1,720,971 research outputs found
Re-Examination of Cyclized Products from Lycopodine and Clavolonine
Full text linkTitle: Re-Examination of Cyclized Products from Lycopodine and Clavolonine, Author: Norman M. C. You, Location: ThodeCyclized products derived from lycopodine and clavolonine through
the Hofmann and von Braun reactions were prepared and examined. From
evidence obtained new structures are proposed for the Hofmann products
of lycopodine and clavolonine.ThesisMaster of Science (MS
The Role of 2-Piperidneacetic Acid in the Biosythesis of Lycopodine
Full text linkTitle: The Role of 2-Piperidneacetic Acid in the Biosythesis of Lycopodine, Author: Thi T. Nguyen, Location: ThodeThe role of 2-piperidineacetic acid in the biosynthesis of lycopodine was tested by feeding experiments with β-14C-2-piperidineacetic acid hydrochloride. The compound was synthesized starting from
2-picolylchloride which was treated with K14CN yielding the labeled
2-pyridineacetonitrile. Conversion of the nitrile to the ester was followed by reduction of the pyridine ring and hydrolysis of the ester function. The labeled β-14C-2-piperidineacetic acid was obtained in 60% radiochemical yield. When administered to L. tristachyum, alone or along with radioactive lysine, β-14C-2-piperidineacetic acid showed very low
incorporation into lycopodine. The incorporation of lysine into lycopodine
showed however that the alkaloid was being synthesized in the plant in the course of the feeding experiments. These results cast doubt on the hypothesis that 2-piperidineacetlc acid is an intermediate on the pathway to lycopodine from lysine.ThesisMaster of Science (MS
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
Studies in Alkaloid Chemistry: Part I. Minor Alkaloids of Lycopodium flabelliforme; Part II. Model Studies leading to a synthesis of cularine
No full textPart I. The results of an investigation of the minor alkaloids of Lycopodium flabelliforme using elution chromatography and countercurrent distribution are presented. Several alkaloids not previously reported to occur in this species were isolated and identified. A new alkaloid, hydroxy-de-N-methyl-α-obscurine, has been isolated and a structure proposed for it on the basis of physical evidence. A sufficient quantity of Lycopodium alkaloid L.5 which we have named flabellidine was isolated to permit the elucidation of its structure. Part II. A synthesis of 9-xanthenemethylamine and its rearrangement to the ring-expanded alcohol under the condition of the Demjanov reaction is described.Doctor of Philosophy (PhD
Minor Alkaloids of Lycopodium Flabelliforme
No full textAn examination of the alkaloids of L. flabelliform var. ambiguum was undertaken. By using chromatographic and counter-current distribution methods, the known alkaloids lycopodine, dihydrolycopodine and a-obscurine have been isolated. In addition two new minor alkaloids, fiabelliformine (C16H25O2N) and flabelline (C18H30ON2) have been isolated. The structure of flabelline has been established by infrared and nuclear magnetic resonance data, and chemical examination.ThesisMaster of Science (MSc
Studies on the Chemistry of Annotinine
Full text linkThe amino acid C14H19O4N, obtained from annotinine by oxidative fission of ring A, has been converted to the o,N-diacetyl acyclic anhydride C18H22O6N, and the anhydride ring has been shown to be five-membered. Oxidation studies have been carried out on the N-methyl lactone C17H27O2N, obtained by fission of ring A, and the oxidation products isolated and characterized. Hofmann degradation studies on the N-methyl lactone have been carried out and the products isolated from this reaction are discussed in relation to the known structure of the alkaloid.ThesisMaster of Science (MS
STUDIES ON THE STRUCTURE OF ANNOTINE
Full text linkAnnotine (C16Ο21Η3), a minor alkaloid of L. annotinum L.,
has been studied by physical and chemical methods. The studies have
established the nature of the functional groups in the alkaloid. On
the basis of the information obtained and of a probable structural relationship to other Lycopodium alkaloids a structure is proposed for annotine.ThesisMaster of Science (MS
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