1,720,957 research outputs found
A convenient synthesis of oxandrolone through a regioselective Candida antarctica lipase-catalyzed transformation
No full textThe use of a regioselective CAL-catalyzed transformation of a suitable intermediate allowed a convenient synthesis of oxandrolone, an anabolic hormone actualy employed to improve the quality of life for patients with HIV-infection
A comparative molecular modeling study of dydrogesterone with other progestational agents through theoretical calculations and nuclear magnetic resonance spectroscopy
No full text6-Dehydroretroprogesterone (dydrogesterone) and three other natural or synthetic progestins (progesterone, retroprogesterone, and 6-dehydroprogesterone) were submitted to a conformational study through theor. calcns. at the B3LYP/6-31G* level and high field NMR spectroscopy. The study allows to define the role of the two structural features which differentiate these steroids, i.e., the C9 and C10 configuration and the C6-C7 unsatn. The combined effects of the conformational preference of A ring, detd. by the configuration at C9 and C10, and the enhanced rigidity due to the C6-C7 double bond, could account both for the higher activity and selectivity of dydrogesterone with respect to the other three steroids
A full conformational characterization of 13-ethylprogestogens through theoretical calculations and nuclear magnetic resonance spectroscopy
No full textThe conformational preference of a group of 13-ethylsteoids and related estranes have been determined through theoretical calculations at B3LYp/6-31G level in order to ascertain differences and similarities in conformational behavior which might, in principle, influence the activity. Attention was focussed on two geometrical features usually related to the progestional activity of this class of compounds, namely, the inversion of the A ring and the orientation of the 13-ethyl group. The present calculations show that the absence of the C10 methyl group, like in levonorgestrel, 3-ketodesogestrel, and gestodene, makes the inversion of the A ring easier than in norethisterone andethisterone even if in any case the 1alpha,2beta-half-chair conformation remains preferred. The presence of ethyl group for the trans orientation is maintened by all the 13-ethylprogestogens though in gestodene also the g+ gauche conformation is significantly populated. This preference was experimentally supported through a high field NMR spetroscopy study of the ethylsteroid
A simple synthesis of gestodene from 18-methyl-4-estren-3,17-dione
No full textA simple synthesis enable us to obtain the progestin gestodene, in five steps and satisfatory yields from 18-methyl-estren-3,17-dione. This was accomplished through the selective protection of C-3 carbonyl group aa a cyclic ketal and the installation of a phenylsulfoxide group at the C-16 positio
Synthesis of the immunosuppressive agent 2-morpholinoethyl mycophenolate by a lipase-catalyzed transesterification
No full textThe synthesis of 2-morpholinoethyl mycophenolate was realized by an enzymic transesterification of simple esters of mycophenolic acid with 2-morpholinoethanol. Best results were achieved by a Candida antarctica lipase B (CAL B) catalyzed transesterification of Et mycophenolate in toluene. CAL B showed to selectively transform only the Et ester function leaving unreacted the other functional groups present on the substrate. By this way 2-morpholinoethyl mycophenolate was obtained in satisfactory yields from mycophenolic acid (84%)
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Full text linkWe 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
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