1,721,007 research outputs found
Nuovi e semplici metodi di sintesi regioselettiva di 1,5- e di 1,2-diaril-1H-imidazoli
No full textGli 1,5-diaril- e gli 1,2-diaril-1H-imidazoli, 1 and 2, rappresentano due classi di derivati eterociclici che comprendono inibitori selettivi della cicloossigenasi-2 (COX-2), sostanze con attività anti-tubulinica ed analoghi Z-ristretti della combretastatina A-4 (CA-4). Quest’ultimo composto, isolato dal salice sudafricano Combretum caffrum Kuntze, è capace di inibire sia la polimerizzazione della tubulina che il binding della colchicina alla tubulina ed è inoltre potentemente e selettivamente citotossico nei confronti della vascolatura tumorale. Nonostante l’indubbia rilevanza di queste due classi di composti, a nostra conoscenza non ne sono stati sinora riportati metodi generali e semplici di preparazione.
Proseguendo i nostri studi sulla sintesi e la valutazione dell’attività citotossica di analoghi configurazionalmente stabili della CA-4,1 recentemente abbiamo trovato che una varietà di 1,5-diaril-1H-imidazoli 1 possono essere sintetizzati regioselettivamente e con rese moderate mediante reazione di coupling diretto di 1-aril-1H-imidazoli 3 con 2 equiv di alogenuri arilici 4 in DMF a 140 °C in presenza di CsF e di un precursore catalitico costituito da una miscela di Pd(OAc)2 e di AsPh3 (eq. 1).Abbiamo inoltre osservato che per reazione di 1-aril-1H-imidazoli variamente sostituiti 5 con 2 equiv di 4 in DMF a 140 °C in presenza di CsF, CuI e di una quantità catalitica di Pd(OAc)2 si ottengono 1,2-diaril-1H-imidazoli 2 con elevata selettività e rese da moderate ad alte (eq. 2).Tali reazioni Pd-catalizzate, di cui verranno anche discussi i plausibili meccanismi, sono state da noi utilizzate nella sintesi di derivati imidazolici che possiedono attività citotossica nei confronti di linee di cellule tumorali umane o che sono inibitori selettivi della COX-2
Regioselective synthesis of 1,5- and 1,2-diaryl-1H-imidazoles by Pd- or Pd/Cu-mediated direct arylation of 1-aryl-1H-imidazoles
No full textA variety of 1,5-diaryl-1H-imidazoles, e.g., I, have been regioselectively synthesized by direct coupling of 1-aryl-1H-imidazoles with aryl iodides or bromides in DMF in the presence of CsF as the base and a catalyst precursor consisting of a mixt. of Pd(OAc)2 and AsPh3. The data obtained support a reaction mechanism involving an electrophilic attack of an arylpalladium(II) halide species onto the imidazole ring. Interestingly, some of the imidazole derivs. have been found to exhibit significant cytotoxic activity against human tumor cell lines
Caratterizzazione NMR e Analisi Statistica di Oli di Oliva DOP Veneti
No full textHigh-field 1H Nuclear Magnetic Resonance (NMR) was used to analyze 14 extra virgin olive oils coming from two PDO (Protected Denomination of Origin) areas of Veneto. The methodology previously applied to olive oils coming from Mediterranean areas has been applied to olive oils coming from area with different pedoclimatic conditions. Selected 1H NMR resonance were submitted to two different statistical methods namely Analysis of Variance and Principal Component Analysis. Extra virgin olive oils from the same geographical area were clearly grouped, indicating that multivariate statistical analysis applied to 1H NMR data can be used to check the Protected Denomination of Origin. Preliminary results show that it is also possible to distinguish olive oils coming from different micro-areas of the same DOP
Sintesi selettiva di b4-aril-, 4-alchenil- e 4-(1-alcjhinil)-%H-furan-2-oni racemi mediante reazioni a cascata promosse da palladio coinvolgenti acidi 3-inolici ed alogenuri arilici, alchenilici od alchinilici
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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
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
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