Intramolecular bridges formed by photoswitchable click amino acids

• Christian Hoppmann,
• Ronald Kühne and
• Michael Beyermann

Beilstein J. Org. Chem. 2012, 8, 884–889, doi:10.3762/bjoc.8.100

• presence of glutathione as an additional thiol the click reaction of the PSCaa occurs intramolecularly with the cysteine rather than with the glutathione, indicating that the click reaction may be used even under reducing conditions occurring in living cells. Keywords: azobenzene; helical conformation

• ; isomerization; molecular switches; photoswitchable click amino acid; thiol–ene click; Introduction Photoswitchable bridges that are site-specifically incorporated into proteins allow the conformation and activity of proteins to be modulated by light. In contrast to common bivalent thiol reactive azobenzene

• switches [1][2][3][4][5], the PSCaa described here (Scheme 1) is an α-amino acid containing, besides an azobenzene unit, a vinyl function that can react specifically with a cysteine within a putative conformational domain of a peptide or a protein by light-induced thiol–ene click reaction [6][7][8][9]. The

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

• revealed that the overall degree of switching was independent of the connected azo-units. However, one of the azobonds in the bis-azobiphenyl is isomerized preferentially despite the high structural similarity. Keywords: azobenzene; cross-coupling reaction; foldamer; molecular switches; photochromism

• ; Introduction The possibility to control structures on the molecular level in a reversible manner by using an external stimulus has fascinated scientists for a long time. One of the earliest reports on a molecular entity that can be influenced in this way concerns the azobenzene scaffold. Since this discovery

• by Hartley in 1937 [1] many more compounds showing such a photochromism have been reported [2]. However, the azobenzene moiety still remains one of the most popular “work horses” in this respect [3][4][5][6]. The reason can probably be found in its relatively easy synthetic accessibility combined

Molecular switches and cages

• Dirk Trauner

Beilstein J. Org. Chem. 2012, 8, 870–871, doi:10.3762/bjoc.8.97

• (Rück-Braun, Hoppmann). Two reviews discuss cis-azobenzenes with rapid thermal isomerization kinetics (Velasco), and highlight the azobenzene moiety as one of the smallest light-driven molecular motors conceivable (Merino). Issues of bistability are also addressed in an account on shape-persistent

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

• Yagang Zhang Steven C. Zimmerman Department of Chemistry, 600 South Mathews Avenue, University of Illinois, Urbana, IL 61801, USA 10.3762/bjoc.8.55 Abstract The facile coupling of azobenzene dyes to the quadruply hydrogen-bonding modules 2,7-diamido-1,8-naphthyridine (DAN) and 7-deazaguanine urea

• (DeUG) is described. The coupling of azobenzene dye 2 to mono-amido DAN units 4, 7, and 9 was effected by classic 4-(dimethylamino)pyridine (DMAP)-catalyzed peptide synthesis with N-(3-dimethylaminopropyl)-N’-ethyl carbodiimide hydrochloride (EDC) as activating agent, affording the respective amide

• products 5, 8, and 10 in 60–71% yield. The amide linkage was formed through either the aliphatic or aromatic ester group of 2, allowing both the flexibility and absorption maximum to be tuned. Azobenzene dye 1 was coupled to the DeUG unit 11 by Steglich esterification to afford the product amide 12 in 35

Liquid-crystalline nanoparticles: Hybrid design and mesophase structures

• Gareth L. Nealon,
• Romain Greget,
• Cristina Dominguez,
• Zsuzsanna T. Nagy,
• Daniel Guillon,
• Jean-Louis Gallani and
• Bertrand Donnio

Beilstein J. Org. Chem. 2012, 8, 349–370, doi:10.3762/bjoc.8.39

• to emphasise the wider applicability of this approach to nanohybrid science. Fundamental studies into the photochemical activity of lipophilic azobenzene- and stilbene thiols (10, Figure 12) on Au NPs surfaces were reported [66], which indicated a chromophore-to-NP distance dependence of the

• photoisomerisation and photodimerisation efficiency in these systems. Interesting examples of the potential application of this type of approach were shown by the grafting of similar azobenzene ligands 11 (Figure 12) to the surfaces of γ-Fe2O3 [67] and FePt [68] NPs, which exhibited a photoswitchable change in

Continuous proline catalysis via leaching of solid proline

• Suzanne M. Opalka,
• Ashley R. Longstreet and
• D. Tyler McQuade

Beilstein J. Org. Chem. 2011, 7, 1671–1679, doi:10.3762/bjoc.7.197

• , and finally azobenzene by product disproportionation [53][54][55]. Byproduct suppression is both solvent and temperature dependent. Hayashi reported that when the reaction is performed at room temperature in acetonitrile with 30 mol % proline, the reaction is complete in 10 min, but achieves only 29

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

• ′-deoxyribose substitutes by influencing the stacking orientation of an attached azobenzene dye. The configuration of the linker decides if the dye protrudes towards the major or minor groove, which subsequently leads to an enhanced or diminished stability of the whole DNA duplex [42]. Herein, we want to