A toolbox of molecular photoswitches to modulate the CXCR3 chemokine receptor with light

• Xavier Gómez-Santacana,
• Sabrina M. de Munnik,
• Tamara A. M. Mocking,
• Niels J. Hauwert,
• Shanliang Sun,
• Prashanna Vijayachandran,
• Iwan J. P. de Esch,
• Henry F. Vischer,
• Maikel Wijtmans and
• Rob Leurs

Beilstein J. Org. Chem. 2019, 15, 2509–2523, doi:10.3762/bjoc.15.244

• the para-position of the central ring. A variety of efficacy differences between the trans and cis forms emerges from these compounds. Tool compounds VUF15888 (4d) and VUF16620 (6e) represent more subtle efficacy switches, while VUF16216 (6f) displays the largest efficacy switch, from antagonism to

• , exemplified by partial agonist 1c and equal full agonists 1d and 1e (VUF11418, Figure 2A). A tentative explanation for this efficacy switch includes a variation of the dihedral angle of the biaryl moiety, an increase of the electron density in the biaryl unit and/or a postulated halogen bond of the halogen

Experimental and computational electrochemistry of quinazolinespirohexadienone molecular switches – differential electrochromic vs photochromic behavior

• Eric W. Webb,
• Jonathan P. Moerdyk,
• Kyndra B. Sluiter,
• Benjamin J. Pollock,
• Amy L. Speelman,
• Eugene J. Lynch,
• William F. Polik and
• Jason G. Gillmore

Beilstein J. Org. Chem. 2019, 15, 2473–2485, doi:10.3762/bjoc.15.240

• anion rather than a photoexcited state. The reduction of the molecular switch necessary for electrochromism is in a sense catalytic: the rearranged product is reoxidized to a neutral LW isomer, which reverts thermally to SW upon standing, just as it does when the LW is generated photochemically. The

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

• absorption cross-section of the molecule. Keywords: hydrazone; molecular switch; pump-probe spectroscopy; time-resolved fluorescence; Introduction Molecular switches are systems that are able to rapidly respond to an external stimulus, which can be of chemical or physical nature, through a variation of

Effect of ring size on photoisomerization properties of stiff stilbene macrocycles

• Sandra Olsson,
• Óscar Benito Pérez,
• Magnus Blom and
• Adolf Gogoll

Beilstein J. Org. Chem. 2019, 15, 2408–2418, doi:10.3762/bjoc.15.233

• the resulting macrocycle. Keywords: DFT; molecular mechanics; photostability; photo-switch; ring-strain; stiff stilbene; Introduction The stiff stilbene (SS) molecule has drawn a lot of interest due to its photodynamic properties [1]. Stiff stilbenes typically undergo light triggered isomerization

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

• photochromism in the spiropyran switch [18]. Other recent studies of photochromic systems within macrocyclic and supramolecular hosts [19] include dihydroazulene switches [20] and red-shifted azobenzenes [21][22] inside cucurbiturils and cyclodextrins. The behavior of light-responsive compounds can also be

Aggregation-induced emission effect on turn-off fluorescent switching of a photochromic diarylethene

• Luna Kono,
• Yuma Nakagawa,
• Ayako Fujimoto,
• Ryo Nishimura,
• Yohei Hattori,
• Toshiki Mutai,
• Nobuhiro Yasuda,
• Kenichi Koizumi,
• Satoshi Yokojima,
• Shinichiro Nakamura and
• Kingo Uchida

Beilstein J. Org. Chem. 2019, 15, 2204–2212, doi:10.3762/bjoc.15.217

• turn-off type fluorescent switch (Figure 6c and Figure 7e) [29][30]. The emission from the aggregates quenched much faster than the solution (Figure 6c) (Supporting Information File 2, Movie 1). This is due to a “giant amplification of fluorescence photoswitching” ascribed by a very efficient

Norbornadiene-functionalized triazatriangulenium and trioxatriangulenium platforms

• Roland Löw,
• Talina Rusch,
• Tobias Moje,
• Fynn Röhricht,
• Olaf M. Magnussen and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1815–1821, doi:10.3762/bjoc.15.175

• are possible to account for the presence of these two species: Either they correspond to a mixture of adsorbed NBD-TATA 1a and QC-TATAs 1b or to coadsorption of 1a and the pure octyl-TATA 6. The first case may be possible, because the molecules are able to switch to the 1b state at a wavelength of 385

Design, synthesis and biological evaluation of immunostimulating mannosylated desmuramyl peptides

• Rosana Ribić,
• Ranko Stojković,
• Lidija Milković,
• Mariastefania Antica,
• Marko Cigler and
• Srđanka Tomić

Beilstein J. Org. Chem. 2019, 15, 1805–1814, doi:10.3762/bjoc.15.174

• affect the Th1/Th2 switch of the immune response [52]. The presented results demonstrate the great immunostimulating potential of glycolyl-modified desmuramyl peptides. Peptidoglycan fragments with mycobacterial structural features, such as synthesized compounds 20–22, could efficiently link innate and

An azobenzene container showing a definite folding – synthesis and structural investigation

• Abdulselam Adam,
• Saber Mehrparvar and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2019, 15, 1534–1544, doi:10.3762/bjoc.15.156

• the high dispersion energy in the compact cis,cis-isomer. Keywords: azobenzene; macrocycles; molecular switch; Introduction In supramolecular chemistry rigid scaffolds are required to arrange different recognition units in predefined distances and spatial orientation to each other [1]. One example

• coefficient of the compound. To examine this, DOSY spectra of the container 10 after synthesis and after irradiation with light of the wavelength λ = 365 nm were recorded (Figure 8). Please note, that a change in the geometry of a switch need not result in a change of the size of the diffusion coefficient

Diazocine-functionalized TATA platforms

• Roland Löw,
• Talina Rusch,
• Fynn Röhricht,
• Olaf Magnussen and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1485–1490, doi:10.3762/bjoc.15.150

• gold. To investigate this mechanism further and to examine scope and limitation of the “spin-switch catalysis” we now prepared analogous diazocine systems. Diazocines, in contrast to azobenzenes, are stable in the cis-configuration. Upon irradiation with light of 405 nm the cis-configuration isomerizes

• ordered monolayers on Au(111) surfaces. Keywords: cis–trans isomerization; diazocine; molecular switch; photochrome; self-assembled monolayers; TATA platform; Introduction Catalysts increase chemical reaction rates by lowering the activation energies and thus create more favorable reaction pathways [1

Complexation of a guanidinium-modified calixarene with diverse dyes and investigation of the corresponding photophysical response

• Yu-Ying Wang,
• Yong Kong,
• Zhe Zheng,
• Wen-Chao Geng,
• Zi-Yi Zhao,
• Hongwei Sun and
• Dong-Sheng Guo

Beilstein J. Org. Chem. 2019, 15, 1394–1406, doi:10.3762/bjoc.15.139

• accompanied by a drastic quenching of fluorescence, which is a proper feature to be applied in IDA, product-selective STA and BDA, resulting in a desired switch-on sensing (Scheme 1) or activatable phototheranostics. With respect to the sensing application, the reporter pairs can be used in very dilute

• naphthalenesulfonic acids generally shows large binding affinities and a prominent fluorescence enhancement. Differing from the complexation-induced quenching of ACQ dyes, the fluorescence enhancement of ICT dyes upon complexation with GC5A would benefit for substrate-selective STA, realizing the desired switch-on

• typical difference from ICT dyes [56]. The extraordinary fluorescence enhancement of P-TPE upon complexation with GC5A (Ibound/Ifree = 42) would be beneficial for substrate-selective STA, realizing the desired switch-on sensing (Scheme 1). The complexation between calixarenes and AIEgens also offers the

Coordination chemistry and photoswitching of dinuclear macrocyclic cadmium-, nickel-, and zinc complexes containing azobenzene carboxylato co-ligands

• Jennifer Klose,
• Tobias Severin,
• Peter Hahn,
• Alexander Jeremies,
• Jens Bergmann,
• Daniel Fuhrmann,
• Jan Griebel,
• Bernd Abel and
• Berthold Kersting

Beilstein J. Org. Chem. 2019, 15, 840–851, doi:10.3762/bjoc.15.81

• [Cd2L]2+ fragment. The switch from the trans to the cis form induces significant change of the π–π transitions of the supporting N6S2 macrocycle, which may be indicative of some increased π–π- (or charge transfer) interactions between the aromatic rings of the electron rich amino thiophenolato

The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives

• Tilman Lechel,
• Roopender Kumar,
• Mrinal K. Bera,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2019, 15, 655–678, doi:10.3762/bjoc.15.61

• prototropy directly delivers the isolated 1,2-diketones DK. Experiments with labelled oxygen showed that the oxazole oxygen originates from the alkoxy group and not from the amide moiety [45]. The oxazole formation therefore requires a configurational switch from enol E-EN to Z-EN. Very likely, this step is

Aqueous olefin metathesis: recent developments and applications

• Valerio Sabatino and
• Thomas R. Ward

Beilstein J. Org. Chem. 2019, 15, 445–468, doi:10.3762/bjoc.15.39

• the benzylidene moiety, such as NO2 [58], they proposed an “electron-donating to electron-withdrawing activity switch”, consisting of an in situ formation of quaternary ammonium salts by treatment with Brønsted acids (Scheme 10). Several metathesis reactions were performed in methanol/water mixtures

Synthesis of a tubugi-1-toxin conjugate by a modulizable disulfide linker system with a neuropeptide Y analogue showing selectivity for hY1R-overexpressing tumor cells

• Rainer Kufka,
• Robert Rennert,
• Goran N. Kaluđerović,
• Lutz Weber,
• Wolfgang Richter and
• Ludger A. Wessjohann

Beilstein J. Org. Chem. 2019, 15, 96–105, doi:10.3762/bjoc.15.11

• breast tissue was found to express negligible amounts of hY1R but predominantly the closely related Y2 receptor subtype (hY2R) [23]. Hence, a switch from hY2R to hY1R expression during pathogenic breast-cell transformation was hypothesized. Furthermore, many breast cancers of all major breast cancer

Regioselective addition of Grignard reagents to N-acylpyrazinium salts: synthesis of substituted 1,2-dihydropyrazines and Δ⁵-2-oxopiperazines

• Valentine R. St. Hilaire,
• William E. Hopkins,
• Yenteeo S. Miller,
• Srinivasa R. Dandepally and
• Alfred L. Williams

Beilstein J. Org. Chem. 2019, 15, 72–78, doi:10.3762/bjoc.15.8

• isolated in a yield of 40% (entry 1, Table 1). This initial low yield prompted us to switch the Grignard solvent from THF to DCM. Using modified reaction conditions from Andersson and co-wokers [22], phenylmagnesium bromide in DCM was added to 2 at −41 °C and after 35 min, dihydropyrazine 3a was only

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

• receptor. Hence, it should be possible to administer the stabile inactive compound and switch it on at the site of illness with visible light. To date only a limited number of diazocine derivatives have been published of which most are symmetrically functionalized. Using the Baeyer–Mills reaction for the

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• by UV light irradiation in the presence of oxygen, whereas dichlorostilbenes (E and Z forms) were formed under nitrogen atmosphere from benzotrichloride [100]. It was noticeable that an oxygen switch in dechlorination was successfully demonstrated. A benzoyl chloride was identified as an intermediate

Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

• Hendrik V. Schröder and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190

• introduction to readers new to the field of TTF-switchable MIMs. Review 1. Tetrathiafulvalene – an (almost) perfect molecular switch Whereas inorganic chemists are used to commonly handle metal-based compounds in different oxidation states, only a small selection of organic molecules [22] can be reversibly

• molecular switch. A first one-electron oxidation [23] converts neutral TTF (1) into the radical-cationic species 1●+ (Figure 1). The TTF radical cation is one of the rare organic radicals that are long-term stable and even isolable. A second oxidation step yields the dication 12+. Both redox-transitions are

• macroscopic as well as on the molecular level, even the most efficient switch is useless, if no observable output is generated which helps to detect the switching process [30]. A simple “read out” is provided by the optical properties of TTF in its different switching states. For example, UV–vis spectra of

Assessing the possibilities of designing a unified multistep continuous flow synthesis platform

• Mrityunjay K. Sharma,
• Roopashri B. Acharya,
• Chinmay A. Shukla and
• Amol A. Kulkarni

Beilstein J. Org. Chem. 2018, 14, 1917–1936, doi:10.3762/bjoc.14.166

• the throughput in the start or anywhere else gets changed in the sequence. This is very important for synthesis steps where downstream processing is also in sequence. Usually time scales for work-up procedures like extraction, crystallization, solvent switch etc. are longer compared to the main

• collect useful data for further plant design or for using it for a specific period of time to meet the production needs and then switch to another molecule, making it a flexible production platform. Eventually, at the pilot or production scale, it will be analogous to approach 2. Key features of this

A pyridinium/anilinium [2]catenane that operates as an acid–base driven optical switch

• Sarah J. Vella and
• Stephen J. Loeb

Beilstein J. Org. Chem. 2018, 14, 1908–1916, doi:10.3762/bjoc.14.165

• molecule; molecular switch; Introduction [2]Rotaxane molecular shuttles [1][2][3][4][5] are the dynamic building blocks of a wide variety of molecular switches [6][7][8][9] and a number of sophisticated molecular machines that operate away from equilibrium [10][11][12][13][14][15]. We have previously

• (pyridinium)ethane recognition sites linked by terphenyl spacer groups [17] (Figure 2). It was thus of interest to design and build these two different recognition sites (benzylanilinium and bis(pyridinium)ethane) into an analogous circumrotational [2]catenane molecular switch to compare to the linear [2

• in some cases exclusively (CD2Cl2) generating a true ON/OFF bistable switch; unfortunately, the [2]catenane switch is insoluble in CD2Cl2 when protonated so a comparison could not be undertaken in this solvent. This difference in site populations between [2]rotaxane and [2]catenane is due to the

Strong binding and fluorescence sensing of bisphosphonates by guanidinium-modified calix[5]arene

• Jie Gao,
• Zhe Zheng,
• Lin Shi,
• Si-Qi Wu,
• Hongwei Sun and
• Dong-Sheng Guo

Beilstein J. Org. Chem. 2018, 14, 1840–1845, doi:10.3762/bjoc.14.157

• , Tianjin 300071, China 10.3762/bjoc.14.157 Abstract Based on the indicator displacement assay (IDA) approach, we herein report the fluorescence “switch-on” sensing and quantitative detection of bisphosphonates (BPs), a class of drugs extensively used in the treatment of patients with various skeletal

• recovery, offers the opportunity for fluorescence “switch-on” sensing of BPs. In general, fluorescent IDA could be operated at low μM or even nM concentrations, which is desirable with respect to sensing sensitivity. We tested the host–guest complexation of GC5A with a total number of 9 BP drugs clinically

• pair, we realized the fluorescence “switch-on” sensing of BPs. We herein selected clodronate, zoledronate and etidronate to further investigate their quantitative detection. As shown in Figure 2a, increasing the concentrations of BPs resulted in a practically linear fluorescence increase. The limit of

Synthesis and photophysical studies of a multivalent photoreactive Ru^II-calix[4]arene complex bearing RGD-containing cyclopentapeptides

• Sofia Kajouj,
• Lionel Marcelis,
• Alice Mattiuzzi,
• Adrien Grassin,
• Damien Dufour,
• Pierre Van Antwerpen,
• Didier Boturyn,
• Eric Defrancq,
• Mathieu Surin,
• Julien De Winter,
• Pascal Gerbaux,
• Ivan Jabin and
• Cécile Moucheron

Beilstein J. Org. Chem. 2018, 14, 1758–1768, doi:10.3762/bjoc.14.150

• . Barton et al. demonstrated in 1990 that [Ru(bpy)2(dppz)]2+ behaves as a light-switch for DNA [5]: this complex is not luminescent in water but upon intercalation within the DNA base pairs stack, the complex luminescence is restored. Derivatives of [Ru(bpy)2(dppz)]2+ and complexes bearing similar aromatic

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

• applications in recent years. This molecular switch has been utilized inter alia in the rising field of photopharmacology [2][3], the manipulation of biomolecular processes [4][5][6] as well as in molecular machinery [7][8] and materials science [9][10][11]. Azobenzenes are highly stable, easily synthesized

Synthetic avenues towards a tetrasaccharide related to Streptococcus pneumonia of serotype 6A

• Aritra Chaudhury,
• Mana Mohan Mukherjee and
• Rina Ghosh

Beilstein J. Org. Chem. 2018, 14, 1095–1102, doi:10.3762/bjoc.14.95

• 2,3,4,6-tetra-O-benzyl-1-thio-β-D-galactopyranoside (22) with acceptor 4 using a NIS/TMSOTf combination in the presence of DMF acting as a modulating solvent (inset, Scheme 5). Unfortunately, when this strategy was applied to our case it could not produce a viable result. So we switch to the conventional