Conformational study of the 3,6-dihydro-2H-1,4-oxazin-2-one fragment in 8-tert-butyl-7-methoxy-8-methyl-9-oxa-6-azaspiro[4.5]decane-2,10-dione stereoisomers

2017 ◽  
Vol 73 (7) ◽  
pp. 556-562
Author(s):  
Ewa Żesławska ◽  
Anna Jakubowska ◽  
Wojciech Nitek
Keyword(s):  
Amino Acids ◽  
Crystal Structures ◽  
Stereoselective Synthesis ◽  
Biologically Active ◽  
Asymmetric Unit ◽  
Conformational Study ◽  
X Ray Diffraction ◽  
X Ray ◽  
Natural Amino Acids ◽  
Heterocyclic Moiety

Unnatural cyclic α-amino acids play an important role in the search for biologically active compounds and macromolecules. Enantiomers of natural amino acids with a D configuration are not naturally encoded, but can be chemically synthesized. The crystal structures of two enantiomers obtained by a method of stereoselective synthesis, namely (5R,8S)-8-tert-butyl-7-methoxy-8-methyl-9-oxa-6-azaspiro[4.5]decane-2,10-dione, (1), and (5S,8R)-8-tert-butyl-7-methoxy-8-methyl-9-oxa-6-azaspiro[4.5]decane-2,10-dione, (2), both C14H21NO4, were determined by X-ray diffraction. Both enantiomers crystallize isostructurally in the space group P21, with one molecule in the asymmetric unit and with the same packing motif. The crystal structures are stabilized by C—H...O hydrogen bonds, resulting in the formation of chains along the [100] and [010] directions. The conformation of the 3,6-dihydro-2H-1,4-oxazin-2-one fragment was compared with other crystal structures possessing this heterocyclic moiety. The comparison showed that the title compounds are not exceptional among structures containing the 3,6-dihydro-2H-1,4-oxazin-2-one fragment. The planar moiety was more frequently observed in derivatives in which this fragment was not condensed with other rings.

Influence of 3-{5-[4-(diethylamino)benzylidene]rhodanine}propionic acid on the conformation of 5-(4-chlorobenzylidene)-2-(4-methylpiperazin-1-yl)-3H-imidazol-4(5H)-one

2018 ◽  
Vol 74 (11) ◽  
pp. 1427-1433 ◽  
Author(s):  
Ewa Żesławska ◽  
Wojciech Nitek ◽  
Waldemar Tejchman ◽  
Jadwiga Handzlik
Keyword(s):  
Crystal Structures ◽  
Crystal Packing ◽  
Protonated Form ◽  
Acid Form ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
Basic Form ◽  
Piperazine Ring ◽  
X Ray ◽  
Intermolecular Contacts

The arylidene–imidazolone derivatives are a group of compounds of great interest in medicinal chemistry due to their various pharmacological actions. In order to study the possible conformations of an arylidene–imidazolone derivative, two new crystal structures were determined by X-ray diffraction, namely (Z)-5-(4-chlorobenzylidene)-2-(4-methylpiperazin-1-yl)-3H-imidazol-5(4H)-one, C15H17ClN4O, (6), and its salt 4-[5-(4-chlorobenzylidene)-5-oxo-4,5-dihydro-3H-imidazol-2-yl]-1-methylpiperazin-1-ium 3-{5-[4-(diethylamino)benzylidene]-4-oxo-2-thioxothiazolidin-3-yl}propionate, C15H18ClN4O+·C17H19N2O3S2 −, (7). Both compounds crystallize in the space group P\overline{1}. The basic form (6) crystallizes with two molecules in the asymmetric unit. In the acid form of (6), the N atom of the piperazine ring is protonated by proton transfer from the carboxyl group of the rhodanine acid derivative. The greatest difference in the conformations of (6) and its protonated form, (6c), is observed in the location of the arylidene–imidazolone substituent at the N atom. In the case of (6c), the position of this substituent is close to axial, while for (6), the corresponding position is intermediate between equatorial and axial. The crystal packing is dominated by a network of N—H...O hydrogen bonds. Furthermore, the crystal structures are stabilized by numerous intermolecular contacts of types C—H...N and C—H...Cl in (6), and C—H...O and C—H...S in (7). The geometry with respect to the location of the substituents at the N atoms of the piperazine ring was compared with other crystal structures possessing an N-methylpiperazine moiety.

Structural Studies of Some o- and p-Nitrophenylcarbamates by IR Spectroscopy and X-Ray Diffraction

2008 ◽  
Vol 63 (12) ◽  
pp. 1402-1406
Author(s):  
Monika Simon ◽  
Carol Csunderlik ◽  
G. Jones
Keyword(s):  
Ir Spectroscopy ◽  
Crystal Structures ◽  
Ir Spectrum ◽  
Structural Studies ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
X Ray

N-Alkyl-o-nitrophenylcarbamates as solids present two carbonyl stretching bands in the region 1700 - 1800 cm−1 but similar N-alkyl-p-nitrophenylcarbamates have only one such band in the IR spectrum. In solution both kinds of carbamate present one carbonyl stretching band, but for the former, the splittings occur when the carbamates crystallize. Four crystal structures were analyzed by X-ray diffraction. The two ortho derivatives have more than one molecule in the asymmetric unit, which is consistent with the IR observations.

scholarly journals Hydrogels formed from Fmoc amino acids

CrystEngComm ◽  
2015 ◽  
Vol 17 (42) ◽  
pp. 8047-8057 ◽  
Author(s):  
Emily R. Draper ◽  
Kyle L. Morris ◽  
Marc A. Little ◽  
Jaclyn Raeburn ◽  
Catherine Colquhoun ◽  
...  
Keyword(s):  
Amino Acids ◽  
Molecular Weight ◽  
Single Crystal ◽  
Crystal Structures ◽  
Diffraction Data ◽  
Low Molecular Weight ◽  
X Ray Diffraction ◽  
X Ray ◽  
Single Crystal Structures

A number of Fmoc amino acids can be effective low molecular weight hydrogelators; we compare single crystal structures to fibre X-ray diffraction data.

scholarly journals Crystal structures of 5,12-dimethyl-1,4,8,11-tetraazacyclotetradecane cobalt(III) mono-phenylacetylide and bis-phenylacetylide

2018 ◽  
Vol 74 (4) ◽  
pp. 522-529 ◽  
Author(s):  
Benjamin M. Oxley ◽  
Brandon Mash ◽  
Matthias Zeller ◽  
Susannah Banziger ◽  
Tong Ren
Keyword(s):  
Crystal Structures ◽  
Symmetry Operator ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
Weak Base ◽  
Monoclinic Symmetry ◽  
X Ray ◽  
Independent Molecules ◽  
Solvent Molecules ◽  
Occupancy Rates

Reported in this contribution are the synthesis and crystal structures of new mono- and bis-phenylacetylides based on CoIII(DMC) (DMC is 5,12-dimethyl-1,4,8,11-tetraazacyclotetradecane). Chlorido(5,12-dimethyl-1,4,8,11-tetraazacyclotetradecane)(phenylethynyl)cobalt(III) chloride–acetonitrile–methanol (1/1/1), [Co(C8H5)Cl(C12H28N4)]Cl·CH3CN·CH3OH, 1, and (5,12-dimethyl-1,4,8,11-tetraazacyclotetradecane)bis(phenylethynyl)cobalt(III) trifluoromethanesulfonate–dichloromethane (2/1), [Co(C8H5)2(C12H28N4)]2(CF3SO3)2·CH2Cl2, 2, were prepared under weak-base conditions in satisfactory yields. Single-crystal X-ray diffraction studies revealed that both 1 and 2 adopt a pseudo-octahedral symmetry in which the Cl—Co—C angles of 1 and C—Co—C of 2 range from 177.7 (2) to 178.0 (2)° and from 177.67 (9) to 179.67 (9)°, respectively. In both structures, the CoIII metal center is coordinated in the equatorial plane by four N atoms, in which the N—Co—N angles range from 85.6 (3) to 94.4 (3)°. The structure of 1 features two crystallographically independent molecules in its triclinic cell (Z′ = 2), which are related to each other by pseudo-monoclinic symmetry. The crystal investigated was twinned by a symmetry operator of the approximate double-volume C-centered cell (180° rotation around [201] of the actual triclinic cell), with a refined twin ratio of 0.798 (3) to 0.202 (3). Both methanol solvent molecules in 1 are disordered, the major occupancy rates refined to 0.643 (16) and 0.357 (16). Compound 2 also contains two molecules in the asymmetric unit, together with two trifluoromethanesulfonate anions [of which one is disordered; occupancy values of 0.503 (16) and 0.497 (16)] and a disordered dichloromethane [occupancy values of 0.545 (12) and 0.455 (12)].

scholarly journals Crystal structures of cristobalite-type and coesite-type PON redetermined on the basis of single-crystal X-ray diffraction data

2015 ◽  
Vol 71 (11) ◽  
pp. 1325-1327 ◽  
Author(s):  
Maxim Bykov ◽  
Elena Bykova ◽  
Vadim Dyadkin ◽  
Dominik Baumann ◽  
Wolfgang Schnick ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Single Crystals ◽  
Crystal Structures ◽  
Rotation Axis ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structure Determinations ◽  
Anisotropic Displacement Parameters

Hitherto, phosphorus oxonitride (PON) could not be obtained in the form of single crystals and only powder diffraction experiments were feasible for structure studies. In the present work we have synthesized two polymorphs of phosphorus oxonitride, cristobalite-type (cri-PON) and coesite-type (coe-PON), in the form of single crystals and reinvestigated their crystal structures by means of in house and synchrotron single-crystal X-ray diffraction. The crystal structures ofcri-PON andcoe-PON are built from PO2N2tetrahedral units, each with a statistical distribution of oxygen and nitrogen atoms. The crystal structure of thecoe-PON phase has the space groupC2/cwith seven atomic sites in the asymmetric unit [two P and three (N,O) sites on general positions, one (N,O) site on an inversion centre and one (N,O) site on a twofold rotation axis], while thecri-PON phase possesses tetragonalI-42dsymmetry with two independent atoms in the asymmetric unit [the P atom on a fourfold inversion axis and the (N,O) site on a twofold rotation axis]. In comparison with previous structure determinations from powder data, all atoms were refined with anisotropic displacement parameters, leading to higher precision in terms of bond lengths and angles.

scholarly journals Crystallization and X-ray diffraction analysis of chondroitin lyase from baculovirus: envelope protein ODV-E66

2012 ◽  
Vol 68 (2) ◽  
pp. 190-192 ◽  
Author(s):  
Yoshirou Kawaguchi ◽  
Nobuo Sugiura ◽  
Momo Onishi ◽  
Koji Kimata ◽  
Makoto Kimura ◽  
...  
Keyword(s):  
Amino Acids ◽  
Diffraction Analysis ◽  
Envelope Protein ◽  
Unique Characteristic ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters ◽  
Baculovirus Infection

Baculovirus envelope protein ODV-E66 (67–704), in which the N-terminal 66 amino acids are truncated, is a chondroitin lyase. It digests chondroitin and chondroitin 6-sulfate efficiently, but does not digest chondroitin 4-sulfate. This unique characteristic is useful for the preparation of specific chondroitin oligosaccharides and for investigation of the mechanism of baculovirus infection. ODV-E66 (67–704) was crystallized; the crystal diffracted to 1.8 Å resolution and belonged to space groupP62orP64, with unit-cell parametersa = b = 113.5,c= 101.5 Å. One molecule is assumed to be present per asymmetric unit, which gives a Matthews coefficient of 2.54 Å3 Da−1.

L-Lysine: Exploiting Powder X-ray Diffraction to Complete the Set of Crystal Structures of the 20 Directly Encoded Proteinogenic Amino Acids

2015 ◽  
Vol 127 (13) ◽  
pp. 4045-4049 ◽  
Author(s):  
P. Andrew Williams ◽  
Colan E. Hughes ◽  
Kenneth D. M. Harris
Keyword(s):  
Amino Acids ◽  
Crystal Structures ◽  
X Ray Diffraction ◽  
X Ray

Examination of Rabbit Fc Crystals

1968 ◽  
Vol 26 ◽  
pp. 140-141
Author(s):  
J. P. Robinson ◽  
P. G. Lenhert
Keyword(s):  
Molecular Weight ◽  
Flat Plate ◽  
Phosphate Buffer ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Neutral Ph ◽  
Small Crystals ◽  
Carbon Coated ◽  
Diffraction Patterns

Crystallographic studies of rabbit Fc using X-ray diffraction patterns were recently reported. The unit cell constants were reported to be a = 69. 2 A°, b = 73. 1 A°, c = 60. 6 A°, B = 104° 30', space group P21, monoclinic, volume of asymmetric unit V = 148, 000 A°3. The molecular weight of the fragment was determined to be 55, 000 ± 2000 which is in agreement with earlier determinations by other methods.Fc crystals were formed in water or dilute phosphate buffer at neutral pH. The resulting crystal was a flat plate as previously described. Preparations of small crystals were negatively stained by mixing the suspension with equal volumes of 2% silicotungstate at neutral pH. A drop of the mixture was placed on a carbon coated grid and allowed to stand for a few minutes. The excess liquid was removed and the grid was immediately put in the microscope.

Transmission electron microscope studies in special ceramics

1978 ◽  
Vol 36 (1) ◽  
pp. 268-269
Author(s):  
A. Zangvil ◽  
L.J. Gauckler ◽  
G. Schneider ◽  
M. Rühle
Keyword(s):  
Phase Diagrams ◽  
Crystal Structures ◽  
Thin Foil ◽  
Limited Extent ◽  
Complex Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
Lattice Resolution

The use of high temperature special ceramics which are usually complex materials based on oxides, nitrides, carbides and borides of silicon and aluminum, is critically dependent on their thermomechanical and other physical properties. The investigations of the phase diagrams, crystal structures and microstructural features are essential for better understanding of the macro-properties. Phase diagrams and crystal structures have been studied mainly by X-ray diffraction (XRD). Transmission electron microscopy (TEM) has contributed to this field to a very limited extent; it has been used more extensively in the study of microstructure, phase transformations and lattice defects. Often only TEM can give solutions to numerous problems in the above fields, since the various phases exist in extremely fine grains and subgrain structures; single crystals of appreciable size are often not available. Examples with some of our experimental results from two multicomponent systems are presented here. The standard ion thinning technique was used for the preparation of thin foil samples, which were then investigated with JEOL 200A and Siemens ELMISKOP 102 (for the lattice resolution work) electron microscopes.

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