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

An alternative to hydrogenation processes. Electrocatalytic hydrogenation of benzophenone

• Cristina Mozo Mulero,
• Alfonso Sáez,
• Jesús Iniesta and
• Vicente Montiel

Beilstein J. Org. Chem. 2018, 14, 537–546, doi:10.3762/bjoc.14.40

• using NaBH4 as reducing agent in a water-in-oil (w/o) microemulsion in the presence of polyethylene glycol hexadecyl ether, Brij@30 as capping agent and n-heptane as organic solvent (water/Brij@30/n-heptane). After precipitation and copiously washing with acetone and water, Pd nanoparticles were

Synthetic and semi-synthetic approaches to unprotected N-glycan oxazolines

• Antony J. Fairbanks

Beilstein J. Org. Chem. 2018, 14, 416–429, doi:10.3762/bjoc.14.30

• partially purified by acetone precipitation and extraction with 60% methanol. The crude N-glycans were found to be a rather complex mixture of compounds, the four major components of which were identified as triantennary glycans with 2 or 3 sialic acids attached as regioisomers (i.e., both α(2–6)- and α(2–3

Preparation of trinucleotide phosphoramidites as synthons for the synthesis of gene libraries

• Ruth Suchsland,
• Bettina Appel and
• Sabine Müller

Beilstein J. Org. Chem. 2018, 14, 397–406, doi:10.3762/bjoc.14.28

• ) has a prominent position, appearing as the routinely used polymer [40][41][42][43][44]. The isolation of intermediate and final products from the reaction mixture proceeds by precipitation from diethyl ether and filtration, thus significantly speeding up the process. In addition, the method is

• , entry 1). Upon detritylation, the support carrying the start nucleoside now having a free 5'-OH group was precipitated from methanol, followed by coupling with a 5'-O-DMTr-protected nucleoside-3'-O-(o-chlorophenyl)phosphate activated as benzotriazol and renewed precipitation with methanol. The resulting

• dimer was then extended to the trimer by another cycle of detritylation, precipitation, coupling and precipitation. During reductive cleavage of the disulfide bond to release the fully protected trimer from the support, unfortunately the loss of the 5'-DMTr group was observed. To overcome this hurdle

Continuous-flow retro-Diels–Alder reaction: an efficient method for the preparation of pyrimidinone derivatives

• Imane Nekkaa,
• Márta Palkó,
• István M. Mándity and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2018, 14, 318–324, doi:10.3762/bjoc.14.20

• % methanolic solution in water was added to get precipitation. The solid was filtered off and washed with water to get di-endo-3-phenyl-4a,5,8,8a-tetrahydro-5,8-ethanoquinazolin-4(3H)-one (15b). All spectroscopic data of the alternately synthesized compound were the same as those obtained by the flow chemical

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

• yields, was effectively obtained in 86% yield by using an excess of KF in ethanol and microwave heating at 140 °C. Conveniently, at the same time all the three acetyl protecting groups were cleaved and the free nucleobase was isolated via precipitation. A 5´-DMTr protection followed by 2´-TBDMS

Polarization spectroscopy methods in the determination of interactions of small molecules with nucleic acids – tutorial

• Tamara Šmidlehner,
• Ivo Piantanida and
• Gennaro Pescitelli

Beilstein J. Org. Chem. 2018, 14, 84–105, doi:10.3762/bjoc.14.5

• at a concentration of about 0.001 M. The prepared solution should be clear and homogeneous with no visible precipitation or opalescence. If the ligand is poorly soluble in water, other solvents can be used, but some of them may interfere by absorbing light and raising the wavelength cut-off, as well

• increase in the cuvette, usually best seen in the long-wavelength range of the spectrum, is a clear evidence of precipitation or colloid/aggregate formation in the cuvette, which completely hampers further experiments. The characterization of the thermal stability of the ligand solution by collecting it’s

Recent applications of click chemistry for the functionalization of gold nanoparticles and their conversion to glyco-gold nanoparticles

• Vivek Poonthiyil,
• Thisbe K. Lindhorst,
• Vladimir B. Golovko and
• Antony J. Fairbanks

Beilstein J. Org. Chem. 2018, 14, 11–24, doi:10.3762/bjoc.14.2

• File 1, Figure S5). Furthermore TEM revealed partial aggregation of the particles (Supporting Information File 1, Figure S6). However, despite this partial aggregation the ATT-AuNP solution was stable without any precipitation at least for three months when stored at 4 °C. Similar observations have

• obtained. In further experiments the CuAAC was attempted using a solution of purified GlcNAc azide 34. Water and THF were used as the solvent in a 1:1 ratio to be in line with the conditions reported by Boisselier et al. [62]. However, even with these conditions precipitation of the particles could not be

• , it may be that although the conditions reported by Boisselier et al. work well for smaller sized particles, however, may not be enough to overcome the precipitation of the larger sized AuNPs (>10 nm) caused by Cu as observed by some groups. Unfortunately our attempts to synthesize smaller sized (≈2

Binding abilities of polyaminocyclodextrins: polarimetric investigations and biological assays

• Marco Russo,
• Daniele La Corte,
• Annalisa Pisciotta,
• Serena Riela,
• Rosa Alduina and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2017, 13, 2751–2763, doi:10.3762/bjoc.13.271

• is concerned, analysis of the composition of the aggregates, as accounted for by nr values, enabled us to evidence i) the effect of inorganic electrolytes, which ensure charge counterbalance, resulting in low ζ-potential and precipitation and ii) the effect of the structure of the polyamine branches

A novel synthetic approach to hydroimidazo[1,5-b]pyridazines by the recyclization of itaconimides and HPLC–HRMS monitoring of the reaction pathway

• Dmitry Yu. Vandyshev,
• Khidmet S. Shikhaliev,
• Andrey Yu. Potapov,
• Michael Yu. Krysin,
• Fedor I. Zubkov and
• Lyudmila V. Sapronova

Beilstein J. Org. Chem. 2017, 13, 2561–2568, doi:10.3762/bjoc.13.252

• probable routes of the cascade recyclization process, because ions of the protonable substances are only fixed in the given ESI–MS conditions, and precipitation of the product is observed as the reaction proceeds. The latter causes a decreased content of the imidazopyridazine 9d in the liquid phase is

Synthesis and supramolecular properties of regioisomers of mononaphthylallyl derivatives of γ-cyclodextrin

• Markéta Bláhová,
• Sergey K. Filippov,
• Lubomír Kováčik,
• Jiří Horský,
• Simona Hybelbauerová,
• Zdenka Syrová,
• Tomáš Křížek and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2017, 13, 2509–2520, doi:10.3762/bjoc.13.248

• quite soluble in water, turbidity becomes noticeable after a longer time, and in the case of 100 mM specimens, even precipitation of a solid was observed. The turbidity caused the worse quality of 1H NMR spectra; however, chemical shifts and changes in the shape of the peaks are clearly visible. For the

• ) Interactions between naphthyl groups (stacking) leading to micellization or aggregation. (c) Inclusion complexation of naphthyl into the CD cavity leading to supramolecular polymerization. (d) Free 2c. (e) Interaction between CD moieties leading to aggregation or precipitation. Preparation of 2I-O-, 3I-O- and

Syntheses, structures, and stabilities of aliphatic and aromatic fluorous iodine(I) and iodine(III) compounds: the role of iodine Lewis basicity

• Tathagata Mukherjee,
• Soumik Biswas,
• Andreas Ehnbom,
• Subrata K. Ghosh,
• Ibrahim El-Zoghbi,
• Nattamai Bhuvanesh,
• Hassan S. Bazzi and
• John A. Gladysz

Beilstein J. Org. Chem. 2017, 13, 2486–2501, doi:10.3762/bjoc.13.246

• , such as precipitation (e.g., the conversion of I-Me to II-Me in Scheme 1), or kinetic barriers (inertness of RfOxCH2I in Scheme 3 or the precursor to V in Scheme 1). With the fluorous iodides, the extent of chlorination generally provides a measure of the degree to which the electron-withdrawing

Is the tungsten(IV) complex (NEt₄)₂[WO(mnt)₂] a functional analogue of acetylene hydratase?

• Matthias Schreyer and
• Lukas Hintermann

Beilstein J. Org. Chem. 2017, 13, 2332–2339, doi:10.3762/bjoc.13.230

• -Markovnikov hydration [18][24][25][26][27][28]. Results and Discussion Tungsten complex (NEt4)2[WO(mnt)2] (1) was prepared according to the literature procedure from Na2WO4, Na2mnt and buffered aqueous dithionite, followed by precipitation with Et4NBr (Scheme 3a) [29]. The compound was characterized by 1H and