scholarly journals Synthesis of cis-hydrindan-2,4-diones bearing an all-carbon quaternary center by a Danheiser annulation

2018 ◽  
Vol 14 ◽  
pp. 2597-2601 ◽  
Author(s):  
Gisela V Saborit ◽  
Carlos Cativiela ◽  
Ana I Jiménez ◽  
Josep Bonjoch ◽  
Ben Bradshaw
Keyword(s):  
Building Blocks ◽  
Ring System ◽  
Core Nucleus ◽  
Keto Ester ◽  
The Core ◽  
Quaternary Center

A straightforward synthetic entry to functionalized hydrindane compounds based on a rapid assembly of the core nucleus by a Danheiser cycloaddition is reported. Valuable bicyclic building blocks containing the fused five and six-membered carbocyclic ring system can be achieved in only four steps from a simple acyclic β-keto ester.

scholarly journals Studies on polynuclear furoquinones. Part 1: Synthesis of tri- and tetra-cyclic furoquinones simulating BCD/ABCD ring system of furoquinone diterpenoids

2009 ◽  
Vol 5 ◽  
Author(s):  
Faruk Hasan Shaik ◽  
Gandhi Kumar Kar
Keyword(s):  
Acid Derivative ◽  
Boronic Acid ◽  
Functional Group ◽  
Suzuki Coupling ◽  
Ring System ◽  
Core Nucleus ◽  
Tanshinone I ◽  
The Core ◽  
Acetic Ester ◽  
Naphthyl Acetate

Synthesis of phenanthro[1,2-b]furan-10,11-dione, the core nucleus present in Tanshinone-I is described in 8–10 steps starting from 2-bromo-3,4-dihydro-1-naphthaldehyde. The bromoaldehyde was converted to methyl 2-(2-bromo-1-naphthyl)acetate or 2-(2-bromo-1-naphthyl)acetonitrile following the protocol of functional group transformations. Subsequent Suzuki coupling of this ester/nitrile derivative with furan-2-boronic acid produced [2-(2-furyl)-1-naphthyl]acetic ester/nitrile which on hydrolysis furnished the corresponding acid derivative. Cyclization of the acid followed by oxidation of the phenol, with Fremy’s salt, produced the tetra-cyclic furoquinone, phenanthro[1,2-b]furan-10,11-dione. This method has also been extended for the synthesis of the tricyclic furoquinone, naphtho[1,2-b]furan-4,5-dione.

Tele-Substitution Reactions in the Synthesis of a Promising Class of Antimalarials

2020 ◽  
Author(s):  
Marat Korsik ◽  
Edwin Tse ◽  
David Smith ◽  
William Lewis ◽  
Peter J. Rutledge ◽  
...  
Keyword(s):  
Heterocyclic Ring ◽  
Ring System ◽  
Substitution Reactions ◽  
Laboratory Notebook ◽  
Polar Solvents ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Core ◽  
Nmr Data

<p></p><p>We have discovered and studied a <i>tele</i>substitution reaction in a biologically important heterocyclic ring system. Conditions that favour the <i>tele</i>-substitution pathway were identified: the use of increased equivalents of the nucleophile or decreased equivalents of base, or the use of softer nucleophiles, less polar solvents and larger halogens on the electrophile. Using results from X-ray crystallography and isotope labelling experiments a mechanism for this unusual transformation is proposed. We focused on this triazolopyrazine as it is the core structure of the <i>in vivo </i>active anti-plasmodium compounds of Series 4 of the Open Source Malaria consortium.</p> <p> </p> <p>Archive of the electronic laboratory notebook with the description of all conducted experiments and raw NMR data could be accessed via following link <a href="https://ses.library.usyd.edu.au/handle/2123/21890">https://ses.library.usyd.edu.au/handle/2123/21890</a> . For navigation between entries of laboratory notebook please use file "Strings for compounds in the article.pdf" that works as a reference between article codes and notebook codes, also this file contain SMILES for these compounds. </p><br><p></p>

Design, Synthesis and Bioactivity of Core 1 O-glycan and its Derivative on Human Gut Microbiota

2019 ◽  
Vol 16 (12) ◽  
pp. 1348-1353
Author(s):  
Huanhuan Qu ◽  
Baixue Li ◽  
Jingyi Yang ◽  
Huaiwen Liang ◽  
Meixia Li ◽  
...  
Keyword(s):  
Gut Microbiota ◽  
Initial Step ◽  
Building Blocks ◽  
Glycan Structure ◽  
Human Gut ◽  
Design Synthesis ◽  
The Core ◽  
Human Gut Microbiota ◽  
Biochemical Studies ◽  
Gut Symbionts

Background: Disaccharide core 1 (Galβ1-3GalNAc) is a common O-glycan structure in nature. Biochemical studies have confirmed that the formation of the core 1 structure is an important initial step in O-glycan biosynthesis and it is of great importance for human body. Objective: Our study will provide meaningful and useful sights for O-glycan synthesis and their bioassay. And all the synthetic glycosides would be used as intermediate building blocks in the scheme developed for oligosaccharide construction. Methods: In this article, we firstly used chemical procedures to prepare core 1 and its derivative, and a novel disaccharide was efficiently synthesized. The structures of the synthesized compounds were elucidated and confirmed by 1H NMR, 13C NMR and MS. Then we employed three human gut symbionts belonging to Bacteroidetes, a predominantphyla in the distal gut, as models to study the bioactivity of core 1 and its derivative on human gut microbiota. Results: According to our results, both core 1 and derivative could support the growth of B. fragilis, especially the core 1 derivative, while failed to support the growth of B. thetaiotaomicron and B. ovatus. Conclusion: This suggested that the B. fragilis might have the specificity glycohydrolase to cut the glycosidic bond for acquiring monosaccharide.

Political Settlements and Economic Transformation

2018 ◽  
Author(s):  
Hazel Gray
Keyword(s):  
Institutional Economics ◽  
Building Blocks ◽  
Analytical Framework ◽  
Economic Transformation ◽  
New Institutional Economics ◽  
Technological Learning ◽  
The Core ◽  
1960S And 1970S ◽  
The 1960S ◽  
Political Settlement

This chapter sets out the analytical framework of political settlements and elaborates the framework to account for the socialist experiences of Tanzania and Vietnam in the 1960s and 1970s. A political settlement, as defined by Mushtaq Khan, is a combination of power and institutions that is mutually compatible and also sustainable in terms of economic and political viability. The chapter clarifies the core building blocks of the approach and sets out the main differences between political settlements and new institutional economics. The chapter then defines a socialist political settlement where productive rights are formally held by the collective and formal institutions protect common and collectively owned assets. The attempts to construct a socialist political settlement left important institutional, political, and economic legacies. These shaped incentives and constraints which influenced a number of critical processes at the heart of economic development—related to technological learning, accumulation for investment, and political stabilization.

A RECONFIGURABLE ARCHITECTURE FOR IMAGE PROCESSING AND COMPUTER VISION

1995 ◽  
Vol 09 (02) ◽  
pp. 201-229 ◽  
Author(s):  
SUCHENDRA M. BHANDARKAR ◽  
HAMID R. ARABNIA ◽  
JEFFREY W. SMITH
Keyword(s):  
Image Processing ◽  
Computer Vision ◽  
Hough Transform ◽  
Broad Class ◽  
Building Blocks ◽  
Ring System ◽  
Reconfigurable Architecture ◽  
Vlsi Implementation ◽  
Ring Network ◽  
Linear Features

In this paper we describe a reconfigurable architecture for image processing and computer vision based on a multi-ring network which we call a Reconfigurable Multi-Ring System (RMRS). We describe the reconfiguration switch for the RMRS and also describe its VLSI implementation. The RMRS topology is shown to be regular and scalable and hence well-suited for VLSI implementation. We prove some important properties of the RMRS topology and show that a broad class of algorithms for the n-cube can be mapped to the RMRS in a simple and elegant manner. We design and analyze a class of procedural primitives for the SIMD RMRS and show how these primitives can be used as building blocks for more complex parallel operations. We demonstrate the usefulness of the RMRS for problems in image processing and computer vision by considering two important operations—the Fast Fourier Transform (FFT) and the Hough transform for detection of linear features in an image. Parallel algorithms for the FFT and the Hough transform on the SIMD RMRS are designed using the aforementioned procedural primitives. The analysis of the complexity of these algorithms shows that the SIMD RMRS is a viable architecture for problems in computer vision and image processing.

A de novo Synthesis of Oxindoles from Cyclohexanone-Derived γ-Keto-ester Acceptors Using a Desaturative Amination–Cyclization Approach

Synthesis ◽  
2021 ◽  
Author(s):  
Henry P. Caldora ◽  
Sebastian Govaerts ◽  
Shashikant U. Dighe ◽  
Oliver J. Turner ◽  
Daniele Leonori
Keyword(s):  
Amino Acids ◽  
Primary Amine ◽  
De Novo ◽  
Building Blocks ◽  
De Novo Synthesis ◽  
Keto Ester ◽  
Mild Conditions ◽  
Blockbuster Drug

Here we report a desaturative approach for oxindole synthesis. This method uses simple γ-ester-containing cyclohexanones and primary amine building blocks as coupling partners. A dual photoredox–cobalt manifold is used to generate a secondary aniline that, upon heating, cyclizes with the pendent ester functionality. The process operates under mild conditions and was applied to the modification of several amino acids, the blockbuster drug mexiletine, as well as the formation of dihydroquinolinones.

Biosynthesis of Carbohydrates and Amino Acids

2016 ◽  
Author(s):  
Gary W. Morrow
Keyword(s):  
Amino Acids ◽  
Construction Materials ◽  
Building Blocks ◽  
General Term ◽  
Molecular Formula ◽  
Biosynthetic Pathways ◽  
Hydrated Form ◽  
The Core ◽  
Carbon Dioxide Co2 ◽  
Structure And Metabolism

We have already seen that some of the basic building blocks used in the biosynthesis of natural products are amino acids such as phenylalanine, tyrosine, and others. These and other crucial construction materials such as the acyl group in acetyl-CoA are all ultimately derived from carbohydrates. In this chapter, we will present an abbreviated overview of the components of carbohydrate structure and metabolism sufficient for our purposes going forward, with a schematic flowchart showing how carbohydrates and amino acids are modified, combined, and branched off in various ways to yield the distinct set of biosynthetic pathways that will form the core of the remainder of the text. We will finish the chapter with a brief, general review of amino acid nomenclature and structure with emphasis on the key amino acids that will be used throughout the remainder of the text. We know that plants make glucose (C6H12O6) by photosynthesis using light, water (H2O), and carbon dioxide (CO2). Another way of looking at the formula for glucose is C6(H2O)6, that is, six carbon atoms and six water molecules. Thus, glucose was originally referred to as a hydrated form of carbon—a carbohydrate. But this is a very general term since there are many different types of carbohydrate compounds. One way to broadly classify carbohydrates is to identify them as either mono- (one), di- (two), oligo- (a few) or poly- (many) saccharides. For example, glucose (C6H12O6) cannot be broken down into simpler carbohydrates by simple hydrolysis, so it is classified as a monosaccharide, that is, a single, discrete carbohydrate compound. On the other hand, the carbohydrate sucrose (C12H22O11) is classified as a disaccharide since when it is subjected to aqueous hydrolysis, it yields two different monosaccharide carbohydrates, namely glucose (C6H12O6) and fructose (C6H12O6). Noting that glucose and fructose are different compounds but with the same molecular formula, they must be related to one another either as stereoisomers or as constitutional isomers, so further refinement of classification is needed. Structurally speaking, most monosaccharide carbohydrates are simply polyhydroxyaldehydes (aldoses) or polyhydroxyketones (ketoses) which can be further classified using a combination of aldo- or keto- prefixes along with suffixes such as triose, tetrose, pentose, or hexose to designate the number of carbon atoms.

Enantioselective Synthesis of Alcohols and Amines: The Fujii/Ohno Synthesis of (+)-Lysergic Acid

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Kinetic Resolution ◽  
Lysergic Acid ◽  
Enantioselective Synthesis ◽  
Amino Acid Derivative ◽  
State University ◽  
University Of Arkansas ◽  
Keto Ester ◽  
Colorado State University ◽  
Quaternary Center ◽  
The University

Ramón Gómez Arrayás and Juan C. Carretero of the Universidad Autónoma de Madrid effected (Chem. Commun. 2011, 47, 6701) enantioselective conjugate borylation of an unsaturated sulfone 1, leading to the alcohol 2. Robert E. Gawley of the University of Arkansas found (J. Am. Chem. Soc. 2011, 133, 19680) conditions for enantioselective ketone reduction that were selective enough to distinguish between the ethyl and propyl groups of 3 to give 4. Vicente Gotor of the Universidad de Oviedo used (Angew. Chem. Int. Ed. 2011, 50, 8387) an overexpressed Baeyer-Villiger monoxygenase to prepare 6 by dynamic kinetic resolution of 5. Li Deng of Brandeis University prepared (J. Am. Chem. Soc. 2011, 133, 12458) 8 in high ee by kinetic enantioselective migration of the alkene of racemic 7. Bernhard Breit of the Freiburg Institute for Advanced Studies established (J. Am. Chem. Soc. 2011, 133, 20746) the oxygenated quaternary center of 10 by the addition of benzoic acid to the allene 9. Keith R. Fandrick of Boehringer Ingelheim constructed (J. Am. Chem. Soc. 2011, 133, 10332) the oxygenated quaternary center of 13 by enantioselective addition of the propargylic nucleophile 12 to 11. Yian Shi of Colorado State University devised (J. Am. Chem. Soc. 2011, 133, 12914) conditions for the enantioselective transamination of the α-keto ester 14 to the amine 15. Professor Deng added (Adv. Synth. Catal. 2011, 353, 3123) 18 to an enone 17 to give the protected amine 19. Song Ye of the Institute of Chemistry, Beijing effected (J. Am. Chem. Soc. 2011, 133, 15894) elimination/addition of an unsaturated acid chloride 20 to give the γ-amino acid derivative 22. Frank Glorius of the Universität Münster added (Angew. Chem. Int. Ed. 2011, 50, 1410) an aldehyde 23 to 24 to give the amide 25. Sentaro Okamoto of Kanagawa University designed (J. Org. Chem. 2011, 76, 6678) an organocatalyst for the enantioselective Steglich rearrangement of 26, creating the aminated quaternary center of 27. Most impressive of all was the report (Org. Lett. 2011, 13, 5460) by Hélène Lebel of the Université de Montréal of the direct enantioselective C–H amination of 28 to give 29.

scholarly journals A unified view of density-based methods for semi-supervised clustering and classification

2019 ◽  
Vol 33 (6) ◽  
pp. 1894-1952 ◽  
Author(s):  
Jadson Castro Gertrudes ◽  
Arthur Zimek ◽  
Jörg Sander ◽  
Ricardo J. G. B. Campello
Keyword(s):  
Supervised Classification ◽  
Clustering Algorithms ◽  
Building Blocks ◽  
Large Collection ◽  
Supervised Clustering ◽  
The Core ◽  
Density Based Clustering ◽  
Clustering And Classification ◽  
Unified View ◽  
New Framework

Abstract Semi-supervised learning is drawing increasing attention in the era of big data, as the gap between the abundance of cheap, automatically collected unlabeled data and the scarcity of labeled data that are laborious and expensive to obtain is dramatically increasing. In this paper, we first introduce a unified view of density-based clustering algorithms. We then build upon this view and bridge the areas of semi-supervised clustering and classification under a common umbrella of density-based techniques. We show that there are close relations between density-based clustering algorithms and the graph-based approach for transductive classification. These relations are then used as a basis for a new framework for semi-supervised classification based on building-blocks from density-based clustering. This framework is not only efficient and effective, but it is also statistically sound. In addition, we generalize the core algorithm in our framework, HDBSCAN*, so that it can also perform semi-supervised clustering by directly taking advantage of any fraction of labeled data that may be available. Experimental results on a large collection of datasets show the advantages of the proposed approach both for semi-supervised classification as well as for semi-supervised clustering.

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