scholarly journals Conformational investigation of alpha,beta-dehydropeptides. XIII. Conformational properties of N-acetyl-alpha,beta-dehydrovaline N',N'-dimethylamide.

2004 ◽  
Vol 51 (1) ◽  
pp. 145-152 ◽  
Author(s):  
Dawid Siodłak ◽  
Barbara Rzeszotarska ◽  
Małgorzata A Broda ◽  
Anna E Kozioł ◽  
Edyta Kołodziejczyk
Keyword(s):  
Type Ii ◽  
Beta Turn ◽  
X Ray ◽  
X Ray Crystallography ◽  
Tertiary Amide ◽  
Conformational Investigation ◽  
Conformational Properties ◽  
Alpha Beta ◽  
Solid State Conformation ◽  
Ab Initio Dft

The crystal structure of Ac-DeltaVal-NMe(2) (DeltaVal = alpha,beta-dehydrovaline) was determined by X-ray crystallography. The found angles phi = -60 degrees and psi = 125 degrees correspond exactly to the respective values of the (i + 1)th residue in idealised beta-turn II/VIa. Ab initio/DFT studies revealed that the molecule adopts the angle psi restricted only to about |130 degrees | and very readily attains the angle phi = about -50 degrees. This is in line with its solid-state conformation. Taken together, these data suggest that the DeltaVal residue combined with a C-terminal tertiary amide is a good candidate at the (i + 1)th position in a type II/VIa beta-turn.

Structural studies of some 1-polymethyleneimino-2,4-dinitrobenzenesand related compounds; crystal structure of 1-(cis-2′,6′-dimethylpiperidin-1′-yl)-2,4-dinitrobenzene

2000 ◽  
Vol 53 (8) ◽  
pp. 715 ◽  
Author(s):  
Maureen F. Mackay ◽  
Douglas J. Gale ◽  
John F. K. Wilshire
Keyword(s):  
Crystal Structure ◽  
Phenyl Ring ◽  
Ring Opening ◽  
Boat Conformation ◽  
Structural Studies ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Mean ◽  
Related Compounds ◽  
Solid State Conformation

The ultraviolet and 1H n.m.r. spectra of some 1-polymethyleneimino-2,4-dinitrobenzenes and related compounds are discussed. The effect of trifluoroacetic acid on these spectra was also investigated; with 1-azetidinyl-2,4-dinitrobenzene, acid-catalysed ring opening was observed. The solid-state conformation of 1-(cis-2′,6′-dimethylpiperidin-1′-yl)-2,4-dinitrobenzene has been defined by single-crystal X-ray crystallography. Triclinic crystals belong to the space group P–1 with a 8.165(1), b 7.865(1), c 11.148(1) Å, α 95.23(1), β 106.00(1), γ 92.63(1)˚ and Z 2. The structure was refined to a final R of 0.048 for the 2222 observed data. In the crystal, the phenyl ring adopts a slight boat conformation, while the amino and o-nitro groups are significantly twisted from the mean plane of the ring.

Influence of fluorine substitution on the molecular conformation of 3′-deoxy-3′-fluoro-5-methyluridine

2020 ◽  
Vol 76 (4) ◽  
pp. 346-352
Author(s):  
Manisha N. Aher ◽  
Namrata D. Erande ◽  
Vaijayanti A. Kumar ◽  
Moneesha Fernandes ◽  
Rajesh G. Gonnade
Keyword(s):  
Molecular Conformation ◽  
Asymmetric Unit ◽  
Screw Axis ◽  
Orthorhombic Space Group ◽  
Fluorine Substitution ◽  
X Ray ◽  
X Ray Crystallography ◽  
Conformational Properties ◽  
Independent Molecules ◽  
Phase Angles

Fluorine substitutions on the furanose ring of nucleosides are known to strongly influence the conformational properties of oligonucleotides. In order to assess the effect of fluorine on the conformation of 3′-deoxy-3′-fluoro-5-methyluridine (RTF), C10H13FN2O5, we studied its stereochemistry in the crystalline state using X-ray crystallography. The compound crystallizes in the chiral orthorhombic space group P212121 and contains two symmetry-independent molecules (A and B) in the asymmetric unit. The furanose ring in molecules A and B adopts conformations between envelope (2E, 2′-endo, P = 162°) and twisted (2T3, 2′-endo and 3′exo, P = 180°), with pseudorotation phase angles (P) of 164.3 and 170.2°, respectively. The maximum puckering amplitudes, νmax, for molecules A and B are 38.8 and 36.1°, respectively. In contrast, for 5-methyluridine (RTOH), the value of P is 21.2°, which is between the 3E (3′-endo, P = 18.0°) and 3T4 (3′-endo and 4′-exo, P = 36°) conformations. The value of νmax for RTOH is 41.29°. Molecules A and B of RTF generate respective helical assemblies across the crystallographic 21-screw axis through classical N—H...O aand O—H...O hydrogen bonds supplemented by C—H...O contacts. Adjacent parallel helices of both molecules are linked to each other via O—H...O and O...π interactions.

Conformation of a Fluorochrome from Aniline Blue

1997 ◽  
Vol 50 (10) ◽  
pp. 987
Author(s):  
Maureen F. Mackay, ◽  
Michael J. McTigue ◽  
Maruse Sadek
Keyword(s):  
Solid State ◽  
Single Crystal ◽  
Dimethyl Sulfoxide ◽  
Chemical Shifts ◽  
Deuterium Oxide ◽  
Sodium Ion ◽  
Space Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
Solid State Conformation

The solid-state conformation of the fluorochrome sodium 4,4′-[carbonylbis(benzene-4,1-diyl)bis(imino)]-bisbenzenesulfonate has been defined by single-crystal X-ray crystallography. Monoclinic crystals belong to the space group C 2/c with a 11·732(1), b 6·185(1), c 37·179(3) Å, β 94·40(1)° and Z 8. The structure was refined to a final R0·042 for all 2271 unique terms. In the crystal six oxygen atoms form an octahedral grouping around the sodium ion and these octahedra are linked into layers sandwiched between the layers of organic anions which adopt an extended conformation. The n.m.r. spectra indicate that in solution the fluorochrome is flexible and averages to an extended structure that maintains symmetry about its longitudinal and carbonyl axes. Chemical shifts have been measured in water, deuterium oxide and (D6)dimethyl sulfoxide

Synthesis and Structural Characterization of N-Methyl-DL-glutamic Acid

2000 ◽  
Vol 53 (3) ◽  
pp. 237 ◽  
Author(s):  
Andrew B. Hughes ◽  
Maureen F. Mackay ◽  
Luigi Aurelio
Keyword(s):  
Three Dimensional ◽  
Amino Nitrogen ◽  
Measured Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Zwitterionic Form ◽  
Dimensional Network ◽  
Orthorhombic Crystals ◽  
Solid State Conformation

The solid-state conformation of racemic N-methylglutamic acid has been defined by single-crystal X-ray crystallography. Orthorhombic crystals belong to the space group Pbca with a 15.219(2), b 10.583(1), c 9.595(1) Å and Z 8. The structure was refined to a final R value of 0.049 for the 1285 measured data. In the crystal the molecules adopt a zwitterionic form with protonation having occurred at the amino nitrogen atom. The a-carboxyl is unprotonated with the d-carboxy group retaining a proton. The i.r. spectrum shows absorptions which also are indicative of the amino acid being in the zwitterionic form. Intermolecular H-bonds involving the carboxylate proton and the two protons on the N-atom link the molecules into a three-dimensional network in the crystal.

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