Stereochemistry of Protected Ornithine Side Chains of Gramicidin S Derivatives:  X-ray Crystal Structure of the Bis-Boc-tetra-N-methyl Derivative of Gramicidin S

2002 ◽  
Vol 124 (43) ◽  
pp. 12684-12688 ◽  
Author(s):  
Keiichi Yamada ◽  
Masafumi Unno ◽  
Kyoko Kobayashi ◽  
Hiroyuki Oku ◽  
Hatsuo Yamamura ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Side Chains ◽  
Methyl Derivative ◽  
X Ray ◽  
Gramicidin S

NMR-Spectra and Solution Structures of Some Piperazine-2,5-Diones. X-Ray Crystal-Structure of Threo-1-Acetyl-3-(Alpha-Bromobenzyl)-3-Methoxy-Piperazine-2,5-Dione

1986 ◽  
Vol 39 (7) ◽  
pp. 1141 ◽  
Author(s):  
JA Elix ◽  
GD Fallon ◽  
SM Marcuccio ◽  
ID Rae
Keyword(s):  
Crystal Structure ◽  
Heterocyclic Ring ◽  
Ring System ◽  
Side Chain ◽  
Boat Conformation ◽  
Methyl Derivative ◽  
X Ray ◽  
Solution Structures ◽  
Cdcl3 Solution ◽  
Substituted Piperazine

3-(α- Bromobenzyl )-3-methoxypiperazine-2,5-diones are prepared by the reaction of 3-benzylidenepiperazine-2,5-diones with N- bromosuccinimide in methanol. The crystal structure of the threo-1-acetyl compound shows the side chain in the EN conformation, with the bromine above the heterocyclic ring, the latter ring system being almost planar. This conformer predominates in CDCl3 solution also, but in (CD3)2SO the piperazine-2,5-dione ring adopts a boat conformation. Both the erythro isomer and an N(4)-methyl derivative exist in solution predominantly as folded conformers. The importance of repulsive interactions in predicting the conformation of substituted piperazine-2,5-diones is discussed.

In situ iodination and X-ray crystal structure of a foldamer helix bundle

2016 ◽  
Vol 52 (6) ◽  
pp. 1202-1205 ◽  
Author(s):  
Gavin William Collie ◽  
Karolina Pulka-Ziach ◽  
Gilles Guichard
Keyword(s):  
Crystal Structure ◽  
Structure Determination ◽  
Side Chains ◽  
Anomalous Diffraction ◽  
X Ray ◽  
Helix Bundle

We report here the efficient in situ iodination of tyrosine-type side-chains located within a foldamer helix bundle, permitting structure determination using single-wavelength anomalous diffraction (SAD) methods.

Derivatives of the Benzo[5,6]cyclohepta[1,2,3-Cd]thieno[3,2-C]pyridine System. X-Ray Crystal Structure of 8,9-Dimethoxy-1,2,3,6,11,11a-hexahydrobenzo[5,6]cyclohepta[1,2,3-Cd]thieno[3,2-C]pyridine-1-carbonitrile

1988 ◽  
Vol 41 (4) ◽  
pp. 575 ◽  
Author(s):  
JB Bremner ◽  
EJ Browne ◽  
LM Engelhardt ◽  
BA Hyland ◽  
GS James ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Cyanogen Bromide ◽  
Heterocyclic System ◽  
Crystal And Molecular Structure ◽  
Ring Cleavage ◽  
Methyl Derivative ◽  
X Ray ◽  
Derivatives Of ◽  
By Products

During attempts to prepare 9,10-dimethoxy-4,7,12,12a-tetrahydro-5H- benzo [g] thieno [3,2-a] quinolizine (1), and subsequent cyanogen bromide- induced ring cleavage of this tetracyclic base, two by-products were isolated. The preparations of these two compounds are described, and their structures elucidated as 8,9-dimethoxy-1,2,3,6,11,11a-hexahydrobenzo [5,6] cyclohepta [1,2,3-cd] thieno [3,2-c]pyridine (5a), and its 1-carbonitrile derivative (5b). An N-methyl derivative (5c) has been prepared from (5a). These products (5) are the first examples of a new heterocyclic system. The crystal and molecular structure of the cyanamide (5b) has been determined by X-ray crystallographic methods.

Synthesis of complexes of the type cis-Pt(amine) (unsaturated ligand)Cl2 and crystal structure cis-Pt(methylaimne) (dimethylhexynediol)Cl2

1989 ◽  
Vol 67 (12) ◽  
pp. 2209-2212 ◽  
Author(s):  
F. D. Rochon ◽  
R. Melanson ◽  
Monique Doyon
Keyword(s):  
Crystal Structure ◽  
Platinum Complexes ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Methyl Derivative ◽  
Full Matrix ◽  
X Ray ◽  
H Nmr ◽  
R Factor ◽  
Square Planar

Complexes of the type cis-Pt(L)(un)Cl2 where L = primary amine or methyl derivative of pyridine and un = cyclopentene, cyclohexene, or dimethylhexynediol, have been synthesized from the reaction of K[Pt(L)Cl3] with the unsaturated ligand in water. The compounds were characterized and studied by 1H NMR and IR spectroscopy. The crystal structure of cis-Pt(CH3NH2)((CH3)2C(OH)—C≡C—C(OH)(CH3)2)Cl2 was determined by X-ray diffraction methods. The crystals are monoclinic, space group P21/c, with a = 6.544(2), b = 14.304(7), c = 15.508(7) Å, β = 109.39(2)°, and Z = 4. The coordinates and the anisotropic thermal factors were refined by full-matrix least-squares analysis to a R factor of 0.048 and wR = 0.047. The coordination around the platinum atom is square planar and the acetylenic ligand is perpendicular to the Pt plane. Keywords: platinum complexes, crystal structure, methylamine, dimethylhexynediol, synthesis.

A study on α-RuCl3 crystal structure by scanning tunneling microscopy

1989 ◽  
Vol 47 ◽  
pp. 30-31
Author(s):  
H.-J. Cantow ◽  
H. Hillebrecht ◽  
S. Magonov ◽  
H. W. Rotter ◽  
G. Thiele
Keyword(s):  
Crystal Structure ◽  
Density Distribution ◽  
Scanning Tunneling Microscopy ◽  
Electron Density ◽  
Structure Determination ◽  
Electron Density Distribution ◽  
Scanning Tunneling ◽  
Monoclinic Space Group ◽  
Tunneling Microscopy ◽  
X Ray

From X-ray analysis, the conclusions are drawn from averaged molecular informations. Thus, limitations are caused when analyzing systems whose symmetry is reduced due to interatomic interactions. In contrast, scanning tunneling microscopy (STM) directly images atomic scale surface electron density distribution, with a resolution up to fractions of Angstrom units. The crucial point is the correlation between the electron density distribution and the localization of individual atoms, which is reasonable in many cases. Thus, the use of STM images for crystal structure determination may be permitted. We tried to apply RuCl3 - a layered material with semiconductive properties - for such STM studies. From the X-ray analysis it has been assumed that α-form of this compound crystallizes in the monoclinic space group C2/m (AICI3 type). The chlorine atoms form an almost undistorted cubic closed package while Ru occupies 2/3 of the octahedral holes in every second layer building up a plane hexagon net (graphite net). Idealizing the arrangement of the chlorines a hexagonal symmetry would be expected. X-ray structure determination of isotypic compounds e.g. IrBr3 leads only to averaged positions of the metal atoms as there exist extended stacking faults of the metal layers.

X-ray Crystal Structure of ?9-THC-tosylate

Planta Medica ◽  
2008 ◽  
Vol 74 (03) ◽  
Author(s):  
W Gul ◽  
P Carvalho ◽  
D Slade ◽  
M Avery ◽  
JR Duchek ◽  
...  
Keyword(s):  
Crystal Structure ◽  
X Ray

Crystal structure of an inclusion complex between chiral monoaza-15-crown-5 and S(–)-1-phenyl-ethyl ammonium percholorate

2003 ◽  
Vol 218 (5) ◽  
Author(s):  
Süheyla Özbey ◽  
F. B. Kaynak ◽  
M. Toğrul ◽  
N. Demirel ◽  
H. Hoşgören
Keyword(s):  
Crystal Structure ◽  
Inclusion Complex ◽  
Single Crystal ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
New Type

AbstractA new type of inclusion complex, S(–)-1 phenyl ethyl ammonium percholorate complex of R-(–)-2-ethyl - N - benzyl - 4, 7, 10, 13 - tetraoxa -1- azacyclopentadecane, has been prepared and studied by NMR, IR and single crystal X-ray diffraction techniques. The compound crystallizes in space group

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2020 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.50 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

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