Determination by Neutron and X-Ray Diffraction of the Absolute Configuration of an Enzymatically Formed α-Monodeuterioglycolate1

1965 ◽  
Vol 87 (8) ◽  
pp. 1802-1804 ◽  
Author(s):  
Carroll K. Johnson ◽  
Eric J. Gabe ◽  
Max R. Taylor ◽  
Irwin A. Rose
Keyword(s):  
Absolute Configuration ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Absolute

Alkaloids of Rauvolfia salicifolia GRISEB species

1982 ◽  
Vol 47 (11) ◽  
pp. 2912-2921 ◽  
Author(s):  
Patricia Sierra ◽  
Ladislav Novotný ◽  
Zdeněk Samek ◽  
Miloš Buděšínský ◽  
Ladislav Dolejš ◽  
...  
Keyword(s):  
Absolute Configuration ◽  
Cd Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Absolute

From the endemic Cuban species Rauvolfia salicifolia GRISEB nine alkaloids were isolated of which the following seven had been already described: (+)-ajmalidine (I), (-)-reserpiline (II), (-)-isoreserpiline (III), (-)-isocarapanaubine (IV), (-)-ajmalicine (V), (+)-vellosimine (VI), and (+)-yohimbine (VII). The structure of (-)-raucubaine (VIII) had been previously determined by X-ray diffraction and the structure of the alkaloid (-)-raucubainine (IX) was suggested on the basis of its conversion to (-)-raucubaine (VIII). The absolute configuration of (-)-raucubaine and (-)-raucubainine was elucidated by CD spectroscopy.

scholarly journals Absolute Configuration of Cembrane Diterpenoids from Bursera multijuga

2014 ◽  
Vol 9 (9) ◽  
pp. 1934578X1400900 ◽  
Author(s):  
Juan D. Hernández-Hernández ◽  
Hugo A. García-Gutiérrez ◽  
Luisa U. Román-Marín ◽  
Yunuen I. Torres-Blanco ◽  
Carlos M. Cerda-García-Rojas ◽  
...  
Keyword(s):  
Molecular Modeling ◽  
Absolute Configuration ◽  
2D Nmr ◽  
Vibrational Circular Dichroism ◽  
Conformational Preference ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Absolute ◽  
First Time ◽  
Good Agreement

The stems of Bursera multijuga afforded (-)-(1 S,3 E,7 R,8 R,11 E)-7,8-epoxycembra-3,11-dien-1-ol (1) and its acetate 2, together with cembrene A (3), nephthenol (4), and cembrenol (5). The structures of 1 and 2 were elucidated by 1D and 2D NMR, HRESIMS, and X-ray diffraction. The conformational preference of flexible 1 was studied by molecular modeling at the DFT B3LYP/DGDZVP level of theory. Good agreement between calculated and experimental vibrational circular dichroism curves established the absolute configuration of 1. This is the first time that cembrane derivatives have been isolated from the genus Bursera.

Structure of isosilerolide, relative and absolute configuration of silerolide and lasolide - Sesquiterpenic lactones of new stereoisomeric type of eudesmanolides

1986 ◽  
Vol 51 (4) ◽  
pp. 903-929 ◽  
Author(s):  
Miroslav Holub ◽  
Miloš Buděšínský ◽  
Zdenka Smítalová ◽  
David Šaman ◽  
Urszula Rychłewska
Keyword(s):  
Absolute Configuration ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr ◽  
Nmr Data ◽  
Chemical Correlation ◽  
The Absolute

On the basis of spectroscopic, particularly 1H NMR data, isosilerolide was assigned structure I, including the absolute configuration. The structure was confirmed by X-ray diffraction. Isosilerolide represents a new stereoisomeric type of natural eudesmanolides, characterized as 5βH, 6αH, 7αH, 10αCH3-eudesman-6,12-olide. As shown by the chemical correlation of isosilerolide (I) with silerolide (III) and lasolide (X), the latter two natural lactones belong to this stereoisomeric group of eudesmanolides. Analysis of models and 1H NMR data shows that structures of some eudesman-6,12-olides, published by other authors, should be corrected.

Stereochemistry at carbon upon protonolysis of a late transition metal-alkyl bond: a reaction of relevance to catalytic enantioselective hydrogenation of olefins

2001 ◽  
Vol 79 (5-6) ◽  
pp. 1019-1025 ◽  
Author(s):  
Jason A Wiles ◽  
Steven H Bergens ◽  
Victor G Young, Jr
Keyword(s):  
Absolute Configuration ◽  
Room Temperature ◽  
Enantioselective Hydrogenation ◽  
Insertion Reaction ◽  
X Ray Diffraction ◽  
Olefinic Carbon ◽  
X Ray ◽  
The Absolute ◽  
Hydride Elimination ◽  
Late Transition

Reaction of [Ru((R)-BINAP)(H)(MeCN)n(acetone)3–n](BF4) (where n = 0–3) (2) with 1 equiv of the olefin substrate methyl α-acetamidoacrylate (MAA) in acetone at room temperature immediately generated a mixture (72:28) of two diastereomers of the complex [Ru((R)-BINAP)(MeCN)(MAA(H))](BF4) (3). The olefin–hydride insertion reaction between 2 and MAA to generate 3 was regioselective, with transfer of the hydride to the β-olefinic carbon and transfer of ruthenium to the α-carbon in both diastereomers of 3. The two diastereomers of 3 differ by the absolute configuration at the α-carbon of MAA(H) ((SCα)-3 and (RCα)-3). The absolute configuration of the major ((SCα)-3) diastereomer was determined by X-ray diffraction in conjunction with NMR spectroscopic data. Protonolysis of the ruthenium–carbon bond in 3 and in the methyl α-acetamidocinnamate (MAC) analog ([Ru((R)-BINAP)(MeCN)((S)- MAC(H))](BF4) ((SCα)-4)) by addition of 2 equiv HBF4·Et2O in CH2Cl2 at room temperature was not stereospecific and did not occur with β-hydride elimination from the methyl or benzyl groups.Key words: ruthenium, BINAP, enantioselective, hydrogenation, catalysis.

Synthese und absolute Konfiguration kettenverzweigter, Cimetidin-analoger Thioether / Synthesis and Absolute Configuration of Chain Branched Cimetidine Analogous Thioethers

1987 ◽  
Vol 42 (3) ◽  
pp. 348-354 ◽  
Author(s):  
Sigurd Elza ◽  
Martin Dräger ◽  
Walter Schunack
Keyword(s):  
Amino Acids ◽  
Absolute Configuration ◽  
Enantiomeric Excess ◽  
Building Blocks ◽  
Anomalous Dispersion ◽  
X Ray Diffraction ◽  
Enantiomerically Pure ◽  
X Ray ◽  
The Absolute ◽  
Branched Compound

Chain branched Cimetidine analogous thioethers, promising building blocks for the preparation of H2-histaminergic compounds, were synthetized from chiral aminoalkanethiols. Enantiomerically pure amino acids or aminoalcohols were used as starting materials. In one case, a resolution via neutral and acid di-O-(4-toluoyl)tartrates was achieved in good yields and satisfying enantiomeric excess. The absolute configuration of an ethyl branched compound was determined using X-ray diffraction and anomalous dispersion

Euryachins A and B, a new type of diterpenoids from Eurya chinensis with potent NO production inhibitory activity

RSC Advances ◽  
2016 ◽  
Vol 6 (89) ◽  
pp. 85958-85961 ◽  
Author(s):  
Jia-Ling Song ◽  
Yao Yuan ◽  
Hai-Bo Tan ◽  
Jie-Wei Wu ◽  
Ri-Ming Huang ◽  
...  
Keyword(s):  
Single Crystal ◽  
Absolute Configuration ◽  
Inhibitory Activity ◽  
No Production ◽  
X Ray Diffraction ◽  
X Ray ◽  
New Type ◽  
The Absolute

Euryachins A (1) and B (2), new typediterpenoid euryamanes, were isolated from the branches of Eurya chinensis. The absolute configuration of 1 was determined by single-crystal X-ray diffraction. Both 1 and 2 exhibited significant NO production inhibitory activity.

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