1,720,972 research outputs found
Resolution of inherently chiral 1,4-2,5-calix[8]bis-crown-4 derivatives by enantioselective HPLC
No full textThe first example of the resolution of inherently chiral calix[8]arenes, 1,4-2,5-calix[8]bis-crown-4 1 and its methyl derivatives 2-4, has been achieved using enantioselective HPLC methods. The enantiomeric nature of isolated (+)-1 and (-)-1 was confirmed by CD spectra, specific optical rotation and H-1 NMR in the presence of Pirkle's reagent. A rationale is given for the observed HPLC enantioselectivity among compounds 2-4. (C) 1997 Elsevier Science Ltd
Resolution of inherently chiral calix[4]arenes with AABB and CDCD substitution patterns at upper and lower rim, respectively
No full textMethyl beta-Orcinolcarboxylate and Depsides from Parmelia Furfuracea
No full textParmelia furfuracea, a common conifer lichen, produce antimicrobical constituents whose extracts have been utilized to give base materials for perfumes. Crude extracts of this lichen were tested against representative different class of microorganisms. A strong activity was exhibited against Bacillus subtilis and Escherichia col
[3+2]-Cycloaddition Reaction between Chiral Oxaziridines and Nitriles: Enantioselective Synthesis of 2,3-Dihydro-1,2,4-oxadiazoles.
No full textEnantiomerically pure 2,3-dihydro-1,2,4-oxadiazoles were synthesized by a cycloaddition reaction between chiral oxaziridines and nitriles. Assignment of absolute configurations was made by X-ray diffraction analysis, NOESY spectra, and theoretical calculations
The Structure of Laurobtusol, A New Rearranged Sesquiterpenoid From the Mediterranean Red Alga Laurencia-obtusa
No full textAn alcohol with a new tricyclic humulane skeleton, laurobtusol, was isolated from the Mediterranean Red Alga Laurencia obtusa. The structure was established mainly by 2 D NMR methods and the relative configuration was assigned by a quantiative computer simulation of the lanthanide induced shifts in the H-1 NMR spectrum and Molecular Mechanics calculation (MM2)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
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