1,721,030 research outputs found
Metabolism study and biological evaluation of bosentan derivatives
No full textBosentan, the first-in-class drug used in treatment of pulmonary arterial hypertension, is principally metabolized by the cytochromes P450, and it is responsible for cytochromes induction and drug-drug interaction events with moderate to severe consequences. A strategy to reduce drug-drug interactions consists of increasing the metabolic stability of the perpetrator, and fluorinated analogues are often designed to block the major sites of metabolism. In this paper bosentan analogues were synthesized, and their metabolism and biological activity were evaluated. All synthesized compounds showed an improved metabolic stability towards CYP2C9, with one maintaining a moderate antagonist effect towards the ETA receptor.
Copyright 2016 Elsevier Masson SAS. All rights reserved
Are carboxylic Esters Really Refractory to DAST? Fluorination of -Hydroxyesters with DAST
No full textAre carboxylic esters really refractory to DAST? On the fluorination of α-hydroxyesters with DAST
No full textDiethyl 2-alkyl-2-hydroxymalonates react with DAST almost exclusively at the ester carbonyl giving a mixture of ethyl 2-(ethoxydifluoromethyl)-2-hydroxyalkanoates, 1,1-bis(ethoxydifluoromethyl)alkan-1-ols when administered at room temperature in dichloromethane. The reaction was exploited in the synthesis of nucleus- and side-chain polyfluorinated indoles. The fluorination of substituted diethyl 2-[(1-tert-butoxycarbonylindol-3-yl)methyl]-2-hydroxymalonates with DAST gave a mixture of ethyl 2-(ethoxydifluoromethyl)-2-hydroxy-3-(1-tert-butoxycarbonylindol-3-yl)propionate, diastereomeric 1'-tert-butoxycarbonyl-2'-hydroxy-2,2-diethoxycarbonylspiro(cyclopropane-1,3'-indoline) and only traces of 1,1-bis(ethoxydifluoromethyl)-2-(1-tert-butoxycarbonylindol-3-yl)ethanol. The composition of these mixtures changes depending on the reaction conditions. Regioselectively substituted ethyl 2-hydroxy-2[(1-tert-butoxycarbonylindol-3-yl)methyl]-3,3,3-trifluoropropionate reacts with DAST at 0 degrees C in dichloromethane giving satisfactory yields of the corresponding 1-ethoxy-2-[(1-tert-butoxycarbonylindol-3-yl)methyl]-1,1,3,3,3-pentafluoropropan-2-ols as the exclusive reaction products. In the same reaction conditions, ethyl 3-(1-tert-butoxycarbonylindol-3-yl)-2-hydroxypropionate mainly provides 1'-tert-butoxycarbonyl-2'-hydroxy-2,2-diethoxycarbonylspiro(cyclopropane-1,3'-indoline) together with the "normal" fluorination product ethyl 3-(1-tert-butoxycarbonylindol-3-yl)-2-fluoropropionate. A plausible mechanism of this process is proposed in the following. (C) 2014 Elsevier B.V. All rights reserved
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
Importance of C*–H Based Modes and Large Amplitude Motions Effects in Vibrational Circular Dichroism Spectra: The Case of the Chiral Adduct of Dimethyl Fumarate and Anthracene.
No full textThe role played by the C*-H based modes (C* being the chiral carbon atom) and the large amplitude motions in the vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra is investigated. The example of an adduct of dimethyl fumarate and anthracene, i.e., dimethyl-(+)-(11R,12R)-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylate, and two deuterated isotopomers thereof specially synthesized for this goal, are considered. By comparing the experimental and DFT calculated spectra of the undeuterated and deuterated species, we demonstrate that the C*-H bending, rocking, and stretching modes in the VA and VCD spectra are clearly identified in well defined spectroscopic features. Further, significant information about the conformer distribution is gathered by analyzing the VA and VCD data of both the fingerprint and the C-H stretching regions, with particular attention paid to the band shape data. Effects related to the large amplitude motions of the two methoxy moieties have been simulated by performing linear transit (LT) calculations, which consists of varying systematically the relative positions of the two methoxy moieties and calculating VCD spectra for the partially optimized structures obtained in this way. The LT method allows one to improve the quality of calculated spectra, as compared to experimental results, especially in regard to relative intensities and bandwidths
Synthesis of new indole-based bisphosphonates and evaluation of their chelating ability in PE/CA-PJ15 cells
No full textBisphosphonates are the most important class of antiresorptive agents used against osteoclast-mediated bone loss, and, more recently, in oncology. These compounds have high affinity for calcium ions (Ca(2+)) and therefore target bone mineral, where they appear to be internalized selectively by bone-resorbing osteoclasts and inhibit osteoclast function. They are extensively used in healthcare, however they are affected by severe side effects; pharmacological properties of bisphosphonates depend on their molecular structure, which is frequently the cause of poor intestinal adsorption and low distribution. In this work we synthesized six novel bisphosphonate compounds having a variably substituted indole moiety to evaluate their extra- and intracellular calcium chelating ability in PE/CA-PJ15 cells. Preliminary in silico and in vitro ADME studies were also performed and the results suggested that the indole moiety plays an important role in cell permeability and metabolism properties
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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