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Nature Chemistry

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https://www.readbyqxmd.com/read/29168498/enantioselective-cyclizations-and-cyclization-cascades-of-samarium-ketyl-radicals
#1
Nicolas Kern, Mateusz P Plesniak, Joseph J W McDouall, David J Procter
The rapid generation of molecular complexity from simple starting materials is a key challenge in synthesis. Enantioselective radical cyclization cascades have the potential to deliver complex, densely packed, polycyclic architectures, with control of three-dimensional shape, in one step. Unfortunately, carrying out reactions with radicals in an enantiocontrolled fashion remains challenging due to their high reactivity. This is particularly the case for reactions of radicals generated using the classical reagent, SmI2...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168496/de-novo-design-of-a-hyperstable-non-natural-protein-ligand-complex-with-sub-%C3%A3-accuracy
#2
Nicholas F Polizzi, Yibing Wu, Thomas Lemmin, Alison M Maxwell, Shao-Qing Zhang, Jeff Rawson, David N Beratan, Michael J Therien, William F DeGrado
Protein catalysis requires the atomic-level orchestration of side chains, substrates and cofactors, and yet the ability to design a small-molecule-binding protein entirely from first principles with a precisely predetermined structure has not been demonstrated. Here we report the design of a novel protein, PS1, that binds a highly electron-deficient non-natural porphyrin at temperatures up to 100 °C. The high-resolution structure of holo-PS1 is in sub-Å agreement with the design. The structure of apo-PS1 retains the remote core packing of the holoprotein, with a flexible binding region that is predisposed to ligand binding with the desired geometry...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168495/a-unifying-paradigm-for-naphthoquinone-based-meroterpenoid-bio-synthesis
#3
Zachary D Miles, Stefan Diethelm, Henry P Pepper, David M Huang, Jonathan H George, Bradley S Moore
Bacterial meroterpenoids constitute an important class of natural products with diverse biological properties and therapeutic potential. The biosynthetic logic for their production is unknown and defies explanation via classical biochemical paradigms. A large subgroup of naphthoquinone-based meroterpenoids exhibits a substitution pattern of the polyketide-derived aromatic core that seemingly contradicts the established reactivity pattern of polyketide phenol nucleophiles and terpene diphosphate electrophiles...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168494/vibronically-coherent-ultrafast-triplet-pair-formation-and-subsequent-thermally-activated-dissociation-control-efficient-endothermic-singlet-fission
#4
Hannah L Stern, Alexandre Cheminal, Shane R Yost, Katharina Broch, Sam L Bayliss, Kai Chen, Maxim Tabachnyk, Karl Thorley, Neil Greenham, Justin M Hodgkiss, John Anthony, Martin Head-Gordon, Andrew J Musser, Akshay Rao, Richard H Friend
Singlet exciton fission (SF), the conversion of one spin-singlet exciton (S1) into two spin-triplet excitons (T1), could provide a means to overcome the Shockley-Queisser limit in photovoltaics. SF as measured by the decay of S1 has been shown to occur efficiently and independently of temperature, even when the energy of S1 is as much as 200 meV less than that of 2T1. Here we study films of triisopropylsilyltetracene using transient optical spectroscopy and show that the triplet pair state (TT), which has been proposed to mediate singlet fission, forms on ultrafast timescales (in 300 fs) and that its formation is mediated by the strong coupling of electronic and vibrational degrees of freedom...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168493/site-selective-oxidation-amination-and-epimerization-reactions-of-complex-polyols-enabled-by-transfer-hydrogenation
#5
Christopher K Hill, John F Hartwig
Polyoxygenated hydrocarbons that bear one or more hydroxyl groups comprise a large set of natural and synthetic compounds, often with potent biological activity. In synthetic chemistry, alcohols are important precursors to carbonyl groups, which then can be converted into a wide range of oxygen- or nitrogen-based functionality. Therefore, the selective conversion of a single hydroxyl group in natural products into a ketone would enable the selective introduction of unnatural functionality. However, the methods known to convert a simple alcohol, or even an alcohol in a molecule that contains multiple protected functional groups, are not suitable for selective reactions of complex polyol structures...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168491/structure-and-reactivity-of-a-mononuclear-gold-ii-complex
#6
Sebastian Preiß, Christoph Förster, Sven Otto, Matthias Bauer, Patrick Müller, Dariush Hinderberger, Haleh Hashemi Haeri, Luca Carella, Katja Heinze
Mononuclear gold(II) complexes are very rare labile species. Transient gold(II) species have been suggested in homogeneous catalysis and in medical applications, but their geometric and electronic structures have remained essentially unexplored: even fundamental data, such as the ionic radius of gold(II), are unknown. Now, an unprecedentedly stable neutral gold(II) complex of a porphyrin derivative has been isolated, and its structural and spectroscopic features determined. The gold atom adopts a 2+2 coordination mode in between those of gold(III) (four-coordinate square planar) and gold(I) (two-coordinate linear), owing to a second-order Jahn-Teller distortion enabled by the relativistically lowered 6s orbital of gold...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168490/single-crystal-to-single-crystal-intercalation-of-a-low-bandgap-superatomic-crystal
#7
Evan S O'Brien, M Tuan Trinh, Rose L Kann, Jia Chen, Giselle A Elbaz, Amrita Masurkar, Timothy L Atallah, Maria V Paley, Nilam Patel, Daniel W Paley, Ioannis Kymissis, Andrew C Crowther, Andrew J Millis, David R Reichman, X-Y Zhu, Xavier Roy
The controlled introduction of impurities into the crystal lattice of solid-state compounds is a cornerstone of materials science. Intercalation, the insertion of guest atoms, ions or molecules between the atomic layers of a host structure, can produce novel electronic, magnetic and optical properties in many materials. Here we describe an intercalation compound in which the host [Co6Te8(P(n)Pr3)6][C60]3, formed from the binary assembly of atomically precise molecular clusters, is a superatomic analogue of traditional layered atomic compounds...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168489/modular-probes-for-enriching-and-detecting-complex-nucleic-acid-sequences
#8
Juexiao Sherry Wang, Yan Helen Yan, David Yu Zhang
Complex DNA sequences are difficult to detect and profile, but are important contributors to human health and disease. Existing hybridization probes lack the capability to selectively bind and enrich hypervariable, long or repetitive sequences. Here, we present a generalized strategy for constructing modular hybridization probes (M-Probes) that overcomes these challenges. We demonstrate that M-Probes can tolerate sequence variations of up to 7 nt at prescribed positions while maintaining single nucleotide sensitivity at other positions...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168486/infrared-spectrum-and-structure-of-the-homochiral-serine-octamer-dichloride-complex
#9
Jongcheol Seo, Stephan Warnke, Kevin Pagel, Michael T Bowers, Gert von Helden
The amino acid serine is known to form a very stable octamer that has properties that set it apart from serine complexes of different sizes or from complexes composed of other amino acids. For example, both singly protonated serine octamers and anionic octamers complexed with two halogen ions strongly prefer homochirality, even when assembled from racemic D,L mixtures. Consequently, the structures of these complexes are of great interest, but no acceptable candidates have so far been identified. Here, we investigate anionic serine octamers coordinated with two chloride ions using a novel technique coupling ion mobility spectrometry-mass spectrometry with infrared spectroscopy, in combination with theoretical calculations...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168485/catalyst-controlled-oligomerization-for-the-collective-synthesis-of-polypyrroloindoline-natural-products
#10
Christopher R Jamison, Joseph J Badillo, Jeffrey M Lipshultz, Robert J Comito, David W C MacMillan
In nature, many organisms generate large families of natural product metabolites that have related molecular structures as a means to increase functional diversity and gain an evolutionary advantage against competing systems within the same environment. One pathway commonly employed by living systems to generate these large classes of structurally related families is oligomerization, wherein a series of enzymatically catalysed reactions is employed to generate secondary metabolites by iteratively appending monomers to a growing serial oligomer chain...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168484/global-profiling-of-lysine-reactivity-and-ligandability-in-the-human-proteome
#11
Stephan M Hacker, Keriann M Backus, Michael R Lazear, Stefano Forli, Bruno E Correia, Benjamin F Cravatt
Nucleophilic amino acids make important contributions to protein function, including performing key roles in catalysis and serving as sites for post-translational modification. Electrophilic groups that target amino-acid nucleophiles have been used to create covalent ligands and drugs, but have, so far, been mainly limited to cysteine and serine. Here, we report a chemical proteomic platform for the global and quantitative analysis of lysine residues in native biological systems. We have quantified, in total, more than 9,000 lysines in human cell proteomes and have identified several hundred residues with heightened reactivity that are enriched at protein functional sites and can frequently be targeted by electrophilic small molecules...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168483/bicyclic-baird-type-aromaticity
#12
Won-Young Cha, Taeyeon Kim, Arindam Ghosh, Zhan Zhang, Xian-Sheng Ke, Rashid Ali, Vincent M Lynch, Jieun Jung, Woojae Kim, Sangsu Lee, Shunichi Fukuzumi, Jung Su Park, Jonathan L Sessler, Tavarekere K Chandrashekar, Dongho Kim
Classic formulations of aromaticity have long been associated with topologically planar conjugated macrocyclic systems. The theoretical possibility of so-called bicycloaromaticity was noted early on. However, it has yet to be demonstrated by experiment in a simple synthetic organic molecule. Conjugated organic systems are attractive for studying the effect of structure on electronic features. This is because, in principle, they can be modified readily through dedicated synthesis. As such, they can provide useful frameworks for testing by experiment with fundamental insights provided by theory...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168482/uv-light-driven-prebiotic-synthesis-of-iron-sulfur-clusters
#13
Claudia Bonfio, Luca Valer, Simone Scintilla, Sachin Shah, David J Evans, Lin Jin, Jack W Szostak, Dimitar D Sasselov, John D Sutherland, Sheref S Mansy
Iron-sulfur clusters are ancient cofactors that play a fundamental role in metabolism and may have impacted the prebiotic chemistry that led to life. However, it is unclear whether iron-sulfur clusters could have been synthesized on prebiotic Earth. Dissolved iron on early Earth was predominantly in the reduced ferrous state, but ferrous ions alone cannot form polynuclear iron-sulfur clusters. Similarly, free sulfide may not have been readily available. Here we show that UV light drives the synthesis of [2Fe-2S] and [4Fe-4S] clusters through the photooxidation of ferrous ions and the photolysis of organic thiols...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168481/direct-mapping-of-the-angle-dependent-barrier-to-reaction-for-cl%C3%A2-%C3%A2-chd3-using-polarized-scattering-data
#14
Huilin Pan, Fengyan Wang, Gábor Czakó, Kopin Liu
The transition state, which gates and modulates reactive flux, serves as the central concept in our understanding of activated reactions. The barrier height of the transition state can be estimated from the activation energy taken from thermal kinetics data or from the energetic threshold in the measured excitation function (the dependence of reaction cross-sections on initial collision energies). However, another critical and equally important property, the angle-dependent barrier to reaction, has not yet been amenable to experimental determination until now...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168480/structural-snapshots-of-concerted-double-e-h-bond-activation-at-a-transition-metal-centre
#15
Joseph A B Abdalla, Alexa Caise, Christian P Sindlinger, Rémi Tirfoin, Amber L Thompson, Alison J Edwards, Simon Aldridge
Bond activation at a transition metal centre is a key fundamental step in numerous chemical transformations. The oxidative addition of element-hydrogen bonds, for example, represents a critical step in a range of widely applied catalytic processes. Despite this, experimental studies defining steps along the bond activation pathway are very rare. In this work, we report on fundamental studies defining a new oxidative activation pathway: combined experimental and computational approaches yield structural snapshots of the simultaneous activation of both bonds of a β-diketiminate-stabilized GaH2 unit at a single metal centre...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168479/catalytic-diastereo-and-enantioselective-additions-of-versatile-allyl-groups-to-n-h-ketimines
#16
Hwanjong Jang, Filippo Romiti, Sebastian Torker, Amir H Hoveyda
There are many biologically active organic molecules that contain one or more nitrogen-containing moieties, and broadly applicable and efficient catalytic transformations that deliver them diastereoselectively and/or enantioselectively are much sought after. Various methods for enantioselective synthesis of α-secondary amines are available (for example, from additions to protected/activated aldimines), but those involving ketimines are much less common. There are no reported additions of carbon-based nucleophiles to unprotected/unactivated (or N-H) ketimines...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168478/supramolecular-heterostructures-formed-by-sequential-epitaxial-deposition-of-two-dimensional-hydrogen-bonded-arrays
#17
Vladimir V Korolkov, Matteo Baldoni, Kenji Watanabe, Takashi Taniguchi, Elena Besley, Peter H Beton
Two-dimensional (2D) supramolecular arrays provide a route to the spatial control of the chemical functionality of a surface, but their deposition is in almost all cases limited to a monolayer termination. Here we investigated the sequential deposition of one 2D array on another to form a supramolecular heterostructure and realize the growth-normal to the underlying substrate-of distinct ordered layers, each of which is stabilized by in-plane hydrogen bonding. For heterostructures formed by depositing terephthalic acid or trimesic acid on cyanuric acid/melamine, we have determined, using atomic force microscopy under ambient conditions, a clear epitaxial arrangement despite the intrinsically distinct symmetries and/or lattice constants of each layer...
December 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168499/polymer-mechanochemistry-up-another-rung
#18
Stephen L Craig
No abstract text is available yet for this article.
November 23, 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168497/molecular-organic-networks-a-step-beyond-flatland
#19
Manfred Buck
No abstract text is available yet for this article.
November 23, 2017: Nature Chemistry
https://www.readbyqxmd.com/read/29168492/thoroughly-enthralling-thulium
#20
Polly Arnold
No abstract text is available yet for this article.
November 23, 2017: Nature Chemistry
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