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https://www.readbyqxmd.com/read/28430454/accessing-polyoxygenated-dibenzofurans-via-the-union-of-phenols-and-o-benzoquinones-rapid-syntheses-of-metabolites-isolated-from-ribes-takare
#1
Meng Yao Zhang, Russell A Barrow
The construction of polyoxygenated dibenzo[b,d]furan frameworks from the union of substituted phenols/naphthols and o-benzoquinones via a Michael-oxidation-oxa-Michael cascade is reported. The power of this transformation is demonstrated in the generation of a library of highly substituted dibenzofurans, featuring specifically substituted molecules containing broad ranges of functionality. The utility of this method is showcased in the total syntheses of two dibenzofurans isolated from Ribes takare, assembling the carbon scaffold of both natural products in one operation...
April 21, 2017: Organic Letters
https://www.readbyqxmd.com/read/28430196/organocatalytic-stereoselective-8-2-and-6-4-cycloadditions
#2
Rasmus Mose, Gert Preegel, Jesper Larsen, Sofie Jakobsen, Eva Høgh Iversen, Karl Anker Jørgensen
Cycloadditions that involve more than six π electrons are termed higher-order cycloadditions and are an excellent tool for solving complex synthetic challenges, as they provide direct access to polycyclic scaffolds that contain medium-sized rings. They have interesting synthetic potential for the discovery of new bioactive molecules and in natural product synthesis. It is peculiar that stereocontrolled [8+2] and [6+4] cycloadditions have been largely neglected for the past 50 years. Here we demonstrate a cross-dienamine activation of 2-cyclopentenone and the unprecedented endocyclic linear-dienamine activation of 2-cyclohexenones and 2-cycloheptenones...
May 2017: Nature Chemistry
https://www.readbyqxmd.com/read/28427007/novel-and-revisited-approaches-in-antituberculosis-drug-discovery
#3
REVIEW
Jennifer Herrmann, Jan Rybniker, Rolf Müller
The increasing prevalence of multidrug-resistant Mycobacterium tuberculosis (Mtb) necessitates the discovery and development of novel drugs against tuberculosis. In this review, we focus on two recent approaches that led to the discovery of promising antitubercular compound classes: (I) Hits derived from large compound library screens are increasingly difficult to translate into clinical application; this in turn fostered the development of innovative screening methods. (II) An alternative strategy towards high-quality hits and leads is to evaluate chemically diverse scaffolds which can be found among natural products...
April 17, 2017: Current Opinion in Biotechnology
https://www.readbyqxmd.com/read/28426060/hierarchically-scaffolded-cop-cop2-nanoparticles-controllable-synthesis-and-their-application-as-a-well-matched-bifunctional-electrocatalyst-for-overall-water-splitting
#4
Wan Li, Shilin Zhang, Qining Fan, Fazhi Zhang, Sailong Xu
Transition metal phosphide (TMP) nanostructures have stimulated increasing interest for use in water splitting owing to their abundant natural sources and high activity for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Typically, the preparation of hierarchical TMPs involves the utilization of expensive or dangerous phosphorus sources, and, in particular, the understanding of topotactic transformations of the precursors to crystalline phases-which could be utilized to enhance electrocatalytic performance-remains very limited...
April 20, 2017: Nanoscale
https://www.readbyqxmd.com/read/28425951/modification-of-natural-eudesmane-scaffolds-via-mizoroki-heck-reactions
#5
Mohamed Zaki, Mohamed Akssira, Sabine Berteina-Raboin
The Mizoroki-Heck reaction was applied to substrates derived from isocostic and ilicic acids, important sesquiterpene components of Dittrichia viscosa L. Greuter that were extracted directly from plant material collected in Morocco. After optimization of the metallo-catalysis conditions, various aryl-groups were successfully introduced on the exocyclic double bond with an exclusive E-configuration and without racemization.
April 20, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28425525/exploiting-hydrogen-bonding-interactions-to-probe-smaller-linear-and-cyclic-diamines-binding-to-g-quadruplexes-a-dft-and-molecular-dynamics-study
#6
Mrinal Kanti Si, Anik Sen, Bishwajit Ganguly
G-quadruplexes are formed by the association of four guanine bases through Hoogsteen hydrogen bonding in guanine-rich sequences of DNA and exist in the telomere as well as in promoter regions of certain oncogenes. The sequences of G-quadruplex-DNA are targets for the design of molecules that can bind and can be developed as anti-cancer drugs. The linear and cyclic protonated diamines have been explored to bind to G-quadruplex-DNA through hydrogen bonding interactions. The quadruplex-DNA binders exploit π-stacking and hydrogen bonding interactions with the phosphate backbone of loops and grooves...
April 20, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28423958/strategies-and-perspectives-of-assembling-multi-enzyme-systems
#7
Shi-Zhen Wang, Yong-Hui Zhang, Hong Ren, Ya-Li Wang, Wei Jiang, Bai-Shan Fang
Multi-enzyme complexes have the potential to achieve high catalytic efficiency for sequence reactions due to their advantages in eliminating product inhibition, facilitating intermediate transfer and in situ regenerating cofactors. Constructing functional multi-enzyme systems to mimic natural multi-enzyme complexes is of great interest for multi-enzymatic biosynthesis and cell-free synthetic biotransformation, but with many challenges. Currently, various assembly strategies have been developed based on the interaction of biomacromolecules such as DNA, peptide and scaffolding protein...
April 20, 2017: Critical Reviews in Biotechnology
https://www.readbyqxmd.com/read/28422724/utilizing-combinatorial-engineering-to-develop-tie2-targeting-antagonistic-angiopoetin-2-ligands-as-candidates-for-anti-angiogenesis-therapy
#8
Tomer Shlamkovich, Lidan Aharon, William A Barton, Niv Papo
In many human cancers, the receptor tyrosine kinase (RTK) Tie2 plays important roles in mediating proliferation, survival, migration and angiogenesis. Thus, molecules that could potently inhibit activation of the Tie2 receptor would have a significant impact on cancer therapy. Nevertheless, attempts to develop Tie2-targeted inhibitors have met with little success, and there is currently no FDA-approved therapeutic selectively targeting Tie2. We used a combinatorial protein engineering approach to develop a new generation of angiopoietin (Ang) 2-derived Tie2 antagonists as potential cancer therapeutics and as tools to study angiogenesis...
April 4, 2017: Oncotarget
https://www.readbyqxmd.com/read/28421720/enantioselective-organocatalytic-synthesis-of-a-secoyohimbane-inspired-compound-collection-with-neuritogenic-activity
#9
Herbert Waldmann, Tim Förster, Sara Lopéz-Tosco, Slava Ziegler, Andrey P Antonchick
Natural products provide evolutionary validated core structures inspiring the synthesis of new compound collections endowed with neurite growth-promoting activity. Rhynchophylline is the major component of Uncaria species which has been used to treat neurological diseases in Chinese traditional medicine. According to the structure of this spirocyclic secoyohimbane alkaloid, we developed a highly enantioselective and efficient organocatalyzed synthesis method to provide the tetracyclic secoyohimbane scaffold incorporating a quaternary and three tertiary stereogenic centers in a one-pot multistep reaction sequence...
April 19, 2017: Chembiochem: a European Journal of Chemical Biology
https://www.readbyqxmd.com/read/28420994/scaffold-diversity-of-fungal-metabolites
#10
Mariana González-Medina, John R Owen, Tamam El-Elimat, Cedric J Pearce, Nicholas H Oberlies, Mario Figueroa, José L Medina-Franco
Many drug discovery projects rely on commercial compounds to discover active leads. However, current commercial libraries, with mostly synthetic compounds, access a small fraction of the possible chemical diversity. Natural products, in contrast, possess a vast structural diversity and have proven to be an outstanding source of new drugs. Several chemoinformatic analyses of natural products have demonstrated their diversity and structural complexity. However, to our knowledge, the scaffold content and structural diversity of fungal secondary metabolites have never been studied...
2017: Frontiers in Pharmacology
https://www.readbyqxmd.com/read/28419941/pamam-generation-4-incorporated-gelatin-3d-matrix-as-an-improved-dermal-substitute-for-skin-tissue-engineering
#11
Somnath Maji, Tarun Agarwal, Tapas Kumar Maiti
The study explored the prospects of PAMAM (generation 4) applicability in gelatin based scaffolds for skin tissue engineering. The effect of PAMAM on physico-chemical and biological characteristics of gelatin scaffolds was evaluated. Gelatin scaffolds (with/without PAMAM) were prepared by lyophilization, chemically crosslinked by glutaraldehyde and characterized for their morphology (pore size), chemical features (bond nature), water adsorption, biodegradation and biological compatibility. The study demonstrated that addition of PAMAM did not significantly alter the pore size distribution or porosity of the scaffolds...
April 5, 2017: Colloids and Surfaces. B, Biointerfaces
https://www.readbyqxmd.com/read/28416674/inducing-protein-aggregation-by-extensional-flow
#12
John Dobson, Amit Kumar, Leon F Willis, Roman Tuma, Daniel R Higazi, Richard Turner, David C Lowe, Alison E Ashcroft, Sheena E Radford, Nikil Kapur, David J Brockwell
Relative to other extrinsic factors, the effects of hydrodynamic flow fields on protein stability and conformation remain poorly understood. Flow-induced protein remodeling and/or aggregation is observed both in Nature and during the large-scale industrial manufacture of proteins. Despite its ubiquity, the relationships between the type and magnitude of hydrodynamic flow, a protein's structure and stability, and the resultant aggregation propensity are unclear. Here, we assess the effects of a defined and quantified flow field dominated by extensional flow on the aggregation of BSA, β2-microglobulin (β2m), granulocyte colony stimulating factor (G-CSF), and three monoclonal antibodies (mAbs)...
April 17, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28416216/3-phenyl-4-oxy-5-phenyl-4-5-dihydro-1h-pyrazole-a-fascinating-molecular-framework-to-study-the-enantioseparation-ability-of-the-amylose-3-5-dimethylphenylcarbamate-chiral-stationary-phase-part-ii-solvophobic-effects-in-enantiorecognition-process
#13
Marco Pierini, Simone Carradori, Sergio Menta, Daniela Secci, Roberto Cirilli
The enantiomers of five chiral compounds incorporating the 3-(phenyl-4-oxy)-5-phenyl-4,5-dihydro-(1H)-pyrazole scaffold and differing only in the linear alkyl chain (varying in length from 1 to 5 carbon atoms) linked to the oxygen atom were directly separated on the amylose (3,5-dimethylphenylcarbamate) based Chiralpak AD-3 chiral stationary phase. The effects of the mobile phase composition, the structure of the analytes and temperature on the retention and enantioselectivity were investigated. It was found that the enantiomeric separations were in all cases enthalpy-driven and disfavored by entropic term...
April 4, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28415517/fabrication-of-novel-biodegradable-porous-bone-scaffolds-based-on-amphiphilic-hydroxyapatite-nanorods
#14
Xiaoyan Zheng, Junfeng Hui, Hui Li, Chenhui Zhu, Xiufu Hua, Haixia Ma, Daidi Fan
This paper describes a new synthetic strategy and biological application for novel amphiphilic hydroxyapatite (HAp) nanorods. The prepared HAp nanorods were able to be dispersed in water, ethyl alcohol and cyclohexane. The co-anchoring of the multidentate ligands of PEG 20000 and hydrophobic oleic acid (OA) on the rods' surfaces endowed them with excellent amphibious properties. Utilizing amphiphilic HAp nanorods with excellent biocompatibility as the inorganic phase, human-like collagen (HLC) as the organic phase and natural genipin as the cross-linker, optimal HLC/HAp porous scaffolds (HLC: HAp=1:4, w/w) were fabricated...
June 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
https://www.readbyqxmd.com/read/28415442/small-intestinal-submucosa-a-potential-osteoconductive-and-osteoinductive-biomaterial-for-bone-tissue-engineering
#15
Mei Li, Chi Zhang, Mengjie Cheng, Qiaoqiao Gu, Jiyuan Zhao
SIS is an acellular, naturally occurring collagenous extracellular matrix (ECM) material with various bioactive factors, which broadly applied in tissue engineering in clinic. Several studies have applied SIS in bone tissue engineering to enhance bone regeneration in animal models. However, the mechanism was rarely investigated. The aim of the current study was to investigate the osteoconductivity and osteoinductivity of SIS scaffold to bone regeneration systematically and the potential mechanism. Our results showed that SIS scaffold with excellent biocompatibility was beneficial for cell attachment, proliferation, migration and osteogenic differentiation of various cells contributing to bone repair...
June 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
https://www.readbyqxmd.com/read/28415417/porous-45s5-bioglass%C3%A2-based-scaffolds-using-stereolithography-effect-of-partial-pre-sintering-on-structural-and-mechanical-properties-of-scaffolds
#16
Boonlom Thavornyutikarn, Passakorn Tesavibul, Kriskrai Sitthiseripratip, Nattapon Chatarapanich, Bryce Feltis, Paul F A Wright, Terence W Turney
Scaffolds made from 45S5 Bioglass® ceramic (BG) show clinical potential in bone regeneration due to their excellent bioactivity and ability to bond to natural bone tissue. However, porous BG scaffolds are limited by their mechanical integrity and by the substantial volume contractions occurring upon sintering. This study examines stereolithographic (SLA) methods to fabricate mechanically robust and porous Bioglass®-based ceramic scaffolds, with regular and interconnected pore networks and using various computer-aided design architectures...
June 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
https://www.readbyqxmd.com/read/28414079/in-vivo-reprogramming-of-immune-cells-technologies-for-induction-of-antigen-specific-tolerance
#17
REVIEW
Ryan M Pearson, Liam M Casey, Kevin R Hughes, Stephen D Miller, Lonnie D Shea
Technologies that induce antigen-specific immune tolerance by mimicking naturally occurring mechanisms have the potential to revolutionize the treatment of many immune-mediated pathologies such as autoimmunity, allograft rejection, and allergy. The immune system intrinsically has central and peripheral tolerance pathways for eliminating or modulating antigen-specific responses, which are being exploited through emerging technologies. Antigen-specific tolerogenic responses have been achieved through the functional reprogramming of antigen-presenting cells or lymphocytes...
April 14, 2017: Advanced Drug Delivery Reviews
https://www.readbyqxmd.com/read/28413973/docking-related-survey-on-natural-product-based-new-monoamine-oxidase-inhibitors-and-their-therapeutic-potential
#18
Priyanka Dhiman, Neelam Malik, Anurag Khatkar
This is an exciting period for research on monoamine oxidase and its effects on central nervous system. As the current hitting-one-target therapeutic strategy has become quite inefficient for the treatment of various neurological disorders. The objective of this review is to identify and critically discuss the computational development of multi-target natural and related ligand-MAO protein docking approaches in the study of monoamine oxidase (MAO) enzymes. Computational development of the new compounds form natural and related synthetic origin, active as MAO inhibitors (MAOIs) were discussed in some detail...
April 14, 2017: Combinatorial Chemistry & High Throughput Screening
https://www.readbyqxmd.com/read/28412440/transient-networks-of-spatio-temporal-connectivity-map-communication-pathways-in-brain-functional-systems
#19
Alessandra Griffa, Benjamin Ricaud, Kirell Benzi, Xavier Bresson, Alessandro Daducci, Pierre Vandergheynst, Jean-Philippe Thiran, Patric Hagmann
The study of brain dynamics enables us to characterize the time-varying functional connectivity among distinct neural groups. However, current methods suffer from the absence of structural connectivity information. We propose to integrate infra-slow neural oscillations and anatomical-connectivity maps, as derived from functional and diffusion MRI, in a multilayer-graph framework that captures transient networks of spatio-temporal connectivity. These networks group anatomically wired and temporary synchronized brain regions and encode the propagation of functional activity on the structural connectome...
April 12, 2017: NeuroImage
https://www.readbyqxmd.com/read/28412325/designing-metal-contained-enzyme-mimics-for-prodrug-activation
#20
REVIEW
Baoji Du, Dan Li, Jin Wang, Erkang Wang
Enzyme-activated prodrug therapy (EAPT) is a widely-used and effective treatment method for cancer by converting the prodrugs into the drugs at the demanded time and space, whose key step is prodrug activation. Traditional prodrug activations are mostly dependent on the natural enzymes, which are unstable, expensive and hard to be functionalized. The emerging enzyme mimics, especially the metal-contained enzyme mimics (MEMs), provide a potential chance for improving the traditional EAPT because of their high stability, low cost and easiness of preparation and functionalization...
April 12, 2017: Advanced Drug Delivery Reviews
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