Acylsulfonamide safety-catch linker: promise and limitations for solid–phase oligosaccharide synthesis

• Jian Yin,
• Steffen Eller,
• Mayeul Collot and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2012, 8, 2067–2071, doi:10.3762/bjoc.8.232

• Abstract Safety-catch linkers are useful for solid-phase oligosaccharide synthesis as they are orthogonal to many common protective groups. A new acylsulfonamide safety-catch linker was designed, synthesized and employed during glycosylations using an automated carbohydrate synthesizer. The analysis of the

• ] afforded linker 10. To support oligosaccharide synthesis, the safety-catch linker was first coupled to different resins (Scheme 2). In addition, since the activation and cleavage of safety-catch linkers is typically quite slow, a second, base-labile (Zemplén [24]) cleavage site was integrated to facilitate

• , the amount of glycosylating agent was decreased during a reaction, which resulted in the production of glycosylated linkers 21 and 22. It was evident that two unexpected reactions had occurred. First, the use of excess glycosylating agent, common practice for solid-phase-synthesis protocols, leads to

Modulating the activity of short arginine-tryptophan containing antibacterial peptides with N-terminal metallocenoyl groups

• H. Bauke Albada,
• Alina-Iulia Chiriac,
• Michaela Wenzel,
• Maya Penkova,
• Julia E. Bandow,
• Hans-Georg Sahl and
• Nils Metzler-Nolte

Beilstein J. Org. Chem. 2012, 8, 1753–1764, doi:10.3762/bjoc.8.200

• linkers, a set of peptides were prepared (Table 1 and Figure 1). These peptides were obtained after acidic cleavage of the resin-bound protected precursors, purified by preparative HPLC, and the fractions containing the desired compound in high purity were lyophilized from the prep-HPLC buffers. All these

Supramolecular hydrogels formed from poly(viologen) cross-linked with cyclodextrin dimers and their physical properties

• Yoshinori Takashima,
• Yang Yuting,
• Miyuki Otsubo,
• Hiroyasu Yamaguchi and
• Akira Harada

Beilstein J. Org. Chem. 2012, 8, 1594–1600, doi:10.3762/bjoc.8.182

• tertiary gels, which should create a new paradigm in materials science [10]. Polyrotaxanes form topological gels, because the rotor molecules, which act as cross-linkers, slide on the axial polymer chain. In contrast, chemical gels do not exhibit cross-linker slippage. Previously, there have been some

Synthesis of chiral sulfoximine-based thioureas and their application in asymmetric organocatalysis

• Marcus Frings,
• Isabelle Thomé and
• Carsten Bolm

Beilstein J. Org. Chem. 2012, 8, 1443–1451, doi:10.3762/bjoc.8.164

• additional stereogenic centers, alternative molecules with substituted ethylene linkers ((SS,SC)-18 and (RS,SC)-19) were designed. Their syntheses are outlined in Scheme 5, which also underlines the value of the highly modular preparative approach towards such compounds leading to a variety of molecules by

• on the stereochemistry-determining path despite the fact that they were relatively close to the thiourea substrate binding site. Thus, reducing molecular flexibility by incorporation of plain arenes as linkers appears to be more important than conformational fixation through additional stereogenic

The use of glycoinformatics in glycochemistry

• Thomas Lütteke

Beilstein J. Org. Chem. 2012, 8, 915–929, doi:10.3762/bjoc.8.104

• modified monosaccharides, protecting groups, linkers, or other kinds of nonstandard residues, which are neither included in the standard residue sets nor present in the databases used by mass-fingerprinting approaches. Significantly fewer tools are available to aid the interpretation of HPLC or NMR spectra

Diarylethene-modified nucleotides for switching optical properties in DNA

• Sebastian Barrois and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2012, 8, 905–914, doi:10.3762/bjoc.8.103

• polymerase-assisted PEX and PCR experiments, an absolutely critical issue regarding the application of single C–C bonds, or ethinyl or phenylene linkers is the question of whether the canonical base-recognition complementarity is effected by the chromophore modification [42][43]. Due to the strongest

meta-Oligoazobiphenyls – synthesis via site-selective Mills reaction and photochemical properties

• Raphael Reuter and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2012, 8, 877–883, doi:10.3762/bjoc.8.99

• biphenyl restores the photoisomerization properties (Figure 1) [18][19]. In a related example by Samanta and Woolley a similar compound was presented featuring anchoring groups for biological applications (Figure 1) [20]. In another study the team of Hecht synthesized oligomers separated by alkynyl linkers

High-affinity multivalent wheat germ agglutinin ligands by one-pot click reaction

• Henning S. G. Beckmann,
• Heiko M. Möller and
• Valentin Wittmann

Beilstein J. Org. Chem. 2012, 8, 819–826, doi:10.3762/bjoc.8.91

• or three N,N’-diacetylchitobiose moieties. To connect the chitobiose moieties we chose several linkers of varying length and flexibility, which were, nevertheless, all expected to allow simultaneous binding to adjacent binding sites in a chelating fashion, thus, leading to especially effective

• '-diacetylchitobiose are 330–1000. It is interesting to note the differences induced by differing linker geometries. Here, not the most hydrophobic linkers show strongest binding but the ones that apparently promote multivalent binding most efficiently. Whereas the flexible linkers of C4 and C5 lead to β values of

• 1000 and 860, respectively, the ligands C2 and C3 with the less flexible aromatic linkers have significantly lower binding potencies (β values: 480 and 330). This observation points to the possibility that the aromatic linkers cannot adopt a strain-free conformation if the ligand binds in a chelating

Self-assembly of Ru₄ and Ru₈ assemblies by coordination using organometallic Ru(II)₂ precursors: Synthesis, characterization and properties

• Sankarasekaran Shanmugaraju,
• Dipak Samanta and
• Partha Sarathi Mukherjee

Beilstein J. Org. Chem. 2012, 8, 313–322, doi:10.3762/bjoc.8.34

• allowed the formation of the 3D cage 2c. The use of imidazole-based donor linkers in combination with organometallic half-sandwich ruthenium(II) precursors may generate a wide variety of complex molecular architectures with interesting functional properties. Experimental Materials and methods The acceptor

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

• incorporate porphyrin linkers between two oxacalix[3]arenes, but, due to the size of the porphyrins and their rigidity, only the capsular form was found [50]. Treatment with zinc(II) acetate introduced three equivalents of the metal, one for each porphyrin unit. 3.2.3 Capping the upper rim: Capping the upper

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

• Jiří Kulhánek and
• Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

• -dicarbonitrile (methylvinazene, 3) [28][29][30]. These derivatives were recently utilized as suitable precursors for the construction of various CT chromophores (see below). Y-shaped imidazole-derived chromophores Triarylimidazoles (lophines) and derivatives with larger π-linkers represent the simplest D-π-IM-(π

• nitro, dialkylamino, and hydroxy groups as acceptor and donors [13]. Whereas the imidazole- and thiazole-based chromophores 10a,b possess two extended π-linkers with the imino spacers at the imidazole C4/C5 and nitro and dimethylamino groups as acceptor and donor [15], chromophore 11 (VPDPI) represents

• derivatives 14 bearing a cyanoacrylic moiety connected to imidazole C2 by thiophene or thiazole π-linkers were recently utilized as dye-sensitized solar cells with an efficiency up to 6.3% [41]. Several similar classes of imidazole-derived push–pull compounds can be found in the literature. They were mainly

Dependency of the regio- and stereoselectivity of intramolecular, ring-closing glycosylations upon the ring size

• Patrick Claude,
• Christian Lehmann and
• Thomas Ziegler

Beilstein J. Org. Chem. 2011, 7, 1609–1619, doi:10.3762/bjoc.7.189

• 1-thio-galactosyl donor and a 4,6-O-benzylidene-glucose acceptor tethered by peptide-bond-containing linkers of variable size, in order to study systematically the parameters influencing the outcome of the intramolecular, ring-closing glycosylation step. In order to further provide a rationalization

Ratiometric fluorescent probe for enantioselective detection of D-cysteine in aqueous solution

• Xiao-bo Zhou,
• Wing-Hong Chan,
• Albert W. M. Lee and
• Chi-Chung Yeung

Beilstein J. Org. Chem. 2011, 7, 1508–1515, doi:10.3762/bjoc.7.176

• solutions. Interestingly, the probe is only slightly responsive to Hcy and GSH. Results and Discussion N-Alkylation of trans-1,2-diaminocyclohexane with a pair of 9-carboxamidoquinoline moieties through methylene linkers afforded multifunctionalized ACAQ (Figure 2). Bearing six metal ligating sites, ACAQ

Multicomponent synthesis of artificial nucleases and their RNase and DNase activity

• Anton V. Gulevich,
• Lyudmila S. Koroleva,
• Olga V. Morozova,
• Valentina N. Bakhvalova,
• Vladimir N. Silnikov and
• Valentine G. Nenajdenko

Beilstein J. Org. Chem. 2011, 7, 1135–1140, doi:10.3762/bjoc.7.131

• centers of natural RNases A and T1 have been described [13][14][15]. RNA cleavage was shown to be more efficient in the presence of aliphatic hydrophobic linkers [16]. However, the potential role of the alkyl chain of the catalyst remains unclear. Interaction of hydrophobic residues in peptides was

• groups as well as various aliphatic linkers. With these diamides in hand we began the investigation of their biological activity. Currently, real-time PCR is the better method for the quantitation of the target nucleic acids because of its high specificity and sensitivity of up to a few genome

• with cDNA after reverse transcription irrespective of the structures of their substituents and the length of polymethylene linkers. Double-stranded circular plasmid DNA was partially destroyed possibly because of single-stranded DNA breaks. The mechanism has been previously shown for several artificial

Intramolecular hydroamination of alkynic sulfonamides catalyzed by a gold–triethynylphosphine complex: Construction of azepine frameworks by 7-exo-dig cyclization

• Hideto Ito,
• Tomoya Harada,
• Hirohisa Ohmiya and
• Masaya Sawamura

Beilstein J. Org. Chem. 2011, 7, 951–959, doi:10.3762/bjoc.7.106

• that the reactivity of the substrates is affected by the balance between nucleophilicity of the nitrogen atom and acidity of the N–H bond as well as a steric factor. Effect of substituents in acyclic linkers Next, we explored the substrate scope by introducing one or two substituents in the acyclic

Hoveyda–Grubbs type metathesis catalyst immobilized on mesoporous molecular sieves MCM-41 and SBA-15

• Hynek Balcar,
• Tushar Shinde,
• Naděžda Žilková and
• Zdeněk Bastl

Beilstein J. Org. Chem. 2011, 7, 22–28, doi:10.3762/bjoc.7.4

• supports: (a) by exchanging halide ligands X [7][8][9][10][11], (b) by exchanging phosphine and NHC ligands L [12][13], and (c) through the alkylidene ligand [14][15][16][17][18][19]. For these purposes, special ligand molecules with tags suitable for the reaction with the support surface (linkers) are

• catalysts was reported [20]. A second generation Hoveyda–Grubbs catalyst was immobilized on silica without any linkers by simply placing the Ru complex in contact with silica in a suspension. Heterogeneous catalysts (loading from 0.05 to 0.6 wt % Ru) were prepared, which were active in ring-opening

Functionalized copolyimide membranes for the separation of gaseous and liquid mixtures

• Nadine Schmeling,
• Roman Konietzny,
• Daniel Sieffert,
• Patrick Rölling and
• Claudia Staudt

Beilstein J. Org. Chem. 2010, 6, 789–800, doi:10.3762/bjoc.6.86

• reaction. In the following sections it will be shown which cross-linking method, ionic or covalent, will be the most effective to reduce undesired plasticization effects occurring in different separations. Furthermore, different ionic cross-linkers are compared, since it was expected that higher cation

Preparation of aminoethyl glycosides for glycoconjugation

• Robert Šardzík,
• Gavin T. Noble,
• Martin J. Weissenborn,
• Andrew Martin,
• Simon J. Webb and
• Sabine L. Flitsch

Beilstein J. Org. Chem. 2010, 6, 699–703, doi:10.3762/bjoc.6.81

• ; glycoarrays; glycoconjugation; glycosylation; Introduction The chemical conjugation of carbohydrates through the anomeric centre to biomolecules such as peptides, proteins, lipids, metabolites and to array surfaces is an important synthetic challenge [1][2][3][4][5]. A diverse range of linkers and spacers

Novel tetracyclic structures from the synthesis of thiolactone-isatin hybrids

• Renate Hazel Hans,
• Hong Su and
• Kelly Chibale

Beilstein J. Org. Chem. 2010, 6, No. 78, doi:10.3762/bjoc.6.78

• the formation of by-products (tetracycles) observed in the reaction of 5 with the N-alkylated isatin intermediates 6 bearing the n = 3–5 linkers (Table 1). The tetracycle 4 had a slightly lower Rf than the desired hybrid 3 and was colorless or light yellow compared to the orange-colored hybrid 3. We

Concise methods for the synthesis of chiral polyoxazolines and their application in asymmetric hydrosilylation

• Wei Jie Li,
• Zun Le Xu and
• Sheng Xiang Qiu

Beilstein J. Org. Chem. 2010, 6, No. 29, doi:10.3762/bjoc.6.29

• the linkers and the substituents present on the oxazoline rings on the yield and enantioselectivity investigated. Compound 2 was identified as the best ligand of this family for the hydrosilylation of aromatic ketones. Keywords: aromatic ketone; hydrosilylation; polyoxazoline; rhodium; synthesis

• the coordination of 5 to [Rh(COD)Cl]2. In addition, the experimental results also show that flexible linkers of oxazoline rings result in low enantioselectivities (entries 11, 12, 14, 15). Table 2 shows that bisoxazoline 2 with benzyl group (entry 10) gave a higher ee than its counterpart

• –7) are described, which are much simpler and more efficient in comparison to those reported in the literature. With these chiral ligands as templates, the rhodium-catalyzed asymmetric hydrosilylation of aromatic ketones was carried out. The effects of the linkers of oxazoline rings and the

(Pseudo)amide-linked oligosaccharide mimetics: molecular recognition and supramolecular properties

• José L. Jiménez Blanco,
• Fernando Ortega-Caballero,
• Carmen Ortiz Mellet and
• José M. García Fernández

Beilstein J. Org. Chem. 2010, 6, No. 20, doi:10.3762/bjoc.6.20

• access pseudoamide-type oligosaccharide mimics. Calystegine B2 analogues 38 and 39 with urea-linked disaccharide structure. Rotameric equilibrium shift of 40 by formation of a bidentate hydrogen bond. Nucleotide analogues with thiourea and S-methylisothiouronium linkers. Rotameric equilibria for β-(1→6

Synthetic incorporation of Nile Blue into DNA using 2′-deoxyriboside substitutes: Representative comparison of (R)- and (S)-aminopropanediol as an acyclic linker

• Daniel Lachmann,
• Sina Berndl,
• Otto S. Wolfbeis and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2010, 6, No. 13, doi:10.3762/bjoc.6.13

• the 2′-deoxyriboside between the phosphodiester bridges. Similar propanediol derivatives have been used extensively as alternative and simplified phosphodiester linkers in the 1990s [19][20][21][22][23], and have been further explored for glycol nucleic acid (GNA) [24][25][26] twisted intercalating

• experimental result can be imaged by geometrically optimized DNA models. Our result is remarkable regarding opposite results with the L-/D-threoninol linkers [37][38][39][40] that revealed strong differences in stacking and also in function of attached chromophores depending on the chirality of the linker. We

Synthesis and binding studies of two new macrocyclic receptors for the stereoselective recognition of dipeptides

• Ana Maria Castilla,
• M. Morgan Conn and
• Pablo Ballester

Beilstein J. Org. Chem. 2010, 6, No. 5, doi:10.3762/bjoc.6.5

• synthetic receptors for peptides [11][12][13][14][15][16]. However, we believe that our design includes some novelties. To reduce the conformational flexibility and confer a certain degree of preorganization to this type of receptor, the use of one or two linkers connecting the two peptide strands is

• introduction of two linkers connecting the two peptide strands affording, a macrocyclic structure. In doing so, we expect that the molecular recognition properties of the designed receptor will also benefit from the macrocyclic effect [17][18][19][20]. Simple molecular modeling studies [21] revealed that a

• macrocycle, also allows for the possibility of binding short amino acid sequences not necessarily located on the edges of larger peptides. Other considerations, apart from preventing intramolecular hydrogen bond formation, related to the use of bis(alanyl)benzophenone rigid linkers include: a) to avoid

Versatile supramolecular reactivity of zinc-tetra(4-pyridyl)porphyrin in crystalline solids: Polymeric grids with zinc dichloride and hydrogen-bonded networks with mellitic acid

• Sophia Lipstman and
• Israel Goldberg

Beilstein J. Org. Chem. 2009, 5, No. 77, doi:10.3762/bjoc.5.77

• chemistry. In this work, it was found to be reactive in the assembly of both (a) a 2D polymeric array by a unique combination of self-coordination and coordination through external zinc dichloride linkers and (b) an extended heteromolecular hydrogen-bonded network with mellitic acid sustained by multiple

• , in which the porphyrin units are inter-coordinated via exocyclic metal ion linkers (e.g., tetrahedral CuI), has also been observed [5]. The latter mode of coordination polymerization, in which the peripheral pyridyl sites of different TPyP/MTPyP moieties can be readily bridged by various metal ion

• assemblies of varying dimensionality with the aid of exocyclic metal ion linkers capable of coordinating simultaneously to several neighboring ZnTPyP units [5][6][7][8][9][10][11]. The ZnTPyP can adopt in the above constructs either five-coordinate or six-coordinate geometries, which affects the architecture

Silica- bound benzoyl chloride mediated the solid- phase synthesis of 4H-3,1-benzoxazin- 4-ones

• Kurosh Rad-Moghadam and
• Somayeh Rouhi

Beilstein J. Org. Chem. 2009, 5, No. 13, doi:10.3762/bjoc.5.13

• . Apparently, owing to porous nature of silica chloride, a significant fraction of the silyl chloride linkers remains unreacted even in treatment with excess 4-hydroxybenzoic acid during the loading process. On the other hand, and for the same reason, many of the graft sites may be unavailable or more hindered