Synthesis and characterization of a new photoinduced switchable β-cyclodextrin dimer

• Florian Hamon,
• Claire Blaszkiewicz,
• Marie Buchotte,
• Estelle Banaszak-Léonard,
• Hervé Bricout,
• Sébastien Tilloy,
• Eric Monflier,
• Christine Cézard,
• Laurent Bouteiller,
• Christophe Len and
• Florence Djedaini-Pilard

Beilstein J. Org. Chem. 2014, 10, 2874–2885, doi:10.3762/bjoc.10.304

• high solubility in water. The photoisomerization properties were studied by UV–vis and HPLC and supported by ab initio calculations. The cis/trans ratio of AZO-CDim 1 is 7:93 without irradiation and 37:63 after 120 min of irradiation at 365 nm; the reaction is reversible after irradiation at 254 nm

• cavities of cis-AZO-CDim 1 are complexed simultaneously by two adamantyl units of the guest forming a 1:1 complex while trans-AZO-CDim 1 seems to lead to the formation of supramolecular polymers with an n:n stoichiometry. Keywords: azobenzene; cyclodextrins; inclusion complex; photoisomerization

• photoisomerization of the guests and this property has been widely applied to molecular shuttles, motors, information storage [24][25] and catalysis [26]. Some examples of azobenzene-linked CD dimers can be found in the literature but they generally suffer from arduous purification steps and very low yields [27][28

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

• absorbance spectra of both photoswitchable glycooligomers (see Figure 2 for the spectrum of Azo-Gal(1,3,5)-5). The presence of well-defined isosbestic points at 290 nm and 395 nm indicates a clean photoisomerization process. The composition at the photostationary state (PSS) was analyzed by UPLC using

• light-induced change in the geometry of the glycooligomers. Binding studies of the galactose-functionalized glycooligomers showed specific binding to PA-IL and a controlled reduction in binding affinity upon E → Z photoisomerization. We proposed a first model to explain our findings based on molecular

• solid support followed by on-resin functionalization of alkyne side chains with sugar azide ligands and final cleavage from the support. Characterization of the E → Z photoisomerization (λ = 360 nm) of Azo-Gal(1,3,5)-5 in buffer solution at 25 °C via UV–vis absorption spectroscopy measurements

Cyclization of substitued 2-(2-fluorophenylazo)azines to azino[1,2-c]benzo[d][1,2,4]triazinium derivatives

• Aleksandra Jankowiak,
• Emilia Obijalska and
• Piotr Kaszynski

Beilstein J. Org. Chem. 2013, 9, 1873–1880, doi:10.3762/bjoc.9.219

• photochemically. Thus, the success of the reaction depends on i) the efficient access to the Z-isomer, and ii) the relative rates of cyclization vs back isomerization to the E-isomer. The supply of the requisite Z-isomers of the azoazines is best accomplished by photoisomerization of the E-isomers, since the Z

Synthesis and testing of the first azobenzene mannobioside as photoswitchable ligand for the bacterial lectin FimH

• Vijayanand Chandrasekaran,
• Katharina Kolbe,
• Femke Beiroth and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2013, 9, 223–233, doi:10.3762/bjoc.9.26

• 56: Photoisomerization studies, UV–vis spectra, NMR spectra, bioassay and docking results. Acknowledgements Financial support by the DFG (collaborative network SFB677) and FCI (Fonds der Chemischen Industrie) is gratefully acknowledged. We thank Max Britz for technical assistance.

Amino-substituted diazocines as pincer-type photochromic switches

• Hanno Sell,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2013, 9, 1–7, doi:10.3762/bjoc.9.1

• thermal half-life of the trans isomer, however, is drastically increased (3,3’-diamino-EBAB 4: 74 h, 3,3’-diacetamido-EBAB 5: 46 h). The EBAB derivatives upon photoisomerization perform a pincer-like motion. Diacetamido derivative 5 binds ethylenediamine better in its cis (closed) form than in its trans

A bisazobenzene crosslinker that isomerizes with visible light

• Subhas Samanta,
• Harris I. Qureshi and
• G. Andrew Woolley

Beilstein J. Org. Chem. 2012, 8, 2184–2190, doi:10.3762/bjoc.8.246

• -modified biomolecules require longer azobenzene derivatives that undergo large end-to-end distance changes upon photoisomerization. In addition, isomerization that occurs with visible rather than UV irradiation is preferred for biological applications. Results: We report the synthesis and characterization

• the effects of crosslinkers on protein folding led to the conclusion that photocontrol of folding is best achieved by using rigid crosslinkers that undergo a large change in end-to-end distance upon photoisomerization [6]. Previously, we reported the design and synthesis of the rigid bisazobenzene

• to ~80% trans–cis isomerization under favorable conditions. The suitability of this photoswitch for biological systems would be enhanced if the wavelengths required for photoisomerization were longer, so that UV light was not required. UV light is highly scattered by biological samples and can be a

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

• encapsulating some important agricultural chemicals. In this case, release is controlled and has a slow profile [27]. Finally, nanosponges can also be used in polymer processing to improve flame-retardant properties [28][29] and in enantio-differentiating photoisomerization reactions [30]. Application of

Design and synthesis of a photoswitchable guanidine catalyst

• Philipp Viehmann and
• Stefan Hecht

Beilstein J. Org. Chem. 2012, 8, 1825–1830, doi:10.3762/bjoc.8.209

• leads to a separation of the n→π* and π→π* bands for the (Z)-isomer. As expected, an inverse behavior is observed upon irradiation at 254 nm, inducing photoisomerization of guanidine 2Z back to its precursor 2E (Figure 2b). The amount of isomer 2E in the resulting pss was determined to be 94%. The same

• nearly quantitative Z→E photoisomerization, giving 92% of 2E in the pss, is obtained upon irradiation at 430 nm. Related to the supposed function of guanidine as a switchable catalyst, these experiments demonstrate the reversible photoisomerization of the azobenzene moiety. Nevertheless, the switching

• properties can still be improved, in particular to obtain a pss with higher (Z)-content in the E→Z photoisomerization. Besides the photo-induced Z→E isomerization, the thermal back-reaction of guanidine 2Z was examined as well (Figure 2c). Based on the measured UV–vis and UPLC data and assuming a first-order

Cyclodextrin nanosponge-sensitized enantiodifferentiating photoisomerization of cyclooctene and 1,3-cyclooctadiene

• Wenting Liang,
• Cheng Yang,
• Masaki Nishijima,
• Gaku Fukuhara,
• Tadashi Mori,
• Andrea Mele,
• Franca Castiglione,
• Fabrizio Caldera,
• Francesco Trotta and
• Yoshihisa Inoue

Beilstein J. Org. Chem. 2012, 8, 1305–1311, doi:10.3762/bjoc.8.149

• the photochirogenic reaction. Keywords: cyclodextrins; 1,3-cyclooctadiene; cyclooctene; nanosponge; photochirogenesis; photoisomerization; Introduction The precise control of chiral photoreactions, or photochirogenesis, is one of the most challenging topics in current photochemistry [1][2][3]. Weak

• photochirogenesis to use pyromellitate-linked polymeric β- and γ-CDs, termed “cyclodextrin nanosponges” (CDNSs) [25][26][27][28][29][30][31][32][33], as sensitizing hosts for the enantiodifferentiating photoisomerization of (Z)-cyclooctene (1Z) [34][35][36][37] and (Z,Z)-1,3-cyclooctadiene (2ZZ) [38][39][40

• pH 10. Similar ee behavior was observed upon photoisomerization of 2ZZ sensitized by 5, showing a significant increase from 1.0% ee at pH 1.9–6.5 to 7.4% ee at pH 10. These results nicely coincide with the conformational changes of PM units caused by altering the solution pH, providing us with a

Control over molecular motion using the cis–trans photoisomerization of the azo group

• Estíbaliz Merino and
• María Ribagorda

Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119

• external stimuli. Keywords: azobenzenes; molecular switches; nanomachines; photoisomerization; Review This review is based on an article published in 2009 in Anales de Química (Real Sociedad Española de Química) [1]. Azobenzene was described for the first time in 1834 [2] and one century later, in 1937

• located in the visible region and is due to the presence of unshared electron pairs of nitrogen atoms [19]. Due to this second electronic transition, the dynamic photoisomerization process of azobenzenes is different to the carbonate compounds [20]. Azobenzene undergoes trans–cis isomerization by S1←S0

• states of a molecule with different absorption spectra. These photoisomerization processes modify the absorption spectra and can produce variations in different physicochemical properties of molecules, such as ion complexation, refractive index, electrochemical behaviour, and very significant

The effect of the formyl group position upon asymmetric isomeric diarylethenes bearing a naphthalene moiety

• Renjie Wang,
• Shouzhi Pu,
• Gang Liu and
• Shiqiang Cui

Beilstein J. Org. Chem. 2012, 8, 1018–1026, doi:10.3762/bjoc.8.114

• –3o were prepared by hydrolyzing compounds 7a–c in the presence of pyridine and p-toluenesulfonic acid in acetone/water. The structures of 1o–3o were confirmed by elemental analysis, NMR, and IR (Supporting Information File 1). Photoisomerization of diarylethenes 1–3 Diarylethenes 1−3 showed good

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

• light-induced click reaction of our PSCaa occurs predominantly in the cis state that is formed simultaneously due to the photoisomerization at λ = 365 nm. Recently, the concept of photoswitchable click amino acids has been applied to the polypeptide hormone urocortin, the helical fold of which was

• the study of this effect. Irradiation of the reaction mixture at λ = 365 nm for 45 min induces not only the thiol–ene click reaction but simultaneously the trans-to-cis photoisomerization. Under these conditions the formation of the intramolecular bridge resulted in click product 3 with i,i+4 helical

• click product 5 at high GSH concentrations and the intramolecular click product 3 at decreasing GSH concentrations. Photoisomerization of the photoswitchable click amino acid 2-amino-3-(4-((3-vinylphenyl)diazenyl)phenyl)propanoic acid. Thiol–ene click reaction of PSCaa with cysteine within the helical

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

Intraannular photoreactions in pseudo-geminally substituted [2.2]paracyclophanes

• Henning Hopf,
• Vitaly Raev and
• Peter G. Jones

Beilstein J. Org. Chem. 2011, 7, 658–667, doi:10.3762/bjoc.7.78

• Braunschweig, Germany, Fax: +49 531 / 391 5387 10.3762/bjoc.7.78 Abstract The photoisomerization of the pseudo-geminal tetraene 11 furnishes the cyclooctadiene derivatives 13 and 15 with a completely new type of molecular bridge for a [2.2]paracyclophane which promise many interesting novel applications; the

• same is true for the photoisomerization of 22 to 23 and 24. The structures of these new hydrocarbons were established by X-ray crystallography and spectroscopic analysis; among the noteworthy structural features of 13 and 15 are unusually long carbon–carbon single bonds (>1.64 Å). Keywords

• prepare the biscyclopropane analog of 11, the bisvinylcyclopropane 19 (or one of its cis-isomers) and subject this presumably strained hydrocarbon to our photocyclization conditions. Of course, this system also has various options to react, among them the photoisomerization to a mono- or all-cis

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

• ], photoisomerization of 2-arylisatogen [25], and cyclocondensation of anthranilic acid with orthoesters [26]. Meanwhile, the cyclodehydration of N-acylanthranilic acids in refluxing acetic anhydride has been the prevalent method used for production of 4H-3,1-benzoxazin-4-ones. However, use of traditional dehydrating