scholarly journals Memorial Issue Dedicated to Dr. Howard D. Flack: The Man behind the Flack Parameter

Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 818-820
Author(s):  
Catherine E. Housecroft ◽  
Katharina M. Fromm
Keyword(s):  
Single Crystal ◽  
Absolute Configuration ◽  
Molecular Species ◽  
Crystalline Material ◽  
Special Issue ◽  
X Ray Diffraction ◽  
X Ray ◽  
Memorial Issue ◽  
The Absolute ◽  
Absolute Structure

This Special Issue of Chemistry is dedicated to Dr. Howard D. Flack (1943–2017), a renowned crystallographer who transformed the way in which, by using single crystal X-ray diffraction, we are able to determine the absolute structure of a crystalline material, and thereby determine the absolute configuration of molecular species within the material [...]

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.

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.

scholarly journals D-Glutamic acid hydrochloride

IUCrData ◽  
2019 ◽  
Vol 4 (4) ◽  
Author(s):  
Leonardo Y. Fox-Uribe ◽  
Javier Hernández-Paredes ◽  
Yedith Soberanes ◽  
Ignacio Valenzuela-Chavira ◽  
Karina D. Garcia-Orozco ◽  
...  
Keyword(s):  
Glutamic Acid ◽  
Single Crystal ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray ◽  
Acid Hydrochloride ◽  
The Absolute ◽  
Absolute Structure

The absolute structure of D-glutamic acid hydrochloride [systematic name: (R)-1,3-dicarboxypropan-1-aminium chloride], C5H10NO4 +·Cl−, has been determined by single-crystal X-ray diffraction at room temperature using Cu Kα radiation.

Vibrational circular dichroism and single crystal X-Ray diffraction analyses of [Ir(bzq)2(phen)]+ (bzq = benzo[h]quinoline; phen = 1,10-phenanthroline): absolute configuration and role of CH–π interaction in molecular packing

2017 ◽  
Vol 46 (13) ◽  
pp. 4397-4402 ◽  
Author(s):  
Kazuyoshi Takimoto ◽  
Yutaka Watanabe ◽  
Shigeki Mori ◽  
Hisako Sato
Keyword(s):  
Circular Dichroism ◽  
Single Crystal ◽  
Absolute Configuration ◽  
Molecular Packing ◽  
Vibrational Circular Dichroism ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Absolute ◽  
Circular Dichroïsm

The absolute configuration of a cationic iridium(iii) complex was determined in solution and solid by vibrational circular dichroism and X-ray diffraction analyses.

Crystal structure of aristoserratine

1983 ◽  
Vol 36 (5) ◽  
pp. 1037 ◽  
Author(s):  
IRC Bick ◽  
MA Hai ◽  
VA Patrick ◽  
AH White
Keyword(s):  
Crystal Structure ◽  
Circular Dichroism ◽  
Single Crystal ◽  
Absolute Configuration ◽  
Circular Dichroism Spectrum ◽  
X Ray Diffraction ◽  
Relative Configuration ◽  
X Ray ◽  
The Absolute ◽  
Circular Dichroïsm

The crystal structure of the alkaloid aristoserratine,* C20H24N2O, has been determined by single-crystal X-ray diffraction methods at 295 K, the structure being refined to a residual of 0.034 for 1107 independent 'observed' reflections. Crystals are monoclinic, P21, a 14.836(5), b 8.568(3), c 6.633(3) �, β 98.05(3)�, Z 2. The relative configuration is established and, by inference, by comparison of the circular dichroism spectrum with that of aristoteline, the absolute configuration is assigned.

Alkaloids of Templetonia retusa. Chemistry, Structure and Absolute Configuration of (-)-Templetine

1991 ◽  
Vol 44 (4) ◽  
pp. 509 ◽  
Author(s):  
JR Cannon ◽  
JR Williams ◽  
D Arbain ◽  
A Brossi ◽  
JF Blount ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Carbon Disulfide ◽  
Absolute Configuration ◽  
Perchloric Acid ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Absolute ◽  
Absolute Structure ◽  
Least Squares Techniques

(-)-Cytisine, (+)-lupanine, (-)-anagyrine, (�)-piptanthine and (-)-templetine have been isolated from Templetonia retusa (Vent.) R.Br. The absolute crystal structures of the trihydrochloride dihydrate and the isomorphous trihydrobromide dihydrate of (-)- templetine have both been determined by single-crystal X-ray diffraction; diffractometer data at 295 K were refined by least-squares techniques to residuals of 0.045 and 0.031, respectively, for 2351 and 1948 'observed' reflections. Crystals of the trihydrochloride are orthorhombic P212121, a 8.830(4), b 14.201(6), c 19.122(12)Ǻ, Z 4. Crystals of the trihydrobromide are isomorphous, a 9.081(3), b 14.578(2), c 19.197(11)Ǻ, Z 4. The absolute structure (1) of (-)- templetine has led to the absolute structure of its dehydrogenation product (-)- dehydropiptanthine perchlorate (7) which, in turn, has allowed the absolute structures of (-)- ormosanine (6), (+)- piptanthine (4) and (-)- panamine (9) to be defined. (-)- Templetine (1) reacts with formaldehyde to form homotempletine (12) and with carbon disulfide to yield the thiourea (13). Treatment of either (12) or (13) with W-1 Raney nickel followed by perchloric acid has yielded the diperchlorate (15). The X-ray crystal structure of the diperchlorate (15) has also been determined: diffractometer data at 295 K were refined by least-squares techniques to a residual of 0.056 (1312 'observed' reflections). Crystals of the diperchlorate (15) are orthorhombic, P212121, a 18.636(5), b 12.569(6), c 10.403(4)Ǻ, Z 4.

The Absolute Structure of Latifoline

1992 ◽  
Vol 45 (2) ◽  
pp. 451 ◽  
Author(s):  
CCJ Culvenor ◽  
MF Mackay
Keyword(s):  
Single Crystal ◽  
Absolute Configuration ◽  
Crystallographic Analysis ◽  
Salt Hydrate ◽  
Space Group ◽  
X Ray ◽  
Orthorhombic Crystals ◽  
The Absolute ◽  
Absolute Structure

The absolute structure of latifoline, a pyrrolizidine diester alkaloid of retronecine and latifolic and angelic acids, has been defined by single-crystal X-ray crystallographic analysis of the hydrobromide salt hydrate. Orthorhombic crystals of C20H27NO7.HBr.H2O belong to the space group P 2′2′2′ with a 7.279(1), b 17.898(3), c 17.922(2) � and V 2334-9(8) � 3 . The structure has been refined to an R index of 0.054 for 1725 observed terms. The absolute configuration has been assigned by comparison with that of retronecine and also determined independently by X-ray examination of selected Bijvoet pairs. Our results have shown that the absolute structure of latifolic acid is 13S,14R,19S (2R,3S,4S in latifolic acid numbering), and not the stereoisomer reported recently by Roitman and Wong.

scholarly journals Difficulties to Determine the Absolute Configuration of Guaiaretic Acid

2018 ◽  
Vol 13 (8) ◽  
pp. 1934578X1801300
Author(s):  
Alfredo R. Ortega ◽  
Eleuterio Burgueño-Tapia ◽  
Pedro Joseph-Nathan
Keyword(s):  
Symmetric Space ◽  
Single Crystal ◽  
Absolute Configuration ◽  
Structure Elucidation ◽  
Carbon Chain ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
The Absolute ◽  
Stereogenic Center

An account of the difficulties to determine the absolute configuration (AC) of guaiaretic acid (1a), using contemporary methodology, is described in commemoration of the century of its structure elucidation. In fact, the herein studied molecule was the derived diacetate 1b, since the natural lignan slowly decomposes upon manipulation. Single crystal X-ray diffraction of 1b demonstrated the structure, but calculation of Flack and Hooft parameters to know the AC was unsuccessful since the crystals were triclinic, P-1, which is a centro-symmetric space group. In turn, manual band to band comparison of experimental and DFT B3LYP/DGDZVP calculated VCD spectra of 1b allowed ascertaining its AC, although automatic comparison using the Compare VOA software was not very successful. This behavior is associated to the fact that the studied molecule has a sole stereogenic center located on the acyclic portion of a carbon chain possessing two quite similar substituents. The behavior is discussed in relation to cases where the molecular flexibility also generates a very large number of conformers.

Confirmation of the absolute configuration of Stachybotrin C using single-crystal X-ray diffraction analysis of its 4-bromobenzyl ether derivative

2018 ◽  
Vol 71 (6) ◽  
pp. 584-591 ◽  
Author(s):  
Yu Kuroda ◽  
Keiko Hasegawa ◽  
Keiichi Noguchi ◽  
Kazuhiro Chiba ◽  
Keiji Hasumi ◽  
...  
Keyword(s):  
Single Crystal ◽  
Diffraction Analysis ◽  
Absolute Configuration ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ether Derivative ◽  
The Absolute

Crystal structures of (S)- and (R,S)-2,2′-bipyridine-3,3′-dicarboxylic acid 1,1′-dioxides and of their barium salts: absolute configuration and molecular distortion enforced by supramolecular self-assembly

1997 ◽  
Vol 212 (3) ◽  
Author(s):  
P. Vojtíšek ◽  
I. Císařová ◽  
J. Podlaha ◽  
Z. Žák ◽  
S. Böhm ◽  
...  
Keyword(s):  
Single Crystal ◽  
Dicarboxylic Acid ◽  
Crystal Structures ◽  
Absolute Configuration ◽  
Self Assembly ◽  
Barium Salt ◽  
X Ray Diffraction ◽  
X Ray

AbstractCrystal structures of the title compounds were determined by single crystal X-ray diffraction. Absolute configuration of the barium salt of (+)-(

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