1,721,050 research outputs found
Synthesis of integrin inhibitors
No full textA series of azabicycloalkane amino acids, which can be regarded as conformationally restricted substitutes
for Phe-Pro dipeptide units have been synthesized. These bicyclic scaffolds are used as intermediates in
the synthesis of biologically active cyclic peptidomimetic compounds comprising the sequence RGD (Arg-
Gly-Asp). The most active cyclopentapeptide of the series was 1-RGD, which shows biological activity as
selective ®v ̄3 and ®v ̄5 integrin inhibitor. The high affinity of 1-RGD towards ®v ̄3 and ®v ̄5 receptors,
involved in tumor angiogenesis, led us to functionalize the azabicycloalkane scaffold with a suitable linker
to which bioactive compounds could be appended; thus it would be possible to perform selective delivery
of therapeutics and imaging agents to the tumor vasculature. Our work was focused on the synthesis of
lactams 2a, 2b or 3, endowed with a vinyl moiety on a 7,5-fused 1-aza-2-oxo-bicycloalkane. Two different
approaches exploiting as a key step either a Ring Closing Enyne Metahesis (RCEYM) or an intramolecular
Sakurai reaction, have been studied
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
Novel stereoselective syntheses of (2E,4E)-4-(4,4-dimethylpent-2-ynylidene)-N1,N5-dimethyl-N1,N5-bis(naphthalen-1-ylmethyl)pent-2-ene-1,5-diamine
No full textWe report two different synthetic approaches for the stereoselective synthesis of (2E,4E)-4-(4,4-dimethylpent-
2-ynylidene)-N1,N5-dimethyl-N1,N5-bis(naphthalen-1-ylmethyl)pent-2-ene-1,5-diamine 1, an
important impurity-reference standard for the chemical characterization of terbinafine. The diamine 1
was obtained in only six steps with a good overall yield starting from commercially available glutaconic
acid
Synthesis of bicyclolactam (Phe-Pro)-mimetic scaffold using an intramolecular Hosomi-Sakurai reaction
No full textStereoselective Pd-catalyzed synthesis of quaternary a-C-D-mannosyl-(S)-amino acids
No full textIn this paper, we report the stereoselective synthesis of α-d-C-mannosyl-(S)-amino acids exploiting, as a key step, an allylic alkylation of glycal-derived π-allyl Pd(II) intermediates, prepared by oxidative addition of Pd(0) species to 2,3-unsaturated pyranosides (pseudoglycals). The reaction of 4,6-di-O-acetyl α-pseudoglucal carbonate 10a with racemic alanine-, valine-, and phenylalanine-derived azlactones gave the corresponding (4S)-4-α-d-C-mannosyl-2-phenyloxazol-5(4H)-ones as the major diastereoisomers in high yields. The final α-d-C-mannosyl-(S)-amino acids were obtained in a few steps comprising highly diastereoselective dihydroxylation of the glucal derivative double bond followed by the one-pot hydrolysis of the benzamido and acetate protecting groups. Main features of this method are the conciseness of the synthetic sequence, the high diastereoselection of the allylic alkylation step, the use of racemic α-amino acids as starting material, and the good overall yields
New fast and practical method for the enantioselective synthesis of α-vinyl, α-alkyl quaternary α-amino acids
No full textWe describe a fast and practical enantioselective synthesis of (S)-N-Cbz-a-vinyl, phenylalanine, suitable for the preparation of
different N-Cbz-a-vinyl aminoacids of both configurations. The new protocol exploits a Wittig reaction on highly enantiomeric enriched
N-Cbz-a-formyl-a-alkyl amino esters, readily accessible from (L)-serine through a stereoselective alkylation of Seebach’s oxazolidine,
carried out with a significant improvement of the previously reported method. The synthetic scheme is suitable for gram scale preparation
of the desired product with a 94% e
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
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