1,720,958 research outputs found
Multi-Step Chemo-Enzymatic Synthesis of APIs in Non-Conventional Solvents
No full textThe goal of Green Chemistry is to develop sustainable synthetic processes by promoting the use of eco-friendly solvents. Among these, Deep Eutectic Solvents (DESs) have been employed in the synthesis of various pharmacologically active compounds. In this work, DESs were used for the preparation of α,β-unsaturated esters and sulfonamides, improving the eco-friendliness of the process compared to pre-existing methodologies. These solvents were also used for the preparation of optically active alcohols via biocatalytic processes using lactic acid bacteria and yeasts. The use of DESs enhanced the catalytic efficiency of stereoselective reductions of prochiral ketones. Finally, deracemization reactions and sequential metal-enzyme processes in DESs were investigated to obtain key intermediates for the synthesis of pharmaceutical compounds, thus developing more sustainable and industrially relevant synthetic methodologies.Scopo della chimica verde è realizzare processi sintetici sostenibili, tramite l’utilizzo di solventi ecocompatibili. Tra questi le miscele eutettiche profonde o Deep Eutectic Solvents (DESs), impiegate nella sintesi di numerosi composti farmacologicamente attivi. In questo lavoro abbiamo utilizzato i DESs per la preparazione di esteri α,β-insaturi e solfonammidi, migliorando l’ecocompatibilità del processo rispetto alle metodologie pre-esistenti. Tali solventi sono stati utilizzati per la preparazione di alcoli otticamente attivi tramite processi biocatalitici, impiegando batteri lattici e lieviti. Grazie all’uso dei DESs è stato possibile migliorare l’efficienza catalitica della riduzione stereoselettiva dei chetoni pro-chirali. Infine, sono state investigate reazioni di deracemizzazione e processi sequenziali metallo-enzimatici in DESs per ottenere intermedi chiave per la preparazione di composti farmaceutici, sviluppando metodologie di sintesi più sostenibili e industrialmente rilevanti
An enhanced stereoselective synthesis of α,β-unsaturated esters through the Horner–Wadsworth–Emmons reaction in deep eutectic solvents
Full text linkA new scalable synthesis of (E)-alpha,beta-unsaturated esters has been developed using protic, non-toxic, and biodegradable deep eutectic solvents through the Horner-Wadsworth-Emmons reaction between triethyl phosphonates and (hetero)aromatic carbonyl compounds, encompassing electron-withdrawing and electron-donating groups. Stereoselective preparation of disubstituted or trisubstituted ethyl cinnamate derivatives is achieved in the presence of LiOH, K2CO3, or DBU as bases, at room temperature and under air. Demonstrated with the synthesis of (E)-ethyl 3-(4-bromophenyl)acrylate, the same eutectic mixture (choline chloride/urea) proved to be reusable for three consecutive runs. Gram-scale reactions (10 mmol) can be carried out without the formation of side products, thereby ensuring high atom economy and an EcoScale score of 71.An enhanced stereoselective synthesis of alpha,beta-unsaturated esters has been developed using protic and biodegradable deep eutectic solvents
Switchable Deep Eutectic Solvents for Sustainable Sulfonamide Synthesis
Full text linkA sustainable and scalable protocol for synthesizing variously functionalized sulfonamides, from amines and sulfonyl chlorides, has been developed using environmentally responsible and reusable choline chloride (ChCl)-based deep eutectic solvents (DESs). In ChCl/glycerol (1:2 mol mol-1) and ChCl/urea (1:2 mol mol-1), these reactions yield up to 97% under aerobic conditions at ambient temperature within 2-12 h. The practicality of the method is exemplified by the sustainable synthesis of an FFA4 agonist and a key building block en route to anti-Alzheimer drug BMS-299897. A subtle interplay of electronic effects and the solubility characteristics of the starting materials in the aforementioned DESs seem to be responsible for driving the reaction successfully over the hydrolysis of sulfonyl chlorides. The procedure's eco-friendliness is validated by quantitative metrics like the E-factor and the EcoScale, with products isolated by extraction or filtration after decantation
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
