Azobenzene dye-coupled quadruply hydrogen-bonding modules as colorimetric indicators for supramolecular interactions

• Yagang Zhang and
• Steven C. Zimmerman

Beilstein J. Org. Chem. 2012, 8, 486–495, doi:10.3762/bjoc.8.55

• ) by their coupling to azobenzene dyes allowing them to serve as colorimetric indicators for supramolecular interactions. Beyond reporting the straightforward coupling of DAN and DeUG to azobenzene dyes, we show that the dye-recognition-unit conjugates act as selective polymer colorants (Figure 2). The

A novel high-yield synthesis of aminoacyl p-nitroanilines and aminoacyl 7-amino-4-methylcoumarins: Important synthons for the synthesis of chromogenic/fluorogenic protease substrates

• Xinghua Wu,
• Yu Chen,
• Herve Aloysius and
• Longqin Hu

Beilstein J. Org. Chem. 2011, 7, 1030–1035, doi:10.3762/bjoc.7.117

• -amino-4-methylcoumarin; p-nitroaniline; proteolytic substrate; selenocarboxylate/azide amidation; synthon; Introduction Chromogenic and fluorogenic amino acid/peptide conjugates are widely used as substrates in enzyme assays for protease activity and specificity [1]. Proteolytic cleavage of the amino

• acid/peptide conjugates liberates the free chromophore or fluorophore, allowing the convenient determination of the rate of enzyme catalysis with a UV or fluorescence spectrophotometer. p-Nitroaniline (pNA) is one of the most commonly used chromogenic reagents. The synthesis of peptide-pNAs usually

• conjugates. 7-Azido-4-methylcoumarin was readily prepared from 7-AMC by the standard diazotization/sodium azide protocol in a yield of 92%. Under the same reaction conditions described above, the amidation of 7-azido-4-methylcoumarin with various amino selenocarboxylates gave the desired Nα-protected

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

• the kinetics of photoinduced electron transfer (PET). The three analogous isomeric lysine conjugates cleaved DNA with different efficiencies (34, 15, and 0% of ds DNA cleavage for p-, m-, and o-substituted lysine conjugates, respectively) consistent with the alkylating ability of the respective

• acetamides. The significant protecting effect of the hydroxyl radical and singlet oxygen scavengers to DNA cleavage was shown only with m-lysine conjugate. All three isomeric lysine conjugates inhibited human melanoma cell growth under photoactivation: The p-conjugate had the lowest CC50 (50% cell

• lysine (C-lysine conjugates in Figure 1) displayed a combination of unique properties such as the ability to cause true double-strand (ds) DNA cleavage [24], amplification of ds cleavage dramatically at the lower pH of cancer cells [25], as well as the ability to recognize terminal phosphate monoester

Advances in synthetic approach to and antifungal activity of triazoles

• Kumari Shalini,
• Nitin Kumar,
• Sushma Drabu and
• Pramod Kumar Sharma

Beilstein J. Org. Chem. 2011, 7, 668–677, doi:10.3762/bjoc.7.79

• occupies the most important place in the treatment of fungal diseases. The triazole derivatives noted below were synthesized by various groups and show antifungal activity. Novel 1,2,3-triazole-linked with β-lactam–bile acid conjugates were prepared via 1,3-dipolar cycloaddition reactions of azido β

Exceptionally small supramolecular hydrogelators based on aromatic–aromatic interactions

• Junfeng Shi,
• Yuan Gao,
• Zhimou Yang and
• Bing Xu

Beilstein J. Org. Chem. 2011, 7, 167–172, doi:10.3762/bjoc.7.23

• less explored. We have shown that aromatic–aromatic interactions induce the self-assembly of glycopeptides [30] or pentapeptidic derivatives [31] in water to form nanofibers and supramolecular hydrogels. These results, together with the supramolecular hydrogelators made from dipeptide conjugates with

Cross-metathesis of allylcarboranes with O-allylcyclodextrins

• Ivan Šnajdr,
• Zbyněk Janoušek,
• Jindřich Jindřich and
• Martin Kotora

Beilstein J. Org. Chem. 2010, 6, 1099–1105, doi:10.3762/bjoc.6.126

• , Czech Republic 10.3762/bjoc.6.126 Abstract Cross-metathesis between allylcarboranes and O-allylcyclodextrins was catalyzed by Hoveyda–Grubbs 2nd generation catalyst in toluene. The corresponding carboranyl-cyclodextrin conjugates were isolated in 15–25% yields. Keywords: carborane; catalysis; cross

• carborane-cyclodextrin conjugates. Herein, we report our preliminary results. Results and Discussion Although studies on the inclusion of carboranes into cyclodextrins have previously been reported [9][10][11][12][13], a synthesis of cyclodextrin-carborane conjugates connected by a linker has not been, to

• ]), consequently, there is considerable interest in the synthesis of water soluble carborane derivatives. One strategy to access such compounds is based on the synthesis of carborane conjugates bearing a water-soluble moiety. With this in mind, we envisioned that this concept could be realized by the synthesis of

Synthesis of 6-PEtN-α-D-GalpNAc-(1–>6)-β-D-Galp-(1–>4)-β-D-GlcpNAc-(1–>3)-β-D-Galp-(1–>4)-β-D-Glcp, a Haemophilus influenzae lipopolysacharide structure, and biotin and protein conjugates thereof

• Andreas Sundgren,
• Martina Lahmann and
• Stefan Oscarson

Beilstein J. Org. Chem. 2010, 6, 704–708, doi:10.3762/bjoc.6.80

• spacer amino group but with a protected phosphoethanolamino group. Conjugation of the spacer amino group to biotin or dimethyl squarate followed by deprotection of the phosphoethanolamino group and, in the case of the squarate derivative, further reaction with a protein then afforded the title conjugates

• . Conclusion: An effective synthesis of a biologically interesting pentasaccharide structure has been accomplished. The target pentasaccharide, an α-GalNAc substituted lacto-N-neotetraose structure, comprises a phosphoethanolamine motif and a spacer aglycon. Through the spacer, biotin and protein conjugates of

• of 23, from which the Boc-group was removed by acid hydrolysis to afford derivative 24. Protein conjugations were performed by reaction of 24 (20 equiv) with human serum albumin (HSA). Compound 20 was similarly activated with dimethyl squarate and conjugated to HSA. MALDI-TOF MS of the HSA-conjugates

Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans – an approach to carbohydrate mimetics

• Fabian Pfrengle and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 75, doi:10.3762/bjoc.6.75

• (particle diameter 6 nm). After sulfation of the hydroxyl groups the multivalent conjugates obtained displayed strong binding to P- and L-selectins, thus demonstrating that compounds such as 24 and 28 are of interest for the development of new anti-inflammatory agents [27][28]. Inspired by these first

• findings, we decided to prepare also smaller conjugates for evaluation as selectin ligands. Thus, the free hydroxyl groups of aminopyrans 24 and 28 were temporarily protected as TMS ethers in order to achieve smooth reaction with 1,3,5-benzenetricarboxylic acid chloride (Scheme 14) [29]. After successful

Synthesis of glycosylated β³-homo-threonine conjugates for mucin-like glycopeptide antigen analogues

• Florian Karch and
• Anja Hoffmann-Röder

Beilstein J. Org. Chem. 2010, 6, No. 47, doi:10.3762/bjoc.6.47

• bioavailability for tumour immunotherapy. Towards this end, TN and TF antigen conjugates O-glycosidically linked to Fmoc-β3-homo-threonine were prepared in good yield via Arndt–Eistert homologation of the corresponding glycosyl α-amino acid derivative. By incorporation of TN-Fmoc-β3hThr conjugate into the 20

• proteins involved in fundamental biological recognition events of cell adhesion, cell differentiation and cell growth [1][2][3]. As a consequence, synthetic oligosaccharides and their conjugates are recognised as important tools for the expanding field of chemical biology [4]. Aberrant glycosylation of

• limited metabolic stability of the glycopeptide conjugates represents a major obstacle for the development of efficient carbohydrate-based vaccines. Various strategies towards the incorporation of non-natural hydrolysis resistant carbohydrate analogues into vaccine constructs have been pursued. For

Symmetrical and unsymmetrical α,ω-nucleobase amide-conjugated systems

• Sławomir Boncel,
• Maciej Mączka,
• Krzysztof K. K. Koziol,
• Radosław Motyka and
• Krzysztof Z. Walczak

Beilstein J. Org. Chem. 2010, 6, No. 34, doi:10.3762/bjoc.6.34

• NMR spectra of all newly synthesised compounds. Acknowledgements The authors would like to thank the Institute of Tropical Diseases in Geneva, Switzerland for performing the initial tests of antiprotozoal activity for the unsymmetrical short-linkage α,ω-nucleobase amide-conjugates. These

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

(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

• specifically to the minor groove of the DNA. A pentameric thymidyl DNG incorporating bis-benzimidazole (Hoechst 33258) ligand (64) was synthesised [105]. The stability of DNG-Hoechst conjugates 64 and 65 with a 30-mer double-strand DNA (dsDNA) and single-strand DNA (ssDNA) were evaluated. Fluorescent emission

• studies showed that hybridization of DNG-Hoechst conjugates 64 and 65 to dsDNA enhances the stability of the triple helix through simultaneous minor groove binding by the tethered Hoechst 33258 ligand. Furthermore, Hoechst 33258 is able to enhance the stability of the duplex DNG·DNA with a flexible minor

• conjugates. Protected derivatives of 2,6-diamino-2,6-dideoxy-β-D-glucopyranosyl carboxylic acid 22 and 23. Cyclic homo-oligomers containing glucopyranoid-SAAs. Cyclic tetramers of L-rhamno- and D-gulo-configured oxetane-SAAs. Aminoglycosidic antibiotics of the glycocinnamoylspermidine family. Approaches to

Synthesis of rigidified flavin–guanidinium ion conjugates and investigation of their photocatalytic properties

• Harald Schmaderer,
• Mouchumi Bhuyan and
• Burkhard König

Beilstein J. Org. Chem. 2009, 5, No. 26, doi:10.3762/bjoc.5.26

• and flavin should enhance the rate of photoinduced electron transfer processes, which strongly depend on distance [44]. We present here the synthesis of geometrically defined flavin-guanidinium ion conjugates based on a Kemp’s acid skeleton (Scheme 1). The guanidinium moiety should serve as a hydrogen

• ). Structure of compound 1 in the solid state. Calculated lowest energy conformation of 1 in the gas phase (AM1, Spartan program package). Flavin–guanidinium ion conjugates 1 and 2 and tetraacetyl riboflavin (3). Synthesis of flavins 1 and 2. Conditions: (i) DMAP, H2O, Δ, 20 h, 71–78%, (ii) HOBt, EDC, NEt(iPr

Synthesis of coumarin or ferrocene labeled nucleosides via Staudinger ligation

• Ivana Kosiova,
• Andrea Janicova and
• Pavol Kois

Beilstein J. Org. Chem. 2006, 2, No. 23, doi:10.1186/1860-5397-2-23

• spectral characteristics of the isolated products are summarised in Table 1. We found that all newly prepared conjugates display only one peak in the fluorescence spectrum in methanol. The process of conjugation did not cause a shift in the absorption and fluorescence maxima of our compounds, in comparison