1,720,991 research outputs found
Diastereoselectivity in the synthesis of syn-cis-3a-hydroxypyrrolo[2,3-b] indoline N<sup>α′</sup>-methyl-dipeptide methyl esters
No full textDescribed herein is a high yielding, diastereoselective synthesis of the syn-cis hydroxypyrroloindoline moiety by oxidation of the Nα-trityl- tryptophan-Nα-methyl-dipeptide methyl esters.</p
Synthesis, characterisation, and in vitro evaluation of pro <sup>2</sup>-Ile<sup>3</sup>-S-deoxo-amaninamide and pro<sup>2</sup>-D-allo- Ile<sup>3</sup>-5-deoxo-amaninamide: Implications for structure-activity relationships in amanitin conformation and toxicity
No full textThe amatoxins are a family of toxic bicyclic peptides that inhibit RNA polymerase II. Herein we discuss an improved synthesis of these compounds from easily obtainable amino acids by means of a solid-phase methodology. Interestingly, we obtained two products of the same mass following our final macrocyclisation, relating to a similar distribution of products described in some previous reports. One of these products was the desired amatoxin ; Pro 2-Ile3-S-deoxo-amaninamide 1b. The other compound, after thorough investigation, was confirmed to be the epimer Pro2-D-allo- Ile3-S-deoxoamaninamide 1a, not an atropisomer structure as previously suggested in syntheses of related amanitin analogues. Crystallographic data of 1a confirms the presence of a βII-turn, rather than a βI-turn common to the natural toxin and 1b. This difference explains the large variation in CD spectra, although it seems to have relatively little effect on the bioactivity in vitro. These data provide new insights into the bicyclic amatoxin structure.</p
Fig. 3. Key 1H–1H in Dimeric aporphine alkaloids from the twigs of Trivalvaria costata (Hook.f. & Thomson) I.M.Turner
No full textFig. 3. Key 1H–1H COSY and HMBC (1H→13C) correlations of compounds 1–10 and 15.Published as part of Teerapongpisan, Passakorn, Suthiphasilp, Virayu, Phukhatmuen, Piyaporn, Rujanapun, Narawadee, Chaiyosang, Boonyanoot, Tontapha, Sarawut, Maneerat, Tharakorn, Patrick, Brian O., Duangyod, Thidarat, Charoensup, Rawiwan, Andersen, Raymond J. & Laphookhieo, Surat, 2023, Dimeric aporphine alkaloids from the twigs of Trivalvaria costata (Hook.f. & Thomson) I.M.Turner, pp. 1-11 in Phytochemistry (113586) 207 on page 6, DOI: 10.1016/j.phytochem.2023.113586, http://zenodo.org/record/829048
Fig. 5 in Dimeric aporphine alkaloids from the twigs of Trivalvaria costata (Hook.f. & Thomson) I.M.Turner
No full textFig. 5. ECD spectra (MeOH) of compounds ()-(1), (+)-(1), ()-(2), (+)-(2), ()-(3), (+)-(3), (+)-(4), ()-(5), (+)-(5), ()-(6), and (+)-(6).Published as part of Teerapongpisan, Passakorn, Suthiphasilp, Virayu, Phukhatmuen, Piyaporn, Rujanapun, Narawadee, Chaiyosang, Boonyanoot, Tontapha, Sarawut, Maneerat, Tharakorn, Patrick, Brian O., Duangyod, Thidarat, Charoensup, Rawiwan, Andersen, Raymond J. & Laphookhieo, Surat, 2023, Dimeric aporphine alkaloids from the twigs of Trivalvaria costata (Hook.f. & Thomson) I.M.Turner, pp. 1-11 in Phytochemistry (113586) 207 on page 6, DOI: 10.1016/j.phytochem.2023.113586, http://zenodo.org/record/829048
Fig. 2. X in Dimeric aporphine alkaloids from the twigs of Trivalvaria costata (Hook.f. & Thomson) I.M.Turner
No full textFig. 2. X-ray ORTEP-like of 1, 3, and 14.Published as part of Teerapongpisan, Passakorn, Suthiphasilp, Virayu, Phukhatmuen, Piyaporn, Rujanapun, Narawadee, Chaiyosang, Boonyanoot, Tontapha, Sarawut, Maneerat, Tharakorn, Patrick, Brian O., Duangyod, Thidarat, Charoensup, Rawiwan, Andersen, Raymond J. & Laphookhieo, Surat, 2023, Dimeric aporphine alkaloids from the twigs of Trivalvaria costata (Hook.f. & Thomson) I.M.Turner, pp. 1-11 in Phytochemistry (113586) 207 on page 3, DOI: 10.1016/j.phytochem.2023.113586, http://zenodo.org/record/829048
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
Dibenzyl ferrocene-1,1&#8242;-dicarboxylate
No full textIn the title compound, [Fe(C13H11O2)2], there are markedly different orientations of the two phenylmethoxycarbonyl substituents [O&#8212;C&#8212;C&#8212;C torsion angles = 84.5&#8197;(3) and 139.6&#8197;(2)&#176;]. These orientations are mediated by a number of intermolecular C&#8212;H...O interactions, which result in a one-dimensional hydrogen-bonded network of molecules
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