Consecutive isocyanide-based multicomponent reactions: synthesis of cyclic pentadepsipeptoids

• Angélica de Fátima S. Barreto,
• Otilie E. Vercillo,
• Ludger A. Wessjohann and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2014, 10, 1017–1022, doi:10.3762/bjoc.10.101

• ]. This family of oligomers comprising poly-N-substituted glycines mimics the primary natural structure of peptides and exhibits greater proteolytic stability and increased cellular permeabilities in comparison to peptides [5][6][7]. A powerful synthetic tool for the preparation of a peptoid backbone is

Molecular architecture with carbohydrate functionalized β-peptides adopting 3₁₄-helical conformation

• Nitin J. Pawar,
• Navdeep S. Sidhu,
• George M. Sheldrick,
• Dilip D. Dhavale and
• Ulf Diederichsen

Beilstein J. Org. Chem. 2014, 10, 948–955, doi:10.3762/bjoc.10.93

• oligomers varying the sugar (glucose, galactose, xylose) and sugar protecting groups. The influence of sugar units and the configuration of sugar-β-amino acids on β-peptide secondary structure were investigated by CD spectroscopy. Keywords: carbohydrate recognition; conformation; glycopeptide; β-peptide

• groups still being protected (Figure 2). Further, oligomers 1 and 7 were debenzylated using H2, 10% Pd/C to β-glycopeptides 2 and 8, respectively. The acetonide groups in the galactosyl and xylosyl sugar units were deprotected simultaneously along with the Boc-groups and cleavage from solid support using

• % depending on the kind of sugar units incorporated. Oligomers 1–6 all have in common the (S)-configuration for the β3-sugar side chains; this is in agreement with the right-handed 314-helix and a positive Cotton effect. Nevertheless, β3-peptide 1 seems to provide a different structure and helical sense

The influence of intraannular templates on the liquid crystallinity of shape-persistent macrocycles

• Joscha Vollmeyer,
• Ute Baumeister and
• Sigurd Höger

Beilstein J. Org. Chem. 2014, 10, 910–920, doi:10.3762/bjoc.10.89

• yield of 57%. The comparison of the GPC traces of the crude products of 1a and 1d shows that in the intramolecular reaction less oligomers are formed than in the intermolecular reaction. However, the yields of the cyclization reactions do not differ significantly. That indicates that in the template

• -mediated cyclization side reactions cannot be completely suppressed. In the statistical half ring dimerization, the most important side reaction is the oligomerization of the half rings. Beside the desired dimers also trimers, tetramers, and other oligomers are formed, which can undergo further

• oligomerization reactions or may cyclize. These cyclic oligomers are still soluble and therefore they can be detected by GPC. In case of the template connected half rings, we assume that the oligomers formed through an intermolecular reaction cross-link, most likely form insoluble polymers, and are therefore not

Metal and metal-free photocatalysts: mechanistic approach and application as photoinitiators of photopolymerization

• Jacques Lalevée,
• Sofia Telitel,
• Pu Xiao,
• Marc Lepeltier,
• Frédéric Dumur,
• Fabrice Morlet-Savary,
• Didier Gigmes and
• Jean-Pierre Fouassier

Beilstein J. Org. Chem. 2014, 10, 863–876, doi:10.3762/bjoc.10.83

• ][52][53][54][55]) in formulations containing multifunctional synthetic epoxides, acrylates, monomers/oligomers or epoxide/acrylate blends (renewable raw or modified materials are usable to some extent) with lights extending from the UV to the red, using polychromatic or monochromatic light sources

Staudinger ligation towards cyclodextrin dimers in aqueous/organic media. Synthesis, conformations and guest-encapsulation ability

• Malamatenia D. Manouilidou,
• Yannis G. Lazarou,
• Irene M. Mavridis and
• Konstantina Yannakopoulou

Beilstein J. Org. Chem. 2014, 10, 774–783, doi:10.3762/bjoc.10.73

• and animals in vivo have been demonstrated [6]. Cyclodextrins (CDs, Scheme 1c), are cyclic oligomers of glucopyranose that act as hosts to hydrophobic molecules in aqueous environment [9][10]. CDs have been recognized as potent drug solubilizers and transporters through biological barriers with

• increasingly important applications [11]. A specific category of modified CDs are the CD oligomers, compounds with two or three CD macrocycles linked together at different positions (2–2’, 3–3’, 3–2’, 6–2’ etc) via selected spacers. The multicavity structures can, in principle, be precisely tailored to fit

• specific guest molecules. The oligomers are reported to display improved to significantly enhanced binding capacity as well as superior molecular recognition ability [12][13][14], compared to the natural CDs. Suitable design has resulted in better hosts for applications as sensors and catalysts [15], hosts

Rapid pseudo five-component synthesis of intensively blue luminescent 2,5-di(hetero)arylfurans via a Sonogashira–Glaser cyclization sequence

• Fabian Klukas,
• Alexander Grunwald,
• Franziska Menschel and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 672–679, doi:10.3762/bjoc.10.60

• analyzed by MALDI–TOF mass spectrometry indicating the formation of oligomers with m/z = 422 to 1046. We could efficiently suppress this oligo- and polymerization by increasing the amount of solvent, i.e. by dilution (Table 1, entries 9–13). Additionally increasing the concentration of KOH and water also

Synthesis of novel derivatives of 5-hydroxymethylcytosine and 5-formylcytosine as tools for epigenetics

• Anna Chentsova,
• Era Kapourani and
• Athanassios Giannis

Beilstein J. Org. Chem. 2014, 10, 7–11, doi:10.3762/bjoc.10.2

• of the TCBoc group afforded derivatives 9a–d. These new nucleobase modified 2’-deoxycytidine analogues can be used in the synthesis [29][33][34] of modified DNA oligomers for further studies of the TET-mediated processes which are of great importance in the emerging field of epigenetics. In addition

Studies toward bivalent κ opioids derived from salvinorin A: heteromethylation of the furan ring reduces affinity

• Thomas A. Munro,
• Wei Xu,
• Douglas M. Ho,
• Lee-Yuan Liu-Chen and
• Bruce M. Cohen

Beilstein J. Org. Chem. 2013, 9, 2916–2924, doi:10.3762/bjoc.9.328

• ligands with a furanylmethyl substituent (Figure 3), we decided to use a short linker. As an alternative approach, bivalent ligands with much longer linkers can bind simultaneously to both protomers in a receptor dimer, allowing selective targeting of specific receptor oligomers [21]. We also sought to

Triphenylene discotic liquid crystal trimers synthesized by Co₂(CO)₈-catalyzed terminal alkyne [2 + 2 + 2] cycloaddition

• Bin Han,
• Ping Hu,
• Bi-Qin Wang,
• Carl Redshaw and
• Ke-Qing Zhao

Beilstein J. Org. Chem. 2013, 9, 2852–2861, doi:10.3762/bjoc.9.321

• ][17], and organic photovoltaic solar cells (OPVs) [18][19][20]. The reported DLC oligomers [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] are limited compared with the low-molar-mass DLCs and polymeric DLC materials, due to the

• construction methods for the oligomers. However, DLC oligomers usually possess wider mesophase ranges than the monomers as the crystallization was prevented, due to the size of molecules is enlarged and molecular symmetry is lowered. However DLC oligomers exhibit higher charged carrier mobility than DLC

• polymers, the most important parameter in determining the device performance, as the discotic unites can still self-assemble to higher order through the π–π interaction. In addition, DLC oligomers similar to polymers can be processed on flexible substrates by spin-casting, screen printing, doctor-blading

N,N'-(Hexane-1,6-diyl)bis(4-methyl-N-(oxiran-2-ylmethyl)benzenesulfonamide): Synthesis via cyclodextrin mediated N-alkylation in aqueous solution and further Prilezhaev epoxidation

• Julian Fischer,
• Simon Millan and
• Helmut Ritter

Beilstein J. Org. Chem. 2013, 9, 2834–2840, doi:10.3762/bjoc.9.318

• used [3][4]. However, non-bisphenol A based diepoxides are subject to intensive research [5][6][7][8][9]. The industrial synthesis of BADGE and other commercially available diepoxides proceeds mainly by using epichlorohydrin, whereby usually several side products and oligomers are formed in significant

Oligomeric epoxide–amine adducts based on 2-amino-N-isopropylacetamide and α-amino-ε-caprolactam: Solubility in presence of cyclodextrin and curing properties

• Julian Fischer and
• Helmut Ritter

Beilstein J. Org. Chem. 2013, 9, 2803–2811, doi:10.3762/bjoc.9.315

• diglycidyl ether to give novel oligomeric thermoresponsive epoxide–amine adducts. These oligomers exhibit a lower critical solution temperature (LCST) behavior in water. The solubility properties were influenced with randomly methylated β-cyclodextrin (RAMEB-CD) and the curing properties of the amine–epoxide

• mixtures were analyzed by oscillatory rheology and differential scanning calorimetry, whereby significant differences in setting time, viscosity, and stiffness were observed. Keywords: amino acids; curing properties; cyclodextrin; epoxide–amine oligomers; LCST; Introduction Many partially hydrophobic

• present paper we wish to describe our results about preparation and solubility of novel bio-based amine–epoxy oligoadducts. Also, we present some effects of CD on the solubility of these oligomers. Results and Discussion Generally, primary amins are bifunctional towards diepoxides and are thus monomers

Synthesis of homo- and heteromultivalent carbohydrate-functionalized oligo(amidoamines) using novel glyco-building blocks

• Felix Wojcik,
• Sinaida Lel,
• Alexander G. O’Brien,
• Peter H. Seeberger and
• Laura Hartmann

Beilstein J. Org. Chem. 2013, 9, 2395–2403, doi:10.3762/bjoc.9.276

• the straightforward synthesis of multivalent glycoligands with full control over monomer sequence and functionalization pattern. We demonstrate the potential of this building-block approach by synthesizing oligomers with different numbers and spacing of carbohydrates and also show the feasibility of

• [20]. Carbohydrate conjugation was achieved by copper-catalyzed azide alkyne cycloaddtion (CuAAC) of carbohydrate ligands on alkyne presenting oligomers [21]. As an alternative conjugation approach to CuAAc, a very efficient thiol–ene coupling (TEC) [22][23][24][25] protocol in a continuous flow

• photoreactor was developed involving post functionalization of alkene presenting oligomers by thioglycosides [26]. The flow system allows for precise control over the reaction conditions, is easy to scale up and provides efficient irradiation of the samples by virtue of a sub-millimeter path length. Continuous

Synthesis of mucin-type O-glycan probes as aminopropyl glycosides

• David Benito-Alifonso,
• Rachel A. Jones,
• Anh-Tuan Tran,
• Hannah Woodward,
• Nichola Smith and
• M. Carmen Galan

Beilstein J. Org. Chem. 2013, 9, 1867–1872, doi:10.3762/bjoc.9.218

• and core 3 disaccharide precursors 14 and 15 were then prepared in the presence of catalytic TMSOTf in respective yields of 90% and 76%. Global deprotection of the assembled oligomers was achieved by a tandem process that required no purifications between steps, as the reactions proceeded cleanly as

True and masked three-coordinate T-shaped platinum(II) intermediates

• Manuel A. Ortuño,
• Salvador Conejero and
• Agustí Lledós

Beilstein J. Org. Chem. 2013, 9, 1352–1382, doi:10.3762/bjoc.9.153

• in solution, both 16-electron and 14-electron species are obtained, though the latter are not stable, and only oligomers with bridging hydrides can be detected [125]. Wang and co-workers disclosed the spontaneous self-assembling of [Pt(Me)2(NPA)] 45 by a “rollover” cyclometalation process (Scheme 21

Linkage of α-cyclodextrin-terminated poly(dimethylsiloxanes) by inclusion of quasi bifunctional ferrocene

• Helmut Ritter,
• Berit Knudsen and
• Valerij Durnev

Beilstein J. Org. Chem. 2013, 9, 1278–1284, doi:10.3762/bjoc.9.144

• significantly shifts from 343 nm to 615 and 5489 nm. The hydrodynamic diameter of 615 nm can be explained by the formation of some macrocycles and oligomers by noncovalent interactions of the host and guest molecules. This phenomenon might also explain the almost unchanged viscosity increase of the complex in

Incorporation of perfluorohexyl-functionalised thiophenes into oligofluorene-truxenes: synthesis and physical properties

• Neil Thomson,
• Alexander L. Kanibolotsky,
• Joseph Cameron,
• Tell Tuttle,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2013, 9, 1243–1251, doi:10.3762/bjoc.9.141

• containing perfluorohexylthiophene units at the terminal positions on the arms were synthesised, and their optical and electrochemical properties were investigated to determine the effect that the perfluorohexylthiophene unit has on the HOMO and LUMO properties of the oligomers. By synthesising a molecule

• with longer oligofluorene arms the effects of the perfluorohexylthiophene unit on larger oligomers was explored. The effect of steric hindrance from the perfluorohexyl chain was also evaluated by altering the position of the chain on the thiophene moiety. Keywords: oligomers; perfluorinated-materials

• ; star-shaped molecules; synthesis; truxene; Introduction Star-shaped oligomers share a common central unit with multiple arms branching from the core [1]. The morphology and electronic properties of these oligomers often vary from the linear versions of the arms alone. 10,15-Dihydro-5H-diindeno[1,2-a;1

Efficient regio- and stereoselective access to novel fluorinated β-aminocyclohexanecarboxylates

• Loránd Kiss,
• Melinda Nonn,
• Reijo Sillanpää,
• Santos Fustero and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2013, 9, 1164–1169, doi:10.3762/bjoc.9.130

• appreciable in the case of peptide oligomers formed from conformationally restricted fluorinated amino acids. Although cyclic β-amino acids are of major interest in pharmaceutical chemistry and in peptide research [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59

Synthesis, photophysical and electrochemical characterization of terpyridine-functionalized dendritic oligothiophenes and their Ru(II) complexes

• Amaresh Mishra,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2013, 9, 866–876, doi:10.3762/bjoc.9.100

• oligomers and polymers are amongst the best-studied π-conjugated systems in the past few decades because of their tunable optoelectronic properties [6][7][8]. Furthermore, transition-metal complexes offer significant advantages such as long-lived luminescent excited states, high chemical and photochemical

1-n-Butyl-3-methylimidazolium-2-carboxylate: a versatile precatalyst for the ring-opening polymerization of ε-caprolactone and rac-lactide under solvent-free conditions

• Astrid Hoppe,
• Faten Sadaka,
• Claire-Hélène Brachais,
• Gilles Boni,
• Jean-Pierre Couvercelle and
• Laurent Plasseraud

Beilstein J. Org. Chem. 2013, 9, 647–654, doi:10.3762/bjoc.9.73

• of 50–70% were obtained for the ROP of rac-lactide, which afforded oligomers. The incomplete conversion can be explained by the viscous nature of the reaction mixture, resulting in PLA formation and limiting the polymerization process. Besides, increasing the amount of alcohol and consequently the

• zwitterionic intermediate (propagation step, Scheme 2). As a consequence, if the ratio of monomer to alcohol initiator is too low, the latter can compete with the formed hydroxy-terminated monomers/polymers to initiate the formation of a new polymer chain, and the propagation is stopped. In this case oligomers

Some aspects of radical chemistry in the assembly of complex molecular architectures

• Béatrice Quiclet-Sire and
• Samir Z. Zard

Beilstein J. Org. Chem. 2013, 9, 557–576, doi:10.3762/bjoc.9.61

• methods. The main limitation is that the initial radical R· has to be more stable than adduct radical 29 in order to bias the equilibrium in favour of product 30 and avoid the formation of oligomers by further additions of radical 29 to the alkene. Radicals R· stabilised by electron-withdrawing groups

Peptoids and polyamines going sweet: Modular synthesis of glycosylated peptoids and polyamines using click chemistry

• Daniel Fürniss,
• Timo Mack,
• Frank Hahn,
• Sidonie B. L. Vollrath,
• Katarzyna Koroniak,
• Ute Schepers and
• Stefan Bräse

Beilstein J. Org. Chem. 2013, 9, 56–63, doi:10.3762/bjoc.9.7

• oligonucleotides [5][6][7][11][12][13] displaying only very little toxicity towards mammalian cells [11]. They have also been shown to function in the recognition of biomacromolecules. Likewise, other polycationic species, such as the N-alkylated glycine oligomers (peptoids) [14][15][16][17][18][19][20][21][22][23

• conjugation (Scheme 2) with minor modifications. The CuAAC was carried out by using Cu(CH3CN)4PF6 in THF with 2,6-lutidine as base. Only 1.60 equiv of the azidosugar were necessary to achieve full conversion after 18 h, and no shorter oligomers were observed in the MALDI–TOF spectrum. Cleavage from the resin

Cyclodextrin-based nanosponges as drug carriers

• Francesco Trotta,
• Marco Zanetti and
• Roberta Cavalli

Beilstein J. Org. Chem. 2012, 8, 2091–2099, doi:10.3762/bjoc.8.235

• nanoscale structural characteristics can be expected to provide many potential applications in the field of nanomedicine. Cyclodextrins [1][2][3] are nanometric biomaterials with a close relationship between molecular status and supramolecular properties. They are a class of cyclic glucopyranose oligomers

New efficient ligand for sub-mol % copper-catalyzed C–N cross-coupling reactions running under air

• Per-Fredrik Larsson,
• Peter Astvik and
• Per-Ola Norrby

Beilstein J. Org. Chem. 2012, 8, 1909–1915, doi:10.3762/bjoc.8.221

• higher concentrations [77]. A value lower than 1 indicates that an active monomeric catalyst is in equilibrium with inactive dimers or higher oligomers. The reaction order never drops to zero, as it did with DMEDA, showing that the formation of insoluble aggregates at high concentration [87] is avoided

Influence of cyclodextrin on the solubility of a classically prepared 2-vinylcyclopropane macromonomer in aqueous solution

• Helmut Ritter,
• Jia Cheng and
• Monir Tabatabai

Beilstein J. Org. Chem. 2012, 8, 1528–1535, doi:10.3762/bjoc.8.173

• ; cyclodextrins; graft copolymer; macromonomer; ring-opening free radical polymerization; 2-vinylcyclopropane; Introduction Macromonomers are polymers or oligomers with at least one functional end group that is capable of further polymerization. The molecular weight of macromonomers generally ranges between 1000

• studied area [7][8]. β-Cyclodextrins (β-CDs) are cyclic oligomers consisting of seven α-1,4-glycosidically linked glucopyranose units which are present in the chair conformation [9][10][11][12]. The molecule resembles a truncated cone with approximate Cn-symmetry [13]. The cyclic 1,4-linked glucose units

Interaction of cyclodextrins with pyrene-modified polyacrylamide in a mixed solvent of water and dimethyl sulfoxide as studied by steady-state fluorescence

• Akihito Hashidzume,
• Yongtai Zheng and
• Akira Harada

Beilstein J. Org. Chem. 2012, 8, 1312–1317, doi:10.3762/bjoc.8.150

• fluorescence; water/DMSO mixed solvent; Introduction Cyclodextrins (CDs) are cyclic oligomers composed of glucopyranose units linked through α-1,4-glycoside bonding. They bear a tapered structure with a narrower rim of primary hydroxy groups and a wider rim of secondary hydroxy groups. CDs of 6, 7, and 8