1,729,702 research outputs found
3-Amminoisotiazol diossidi come efficienti dienofili in reazioni di cicloaddizione di Diels Alder
No full text3-Amminoisotiazol diossidi come efficienti dienofili in reazioni di cicloaddizione di Diels AlderLe reazioni di Diels-Alder rappresentano uno dei mezzi più efficaci per la costruzione di sistemi carbociclici od eterociclici esatomici ed offrono la possibilità di realizzare processi sintetici stereocontrollati. Sulla base di questa considerazione e del nostro interesse nei confronti dei sistemi isotiazolici,1 abbiamo studiato le potenzialità del sistema 3-amminoisotiazol S-ossido in reazioni di Diels-Alder, valutando la sua efficienza come dienofilo e l’efficacia del gruppo sulfinilico come induttore di stereoselettività. Per la realizzazione delle cicloaddizioni sono state studiate metodologie eco-compatibili.2 In particolare, abbiamo utilizzato due approcci: 1) eliminazione del solvente; 2) sostituzione con solventi a basso impatto ambientale.
Il gruppo SO induce la formazione esclusiva dell’addotto endo e, a seconda delle condizioni adottate, è possibile osservare una variazione nel rapporto percentuale tra i due addotti endo sin ed endo anti.
1. F. Clerici, “Thiazole and Thiadiazole S-oxides” Advances in Heterocyclic Chemistry, A. R. Katritzky ed., Pergamon Press, vol. 83, 72-116, 2002
2.G.Imperato, B. Koenig, A. Sala. Sweet Solutions – Low melting mixtures of carbohydrates and inorganic salts as new media for organic reaction, German, Degussa, January 200
I valdesi alpini visti da due codici parigini (Bibliothèque Nationale, ms. Lat. 3375, I-II)
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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
Neutrophils, endothelial cells, and cysteinyl leukotrienes: a new approach to neutrophil-dependent inflammation?
No full textCysteinyl leukotrienes (cys-LT) have been historically involved with the pathogenesis of asthma, and cys-LT receptor antagonists and synthesis inhibitors are currently in use for the therapy of this disease. Nevertheless cys-LT possess very potent proinflammatory activities and may play a significant role in inflammatory processes other than asthma. Recent evidences obtained in our laboratory, as well as in others, show that unexpected, biologically significant amounts of cys-LT are formed upon cell-cell cooperation between neutrophils and endothelial cells, resulting from transfer of the synthesis intermediate leukotriene A4 from neutrophils to endothelial cells. Cys-LT formed upon neutrophil adhesion to endothelial cells may contribute to the alterations of microvasculature associated with the inflammatory response. In particular, nonsteroidal anti-inflammatory drug (NSAIDs)-induced neutrophil adhesion to gastric wall microvessels may contribute to the gastric damage associated to the use of NSAIDs. In agreement with this hypothesis, dual 5-LOX/COX inhibitors are characterized by reduced gastric damage when compared to nonspecific COX-inhibitors. Evidence provide support for the involvement of cys-LT in neutrophil-dependent inflammatory responses and suggest new potential application of 5-LO inhibition in anti-inflammatory pharmacological treatment
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