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An unexpected reaction of pyridine with acetyl chloride to give dihydropyridine and piperidine derivatives
Full text linkSynthesis of dihydropyridine and piperidine derivatives via an unexpected reaction of pyridine with acetyl chloride
Full text linkAcetyl chloride reacts with pyridine to give a mixture of N-acetyl-1,4- and 1,2-dihydropyridyl acetic acid (1a,b) after water quenching. The reactioninvolves the formation of a zwitterionic ketene enolate intermediate which results from
deprotonation of the acetyl moiety of the in situ formed N-acetyl pyridinium ion.The effect on the reaction outcome of different parameters as temperature, pyridine/acetyl chloride molar ratio, and as Lewis acids and triflate counterion presence has been studied in detail, and a reaction mechanism has been proposed
Selective reactions using N-(tert-butoxycarbonyl)-2-(tert-butyldimethylsiloxy)pyrrole: concise asymmetric syntheses of (+)-1-deoxy-8-epi-castanospermine and its enantiomer
No full textAdvantage being taken of the versatility of the siloxydiene TBSOP in asymmetric synthesis, (6S,7R,8S,8aR)-6,7,8-trihydroxyindolizidine 11 has been assembled from the L-threose derivative 1 in six or eight steps in 22-30% overall yield. Pivotal to the success of this total synthesis venture is the ready availability of unsaturated lactam 2 with complete stereocontrol. As a corollary, the synthesis of the known indolizidine enantiomer ent-11 confirms the feasibility of the procedure. The structure of compound 5 has been determined by X-ray crystallography
A New Synthetic Spiroketal: Studies on Antitumor Activity on Murine Melanoma Model In Vivo and Mechanism of Action In Vitro
No full textBackground: In a previous study, we synthesised a new spiroketal derivative, inspired to natural products, that has shown high antiproliferative activity, potent telomerase inhibition and proapoptotic activity on several human cell lines. Objective: This work focused on the study of in vivo antitumor effect of this synthetic spiroketal on a murine melanoma model. In order to shed additional light on the origin of the antitumor effect, in vitro studies were performed. Methods: Spiroketal was administered to B16F10 melanoma mice at a dose of 5 mg/Kg body weight via intraperitoneum at alternate days for 15 days. Tumor volume measures were made every 2 days starting after 12 days from cells injection. The effects of the spiroketal on tumor growth inhibition, apoptosis induction, and cell cycle modification were investigated in vitro on B16 cells. HIF1α gene expression, the inhibition of cells migration and the changes induced in cytoskeleton conformation were evaluated. Results: Spiroketal displayed proapoptotic activity and high antitumor activity in B16 cells with nanomolar IC50. Moreover it has shown to inhibit cell migration, to strongly reduce the HIF1α expression and to induce strongly deterioration of cytoskeleton structure. A potent dose-dependent antitumor efficacy in syngenic B16/C57BL/6J murine model of melanoma was observed with the suppression of tumor growth by an average of 90% at a dose of 5 mg/kg. Conclusion: The synthesized spiroketal shows high antitumor activity in the B16 cells in vitro at nM concentration and a dose-dependent antitumor efficacy in syngenic B16/C57BL/6J mice. The results suggest that this natural product inspired spiroketal may have a potential application in melanoma therapy
Sintesi stereoselettiva di ureido-zuccheri via 5-(alditol-1-C-il) idantoina building blocks: effetto del gruppo protettivo dell'idantoina sulla diastereoselettività
No full textIn questo lavoro verrà presentata la sintesi stereoselettiva di interessanti
ureido-zuccheri che sfrutta 5-poliidrossialchil-idantoine come building blocks.
Presenteremo inoltre uno studio sull’effetto del gruppo protettivo dell’idantoina sulla
disatereoselettività della reazione con aldeidi omochirali
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
Synthesis of indole derivatives by domino hydroformylation/indolization of 2-nitrocinnamaldehydes
No full textThe present work furnishes an innovative preparation of substituted indoles based on tandem hydroformylation, where the chemo- and the regio-selectivities are good, so the yield of the reaction. The novelty has been established in the four-step transformation of substituted alpha nitrocinnamaldehydes into desired indoles in a one-pot reaction. Under hydroformylation reaction conditions we have been able to trigger off a cascade of reactions, which gave substituted indoles in high yields. Useful intermediates are prepared by using this technique for the synthesis of well-known biologically active molecules. (C) 2008 Elsevier B.V. All rights reserved
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