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Tropos ligand for the asymmetric addition of phenylboronic acid to enones
No full textTROPOS LIGAND FOR THE ASYMMETRIC ADDITION OF PHENYLBORONIC ACID TO ENONES
P. Scafato, F. Caprioli, L. Pisani, C. Rosini
Dipartimento di Chimica, Università degli Studi della Basilicata, via N. Sauro, 85; Potenza.
e-mail: [email protected]
The asymmetric conjugate addition of arylboronic acids to activated olefins is nowadays an efficient method for the stereoselective construction of C(sp2)-C(sp3) bonds, given the large spectrum of substrates which can be used and the availability of many different chiral ligands.1 In this context, phosphoramidites certainly constitute a class of versatile and easily tunable ligands.2
We report herein the asymmetric addition of phenylboronic acid to different cycloalkenones with both the tropos phosphoramidite (S)-L1 and the non tropos (S)-L2 ligand. Different enantioselectivities have been obtained, mainly depending on the ring size of the substrates, with (S)-L1 affording higher e.e. values than (S)-L2. These results can been explained reasoning that, only for the tropos phosphoramidite, a “chiral pocket” is formed when the ligand links to the metal atom.
References:
1) (a) Fagnou, K.; Lautens, M. Chem. Rev. 2003, 103, 169-196; (b) Hayashi, T.; Yamasaki, K. Chem. Rev. 2003, 103, 2829-2844.
2) a) Boiteau, J.-M.; Imbos, R.; Minnaard, A. J.; Feringa, B. L. Org. Lett. 2003, 5, 681-684.
3) P. Scafato, G. Cunsolo, S. Labano, C. Rosini, Tetrahedron 2004, 60, 8801-8806
Türkçelik, Evrim, Un noble italiano en la corte otomana: Cigalazade y el Mediterráneo (1591-1606), Valencia, Albatros Ediciones, 2019, 201 págs., ISBN: 978-84-7274-364-9.
No full textSuccessful Treatment With Vedolizumab in a Patient with Chronic Refractory Pouchitis and Primary Sclerosing Cholangitis
No full textAsymmetric conjugate addition of arylboronic acids to enones mediated by rhodium/phosphoramidite complex
No full textAsymmetric conjugate addition of arylboronic acids to enones mediated by rhodium/phosphoramidite complex
Patrizia Scafato, Francesca Caprioli, Carlo Rosini
Dipartimento di Chimica, Università degli Studi della Basilicata, via N. Sauro, 85; Potenza. [email protected]
The asymmetric rhodium-catalyzed conjugate addition of aryl boronic acids nowadays is the method of choice for the stereoselective introduction of an aryl group in the β position of activated olefins.1
The catalytic efficiency of phosphoramidite L* has been tested on such a reaction with different enones, providing high yields and enantioselectivities (up to 96% e.e.) dependent on the nature of the carbonyl compound. Furthermore, preliminary investigations on the asymmetric addition of phenylboronic acid to chromones, substrates never utilized for this reaction, are reported. The results obtained indicate that also this reaction can occur with high enantioselectivity. Moreover, this synthetic approach could represent a new convenient access to chiral flavanones,2 an important class of natural and synthetic products which possess an impressive and varied array of biological and pharmacological properties.
1. (a) Fagnou, K.; Lautens, M. Chem. Rev. 2003, 103, 169-196; (b) Hayashi, T.; Yamasaki, K. Chem. Rev. 2003, 103, 2829-2844; (c) Christoffers, J.; Koripelly, G.; Rosiak, A.; Rössle, M. Synthesis 2007, 1279-1300. 2. Moorty, N. S. H. N.; Singh, R. J.; Sing, H. P.; Gupta, S. D. Chem. Pharm. Bull. 2006, 54, 1384-1390
Preparation of biologically active 3-arylketones by asymmetric conjugate addition of arylboronic acid to the corresponding α,β-unsaturated enones
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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
Pietre che camminano: il colore e il prestigio dei marmi antichi nell’Ottocento roma
No full textOne of the peculiarities of the Papal architecture of the 19th century in Rome
is the use of stones and coloured marbles, often for reuse, according to the taste and the
building practice of the great Renaissance and Baroque tradition. The use of ancient, prized
and sometimes rare stones attributed to the architectures a strong prestige and a symbolic
charge, binding them ideally to the immortal values of Classicism and the great Christian
architecture of imperial matrix.
Furthermore, the retrieval, transport and processing of the stones, intended for these architectures,
represented steps of a flourishing and profitable economic activity in the Papal
State; steps all of which had a direct impact on the town, its economic organization and
urban structure.
The Confession of the Basilica of Santa Maria Maggiore in Rome, made between 1861 and
1864, represents in its architectural and chromatic syntax (geometry of the intarsia, colours
and patterns of the stones, their distribution) the result of a conceptual process and of a
coordinated activity of specialized workers: a world that closes its long life cycle at the dawn
of the 20th Century
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
A novel method for the culture and polarized stimulation of human intestinal mucosa explants
No full textFew models currently exist to realistically simulate the complex human intestine's micro-environment, where a variety of interactions take place. Proper homeostasis directly depends on these interactions, as they shape an entire immunological response inducing tolerance against food antigens while at the same time mounting effective immune responses against pathogenic microbes accidentally ingested with food. Intestinal homeostasis is preserved also through various complex interactions between the microbiota (including food-associated beneficial bacterial strains) and the host, that regulate the attachment/degradation of mucus, the production of antimicrobial peptides by the epithelial barrier, and the "education" of epithelial cells' that controls the tolerogenic or immunogenic phenotype of unique, gut-resident lymphoid cells' populations. These interactions have been so far very difficult to reproduce with in vitro assays using either cultured cell lines or peripheral blood mononuclear cells. In addition, mouse models differ substantially in components of the intestinal mucosa (mucus layer organization, commensal bacteria community) with respect to the human gut. Thus, studies of a variety of treatments to be brought in the clinics for important stress-related or pathological conditions such as irritable bowel syndrome, inflammatory bowel disease or colorectal cancer have been difficult to carry out. To address these issues, we developed a novel system that enables us to stimulate explants of human intestinal mucosa that retain their in situ conditioning by the host microbiota and immune response, in a polarized fashion. Polarized apical stimulation is of great importance for the outcome of the elicited immune response. It has been repeatedly shown that the same stimuli can produce completely different responses when they bypass the apical face of the intestinal epithelium, stimulating epithelial cells basolaterally or coming into direct contact with lamina propria components, switching the phenotype from tolerogenic to immunogenic and causing unnecessary and excessive inflammation in the area. We achieved polarized stimulation by gluing a cave cylinder which delimited the area of stimulation on the apical face of the mucosa as will be described in the protocol. We used this model to examine, among others, differential effects of three different Lactobacilli strains. We show that this model system is very powerful to assess the immunomodulatory properties of probiotics in healthy and disease conditions
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