “waste product O2”, FDCA can be further utilized, e.g., for production of polyethylene 2,5-furandicarboxylate (PEF), a sustainable polymer analog to polyethylene terephthalate (PET) and thus represents a

• -refinery based chemicals for a “green” chemical industry [6][7][8]. FDCA was suggested to replace, e.g., terephthalic acid as building block for the formation of polyamides, polyesters, and polyurethanes [6]. Especially, the polymer polyethylene terephthalate (PET), a perpetually used polymer, could be

On the design principles of peptide–drug conjugates for targeted drug delivery to the malignant tumor site

• Eirinaios I. Vrettos,
• Gábor Mező and
• Andreas G. Tzakos

Beilstein J. Org. Chem. 2018, 14, 930–954, doi:10.3762/bjoc.14.80

• presence of oxygen, rendered his observation puzzling for scientists, who still struggle to elucidate the complete mechanism of action of diseased cells. Following the Warburg effect, 18F-deoxyglucose positron emission tomography (FDG–PET) imaging was developed in order to visualize the phenomenon of

Development of novel cyclic NGR peptide–daunomycin conjugates with dual targeting property

• Andrea Angelo Pierluigi Tripodi,
• Szilárd Tóth,
• Kata Nóra Enyedi,
• Gitta Schlosser,
• Gergely Szakács and
• Gábor Mező

Beilstein J. Org. Chem. 2018, 14, 911–918, doi:10.3762/bjoc.14.78

• breast adenocarcinoma cells [15]. Moreover, a 68Ga- radiotracer labeled derivative of the cyclic [KNGRE]-NH2 has been successfully used for tumor diagnostic studies by PET, indicating its specific binding to CD13 receptor expressing tumor tissues [16]. Recently, we reported the synthesis and biochemical

Microfluidic radiosynthesis of [¹⁸F]FEMPT, a high affinity PET radiotracer for imaging serotonin receptors

• Thomas Lee Collier,
• Steven H. Liang,
• J. John Mann,
• Neil Vasdev and
• J. S. Dileep Kumar

Beilstein J. Org. Chem. 2017, 13, 2922–2927, doi:10.3762/bjoc.13.285

• -18; 5-HT1A; microfluidics; PET; Introduction The development of serotonin 1A receptor (5-HT1AR) agonist radiotracers for applications in molecular imaging with positron emission tomography (PET) has been avidly sought over the past two decades, albeit with limited success. The current status of

• serotonin-targeting radiopharmaceuticals was recently reviewed by Paterson et al. [1] and their conclusion was that “the development of PET and single-photon emission computed tomography (SPECT) radioligands to image serotonergic targets is of high interest, and successful evaluation in humans is leading to

• invaluable insight into normal and abnormal brain function”. A further review by us focusing on 5-HT1AR overviewed a number of PET and SPECT tracers that have been tested in vivo with varying efficacy [2]. A few representative compounds which show the structures that have been tested as radiotracers are

Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides

• Irwan Iskandar Roslan,
• Kian-Hong Ng,
• Gaik-Khuan Chuah and
• Stephan Jaenicke

Beilstein J. Org. Chem. 2017, 13, 2739–2750, doi:10.3762/bjoc.13.270

• antimicrobial [35][36], antitumor [37][38][39], antibacterial [40], and anti-allergic agents [41]. In addition, compounds with this backbone are employed as kinase inhibitors and receptors [42][43][44] and as a tracer for PET imaging of β-amyloid plaques [45][46]. The conventional approach for the construction

Regioselective decarboxylative addition of malonic acid and its mono(thio)esters to 4-trifluoromethylpyrimidin-2(1H)-ones

• Sergii V. Melnykov,
• Andrii S. Pataman,
• Yurii V. Dmytriv,
• Svitlana V. Shishkina,
• Mykhailo V. Vovk and
• Volodymyr A. Sukach

Beilstein J. Org. Chem. 2017, 13, 2617–2625, doi:10.3762/bjoc.13.259

• Organofluorine compounds now play an essential role in the development of new materials for solar cells [1][2][3], radiotracers for PET imaging [4], agrochemicals [5][6], sensitive chemical probes for 19F nuclear magnetic resonance investigation of biological experiments [7][8], and are most widely used in the

Dialkyl dicyanofumarates and dicyanomaleates as versatile building blocks for synthetic organic chemistry and mechanistic studies

• Grzegorz Mlostoń and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2017, 13, 2235–2251, doi:10.3762/bjoc.13.221

• radical intermediate 46 governs the formal [4 + 2]-cycloaddition reaction of E-1b with 3,4-di(α-styryl)furan (47, Scheme 15). The photoinduced reaction occurs via an electron-transfer (PET) process and led to the formation of the polycyclic product 48 in a stereospecific manner [52]. Similar products were

Accessing simply-substituted 4-hydroxytetrahydroisoquinolines via Pomeranz–Fritsch–Bobbitt reaction with non-activated and moderately-activated systems

• Marco Mottinelli,
• Mathew P. Leese and
• Barry V. L. Potter

Beilstein J. Org. Chem. 2017, 13, 1871–1878, doi:10.3762/bjoc.13.182

• a Bruker microTOF. Melting points were determined using an Optimelt block and are uncorrected. 2,2-Dimethoxyacetaldehyde was purchased as an aqueous solution and was extracted in CHCl3 before use. Petroleum ether (pet. ether) used for chromatography was the 40–60 °C distillate. The general

• yellow oil (3.87 g). N-Benzyl-N-(2,2-dimethoxyethyl)aniline (9a). The crude compound was purified by column chromatography (eluent: from 0–30% EtOAc in pet. ether) to give 9a as a colorless oil (2.92 g, 99%) which showed: 1H NMR (500 MHz, CDCl3) δ 3.41 (s, 6H, OCH3), 3.58 (d, J = 5.1 Hz, 2H, NCH2CH

• according to method A. A sample of the crude compound was purified by column chromatography (eluent: from 0% to 10% EtOAc in pet. ether) to give a yellow oil which showed: 1H NMR (500 MHz, CDCl3) δ 2.65 (bs, 1H, OH), 3.39 (dd, J = 2.6, 12.6 Hz, 1H, H3-THIQ), 3.86 (ddd, J = 1.1, 3.8, 12.6 Hz, 1H, H3-THIQ

Direct catalytic arylation of heteroarenes with meso-bromophenyl-substituted porphyrins

• Alexei N. Kiselev,
• Olga K. Grigorova,
• Alexei D. Averin,
• Sergei A. Syrbu,
• Oskar I. Koifman and
• Irina P. Beletskaya

Beilstein J. Org. Chem. 2017, 13, 1524–1532, doi:10.3762/bjoc.13.152

• application of such medicaments are antitumor remedies and non-invasive diagnostic imaging agents for PET, SPECT and MRI methods [5]. The combination of porphyrin and heterocyclic moieties in one molecule is perspective for the design of new compounds with potential powerful pharmaceutical properties. Up to

Glyco-gold nanoparticles: synthesis and applications

• Federica Compostella,
• Olimpia Pitirollo,
• Alessandro Silvestri and
• Laura Polito

Beilstein J. Org. Chem. 2017, 13, 1008–1021, doi:10.3762/bjoc.13.100

• brain. AuNPs were decorated in a controlled ratio with glucose, neuropeptides and a chelator of gallium-68, a sensitive positron emission tomography (PET) tracer, affording the quantification of BBB permeability in healthy small animals. Glyco-gold nanoparticles in immunology The development of

Versatile synthesis of end-reactive polyrotaxanes applicable to fabrication of supramolecular biomaterials

• Atsushi Tamura,
• Asato Tonegawa,
• Yoshinori Arisaka and
• Nobuhiko Yui

Beilstein J. Org. Chem. 2016, 12, 2883–2892, doi:10.3762/bjoc.12.287

• ) contrast agents and positron emission tomography (PET) probes for in vivo studies. Conclusion In this study, we described a novel preparation method for end-reactive PRXs using 3 as an axle polymer for the PRXs. The terminal 2-amino-3-phenylpropyl groups of 3 prevent the dethreading of α-CDs after end

Biochemical and structural characterisation of the second oxidative crosslinking step during the biosynthesis of the glycopeptide antibiotic A47934

• Veronika Ulrich,
• Clara Brieke and
• Max J. Cryle

Beilstein J. Org. Chem. 2016, 12, 2849–2864, doi:10.3762/bjoc.12.284

• . StaF was expressed with an N-terminal hexahistidine-tag and under the control of the T7 promoter. The StaH construct (pET28a StaH) as well as all NRPS constructs (pET MBP-PCPsta-Xsta 1c, pET MBP-PCPtei-Xtei 1c, pET MBP-PCPtei-Xsta 1c, pET MBP-PCPsta-Xtei 1c, pET NCL-4 MBP-Xsta) were employed from a