Total assignment of the 13C spectrum of taraxasteryl acetate by 13C–13C connectivity experiments and determination of the stereochemistry of taraxasterol by X-ray diffraction

1985 ◽  
Vol 63 (5) ◽  
pp. 1048-1054 ◽  
Author(s):  
William F. Reynolds ◽  
Jeffery F. Sawyer ◽  
Raúl G. Enriquez ◽  
Laura I. Escobar ◽  
Marco A. Chavez ◽  
...  
Keyword(s):  
Coupling Constants ◽  
Boat Conformation ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Chair Form ◽  
X Ray ◽  
Ethanol Solvate ◽  
Similar Conformation ◽  
Spectral Assignment

13C–13C connectivity (INADEQUATE) experiments have been used to reassign the 13C spectrum of taraxasteryl acetate. This shows that there were ten errors in an earlier 13C spectral assignment for this compound. An X-ray diffraction investigation of taraxasterol shows that ring E adopts a slightly distorted boat conformation. It is suggested that severe steric interactions in the chair form force it to adopt this unusual conformation. On the basis of the 1H–1H coupling constants, it is concluded that taraxasteryl acetate adopts a very similar conformation in solution. Crystals of taraxasterol–ethanol solvate are orthorhombic, space group P21,21,21, wih a = 7.447(1) Å, b = 17.637(2) Å, c = 22.269(4) Å, U = 2925 Å3, and Dcalc = 1.07 g cm−3 for Z = 4.

Crystal structure determination of the conformation of two bicyclo[3.3.1]nonan-ones

1985 ◽  
Vol 63 (6) ◽  
pp. 1166-1169 ◽  
Author(s):  
John F. Richardson ◽  
Ted S. Sorensen
Keyword(s):  
Crystal Structure ◽  
Direct Methods ◽  
Chair Conformation ◽  
Molecular Structures ◽  
Boat Conformation ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Final Agreement

The molecular structures of exo-7-methylbicyclo[3.3.1]nonan-3-one, 3, and the endo-7-methyl isomer, 4, have been determined using X-ray-diffraction techniques. Compound 3 crystallizes in the space group [Formula: see text] with a = 15.115(1), c = 7.677(2) Å, and Z = 8 while 4 crystallizes in the space group P21 with a = 6.446(1), b = 7.831(1), c = 8.414(2) Å, β = 94.42(2)°, and Z = 2. The structures were solved by direct methods and refined to final agreement factors of R = 0.041 and R = 0.034 for 3 and 4 respectively. Compound 3 exists in a chair–chair conformation and there is no significant flattening of the chair rings. However, in 4, the non-ketone ring is forced into a boat conformation. These results are significant in interpreting what conformations may be present in the related sp2-hybridized carbocations.

Determination of the Crystal Structure and Redefinition of Tsugaruite, Pb28As15S50Cl, the First Lead-Arsenic Chloro-Sulfosalt

2020 ◽  
Author(s):  
Cristian Biagioni ◽  
Luca Bindi ◽  
Koichi Momma ◽  
Ritsuro Miyawaki ◽  
Yoshitaka Matsushita ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Atomic Ratio ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Specific Position ◽  
Actual Classification ◽  
Aomori Prefecture

Abstract Tsugaruite was originally defined as a lead-arsenic sulfosalt from the Yunosawa mine, Aomori Prefecture, Japan. Until recently its crystal structure remained unsolved and its actual classification in the sulfosalt realm was unknown. Here the refinement of the crystal structure of tsugaruite using single-crystal X-ray diffraction data is reported. The mineral is orthorhombic, space group P2nn, with unit-cell parameters a = 8.0774(10), b = 15.1772(16), c = 38.129(4) Å, V = 4674.3(9) Å3, in agreement with previous studies. The solution of the crystal structure of this mineral revealed Cl occupying a specific position. Chlorine was thus sought and found using the electron microprobe; the average of six spot analyses gave (in wt.%): Pb 68.04, As 12.83, S 18.29, Cl 0.63, total 99.80. The empirical formula, calculated on the basis of Pb + As = 43 atoms per formula unit, is Pb28.26As14.74S49.08Cl1.52. Tsugaruite is an N = 4 plesiotypic derivative of the homologous series of Pb-Sb chloro-sulfosalts having the general formula Pb(2+2N)(Sb,Pb)(2+2N)S(2+2N)(S,Cl)(4+2N)ClN. It has a Cl/(Cl + S) atomic ratio close to that of other known Pb-Sb chloro-sulfosalts (pillaite, pellouxite) and slightly higher than that of dadsonite.

The X-Ray Crystal Structure of 1,2-3,4-Di-O-isopropylidene-4-C-methylthiomethoxy-β-L-arabino-hexoseptanos-5-ulose

1990 ◽  
Vol 43 (12) ◽  
pp. 2083 ◽  
Author(s):  
DC Craig ◽  
VJ James ◽  
JD Stevens
Keyword(s):  
Crystal Structure ◽  
Title Compound ◽  
Membered Ring ◽  
Boat Conformation ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray

The crystal structure of the title compound (1) has been determined by X-ray diffraction. Crystals of (1) are orthorhombic, space group P21212 with a 11.425(1), b 24.916(1), c 5.8952(3)Ǻ, Z 4. Refinement on 1675 observed reflections measured with Cu Kα radiation converged at R 0.034. The seven- membered ring adopts a boat conformation in which the pseudo plane of symmetry passes through the ring oxygen.

Ab initiostructure determination of the Γ form ofD-sorbitol (D-glucitol) by powder synchrotron X-ray diffraction

2004 ◽  
Vol 37 (5) ◽  
pp. 766-772 ◽  
Author(s):  
Mwaffak Rukiah ◽  
Jacques Lefebvre ◽  
Olivier Hernandez ◽  
Wouter van Beek ◽  
Michel Serpelloni
Keyword(s):  
Monte Carlo ◽  
Simulated Annealing ◽  
Interatomic Bond ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Rietveld Refinements ◽  
X Ray ◽  
Monte Carlo Simulated Annealing ◽  
Starting Model

A high-resolution powder synchrotron X-ray diffraction pattern of the Γ form of D-sorbitol has been recorded at 293 K on the BM1B beamline at the ESRF (Grenoble). The starting model of the structure was found by Monte Carlo simulated annealing. The final structure was obtained through Rietveld refinements performed with soft restraints on interatomic bond lengths and angles. The symmetry is orthorhombic, space groupP21212, with 12 molecules within the cell [a= 24.3012 (2),b= 20.5726 (2),c= 4.8672 (1) Å,V= 2433.30 (3) Å3,Z′ = 3, 36 non-H independent atoms]. Crystalline cohesion between neighbouring molecules is achieved by three networks of O—H...O hydrogen bonds. The width of the Bragg peaks is interpreted through a microstructural approach in terms of anisotropic strain effects.

Crystal Structure of Dibromo(η4-1,5-cyclooctadiene)palladium(II)

1996 ◽  
Vol 61 (9) ◽  
pp. 1335-1341 ◽  
Author(s):  
Petr Štěpnička ◽  
Ivana Císařová
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Single Crystal ◽  
Boat Conformation ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Space Group ◽  
X Ray ◽  
Square Planar ◽  
Twisted Boat

The crystal structure of [(η4-C8H12)PdBr2] has been determined by a single crystal X-ray diffraction with R = 3.82% for 2 147 independent diffractions. The compound crystallizes with the symmetry of orthorhombic space group P212121 (No. 19) within the following parameters: a = 7.0785(5) Å, b = 11.1896(9) Å, c = 12.514(1) Å, V = 991.2(1) Å3, Z = 4. The square planar arrangement of ligands around Pd(II) is distorted due to the steric requirements of 1,5-cyclooctadiene in a twisted boat conformation. Formula units are joined by the weak C2-H2...Br1(1 + x, y, z) hydrogen bonds.

Structural Studies on Catalysts and Catalyst Precursors. II. The X-Ray Structure Determination of Chloro(Pentante-2,4-dithionato)(tributylphosphine)nickel(II), Ni(sacsac)(PBu3)Cl

1985 ◽  
Vol 38 (3) ◽  
pp. 369 ◽  
Author(s):  
KJ Cavell ◽  
DG Hay ◽  
AF Masters ◽  
GA Williams
Keyword(s):  
Structural Studies ◽  
Donor Atom ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Apical Position ◽  
X Ray ◽  
Butyl Group ◽  
Atom Bond

The preparation and characterization of Ni( sacsac )(PBu3) Cl by single crystal X-ray diffraction [refined to R 0.052, R? 0.042 with 1325 data having I ≥ 3σ(I)], are reported. The compound crystallizes as discrete molecules in the orthorhombic space group P bca, with a 15.526(4), b 15.774(4), c 18.377(8)Ǻ, U 4500.7 Ǻ3, and Z 8. The nickel-donor atom bond distances are Ni-S (trans Cl ) 2.097(3), Ni-S (trans P) 2.138(3), Ni- Cl 2.216(3) and Ni-P 2.237(3)Ǻ, with the ligands subtending angles S-Ni-S 98.6(1), S-Ni- Cl 85.4(1), S-Ni-P 89.5(1) and Cl -Ni-P 86.8(1). The coordination about the nickel(II) centre is planar; however, one butyl group of the phosphine is oriented so that a hydrogen is directed towards the apical position of the nickel. The structure is correlated with the N.M.R . spectra in both solid and solution phases and compared with the structures of related com- pounds. The Ni-S bonds are shown to be short and the Ni-P bond long relative to such dimensions in comparable compounds.

Carbonyliron-Lead Complexes: Multinuclear Magnetic Resonance Study in Solution and X-Ray Structure Determination of [Et2PbFe(CO)4]2

1994 ◽  
Vol 49 (12) ◽  
pp. 1781-1788 ◽  
Author(s):  
Max Herberhold ◽  
Volker Tröbs ◽  
Wolfgang Milius ◽  
Bernd Wrackmeyer
Keyword(s):  
Magnetic Resonance ◽  
Structure Determination ◽  
2D Nmr ◽  
Coupling Constants ◽  
Resonance Spectroscopy ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Geminal Coupling ◽  
Multinuclear Magnetic Resonance

Complexes of the types R3Pb-Fe(CO)2Cp [R=Me (a). Et (1b), iPr (lc), iBu (Id)]. R2Pb[Fe(CO)2Cp]2 [R=Me (2a), Et (2b)], iPr2(Br)Pb-Fe(CO)2Cp (3c) and [R2PbFe(CO)4]2 [R=Me (4a), Et (4b). iPr (4c)], as well as the spiro-complexes Pb[Fe(CO)4PbR2]2 [R = Me (5a). Et (5b). iPr (5c)] and Pb[Fe(CO)4]4 (6) were studied by multinuclear magnetic resonance spectroscopy (1H. 13C, 207Pb NMR). For the first time, coupling constants 1J(207Pb57Fe) were determined, covering a range between 33.5 (6) and 117 Hz (4a). The magnitude of the geminal coupling constants ∣2J(207Pb207Pb) ∣ in the spiro-compounds 5 decreases from 1090.0 Hz (5a) to 377.0 Hz (5c). The signs of the coupling constants nJ(207Pb13C(R)) (n = 1, 2) and nJ(207Pb1H(R)) (n = 2, 3) were determined by various 2D NMR experiments. Among all known Pb(IV) compounds the lowest 207Pb nuclear magnetic shielding was found in Pb[Fe(CO)4]4 (6): δ207Pb +3586.6. According to the single crystal X-ray structure determination of 4b (orthorhombic; space group Pbca; a = 967.4, b = 1367.7, c = 1772.4 pm), the Pb2Fe2 ring is planar with bond angles FePbFe = 102.8° and PbFePb = 77.2°, and there is a relatively short transannular distance of 340.8 pm between the two lead atoms.

Structure determination of phase II of the antifungal drug griseofulvin by powder X-ray diffraction

2018 ◽  
Vol 74 (3) ◽  
pp. 321-324 ◽  
Author(s):  
Aurélien Mahieu ◽  
Jean-François Willart ◽  
Mathieu Guerain ◽  
Patrick Derollez ◽  
Florence Danéde ◽  
...  
Keyword(s):  
Phase Ii ◽  
Structural Model ◽  
Interatomic Bond ◽  
Antifungal Drug ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Pxrd Pattern ◽  
X Ray ◽  
Monte Carlo Simulated Annealing

Two new crystalline polymorphs of the widely used antifungal drug griseofulvin (phases II and III), which originate from the crystallization of the melt, have been detected recently. The crystal structure of phase II of griseofulvin {systematic name: (2S,6′R)-7-chloro-2′,4,6-trimethoxy-6′-methyl-3H,4′H-spiro[1-benzofuran-2,1′-cyclohex-2-ene]-3,4′-dione}, C17H17ClO6, has been solved by powder X-ray diffraction (PXRD). The PXRD pattern of this new phase was recorded at room temperature using synchrotron radiation. The starting structural model was generated by a Monte Carlo simulated annealing method. The final structure was obtained through Rietveld refinement with soft restraints for interatomic bond lengths and angles, except for the aromatic ring, where a rigid-body constraint was applied. The symmetry is orthorhombic (space groupP212121) and the asymmetric unit contains two molecules.

scholarly journals Investigation of the role of stereoelectronic effects in the conformation of piperidones by NMR spectroscopy and X-ray diffraction

2015 ◽  
Vol 11 ◽  
pp. 1973-1984 ◽  
Author(s):  
Cesar Garcias-Morales ◽  
David Ortegón-Reyna ◽  
Armando Ariza-Castolo
Keyword(s):  
Density Functional ◽  
Pulse Sequence ◽  
Lone Pair ◽  
Chair Conformation ◽  
Intramolecular Interactions ◽  
Coupling Constants ◽  
Boat Conformation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Stereoelectronic Effects

This paper reports the synthesis of a series of piperidones 1–8 by the Mannich reaction and analysis of their structures and conformations in solution by NMR and mass spectrometry. The six-membered rings in 2,4,6,8-tetraphenyl-3,7-diazabicyclo[3.3.1]nonan-9-ones, compounds 1 and 2, adopt a chair–boat conformation, while those in 2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9-ones, compounds 3–8, adopt a chair–chair conformation because of stereoelectronic effects. These stereoelectronic effects were analyzed by the 1 J C–H coupling constants, which were measured in the 13C satellites of the 1H NMR spectra obtained with the hetero-dqf pulse sequence. In the solid state, these stereoelectronic effects were investigated by measurement of X-ray diffraction data, the molecular geometry (torsional bond angles and bond distances), and inter- and intramolecular interactions, and by natural bond orbital analysis, which was performed using density functional theory at the ωB97XD/6311++G(d,p) level. We found that one of the main factors influencing the conformational stability of 3–8 is the interaction between the lone-pair electrons of nitrogen and the antibonding sigma orbital of C(7)–Heq (nN→σ*C–H(7)eq), a type of hyperconjugative interaction.

scholarly journals Determination of the relative configuration of tropinone and granatanone aldols by using TBDMS ethers

2012 ◽  
Vol 8 ◽  
pp. 1877-1883 ◽  
Author(s):  
Ryszard Lazny ◽  
Aneta Nodzewska ◽  
Katarzyna Sidorowicz ◽  
Przemyslaw Kalicki
Keyword(s):  
Coupling Constants ◽  
Side Chain ◽  
X Ray Diffraction ◽  
Relative Configuration ◽  
X Ray ◽  
Vicinal Coupling Constants ◽  
Nmr Data ◽  
And Shifts ◽  
Solventless Reaction

The relative configurations oftert-butyldimethylsilyl (TBDMS) ethers of all four diastereomers of the aldols of tropinone (8-methyl-8-azabicyclo[3.2.1]octan-3-one), as well as of granatanone (9-methyl-9-azabicyclo[3.3.1]nonan-3-one), were determined from NMR data, and from the observed interconversion of the diastereomers (exo,antitoendo,synandexo,syntoendo,anti). Theexoforms invert toendoisomers in the presence of silica gel. The relative configuration of a new isomer of tropinone aldol accessible synthetically through the direct solventless reaction of tropinone and benzaldehyde in the presence of water was determined asexo,synby comparison of NMR data of the aldol isomers, in particular vicinal coupling constants and shifts corresponding to the side-chain CH group, with data of related TBDMS derivatives and confirmed by single-crystal X-ray diffraction.

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