Anionic sigmatropic-electrocyclic-Chugaev cascades: accessing 12-aryl-5-(methylthiocarbonylthio)tetracenes and a related anthra[2,3-b]thiophene

• Laurence Burroughs,
• John Ritchie,
• Mkhethwa Ngwenya,
• Dilfaraz Khan,
• William Lewis and
• Simon Woodward

Beilstein J. Org. Chem. 2015, 11, 273–279, doi:10.3762/bjoc.11.31

• rearrangements of xanthates are normally considered to proceed via neutral species (such as 1c). The tetracenes 7 herein are not formed this way, instead the evidence here strongly suggests that the required [3,3]-6π–6π electrocyclic cascades takes place via anionic xanthate species before final capping with

Synthesis of an organic-soluble π-conjugated [3]rotaxane via rotation of glucopyranose units in permethylated β-cyclodextrin

• Jun Terao,
• Yohei Konoshima,
• Akitoshi Matono,
• Hiroshi Masai,
• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2014, 10, 2800–2808, doi:10.3762/bjoc.10.297

• , we then fixed this pseudo rotaxane structure, which was only present in 50% methanol aqueous solution. The capping reaction by Suzuki cross-coupling with pinacolboron derivative 7 bearing PM α-CD as the bulky stopper group was carried out under the same hydrophilic solvent conditions as in the

• or complexation of the pseudo linked [3]rotaxane with capping molecules, the fixed [3]rotaxane was isolated in chloroform solution. The formation of the fixed [3]rotaxane was confirmed by NMR analysis. Experiments are now in progress towards synthesizing IMWs bearing polythiophene or poly(para

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

• includes two extended PEG chains but also one bent PEG chain. Actually, our research group and Gao et al. have reported that γ-CD can form PPRXs with bulky molecules-appended PEG derivatives, implying the formation of γ-CD PPRX with one bent PEG chain [10][11]. On the other hand, the covalent capping of

Galactan synthesis in a single step via oligomerization of monosaccharides

• Marius Dräger and
• Amit Basu

Beilstein J. Org. Chem. 2014, 10, 2658–2663, doi:10.3762/bjoc.10.279

• capping the product mixture as TBS ethers greatly improved product separation, resulting in higher overall yields for the process (Table 1, entry 11). Finally, we reexamined the use of the TBS protected glycosyl donor 1 under the optimized conditions of Table 1, entry 11, and confirmed that the presence

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

• ][4]. For example, if cleavable end-capping groups such as disulfide groups are introduced at both ends of PRX, the threaded α-CD molecules could be completely released by disassembling the PRX structure when a preferable stimulation such as dithiothreitol (DTT) is applied to the cleavable end-capping

• with minimal chemical reaction, methacrylate-functionalized PRX with degradable end-capping groups is anticipated to be a useful molecular platform for the development of degradable crosslinking agents. In this study, resin monomer-soluble, methacrylate-functionalized PRX with degradable end-capping

Encapsulation of biocides by cyclodextrins: toward synergistic effects against pathogens

• Véronique Nardello-Rataj and
• Loïc Leclercq

Beilstein J. Org. Chem. 2014, 10, 2603–2622, doi:10.3762/bjoc.10.273

• several papers [82][83]. In 2010, Jaiswal et al. proposed to use of β-CD as a capping agent [84]. The reduction of silver salts using sodium borohydride followed by β-CD capping allows the synthesis of stable spherical silver nanoparticles. The authors proved by dynamic light scattering that the average

• organic to the aqueous phase containing β-CD as a capping agent [85]. The “β-CD/silver” nanoparticles were purified and characterized by spectroscopic and microscopic analyses. The results showed that the encapsulation confered a considerable stability to the nanoparticles. Moreover, the silver

• ]. Similarly, Priya et al. used sodium citrate as a reducing agent followed by capping with β-cyclodextrin for the preparation of silver nanoparticles [87] with an increased biocidal activity against P. aeruginosa and S. aureus of the β-CD capped silver nanoparticles compared to the uncapped ones. The proposed

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

• 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

• reaction yielded graft polyrotaxanes in a good yield, demonstrating a significant simplification of the synthesis of graft polyrotaxanes. Keywords: branch structure; cyclodextrin; end capping; graft polyrotaxane; polyrotaxane; Introduction Polyrotaxanes, interlocked molecules composed of polymer chains

• inclusion complex with CDs, 3) end capping, 4) chemical modification of CDs, and 5) grafting. The first three steps constitute the synthesis of polyrotaxane. The fourth process is necessary to dissociate the columnar crystal of CDs formed by hydrogen bonds and to disperse the CDs within the backbone

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

• impact of end-capping groups on the self-assembly direction of γ-CDs with an incoming polymer chain, a PPO-PEO-PPO, triblock copolymer was studied. The copolymer had an average degree of polymerization (DP) of five PPO flanking blocks instead of pure PEG in order to enlarge the volume of the end-capping

• the conformational differences in the double-chain and single-chain stranded PPRs. This implies that PEG tends to be bent in order to quickly pass through the inner cavity of γ-CDs when the 2-bromoisobutyryl initiating groups are attached to two ends. However, if these end-capping groups were replaced

• end-capping reaction with a fourfold molar excess of 2-bromoisobutyryl bromide in CH2Cl2. PPO-PEO-PPO (9.16 g, 2 mmol), DMAP (488 mg, 4 mmol) and TEA (404 mg, 4 mmol) were dissolved in 20 mL CH2Cl2 in a 100 mL three-neck round-bottom flask. Thereafter, another 20 mL of CH2Cl2 containing 2

Reversibly locked thionucleobase pairs in DNA to study base flipping enzymes

• Christine Beuck and
• Elmar Weinhold

Beilstein J. Org. Chem. 2014, 10, 2293–2306, doi:10.3762/bjoc.10.239

• nucleotides. For unnatural nucleotides, the coupling time was extended to 90 s. Fast deprotectable tert-butylphenoxyacetyl (TAC) protected A, C and G phosphoamidites and coupling reagents including TAC anhydride as capping reagent were purchased from Proligo. N6-Methyl-2’-deoxyadenosine (AMe), 6-thio-2

Molecular recognition of AT-DNA sequences by the induced CD pattern of dibenzotetraaza[14]annulene (DBTAA)–adenine derivatives

• Marijana Radić Stojković,
• Marko Škugor,
• Łukasz Dudek,
• Jarosław Grolik,
• Julita Eilmes and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2175–2185, doi:10.3762/bjoc.10.225

• , Supporting Information File 1). The choice of long polynucleotides ensures that significant binding of the DBTAA moiety at the ends of the double strands (“capping”) can be neglected and that our investigations indeed sense the differences of the secondary structure (from minor/major groove) of the studied

The effect of permodified cyclodextrins encapsulation on the photophysical properties of a polyfluorene with randomly distributed electron-donor and rotaxane electron-acceptor units

• Aurica Farcas,
• Ana-Maria Resmerita,
• Pierre-Henri Aubert,
• Flavian Farcas,
• Iuliana Stoica and
• Anton Airinei

Beilstein J. Org. Chem. 2014, 10, 2145–2156, doi:10.3762/bjoc.10.222

• of approaches were examined, e.g., copolymerization [7][8][9][10][11], end-capping with sterically hindered groups [12], introduction of donor (D) and acceptor (A) moieties, to form statistically [13][14] or alternating D–A units in the main chain [15][16][17][18]. The coupling of D–A units has been

Photoswitchable precision glycooligomers and their lectin binding

• Daniela Ponader,
• Sinaida Igde,
• Marko Wehle,
• Katharina Märker,
• Mark Santer,
• David Bléger and
• Laura Hartmann

Beilstein J. Org. Chem. 2014, 10, 1603–1612, doi:10.3762/bjoc.10.166

• carefully washing the resin with DMF. Capping of N-teminal site: The free primary amine, obtained after final Fmoc cleavage, was capped with an acetyl group by the addition of 2.5 mL acetic anhydride. After shaking the mixture for 15 min, the resin was washed with DMF and DCM. Cleavage from solid phase: 30

• )-3: This structure was synthesized by applying the general coupling protocol three times with building blocks in the sequence TDS, AZO, TDS. After capping the primary amine, two galactose units were conjugated to the scaffold according to the general CuAAC protocol. The product was cleaved from the

• ;. ESIMS [M + H]+: calcd for C60H89N17O20, 1368.6; found, 1368.4; [M + 2H]2+ 684.8; found, 684.8, [M + 3H]3+ 456.9; found, 457.0. AZO-Gal(1,3,5)-5: This structure was synthesized by applying the general coupling protocol five times with building blocks in the sequence TDS, AZO, TDS, AZO, TDS. After capping

Design, automated synthesis and immunological evaluation of NOD2-ligand–antigen conjugates

• Marian M. J. H. P. Willems,
• Gijs G. Zom,
• Nico Meeuwenoord,
• Ferry A. Ossendorp,
• Herman S. Overkleeft,
• Gijsbert A. van der Marel,
• Jeroen D. C. Codée and
• Dmitri V. Filippov

Beilstein J. Org. Chem. 2014, 10, 1445–1453, doi:10.3762/bjoc.10.148

• the antigenic peptide was protected with the methyl trityl (Mtt) protective group, allowing the modification of both the N- or C-terminal end at the final stage of the synthesis. In a standard elongation cycle using HCTU as a coupling reagent, acetic anhydride as capping reagent and piperidine to

Solid-phase-supported synthesis of morpholinoglycine oligonucleotide mimics

• Tatyana V. Abramova,
• Sergey S. Belov,
• Yulia V. Tarasenko and
• Vladimir N. Silnikov

Beilstein J. Org. Chem. 2014, 10, 1151–1158, doi:10.3762/bjoc.10.115

• the support and reactants. Swelling and capping steps were omitted beginning the second cycle. After each cycle, a small sample of the support was subjected to aqueous ammonia treatment to analyse resulting oligomers. The homogeneity and the structure of the products formed after each cycle were

End-labeled amino terminated monotelechelic glycopolymers generated by ROMP and Cu(I)-catalyzed azide–alkyne cycloaddition

• Ronald Okoth and
• Amit Basu

Beilstein J. Org. Chem. 2013, 9, 608–612, doi:10.3762/bjoc.9.66

• Ronald Okoth Amit Basu Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA 10.3762/bjoc.9.66 Abstract Functionalizable monotelechelic polymers are useful materials for chemical biology and materials science. We report here the synthesis of a capping agent that can be

• accomplished by amidation with an azido-amine linker followed by Cu(I)-catalyzed azide–alkyne cycloaddition with propargyl sugars. Subsequent Teoc deprotection and conjugation with pyrenyl isothiocyanates afforded well-defined end-labeled glycopolymers. Keywords: capping agent; carbohydrate; glycan; olefin

• used as probes of biologically relevant recognition events and to functionalize surfaces [10]. Monotelechelic polymers have been obtained by the use of prefunctionalized initiators, direct end-capping with functionalized capping agents (terminating agents), and through the use of sacrificial monomers

Glycosylation efficiencies on different solid supports using a hydrogenolysis-labile linker

• Mayeul Collot,
• Steffen Eller,
• Markus Weishaupt and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2013, 9, 97–105, doi:10.3762/bjoc.9.13

• functionalized with linker 1 (Scheme 4). Coupling to both chloro-functionalized Merrifield resin 16 and Jandajel 17 was achieved by a tetrabutylammonium iodide (TBAI) mediated substitution in the presence of Cs2CO3. Capping of unreacted chlorides by cesium acetate and subsequent acidic hydrolysis of the THP

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

• the fast release and analysis of glycosides. Linker-functionalized resin 11 contains both cleavage sites, and was accessed by coupling the cesium salt of linker 10 with Merrifield chloride resin prior to capping and deprotection (Scheme 2). A second resin 12, containing only the safety-catch cleavage

• site, was created by installing linker 10 on Merrifield amine resin by treatment with DIC and HOBt (Scheme 2) [15]. After capping with acetic anhydride and removing the THP protecting group with p-TsOH·H2O, the functionalized resin 12 was ready for use. Finally, a third linker-functionalized resin 16

• possible explanation is provided by Unverzagt and co-workers [27], who reported, when using another acylsulfonamide safety-catch linker on a solid support, that capping the remaining amino group using acetic anhydride preactivates the sulfamyl group. To test this hypothesis, linker 10 was transformed by

Peptides presenting the binding site of human CD4 for the HIV-1 envelope glycoprotein gp120

• Julia Meier,
• Kristin Kassler,
• Heinrich Sticht and
• Jutta Eichler

Beilstein J. Org. Chem. 2012, 8, 1858–1866, doi:10.3762/bjoc.8.214

• capping step using a mixture of acetic anhydride/pyridine/DMF (1:2:3; 30 min). The Fmoc group was removed by using 20% piperidine/DMF (20 min). After completing the sequence, the N-terminal amino group was acetylated. Peptides were cleaved from the resin by using Reagent K (TFA/water/phenol/thioanisole

Automated synthesis of sialylated oligosaccharides

• Davide Esposito,
• Mattan Hurevich,
• Bastien Castagner,
• Cheng-Chung Wang and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2012, 8, 1601–1609, doi:10.3762/bjoc.8.183

• hydrogenolysis affording good yields of the trisaccharide 16, equipped with an amino spacer for conjugation. The synthesis of GM3 trisaccharide 16 proved that compound 4 is efficient for installing the capping sialyl α-(2→3) galactose unit into synthetic oligosaccharides. Furthermore, conditions applied to the

Synthesis and characterization of low-molecular-weight π-conjugated polymers covered by persilylated β-cyclodextrin

• Aurica Farcas,
• Ana-Maria Resmerita,
• Andreea Stefanache,
• Mihaela Balan and
• Valeria Harabagiu

Beilstein J. Org. Chem. 2012, 8, 1505–1514, doi:10.3762/bjoc.8.170

• 1:1 5,5'-dibromo-2,2'-bithiophene inclusion complex in PS-βCD (BTc) and 9,9-dioctylfluorene-2,7-bis(trimethylene borate) (DOF) as a bulky molecule followed by a small excess of DOF at the end of polymerization and, finally, 3-bromothiophene (3T) as a monofunctional end-capping reagent, as

• illustrated in Scheme 1. In order to analyse the influence of end-capping reagents on the photophysical properties we changed the termination of the growing chains to 3T instead of bromobenzene, as in previously reported results [12]. A noncomplexed PDOF-BT copolymer was also synthesized by polycondensation

• the influence on the surface morphological properties induced by using 3T as an end-capping reagent instead of bromobenzene [12], AFM experiments were also performed. The 2D AFM images of the top surface of both copolymer films, within the same scan areas of 2 × 2 μm2 are shown in Figure 7a and Figure

Combined bead polymerization and Cinchona organocatalyst immobilization by thiol–ene addition

• Kim A. Fredriksen,
• Tor E. Kristensen and
• Tore Hansen

Beilstein J. Org. Chem. 2012, 8, 1126–1133, doi:10.3762/bjoc.8.125

• . Consequently, we do not believe this to be an intrinsic property of our thiol–ene polymer beads, connected to the effect of free thiol groups. In addition, capping free thiol groups on beforehand by treatment with excess methyl acrylate did not affect the performance in this transformation. Catalyst 12 was

Synthesis and characterization of Sant-75 derivatives as Hedgehog-pathway inhibitors

• Chao Che,
• Song Li,
• Bo Yang,
• Shengchang Xin,
• Zhixiong Yu,
• Taofeng Shao,
• Chuanye Tao,
• Shuo Lin and
• Zhen Yang

Beilstein J. Org. Chem. 2012, 8, 841–849, doi:10.3762/bjoc.8.94

• -substituted precursor 7c by the reduction of the nitro group to an amino group using an FeCl3–Zn system [41]. Subsequently, capping the amino group with a sulfonyl or acetyl group led to 7n and 7o, respectively. In regard to hydroxy or acid modification, the demethylation or hydrolysis released the

• compounds as Hedgehog-pathway inhibitors. Therefore, the emphasis of the fourth series of structural optimization was placed on the nitrogen atom through capping of the amino group with various acyl chlorides, delivering the corresponding amides 21a–j. It should be noted that the capping of the amino group

Synthesis of functionalized macrocyclic derivatives of trioxabicyclo[3.3.0]nonadiene

• Sabine Leber,
• Gert Kollenz and
• Curt Wentrup

Beilstein J. Org. Chem. 2012, 8, 738–743, doi:10.3762/bjoc.8.83

• the sterically hindering tert-butyl groups make it an interesting spacer group, and it thus has been applied successfully in syntheses of several macrocyclic polyether and polymethyleneoxy rings containing one, two or three bisdioxine units, e.g., 4 and 5 (Scheme 1) [4][5]. Capping of a calix[6]arene

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

• -residues to twofold for the first and onefold for the second coupling. The completion of these couplings was indicated by a negative Kaiser test. Prior to each deprotection step, capping of the possibly nonacylated N-termini was carried out by treatment with 10% acetic anhydride and 10% DIEA in DMF (3 × 10

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