In search of visible-light photoresponsive peptide nucleic acids (PNAs) for reversible control of DNA hybridization

• Lei Zhang,
• Greta Linden and
• Olalla Vázquez

Beilstein J. Org. Chem. 2019, 15, 2500–2508, doi:10.3762/bjoc.15.243

• photoswitchable antisense research in the context of photopharmacology is entirely unexplored. Furthermore, reversible approaches with photoswitches will contribute to a better understanding of biological pathways as they would allow precise reversible spatio-temporal activation/deactivation of the desired

• avenues for the investigation of other photoswitchable PNAs and pursuing visible-light modulation. Herein, we report the design of a versatile synthetic platform to derivatize PNAs with different photoswitches (Figure 1), which has never been studied in the context of PNA. After incorporation, their

• )aminoethyl]glycine residue –Aeg(Alloc)– was selectively deprotected in the presence of Pd(OAc)2, Ph3P, NMM, PhSiH3 in CH2Cl2 for 2 h. Subsequently, carboxy photoswitches were introduced using Oxyma and N,N’-diisopropylcarbodiimide (DIC) as coupling agent. We explored two different types of photoswitches

Ultrafast processes triggered by one- and two-photon excitation of a photochromic and luminescent hydrazone

• Alessandro Iagatti,
• Baihao Shao,
• Alberto Credi,
• Barbara Ventura,
• Ivan Aprahamian and
• Mariangela Di Donato

Beilstein J. Org. Chem. 2019, 15, 2438–2446, doi:10.3762/bjoc.15.236

• photoswitches have been developed and successfully employed in many technological fields [20][21][22][23]. Among others, azobenzenes [24], spiropyranes [25], diarylethenes [26] and their derivatives have been intensively applied. Despite the numerous successful applications of several synthetized switches, some

• an absorption band in the region where the E-isomer absorbs is indicative of the photoinduced Z/E isomerization event, which thus results to be an ultrafast process, as observed for other photoswitches – azobenzene in particular [32]. Upon this initial ultrafast evolution, the transient absorption

• through two-photon fluorescence measurements [29]. Conclusion Hydrazones are a promising new class of molecular photoswitches. In this work we investigated the spectroscopic properties of hydrazone 1, a member of this family showing very interesting properties, such as high-isomerization quantum yield

Reversible switching of arylazopyrazole within a metal–organic cage

• Anton I. Hanopolskyi,
• Soumen De,
• Michał J. Białek,
• Yael Diskin-Posner,
• Liat Avram,
• Moran Feller and
• Rafal Klajn

Beilstein J. Org. Chem. 2019, 15, 2398–2407, doi:10.3762/bjoc.15.232

• Arylazopyrazoles represent a new family of molecular photoswitches characterized by a near-quantitative conversion between two states and long thermal half-lives of the metastable state. Here, we investigated the behavior of a model arylazopyrazole in the presence of a self-assembled cage based on Pd–imidazole

Excited state dynamics for visible-light sensitization of a photochromic benzil-subsituted phenoxyl-imidazolyl radical complex

• Yoichi Kobayashi,
• Yukie Mamiya,
• Katsuya Mutoh,
• Hikaru Sotome,
• Masafumi Koga,
• Hiroshi Miyasaka and
• Jiro Abe

Beilstein J. Org. Chem. 2019, 15, 2369–2379, doi:10.3762/bjoc.15.229

• Abstract Visible-light sensitized photoswitches have been paid particular attention in the fields of life sciences and materials science because long-wavelength light reduces photodegradation, transmits deep inside of matters, and achieves the selective excitation in condensed systems. Among various

• molecular design [25]. The wide ranges of thermal back reactions of photoswitches expand the potential applications of photochromic materials such as to dynamic holographic display [26][27][28], switchable fluorescent markers [29][30][31], and anticounterfeit inks. However, PIC is photosensitive only in the

• sensitization of PIC expands the versatility of the rate-tunable photoswitches of PIC systems. In this study, we synthesized a novel PIC derivative conjugated with a visible-light photosensitizer (Benzil-PIC, Scheme 1) and investigated the excited state dynamics. We used a benzil framework as a photosensitizer

Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

• A. Lennart Schleper,
• Mariano L. Bossi,
• Vladimir N. Belov and
• Stefan W. Hell

Beilstein J. Org. Chem. 2019, 15, 2344–2354, doi:10.3762/bjoc.15.227

• , substitution of fluorine and/or the addition of nucleophiles to the electron-poor double bond take place. Therefore, tert-butyl protection is required for carboxylates present in diarylethenes with “oxidized” benzothiophene units and perfluorocyclopentene rings. Photoswitches containing the free carboxylic

Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors

• Christoph W. Grathwol,
• Nathalie Wössner,
• Sören Swyter,
• Adam C. Smith,
• Enrico Tapavicza,
• Robert K. Hofstetter,
• Anja Bodtke,
• Manfred Jung and
• Andreas Link

Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214

• the biological activity of small molecules in vitro or in vivo comprises numerous opportunities for example in the elucidation of biochemical pathways or the reduction of systemic side effects in drug therapy. Molecular photoswitches, i.e., compounds that undergo changes in their geometry and

• physicochemical properties upon irradiation with light, represent one major approach to this. One of the most common light-driven transformations exploited in molecular photoswitches is the E–Z isomerization of double bonds [18]. In this context, the photochemistry of stilbenes and the closely related azobenzenes

• azobenzenes are more convenient as already proven by their use as photoswitches in countless biological applications [26][27][28][29][30]. However, their heteroaromatic counterparts still seem underrepresented [31]. The approach to new chemotypes for sirtuin inhibition via known adenosine mimicking kinase

Fluorinated azobenzenes as supramolecular halogen-bonding building blocks

• Esther Nieland,
• Oliver Weingart and
• Bernd M. Schmidt

Beilstein J. Org. Chem. 2019, 15, 2013–2019, doi:10.3762/bjoc.15.197

• , Universitätsstraße 1, D-40225 Düsseldorf, Germany 10.3762/bjoc.15.197 Abstract ortho-Fluoroazobenzenes are a remarkable example of bistable photoswitches, addressable by visible light. Symmetrical, highly fluorinated azobenzenes bearing an iodine substituent in para-position were shown to be suitable supramolecular

• building blocks both in solution and in the solid state in combination with neutral halogen bonding acceptors, such as lutidines. Therefore, we investigate the photochemistry of a series of azobenzene photoswitches. Upon introduction of iodoethynyl groups, the halogen bonding donor properties are

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• -crown-5 ether; benzothiazolium crown ether-containing styryl dyes; E/Z photoisomerization; molecular solar thermal system; Introduction Molecular photoswitches permanently attract considerable interest because they hold potential for application in molecular electronic and photonic devices [1][2][3][4

• ][5]. Photoswitches are a class of switches that can alternate between the thermodynamically stable forms by application of light (or change of the light intensity) as an external stimulus. If the stable forms (isomers) are not isoenergetic, they have the ability to capture and store imported (solar

Synthesis of functionalized diazocines for application as building blocks in photo- and mechanoresponsive materials

• Widukind Moormann,
• Daniel Langbehn and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 727–732, doi:10.3762/bjoc.15.68

• damage by UV light [19]. Well separated absorption bands, high switching efficiency and high quantum yields are further advantages regarding their application as switches in photoresponsive materials [19][24][26]. In contrast to spiropyrans which have been frequently used as photoswitches in materials

Oxidative and reductive cyclization in stiff dithienylethenes

• Michael Kleinwächter,
• Ellen Teichmann,
• Lutz Grubert,
• Martin Herder and
• Stefan Hecht

Beilstein J. Org. Chem. 2018, 14, 2812–2821, doi:10.3762/bjoc.14.259

• Diarylethenes (DAEs) are a rich family of organic photoswitches formally derived from stilbene [1][2]. Upon irradiation they are able to undergo reversible photoisomerization based on 6π-electrocyclization and -cycloreversion, respectively, between two thermally stable states, which make them interesting

• family of photoswitches possessing three switching states (E/Z/C). The oxidation potentials of a series of compounds with either 5-, 6-, or 7-membered rings attached to the central exocyclic double bond as well as the electronic influence of substituents were compared. We found that in particular the

Synthesis of mono-functionalized S-diazocines via intramolecular Baeyer–Mills reactions

• Miriam Schehr,
• Daniel Hugenbusch,
• Tobias Moje,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2018, 14, 2799–2804, doi:10.3762/bjoc.14.257

• difficult to achieve. On this account, bridged azobenzenes (diazocines), would be more suitable as photoswitches in pharmacologically active compounds [8]. Besides their superior photophysical properties, diazocines are more stable in the cis configuration and could therefore be administered in their

London dispersion as important factor for the stabilization of (Z)-azobenzenes in the presence of hydrogen bonding

• Andreas H. Heindl,
• Raffael C. Wende and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2018, 14, 1238–1243, doi:10.3762/bjoc.14.106

• density functional theory (DFT) computations, attractive LD forces were identified as the origin of this stability trend. Based on this study, LD interactions represent a valuable tool for the design of novel azobenzene photoswitches [24]. Herein we provide further evidence for the importance of LD as

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• ball milling using a custom-made copper vial and copper ball enabled efficient reaction between propyne-derivatised photoswitches and an azidodeoxynucleoside click partner (Scheme 6) [44]. In contrast to the solution-phase (Cu(I)-promoted) reactions, no contamination of the ball milled products by

The role of alkyl substituents in deazaadenine-based diarylethene photoswitches

• Christopher Sarter,
• Michael Heimes and
• Andres Jäschke

Beilstein J. Org. Chem. 2016, 12, 1103–1110, doi:10.3762/bjoc.12.106

• Christopher Sarter Michael Heimes Andres Jaschke Institut für Pharmazie und Molekulare Biotechnologie, Universität Heidelberg, 69120 Heidelberg, Germany 10.3762/bjoc.12.106 Abstract Diarylethenes are an important class of reversible photoswitches and often claimed to require two alkyl

• substituents at the carbon atoms between which the bond is formed or broken in the electrocyclic rearrangement. Here we probe this claim by the synthesis and characterization of four pairs of deazaadenine-based diarylethene photoswitches with either one or two methyl groups at these positions. Depending on the

• DNA photoswitches for the application in bionanotechnology and synthetic biology. Keywords: diarylethene; nucleoside; electrocyclic rearrangement; photochromism; photoswitch; Introduction Most biomacromolecules are per se not responsive to light. Their conversion into photoresponsive molecules opens

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

• oligomer shape and concomitantly in the sugar ligands accessibility. Indeed, dramatic shrinking of rigid-rod polymers for example, occurs upon photoirradiation when several azobenzenes are introduced in the main-chain, the embedded photoswitches acting as hinges [17][18]. In the present study, an

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

• residues were intramolecularly cross-linked with thiol reactive azobenzene-based photoswitches. Photoisomerization of the azobenzene changes the conformation of the peptide depending on the location of the cysteine. When the azo group of polypeptide 2 is in its trans form, it retains its affinity for DNA

• between the trans and cis isomer but in turn destabilizes one of the helices of the cis isomer, and only one cis isomer (P) is present in solution (Figure 22). Conclusion Azobenzene is one of the most used systems in the design of molecular photoswitches. The synthesis is very easy and their photochromic

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

• [1][2][3][4]. Nucleic acids are synthesized by building blocks; in this bottom-up approach artificial functionalities, such as photoswitches, can be introduced synthetically by providing the corresponding artificial DNA building block. Among the known and structurally diverse photochromic compounds

Building photoswitchable 3,4'-AMPB peptides: Probing chemical ligation methods with reducible azobenzene thioesters

• Gehad Zeyat and
• Karola Rück-Braun

Beilstein J. Org. Chem. 2012, 8, 890–896, doi:10.3762/bjoc.8.101

• of photoswitches, and typical applications based on light-triggered reversible conformational control of cyclic, helical or beta-hairpin peptides have been intensively reviewed [2][3]. Current research in this field focuses on advanced methods and designs for the synthesis of complex azopeptides and

Molecular switches and cages

• Dirk Trauner

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

• synthetic switches, complementing the many types found in nature. Given their prominence in biology, it is not surprisingly that photoswitches, which are actuated by ultraviolet, visible or infrared light, have been an especially productive field of study. Despite their long history, new types of synthetic

• photoswitches continue to emerge and “old friends”, such as azobenzenes are constantly improved and optimized. This is not only true with respect to their photophysical properties but also with regard to their synthetic accessibility. Indeed, as molecular switches are applied in ever-increasing quantities, the

• compounds but in its infancy in the case of reversible photoswitches. The present Thematic Series of the Beilstein Journal of Organic Chemistry addresses the crucial role that chemistry, and particularly organic chemistry, can play in tuning the functional features of molecular switches and cages. These

Synthesis of novel photochromic pyrans via palladium- mediated reactions

• Christoph Böttcher,
• Gehad Zeyat,
• Saleh A. Ahmed,
• Elisabeth Irran,
• Thorben Cordes,
• Cord Elsner,
• Wolfgang Zinth and
• Karola Rueck-Braun

Beilstein J. Org. Chem. 2009, 5, No. 25, doi:10.3762/bjoc.5.25

• -electronic devices, e.g. as logic gates [1]. In the life sciences, functionalized azobenzenes [6], hemithioindigos [7][8] and fulgimides [9][10] among other classes of photoswitches, have already proven to be valuable tools for photo-controlling the structure and function of complex biomolecules [6][7][8][9