Olefin metathesis in air

• Lorenzo Piola,
• Fady Nahra and
• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 2038–2056, doi:10.3762/bjoc.11.221

• ]. Conversions were found to be as low as 10% in DCM and <20% in toluene. In 2009, Abell and Zaman reported the use of a Hoveyda–Grubbs 2nd generation ruthenium-based catalyst immobilized on PEG (61, Figure 7) [65]. This catalyst was soluble in dichloromethane but could be retrieved and recycled by simple

Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC) and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions

• Shawna L. Balof,
• K. Owen Nix,
• Matthew S. Olliff,
• Sarah E. Roessler,
• Arpita Saha,
• Kevin B. Müller,
• Ulrich Behrens,
• Edward J. Valente and
• Hans-Jörg Schanz

Beilstein J. Org. Chem. 2015, 11, 1960–1972, doi:10.3762/bjoc.11.212

• monomer liquidity and polyethylene glycol (PEG) based Emulgin® B3 as surfactant which was previously vigorously stirred for 1 h and then further emulsified using a sonication probe for another 5 min establishing the microemulsion. The emulsion polymerization reactions were conducted at less favorable

• after 30 min. General procedure for the preparation of the polymer dispersions using DCPD or DCPD/COE mixtures with complexes 11 and 12. A mixture of 73.1 g of water, 8.3 g of a 10% (by strength) solution of PEG-30 cetyl stearyl ether (Emulgin® B3) as charge-neutral surfactant, 0.75 g of n-hexadecane

Dicarboxylic esters: Useful tools for the biocatalyzed synthesis of hybrid compounds and polymers

• Ivan Bassanini,
• Karl Hult and
• Sergio Riva

Beilstein J. Org. Chem. 2015, 11, 1583–1595, doi:10.3762/bjoc.11.174

• weight (12–18000 Dalton) were obtained (Figure 6). Nano particles of the polymer were used for a controlled slow release of the drug doxorubicin (29) trapped in this material. Bhatia et al. used Novozyme 435 to make polymers from functionalized pentofuranose derivatives (i.e, 30) and PEG-600 dicarboxylic

• ´-dithiodipropionic acid dimethyl ester in combination with pentadecalactone and 1,4-butandiol (Figure 8) [57]. When MeO-PEG-OH was used as chain terminator amphiphilic copolymers were formed. The hydrophobicity of the polymer could easily be changed by the content of the lactone. The copolymers had low toxicity and

• diester using ethyl α-bromoacetate. The formed diester was copolymerized with PEG using CAL-B (Figure 14). The final product was an effective activator of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) several times better than the free curcumin [66]. The curcumin diester was used in a second polymer

The synthesis of active pharmaceutical ingredients (APIs) using continuous flow chemistry

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2015, 11, 1194–1219, doi:10.3762/bjoc.11.134

Radical-mediated dehydrative preparation of cyclic imides using (NH₄)₂S₂O₈–DMSO: application to the synthesis of vernakalant

• Dnyaneshwar N. Garad,
• Subhash D. Tanpure and
• Santosh B. Mhaske

Beilstein J. Org. Chem. 2015, 11, 1008–1016, doi:10.3762/bjoc.11.113

• , hydrothermal cyclization, H2SO4 in acetic acid, PEG-600, silica supported TaCl5, esterification using inorganic base and alkylating agent followed by heating in the presence of tetrabutylammonium bromide, diphenyl 2-oxo-3-oxazolinylphosphonate and Et3N as well as several other conditions have been reported in

Adsorption mechanism and valency of catechol-functionalized hyperbranched polyglycerols

• Stefanie Krysiak,
• Qiang Wei,
• Klaus Rischka,
• Andreas Hartwig,
• Rainer Haag and
• Thorsten Hugel

Beilstein J. Org. Chem. 2015, 11, 828–836, doi:10.3762/bjoc.11.92

• with dopamine. Dopamine is derived from L-DOPA by removing the carboxyl group. This leaves an amine group that was used to covalently couple the probe molecule to the tip through a PEG linker using NHS-ester chemistry, as illustrated in the inset of Figure 1B. A sample force–distance trace showing the

• groups of one molecule or two molecules with catechol groups. The fact that only two of the five measurements showed high force peak interactions could be explained by geometrical constraints. The molecule was covalently attached to the tip by a PEG tether, which limits the ability of the molecule to

• catechol anchor and the second with two catecholic anchors. Note that in the last case, two catechols with two PEG linkers were involved that shared the applied force. Therefore, the triple maximum force peak with forces of up to 2 nN could be measured despite rupture forces of 1.4 nN for the Si–O bond

Mechanical stability of bivalent transition metal complexes analyzed by single-molecule force spectroscopy

• Manuel Gensler,
• Christian Eidamshaus,
• Maurice Taszarek,
• Hans-Ulrich Reissig and
• Jürgen P. Rabe

Beilstein J. Org. Chem. 2015, 11, 817–827, doi:10.3762/bjoc.11.91

• rupture. Results and Discussion Regarding the synthesis, pyridine nanorod 3, which was also precursor for the synthesis of complex 2a [27], was hydrogenated to receive intermediate 4 (Scheme 1). Subsequent coupling with bifunctional poly(ethylene glycol) (PEG) and purification by dialysis gave compound 5

• bifunctional PEG as written above. Figure 1 shows the expected coordination complexes of our mono- and bivalent model systems with Cu2+ in aqueous solution. In the present work, we analyzed the bivalent systems 2b and 2c by DFS, similarly as for the recently published reference case of 2a [27]. We modified

• ) cantilever tip, there is also a certain possibility of simultaneous bond formation as shown in Figure 2b, or non-specific interactions directly between tip and surface. For a proper detection of single-molecular events, we utilized PEG chains with a well characterized force-extension behavior [40][41

Influence of length and flexibility of spacers on the binding affinity of divalent ligands

• Susanne Liese and
• Roland R. Netz

Beilstein J. Org. Chem. 2015, 11, 804–816, doi:10.3762/bjoc.11.90

• ratio lp/L ≈ 10 and thus correspond to the very stiff limit. Polyethylene glycol (PEG) with a persistence length of about lp = 0.38 nm on the other hand is characterized by a ratio smaller than lp/L = 0.08 and thus correspond to the flexible limit [23]. Effective concentration – harmonic spring and

• surface (P′(ρ,z = 0,N) = 0). To obtain the parameter α, P′ has to be integrated over one half space: In the limit of a long chain (N >> 1), Equation 28 can be approximated as: A PEG spacer with b = 0.38 nm requires 30–800 segments to adopt an average end-to-end distance of 2 to 10 nm. In this range α

• also the maximum and width of the RBA are in this case determined by the binding range σ. In Figure 5b we assume a DNA spacer that is decorated with flexible PEG linkers at both ends. The PEG linkers consist of four monomers each. Assuming Gaussian-chain behavior with a segment length of b = 0.38 nm

Regulation of integrin and growth factor signaling in biomaterials for osteodifferentiation

• Qiang Wei,
• Theresa L. M. Pohl,
• Anja Seckinger,
• Joachim P. Spatz and
• Elisabetta A. Cavalcanti-Adam

Beilstein J. Org. Chem. 2015, 11, 773–783, doi:10.3762/bjoc.11.87

• and BMP-2s are integrated in matrix metalloproteinase (MMP)-degradable PEG-maleimide hydrogels. The peptide ligands successfully host stem cells in vivo, and the sustained release of low doses of BMP-2 direct endogenous stem cell differentiation and promote bone healing [87]. Furthermore, the signal

Multivalent polyglycerol supported imidazolidin-4-one organocatalysts for enantioselective Friedel–Crafts alkylations

• Tommaso Pecchioli,
• Manoj Kumar Muthyala,
• Rainer Haag and
• Mathias Christmann

Beilstein J. Org. Chem. 2015, 11, 730–738, doi:10.3762/bjoc.11.83

• and various families of branched polymers such as dendrimers, dendritic-hybrid and hyperbranched polymers are used as macromolecular support for catalysis [10][11][12]. Linear polymers such as poly(ethylene glycol) (PEG) [13] or non-cross-linked polystyrene (NCPS) [14] are readily available but suffer

Probing multivalency in ligand–receptor-mediated adhesion of soft, biomimetic interfaces

• Stephan Schmidt,
• Hanqing Wang,
• Daniel Pussak,
• Simone Mosca and
• Laura Hartmann

Beilstein J. Org. Chem. 2015, 11, 720–729, doi:10.3762/bjoc.11.82

• a concanavalin A (ConA) layer via poly(ethylene glycol)-(PEG)-based soft colloidal probes (SCPs). Special emphasis is on the dependence of multivalent presentation and density of carbohydrate units on specific adhesion. Consequently, we first present a synthetic strategy that allows for controlled

• density variation of functional groups on the PEG scaffold using unsaturated carboxylic acids (crotonic acid, acrylic acid, methacrylic acid) as grafting units for mannose conjugation. We showed by a range of analytic techniques (ATR–FTIR, Raman microscopy, zeta potential and titration) that this

• synthetic strategy allows for straightforward variation in grafting density and grafting length enabling the controlled presentation of mannose units on the PEG network. Finally we determined the specific adhesion of PEG-network-conjugated mannose units on ConA surfaces as a function of density and grafting

Synthesis of tripodal catecholates and their immobilization on zinc oxide nanoparticles

• Franziska Klitsche,
• Julian Ramcke,
• Julia Migenda,
• Andreas Hensel,
• Tobias Vossmeyer,
• Horst Weller,
• Silvia Gross and
• Wolfgang Maison

Beilstein J. Org. Chem. 2015, 11, 678–686, doi:10.3762/bjoc.11.77

• PEG, a sulfobetaine and an adamantyl group. The potential of these conjugates has been demonstrated with the immobilization of tripodal catecholates on ZnO NPs. The results confirmed a high loading of tripodal PEG-catecholates on the particles and the formation of stable PEG layers in aqueous solution

• derivatives bearing an additional effector moiety may be used to generate stable particles with tailored properties, good solubility and biocompatibility. Suitable effectors in this context are PEG [31][32][33], zwitterions [34][35] or polyglycerols [36][37] which, when immobilized on NPs, may be used to tune

• as a cheap starting material [43]. Amine 1 was coupled to a commercially available PEG-carboxylate (5 kDa) with EDC/DMAP. The resulting PEG-conjugate was treated with KOTMS to remove the methyl esters to give tricarboxylic acid 2 in good 57% yield for the two-step procedure. In a last step, dopamine

The preparation of new functionalized [2.2]paracyclophane derivatives with N-containing functional groups

• Henning Hopf,
• Swaminathan Vijay Narayanan and
• Peter G. Jones

Beilstein J. Org. Chem. 2015, 11, 437–445, doi:10.3762/bjoc.11.50

• bridging and the strain of the desired 17 would be too high for a successful ring closure. Reacting 16 with tetraethylene glycol (TEG) under high dilution conditions (toluene, reflux, 7 d) provides the crownophane 18 in 68% yield (Scheme 2). Likewise, replacement of TEG by pentaethylene glycol (PEG

Highly selective electrochemical fluorination of dithioacetal derivatives bearing electron-withdrawing substituents at the position α to the sulfur atom using poly(HF) salts

• Bin Yin,
• Shinsuke Inagi and
• Toshio Fuchigami

Beilstein J. Org. Chem. 2015, 11, 85–91, doi:10.3762/bjoc.11.12

• was achieved by direct and indirect anodic oxidation in the presence of the poly(HF) salts [12][13][14][15][16][23][24][25] or alkali-metal fluorides like KF and CsF with PEG 200 [17]. The anodic fluorination of a dithioacetal derived from an aliphatic aldehyde provided the fluorodesulfurization

Modification of physical properties of poly(L-lactic acid) by addition of methyl-β-cyclodextrin

• Toshiyuki Suzuki,
• Ayaka Ei,
• Yoshihisa Takada,
• Hiroki Uehara,
• Takeshi Yamanobe and
• Keiko Takahashi

Beilstein J. Org. Chem. 2014, 10, 2997–3006, doi:10.3762/bjoc.10.318

• . It has been reported that the unmodified α-CD accelerates the crystallization of PCL, PEG, PBS and P3HB during cooling from melts. Cooling measurements by DSC were carried out for PLLA, PL-MCD50, 67 and 83 to confirm the similar effects. However, the crystallization was not observed for PLLA, PL

A novel 4-aminoantipyrine-Pd(II) complex catalyzes Suzuki–Miyaura cross-coupling reactions of aryl halides

• Claudia A. Contreras-Celedón,
• Darío Mendoza-Rayo,
• José A. Rincón-Medina and
• Luis Chacón-García

Beilstein J. Org. Chem. 2014, 10, 2821–2826, doi:10.3762/bjoc.10.299

• are summarized in Table 2. The reaction proceeded in both protic and aprotic solvents, but with significantly varying yields of the product. In the cases of H2O, THF, DMF, toluene, benzene and PEG 600 solvents, the yields were between 29–67% (Table 2, entries 1–6), all lower than the product yield

• was carried out at room temperature for 22 hours. However, the yield of 3q was low when 1:1.5 PEG 600/H2O was used at 80 °C (Table 2, entry 7) and moderate yield when 1:1 EtOH/H2O when was used as solvent at room temperature (rt) or at 80 °C (Table 2, entries 11 and 12). Different bases were screened

Preparation and evaluation of cyclodextrin polypseudorotaxane with PEGylated liposome as a sustained release drug carrier

• Kayoko Hayashida,
• Taishi Higashi,
• Daichi Kono,
• Keiichi Motoyama,
• Koki Wada and
• Hidetoshi Arima

Beilstein J. Org. Chem. 2014, 10, 2756–2764, doi:10.3762/bjoc.10.292

• such as polyethylene glycol (PEG). On the other hand, PEGylated liposomes have been utilized as a representative anticancer drug carrier. However, little is known about the formation of CD PPRX with PEGylated liposome. In the present study, we first report the formation of CD PPRX with PEGylated

• liposome and evaluate it as a sustained release drug carrier. PEGylated liposome encapsulating doxorubicin was disrupted by the addition of α-CD. Meanwhile, γ-CD included two PEG chains and/or one bending PEG chain of PEGylated liposome and formed PPRX without the disruption of the membrane integrity of

• et al. have reported that a number of α-CDs spontaneously thread onto polyethylene glycol (PEG) and form necklace-like supramolecular assemblies [6][7]. The latter are referred to as polypseudorotaxanes (PPRXs), since the release of α-CD from the polymer chain can be achieved upon dissolution in

Synthesis of a resin monomer-soluble polyrotaxane crosslinker containing cleavable end groups

• Ji-Hun Seo,
• Shino Nakagawa,
• Koichiro Hirata and
• Nobuhiko Yui

Beilstein J. Org. Chem. 2014, 10, 2623–2629, doi:10.3762/bjoc.10.274

• , e.g., α-cyclodextrin (α-CD), threaded on a linear guest molecule, e.g., poly(ethylene glycol) (PEG) [1]. The threaded α-CD molecules are known to be reversibly disassembled when a cleavable end-capping group was introduced in the PEGs, and the cleavable reaction was triggered by proper signals [2][3

•  3 shows the results of the SEC analysis of the synthesized polymers. Although a slight degradation of PRX was observed (disassembled α-CD at 42 min), C12-Bu12 and C12-Bu12-MA12 show shorter elution times compared to PEG, which indicates that the molecular weight is increased due to the formation of

• an inclusion complex of PEG with ca. 50 α-CDs. The degradation nature of C12-Bu12-MA12 was confirmed after the treatment with DTT. As shown in Figure 3, the PRX SEC signal almost disappeared, and a large intensity of low molecular weight signals was observed within 40–50 min. The low molecular weight

Synthesis and characterization of a hyper-branched water-soluble β-cyclodextrin polymer

• Francesco Trotta,
• Fabrizio Caldera,
• Roberta Cavalli,
• Andrea Mele,
• Carlo Punta,
• Lucio Melone,
• Franca Castiglione,
• Barbara Rossi,
• Monica Ferro,
• Vincenza Crupi,
• Domenico Majolino,
• Valentina Venuti and
• Dominique Scalarone

Beilstein J. Org. Chem. 2014, 10, 2586–2593, doi:10.3762/bjoc.10.271

• oven at 70 °C. DMF solutions of the samples (3 mg/mL) were filtered through 0.45 μm PTFE membrane filters. Calibration was obtained with PEG/PEO molecular weight standards. All Raman measurements were carried out on dried samples deposited on a glass slide in air and at room temperature. Spectra were

Synthesis of graft polyrotaxane by simultaneous capping of backbone and grafting from rings of pseudo-polyrotaxane

• Kazuaki Kato,
• Katsunari Inoue,
• Masabumi Kudo and
• Kohzo Ito

Beilstein J. Org. Chem. 2014, 10, 2573–2579, doi:10.3762/bjoc.10.269

• (PEG) and the formation of inclusion complexes with α-cyclodextrin (α-CD). PEG with multiple functional groups at each end was prepared by the condensation of PEG-amine and D-gluconic acid; the PEG derivative formed an inclusion complex with α-CD. The polymerization of multiple hydroxy groups at the

• backbone ends resulted in a star-shaped end group, which served as a bulky capping group to prevent dethreading. In contrast, PEG with only one hydroxy group at each end did not produce polyrotaxanes, indicating that single PCL chains were too thin to confine α-CDs to the complex. In addition, the grafting

• form an inclusion complex with α-CD, indicating that the PCL chains at the ends of PEG cannot prevent the dethreading of the CDs. We demonstrated the complexation between α-CD and PCL-PEG-PCL triblock copolymers. The triblock copolymer was synthesized by the ring-opening polymerization of ε

Loose-fit polypseudorotaxanes constructed from γ-CDs and PHEMA-PPG-PEG-PPG-PHEMA

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

Beilstein J. Org. Chem. 2014, 10, 2461–2469, doi:10.3762/bjoc.10.257

• to not only small guest molecules, but also to linear polymeric guest molecules. They can self-assemble into novel inclusion complexes (ICs), or polypseudorotaxanes (PPRs) and polyrotaxanes (PRs) end-capped by bulky stoppers. For example, α-CDs typically include PEG, but not PPG, β-CDs contain PPG

• instead of PEG, and γ-CDs accommodate either single-chain PPG or double-chain PEG [1]. The driving force behind the self-assembly is mostly ascribed to a suitable fit between the cross-sectional area of the incoming polymer chain and the cavity size of the CDs [2]. However, the cavity shape and size of

• first PPRs (comprised of γ-CD and PEG) as early as the 1990s. The γ-CD-based PPRs with designated supramolecular structure have been seldom prepared as compared with the α-CD- or β-CD-based PPRs [5][6][7][8][9][10][11][12][13]. Besides the typical double-chain stranded PPR showing a characteristic

Synthesis and immunological evaluation of protein conjugates of Neisseria meningitidis X capsular polysaccharide fragments

• Laura Morelli,
• Damiano Cancogni,
• Marta Tontini,
• Alberto Nilo,
• Sara Filippini,
• Paolo Costantino,
• Maria Rosaria Romano,
• Francesco Berti,
• Roberto Adamo and
• Luigi Lay

Beilstein J. Org. Chem. 2014, 10, 2367–2376, doi:10.3762/bjoc.10.247

• (BS(PEG)5) linker was used to rule out the interference of the spacer (details are reported in Supporting Information File 1). ELISA analysis using HSA conjugates as coating reagent demonstrated that the conjugated monomer 1 and the dimer 2 at the present dose elicited extremely low levels of

Autonomous assembly of synthetic oligonucleotides built from an expanded DNA alphabet. Total synthesis of a gene encoding kanamycin resistance

• Kristen K. Merritt,
• Kevin M. Bradley,
• Daniel Hutter,
• Mariko F. Matsuura,
• Diane J. Rowold and
• Steven A. Benner

Beilstein J. Org. Chem. 2014, 10, 2348–2360, doi:10.3762/bjoc.10.245

• , each holding 10 µM of DNA (by UV spectroscopy at 260 nm prior to dilution). For the annealing step, aliquots (1 µL, containing each 10 pmol, ca. 125–250 ng of DNA) were combined from each of the stock solutions with 5× ISO buffer (8 μL, 25% PEG-6000, 500 mM Tris-HCl, pH 7.5, 50 mM MgCl2, 50 mM DTT, 5

• mM NAD+) and diluted with water (40 μL final volume; final concentrations: 250 nM each oligonucleotide, 5% PEG-6000, 100 mM Tris-HCl, pH 7.5, 10 mM MgCl2, 10 mM DTT, 1 mM NAD+). This mixture was then heated at 95 °C for 5 min, and then slowly cooled (0.1 °C/second) to 42 °C. Aliquots (5 μL) of the

End group functionalization of poly(ethylene glycol) with phenolphthalein: towards star-shaped polymers based on supramolecular interactions

• Carolin Fleischmann,
• Hendrik Wöhlk and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 2263–2269, doi:10.3762/bjoc.10.235

• formation occurred with bare eyes. For this, a molar excess of 16.7 DPE-CD equivalents, which equals 100 CD units per PP moiety, was added to a solution of 0.05 mg/mL PEG-PP at pH 12. In order to compare the complexation ability of DPE-CD to free β-CD, a sample containing the same number of equivalents of

• form, indeed resulted in a stronger decrease of the colorization. In addition to the qualitative evaluation of the complexation behavior of PEG-PP, UV–vis measurements were performed in order to get an insight into the quantitative complex analysis. For native phenolphthalein, the characteristic

• absorption maximum that refers to the pink color in basic solution can be found at 554 nm in corresponding UV–vis spectra. For the phenolphthalein-containing polymer PEG-PP, a slight bathochromic effect is observed, which shifts the maximum to 561 nm. Accordingly, the decrease of the absorption at 561 nm was

Efficient CO₂ capture by tertiary amine-functionalized ionic liquids through Li⁺-stabilized zwitterionic adduct formation

• Zhen-Zhen Yang and
• Liang-Nian He

Beilstein J. Org. Chem. 2014, 10, 1959–1966, doi:10.3762/bjoc.10.204

• through formation of zwitterionic adducts, combining synthetic strategies to ionic liquids (ILs) and coordination. The essence of our strategy is to make use of multidentate cation coordination between Li+ and an organic base. Also PEG-functionalized organic bases were employed to enhance the CO2

• ). Notably, equimolar CO2 absorption was obtained using task-specific ionic liquids (TSILs) with the phosphonium cation containing long alkyl chains and anions derived from AAs (prolinate and methioninate) [36], or AA salts with bulky N-substituents in polyethylene glycol (PEG) solution [37]. However

• method combining the formation of ILs and coordination to achieve equimolar CO2 capture through zwitterionic adduct formation. The essence of our strategy is to make use of the multisite coordination interaction between Li+ and organic bases or PEG-functionalized organic bases. The readily prepared ILs