Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• synthesis of differently substituted ketoesters 3 with good to high enantioselectivities by using just 2 mol % of the bifunctional catalyst. Very interestingly, Shi’s group very recently also reported PEG-bound derivatives of these catalysts which performed more or less equally selective for this

An efficient Pd–NHC catalyst system in situ generated from Na₂PdCl₄ and PEG-functionalized imidazolium salts for Mizoroki–Heck reactions in water

• Nan Sun,
• Meng Chen,
• Liqun Jin,
• Wei Zhao,
• Baoxiang Hu,
• Zhenlu Shen and
• Xinquan Hu

Beilstein J. Org. Chem. 2017, 13, 1735–1744, doi:10.3762/bjoc.13.168

• Nan Sun Meng Chen Liqun Jin Wei Zhao Baoxiang Hu Zhenlu Shen Xinquan Hu College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310032, China 10.3762/bjoc.13.168 Abstract Three PEG-functionalized imidazolium salts L1–L3 were designed and prepared from commercially available

• 10,000. Keywords: aqueous homogeneous catalysis; Mizoroki–Heck reaction; Na2PdCl4; PEG-functionalized imidazolium salts; Introduction Nowadays, both increasing environmental concerns and drastic commercial competition are the driving forces to develop more sustainable and economic processes for

• activity in Mizoroki–Heck reactions with DMF as solvent [66]. With this regards, we herein report the development of a new poly(ethylene glycol, PEG) and pyridine bi-functionalized imidazolium salt L1 (Figure 1), which was employed as a water soluble NHC ligand precursor for an in situ generated Pd–NHC

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

• membrane of Escherichia coli (E. coli) [30]. For extraction of membrane proteins, commonly micelle-forming detergents such as sodium dodecyl sulfate (SDS), polyethylene–polyethyleneglycol (PE–PEG), sugar glycosides or polyoxyethylenes are applied [24][25][28][31][32]. SDS is an efficient detergent for

• carried out, reaching higher molecular weights and yields compared to catalysis with the micelle-forming refolding reagent PE–PEG. Minimum of MPD molecules was analyzed by molecular dynamics studies to enable refolding of SDS-denatured transmembrane protein FhuA ΔCVFtev [29]. This report aims to

• demonstrate the importance of the right choice of the membrane protein stabilizer for biohybrid catalysis. Results and Discussion For solubilizing the transmembrane protein FhuA ΔCVFtev PE–PEG and MPD were applied as stabilizing agent and phenylacetylene polymerization was performed as model reaction (Figure

Synthesis of oligonucleotides on a soluble support

• Harri Lönnberg

Beilstein J. Org. Chem. 2017, 13, 1368–1387, doi:10.3762/bjoc.13.134

• by Bonora et al. [37] on polyethylene glycol (PEG 5000) monomethyl ester. The overall strategy was rather similar to that of the solid-supported chemistry (Scheme 2). Accordingly, the 3´-terminal nucleoside, 5´-O-DMTr-N6-Bz-dA, was attached to the support via a 3´-succinyl linker, the 5´-O-DMTr group

• DCM/Et2O. In spite of several precipitations and recrystallizations, one coupling cycle could be completed in 5 hours, the stepwise coupling yield ranging from 90% to 95% and the crude PEG-bound octamer was obtained in 79% yield. The coupling of dGibu proceeded, however, in more than 100% yield, which

• tetramethylguanidine in aq dioxane [39] and aq ammonia, and purified by ion-exchange chromatography on DEAE cellulose. From 980 mg of crude PEG-octamer, 85 mg of pure lyophilized TEA salt of d(5´-TAGCGCTA-3´) was obtained. In other words, the yield of the isolation step was less than 30%. To avoid the modification of

One-pot synthesis of block-copolyrotaxanes through controlled rotaxa-polymerization

• Jessica Hilschmann,
• Gerhard Wenz and
• Gergely Kali

Beilstein J. Org. Chem. 2017, 13, 1310–1315, doi:10.3762/bjoc.13.127

• already started from a PEG α-CD pseudopolyrotaxane, but unthreading of α-CD was found to be a severe problem during polymerization, which could only be overcome by elaborate attachment of “molecular hooks” to both chain ends [30]. Furthermore, polyisoprene is advantageous for biomedical applications

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

• Stephen Hill and
• M. Carmen Galan

Beilstein J. Org. Chem. 2017, 13, 1136–1138, doi:10.3762/bjoc.13.112

• polysaccharide-derived CDs in the presence of PEG-200 and how the starting material composition is conferred to the CD products. Corrected Scheme 22 of the original article. Hyaluronic acid (HA) and glycine-derived CDs, suspected to be decorated in unreacted HA, allowing receptor-mediated cell uptake.

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

• intracellular stability. Liz-Marzan et al. assessed the ability of glycan ligands to reduce the protein corona formation around rod-shaped AuNPs [71]. Lactose- and polyethylene glycol (PEG)-functionalized gold nanorods demonstrated similar ability in reducing the interaction with proteins, when compared to

• citrate-AuNPs. Moreover, comparing the macrophage NP uptake, the authors demonstrated that the lactose shell can prevent phagocytosis more efficiently than PEG coating. A deep knowledge of any aspect which can influence the GAuNP behavior is important to drive the correct design of the nanosystem and is

• ). By means of this sugar chips the carbohydrate−protein interactions have been analyzed and quantified in a very small volume with results confirmed by the conventional LSPR biosensors. Gibson et al. [66] designed 40 nm AuNPs capped with glyco-PEG ligands to discriminate different strains of E. coli

Aggregation behaviour of a single-chain, phenylene-modified bolalipid and its miscibility with classical phospholipids

• Simon Drescher,
• Vasil M. Garamus,
• Christopher J. Garvey,
• Annette Meister and
• Alfred Blume

Beilstein J. Org. Chem. 2017, 13, 995–1007, doi:10.3762/bjoc.13.99

• DPPC/DHPC systems [49], or for mixtures of phospholipids with other amphiphilic substances, e.g., in PEG-stabilized bilayer systems [50][51], for phospholipids with membrane scaffold proteins [52][53] or in combination with copolymers [54][55], or for DPPC in mixture with a T-shaped amphiphile [56

Transition-metal-free one-pot synthesis of alkynyl selenides from terminal alkynes under aerobic and sustainable conditions

• Adrián A. Heredia and
• Alicia B. Peñéñory

Beilstein J. Org. Chem. 2017, 13, 910–918, doi:10.3762/bjoc.13.92

• of diselenides as starting reagents, under an oxygen atmosphere and using PEG 200 as the solvent. This procedure involves the in situ generation of dialkyl diselenides through a K3PO4-assisted reaction of an alkyl selenocyanate obtained by a nucleophilic substitution reaction between KSeCN and alkyl

• of obtaining alkynyl analogues based on our methodology developed for the synthesis of vinyl selenides. We herein report the optimized reaction conditions for the one-pot and three-step synthesis of alkynyl selenides 5 using KSeCN as selenium source in PEG 200 as the solvent under an oxygen

• , we performed a screening of solvents under oxygen atmosphere (Table 1). Best yields were obtained with DMF, isopropanol or polyethylene glycol (PEG) as the solvents (Table 1, entries 1, 10, 12 and 13), whereas only moderate yields below 50% were obtained when the reaction was conducted in

Synthesis of ribavirin 2’-Me-C-nucleoside analogues

• Fanny Cosson,
• Aline Faroux,
• Jean-Pierre Baltaze,
• Jonathan Farjon,
• Régis Guillot,
• Jacques Uziel and
• Nadège Lubin-Germain

Beilstein J. Org. Chem. 2017, 13, 755–761, doi:10.3762/bjoc.13.74

• of such compounds [17]. In clinical studies (phase I and II), the fluorinated compound mericitabine in combination with PEG-IFN and RBV was better tolerated and more effective in genotype 1 or 4 patients compared to the standard combination of Peg-IFN and RBV [18][19]. Further, the therapy of

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

• glucose, this particular monosaccharide has been extensively used as an ideal carbon source for CD formation, under a range of experimental conditions. The microwave-assisted synthesis of FCDs from a glucose solution in the presence of poly(ethylene glycol)-200 (PEG-200) by Yang et al. is, to the best of

• show that the use of PEG-200, as a surface passivation agent (SPA), was crucial for favourable photoluminescence (PL) properties and QYs of up to 6.3% were achieved. The use of SPAs is among one of two main techniques that are widely employed to improve the PL properties of FCDs. SPAs are argued to

• hydrophobic red fluorescent CDs via surface passivation and polymer coating, in which hydrophilic anhydride groups of the polymer can react with PEG-diamine, via a ring-opening to afford a free acid and an amide-linked SPA, lead to water-soluble CDs ready for bio-labelling applications. The CDs were then

Transition-metal-catalyzed synthesis of phenols and aryl thiols

• Yajun Liu,
• Shasha Liu and
• Yan Xiao

Beilstein J. Org. Chem. 2017, 13, 589–611, doi:10.3762/bjoc.13.58

• , and could be easily recovered and reused. Aryl iodides, activated aryl bromides and chlorides, and heteroaryl bromides were smoothly converted to phenols. In 2011, the Chen group developed a PEG-400-mediated protocol for the synthesis of phenols using CuI as the catalyst and KOH as the base (Scheme 14

• ) [36]. In this reaction system, non-toxic and cheap PEG-400 played a dual role as both ligand and solvent. The effective catalytic system could convert aryl iodide to phenols in high yields within 5 hours at 100 °C. The conversion of aryl bromides bearing either an electron-donating group or an

• (OAc)2-catalyzed ortho-hydroxylation of the synthesized diarylpyridines [59]. Their protocol employed oxone as oxidant, allowing the conversion to complete within 2 hours in PEG-3400/t-BuOH at 80–90 °C (Scheme 30). By employing their protocol, ortho-hydroxyarenes were predominately formed. This method

Diels–Alder reactions of myrcene using intensified continuous-flow reactors

• Christian H. Hornung,
• Miguel Á. Álvarez-Diéguez,
• Thomas M. Kohl and
• John Tsanaktsidis

Beilstein J. Org. Chem. 2017, 13, 120–126, doi:10.3762/bjoc.13.15

• the maleates 2d and 2e required up to 10 h reaction time at 140 °C to reach near-completion. The slowest reactions were observed using itaconic acid (2c) and the PEG containing acrylate 2g. Acrylic acid (2b) was selected for further study given our interest in products with surfactant properties, and

Poly(ethylene glycol)s as grinding additives in the mechanochemical preparation of highly functionalized 3,5-disubstituted hydantoins

• Andrea Mascitti,
• Massimiliano Lupacchini,
• Ruben Guerra,
• Ilya Taydakov,
• Lucia Tonucci,
• Nicola d’Alessandro,
• Frederic Lamaty,
• Jean Martinez and
• Evelina Colacino

Beilstein J. Org. Chem. 2017, 13, 19–25, doi:10.3762/bjoc.13.3

• investigated in the presence of various poly(ethylene) glycols (PEGs), as safe grinding assisting agents (liquid-assisted grinding, LAG). A comparative study under dry-grinding conditions was also performed. The results showed that the cyclization reaction was influenced by the amount of the PEG grinding

• ) glycols (PEGs) are eco-friendly solvents [1][2], finding applications in the biomedical field and for pharmaceutical formulations [3] and catalysis [4]. PEG-based reaction media [1] are safe reaction environments, efficiently heated by microwaves [5], but their use in organic transformations activated by

• (POLAG) [8]. However, to the best of our knowledge, the systematic investigation of the influence of PEG polymers has not been reported yet for organic syntheses promoted by mechanical energy. We firstly reported the positive influence of PEG solvents as grinding agents for the mechanochemical

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

• polyrotaxanes (PRXs) with reactive functional groups at the terminals of the axle polymers are attractive candidates for the design of supramolecular materials. Herein, we describe a novel and simple synthetic method for end-reactive PRXs using bis(2-amino-3-phenylpropyl) poly(ethylene glycol) (PEG-Ph-NH2) as

• an axle polymer and commercially available 4-substituted benzoic acids as capping reagents. The terminal 2-amino-3-phenylpropyl groups of PEG-Ph-NH2 block the dethreading of the α-CDs after capping with 4-substituted benzoic acids. By this method, two series of azide group-terminated polyrotaxanes

• simple synthesis method for end-reactive PRXs using commercially available 4-substituted benzoic acids. Typically, 4-substituted benzoic acids are unsuitable for the capping of pseudopolyrotaxanes because they are insufficiently bulky. In this study, bis(2-amino-3-phenylpropyl) poly(ethylene glycol) (PEG

Towards potential nanoparticle contrast agents: Synthesis of new functionalized PEG bisphosphonates

• Souad Kachbi-Khelfallah,
• Maelle Monteil,
• Margery Cortes-Clerget,
• Evelyne Migianu-Griffoni,
• Jean-Luc Pirat,
• Olivier Gager,
• Julia Deschamp and
• Marc Lecouvey

Beilstein J. Org. Chem. 2016, 12, 1366–1371, doi:10.3762/bjoc.12.130

• ligands. The use of phosphonate ligands to modify the nanoparticle surface drew a lot of attention in the last years for the design of highly functional hybrid materials. Here, we report a methodology to synthesize bisphosphonates having functionalized PEG side chains with different lengths. The key step

• obtained must be stable in the various biological compartments and they must be stealthy to avoid the elimination by macrophages. For this purpose, appropriate coatings have already been reported [3][4]. Some of which consist in the NP surface modification using hydrophilic polymers (dextran, PEG) or

• past years, our group has focused its interest in the synthesis of various functionalized hydroxymethylene bisphosphonates (HMBPs) [10] and their applications in health science, especially in antitumor therapy [11][12][13]. Herein, we described the synthesis of novel bifunctional PEG-HMBP compounds in

Artificial Diels–Alderase based on the transmembrane protein FhuA

• Hassan Osseili,
• Daniel F. Sauer,
• Klaus Beckerle,
• Marcus Arlt,
• Tomoki Himiyama,
• Tino Polen,
• Akira Onoda,
• Ulrich Schwaneberg,
• Takashi Hayashi and
• Jun Okuda

Beilstein J. Org. Chem. 2016, 12, 1314–1321, doi:10.3762/bjoc.12.124

• dialysis against SDS-solution, excess catalyst 10–12 was removed. Additional 3 days of dialysis against PE-PEG solution renatured the protein structure to give the expected β-barrel structure, as indicated by CD spectra (Figure 1). The CD spectra show a minimum at around 215 nm and a maximum at 195 nm, as

• SDS at 23 °C. After 3 days, the reaction showed 62% conversion with an endo to exo ratio of 70:30 (Table 1, entry 2). Since detergents such as SDS influences the reaction significantly, this value is in good agreement with previously reported results [32]. In PE-PEG at 4 °C the conversion was lower

• against 200 fold volume containing the refolding detergent PE-PEG (0.125 mM, average Mn = 2250 g/mol), sodium phosphate buffer (10 mM, pH 7.4), and water. The dialysis solution was changed every 12 h. The protein concentration was analyzed by BCA assay, the coupling efficiency was determined by ThioGlo

Supported bifunctional thioureas as recoverable and reusable catalysts for enantioselective nitro-Michael reactions

• José M. Andrés,
• Miriam Ceballos,
• Alicia Maestro,
• Isabel Sanz and
• Rafael Pedrosa

Beilstein J. Org. Chem. 2016, 12, 628–635, doi:10.3762/bjoc.12.61

• nanoparticles [10][11][12], inorganic solids [13][14], and different polystyrene derivatives [15][16][17][18][19][20]. Bifunctional thioureas were first supported on PEG [21], and later on different materials such as poly(methylhydrosiloxane) [16], polystyrene [18][19][20][21][22], and magnetic nanoparticles

Supramolecular polymer assembly in aqueous solution arising from cyclodextrin host–guest complexation

• Jie Wang,
• Zhiqiang Qiu,
• Yiming Wang,
• Li Li,
• Xuhong Guo,
• Duc-Truc Pham,
• Stephen F. Lincoln and
• Robert K. Prud’homme

Beilstein J. Org. Chem. 2016, 12, 50–72, doi:10.3762/bjoc.12.7

• backbones Since the report of host–guest complexation between α-CD and poly(ethylene glycol) (PEG) by Harada and Kamachi in 1990 [82], a variety of pseudo-polyrotaxanes and polyrotaxanes formed through host–guest complexation between cyclodextrins and linear polymers have been reported [83], some of which

• form hydrogels [84][85]. In particular, hydrogels formed by PEG and cyclodextrins have been investigated intensively because of the biocompatibility of their components. Interestingly, local crystallization of the polyrotaxane threaded cyclodextrins, sometimes called molecular necklaces [86], may form

• cross-links and polymer networks in aqueous solution. In 1994, Li et al. reported the formation of hydrogels based on the host–guest complexation between α-CD and high molecular weight PEG [87]. They found the hydrogel melting temperature to increase with increase in PEG length and α-CD concentration

Synthesis of bi- and bis-1,2,3-triazoles by copper-catalyzed Huisgen cycloaddition: A family of valuable products by click chemistry

• Zhan-Jiang Zheng,
• Ding Wang,
• Zheng Xu and
• Li-Wen Xu

Beilstein J. Org. Chem. 2015, 11, 2557–2576, doi:10.3762/bjoc.11.276

• multicomponent CuAAC reaction proceeded well in PEG-400 among various solvents, mainly due to the hydrophilic and hydrophobic character of the PEG-400. As shown in Scheme 12, the CuAAC gave the desired bistriazoles 31 in good to excellent yield when electron-withdrawing groups were present in the benzyl bromides

Smart molecules for imaging, sensing and health (SMITH)

• Bradley D. Smith

Beilstein J. Org. Chem. 2015, 11, 2540–2548, doi:10.3762/bjoc.11.274

• a remarkable self-assembly process that we call Synthavidin (synthetic avidin). A simple example is illustrated in Scheme 5 [44]. A water soluble tetralactam macrocycle with anthracene sidewalls is threaded by squaraine dyes that are flanked by long PEG chains to give highly stable complexes with

• nanomolar dissociation constants. The rate of macrocycle threading is insensitive to the length of the appended PEG chains. But the threading kinetics are greatly affected by the steric size of the second N-substituent at each end of the squaraine dye, and an N-propyl group produces a perfect mixture of

• -pairs. Trapping a macrocyclic receptor containing a reactive ion-pair produces an interlocked [2]rotaxane. (top) Basis of Synthavidin technology. A fluorescent squaraine dye that is flanked by PEG chains can rapidly thread a tetralactam macrocycle in water to produce a highly stable complex. (bottom

Aggregation behaviour of amphiphilic cyclodextrins: the nucleation stage by atomistic molecular dynamics simulations

• Giuseppina Raffaini,
• Antonino Mazzaglia and
• Fabio Ganazzoli

Beilstein J. Org. Chem. 2015, 11, 2459–2473, doi:10.3762/bjoc.11.267

• modulates the formation of micelles, vesicles, nanospheres (or dense aggregates), and nanocapsules [1]. In particular, non-ionic aCD obtained from β-CD modified with hydrophobic thioalkyl chains (H groups in the following) at the primary rim and short polar PEG oligomers (P groups) at the secondary rim form

• recently reported [14], while analogue cationic aCD with terminal short amino-PEG at the secondary rim form nanoassemblies which entrap photosensitizers for photoactivated therapy [25] or DNA for gene delivery [26][27][28][29][30]. The potential of aCD is strengthened by their ability to selectively

Size-controlled and redox-responsive supramolecular nanoparticles

• Raquel Mejia-Ariza,
• Gavin A. Kronig and
• Jurriaan Huskens

Beilstein J. Org. Chem. 2015, 11, 2388–2399, doi:10.3762/bjoc.11.260

• . Davis et al. showed the formation of SNPs using attractive electrostatic interactions between positively charged β-cyclodextrin (CD)-containing polymers and negatively charged siRNA at the core [8]. Neutral adamantyl-grafted poly(ethylene glycol) (Ad-PEG) was incorporated at the surface to stabilize

• (amidoamine) (PAMAM) dendrimers, and a monovalent neutral Ad-PEG stopper is introduced at the surface for stabilization. The SNP size was increased by increasing the amount of multivalent guest molecules in the core, while keeping the host and stopper concentration constant and having an excess of stopper to

• PAMAM (Fc8-PAMAM) dendrimer as the multivalent guest and a monovalent stabilizer. Different stabilizers were used such as: Ad-PEG, Fc-terminated poly(ethylene glycol) (Fc-PEG), methoxypoly(ethylene glycol) (mPEG), and Ad-tetraethylene glycol (Ad-TEG). The effect of the following parameters on the

Self-assemblies of γ-CDs with pentablock copolymers PMA-PPO-PEO-PPO-PMA and endcapping via atom transfer radical polymerization of 2-methacryloyloxyethyl phosphorylcholine

• Jing Lin,
• Tao Kong,
• Lin Ye,
• Ai-ying Zhang and
• Zeng-guo Feng

Beilstein J. Org. Chem. 2015, 11, 2267–2277, doi:10.3762/bjoc.11.247

• inclusion complexation of α-CDs with poly(ethylene glycol) (PEG) [1], a great variety of polymers with different cross-sectional areas have been shown to thread CDs to create PPRs. For example, β-CDs are single-chain-stranded with poly(propylene glycol) (PPG) but not with PEG [2][3], and γ-CDs are not only

• single-chain-stranded with poly(methyl vinyl ether) (PMVE) [4] or poly(dimethylsiloxane) (PDMS) [5], but also double-chain-stranded with PEG and poly(ε-caprolactone) (PCL) [6]. Recently, Akashi et al. reported the single-chain-stranded inclusion complexation of γ-CDs with poly(methyl methacrylate) (PMMA

Synthesis, structure, and mechanical properties of silica nanocomposite polyrotaxane gels

• Kazuaki Kato,
• Daisuke Matsui,
• Koichi Mayumi and
• Kohzo Ito

Beilstein J. Org. Chem. 2015, 11, 2194–2201, doi:10.3762/bjoc.11.238

• components (CDs, in this study) and the nanoparticle surfaces (SiO2), hydroxy groups of the cyclic components of a polyrotaxane comprised of α-CD and PEG (PR) was modified as shown in Scheme 1. The polyrotaxane with triethoxysilylated CD (TES-PR) is suitable for the reaction with SiO2 in the presence of base

• progress. Experimental Materials Crude polyrotaxane consisting of polyethylene glycol (PEG, Mn = 32,000) and α-cyclodextrin (CD) were purchased from Advanced Softmaterials, Inc. The crude polyrotaxane was purified by repeated reprecipitation from its DMSO solution into deionized water. The obtained

• precipitate was freeze-dried and the refined polyrotaxane (PR) obtained as a white powder. The coverage, which is a measure how densely the backbone PEG is covered with CDs, was calculated to be 25% based on the 1H NMR spectrum. Standard polymers for the calibration of the molecular weights by size-exclusion