Kinetic Resolution in a Bridgehead Lithiation Mediated by a Chiral Bis-lithium Amide:  Assignment of the Absolute Configuration of Clusianone

2007 ◽  
Vol 72 (11) ◽  
pp. 4265-4267 ◽  
Author(s):  
Vincent Rodeschini ◽  
Nigel S. Simpkins ◽  
Claire Wilson
Keyword(s):  
Absolute Configuration ◽  
Kinetic Resolution ◽  
Lithium Amide ◽  
The Absolute

Studies of Australian Soft Corals. XLIII. The Structure Elucidation of a New Diterpene From Alcyonium molle

1989 ◽  
Vol 42 (5) ◽  
pp. 665 ◽  
Author(s):  
BF Bowden ◽  
JC Coll ◽  
MC Dai
Keyword(s):  
Absolute Configuration ◽  
High Field ◽  
Structure Elucidation ◽  
Kinetic Resolution ◽  
Soft Coral ◽  
Soft Corals ◽  
Resolution Method ◽  
The Absolute ◽  
First Time

The isolation of a new cladiellin based diterpene (6), (1S,2R,3S,4R,SR,6S,8E,11S,12R,13S,14S)-3-acetoxy-2,12-dibutanoyloxycladiell-8-ene-4,11-diol is reported from the soft coral Alcyonium molle (Octocorallia, Alcyonacea, Alcyoniidae). The structure was deduced by high-field n.m.r. spectroscopy including 13C-lH shift correlated 2D n.m.r. experiments and n.O.e. measurements. The absolute configuration was based on the kinetic resolution method of Horeau. This highly derivatized diterpene (6) is the first alcyonacean derived metabolite to possess hydroxy functionalities protected as butyrate esters, although this feature is relatively common among gorgonacean metabolites. Gorgosterol (7), which cooccurs with (6) in A. molle was identified and its 13C n.m.r. spectrum reported for the first time.

Regioselectivity and stereoselectivity in the reaction of cis-1,2,2-Trimethylcyclopentane-1,3-dicarboxylic anhydride (cis-camphoric anhydride) with chiral primary amines

1981 ◽  
Vol 34 (3) ◽  
pp. 665 ◽  
Author(s):  
KH Bell
Keyword(s):  
Carbonyl Group ◽  
Absolute Configuration ◽  
Kinetic Resolution ◽  
Optically Active ◽  
Primary Amines ◽  
The Absolute

The reaction between primary amines and cis-1,2,2 trimethylcyclopentane-1,3-dicarboxylic anhydride (3) has been shown to be regioselective for the less hindered carbonyl group. Kinetic resolution was observed when racemic primary amines and the (1R,3S) anhydride (3) were used. Similar stereoselectivity was found in the alternative reaction between racemic (3) and optically active primary amines. In both cases, the absolute configuration of the more reactive enantiomeric amine or anhydride could be correlated with a model (7). The use of (3) is recommended for the prediction of the absolute configurations of racemic and optically active primary amines.

scholarly journals Synthesis, lipase catalyzed kinetic resolution, and determination of the absolute configuration of enantiomers of the Morita-Baylis-Hillman adduct 3-hydroxy-2-methylenebutanenitrile

ARKIVOC ◽  
2016 ◽  
Vol 2017 (2) ◽  
pp. 313-323 ◽  
Author(s):  
Daniel J. Strub ◽  
Agata Garboś ◽  
Stanisław Lochyński
Keyword(s):  
Absolute Configuration ◽  
Kinetic Resolution ◽  
The Absolute

Kinetic Resolution in the Reaction of (2R,3R)-2,3-Diacetoxy- and (2R,3R)-2,3-Dibenzoyloxy-succinic Anhydrides with Racemic Alcohols

1979 ◽  
Vol 32 (1) ◽  
pp. 65 ◽  
Author(s):  
KH Bell
Keyword(s):  
Absolute Configuration ◽  
Kinetic Resolution ◽  
The Absolute

The stereoselectivity in the reaction of various racemic alcohols with (2R,3R)-2,3-diacetoxy-and (2R,3R)-2,3-dibenzoyloxy-succinic anhydrides has been studied. Kinetic resolution values ranged up to 48%. A correlation between the absolute configuration of the more reactive enantiomeric alcohol with that of the chiral anhydride has been obtained. Attempted regeneration of the alcohols from the derived half-esters in the above reaction leads to partial racemization.

Microwave assisted glycosylation for determining the absolute configuration of carbohydrates in plant glycosides

Planta Medica ◽  
2012 ◽  
Vol 78 (11) ◽  
Author(s):  
KP Manfredi ◽  
H Frosch
Keyword(s):  
Absolute Configuration ◽  
Microwave Assisted ◽  
The Absolute

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.

Determination of the absolute configuration of natural products

2014 ◽  
Vol 11 (3) ◽  
pp. 193-198 ◽  
Author(s):  
Ling-Yi KONG ◽  
Peng WANG
Keyword(s):  
Natural Products ◽  
Absolute Configuration ◽  
The Absolute

Evaluation of Different Synthetic Routes to (2R,3R)-3-Hydroxymethyl-2-(4-hydroxy- 3-methoxyphenyl)-1,4-Benzodioxane-6-Carbaldehyde

2020 ◽  
Vol 23 (26) ◽  
pp. 2960-2968
Author(s):  
Renáta Kertiné Ferenczi ◽  
Tünde-Zita Illyés ◽  
Sándor Balázs Király ◽  
Gyula Hoffka ◽  
László Szilágyi ◽  
...  
Keyword(s):  
Absolute Configuration ◽  
Stereoselective Synthesis ◽  
Cotton Effect ◽  
Enantioselective Synthesis ◽  
Aryl Group ◽  
Target Molecule ◽  
Synthetic Routes ◽  
The Absolute

The reported enantioselective synthesis for the preparation of (+)-(2R,3R)-2-(4- hydroxy-3-methoxyphenyl)-3-hydroxymethyl-1,4-benzodioxane-6-carbaldehyde, precursor for the stereoselective synthesis of bioactive flavanolignans, could not be reproduced. Thus, the target molecule was prepared via the synthesis and separation of diastereomeric O-glucosides. TDDFT-ECD calculations and the 1,4-benzodioxane helicity rule were utilized to determine the absolute configuration. ECD calculations also confirmed that the 1Lb Cotton effect is governed by the helicity of the heteroring, while the higher-energy ECD transitions reflect mainly the orientation of the equatorial C-2 aryl group.

Absolute configuration at C(20) of the derivatives of 21-nor-5α-cholane-20,24-diol

1980 ◽  
Vol 45 (9) ◽  
pp. 2443-2451
Author(s):  
Vladimír Pouzar ◽  
Miroslav Havel
Keyword(s):  
Absolute Configuration ◽  
Side Chain ◽  
Chemical Correlation ◽  
The Absolute ◽  
Derivatives Of

Derivatives of 21-nor-5α-cholane-20,24-diol XI and XIX were prepared by stepwise construction of the side-chain in the position 17β. Their absolute configuration at C(20) was determined on the basis of chemical correlation with the derivatives of 21-nor-5α-cholan-20-ol, XVI and XXIV. The absolute configuration of alcohols XVI and XXIV was determined from the ratio of the yields in which they are formed during the reduction of ketone X and using the benzoate rule. To compounds XI-XVIII the configuration 20R and to compounds XIX-XXVI the configuration 20S has been assigned.

Absolute Stereochemistry of (-)-Wieland-Miescher Ketone as Established by the X-ray Crystallographic and CD Exciton Chirality Methods

1992 ◽  
Vol 57 (7) ◽  
pp. 1459-1465 ◽  
Author(s):  
Nobuyuki Harada ◽  
Tatsuo Sugioka ◽  
Hisashi Uda ◽  
Takeo Kuriki
Keyword(s):  
Structure Analysis ◽  
Absolute Configuration ◽  
X Ray ◽  
The Absolute ◽  
Absolute Stereochemistry

The 8aR absolute stereochemistry of Wieland-Miescher ketone (-)-I was established by the X-ray structure analysis of its bis(4-bromobenzoate) derivatives (1R,6R,8aR)-(+)-IV and (1R,6S,8aR)-(-)-V. The absolute configuration of (-)-I was corroborated further by the application of the CD exciton chirality method to bis(4-bromobenzoates) (+)-IV and (-)-V.

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