Synthesis and metal binding properties of N-alkylcarboxyspiropyrans

• Alexis Perry and
• Christina J. Kousseff

Beilstein J. Org. Chem. 2017, 13, 1542–1550, doi:10.3762/bjoc.13.154

• with the facile elaboration of the spiropyran core, have made spiropyran–merocyanine systems a common motif in molecular switch and sensing applications [2]. In this respect, the difference in optical properties between colourless, non-fluorescent spiropyran and coloured, fluorescent merocyanine has

Grip on complexity in chemical reaction networks

• Albert S. Y. Wong and
• Wilhelm T. S. Huck

Beilstein J. Org. Chem. 2017, 13, 1486–1497, doi:10.3762/bjoc.13.147

• amplified. Similarly, the design is used to create an analog-to-digital output by introducing a trypsin inhibitor (soybean trypsin inhbitor (STI)) in the second CSTR (Figure 6b). The STI effectively thresholds the local minima in the initial oscillations, converting the initial signal into a switch-like

• chemical reactions create functionality, and ultimately, how molecules create life. Network motifs. (a) Examples of network motifs composed from different feedback loops. Each design can turn a universal signaling cycle into a bistable switch and relaxation oscillator. Adapted with permission from [24

Detection of therapeutic radiation in three-dimensions

• John A. Adamovics

Beilstein J. Org. Chem. 2017, 13, 1325–1331, doi:10.3762/bjoc.13.129

• initial studies focused on a broad class of compounds referred to as leuco dyes which switch between two chemical forms of which one is colorless. The transformations are caused by the in put of energy either from heat, light or change in pH [16]. The leuco dyes by themselves are not oxidized at clinical

Biomimetic molecular design tools that learn, evolve, and adapt

• David A Winkler

Beilstein J. Org. Chem. 2017, 13, 1288–1302, doi:10.3762/bjoc.13.125

• the threshold. Random weight dropout involves randomly selecting weights or hidden layer nodes, setting them identically to zero for one or more training cycles. Both of these methods effectively ‘switch off’ relatively large parts of the deep neural network, this reducing the number of fitted

Total syntheses of the archazolids: an emerging class of novel anticancer drugs

• Stephan Scheeff and
• Dirk Menche

Beilstein J. Org. Chem. 2017, 13, 1085–1098, doi:10.3762/bjoc.13.108

• . Notably, they had to switch the halide/organometallic functionality of each building block after an unsuccessful coupling between the stannane synthesized by reduction and methylation of ketone 67 and the iodine derived from fragment 62. They assume that the steric hindrance of the methyl group in C10

Automating multistep flow synthesis: approach and challenges in integrating chemistry, machines and logic

• Chinmay A. Shukla and
• Amol A. Kulkarni

Beilstein J. Org. Chem. 2017, 13, 960–987, doi:10.3762/bjoc.13.97

• ‘telescopic’ synthesis when carried out in a continuous mode. A separation or purification step is required if (i) there is a need to isolate the necessary phase or isomer or (ii) to switch to a new solvent due to chemical compatibility or (iii) due to an unviable boiling point or (iv) for the cases where the

• intermediate can be reacted with H2 in a commercial reactor with an integrated control system. After hydrogenation, the solvent switch can be carried out in an evaporator by removing the THF solvent and then re-dissolving the intermediate in DCM as solvent. The outlet flow rate of the evaporator can be

Interactions between shape-persistent macromolecules as probed by AFM

• Johanna Blass,
• Jessica Brunke,
• Franziska Emmerich,
• Cédric Przybylski,
• Vasil M. Garamus,
• Artem Feoktystov,
• Roland Bennewitz,
• Gerhard Wenz and
• Marcel Albrecht

Beilstein J. Org. Chem. 2017, 13, 938–951, doi:10.3762/bjoc.13.95

• AFM tip and found enhancement factors up to 2, depending on the force loading rate [46]. We have previously explored the adhesion characteristics of dense CD layers on an AFM tip and a planar silicon surface connected by various ditopic linker molecules. In this system we were able to switch adhesion

Opportunities and challenges for the sustainable production of structurally complex diterpenoids in recombinant microbial systems

• Katarina Kemper,
• Max Hirte,
• Markus Reinbold,
• Monika Fuchs and
• Thomas Brück

Beilstein J. Org. Chem. 2017, 13, 845–854, doi:10.3762/bjoc.13.85

• naturally leads to the formation of tricyclic taxadiene [56] was achieved by exchanging a valin in position 584 with methionine. The resulting product was identified as a bicyclic diterpene of the verticillene type [51] (Scheme 2). A single residue switch in position 753 (W753H) presumably causes premature

How and why kinetics, thermodynamics, and chemistry induce the logic of biological evolution

• Addy Pross and
• Robert Pascal

Beilstein J. Org. Chem. 2017, 13, 665–674, doi:10.3762/bjoc.13.66

• /persistence, rather than on free energy, that offers a basis for understanding the evolutionary process. Furthermore, a threshold distance from equilibrium, leading to irreversibility in the reproduction cycle, is needed to switch the directive for evolution from thermodynamic to DKS. The present report

Polyketide stereocontrol: a study in chemical biology

• Kira J. Weissman

Beilstein J. Org. Chem. 2017, 13, 348–371, doi:10.3762/bjoc.13.39

• type behavior, and still others having no effect on the stereochemical outcome. Most importantly, introducing the same Caffrey motifs mutations into DEBS KRs 1 and 2 housed within DEBS 1-TE produced no discernable stereochemical switch in vivo [78]. These results clearly show that within the context of

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

• Pavel Nagorny and
• Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

• close chiral anion-pair complexes would then undergo a chiral counterion-controlled asymmetric reaction with a nucleophile. This proposal was validated experimentally, and a chloride-induced conformational switch to form a helical backbone was experimentally observed by circular dichroism (CD) during

Protonated paramagnetic redox forms of di-o-quinone bridged with p-phenylene-extended TTF: A EPR spectroscopy study

• Nikolay O. Chalkov,
• Vladimir K. Cherkasov,
• Gleb A. Abakumov,
• Andrey G. Starikov and
• Viacheslav A. Kuropatov

Beilstein J. Org. Chem. 2016, 12, 2450–2456, doi:10.3762/bjoc.12.238

• (A–D–A) systems as ligands [1]. A linear planar skeleton of the molecule with coordinating sites placed at the termini allows the construction of ordered structures using metal ions as nodes [2]. The insertion of p-phenylene in the TTF core is of special interest because it can act as a switch which

High performance p-type molecular electron donors for OPV applications via alkylthiophene catenation chromophore extension

• Paul B. Geraghty,
• Calvin Lee,
• Jegadesan Subbiah,
• Wallace W. H. Wong,
• James L. Banal,
• Mohammed A. Jameel,
• Trevor A. Smith and
• David J. Jones

Beilstein J. Org. Chem. 2016, 12, 2298–2314, doi:10.3762/bjoc.12.223

• semiconductors, there has been a rapid advance in the development of MMs with PCEs over 10% now reported [8][9]. The switch to MMs has in part been due to their discrete structure and relative ease of purification, which offers significant advantages, especially reduced batch-to-batch variation [10][11][12]. We

The hydrolysis of geminal ethers: a kinetic appraisal of orthoesters and ketals

• Sonia L. Repetto,
• James F. Costello,
• Craig P. Butts,
• Joseph K. W. Lam and
• Norman M. Ratcliffe

Beilstein J. Org. Chem. 2016, 12, 1467–1475, doi:10.3762/bjoc.12.143

• . Exclusion of O(1/3)─C(5/4) cleavage It has been noted that annular strain in trans-2,5-dimethyltetrahydrofurans invokes sufficient charge separation to switch the mechanism of ring cleavage from SN2 → SN1 [34]. We therefore sought to exclude the possibility of mechanistic partitioning via some strain

Cyclisation mechanisms in the biosynthesis of ribosomally synthesised and post-translationally modified peptides

• Andrew W. Truman

Beilstein J. Org. Chem. 2016, 12, 1250–1268, doi:10.3762/bjoc.12.120

• other bacteria [151]. Therefore, methanobactins assist with copper uptake for these bacteria and have been shown to participate in the control of the “copper-switch” that regulates whether copper-containing or copper-free MMO is expressed [152]. Thus far, methanobactins have been identified that contain

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

• photochemical properties, in particular their photochromicity, switching kinetics and reversibility, fatigue resistance, and thermostability, were investigated. The main text shows only the analytical data for new pyridyl switch 1b in comparison to the previously published and well-studied switch 2b [43]; all

• opening by vis irradiation only for pyridyl switch 1b, which had shown the highest photostability (Figure 2). These measurements revealed almost complete loss of photoswitchability over 7 cycles, whereas the compound 2b showed only slight deterioration (Figure 3). The more electron-rich two-methyl

• appear in the chromatograms of the two-methyl compounds after reaching the photostationary state (where the closed-ring isomer dominates with more than 95% in all cases according to the integrated peak areas, Figure 4), the 1-methyl switches behave differently: For naphthyl switch 1d the single peak

Cationic Pd(II)-catalyzed C–H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies

• Takashi Nishikata,
• Alexander R. Abela,
• Shenlin Huang and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2016, 12, 1040–1064, doi:10.3762/bjoc.12.99

• formed earlier in water (vide supra), but as seen previously in the corresponding Suzuki–Miyaura reactions, a switch to EtOAc obviated the need for a silver salt. In the presence of BQ and HBF4, the reaction of 1g and acrylate 4 was efficiently catalyzed by Pd(OAc)2 (Figure 5, runs 3 and 4). Lower

Opportunities and challenges for direct C–H functionalization of piperazines

• Zhishi Ye,
• Kristen E. Gettys and
• Mingji Dai

Beilstein J. Org. Chem. 2016, 12, 702–715, doi:10.3762/bjoc.12.70

• , a significant progress has been made. Due to the low reactivity of MeI and Me2SO4, a diamine switch strategy of replacing the bulky chiral diamines (21/28) with the less hindered TMEDA has been put in place to improve the reactivity of the alkyllithium intermediate and gave a 48% yield of (S)-46

• the diamine switch strategy and α-methylbenzyl chiral auxiliary strategy has been reported to give the best results and produce 51 in 70% yield and 90:10 diastereoselectivity (Figure 11, reaction 3). O’Brien and co-workers also reported a stereoselective synthesis of enantiopure 2,6-trans- and 2,5

Antibiotics from predatory bacteria

• Juliane Korp,
• María S. Vela Gurovic and
• Markus Nett

Beilstein J. Org. Chem. 2016, 12, 594–607, doi:10.3762/bjoc.12.58

• their feeding behavior, that is, whether or not their diet relies exclusively on prey consumption, these bacteria have been classified as obligate or facultative predators [6]. While obligate predators can only survive by consuming other bacteria, facultative predators readily switch to a saprophytic

• prokaryotic RNA polymerase (RNAP) as mode of action for myxopyronins and corallopyronins [95][97]. Later on, mutagenesis experiments as well as binding studies indicated that the antibiotics interact with the RNAP switch region [104][105], which acts as a hinge mediating conformational changes during

• active-center cleft. After binding to the switch region, myxopyronins and corallopyronins prevent the opening of the clamp [104][105]. Prey bacteria that develop resistance against corallopyronin, e.g., due to a rpoB mutation, also become resistant towards predation by C. coralloides [82]. It is thus

New synthetic strategies for xanthene-dye-appended cyclodextrins

• Milo Malanga,
• Andras Darcsi,
• Mihaly Balint,
• Gabor Benkovics,
• Tamas Sohajda and
• Szabolcs Beni

Beilstein J. Org. Chem. 2016, 12, 537–548, doi:10.3762/bjoc.12.53

• University, Hlavova 8, 12843 Prague 2, Czech Republic 10.3762/bjoc.12.53 Abstract Xanthene dyes can be appended to cyclodextrins via an ester or amide bridge in order to switch the fluorescence on or off. This is made possible through the formation of nonfluorescent lactones or lactams as the fluorophore

• acts as a complementary molecular switch to Rho-β-CD. While Rho-β-CD exhibits fluorescence at acidic pH, Flu-β-CD shows fluorescence at both neutral and alkaline pH. NMR characterization of Flu-β-CD The 1H NMR spectrum shown in Figure 7 is a typical spectrum of an asymmetric cyclodextrin. The sharp and

Enabling technologies and green processes in cyclodextrin chemistry

• Giancarlo Cravotto,
• Marina Caporaso,
• Laszlo Jicsinszky and
• Katia Martina

Beilstein J. Org. Chem. 2016, 12, 278–294, doi:10.3762/bjoc.12.30

• entrance via confocal laser scanning microscopy [30]. Several types of dye moiety/CD derivatives have been suggested as "switch on" or "switch off" fluorescent chemical sensors. In these systems, the complexation with a guest molecule allows to enhance or decrease the fluorescence intensity. Two water

Supramolecular polymer assembly in aqueous solution arising from cyclodextrin host–guest complexation

• Jie Wang,
• Zhiqiang Qiu,
• Yiming Wang,
• Li Li,
• Xuhong Guo,
• Duc-Truc Pham,
• Stephen F. Lincoln and
• Robert K. Prud’homme

Beilstein J. Org. Chem. 2016, 12, 50–72, doi:10.3762/bjoc.12.7

• -CD·FCA has a much lower K ≤ 20 M−1. Thus, the oxidation state of iron determines the relative stabilities of β-CD·FCA− and β-CD·FCA. Conjointly, these complexes may potentially be used as an electrochemical switch in a supramolecular system. In 2006, Harada et al. realized this potential in a redox

Solving the puzzling competition of the thermal C²–C⁶ vs Myers–Saito cyclization of enyne-carbodiimides

• Anup Rana,
• Mehmet Emin Cinar,
• Debabrata Samanta and
• Michael Schmittel

Beilstein J. Org. Chem. 2016, 12, 43–49, doi:10.3762/bjoc.12.6

• time, diradical intermediates were invoked for both pathways based on analogy and computational results [18]. To obtain a deeper understanding of this switch in selectivity, we decided to amalgamate computations and new mechanistic experiments to resolve the puzzle. For the computational part of this

Bright molecules for sensing, computing and imaging: a tale of two once-troubled cities

• A. Prasanna de Silva

Beilstein J. Org. Chem. 2015, 11, 2774–2784, doi:10.3762/bjoc.11.298

• amine [3][24][30], an amino acid [18][31], a crown ether [32] or a cryptand [33] and the spacer could be an oligomethylene chain [34] or nothing at all [35][36]. Since such diverse systems allow the addressing of various problems and since the design is usually straightforward, the PET sensor/switch

Synthesis of cyclic N¹-pentylinosine phosphate, a new structurally reduced cADPR analogue with calcium-mobilizing activity on PC12 cells

• Ahmed Mahal,
• Stefano D’Errico,
• Nicola Borbone,
• Brunella Pinto,
• Agnese Secondo,
• Valeria Costantino,
• Valentina Tedeschi,
• Giorgia Oliviero,
• Vincenzo Piccialli and
• Gennaro Piccialli

Beilstein J. Org. Chem. 2015, 11, 2689–2695, doi:10.3762/bjoc.11.289

• -phosphate adduct formed with the activating agent. For this reason, we decided to switch to the synthetic pathway B (Figure 2), in which the monophosphate group is installed at the 5’-ribose position. This strategy, reported in Scheme 2, used as the starting material the 5’-TBDMS-2’,3’-O