Fluorescent nucleobase analogues for base–base FRET in nucleic acids: synthesis, photophysics and applications

• Mattias Bood,
• Sangamesh Sarangamath,
• Moa S. Wranne,
• Morten Grøtli and
• L. Marcus Wilhelmsson

Beilstein J. Org. Chem. 2018, 14, 114–129, doi:10.3762/bjoc.14.7

• conjugation. As an effect of the need for hydrogen bonding properties, size restriction and sterical effects these demands are often conflicting [15][18][19]. However, there is an increasing number of exceptions to this and since the pioneering work of Ward et al. on adenine analogues [20] a whole range of

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation and chlorination. Part 2: Use of CF₃SO₂Cl

• Hélène Chachignon,
• Hélène Guyon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2800–2818, doi:10.3762/bjoc.13.273

• partial consumption of the expected product in a side dehydrochlorination reaction. Likewise, the dehydrochlorinated product was recovered exclusively when performing the reaction on 1-phenyl-1,3-butadiene, which tended to indicate that such process was all the more favoured as the conjugation of the

A semisynthesis of 3'-O-ethyl-5,6-dihydrospinosyn J based on the spinosyn A aglycone

• Kai Zhang,
• Shenglan Liu,
• Anjun Liu,
• Hongxin Chai,
• Jiarong Li and
• Lamusi A

Beilstein J. Org. Chem. 2017, 13, 2603–2609, doi:10.3762/bjoc.13.257

• unsaturated bonds were not affected. There is a conjugation between the 13,14-double bond and the carbonyl group, resulting in greater stability of the 13,14-double bond compared to the 5,6-double bond. Thus, the 5,6-double bond can be selectively reduced. Conclusion In summary, we have developed a 7-step

¹⁵N-Labelling and structure determination of adamantylated azolo-azines in solution

• Sergey L. Deev,
• Alexander S. Paramonov,
• Tatyana S. Shestakova,
• Igor A. Khalymbadzha,
• Oleg N. Chupakhin,
• Julia O. Subbotina,
• Oleg S. Eltsov,
• Pavel A. Slepukhin,
• Vladimir L. Rusinov,
• Alexander S. Arseniev and
• Zakhar O. Shenkarev

Beilstein J. Org. Chem. 2017, 13, 2535–2548, doi:10.3762/bjoc.13.250

• membranes. The conjugation of adamantane with heterocyclic compounds also provides a method to modify the pharmacological profile and frequently leads to a new type of bioactivity. For example, N-adamantyl tetrazoles 1 and 2 (Figure 1A) demonstrate lower toxicity and, simultaneously, more potent activity

Pyrene–nucleobase conjugates: synthesis, oligonucleotide binding and confocal bioimaging studies

• Artur Jabłoński,
• Yannic Fritz,
• Hans-Achim Wagenknecht,
• Rafał Czerwieniec,
• Tytus Bernaś,
• Damian Trzybiński,
• Krzysztof Woźniak and
• Konrad Kowalski

Beilstein J. Org. Chem. 2017, 13, 2521–2534, doi:10.3762/bjoc.13.249

• (unresolved) centered at 367 and 360 nm, respectively. The observed changes relative to compounds 4 and 5 and unsubstituted pyrene reflect distinct electronic structure changes of the chromophoric fragment induced by extension of the aromatic system due to conjugation with the carbonyl groups. The pyrene

Solvent-free copper-catalyzed click chemistry for the synthesis of N-heterocyclic hybrids based on quinoline and 1,2,3-triazole

• Martina Tireli,
• Silvija Maračić,
• Stipe Lukin,
• Marina Juribašić Kulcsár,
• Dijana Žilić,
• Mario Cetina,
• Ivan Halasz,
• Silvana Raić-Malić and
• Krunoslav Užarević

Beilstein J. Org. Chem. 2017, 13, 2352–2363, doi:10.3762/bjoc.13.232

• bond bioisosteres made the click reaction a valuable synthetic methodology for conjugation of bioactive molecules [7][8][9] aiming to improve their biological activities [4][10][11]. Discovery of copper(I) ion catalysis in azide–alkyne cycloadditions was decisive for applications of this reaction, as

• quinoline and 1,2,3-triazole scaffolds. Based on the known protocols for click conjugation [39] that include direct utilization of a Cu(I) source as well as alternative creation of Cu(I) from a Cu(II) source or elemental copper, initially we have examined the most common CuAAC reaction procedure using in

Synthesis and application of trifluoroethoxy-substituted phthalocyanines and subphthalocyanines

• Satoru Mori and
• Norio Shibata

Beilstein J. Org. Chem. 2017, 13, 2273–2296, doi:10.3762/bjoc.13.224

• . Keywords: aggregation; fluorine; phthalocyanine; subphthalocyanine; trifluoroethoxy; Introduction Phthalocyanines [1][2][3] are analogues of porphyrin condensed with four isoindoline units via a nitrogen atom and exhibit a deep blue color due to their wide 18π electron conjugation. Among them, the most

• chromatography. The extension of π-conjugation by a palladium-catalyzed cross-coupling reaction after a tetramerization reaction proceeds with high yield. Furthermore, since TFEO-Pcs are not only easy to purify but also do not aggregate, their identification by NMR, MS, UV–vis and IR is easy. Consequently

• conjugation. The electronic interaction between the covalently connected chromophore unit leads to important changes in the absorption spectra and so these dimers are expected to serve as attractive building blocks for the construction of multicomponent photoinduced electron transfer supramolecular systems

Intramolecular glycosylation

• Xiao G. Jia and
• Alexei V. Demchenko

Beilstein J. Org. Chem. 2017, 13, 2028–2048, doi:10.3762/bjoc.13.201

• aglycone delivery helps to enhance the yields while maintaining excellent stereocontrol [84][85]. For example, the Stork group used chlorodimethylsilyl protected acceptor precursor 62 for conjugation to the 2-hydroxy group of donor 61 as shown in Scheme 15. The thiophenyl leaving group of the tethered

Mechanochemical Knoevenagel condensation investigated in situ

• Sebastian Haferkamp,
• Franziska Fischer,
• Werner Kraus and
• Franziska Emmerling

Beilstein J. Org. Chem. 2017, 13, 2010–2014, doi:10.3762/bjoc.13.197

• lower wavenumbers due to a higher conjugation of π-electrons. The extended conjugation is also responsible for the shift of the C≡N stretching band from 2266 to 2233 cm−1 (see Figure 2, yellow and red box). The signal at 2233 cm−1 can be observed after 11 minutes of reaction, indicating that the first p

Solid-state mechanochemical ω-functionalization of poly(ethylene glycol)

• Michael Y. Malca,
• Pierre-Olivier Ferko,
• Tomislav Friščić and
• Audrey Moores

Beilstein J. Org. Chem. 2017, 13, 1963–1968, doi:10.3762/bjoc.13.191

• ], leading to significant improvements in blood circulation half-lives, decrease in clearance rates, and prolonged pharmacological effects [12][13][14]. Derivatives of PEG are often used to perform conjugation reactions on small molecule drugs, proteins, or bioactive nanomaterials [15]. Other methods include

• because of their versatile applicability to covalent conjugation onto various substrates and metal-based nanomaterials. Results and Discussion For this study, we focused on the functionalization of mPEG, which allows the simple mono-functionalization of the polymer, for useful applications to drug

New electroactive asymmetrical chalcones and therefrom derived 2-amino- / 2-(1H-pyrrol-1-yl)pyrimidines, containing an N-[ω-(4-methoxyphenoxy)alkyl]carbazole fragment: synthesis, optical and electrochemical properties

• Daria G. Selivanova,
• Alexei A. Gorbunov,
• Olga A. Mayorova,
• Alexander N. Vasyanin,
• Igor V. Lunegov,
• Elena V. Shklyaeva and
• Georgii G. Abashev

Beilstein J. Org. Chem. 2017, 13, 1583–1595, doi:10.3762/bjoc.13.158

• -carbazoles 3a,b were obtained via acetylation of the same carbazoles 1a,b [20]. The presence of an acetyl group in the resulted compounds 3a and 3b gives the opportunity to extend their conjugation chain via incorporation of an thiophene moiety with the help of a Vilsmeier–Haack–Arnold reaction. The reaction

• 335–370 nm region correspond to the π–π* electron transition arising from the conjugation of the carbonyl group with a C2–C3 double bond and C3 chlorine atom. The broadened absorption maximum in the 460–510 nm region (at the interface between blue and green spectrum regions) characterizes the n–π

• conjugation chain in heterocycles 6 and 8. Further potential sweep demonstrates a broadened oxidation peak (6b: Eox1 = 0.91 V, 7b: Eox1 = 0.95 V, 8b: Eox1 = 1.04 V), which represents the formation of a stable dication of a 6,6’-bicarbazyl structure (Figure 8 and Table 3). In addition to these studies, we have

2-Methyl-2,4-pentanediol (MPD) boosts as detergent-substitute the performance of ß-barrel hybrid catalyst for phenylacetylene polymerization

• Julia Kinzel,
• Daniel F. Sauer,
• Marco Bocola,
• Marcus Arlt,
• Tayebeh Mirzaei Garakani,
• Andreas Thiel,
• Klaus Beckerle,
• Tino Polen,
• Jun Okuda and
• Ulrich Schwaneberg

Beilstein J. Org. Chem. 2017, 13, 1498–1506, doi:10.3762/bjoc.13.148

• indicate the successful conjugation of the catalyst by an increase of the molecular weight of 116 Da corresponding to the maleimide group (Figure 4). In studies with other catalysts attached to FhuA ΔCVFtev, the addition of water to the maleimide ring was observed [10][47]. During digestion or ionization

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

• A. Michael Downey and
• Michal Hocek

Beilstein J. Org. Chem. 2017, 13, 1239–1279, doi:10.3762/bjoc.13.123

Correlation of surface pressure and hue of planarizable push–pull chromophores at the air/water interface

• Frederik Neuhaus,
• Fabio Zobi,
• Gerald Brezesinski,
• Marta Dal Molin,
• Stefan Matile and
• Andreas Zumbuehl

Beilstein J. Org. Chem. 2017, 13, 1099–1105, doi:10.3762/bjoc.13.109

• ]. Mechanical planarization in the ground state increases the conjugation of the push–pull system. As a result, the excitation (or absorption) maximum shifts up to 80 nm to the red [8]. An anionic headgroup is added to produce an amphiphile that self-assembles into monolayers and micelles and enters

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

• employed for this purpose (i.e., click reaction, amidation, conjugation via carbonyldiimidazol and perfluorophenyl azide (PFPA) photo-coupling) have to be compatible with water, the common medium for AuNP preparation [25][26][27][28][29]. One example of the three-step approach was described by Tian and co

Molecular-level architectural design using benzothiadiazole-based polymers for photovoltaic applications

• Vinila N. Viswanathan,
• Arun D. Rao,
• Upendra K. Pandey,
• Arul Varman Kesavan and
• Praveen C. Ramamurthy

Beilstein J. Org. Chem. 2017, 13, 863–873, doi:10.3762/bjoc.13.87

• significant role in increasing the efficiency for OPVs [30][31]. However, fused π-bridges (such as thienothiophene) having a larger molecular structure and higher degree of conjugation are less explored with respect to thiophene and furan spacers. Thienothiophene ensures a highly delocalized electron system

• and donor, respectively [35][36]. The acceptor motif was further coupled with thiophene to increase the conjugation length and absorption. The same acceptor moiety was substituted with fluorine and the effect of this substitution on the polymeric and photovoltaic properties was studied. Furthermore

• , the effect of planarity and conjugation extension on the polymer backbone was also studied by coupling with a fused thienothiophene moiety. Results and Discussion For the synthesis of polymers with alternating donor–acceptor–donor architecture, suitable monomers were first prepared (Scheme 1). The

Synthesis of D-manno-heptulose via a cascade aldol/hemiketalization reaction

• Yan Chen,
• Xiaoman Wang,
• Junchang Wang and
• You Yang

Beilstein J. Org. Chem. 2017, 13, 795–799, doi:10.3762/bjoc.13.79

• evaluation of carbohydrate–lectin interactions by conjugation with fluorescent quantum dots via click chemistry [13][14]. Besides, differentially protected D-manno-heptulose building blocks could serve as valuable precursors for the synthesis of C-glycosides [15][16]. The known synthesis of D-manno-heptulose

Fluorescent carbon dots from mono- and polysaccharides: synthesis, properties and applications

• Stephen Hill and
• M. Carmen Galan

Beilstein J. Org. Chem. 2017, 13, 675–693, doi:10.3762/bjoc.13.67

• -octadecene) that could subsequently be functionalised with hydrophilic PEG-diamine, providing an amine functionality for conjugation with glucosamine, histidine, arginine and folate. The yellow/red emissive loaded-CDs were shown to be viable bioimaging probes in live cells, since their emission did not

• carboxylic acids that could be functionalised. Surface conjugation with PEG-diamine afforded a steric blocking, enhanced permeation and retention (EPR) shell, whilst providing an amine functionality for further surface conjugation. The anticancer drug methotrexate (MTX), which is a well-studied drug used to

Novel β-cyclodextrin–eosin conjugates

• Gábor Benkovics,
• Damien Afonso,
• András Darcsi,
• Szabolcs Béni,
• Sabrina Conoci,
• Éva Fenyvesi,
• Lajos Szente,
• Milo Malanga and
• Salvatore Sortino

Beilstein J. Org. Chem. 2017, 13, 543–551, doi:10.3762/bjoc.13.52

• xanthene-type PSs in conjugation with CDs is very scarce. The reasons behind this fact are most probably the difficulties in selective CD functionalization and limitations in xanthene-dye modification. Xanthene dyes can be introduced into the CD scaffold most easily through an ester linkage between the

• -yl)-4-methylmorpholinium chloride (DMTMMCl), a coupling reagent frequently used in peptide synthesis. Malanga et al. recently reported on the preparation of xanthene-dye-appended CDs with the most commonly used fluorescent probes rhodamine and fluorescein (Flu, 1). The conjugation of the 6-monoamino

• -CD conjugates The condensation reaction between 6-monoamino-β-CD and the synthesized dyes 2 and 4 is shown in Figure 2. The reaction is promoted by the coupling agent DMTMMCl that enables an effective conjugation in water under mild reaction conditions (room temperature). Since a successful

Brønsted acid-mediated cyclization–dehydrosulfonylation/reduction sequences: An easy access to pyrazinoisoquinolines and pyridopyrazines

• Ramana Sreenivasa Rao and
• Chinnasamy Ramaraj Ramanathan

Beilstein J. Org. Chem. 2017, 13, 428–440, doi:10.3762/bjoc.13.46

• 3-factors, such as, (i) extended conjugation in pyrazinones, (ii) good leaving capacity of the benzenesulfonyl group and (iii) the presence of an acidic proton which is α to the amide carbonyl group. Hence, we believe that the selective elimination of the sulfonyl group in refluxing methanol would

Posttranslational isoprenylation of tryptophan in bacteria

• Masahiro Okada,
• Tomotoshi Sugita and
• Ikuro Abe

Beilstein J. Org. Chem. 2017, 13, 338–346, doi:10.3762/bjoc.13.37

• -terminal cysteine (Figure 1B) [9][10]. Each pheromone causes the opposite type of cell to induce the reciprocal conjugation of the heterothallic cells, through the formation of a conjugation tube for mating. A structure–activity relationship study on tremerogen A-10 demonstrated that both the amino acid

• sequence and the hydrophobic side chain were essential for the initiation of the conjugation tube formation [11]. Soon thereafter, the consensus sequence for the isoprenylation of the cysteine in the precursor peptide was identified as the CaaX motif, in which "a" refers to an aliphatic amino acid and "X

• post-translational isoprenylation of tryptophan. (A) Schematic representation of pheromone-induced conjugation tube formation for mating in Tremella mesenterica. (B) Chemical structures of tremerogens A-10 and a-13. The isoprenyl side chains are shown in red. (C) C-terminal amino acid sequences of the

Synthesis and optical properties of new 5'-aryl-substituted 2,5-bis(3-decyl-2,2'-bithiophen-5-yl)-1,3,4-oxadiazoles

• Anastasia S. Kostyuchenko,
• Tatyana Yu. Zheleznova,
• Anton J. Stasyuk,
• Aleksandra Kurowska,
• Wojciech Domagala,
• Adam Pron and
• Alexander S. Fisyuk

Beilstein J. Org. Chem. 2017, 13, 313–322, doi:10.3762/bjoc.13.34

• derivative 15b (2.81 eV). This rather weak dependence of the band gap on the aromatic substituent size observed for compounds 15d–g, can be explained by two opposite effects which partly compensate each other: larger substituents increase the number of π-bonds being in conjugation but at the same time they

• induce non-planarity due to steric hindrance, which lowers the effective conjugation. This problem will be discussed in detail in the section devoted to quantum chemical calculations. When excited by UV light, all studied compounds emit blue (468, 473 nm) or bluish-green (499, 501) light (Table 2

• 88°) [29]. This dihedral angle is “a compromise” between the conjugation of the adjacent segments which favors the molecule’s planarity and steric hindrance effects which induce torsion. In the case of larger sized substituents, the steric effect predominates leading to large values of dihedral

Regiochemistry of cyclocondensation reactions in the synthesis of polyazaheterocycles

• Patrick T. Campos,
• Leticia V. Rodrigues,
• Andrei L. Belladona,
• Caroline R. Bender,
• Juliana S. Bitencurt,
• Fernanda A. Rosa,
• Davi F. Back,
• Helio G. Bonacorso,
• Nilo Zanatta,
• Clarissa P. Frizzo and
• Marcos A. P. Martins

Beilstein J. Org. Chem. 2017, 13, 257–266, doi:10.3762/bjoc.13.29

• isomeric product 9b (see structures in the Supporting Information File 1). Additionally, it was observed that the nitrogen atom farthest from the substituent is the most nucleophilic. The better conjugation of methyl (hyperconjugation effect) and chlorine (+M effect) substituents in the para-position could

Interactions between photoacidic 3-hydroxynaphtho[1,2-b]quinolizinium and cucurbit[7]uril: Influence on acidity in the ground and excited state

• Jonas Becher,
• Daria V. Berdnikova,
• Darinka Dzubiel,
• Heiko Ihmels and
• Phil M. Pithan

Beilstein J. Org. Chem. 2017, 13, 203–212, doi:10.3762/bjoc.13.23

• in a merocyanine-type conjugation (Scheme 2). A similar effect was postulated for the structurally resembling hydroxystyrylquinolizinium derivatives, such as 6 (Figure 8), that also show a red shift of the absorption upon deprotonation, although to a larger extent (from 405 to 472 nm) [50][51][52

Benzothiadiazole oligoene fatty acids: fluorescent dyes with large Stokes shifts

• Lukas J. Patalag and
• Daniel B. Werz

Beilstein J. Org. Chem. 2016, 12, 2739–2747, doi:10.3762/bjoc.12.270

• same length, but of more extended conjugation we made use of the Horner–Wadsworth–Emmons (HWE) reaction. Phosphonate 4 was reacted with the respective aldehyde 1. In a facile three-step one-pot process the emerging α,β-unsaturated ester 5 was immediately converted to the alcohol 6 in 87% yield in the