The X-Ray Crystal Structure and Photochemistry of 22-α-Hydroxystictan-3-One; a Triterpenoid Keto Alcohol From Pseudocyphellaria Species

1988 ◽  
Vol 41 (1) ◽  
pp. 143 ◽  
Author(s):  
AL Wilkins ◽  
EM Goh
Keyword(s):  
Crystal Structure ◽  
Chair Conformation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Photochemical Rearrangement ◽  
Twist Boat

The crystal structure of 22α-hydroxystictan-3-one has been determined by X-ray diffraction. Rings A and B of this keto alcohol have been shown to adopt twist boat conformations. Despite the presence of the twist boat ring A system photochemical rearrangement of the keto alcohol proceeds to give 3,4-secostictane derivatives analogous to those afforded by other 3-oxo-4,4-dimethyl steroids and triterpenoids in which ring A adopts a flattened chair conformation.

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.

The conformation of (1S,3S,4R)- 1,3,8-Tribromo-p-menthan-2-one

1983 ◽  
Vol 36 (5) ◽  
pp. 1043 ◽  
Author(s):  
RM Carman ◽  
E Horn ◽  
CHL Kennard ◽  
G Smith ◽  
MR Snow ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Diffraction Data ◽  
Boat Conformation ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
A Cell ◽  
Twist Boat

The crystal structure of (1S,3S,4R)-1,3,8-tribromo-p-menthan-2-one has been determined from X-ray diffraction data and refined to a final residual of 0.075 for 635 'observed' reflections. Crystals are orthorhombic, of space group P212121 with four molecules in a cell of dimensions a 15.248(3), b 12.189(3), c 7.201(2) �. The analysis confirms that the molecule exists in a distorted twist-boat conformation.

Tetramethyld-η2-vinyldisiloxan(triphenylphosphan)platin(0) / Tetramethyldi-η2-vinyldisiloxane(triphenylphosphine)platinum(0)

1991 ◽  
Vol 46 (12) ◽  
pp. 1694-1698 ◽  
Author(s):  
Georg Beuter ◽  
Olga Heyke ◽  
Ingo-Peter Lorenz
Keyword(s):  
Crystal Structure ◽  
Chair Conformation ◽  
Ring System ◽  
Platinum Atom ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray

The reaction of (Ph3P)2PtC2H4 with the divinyldisiloxane (CH2=CHSiMe2)2O in toluene yields Pt{(η2-H2C=CHSiMe2)2O}PPh3, which has been characterized by IR, 1H, 13C, 31P NMR and MS spectra. The crystal structure was determined by X-ray diffraction: space group C2/c, Z = 16, a = 5534.2(9), b = 842.6(2), c = 2383.1(2) pm, β = 103.73(1)°, R/Rw = 0.047/0.052. It shows a three-coordinate platinum atom with one phosphine and one sym-tetramethyldivinyldisiloxane ligand acting as a chelating bidentate η/2-ligand to give a chair conformation of the six-membered PtC2Si2O-ring system.

Crystal structures of medium ring compounds. Part III. The crystal and molecular structure of trans-anti-trans-4,5:9,10-biscyclohexano-1,3,6,8-tetraoxecane

1979 ◽  
Vol 57 (16) ◽  
pp. 2154-2158 ◽  
Author(s):  
Aris Terzis ◽  
T. Bruce Grindley
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Crystal And Molecular Structure ◽  
Chair Conformation ◽  
Membered Ring ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ring Compounds ◽  
R Value ◽  
Medium Ring

The crystal structure of trans-anti-trans-4,5:9,10-biscyclohexano-1,3,6,8-tetraoxecane (3) has been determined by X-ray diffraction. The crystals are monoclinic, a = 11.919(3), b = 17.330(7), c = 7.019(2) Å, β = 98.91(1)°, P21/c, with Z = 4. The structure was solved by application of the tangent formula and refined by large block least squares to a final R value of 0.060 (Rw = 0.058).The ten-membered ring is present in the crystal in a twist-chair-boat-chair conformation — one which has been calculated to be relatively unstable for cyclodecane. Possible reasons why 3 adopts this conformation are discussed.

The Crystal Structure of the Pyrimidine Analogue Calcium 5-Ethylidenehydroorotate · 1.5 Hydrate, a Photoproduct of Ethylorotate

1976 ◽  
Vol 31 (9-10) ◽  
pp. 518-523 ◽  
Author(s):  
B Hingerty ◽  
E Kulikowska ◽  
W Saenger ◽  
D Shugar
Keyword(s):  
Crystal Structure ◽  
Calcium Salt ◽  
Direct Methods ◽  
Water Molecules ◽  
Monoclinic Space Group ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
X Ray ◽  
Photochemical Rearrangement ◽  
Pyrimidine Analogue

Abstract X-ray diffraction methods have been employed to establish the crystal structure of a new, unusual pyrimidine analogue, 5-ethylidenehydroorotate, obtained by a photochemical rearrangement of 5-ethylorotate. Crystals of the calcium salt of the title compound are monoclinic, space group Pc, cell constants a=14.631, 6 = 10.038, c = 19.168 Å,β = 137.7°, and contain four molecules, two cations and three water molecules per asymmetric unit. The structure was solved by direct methods and refined to R = 5.2% on the basis of 2653 diffractometer measured data. The four independent molecules represent two pairs of enantiomers with slightly differing conformations linked together by an intricate system of hydrogen bonding and Ca2+-coordination (pentagonal bipyrimidal). The structure of the compound in aqueous medium, as that in the crystal.

The crystal and molecular structure of syn-[4.4.3]propella-2,4,12-trien-11-ol 3,5-dinitrobenzoate

1985 ◽  
Vol 63 (4) ◽  
pp. 862-865 ◽  
Author(s):  
Judith C. Gallucci ◽  
Katsuo Ohkata ◽  
Leo A. Paquette
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Crystal And Molecular Structure ◽  
Molecular Geometry ◽  
Chair Conformation ◽  
Membered Ring ◽  
Aqueous Acetone ◽  
X Ray Diffraction ◽  
X Ray ◽  
R Value

The crystal structure of syn-[4.4.3]propella-2,4,12-trien-11-ol 3,5-dinitrobenzoate, 2, has been determined by single crystal X-ray diffraction and refined to an R value of 0.051. The crystal structure is triclinic with a = 10.208(2), b = 13.355(2), c = 7.068(1) Å, α = 99.35(1)°, β = 100.63(1)°, γ = 100.79(1)°, and the space group is [Formula: see text] with two molecules per cell, D(calcd) = 1.39 g cm−3. The unsaturated five-membered ring resides in an envelope conformation with C6—C11—C12—C13 lying essentially in a plane. The fifth atom, C1, is positioned 0.47 Å out of this plane on the side opposite O1. The latter is situated 1.38 Å away and projects the 3,5-dinitrobenzoate group above the central portion of the cyclohexadiene unit. Four contiguous carbon atoms in the latter ring are mutually coplanar and the fused cyclohexane ring adopts a chair conformation. The overall molecular geometry is reconcilable with its solvolytic behavior in aqueous acetone.

scholarly journals Biological Activity, Structural Characterization and Crystal Packing of Chromane-Carboxylate Derivatives

2018 ◽  
Vol 11 (1) ◽  
pp. 1-5
Author(s):  
Viktor Vrábel ◽  
Július Sivýb ◽  
Jan Světlíkc ◽  
Štefan Marchalínd ◽  
Šafař Peterd
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Biological Activity ◽  
Crystal And Molecular Structure ◽  
Crystal Packing ◽  
Chair Conformation ◽  
Heterocyclic Ring ◽  
X Ray Diffraction ◽  
Compound I ◽  
X Ray

Abstract We report here the crystal and molecular structure of a new chromane-derivative, namely isopropyl( 2R*,3S*,4S*)-4-(benzo[d]thiazol-2-ylamino)-2-hydroxy-2-ethylchromane-3-carboxylate (I), C21H22N2O4S, which crystallizes as racemate in the space group C2/c. Its structure has been solved using X-ray diffraction data obtained at low temperature (100(2) K). In this compound, the chromane moiety consists of a benzene ring fused with a six-membered heterocyclic ring which adopts a distorted half-chair conformation. The molecules are linked by a combination of O-H∙∙∙N and N-H∙∙∙O hydrogen bonds, resulting in a twodimensional network which helps stabilizing the crystal structure of the compound (I). Dihedral angle between the chromane and benzothiazol rings is 80.6(1)0.

X-Ray structure analysis of methyl 2,3,4,5-Tetra-O-acetyl-α-D-galactoseptanoside

1980 ◽  
Vol 33 (5) ◽  
pp. 979 ◽  
Author(s):  
W Choong ◽  
JF McConnell ◽  
NC Stephenson ◽  
JD Stevens
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Structure Analysis ◽  
Title Compound ◽  
Chair Conformation ◽  
Membered Ring ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Full Matrix ◽  
X Ray

The crystal structure of the title compound was determined by X-ray diffraction and the use of the multi-solution programs MULTAN 74. Crystals are monoclinic, space group C2 with Z = 4 in a unit cell of dimensions: a 21.140(6), b 9.394(3), c 9.765(3) Ǻ, β 108.73(5)°. The structure was refined by full-matrix least-squares methods to a final R of 0.036 for 1858 diffractometer reflections. The seven-membered ring approximates to a twist-chair conformation very similar to that found for the gluco analogue.

scholarly journals Crystal structure of (1S,3R,8R,9R)-2,2-dichloro-3,7,7-trimethyl-10-methylenetricyclo[6.4.0.01,3]dodecan-9-ol

2016 ◽  
Vol 72 (8) ◽  
pp. 1163-1166
Author(s):  
Ahmed Benzalim ◽  
Aziz Auhmani ◽  
Abdoullah Bimoussa ◽  
My Youssef Ait Itto ◽  
Jean-Claude Daran ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Hydrobromic Acid ◽  
Cyclopropane Ring ◽  
Chair Conformation ◽  
Membered Ring ◽  
Asymmetric Unit ◽  
X Ray ◽  
Compound C ◽  
Concentrated Solution ◽  
Twist Boat

The title compound, C16H24Cl2O, was synthesized by treating (1S,3R,8S,9R,10S)-2,2-dichloro-3,7,7,10-tetramethyl-9,10-epoxytricyclo[6.4.0.01,3]dodecane with a concentrated solution of hydrobromic acid. It is built up from three fused rings: a cycloheptane ring, a cyclohexyl ring bearing alkene and hydroxy substituents, and a cyclopropane ring bearing two chlorine atoms. The asymmetric unit contains two molecules linked by an O—H...O hydrogen bond. In the crystal, further O—H...O hydrogen bonds build up anR44(8) cyclic tetramer. One of the molecules presents disorder that affects the seven-membered ring. In both molecules, the six-membered rings display a chair conformation, whereas the seven-membered rings display conformations intermediate between boat and twist-boat for the non-disordered molecule and either a chair or boat and twist-boat for the disordered molecule owing to the disorder. The absolute configuration for both molecules is 1S,3R,8R,9Rand was deduced from the chemical pathway and further confirmed by the X-ray structural analysis.

1,3-Digermapropan und 1,3,5-Trigermacyclohexan / 1,3-Digermapropane and 1,3,5-Trigermacyclohexane

1988 ◽  
Vol 43 (6) ◽  
pp. 727-732 ◽  
Author(s):  
Hubert Schmidbaur ◽  
Johann Rott ◽  
Gabriele Reber ◽  
Gerhard Müller
Keyword(s):  
Crystal Structure ◽  
Mirror Symmetry ◽  
Spectroscopic Data ◽  
Vapour Deposition ◽  
Chemical Vapour ◽  
Chair Conformation ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
X Ray ◽  
Germanium Powder

AbstractFrom the copper-catalyzed reaction of germanium powder with dichloromethane at 350 °C a mixture of alkylchlorogermanes is obtained, in which CH3GeCl3, CH2(GeCl3)2 (1) and (Cl2GeCH2)3 (2) are the major products. Treatment of 1 and 2 with LiAlH4 in di-n-butyl or diethylether, resp., affords the hydrides CH2(GeH3)2 (3) and cyclic (H2GeCH2)3 (4), the latter along with the heterocycle H2Ge(CH2GeH2)2 (5). Compounds 3-5 have been identified by analytical and spectroscopic data, and the crystal structure of 4 has been determined by single crystal X-ray diffraction. The compound crystallizes in the orthorhombic space group Pmn21, with two molecules in the unit cell (a = 8.663(1), b = 7.783(1), c = 6.124(1) Å). The molecules, which are in a chair conformation, have crystallographic mirror symmetry with bond angles slightly larger than tetrahedral and Ge-C distances of 1.944(6), 1.953(3) and 1.955(4) Å. The compounds show potential as substrates for plasma-enhanced chemical vapour deposition (PE-CVD) of amorphous germanium carbon alloys (a-Ge, C:H).

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