scholarly journals Ethyl (3S)-3-[(3aR,5R,6S,6aR)-6-hydroxy-2,2-dimethyltetrahydrofuro[4,5-d][1,3]dioxol-5-yl]-3-{(3S)-3-[(3aR,5R,6S,6aR)-6-hydroxy-2,2-dimethyltetrahydrofuro[4,5-d][1,3]dioxol-5-yl]-5-oxoisoxazolidin-2-yl}propanoate chloroform monosolvate

IUCrData ◽  
2020 ◽  
Vol 5 (6) ◽  
Author(s):  
Aldo Guillermo Amaro Hernández ◽  
Tomasa Rodríguez Tzompantzi ◽  
Álvaro Dávila García ◽  
Rosa Luisa Meza-León ◽  
Sylvain Bernès
Keyword(s):  
Absolute Configuration ◽  
Diffraction Data ◽  
Michael Addition ◽  
Room Temperature ◽  
Resonant Scattering ◽  
Systematic Errors ◽  
The Other ◽  
Compound C ◽  
Cl Atoms ◽  
Absolute Structure

The title compound, C22H33NO12·CHCl3, was obtained as a product of a double aza-Michael addition of hydroxylamine on a Chiron with a known absolute configuration. The enantiopure compound crystallized as a chloroform solvate, in space group P1, and diffraction data were collected at room temperature with Ag Kα radiation. The Flack parameter refined to x = −0.01 (16); however, the Flack and Watkin 2AD plot clearly shows that differences between Friedel opposites (the D component of the plot) do not carry any reliable information about resonant scattering of Cl atoms, and are rather dominated by random and systematic errors. The RD factor calculated using 1941 acentric Friedel pairs is RD = 0.995. On the other hand, the 2A component of the plot, related to average intensities of Friedel pairs, shows that data are of good quality (RA = 0.069). This example illustrates that while using Ag Kα radiation (λ = 0.56083 Å), scatterers heavier than Cl should be present in a chiral crystal in order to determine confidently the absolute structure of the crystal.

scholarly journals 3β-Hydroxy-28-norolea-12,17-dien-11-one

2014 ◽  
Vol 70 (8) ◽  
pp. o842-o842
Author(s):  
Werner Seebacher ◽  
Robert Weis ◽  
Johanna Faist ◽  
Robert Saf ◽  
Ferdinand Belaj
Keyword(s):  
Hydrogen Bonds ◽  
Diffraction Data ◽  
Title Compound ◽  
The Other ◽  
Asymmetric Unit ◽  
Chiral Molecules ◽  
Compound C ◽  
Alkaline Conditions ◽  
The Absolute ◽  
Absolute Structure

The title compound, C29H44O2, was formed by treatment of 11-oxooleanolic acid under strong alkaline conditions. The absolute structure of the chiral molecules could not be determined reliably from the diffraction data, but is known from other triterpenes. The asymmetric unit consists of two molecules, 1 and 2. In both molecules, ringsAandBshow chair conformations. The other rings show mixed forms between envelope and half-chair conformations with atoms in positions 8, 15 and 21 forming the flaps in ringsC,DandE, respectively. RingsDandEof molecule 2 are disordered over two orientations, with occupancies of 0.557 (4) and 0.443 (4), which differ in the direction of the flap in ringE. In the crystal, molecules 1, as well as the molecules 2, are linked by O—H...O hydrogen bonds, forming chains parallel to thebaxis.

scholarly journals Bis(pyrrolidinium) hexachloridostannate: a redetermination

IUCrData ◽  
2018 ◽  
Vol 3 (10) ◽  
Author(s):  
Kazuma Gotoh ◽  
Hiroyuki Ishida
Keyword(s):  
Crystal Structure ◽  
Room Temperature ◽  
Octahedral Geometry ◽  
The Other ◽  
Mirror Plane ◽  
Site Symmetry ◽  
Special Position ◽  
Compound C ◽  
Twist Conformation ◽  
Cl Atoms

The crystal structure of the title compound, (C4H10N)2[SnCl6], has been redetermined at 180 K. All atoms were located with higher precision than the previous structure determined at room temperature [Ishida et al. (2000). J Mol. Struct. 524, 95–103]. In the crystal, the SnIV atom is located on a special position of site symmetry 2/m and is coordinated by six Cl atoms in a pseudo-octahedral geometry. Of the six Cl atoms, two equivalent axial atoms lie on the mirror plane [Sn—Cl = 2.4281 (6) Å] and the other four equivalent equatorial atoms lie on general positions [Sn—Cl = 2.4285 (4) Å]. The N atom of the pyrrolidinium cation lies on a mirror plane and the other atoms of the cation are disordered over two sites with respect to the mirror plane. Each component of the disordered five-membered rings adopts a twist conformation. The cations and anions are connected via N—H...Cl hydrogen bonds, forming a tape-like structure propagating along [010].

scholarly journals (2S,3S,4R,4a'R,5R,5a'R,11a'R,12′S,12a'R)-5-(Acetoxymethyl)-2′,2′,10′,10′-tetramethyloctahydro-3H,8′H-spiro[furan-2,7′-[1,3]dioxino[4′,5′:5,6]pyrano[3,2-d][1,3,6]trioxocine]-3,4,12′-triyl triacetate

IUCrData ◽  
2019 ◽  
Vol 4 (7) ◽  
Author(s):  
H. E. Bollard ◽  
M. G. Banwell ◽  
J. S. Ward
Keyword(s):  
Crystal Structure ◽  
Structure Analysis ◽  
Absolute Configuration ◽  
Title Compound ◽  
Resonant Scattering ◽  
Crystal Structure Analysis ◽  
Compound C ◽  
Synthetic Derivative

While the crystal structure analysis of the title compound, C26H38O15, a synthetic derivative of sucrose, was originally reported 40 years ago [Drew et al. (1979). Carbohydr. Res. 71, 35–42], the present work has allowed for the determination of its absolute configuration through the application of resonant scattering techniques.

scholarly journals Redetermined structure of oxaline: absolute configuration using Cu Kα radiation

2012 ◽  
Vol 68 (6) ◽  
pp. o1626-o1626 ◽  
Author(s):  
Peng Qu ◽  
Zhi-Yong Wu ◽  
Wei-Ming Zhu
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Dihedral Angle ◽  
Absolute Configuration ◽  
Title Compound ◽  
Three Dimensional ◽  
Compound C ◽  
Dimensional Network ◽  
Absolute Structure ◽  
Atomic Coordinates

In the title compound, C24H25N5O4, the stereogenic C atom bonded to three N atoms and one C atom has an S configuration and its directly bonded neighbour has an R configuration. An intramolecular N—H...O hydrogen bond supports the near coplanarity of the two C3N2-five-membered rings [dihedral angle = 5.64 (10)°]. In the crystal, molecules are linked by N—H...N hydrogen bonds, forming a C(8) chain propagating in [001]. The chains are connected by C—H...O interactions, generating a three-dimensional network. The previous study [Nagel et al. (1974). Chem. Commun. pp. 1021–1022] did not establish the absolute structure and no atomic coordinates were published or deposited.

The perchlorotriphenylmethyl (PTM) radical

2013 ◽  
Vol 69 (3) ◽  
pp. 255-257 ◽  
Author(s):  
Judith Guasch ◽  
Xavier Fontrodona ◽  
Imma Ratera ◽  
Concepció Rovira ◽  
Jaume Veciana
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Diffraction Data ◽  
The Other ◽  
X Ray Diffraction ◽  
Monoclinic Symmetry ◽  
Steric Strain ◽  
High Chemical ◽  
X Ray ◽  
Cl Atoms

In spite of the considerable understanding and development of perchlorotriphenylmethyl (PTM) radical derivatives, the preparation of crystals of the pure unsubstituted PTM radical, C19Cl15, suitable for single-crystal X-ray diffraction has remained a challenge since its discovery, and only two studies dealing with the crystal structure of the unsubstituted PTM radical have been published. In one study, the radical forms clathrates with aromatic solvents [Veciana, Carilla, Miravitlles & Molins (1987).J. Chem. Soc. Chem. Commun.pp. 812–814], and in the other the structure was determinedab initiofrom powder X-ray diffraction data [Rius, Miravitlles, Molins, Crespo & Veciana (1990).Mol. Cryst. Liq. Cryst.187, 155–163]. We report here the preparation of PTM crystals for single-crystal X-ray diffraction and their resolution. The structure, which shows monoclinic symmetry (C2/c), revealed a nonsymmetric molecular propeller conformation (D3symmetry) caused by the steric strain between theortho-Cl atoms, which protect the central C atom (sp2-hybridization and major spin density) and give high chemical and thermal persistence to the PTM. The supramolecular structure of PTM shows short Cl...Cl intermolecular interactions and can be described in terms of layers formed by rows of molecules positioned in a head-to-tail manner along thecaxis.

scholarly journals Crystal structure of an epoxysterol: 9α,11α-epoxy-5α-cholest-7-ene-3β,5,6α-triol 3,6-diacetate

2017 ◽  
Vol 73 (11) ◽  
pp. 1603-1606
Author(s):  
Vincenzo Piccialli ◽  
Angela Tuzi ◽  
Roberto Centore
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Title Compound ◽  
Alkyl Chain ◽  
Resonant Scattering ◽  
Crystal Form ◽  
Epoxy Ring ◽  
Compound C ◽  
Ring Molecules ◽  
Absolute Structure

The title compound, C31H48O6, is a polyoxygenated epoxy steroid obtained by a multi-step synthesis involving oxidation of 7-dehydrocholesterol. It crystallizes in theP212121space group; however, the absolute structure of the molecule in the crystal could not be determined by resonant scattering. The configuration at the C5 and C6 positions is in both cases of the α-type, as is that of the C atoms of the epoxy ring. Molecules in the crystal form chains parallel to thebaxis by hydrogen bonding between O—H donors and carbonyl O-atom acceptors. Some atoms of the alkyl chain are disordered over two orientations, with a refined occupancy ratio of 0.511 (10):0.489 (10).

scholarly journals Absolute structure of (3aS,5S,7aS,7bS,9aR,10R,12aR,12bS)-7b-hydroxy-4,4,7a,9a,12a-pentamethyl-10-[(2′R)-6-methylheptan-2-yl]-2,8,9-trioxooctadecahydrobenzo[d]indeno[4,5-b]azepin-5-yl acetate from 62-year-old crystals

2019 ◽  
Vol 75 (9) ◽  
pp. 1348-1351
Author(s):  
Leopoldo Suescun ◽  
Horacio Heinzen
Keyword(s):  
Data Collection ◽  
Title Compound ◽  
Room Temperature ◽  
Crystal Morphology ◽  
Van Der Waals Interactions ◽  
Short Axis ◽  
Compound C ◽  
New Instrument ◽  
Absolute Structure

The structure of the title compound, C32H51NO6, was determined from 62-year-old crystals at room temperature and refined with 100 K data in a monoclinic (C2) space group. This compound with a triterpenoid structure, now confirmed by this study, played an important role in the determination of the structure of lanosterol. The molecules pack in linear O—H...O hydrogen-bonded chains along the short axis (b), while parallel chains display weak van der Waals interactions that explain the needle-shaped crystal morphology. The structure exhibits disorder of the flexible methylheptane chain at one end of the main molecule with a small void around it. Crystals of the compounds were resistant to data collection for decades with the available cameras and Mo Kα radiation single-crystal diffractometer in our laboratory until a new instrument with Cu Kα radiation operating at 100 K allowed the structure to be solved and refined.

scholarly journals (1S,3R,8R,11S)-2,2,11-Tribromo-10-bromomethyl-3,7,7-trimethyltricyclo[6.4.0.01,3]dodec-9-ene

IUCrData ◽  
2016 ◽  
Vol 1 (5) ◽  
Author(s):  
Abdoullah Bimoussa ◽  
Aziz Auhmani ◽  
My Youssef Ait Itto ◽  
Jean-Claude Daran ◽  
Abdelwahed Auhmani
Keyword(s):  
Hydrogen Bonds ◽  
Essential Oil ◽  
Absolute Configuration ◽  
Title Compound ◽  
Resonant Scattering ◽  
Cedrus Atlantica ◽  
Compound C ◽  
The Absolute

The title compound, C16H22Br4, was synthesized in two steps from β-himachalene, which was isolated from essential oil of the Atlas cedar (cedrus atlantica). It is built up from three fused rings, a seven-membered heptane ring, a six-membered cyclohexyl ring bearing both a bromine and a bromomethyl substituent, and a three-membered propane ring bearing two Br atoms. In the crystal, molecules are linked by C—H...Br hydrogen bonds, forming chains propagating along [001]. The absolute configuration was deduced from the chemical pathway and confirmed by resonant scattering [Flack parameter = 0.012 (10)].

scholarly journals Crystal structure and absolute configuration of preaustinoid A1

2015 ◽  
Vol 71 (8) ◽  
pp. o596-o597 ◽  
Author(s):  
Andrea Stierle ◽  
Donald Stierle ◽  
Daniel Decato
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Detailed Analysis ◽  
Absolute Configuration ◽  
Title Compound ◽  
Resonant Scattering ◽  
Chair Conformation ◽  
Boat Conformation ◽  
Nmr Data ◽  
Absolute Structure

The absolute structure of the title compound preaustinoid A1 [systematic name: (5aR,7aS,8R,10S,12R,13aR,13bS)-methyl 10-hydroxy-5,5,7a,10,12,13b-hexamethyl-14-methylene-3,9,11-trioxohexadecahydro-8,12-methanocycloocta[3,4]benzo[1,2-c]oxepine-8-carboxylate], C26H36O7, has been determined by resonant scattering using CuKα radiation [Flack parameter = 0.07 (15)]. The structure is consistent with that reported previously [Stierleet al.(2011).J. Nat. Prod.74, 2272–2277], determined by detailed analysis of MS and NMR data. The molecule consists of a fused four-ring arrangement. The seven-membered oxepan-2-one ring has a chair conformation, as do the central cyclohexane rings, while the outer cyclohexa-1,3-dione ring has a boat conformation. In the crystal, molecules are linkedviaO—H...O hydrogen bonds, forming helical chains propagating along [100].

scholarly journals 1,5-Dichloro-1,1,2,2,3,3,4,4,5,5-decaphenylpentasilane

IUCrData ◽  
2016 ◽  
Vol 1 (11) ◽  
Author(s):  
Felix Neumeyer ◽  
Leyla Kotil ◽  
Norbert Auner ◽  
Michael Bolte
Keyword(s):  
Title Compound ◽  
Ring Opening ◽  
The Other ◽  
Torsion Angles ◽  
Compound C ◽  
Ring Opening Reaction ◽  
Cl Atoms

The title compound, C60H50Cl2Si5, was obtained by a ring-opening reaction of decaphenylcyclopentasilane. The chain of silicon atoms adopts an alltransconformation [Si—Si—Si—Si torsion angles = −156.31 (5) and −161.02 (5)°]. One of the Cl atoms is in anantiperiplanarconformation with respect to the Si chain [Cl—Si—Si—Si = −156.40 (5)°] while the other Cl substituent adopts asynclinalconformation [Si—Si—Si—Cl = 78.82 (6)°].

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