Absolute configuration of the alkaloid cularine: an X-ray structure determination

1972 ◽  
pp. 1072b ◽  
Author(s):  
T. Kametani ◽  
T. Honda ◽  
H. Shimanouchi ◽  
Y. Sasada
Keyword(s):  
Absolute Configuration ◽  
Structure Determination ◽  
X Ray

Étude conformationnelle de cétopipérazines: (I) 3R-méthyl-6-carbéthoxy-2 oxopipérazine, (II) 3R-[p-hydroxybenzyl]-6-carbéthoxy-2 oxopipérazine: I, II en solution et structure cristalline de II

1987 ◽  
Vol 65 (6) ◽  
pp. 1308-1312 ◽  
Author(s):  
André Michel ◽  
Guy Evrard ◽  
B. Norberg
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Absolute Configuration ◽  
Structure Determination ◽  
Opiate Receptor ◽  
Receptor Level ◽  
X Ray ◽  
Diastereomeric Mixture ◽  
The Absolute

The synthesis of the title compounds has been described recently. It was anticipated that the product would be a diastereomeric mixture. Surprisingly, only one isomer was obtained. The present work is an attempt to find the conformationnal properties accounting for those observations. X-ray structure determination of 3R-[p-hydroxybenzyl]-6-carbethoxy-2-oxopiperazine shows that the molecule adopts a folded conformation and that the absolute configuration at C6 is [R]. Investigation in solution using 1H nuclear magnetic resonance shows the existence of three conformers and discusses the relative populations. Those findings are also relevant in terms of the activity of such compounds at the opiate receptor level.

X-ray Structure Determination, Absolute Configuration and Biological Activity of Phomoxanthone A

2005 ◽  
Vol 2005 (21) ◽  
pp. 4563-4570 ◽  
Author(s):  
Brigitta Elsässer ◽  
Karsten Krohn ◽  
Ulrich Flörke ◽  
Natalia Root ◽  
Hans-Jürgen Aust ◽  
...  
Keyword(s):  
Biological Activity ◽  
Absolute Configuration ◽  
Structure Determination ◽  
X Ray

scholarly journals Cannabidiol revisited

IUCrData ◽  
2017 ◽  
Vol 2 (2) ◽  
Author(s):  
Tobias Mayr ◽  
Tobias Grassl ◽  
Nikolaus Korber ◽  
Volker Christoffel ◽  
Michael Bodensteiner
Keyword(s):  
Absolute Configuration ◽  
Structure Determination ◽  
High Quality ◽  
Acta Cryst ◽  
X Ray ◽  
Radiation Sources ◽  
Wavelength Radiation ◽  
The Absolute ◽  
Absolute Structure ◽  
Intensity Radiation

The crystal structure of cannabidiol, C21H30O2, {systematic name: 2-[(1R,6R)-3-methyl-6-(prop-1-en-2-yl)cyclohex-2-enyl]-5-pentylbenzene-1,3-diol}, was determined earlier by Joneset al.[(1977).Acta Cryst.B33, 3211–3214] and Ottersen & Rosenqvist [(1977).Acta Chem. Scand.B31, 749–755]. In both investigations, the absolute configuration is given asR,R, referring to Mechoulamet al.[(1967.J. Am. Chem. Soc.89, 4552–4554]. In the latter, the absolute configuration was identified by chemical means. Using the advantages of modern single-crystal X-ray diffractometers such as area detectors and high-intensity radiation sources, a high-quality structure determination including the absolute configuration was possible and is shown in this work. Furthermore, the rather uncommon CuKβ wavelength radiation was applied for the structure determination, which confirmed the absolute structure to beR,R.

Oxetanes from Photocycloaddition of 2-Aminopropenenitriles to Methyl Phenylglyoxylate and Benzils

2006 ◽  
Vol 61 (3) ◽  
pp. 301-310 ◽  
Author(s):  
Christiane van Wolven ◽  
Dietrich Döpp ◽  
Gerald Henkel
Keyword(s):  
Single Crystal ◽  
Absolute Configuration ◽  
Structure Determination ◽  
Benzene Solution ◽  
X Ray ◽  
H Nmr ◽  
The Absolute ◽  
Layer Chromatography ◽  
Preparative Layer Chromatography

Abstract By irradiation of methyl phenylglyoxylate (1) in benzene solution in presence of equimolar amounts of 2-aminopropenenitriles H2C=C(NR2)CN (3a - e, NR2 = morpholino, 1-pyrrolidinyl, 1-piperidinyl, hexamethyleneimino, heptamethyleneimino) the corresponding 2R∗,3R∗ head-to-head oxetanes 4a - e were obtained in moderate yields (11 - 52%) along with 2 - 28% of rac-dimethyl 2,3- diphenyltartrate (2). In presence of (S)-2-(2-methoxymethylpiperidin-1-yl)propenenitrile ((+)-3g) 1 is transformed into 26% of 2 and 33% of a mixture of diastereomeric oxetanes 4g,4’g in a ratio of 1.4 : 1 which could be improved to 2.5 : 1 by preparative layer chromatography. The absolute configuration of the major diastereomer 4g was unambiguously confirmed by a single crystal X-ray structure determination to be 2R,3R,2’S. Analogous photoadditions to benzil (5a), 4,4’-bis-(trifluoromethyl)benzil (5b) and 4,4’-dichlorobenzil (5c) with (+)-3g and its lower homologue (S)-2-(2-methoxymethylpyrrolidin- 1-yl)propenenitrile ((-)-3f) gave oxetanes only in low yield as detected by 1H NMR. Byproducts arise from competitive symmetrical α-cleavage of 5.

scholarly journals Absolute structure and absolute configuration

1999 ◽  
Vol 55 (5) ◽  
pp. 908-915 ◽  
Author(s):  
H. D. Flack ◽  
G. Bernardinelli
Keyword(s):  
Single Crystal ◽  
Absolute Configuration ◽  
Structure Determination ◽  
Diffraction Experiment ◽  
X Ray Diffraction ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Absolute Structure

Fundamental notions concerning absolute structure and absolute configuration, and their determination from single-crystal diffraction measurements, are presented and reviewed. A glossary of terms with definitions useful in this field is provided. For absolute structure and its determination, the separate but interacting influences of the structure and the inversion-distinguishing power of an X-ray diffraction experiment with dispersive scatterers are examined. Important experimental and algorithmic details of the current methods used for absolute-structure determination are provided. Characterization of crystals for absolute-structure determination and of molecules for absolute-configuration determination are treated. Attention is given to the analysis of absolute structure and absolute configuration in twinned crystals.

CD-Spectroscopic Confirmation of the Absolute Configuration of a Conformationally Flexible Aldehyde Ester Containing a Quarternary Stereogenic Center

1998 ◽  
Vol 53 (10-11) ◽  
pp. 891-895 ◽  
Author(s):  
Jörg Fleischhauer ◽  
Axel Koslowski ◽  
Jan Schiffer ◽  
Axel Wollmer ◽  
Dieter Enders ◽  
...  
Keyword(s):  
Absolute Configuration ◽  
Structure Determination ◽  
Matrix Method ◽  
Aldehyde Ester ◽  
Cd Spectra ◽  
Perfect Agreement ◽  
X Ray ◽  
The Absolute ◽  
Stereogenic Center

Abstract The absolute configuration of the conformationally flexible aldehyde ester methyl-2-formyl-2-(phe-nylsulfanyl)-3-(3,4,5-trimethoxyphenyl)-propanoate was determined by comparison of measured and calculated CD spectra.The spectra were calculated by means of the so-called matrix method assuming R configuration at the stereogenic center. Calculated and observed signs of the first three most intense CD bands agree. Therefore, it was concluded that the absolute configuration of the compound was also R, which is in perfect agreement with the results of an X-ray structure determination.

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