1,720,985 research outputs found
Catalytic Asymmetric Synthesis of 3,4-Disubstituted Cyclohexadiene Carbaldehydes: Formal Total Synthesis of Cyclobakuchiols A and C
No full textThe
first catalytic approach for the asymmetric synthesis of 3,4-disubstituted
cyclohexadiene carbaldehydes through an inverse-electron-demand Diels–Alder
reaction is described. A variety of arylacetaldehydes and α,β,γ,δ-unsaturated
aldehydes are tested under the mild reaction conditions catalyzed
by l-proline to obtain the trans diastereomeric
products with good yields and high enantioselectivities. The scope
of this methodology is further extended to the asymmetric synthesis
3,4-disubstituted cyclohexane carbaldehydes and their derivatives.
The practicality of this method is demonstrated by the gram-scale
synthesis. This methodology is successfully applied for the formal
total synthesis of cyclobakuchiol A, an antipyretic and anti-inflammatory
agent, and cyclobakuchiol C
Enantioselective Total Synthesis of Potent 9β-11-Hydroxyhexahydrocannabinol
No full textThe first total synthesis of potent cannabinoid, 9β-11-hydroxyhexahydrocannabinol,
is achieved through a proline-catalyzed inverse-electron-demand Diels–Alder
reaction. Using this asymmetric catalysis, the cyclohexane ring is
constructed with two chiral centers as a single diastereomer with
97% ee. The creation of the third chiral center and benzopyran ring
is demonstrated with the elegant synthetic strategies. This mild and
efficient synthetic methodology provides a new route for the asymmetric
synthesis of the other potent hexahydrocannabinols
Asymmetric synthesis of α-methoxyarylacetic acid derivatives
No full textStereoselective synthesis of a series of 2-aryl-2-methoxyethanols was achieved from inexpensive chiral pool tartaric acid employing a diastereoselective reduction of a symmetrical 1,4-diaryldiketone as the key step. 2-Aryl-2-methoxyethanols were enantioselectively prepared in 80–90% yield
Stereoselective syntheses of γ-alkyl (aryl)-α,β-dihydroxy-γ-butyrolactones and naturally occurring lipid guggultetrol
No full textγ-Oxo-butyramides derived from tartaric acid serve as excellent precursors for the synthesis of γ-alkyl (aryl)-α,β-dihydroxy-γ-butyrolactones and for the synthesis of tetrols containing three contiguous stereogenic centres. The methodology presented here is general for the synthesis of γ-alkyl (aryl)-α,β-dihydroxy-γ-butyrolactones. Utility of the chiral building block was demonstrated by the synthesis of naturally occurring lipid guggultetrol
Front Cover: Highly Regio- and Enantioselective γ-Alkylation of Linear α,β-Unsaturated Aldehydes (Eur. J. Org. Chem. 29/2017)
No full textStereoselective syntheses of \gamma-alkyl (aryl)-, -dihydroxy-\gamma-butyrolactones and naturally occurring lipid guggultetrol
No full text\gamma-Oxo-butyramides derived from tartaric acid serve as excellent precursors for the synthesis of \gamma-alkyl (aryl)-, -dihydroxy-\gamma- butyrolactones and for the synthesis of tetrols containing three contiguous stereogenic centres. The methodology presented here is general for the synthesis of \gamma-alkyl (aryl)-, -dihydroxy-\gamma-butyrolactones.Utility of the chiral building block was demonstrated by the synthesis of naturally occurring lipid guggultetrol
Asymmetric synthesis of \alpha-methoxyarylacetic acid derivatives
No full textStereoselective synthesis of a series of 2-aryl-2-methoxyethanols was achieved from inexpensive chiral pool tartaric acid employing a diastereoselective reduction of a symmetrical 1,4-diaryldiketone as the key step. 2-Aryl-2-methoxyethanols were enantioselectively prepared in 80-90% yield
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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