scholarly journals Timeless Classics: on the Applicability of Bochvar's Three-Valued Logic B3 to the Description of an Absolute Configuration in Stereochemistry§ (Author's View)

INEOS OPEN ◽  
2021 ◽  
Vol 4 ◽  
Author(s):  
V. I. Sokolov ◽  
Keyword(s):  
Absolute Configuration ◽  
Chiral Center ◽  
The Absolute

t is shown that the absolute configuration of a chiral center can be successfully described in terms of Bochvar's three-valued logic.

scholarly journals The Assignment of the Absolute Configuration of C-22 Chiral Center in the Aglycones of Triterpene Glycosides from the Sea Cucumber Cladolabes schmeltzii and Chemical Transformations of Cladoloside C

2015 ◽  
Vol 10 (7) ◽  
pp. 1934578X1501000 ◽  
Author(s):  
Anatoly I. Kalinovsky ◽  
Alexandra S. Silchenko ◽  
Sergey A. Avilov ◽  
Vladimir I. Kalinin
Keyword(s):  
Absolute Configuration ◽  
Sea Cucumber ◽  
Triterpene Glycosides ◽  
Chiral Center ◽  
Biosynthetic Pathways ◽  
Chemical Transformations ◽  
Chemical Structures ◽  
Different Types ◽  
The Absolute ◽  
Chiral Centers

The absolute R-configuration of the C-22 chiral center in cladoloside C (1) and therefore in all related glycosides isolated from the sea cucumber Cladolabes schmeltzii has been assigned by Mosher‘s method. Some chemical transformations of the native glycoside 1 were carried out to apply this method. This resulted in the isolation and elucidation of chemical structures of progenin 2 and artefact aglycones 3 and 4, obtained from 1 and assignment of the absolute R-configuration of C-22 in the progenin 2. The coincidence of C-22 configurations in the studied compounds with those of the earlier known lanostane-type aglycone of frondoside C and holostane-type aglycone of cladoloside C (1) confirms the generic biosynthetic pathways to different types of sea cucumber glycoside aglycones. It suggests the same R-configuration of C-22 chiral centers in all the sea cucumber glycosides having C-22 functionalities.

A chiral switch: balancing between equilibrium and non-equilibrium states

2019 ◽  
Vol 55 (48) ◽  
pp. 6910-6913 ◽  
Author(s):  
Iaroslav Baglai ◽  
Michel Leeman ◽  
Bernard Kaptein ◽  
Richard M. Kellogg ◽  
Willem L. Noorduin
Keyword(s):  
Amino Acid ◽  
Absolute Configuration ◽  
Equilibrium States ◽  
Chiral Center ◽  
Equilibrium Conditions ◽  
The Absolute ◽  
Amino Acid Precursors ◽  
Non Equilibrium

Herein we introduce a “chiral switch” – a sequence of operations that alternate between equilibrium and non-equilibrium conditions to switch the absolute configuration of a chiral center. The generality and practical potential of the technique are demonstrated with three unnatural α-amino acid precursors.

Studies on Biologically Active Pteridines: III. The Absolute Configuration at the C-6 Chiral Center of Tetrahydrobiopterin Cofactor and Related Compounds1

1980 ◽  
Vol 87 (3) ◽  
pp. 951-957 ◽  
Author(s):  
Sadao MATSUURA ◽  
Takashi SUGIMOTO ◽  
Hiroyuki HASEGAWA ◽  
Shunsuke IMAIZUMI ◽  
Arata ICHIYAMA
Keyword(s):  
Absolute Configuration ◽  
Biologically Active ◽  
Chiral Center ◽  
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.

scholarly journals Rapid Organocatalytic Chirality Analysis of Amines, Amino Acids, Alcohols, Amino Alcohols and Diols with Achiral Iso(thio)cyanate Probes

2021 ◽  
Author(s):  
Eryn Nelson ◽  
Jeffrey S. S. K. Formen ◽  
Christian Wolf
Keyword(s):  
Amino Acids ◽  
Absolute Configuration ◽  
Rapid Determination ◽  
Amino Alcohols ◽  
Enantioselective Synthesis ◽  
Widespread Occurrence ◽  
Chiral Compounds ◽  
New Methods ◽  
The Absolute

The widespread occurrence and significance of chiral compounds does not only require new methods for their enantioselective synthesis but also efficient tools that allow rapid determination of the absolute configuration,...

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