pinecone/core-2020-05-10-deduplication huggingface dataset:
Total synthesis of the protected aglycon of fidaxomicin (Tiacumicin B, Lipiarmycin A3)

Fidaxomicin, also known as tiacumicin B or lipiarmycin A3, is a novel macrocyclic antibiotic that is used in hospitals for the treatment of Clostridium difficile infections. This natural product has also been shown to have excellent bactericidal activity against multidrug-resistant Mycobacterium tuberculosis. In spite of its attractive biological activity, no total synthesis has been reported to date. The enantioselective synthesis of the central 18-membered macrolactone is reported herein. The key reactions include ring-closing metathesis between a terminal olefin and a dienoate moiety for macrocyclization, a vinylogous Mukaiyama aldol reaction, and a Stille coupling reaction of sterically demanding substrates. The retrosynthesis involves three medium-sized fragments, thus leading to a flexible yet convergent synthetic route
Metal-Atom Impact on the Self-Assembly of Cup-and-Ball Metalloporphyrin–Fullerene Conjugates

A fullerene-ammonium derivative has been combined with different metalloporphyrin-crown ether receptors to generate very stable supermolecules. The combination of fullerene-porphyrin and ammonium-crown ether interactions leads to a strong chelate effect as evidenced by a high effective molarity (3.16 M). The different parameters influencing the stability of the supramolecular ensembles,in particular the nature of the metal in the porphyrin moiety, have been rationalized with the help of theoretical calculations thus providing new insights into fullerene-porphyrin interactions
Total synthesis of albicidin: A lead structure from #Xanthomonas albilineans# for potent antibacterial gyrase inhibitors

The peptide antibiotic albicidin, which is synthesized by the plant pathogenic bacterium Xanthomonas albilineans, displays remarkable antibacterial activity against various Gram-positive and Gram-negative microorganisms. The low amounts of albicidin obtainable from the producing organism or through heterologous expression are limiting factors in providing sufficient material for bioactivity profiling and structure-activity studies. Therefore, we developed a convergent total synthesis route toward albicidin. The unexpectedly difficult formation of amide bonds between the aromatic amino acids was achieved through a triphosgene-mediated coupling strategy. The herein presented synthesis of albicidin confirms the previously determined chemical structure and underlines the extraordinary antibacterial activity of this compound. The synthetic protocol will provide multigram amounts of albicidin for further profiling of its drug properties. (Résumé d'auteur
Reversible control of nanoparticle functionalization and physicochemical properties by dynamic covalent exchange

This work was supported by the EPSRC (EP/K016342/1 and DTG), the University of St Andrews, and by a Royal Society of Edinburgh/Scottish Government Fellowship (E.R.K.).Existing methods for the covalent functionalization of nanoparticles rely on kinetically controlled reactions, and largely lack the sophistication of the preeminent oligonucleotide-based noncovalent strategies. Here we report the application of dynamic covalent chemistry for the reversible modification of nanoparticle (NP) surface functionality, combining the benefits of non-biomolecular covalent chemistry with the favorable features of equilibrium processes. A homogeneous monolayer of nanoparticle-bound hydrazones can undergo quantitative dynamic covalent exchange. The pseudomolecular nature of the NP system allows for the in situ characterization of surface-bound species, and real-time tracking of the exchange reactions. Furthermore, dynamic covalent exchange offers a simple approach for reversibly switching—and subtly tuning—NP properties such as solvophilicity.Publisher PDFPeer reviewe
Self-regulation mechanism for charged point defects in hybrid halide perovskites

Hybrid halide perovskites such as methylammonium lead iodide (CH3NH3PbI3) exhibit unusually low free-carrier concentrations despite being processed at low-temperatures from solution. We demonstrate, through quantum mechanical calculations, that an origin of this phenomenon is a prevalence of ionic over electronic disorder in stoichiometric materials. Schottky defect formation provides a mechanism to selfregulate the concentration of charge carriers through ionic compensation of charged point defects. The equilibrium charged vacancy concentration is predicted to exceed 0.4% at room temperature. This behavior, which goes against established defect conventions for inorganic semiconductors, has implications for photovoltaic performance
A Scalable Biomimetic Synthesis of Resveratrol Dimers and Systematic Evaluation of their Antioxidant Activities

An efficient synthetic route to the resveratrol oligomers quadrangularin A and pallidol is reported. It features a scalable biomimetic oxidative dimerization that proceeds in excellent yield and with complete regioselectivity. A systematic evaluation of the natural products and their synthetic precursors as radical‐trapping antioxidants has revealed that, contrary to popular belief, this mode of action is unlikely to account for their observed biological activity.Persistence pays off: A concise synthesis of the resveratrol oligomers quadrangularin A and pallidol was achieved by leveraging the persistence of 2,6‐di‐tert‐butyl phenol derived radical and quinone methide intermediates. Evaluation of these compounds as radical‐trapping antioxidants is presented and the results demonstrate that this mode of action is unlikely to account for the observed biological activity
Total synthesis of ramonanins A-D

The first total synthesis of the ramonanin family of lignan natural products is described. The short synthesis involves a 2,5-diaryl-3,4-dimethylene tetrahydrofuran intermediate, which participates in an unexpectedly facile Diels-Alder dimerization, generating all four natural products. Insights into the reactivity and stereoselectivity of the key dimerization are provided through computational studies employing B3LYP/6-31G(d) and M06-2X/6-31G(d) model chemistries.This work was supported by the Australian Research Council and a Marie Curie Career Integration Grant. M.N.P.-R. acknowledges that this research was undertaken with the assistance of resources provided at the NCI National Facility through the National Computational Merit Allocation Scheme supported by the Australian Government
Total Syntheses of Linear Poly-Thiazole/Oxazole Plantazolicin A and its biosynthetic precursor Plantazolicin B

Plantazolicin A, a linear decacyclic natural product, exhibits desirable selective activity against the causative agent of anthrax toxicity. The total synthesis of plantazolicin A and its biosynthetic precursor plantazolicin B was successfully achieved via an efficient, unified and highly convergent route featuring dicyclisations to form 2,4-concatenated oxazoles and the mild synthesis of thiazoles from natural amino acids. This report represents the first synthesis of plantazolicin B and includes the first complete characterization data for both natural products.We gratefully acknowledge Prof. D. A. Mitchell (University of Illinois
at Urbana-Champaign) for providing an authentic sample of
plantazolicin A and advice on purification, Peter Grice and Duncan
Howe for assistance with NMR spectroscopy, and generous funding
from the Royal Society (Newton International Fellowship—Z.E.W.),
the German Academic Exchange Service DAAD (S.F.), and the
Engineering and Physical Sciences Research Council.This is the final version. It was first published by Wiley at http://onlinelibrary.wiley.com/doi/10.1002/anie.201410063/abstrac
Formation of thin films of organic-inorganic perovskites for high-efficiency solar cells

Organic-inorganic perovskites are currently one of the hottest topics in photovoltaic (PV) research, with power conversion efficiencies (PCEs) of cells on a laboratory scale already competing with those of established thin-film PV technologies. Most enhancements have been achieved by improving the quality of the perovskite films, suggesting that the optimization of film formation and crystallization is of paramount importance for further advances. Here, we review the various techniques for film formation and the role of the solvents and precursors in the processes. We address the role chloride ions play in film formation of mixed-halide perovskites, which is an outstanding question in the field. We highlight the material properties that are essential for high-efficiency operation of solar cells, and identify how further improved morphologies might be achieved
Enantioselective Synthesis of α-Aminosilanes by Copper-Catalyzed Hydroamination of Vinylsilanes

The synthesis of α-aminosilanes by a highly enantio- and regioselective copper-catalyzed hydroamination of vinylsilanes is reported. The system employs Cu-DTBM-SEGPHOS as the catalyst, diethoxymethylsilane as the stoichiometric reductant, and O-benzoylhydroxylamines as the electrophilic nitrogen source. This hydroamination reaction is compatible with differentially substituted vinylsilanes, thus providing access to amino acid mimics and other valuable chiral organosilicon compounds.National Institutes of Health (U.S.) (Award GM58160
Live-cell imaging of endogenous mRNAs with a small molecule.

Determination of subcellular localization and dynamics of mRNA is increasingly important to understanding gene expression. A new convenient and versatile method is reported that permits spatiotemporal imaging of specific non-engineered RNAs in living cells. The method uses transfection of a plasmid encoding a gene-specific RNA aptamer, combined with a cell-permeable synthetic small molecule, the fluorescence of which is restored only when the RNA aptamer hybridizes with its cognitive mRNA. The method was validated by live-cell imaging of the endogenous mRNA of β-actin. Application of the technology to mRNAs of a total of 84 human cytoskeletal genes allowed us to observe cellular dynamics of several endogenous mRNAs including arfaptin-2, cortactin, and cytoplasmic FMR1-interacting protein 2. The RNA-imaging technology and its further optimization might permit live-cell imaging of any RNA molecules
Rhodium-Catalyzed (5+1) Annulations Between 2-Alkenylphenols and Allenes: A Practical Entry to 2,2-Disubstituted 2H-Chromenes

NOTICE: This is the peer reviewed version of the following article: Casanova, N., Seoane, A., Mascarelas, J. L., Gulías, M. (2015), Rhodium-Catalyzed (5+1) Annulations Between 2-Alkenylphenols
and Allenes: A Practical Entry to 2,2-Disubstituted 2H-Chromenes. Angew. Chem. Int. Ed., 54: 2374-2377 [doi: 10.1002/anie.201410350]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for self-archiving.Readily available alkenylphenols react with allenes under rhodium catalysis to provide valuable 2,2-disubstituted 2H-chromenes. The whole process, which involves the cleavage of one C-H bond of the alkenyl moiety and the participation of the allene as a one-carbon cycloaddition partner, can be considered a simple, versatile, and atom-economical (5+1) heteroannulation. The reaction tolerates a broad range of substituents both in the alkenylphenol and in the allene, and most probably proceeds through a mechanism involving a rhodium-catalyzed C-C coupling followed by two sequential pericyclic processes.This work was supported by the Spanish MINECO (grant: SAF2013-41943-R), the ERDF, the European Research Council (Advanced Grant No. 340055), and the Xunta de Galicia (grants: GRC2013-041, EM2013/036 and a Parga Pondal contract to M.G.). We also thank the orfeo-cinqa networkS
Palladium-Catalyzed Intramolecular C-H Difluoroalkylation: Synthesis of Substituted 3,3-Difluoro-2-oxindoles

The synthesis of 3,3-difluoro-2-oxindoles through a robust and efficient palladium-catalyzed C-H difluoroalkylation is described. This process generates a broad range of difluorooxindoles from readily prepared starting materials. The use of BrettPhos as the ligand was crucial for high efficiency. Preliminary mechanistic studies suggest that oxidative addition is the rate-determining step for this process.National Institutes of Health (U.S.) (GM46059)Japan Society for the Promotion of Science (Fellowship
Machine Assisted Organic Synthesis

For this new review we describe how the advent of machines is impacting on organic synthesis programs with particular emphasis on the practical issues associated with chemical reactor design. In the rapidly changing, multi-variant environment of the research laboratory, equipment needs to be modular to accommodate high and low temperatures and pressures, enzymes, multiphase systems, slurries, gases and organometallics. Additional technologies have been developed to facilitate more specialized reaction techniques such as electrochemical and photochemical methods. All of these areas create both opportunities and challenges during adoption as enabling technologies.The authors gratefully acknowledge support from UK Engineering and Physical Sciences Research Council (SVL and RMM), Woolf Fisher Trust (DEF) and Pfizer Worldwide Research and Development (CB, RJI).This is the accepted manuscript. The final version is available at http://onlinelibrary.wiley.com/doi/10.1002/anie.201410744/abstract
大環状アリーレンエチニレンの連続環化による新奇多環状芳香族化合物の創出

This is the author's version of a work that was accepted for publication in Chemistry - A European Journal. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms, may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Chemistry - A European Journal, VOLUME：18, ISSUE：4, DATE：2012-08-22, DOI: 10.1002/chem.201201061.This is the author's version of a work that was accepted for publication in Angewandte Chemie International Edition. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms, may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Angewandte Chemie International Edition, VOLUME：52, ISSUE：15, DATE：2013-02-28, DOI：10.1002/anie.201210233.This is the author's version of a work that was accepted for publication in Angewandte Chemie International Edition. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms, may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Angewandte Chemie International Edition, VOLUME：54, ISSUE：7, DATE：2015-01-14, DOI：10.1002/anie.201410791
Construction of a new class of tetracycline lead structures with potent antibacterial activity through biosynthetic engineering

Antimicrobial resistance and the shortage of novel antibiotics have led to an urgent need for new antibacterial drug leads. Several existing natural product scaffolds (including chelocardins) have not been developed because their suboptimal pharmacological properties could not be addressed at the time. It is demonstrated here that reviving such compounds through the application of biosynthetic engineering can deliver novel drug candidates. Through a rational approach, the carboxamido moiety of tetracyclines (an important structural feature for their bioactivity) was introduced into the chelocardins, which are atypical tetracyclines with an unknown mode of action. A broad-spectrum antibiotic lead was generated with significantly improved activity, including against all Gram-negative pathogens of the ESKAPE panel. Since the lead structure is also amenable to further chemical modification, it is a platform for further development through medicinal chemistry and genetic engineering
Stereochemical assignment of the protein-protein interaction inhibitor JBIR-22 by total synthesis

The authors acknowledge the EPSRC and Cancer Research UK (CRUK Grant No. C21383/A6950) for funding this research.Recent reports have highlighted the biological activity associated with a sub-family of the tetramic acid class of natural products. Despite the fact that members of this sub-family act as protein-protein interaction inhibitors of relevance to proteasome assembly, no synthetic work has been reported. This may be because this sub-family contains an unnatural 4,4-disubstitued glutamic acid, the synthesis of which provides a key challenge. Here we describe a highly stereoselective route to a masked form of this unnatural amino acid. This enabled the synthesis of two of the possible diastereomers of JBIR-22 and allowed its relative and absolute stereochemistry to be assigned.Publisher PDFPeer reviewe
Non-Centrosymmetric Homochiral Supramolecular Polymers of Tetrahedral Subphthalocyanine Molecules

This is the peer reviewed version of the following article: Angewandte Chemie - International Edition 54.8 (2015): 2543-2547, which has been published in final form at http://dx.doi.org/10.1002/anie.201411272. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingA combination of spectroscopy (UV/Vis absorption, emission, and circular dichroism), microscopy (AFM and TEM), and computational studies reveal the formation of non-centrosymmetric homochiral columnar subphthalocyanine assemblies. These assemblies form through a cooperative supramolecular polymerization process driven by hydrogen-bonding between amide groups, π-π stacking, and dipolar interactions between axial B-F bondsFunding from MINECO (CTQ2011-24187, CTQ2011-23659, CTQ2011-23659 and 02, CTQ2012-31914, and CTQ2012-35513-C02-01), CAM (S2013/MIT-2841 FOTO-CARBON), GVA (PROMETEO/2012/053
Rapid formation of a supramolecular polypeptide-DNA Hydrogel for in situ three-dimensional multilayer bioprinting

A rapidly formed supramolecular polypeptide–DNA hydrogel was prepared and used for in situ multilayer three-dimensional bioprinting for the first time. By alternative deposition of two complementary bio-inks, designed structures can be printed. Based on their healing properties and high mechanical strengths, the printed structures are geometrically uniform without boundaries and can keep their shapes up to the millimeter scale without collapse. 3D cell printing was demonstrated to fabricate live-cell-containing structures with normal cellular functions. Together with the unique properties of biocompatibility, permeability, and biodegradability, the hydrogel becomes an ideal biomaterial for 3D bioprinting to produce designable 3D constructs for applications in tissue engineering
Porous Solids Arising from Synergistic and Competing Modes of Assembly: Combining Coordination Chemistry and Covalent Bond Formation

Design and synthesis of porous solids employing both reversible coordination chemistry and reversible covalent bond formation is described. The combination of two different linkage modes in a single material presents a link between two distinct classes of porous materials as exemplified by metal–organic frameworks (MOFs) and covalent organic frameworks (COFs). This strategy, in addition to being a compelling material‐discovery method, also offers a platform for developing a fundamental understanding of the factors influencing the competing modes of assembly. We also demonstrate that even temporary formation of reversible connections between components may be leveraged to make new phases thus offering design routes to polymorphic frameworks. Moreover, this approach has the striking potential of providing a rich landscape of structurally complex materials from commercially available or readily accessible feedstocks.Teamwork saves the day when coordination chemistry and covalent bond formation can both occur in a single material. A balance between the incubation time of the organic components and solvent decomposition/base formation governs the competition between the two processes and determines the phase outcome. Even the temporary formation of reversible connections between components can be leveraged to make new phases
Total synthesis of (-)-caprazamycin A.

Caprazamycin A has significant antibacterial activity against Mycobacterium tuberculosis (TB). The first total synthesis is herein reported and features a) the scalable preparation of the syn-β-hydroxy amino acid with a thiourea-catalyzed diastereoselective aldol reaction, b) construction of a diazepanone with an unstable fatty-acid side chain, and c) global deprotection with hydrogenation. This report provides a route for the synthesis of related liponucleoside antibiotics with fatty-acid side chains
Intracellular modulation of excited-state dynamics in a chromophore dyad: Differential enhancement of photocytotoxicity targeting cancer cells

The photosensitized generation of reactive oxygen species, and particularly of singlet oxygen [O<inf>2</inf>(a1Δ<inf>g</inf>)], is the essence of photodynamic action exploited in photodynamic therapy. The ability to switch singlet oxygen generation on/off would be highly valuable, especially when it is linked to a cancer-related cellular parameter. Building on recent findings related to intersystem crossing efficiency, we designed a dimeric BODIPY dye with reduced symmetry, which is ineffective as a photosensitizer unless it is activated by a reaction with intracellular glutathione (GSH). The reaction alters the properties of both the ground and excited states, consequently enabling the efficient generation of singlet oxygen. Remarkably, the designed photosensitizer can discriminate between different concentrations of GSH in normal and cancer cells and thus remains inefficient as a photosensitizer inside a normal cell while being transformed into a lethal singlet oxygen source in cancer cells. This is the first demonstration of such a difference in the intracellular activity of a photosensitizer. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Ion‐Specific Oil Repellency of Polyelectrolyte Multilayers in Water: Molecular Insights into the Hydrophilicity of Charged Surfaces

Surface wetting on polyelectrolyte multilayers (PEMs), prepared by alternating deposition of polydiallyldimethylammonium chloride (PDDA) and poly(styrene sulfonate) (PSS), was investigated mainly in water‐solid‐oil systems. The surface‐wetting behavior of as‐prepared PEMs was well correlated to the molecular structures of the uncompensated ionic groups on the PEMs as revealed by sum frequency generation vibrational and X‐ray photoelectron spectroscopies. The orientation change of the benzenesulfonate groups on the PSS‐capped surfaces causes poor water wetting in oil or air and negligible oil wetting in water, while the orientation change of the quaternized pyrrolidine rings on the PDDA‐capped surfaces hardly affects their wetting behavior. The underwater oil repellency of PSS‐capped PEMs was successfully harnessed to manufacture highly efficient filters for oil‐water separation at high flux.Wet surfaces: Liquid wetting on charged surfaces is well correlated with the molecular nature of surface ionic groups. The orientation change of surface ionic groups either hardly affects water wetting if their configuration is isotropic, or markedly transforms poor water wetting in oil to poor water de‐wetting in water if their configuration is anisotropic, thus leading to excellent underwater oil repellency