Identification of optimal fluorescent probes for G-quadruplex nucleic acids through systematic exploration of mono- and distyryl dye libraries

• Xiao Xie,
• Michela Zuffo,
• Marie-Paule Teulade-Fichou and
• Anton Granzhan

Beilstein J. Org. Chem. 2019, 15, 1872–1889, doi:10.3762/bjoc.15.183

• and Table 1), in order to achieve a satisfactory level of solubility in aqueous buffer (i.e., no visible precipitation at a dye concentration of 10 µM in K-100 buffer: 10 mM LiAsO2Me2, 100 mM KCl, pH 7.2). Dyes containing side-chain substituents (2a–6a) were obtained directly as bromide salts

• absorption bands of most dyes are blue-shifted by 10 to 30 nm and undergo a hypochromic effect, compared with organic solvents such as MeOH or DMSO. This behavior evidences a more or less significant aggregation propensity of dyes in aqueous medium, even though, in all tested cases, no visible precipitation

Halide metathesis in overdrive: mechanochemical synthesis of a heterometallic group 1 allyl complex

• Ross F. Koby,
• Nicholas R. Rightmire,
• Nathan D. Schley,
• Timothy P. Hanusa and
• William W. Brennessel

Beilstein J. Org. Chem. 2019, 15, 1856–1863, doi:10.3762/bjoc.15.181

• in general a solvent is not required, in solution environments the formation of products is assisted if the solubility of MX or RnM' is limited, as their precipitation helps shift the equilibrium toward the product side. If ethers are used as solvents, for example, the low solubility of MX can be

Bambusuril analogs based on alternating glycoluril and xylylene units

• Tomáš Lízal and
• Vladimír Šindelář

Beilstein J. Org. Chem. 2019, 15, 1268–1274, doi:10.3762/bjoc.15.124

• significant effect on the distribution of macrocycle homologues probably due to the non-reversible nature of the reaction. However, the salt was used as it facilitated precipitation of the crude product after aqueous work-up. The MALDI analysis (Supporting Information File 1, Figure S1) indicated that the

Ugi reaction-derived prolyl peptide catalysts grafted on the renewable polymer polyfurfuryl alcohol for applications in heterogeneous enamine catalysis

• Alexander F. de la Torre,
• Gabriel S. Scatena,
• Oscar Valdés,
• Daniel G. Rivera and
• Márcio W. Paixão

Beilstein J. Org. Chem. 2019, 15, 1210–1216, doi:10.3762/bjoc.15.118

• out with a concentrated basic solution. The use of a 1 M NaOH (5 mL) solution requires two washes of 10 min each but at the end of the reaction an emulsion may appear. In order to avoid this problem an excess of 0.1 M NaOH solution was used. Polymers were isolated by precipitation in petroleum ether

• , 175.5. PFA-supported catalyst 3. Compound 1 (476 mg, 1 mmol, 1.0 equiv), furfuryl alcohol (860 µL, 10 mmol, 10 equiv) and TFA (38 µL, 0.5 mmol) were reacted in CHCl3 (5 mL) according to the general procedure B. After precipitation in petroleum ether, polymer 3 was obtained as a black amorphous solid. IR

• , 0.5 mmol) were reacted in CHCl3 (5 mL) according to the general procedure B. After precipitation in petroleum ether, polymer 4 was obtained as a black amorphous solid. IR (KBr, cm−1): 3500, 3120, 2930, 1720, 1680, 1610, 1550, 1420, 1350, 1200, 1160, 1110, 1038, 780, 740, 600; microanalysis: N (1.36

Mechanochemical synthesis of hyper-crosslinked polymers: influences on their pore structure and adsorption behaviour for organic vapors

• Sven Grätz,
• Sebastian Zink,
• Hanna Kraffczyk,
• Marcus Rose and
• Lars Borchardt

Beilstein J. Org. Chem. 2019, 15, 1154–1161, doi:10.3762/bjoc.15.112

• interesting adsorbents with a dynamic adsorption behaviour. However, the low solubility of POPs is a main challenge in their synthesis protocols. Solution-based procedures, for example, suffer from almost instant precipitation and thus only produce materials with a low degree of polymerization [10]. In the

Design of a double-decker coordination cage revisited to make new cages and exemplify ligand isomerism

• Sagarika Samantray,
• Sreenivasulu Bandi and
• Dillip K. Chand

Beilstein J. Org. Chem. 2019, 15, 1129–1140, doi:10.3762/bjoc.15.109

• those performed in DMSO were used for isolation of the complex by precipitation methods. The resulting complexes at specified ratios of the reactants are depicted in Scheme 1 and the details of the complexation behavior are described below. Complexation of cis-protected palladium(II) with ligand L1 at 1

• repeated in DMSO and the (PdL’)L-type complex [Pd(tmeda)(L1)](NO3)2 (1a, Scheme 1(i)) was isolated from the reaction mixture by a precipitation method that is described in the experimental section. The 1H NMR spectrum of the solution showed formation of a single discrete complex (Figure 2(ii)). Counter

• discrete complex. The reaction was repeated in DMSO and the PdL2-type complex [Pd(L1)2](NO3)2 (3a, Scheme 1c) was isolated from the reaction mixture by precipitation as described in the experimental section. Counter-anion (BF4−, ClO4− and OTf−) variation was also carried out to successfully prepare a

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• modified literature procedure (Scheme 3) [22]. The modification consists in the addition of a 10% molar excess of 4-(aza-15-crown-5)benzocarbaldehyde (3, Scheme 3) and usage of ethyl acetate as an additional solvent for product precipitation. Because of its better solubility in ethyl acetate the unreacted

• precipitation from ethanol/ethyl acetate 1:3 was needed to obtain analytically pure target dyes 4a–d. The dyes 4a and 4c were previously described [18][21] and were used as reference compounds. To the best of our knowledge dyes 4b and 4d are new compounds. The chemical structures of all dyes from the series

A chemically contiguous hapten approach for a heroin–fentanyl vaccine

• Yoshihiro Natori,
• Candy S. Hwang,
• Lucy Lin,
• Lauren C. Smith,
• Bin Zhou and
• Kim D. Janda

Beilstein J. Org. Chem. 2019, 15, 1020–1031, doi:10.3762/bjoc.15.100

• coating the protein’s surface (i.e., 10.0 copies). However, increasing the conjugation to a 1 mg scale caused the protein to precipitate immediately upon addition of HF-1 in 9:1 DMF/H2O solution, eliminating the possibility of conjugation. To mitigate this precipitation problem, glycerol was added to the

• ameliorate protein precipitation and conjugation issues. The linker placement at the phenethyl position greatly improved conjugation compared to the other phenylamide group; HF-4 had a hapten density of 21.1, drastically higher than HF-2 (hapten density: 12.6) and HF-3 (hapten density: 8.3). Gratifyingly, we

Fabrication, characterization and adsorption properties of cucurbit[7]uril-functionalized polycaprolactone electrospun nanofibrous membranes

• Changzhong Chen,
• Fengbo Liu,
• Xiongzhi Zhang,
• Zhiyong Zhao and
• Simin Liu

Beilstein J. Org. Chem. 2019, 15, 992–999, doi:10.3762/bjoc.15.97

• solvent for PCL. Turbidity/precipitation was observed when the volume ratio of the formic acid solution of CB[n] in the mixed solution was higher than 20% due to the poor solubility of PCL in formic acid solution. In order to keep the CB[n] content in the mixed solution as large as possible, the ratio of

Synthesis of polydicyclopentadiene using the Cp₂TiCl₂/Et₂AlCl catalytic system and thin-layer oxidation of the polymer in air

• Zhargolma B. Bazarova,
• Ludmila S. Soroka,
• Alex A. Lyapkov,
• Мekhman S. Yusubov and
• Francis Verpoort

Beilstein J. Org. Chem. 2019, 15, 733–745, doi:10.3762/bjoc.15.69

• , which reacts with R-olefin and a Lewis base to form stable crystalline titanacyclobutanes. Both titanium carbene and titanacycles are ROMP catalysts (Scheme 4). PDCPD polymers were obtained by precipitation in ethanol, dried and characterized by FTIR, NMR, and GPC. Figure 6 displays a typical infrared

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• polymer was isolated by precipitation. As a result two block copolymers were obtained. The one containing 5% of POSS units was characterized by Mn = 26200 Da and PDI = 1.16 and the other one bearing 10% of POSS-substituted monomeric units, has a number average molecular weight Mn = 33200 Da and a

A convenient and practical synthesis of β-diketones bearing linear perfluorinated alkyl groups and a 2-thienyl moiety

• Ilya V. Taydakov,
• Yuliya M. Kreshchenova and
• Ekaterina P. Dolotova

Beilstein J. Org. Chem. 2018, 14, 3106–3111, doi:10.3762/bjoc.14.290

• ]. This compound was first obtained by Reid and Calvin in 1950 [15] by Claisen condensation of 2-acetylthiophene and ethyl trifluoroacetate in the presence of NaOEt in Et2O (Scheme 1). The purification procedure was laborious and included copper chelate precipitation and its subsequent acid decomposition

• optimization of reaction conditions was made for aliphatic esters. Since the Claisen condensation is accompanied by formation of side products, purification of a diketone is usually difficult. Steam distillation of the reaction mixture followed by precipitation of metal (Cu, Mg, Mn, Fe) chelates and their

• acidic decomposition [22][23] or preparative chromatography [33][34] were used to obtain a pure product. We have found that in most cases, simple vacuum distillation of the crude reaction mixture is sufficient to obtain pure β-diketones with fluorinated side-chain. Nevertheless, precipitation of the Cu

Green synthesis of new chiral 1-(arylamino)imidazo[2,1-a]isoindole-2,5-diones from the corresponding α-amino acid arylhydrazides in aqueous medium

• Nadia Bouzayani,
• Jamil Kraїem,
• Sylvain Marque,
• Yakdhane Kacem,
• Abel Carlin-Sinclair,
• Jérôme Marrot and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2018, 14, 2923–2930, doi:10.3762/bjoc.14.271

• aspect. Once more, the processing includes this eco-friendly way up to have the compounds in hand since simple precipitation allows to isolate the nitrogenated tricyclic compounds; no purification is needed. The model for the key step of the cyclization clearly explains the stereochemistries, which are

Copolymerization of epoxides with cyclic anhydrides catalyzed by dinuclear cobalt complexes

• Yo Hiranoi and
• Koji Nakano

Beilstein J. Org. Chem. 2018, 14, 2779–2788, doi:10.3762/bjoc.14.255

• under standard conditions using (R,R,R,R)-1. The reaction mixture was diluted with CH2Cl2 and quenched with several drops of MeOH/1 M HCl (50:50 vol %). The resulting mixture was poured into an excess of MeOH to precipitate the copolymer. After the precipitation was repeated two more times, the

Synthesis of a tyrosinase inhibitor by consecutive ethenolysis and cross-metathesis of crude cashew nutshell liquid

• Jacqueline Pollini,
• Valentina Bragoni and
• Lukas J. Gooßen

Beilstein J. Org. Chem. 2018, 14, 2737–2744, doi:10.3762/bjoc.14.252

• of the entire mixture and subsequent selective precipitation of 6-(ω-nonenyl)salicylic acid from cold pentane. The olefinic side chain of this intermediate was elongated by its cross-metathesis with 1-hexene using a first generation Hoveyda–Grubbs catalyst, which was reused as precatalyst in a

• anacardic acid (1) is even more attractive, because it contains an additional functional group. However, the separation and purification of this CNSL component without decarboxylation is laborious and relies on wasteful and tedious processes such as fractionate precipitation or column chromatography [6][17

• precipitation of the desired product 2 as a colorless solid in an amount that is equivalent to 80% of the anacardic acid content or 84% of the unsaturated anacardic acid. Anacardic acid makes up for ca. 70% of the CNSL, so that the yield is 56% based on the entire CNSL. We were pleased to find that the

Quinolines from the cyclocondensation of isatoic anhydride with ethyl acetoacetate: preparation of ethyl 4-hydroxy-2-methylquinoline-3-carboxylate and derivatives

• Nicholas G. Jentsch,
• Jared D. Hume,
• Emily B. Crull,
• Samer M. Beauti,
• Amy H. Pham,
• Julie A. Pigza,
• Jacques J. Kessl and
• Matthew G. Donahue

Beilstein J. Org. Chem. 2018, 14, 2529–2536, doi:10.3762/bjoc.14.229

• stirring, the mixture became homogenous followed by precipitation of a pale white solid. The solid was collected by vacuum filtration on a Büchner funnel (7.6 cm diameter) with Whatman #1 filter paper (70 mm) and air pulled through for 5 minutes. The material was transferred to a 250 mL Erlenmeyer flask

Dynamic light scattering studies of the effects of salts on the diffusivity of cationic and anionic cavitands

• Anthony Wishard and
• Bruce C. Gibb

Beilstein J. Org. Chem. 2018, 14, 2212–2219, doi:10.3762/bjoc.14.195

• akin to how these anions can partially unfold proteins. Alternatively, poorly solvated anions can also associate closely with cationic groups, induce charge neutralization, and engender aggregation and/or precipitation. In other words, they can also cause an apparent increase in the hydrophobic effect

• well recognized to interact strongly with carboxylates and induce aggregation [25]. Thus, visual inspection upon the addition of ZnCl2 to give a 100 mM salt concentration revealed extensive precipitation of the host. Returning to the point that the majority of anionic groups in biomacromolecules are

• strongly solvated, it is interesting to contemplate the idea that the prevalence of alkali metal ions in the environment exerted evolutionary pressures on biomacromolecules to select carboxylate, phosphates and sulfates and hence minimize ion pairing, charge neutralization, and deleterious precipitation

Selective formation of a zwitterion adduct and bicarbonate salt in the efficient CO₂ fixation by N-benzyl cyclic guanidine under dry and wet conditions

• Yoshiaki Yoshida,
• Naoto Aoyagi and
• Takeshi Endo

Beilstein J. Org. Chem. 2018, 14, 2204–2211, doi:10.3762/bjoc.14.194

• the precipitation of 2 in CH3CN, and then the only part of 2 was transformed to 3 after stirring in CH3CN containing an excess mole of water, although 2 and 3 were insoluble in organic solvents. This result means that 2 is hydrophobic enough to be isolated as an individual compound. On the other hand

Synthesis and post-functionalization of alternate-linked-meta-para-[2ⁿ.1ⁿ]thiacyclophanes

• Wout De Leger,
• Koen Adriaensen,
• Koen Robeyns,
• Luc Van Meervelt,
• Joice Thomas,
• Björn Meijers,
• Mario Smet and
• Wim Dehaen

Beilstein J. Org. Chem. 2018, 14, 2190–2197, doi:10.3762/bjoc.14.192

• , we report our method of choice to selectively synthesize 7. Purification of [3 + 3] adduct 7 was successful via precipitation (CHCl3/MeOH) in good yield (64%). Proposed mechanism and stability In Scheme 3 a reaction mechanism for the formation of the macrocycles is proposed. It is believed that after

Efficient catenane synthesis by cucurbit[6]uril-mediated azide–alkyne cycloaddition

• Antony Wing Hung Ng,
• Chi-Chung Yee,
• Kai Wang and
• Ho Yu Au-Yeung

Beilstein J. Org. Chem. 2018, 14, 1846–1853, doi:10.3762/bjoc.14.158

• white solid by precipitation with a saturated NH4PF6 solution and simple filtration. The ESIMS spectrum showed two peaks at m/z = 808.5 and 1076.3, consistent with the 3+ and 4+ ions of Cat-1. Similar to Cat-0, the MS2 spectrum of Cat-1 revealed CB[6]-bound fragments, showing the strong CB[6]–ammonium

• various types of building blocks. Because of the high yields of these [3]catenanes, their isolations were all straightforward. Cat-2–Cat-10 were isolated either by precipitation as the PF6− salts or by preparative HPLC, and were fully characterized by MS, NMR and UV–vis spectroscopy. Similar to Cat-1, the

• study. Synthesis of Cat-1 by CBAAC. aAssembly yield by HPLC; bisolated yield as PF6− salt. Synthesis of [3]catenanes by CBAAC. aAssembly yield by HPLC; bisolated yield by precipitation as PF6− salt; cisolated yield by preparative HPLC. Synthesis of the [4]catenane Cat-11. aAssembly yield by HPLC

Polysubstituted ferrocenes as tunable redox mediators

• Sven D. Waniek,
• Jan Klett,
• Christoph Förster and
• Katja Heinze

Beilstein J. Org. Chem. 2018, 14, 1004–1015, doi:10.3762/bjoc.14.86

• of 1.1 V and 1.4 V, respectively, probably due to a fast diffusion of 3 and 4 to the anode in the beam path (Figure 4, Figures S11–S14, Supporting Information File 1). In addition, precipitation of some poorly soluble [4][X] also occurs. During oxidation to the respective ferrocenium cations, the C=O

• Information File 1). Probably, precipitation of the poorly soluble tetraester 4+ could be responsible for this effect, as already suggested for the IR-SEC experiments of 4/4+. On the other hand, isosbestic points are observed in the UV–vis spectra upon re-reduction of 4+ to 4 (Figure S31, Supporting

Phosphodiester models for cleavage of nucleic acids

• Satu Mikkola,
• Tuomas Lönnberg and
• Harri Lönnberg

Beilstein J. Org. Chem. 2018, 14, 803–837, doi:10.3762/bjoc.14.68

Synthesis and in vitro biochemical evaluation of oxime bond-linked daunorubicin–GnRH-III conjugates developed for targeted drug delivery

• Sabine Schuster,
• Beáta Biri-Kovács,
• Bálint Szeder,
• Viktor Farkas,
• László Buday,
• Zsuzsanna Szabó,
• Gábor Halmos and
• Gábor Mező

Beilstein J. Org. Chem. 2018, 14, 756–771, doi:10.3762/bjoc.14.64

• aminooxyacetic acid as “carbonyl capture” reagent (2 h, at room temperature (rt)) resulted in the simultaneous removal of the side chain protecting groups and the cleavage of the peptide from the resin [54]. Peptides were isolated by precipitation with ice-cold Et2O, centrifuged, washed 3 times, dissolved in

An uracil-linked hydroxyflavone probe for the recognition of ATP

• Márton Bojtár,
• Péter Zoltán Janzsó-Berend,
• Dávid Mester,
• Dóra Hessz,
• Mihály Kállay,
• Miklós Kubinyi and
• István Bitter

Beilstein J. Org. Chem. 2018, 14, 747–755, doi:10.3762/bjoc.14.63

• constants in the range of 0.3–3∙103 M−1, considerably lower values. The effect of γ-cyclodextrin was examined in some preliminary experiments. Lowering the concentration to 0.05 mM resulted in unreliable spectra due to possible precipitation of the complex. A higher cyclodextrin concentration resulted in

• spectrum was measured after reaching the equilibrium (5 minutes), and by using γ-cyclodextrin, it was stable over a longer period of time. Since the spectra of UHF and UHF∙ATP did not change upon addition of γ-cyclodextrin in pure HEPES buffer (measurement performed before precipitation), it is unlikely

Investigating radical cation chain processes in the electrocatalytic Diels–Alder reaction

• Yasushi Imada,
• Yohei Okada and
• Kazuhiro Chiba

Beilstein J. Org. Chem. 2018, 14, 642–647, doi:10.3762/bjoc.14.51

• M and 2.0 M concentrations of trans-anethole (1, Table 2, entries 1 and 2). However, 5.0 M was too concentrated and caused precipitation of the supporting electrolyte (Table 2, entry 3). To our satisfaction, up to 4.15 g of the Diels–Alder adduct (3) was isolated with 0.03 F/mol, giving a current