1,720,974 research outputs found
Synthesis and antimicrobial properties of substituted 3-aminoxy-(E)-2-methoxyiminopropionyl penicillins and cephalosporins
No full textThe 3-aminoxy-(E)-2-methoxyiminopropionyl penicillins 13 and cephalosporins 14 and 15 were synthesized and assayed for their antimicrobial activity on Gram-positive and Gram-negative bacteria whether producers of β-lactamases or otherwise. Compounds 13, 14, and 15 exhibited an activity which was generally lower than that of the corresponding phenylacetyl derivative: penicillin G (4), cephaloram (5), and phenylacetamidodesacetoxycephalosporanic acid (6). Furthermore, the comparison of the minimum inhibitory concentration values of some of the new 2-methoxyimino 3-aminoxypropionyl derivatives 13-15 with those of the corresponding ones 1-3 lacking the 2-methoxyimino substituent showed that the introduction of the 2-methoxyimino group of E configuration on the aminoxypropionamido side chain of 1-3 gives compounds (13-15) which do not generally possess better antimicrobial properties
X-Ray analysis, theoretical studies and alfa-adrenergic biopharmacological properties of 1-(2,5-dimethoxyphenyl)-2-aminoethanol and its morpholine analogue.
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Crystal and molecular structure of 2ß-acetoxymethyl-3α-methoxy-2α-methyl-3ß-(p-nitrobenzoyloxymethyl)-6ß-phenoxyacetamidopenam
No full textThe S configuration of the C2 carbon of the penam derivative 6 was unequivocally determined by means of X-ray crystallographic analysis. Crystals are monoclinic, space group P2, with Z = 2, unit cell dimensions a = 9.252(3), b = 15.075(2), c = 10.463(1) À, (:I = 111.76°. The structure was solved by direct methods and refined by a least-squares procedure to an R value ofO.050 for 2482 observed independent reflections. The relevant molecular parameters of 6 are compared with the corresponding ones of other penam derivati ves
Conversion reactions of cepham into penam systems. A route to determine the relative configurations of two diastereoisomeric 3-bromo-4-methoxycepham derivatives
No full textThe p-nitrobenzoates I were stereospecifically transformed with AgOAc-AcOH into the penam derivs. II. Oxidn. of II yielded the (S)- and (R)-sulfoxides. The (R)-sulfoxide of the α-acetoxymethyl isomer was thermally converted into the (S)-sulfoxide of the β-acetoxymethyl isomer. The configurations of II and the sulfoxides were assigned on the basis of 1H NMR studies and mechanistic considerations. The exclusive formation of II from I implies the intermediate formation of the diastereoisomeric α- and β-episulfonium ions, which undergo regiospecific attack of the nucleophile on the methylene carbon
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
Synthesis and antiviral activity of dihydroxycyclohexyl pyrimidine and purine carbocyclic nucleosides
No full textSome novel dihydroxycyclohexyl pyrimidine and purine carbocyclic nucleosides were prepared and tested for inhibitory activity against Cytomegalovirus and Herpes virus- 1 and -2
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
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