1,721,076 research outputs found
Synthesis of chiral atropisomeric phosphonates and diphosphines
No full textDepuis une trentaine d'année, l'obtention de composés chiraux énantiopurs tient un rôle prépondérant dans la synthèse de molécules biologiquement actives, tout particulièrement dans les domaines de la pharmacie de l'agrochimie et de la parfumerie. Cet engouement pour la synthèse énantiosélective a conduit à la mise au point de multiples ligands chiraux et notamment les diphosphines chirales par atropoisomérie initiées par les travaux de Noyori et Takaya. Nous nous sommes intéressés à la synthèse de nouveaux ligands hétérocycliques bidents et chiraux par atropoisomérie par des voies de synthèse originale où une double construction des hétérocycles sera mise en œuvre dans l'étape clé. En parallèle, nous avons aussi développé une approche de synthèse permettant l'obtention de mono et bis phosphonates atropochiraux utilisant des allènes comme précurseurs de la synthèse.Atropisomeric diphosphine ligands play a crucial role in the synthesis of enantiopur molecules, particularly in pharmaceutical, agrochemical and flavors industries. Growing demand in asymmetric synthesis, impose to develop news ligands by rapid, economic and effective strategies of synthesis. This optically pure ligand was combined with multiples transition metal to form catalyst what will have used wide variety of entioselective reaction type.Over the past few years, a new family of ligands has emerged, possessing biheterocyclic skeleton and thus allowing the introduction of different steric and electronic interactions. We will report a efficient syntheses of the new atropisomeric five-membered heterocyclic diphosphines with original strategy of synthesis whose the main stages consist in a double heterocyclic construction. In the second part, we will develop an approach permitting to obtain atropochiral phosphonates with a similar strategy of synthesis from allenylphosphine oxides or allenylphosphonates as precursors
Vers la recherche de structures antagonistes de l'action de la phencyclidine
No full textSIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Fluorowane fosfonianowe analogi fenyloalaniny – synteza, badania strukturalne i reaktywność
Get PDFWydział Chemiiα-Aminophosphonates containing in their structure fluorine atom(s) are bioactive compounds. Due to their biological and pharmacological activities, they have found a wide range of applications in medicinal and agricultural chemistry. First aim of the doctoral dissertation was the synthesis and structural characterization of phosphonate analogues of phenylalanine containing in the phenyl ring different number of fluorine atoms, as potential inhibitors of aminopeptidase. α-Aminophosphonates were synthesized by one-pot two steps reaction. First, imine was generated, followed by the nucleophilic addition of diethyl phosphite. What is more, a convenient method for the synthesis of fluorinated aldehydes, which were not commercially available, was developed. In this work, novel monodeprotection method of diethyl phosphonate group by LiI leading to corresponding monosalt, and deprotection by Me3SiBr resulted in aminophosphonic acid, were developed. Additionally, reactivity of α-aminophosphonates towards aromatic nucleophilic substitution was studied. A large library of para substituted fluorinated analogues of phenylalanine was synthesized in the reactions with different nucleophiles such as thiolates, amines and phenolates.W ostatnich latach coraz większe znaczenie zyskuje synteza fluorowanych pochodnych aminofosfonianów. Fluorowane aminofosfoniany wykazują działanie przeciwnowotworowe, przeciwwirusowe, przeciwbakteryjne ponadto, mogą również działać jako inhibitory enzymów. Celem niniejszej rozprawy było zsyntezowanie fosfonianowych analogów fenyloalaniny zawierających w swojej strukturze różną ilość atomów fluoru znajdujących się w różnych pozycjach pierścienia aromatycznego. Celem było również przeprowadzenie badań reaktywności otrzymanych analogów. Uzyskane aminofosfoniany mogą być potencjalnymi inhibitorami aminopeptydaz, a ponadto mogą wykazywać działanie przeciwnowotworowe. Fluorowane fosfonianowe analogi fenyloalaniny otrzymano w wyniku reakcji dwuetapowej. W pierwszym etapie wytworzono iminę, a następnie w wyniku nukleofilowej addycji fosforynu dietylu uzyskano α-aminofosfonian. Opracowano metodę syntezy niedostępnych komercyjnie fluorowanych aldehydów, stanowiących substraty w reakcjach otrzymywania aminofosfonianów. Ponadto, opracowano nową metodę monodeprotekcji grupy dietylofosfonianowej z zastosowaniem LiI. W niniejszej pracy przeprowadzono badania reaktywności fluorowanych fosfonianowych analogów fenyloalaniny w reakcjach SNAr. Zsyntezowano bibliotekę para podstawionych związków posiadających perfluorowany pierścień aromatyczny
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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