Structure and absolute configuration of hydroxy-bis -dihydrofarinosin from Encelia farinosa

2016 ◽  
Vol 55 (6) ◽  
pp. 530-539 ◽  
Author(s):  
Alfredo R. Ortega ◽  
Naytzé Ortiz-Pastrana ◽  
Leovigildo Quijano ◽  
Elvia Becerra-Martínez ◽  
José O. Olmedo-Aguirre ◽  
...  
Keyword(s):  
Absolute Configuration ◽  
Encelia Farinosa

New rare atropisomers: structure elucidation, absolute configuration and antimicrobial activity

Planta Medica ◽  
2011 ◽  
Vol 77 (12) ◽  
Author(s):  
A Debbab ◽  
R Bara ◽  
A Pretsch ◽  
R Edrada Ebel ◽  
V Wray ◽  
...  
Keyword(s):  
Antimicrobial Activity ◽  
Absolute Configuration ◽  
Structure Elucidation

Influence of Absolute Configuration of Indanofan on Herbicidal Activity

2001 ◽  
Vol 26 (4) ◽  
pp. 383-384 ◽  
Author(s):  
Akemi HOSOKAWA ◽  
Osamu IKEDA ◽  
Chizuko SASAKI ◽  
Yasuko T. OSANO ◽  
Tetsuo JIKIHARA
Keyword(s):  
Absolute Configuration ◽  
Herbicidal Activity

Catalyst- and Silane- Controlled Enantioselective Hydrofunctionalization of Alkenes by Cobalt-Catalyzed Hydrogen Atom Transfer and Radical-Polar Crossover

2020 ◽  
Author(s):  
Kousuke Ebisawa ◽  
Kana Izumi ◽  
Yuka Ooka ◽  
Hiroaki Kato ◽  
Sayori Kanazawa ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Absolute Configuration ◽  
Kinetic Resolution ◽  
Hydrogen Atom Transfer ◽  
Biologically Active ◽  
Atom Transfer ◽  
High Concentration ◽  
Chain Reaction ◽  
Radical Chain ◽  
Radical Chain Reaction

Catalytic enantioselective synthesis of tetrahydrofurans, which are found in the structures of many biologically active natural products, via a transition-metal catalyzed-hydrogen atom transfer (TM-HAT) and radical-polar crossover (RPC) mechanism is described herein. Hydroalkoxylation of non-conjugated alkenes proceeded efficiently with excellent enantioselectivity (up to 94% ee) using a suitable chiral cobalt catalyst, <i>N</i>-fluoro-2,4,6-collidinium tetrafluoroborate, and diethylsilane. Surprisingly, absolute configuration of the product was highly dependent on the steric hindrance of the silane. Slow addition of the silane, the dioxygen effect in the solvent, thermal dependency, and DFT calculation results supported the unprecedented scenario of two competing selective mechanisms. For the less-hindered diethylsilane, a high concentration of diffused carbon-centered radicals invoked diastereoenrichment of an alkylcobalt(III) intermediate by a radical chain reaction, which eventually determined the absolute configuration of the product. On the other hand, a more hindered silane resulted in less opportunity for radical chain reaction, instead facilitating enantioselective kinetic resolution during the late-stage nucleophilic displacement of the alkylcobalt(IV) intermediate.

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