Investigation of the network of preferred interactions in an artificial coiled-coil association using the peptide array technique

• Raheleh Rezaei Araghi,
• Carsten C. Mahrenholz,
• Rudolf Volkmer and
• Beate Koksch

Beilstein J. Org. Chem. 2012, 8, 640–649, doi:10.3762/bjoc.8.71

• the increasing number of helical assemblies made of peptidic foldamers, the combination of artificial oligomers with natural peptides remains a challenge. The main difficulties arise in the prediction of a suitable side-chain composition and the geometry of the foldameric binding groove that interacts

• , and B3β2γ/IaFdEeEg in aqueous solution (59 min). In the case of B3β2γ/IaFdEeEg, despite the presence of tetrameric helix bundles, other species consistent with a higher order of oligomers can be observed; this has also been indicated by SEC at about 45 min. Whereas the stoichiometry of the interaction

Synthesis of mesomeric betaine compounds with imidazolium-enolate structure

• Nina Gonsior,
• Fabian Mohr and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 390–397, doi:10.3762/bjoc.8.42

• unidentified decomposition was obtained, since the extrusion of one component results in the destruction of the polymer backbone. However, further conclusions can be drawn from the thermal stability. Polymers 6a–c are stable up to 300 °C, while oligomers 7a and 7b decompose at temperatures between 200 and 220

• functionalized polymer networks and oligomers, which were stable at temperatures up to 300 °C and 200 °C, respectively. Experimental Materials. Randomly methylated (1.8) β-cyclodextrin (m-β-CD) was obtained from Wacker-Chemie GmbH (Burghausen, Germany). Prior to use, m-β-CD was dried in a CEM Sam 255 microwave

• diagram of 3/m-β-CD complex. Classification of betaine 3. Thermogravimetric analyses of polymer networks 6a–c and oligomers 7a,b. Reaction of p-bromanil (1) with 1-butylimidazole (2). Mechanism of molecular association of the complex. Synthesis of polymer 6 and oligomer 7 based on imidazolium-enolate

Fifty years of oxacalix[3]arenes: A review

• Kevin Cottet,
• Paula M. Marcos and
• Peter J. Cragg

Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22

• to self-inclusion, the authors also proposed the formation of higher order oligomers arising from C60 inclusion in a neighbouring oxacalixarene through the change in conformation illustrated in Figure 27. 5.2 Fluorescent chemosensors In order to determine the equilibrium constants with quaternary

Thermodynamic and kinetic stabilization of divanadate in the monovanadate/divanadate equilibrium using a Zn-cyclene derivative: Towards a simple ATP synthase model

• Hanno Sell,
• Anika Gehl,
• Frank D. Sönnichsen and
• Rainer Herges

Beilstein J. Org. Chem. 2012, 8, 81–89, doi:10.3762/bjoc.8.8

• hold for natural systems – particularly ATP synthase, phosphatases and kinases catalyzing the condensation, hydrolysis and phosphate transfer in phosphate esters and phosphate oligomers – which are unsymmetric with respect to metal complexation of the substrates. In the P–O bond forming/cleaving step

Sexithiophenes as efficient luminescence quenchers of quantum dots

• Christopher R. Mason,
• Yang Li,
• Paul O’Brien,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2011, 7, 1722–1731, doi:10.3762/bjoc.7.202

• potential role in a range of device architectures [15][16]. Additionally, the formation of blends of conjugated oligomers and quantum dots can lead to attractive properties, taking advantage of facile charge transfer due to the high electron affinity of the quantum dot nanoparticles [17][18], as well as

• overcoming processing difficulties associated with devices containing quantum dots alone [15]. The complementary properties of conjugated oligomers/polymers and nanoparticles, and the possible photoinduced electron-transfer processes between them, have led to these materials being combined successfully in

Pseudo five-component synthesis of 2,5-di(hetero)arylthiophenes via a one-pot Sonogashira–Glaser cyclization sequence

• Dominik Urselmann,
• Dragutin Antovic and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2011, 7, 1499–1503, doi:10.3762/bjoc.7.174

• title compounds. This novel pseudo five-component synthesis starting from iodo(hetero)arenes is particularly suitable as a direct access to well-defined thiophene oligomers, which are of peculiar interest in materials science. Keywords: C–C coupling; copper; multicomponent reactions; palladium

Efficient and selective chemical transformations under flow conditions: The combination of supported catalysts and supercritical fluids

• M. Isabel Burguete,
• Eduardo García-Verdugo and
• Santiago V. Luis

Beilstein J. Org. Chem. 2011, 7, 1347–1359, doi:10.3762/bjoc.7.159

• polymers and oligomers [17][18], etc., and the use of liquid phases as the immobilizing media [19][20][21]. A second method to improve the environmental friendliness of the chemical processes is through the use of neoteric solvents, allowing a reduction, or even elimination, of the use of toxic and

Synthesis of enantiomerically enriched (R)-¹³C-labelled 2-aminoisobutyric acid (Aib) by conformational memory in the alkylation of a derivative of L-alanine

• Stephen P. Fletcher,
• Jordi Solà,
• Dean Holt,
• Robert A. Brown and
• Jonathan Clayden

Beilstein J. Org. Chem. 2011, 7, 1304–1309, doi:10.3762/bjoc.7.152

• oligomers. We now report in detail a practical method for the enantioselective synthesis and enantiomeric assignment of a derivative of (R)-1*. Results and Discussion L-Alanine hydrochloride 2 was converted to its sodium salt either in situ with two equiv sodium hydride, or (preferably, and more

Use of mixed Li/K metal TMP amide (LiNK chemistry) for the synthesis of [2.2]metacyclophanes

• Marco Blangetti,
• Patricia Fleming and
• Donal F. O'Shea

Beilstein J. Org. Chem. 2011, 7, 1249–1254, doi:10.3762/bjoc.7.145

• synthesis required identical conditions to the first to provide the di-benzylic metalated derivatives 7 (Table 2). We anticipated that an intramolecular ring closing by oxidative coupling would provide the desired cyclophane product in addition to open chain oligomers or larger ring systems. Substrates 6a–e

Fine-tuning alkyne cycloadditions: Insights into photochemistry responsible for the double-strand DNA cleavage via structural perturbations in diaryl alkyne conjugates

• Wang-Yong Yang,
• Samantha A. Marrone,
• Nalisha Minors,
• Diego A. R. Zorio and
• Igor V. Alabugin

Beilstein J. Org. Chem. 2011, 7, 813–823, doi:10.3762/bjoc.7.93

• remarkable properties, the mechanism of DNA cleavage by photoactivated alkynes and enediynes is still not fully understood. Some light has been shed on the mechanism by the sequence selectivity of DNA cleavage in internally labeled DNA oligomers [28]. All enediyne-, alkyne-, and fulvene-based lysine

Novel carbazole–pyridine copolymers by an economical method: synthesis, spectroscopic and thermochemical studies

• Aamer Saeed,
• Madiha Irfan and
• Shahid Ameen Samra

Beilstein J. Org. Chem. 2011, 7, 638–647, doi:10.3762/bjoc.7.75

• has been focused on organic semiconductors, including polymers, oligomers, dendrimers, small molecules and heavy-metal complexes, after the discovery by Burroughes et al. in 1990 [1][2][3][4][5][6] that they can be used for fabricating organic light emitting diodes (OLEDs). A number of criteria exist

• -precipitated thrice in methanol to remove oligomers. The polymers were obtained as yellow to brown powders which were then dried in a vacuum oven. The polymers were readily soluble, at room temperature, in a variety of common solvents such as tetrahydrofuran, dichloromethane, chloroform and acetone. All

• filtered and washed well with copious quantities of distilled water to remove acetic acid and salts completely. The resulting solid was dissolved in THF and precipitated by adding methanol to remove the oligomers. The precipitation process was repeated three times and the polymers obtained were dried in a

Synthesis of glycoconjugate fragments of mycobacterial phosphatidylinositol mannosides and lipomannan

• Benjamin Cao,
• Jonathan M. White and
• Spencer J. Williams

Beilstein J. Org. Chem. 2011, 7, 369–377, doi:10.3762/bjoc.7.47

• arabinan to the penultimate mannose residue of LM, and is subsequently capped with a variety of groups including inositol phosphate, 5-methylthioxylose and its sulfoxide, and short 1,2-mannose oligomers [7]. Studies into the biosynthesis of the PIMs, LM and LAM have been greatly facilitated by the

Syntheses and properties of thienyl-substituted dithienophenazines

• Annemarie Meyer,
• Eva Sigmund,
• Friedhelm Luppertz,
• Gregor Schnakenburg,
• Immanuel Gadaczek,
• Thomas Bredow,
• Stefan-S. Jester and
• Sigurd Höger

Beilstein J. Org. Chem. 2010, 6, 1180–1187, doi:10.3762/bjoc.6.135

• : oligothiophenes; phenazines; scanning tunneling microscopy; self-assembled monolayers; TD-DFT calculations; Introduction Thiophene based oligomers and polymers have drawn considerable interest as active materials in various fields of organic electronics such as organic light-emitting diodes (OLEDs), organic thin

• manufacturing. Particularly, deposition from the solution phase requires sufficiently high solubility, and one approach to cover this aspect is the functionalization with long, flexible alkyl substituents. Additionally, in many cases (short) oligomers are considerably better soluble than their corresponding

• and could be more easily purified by column chromatography. Nevertheless, both compounds can serve as starting materials for thiophene oligomers with increased donor ability. Thiophene- and bithiophene boronic acids or esters were coupled via Suzuki–Miyaura reactions forming orange-colored thiophene

About the activity and selectivity of less well-known metathesis catalysts during ADMET polymerizations

• Hatice Mutlu,
• Lucas Montero de Espinosa,
• Oĝuz Türünç and
• Michael A. R. Meier

Beilstein J. Org. Chem. 2010, 6, 1149–1158, doi:10.3762/bjoc.6.131

• ). The analytical data of the polymers synthesized is summarized in Table 1 and Table 2 and selected GPC traces are depicted in Figure 5. Except for the cases in which only oligomers were obtained, monomer conversion was quantitative as determined by the total disappearance of the monomer signal in the

• temperature, C2 showed a considerably lower degree of isomerization of 9.91%; however only oligomers (Mn 1700 Da) were obtained. Another goal of this research was to suppress the isomerization side reaction and thus to synthesize well-defined polyesters. Benzoquinones are very effective additives for the

• molecular weights for all the studied catalysts. Quite interestingly, at that temperature the most significant inhibition effect of BQ on the degree of isomerization was observed for C2 (compare entries 15 and 16 in Table 2), however, only oligomers were produced. Similarly as for the results at 80 °C, when

Miniemulsion polymerization as a versatile tool for the synthesis of functionalized polymers

• Daniel Crespy and
• Katharina Landfester

Beilstein J. Org. Chem. 2010, 6, 1132–1148, doi:10.3762/bjoc.6.130

• when dispersed in water in a miniemulsion system [33]. These monomers are typically difficult to polymerize in traditional emulsion polymerizations because of the very low water solubility of the monomers and the oligomers. Functionality was introduced via copolymerization with protonated monomers such

• (methylhydrogenosiloxane), and multiblock vinyl functionalized silicones, respectively. Oligomers of phenyl glycidyl ether were produced in direct miniemulsion initiated by the counter anion of the surfmer didodecyldimethyl ammmonium hydroxide [78]. Cationic polymerization can also be performed in direct miniemulsion in

Redox-active tetrathiafulvalene and dithiolene compounds derived from allylic 1,4-diol rearrangement products of disubstituted 1,3-dithiole derivatives

• Filipe Vilela,
• Peter J. Skabara,
• Christopher R. Mason,
• Thomas D. J. Westgate,
• Asun Luquin,
• Simon J. Coles and
• Michael B. Hursthouse

Beilstein J. Org. Chem. 2010, 6, 1002–1014, doi:10.3762/bjoc.6.113

• thiophenes may be sterically demanding, but the formation of short oligomers cannot be ruled out in this mechanism. Conclusion We have shown that the unusual 1,4-aryl shift observed in the presence of perchloric acid for electron-rich 1,3-dithiole-2-thione and TTF derivatives can be exploited to further

Formation of epoxide-amine oligo-adducts as OH-functionalized initiators for the ring-opening polymerization of ε-caprolactone

• Julia Theis and
• Helmut Ritter

Beilstein J. Org. Chem. 2010, 6, 938–944, doi:10.3762/bjoc.6.105

• catalytic transfer hydrogenation. Accordingly, 4-nitroanisole was reduced under microwave conditions to give 4-aminoanisole which reacted immediately with the diglycidyl ether of bisphenol A in an addition polymerization reaction to yield oligo(amino alcohol)s. The hydroxy groups of the new formed oligomers

• oligomers with repetitive units. Molecular weights calculated from the GPC curve are about 1700 g mol−1 for Mn and 2600 g mol−1 for Mw. The molecular weight distribution of the addition polymer 4 is relatively narrow (Mw/Mn = 1.6) which is typical for low molecular weight polymers. The differential scanning

• solvent. Surprisingly, in this process only reduction of the nitro groups took place, but no formation of oligomers was observed. Performing the solvent-free one-pot synthesis with reaction times up to 1 h did not lead to higher molecular weights. The formation of low molecular weight adducts 4 here is

Conjugated polymers containing diketopyrrolopyrrole units in the main chain

• Bernd Tieke,
• A. Raman Rabindranath,
• Kai Zhang and
• Yu Zhu

Beilstein J. Org. Chem. 2010, 6, 830–845, doi:10.3762/bjoc.6.92

• -containing polymers are considerably more stable than the DPP monomers or non-conjugated DPP-polymers. Dehaen et al. used a stepwise sequence of Suzuki couplings to prepare rod-like DPP-phenylene oligomers with well-defined lengths [26]. The resulting oligomers contained three, five and seven DPP units

EPR and pulsed ENDOR study of intermediates from reactions of aromatic azides with group 13 metal trichlorides

• Giorgio Bencivenni,
• Riccardo Cesari,
• Daniele Nanni,
• Hassane El Mkami and
• John C. Walton

Beilstein J. Org. Chem. 2010, 6, 713–725, doi:10.3762/bjoc.6.84

•  2 and they clearly correspond to a trimer, also probably containing a single F-atom, i.e. 19b+•. It seems clear that the MCl3 reactions with aromatic azides entail a progression from the aniline XC6H4NH2, to the dimer XC6H4NHC6H4NH2, to the trimer XC6H4NHC6H4NHC6H4NH2, thence to oligomers and

Synthesis, electronic properties and self-assembly on Au{111} of thiolated (oligo)phenothiazines

• Adam W. Franz,
• Svetlana Stoycheva,
• Michael Himmelhaus and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2010, 6, No. 72, doi:10.3762/bjoc.6.72

• conductive molecular wires investigated. Among many heteroaromatic systems, phenothiazines, their derivatives and oligomers are interesting building blocks for rigid-rod and wire-like molecular modules for single-molecule electronics as a consequence of their electronic properties. In particular, their

• towards the synthesis and study of (oligo)phenothiazine-based functional π-systems [40][41][42][43][44][45][46], we have now focused our attention on thiolated phenothiazines and (oligo)phenothiazines as “alligator-clips”. Here, we report the synthesis of phenothiazines and their oligomers bearing

• formation of thiol-bound (oligo)phenothiazines on gold surfaces. Whereas the first oligomers are non-fluorescent, the triad and the tetrad display intense greenish-blue fluorescence in addition to distinct multiple reversible oxidation. The in situ deprotection of the thioacetates to thiols in the presence

Poly(glycolide) multi-arm star polymers: Improved solubility via limited arm length

• Florian K. Wolf,
• Anna M. Fischer and
• Holger Frey

Beilstein J. Org. Chem. 2010, 6, No. 67, doi:10.3762/bjoc.6.67

• influence of the flexible PG core. The Tg increased slightly with molecular weight, as it is also observed for most linear polymers. Both findings can be attributed to the low average number of repeating units per arm and are often observed for oligomers. This generally ensures increased chain mobility. As

Polar tagging in the synthesis of monodisperse oligo(p-phenyleneethynylene)s and an update on the synthesis of oligoPPEs

• Dhananjaya Sahoo,
• Susanne Thiele,
• Miriam Schulte,
• Navid Ramezanian and
• Adelheid Godt

Beilstein J. Org. Chem. 2010, 6, No. 57, doi:10.3762/bjoc.6.57

• ][7][12][34][37]. The divergent-convergent route that employs the two orthogonal alkyne protecting groups TIPS and HOM (Scheme 2b) does not only allow the fast growth of oligomers – only four steps for doubling the number of repeating units with two of the four steps being experimentally extremely

• as polar tags for the chromatographic separation. Polar tagging with HOM [47][48][49] or HOP [34][42][45][50][51][52][53][54][55][56][57] has been the key to the successful syntheses of a variety of aryleneethynylene building blocks and oligomers [42][45][47][48][49][50][51][52] and of oligoeneynes

• room temperature. The reaction with γ-MnO2 was the fastest. Even more important, γ-MnO2 when applied to the oligomers 1an proved to be highly reliable in its oxidizing power making it the reagent of choice for the removal of HOM groups. Some experimental results hint at a reduced activity of γ-MnO2

Synthesis, characterization and photoinduced curing of polysulfones with (meth)acrylate functionalities

• Cemil Dizman,
• Sahin Ates,
• Lokman Torun and
• Yusuf Yagci

Beilstein J. Org. Chem. 2010, 6, No. 56, doi:10.3762/bjoc.6.56

• polymerization and conversion were evaluated. Thermal properties of the photochemically cured films were studied by differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA). Keywords: acrylates; photoinitiated polymerization; polysulfone; UV-curable oligomers; Introduction Polysulfones

• the problems associated with the brittleness of epoxy resins [7][8][9][10][11]. Telechelic oligomers are defined as the prepolymers carrying one or more functional end groups. They take part in further polymerization or other reactions through their functional end groups [12]. The functionality of the

• , production-line adjustability, low temperature processing, non-polluting and solvent-free formulations, and uncomplicated designed system. Organic materials (monomers, oligomers, polymers) with photoinitiators can be used in UV-curing systems. There are several photoinitiators acting in the UV and visible

Chemical aminoacylation of tRNAs with fluorinated amino acids for in vitro protein mutagenesis

• Shijie Ye,
• Allison Ann Berger,
• Dominique Petzold,
• Oliver Reimann,
• Benjamin Matt and
• Beate Koksch

Beilstein J. Org. Chem. 2010, 6, No. 40, doi:10.3762/bjoc.6.40

• hydrophobic amino acids have been incorporated into the hydrophobic core of peptides, oligomers and proteins, leading to a significant increase in the thermal stability of the structure [12][13][14][15]. The introduction of fluoroalkyl groups into proteins can also enhance the hydrophobicity of the molecule

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32