Inositols: The Effect of Bulky Substituents on Conformations

2007 ◽  
Vol 60 (8) ◽  
pp. 572 ◽  
Author(s):  
Stephen J. Angyal ◽  
J. Edgar Anderson ◽  
Donald C. Craig
Keyword(s):  
Hydroxy Group ◽  
Chair Conformation ◽  
Free Hydroxy Group ◽  
Chair Form ◽  
X Ray ◽  
X Ray Crystallography

Inositols have been converted into their triphenylsilyl derivatives. In all cases only five substituents could be introduced, the remaining free hydroxy group being hindered. The derivative of myo-inositol and one of two of neo-inositol were found to be in the inverted chair conformation, but those of other inositols are in the normal chair form. The structures of two penta-substituted derivatives have been determined by X-ray crystallography.

Mononuclear and Binuclear Complexes of Platinum(0) Containing (Alkynyl)phenylsilanes

1999 ◽  
Vol 52 (1) ◽  
pp. 51 ◽  
Author(s):  
Martin A. Bennett ◽  
Christopher J. Cobley ◽  
David C. R. Hockless ◽  
Thomas Klettke
Keyword(s):  
Spectroscopic Data ◽  
Chair Conformation ◽  
Membered Ring ◽  
Binuclear Complexes ◽  
Nickel Compound ◽  
X Ray ◽  
X Ray Crystallography

Reaction of bis(cycloocta-1,5-diene)platinum(0) with the (alkynyl)phenylsilanes Ph3SiC2But, Ph2Si(C2But)2 and PhSi(C2But)3 gives, respectively, [Pt (Ph3SiC2But)2] (1b), [Pt {Ph2Si(C2But)}]2 (2b), and [Pt {PhSi(C2But)3}]2 (4b), which contain zerovalent platinum atoms coordinated by two alkyne units. Spectroscopic data indicate that (2b) and (4b) contain two PtC4 and two SiC4 tetrahedra joined at the corners. X-Ray crystallography shows that complex (4b) is isostructural and isomorphous with the known nickel analogue, two of the alkyne units being uncoordinated; the central eight-membered ring comprising two silicon, four alkyne carbon and two platinum atoms has an approximate chair conformation. In contrast, the monomer (1b) is isostructural but not isomorphous with the analogous nickel compound (1a); in the crystal there is evidence for a weak intramolecular phenyl-phenyl interaction.

Regiospecificity in the Hydroborationof 6-Hydroxyandrost-4-enes.

1997 ◽  
Vol 50 (4) ◽  
pp. 249 ◽  
Author(s):  
James R. Hanson ◽  
Peter B. Hitchcock ◽  
Mansur D. Liman
Keyword(s):  
Hydroxy Group ◽  
Tertiary Alcohol ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Face

The hydroboration of 6α- and 6β-hydroxyandrost-4-en-17-one is shown to take place predominantly on the face of the alkenetrans to the allylic hydroxy group. The regiochemistry of the reaction is also modified with the formation of some 5β,6α,17β-trihydroxy-5β-androstane from 6α-hydroxyandrost-4-en-17-one. The structure of this tertiary alcohol was established by X-ray crystallography.

A new modification of [Ag4Br4(PPh3)4]: synthesis, structure and properties

2018 ◽  
Vol 73 (10) ◽  
pp. 733-738 ◽  
Author(s):  
Xintong Han ◽  
Shanshan Mao ◽  
Chuang Li ◽  
Kesheng Shen ◽  
Xinkui Shi ◽  
...  
Keyword(s):  
Solid State ◽  
Ir Spectroscopy ◽  
Hydrogen Bonds ◽  
Elemental Analysis ◽  
Supramolecular Structure ◽  
Chair Conformation ◽  
Cyclic Voltammograms ◽  
Structure And Properties ◽  
X Ray ◽  
X Ray Crystallography

AbstractA new modification of the homometallic silver(I) cluster [Ag4Br4(PPh3)4] has been prepared and characterized by elemental analysis, UV/Vis and IR spectroscopy, and X-ray crystallography. The tetramer shows a polycyclic structure with a chair conformation. The bromine atoms adopt μ2- and μ3-bridging modes. The shortest Ag–Ag distance in the cluster is 3.159(2) Å, which indicates significant Ag–Ag interactions. A supramolecular structure is arranged by hydrogen bonds (C–H···Br). Cyclic voltammograms of the cluster indicate a quasi-reversible Ag+/Ag couple. The fluorescence properties of the ligand and the Ag(I) cluster were studied in the solid state. The emission peaks of the Ag(I) cluster are attributed to ligand-centered luminescence.

N-Glycoside Complexes of Nickel(II); Probing Carbohydrate - Transition Metal Interactions

2009 ◽  
Vol 62 (3) ◽  
pp. 265 ◽  
Author(s):  
Dale Jones ◽  
Marcelis van Holst ◽  
Shigenobu Yano ◽  
Tomoaki Tanase ◽  
Janice Aldrich-Wright
Keyword(s):  
Chelate Ring ◽  
Chair Conformation ◽  
Nickel Atom ◽  
Cd Spectra ◽  
Metal Centre ◽  
Ring Conformation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Metal Interactions ◽  
Helical Configuration

Nickel(ii) complexes prepared from d- and l-arabinose (d-ara and l-ara) and 1,2-diaminoethane (en), [Ni(en-d-ara)2](ClO4)2·2H2O 1 and [Ni(en-l-ara)2](ClO4)2·2H2O 2 (where en-d-ara is 1-((2-aminoethyl)amino)-1-deoxy-d-arabinose) were synthesized and characterized by absorption spectroscopy, circular dichroism (CD), and X-ray crystallography. The CD spectra of 1 and 2 in the d–d transition region indicate a C2 chiral configuration around the metal centre. X-ray crystallography of 1 revealed that two 1-((2-aminoethyl)amino)-1-deoxy-d-arabinose ligands coordinate to the nickel atom in nearly C2 symmetry, through the C(2) hydroxy group of the arabinose moiety and two nitrogen atoms of the diamine in a meridional mode. This results in a Λ-C2-helical configuration around the metal centre. The arabinose ring adopts the rare α-1C4 chair conformation and the carbohydrate–chelate ring conformation is δ.

scholarly journals Structural Reassignment of Koetjapic Acid following X-ray Crystallography and NMR Spectroscopy

2017 ◽  
Vol 12 (7) ◽  
pp. 1934578X1701200 ◽  
Author(s):  
Saifullah Abubakar ◽  
Vikneswaran Murugaiyah ◽  
Chin-Hoe Teh ◽  
Kit-Lam Chan
Keyword(s):  
Spectroscopic Data ◽  
Strong Support ◽  
Chair Conformation ◽  
Unit Cell Parameters ◽  
Orthorhombic Crystal ◽  
Dioic Acid ◽  
X Ray ◽  
Cell Parameters ◽  
X Ray Crystallography ◽  
First Time

The crystal structure and absolute configuration of koetjapic acid were unambiguously reassigned by X-ray crystallography with strong support from NMR spectroscopic data. The acid contained 9 quaternary carbon atoms existing as an orthorhombic crystal with a space group of P21 21 21 and unit cell parameters of a = 7.6641(2), b = 14.6844(4) and c = 23.9316(6). Ring A adopted a chair conformation, ring B has an envelope conformation, whilst ring C assumed a half-chair and D displayed a chair conformation. The absolute configurations at C1 ( R), C5 ( R), C7 ( S), C10 ( S), C13 ( R), C14 ( R), C17 ( S) and C18 ( S) were assigned for the first time. The X-ray crystal of koetjapic acid was therefore reassigned as 3,4-seco-olean-4(23),12-diene-3,30-dioic acid. A plausible biogenetic synthetic pathway for compound 1 is also proposed.

scholarly journals X-ray crystal structure of endosulfan sulfate

2019 ◽  
Vol 62 (1) ◽  
Author(s):  
Hwa-Kyung Lee ◽  
Jonghwa Lee ◽  
Junghak Lee ◽  
Joon-Kwan Moon ◽  
Jeong-Han Kim
Keyword(s):  
Crystal Structure ◽  
Three Dimensional ◽  
Energy Difference ◽  
Dimensional Structure ◽  
Endosulfan Sulfate ◽  
Chair Form ◽  
X Ray ◽  
X Ray Crystallography ◽  
Total Potential ◽  
Ms Analysis

Abstract X-ray crystallography is an important method used to confirm the three-dimensional structure of a chemical compound. In this study, the crystal structure of endosulfan sulfate was investigated. Endosulfan sulfate is the major metabolite of the insecticide endosulfan, which is composed of two stereoisomers (α and β). From GC–MS analysis, α- and β-endosulfan each gave a single peak in the endosulfan sample, but only one peak was observed for endosulfan sulfate. Interestingly, in X-ray crystallography, two conformers of endosulfan sulfate (A and B) were observed at a ratio of 2(A):1(B). A heterocyclic seven-membered ring of conformer B assumed a horizontal-chair form, differing from two twisted forms of α-endosulfan while a vertical-chair form was observed for conformer A, showing the very similar structure to β-endosulfan; this difference in conformation is caused by differing bond angles at O(1)–C(8)–C(3) and O(2)–C(9)–C(4). In space packing, two asymmetric units were obtained, and three molecules were aligned in the order of A–A–B conformers in each unit. The total potential energy of A was slightly lower (approximately 4 kcal/mol) than B, possibly resulting in the two molecules of A that exist in a rigid crystal state. However, A and B conformers should not exist at room temperature in a solution state for GC–MS analysis, likely due to the small energy difference.

The Crystal Structure of Levoglucosan Triacetate

1974 ◽  
Vol 52 (13) ◽  
pp. 2516-2521 ◽  
Author(s):  
F. Leung ◽  
R. H. Marchessault
Keyword(s):  
Crystal Structure ◽  
Chair Conformation ◽  
Crystal Data ◽  
Pyranose Ring ◽  
X Ray ◽  
X Ray Crystallography

The crystal structure of the acetylated levoglucosan (1,6-anhydro-2,3,4-triacetylglucose) was determined by X-ray crystallography. The crystal data are: P212121, a = 10.916, b = 8.318, c = 15.612 Å. It was found that the pyranose ring of the molecule has the 1C(D) chair conformation with the acetate groups occupying the axial positions. The orientation of the acetate groups with respect to the pyranose ring was discussed in conjunction with other acetylated carbohydrate structures.

Synthesis, 1H, 13C, and 29Si nuclear magnetic resonance spectra and crystal structure of trans-1,4-diphenyldecamethylcyclohexasilane

1987 ◽  
Vol 65 (2) ◽  
pp. 437-440 ◽  
Author(s):  
Kanta Kumar ◽  
Morton H. Litt ◽  
Raj K. Chadha ◽  
John E. Drake
Keyword(s):  
Crystal Structure ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Coupling Reaction ◽  
Chair Conformation ◽  
Site Symmetry ◽  
X Ray ◽  
X Ray Crystallography ◽  
Nuclear Magnetic Resonance Spectra ◽  
Phenyl Rings

The coupling reaction between PhMeSiCl2 and Me2SiCl2 in the presence of Na/K alloy resulted in a variety of phenylated permethylcyclohexasilanes of which only trans-1,4-Ph2Me10Si6 could be obtained in pure form by repeated recrystallizations. It was studied by means of nmr (1H, 13C, and 29Si) and X-ray crystallography. The crystals are monoclinic, P21/c with a = 10.105(6), b = 14.77(1), c = 9.973(6) Å, β = 94.08(5)°, V = 1485(2) Å3, and Z = 2 for 1922 unique "observed" reflections and the structure refined to an R index of 0.036. The molecule has site symmetry [Formula: see text] and the chair conformation of cyclohexane, with the two phenyl rings occupying the equatorial positions.

The cycloaddition of norbornadiene to (triphenylphosphoranediyl)aminocyclotrithiatriazene; the crystal and molecular structure of Ph3PN—S3N3•C7H8

1983 ◽  
Vol 61 (9) ◽  
pp. 2062-2067 ◽  
Author(s):  
Stephen W. Liblong ◽  
Richard T. Oakley ◽  
A. Wallace Cordes ◽  
Mark C. Noble
Keyword(s):  
Molecular Structure ◽  
Crystal And Molecular Structure ◽  
Direct Methods ◽  
Chair Conformation ◽  
Monoclinic Space Group ◽  
Frontier Orbitals ◽  
Full Matrix ◽  
X Ray ◽  
X Ray Crystallography ◽  
Kinetics Of

The reaction of norbornadiene with (triphenylphosphoranediyl)aminocyclotrithiatriazene produces the cycloadduct Ph3PN—S3N3•C7H8. The crystal and molecular structure of this compound has been determined by X-ray crystallography. Crystals of Ph3PN—S3N3•C7H8 are monoclinic, space group P21/c, a = 9.757(1), b = 15.114(1), c = 16.535(2) Å, β = 100.73(1)°, V = 2395.7(9) Å3, and Z = 4. The structure was solved by direct methods and refined by Fourier and full-matrix least-squares procedures to give a final R of 0.040 and Rw of 0.058 for 2620 observed reflections. The structure reveals that the S3N3 ring adds to norbornadiene in an exo fashion via two sulphur atoms. The S3N3 ring adopts a chair conformation with the three ligands occupying axial positions on the same side of the ring. The relative rates of this and other cycloadditions involving SN substrates and olefins are discussed in terms of the energies of the interacting frontier orbitals. The results suggest that HOMO(olefin)–LUMO(SN substrate) interactions control the kinetics of these reactions.

Syntheses of Angucyclinones Related to Ochromycinone. III. An 11-Hydroxy Isomer and Some Reduced Analogues

1999 ◽  
Vol 52 (2) ◽  
pp. 129 ◽  
Author(s):  
Tomas Rozek ◽  
Tomas Rozek ◽  
Dennis K. Taylor ◽  
Dennis K. Taylor ◽  
Edward R. T. Tiekink ◽  
...  
Keyword(s):  
Hydroxy Group ◽  
Alder Reaction ◽  
Diels Alder ◽  
X Ray ◽  
X Ray Crystallography ◽  
Diels Alder Reaction ◽  
Stereo Selectivity ◽  
Hydrolysis Of ◽  
Alder Adduct

The boron triacetate assisted Diels Alder reaction between racemic 5,5-dimethyl-3-vinylcyclohex- 2-enyl acetate and 5-hydroxynaphthoquinone yields the racemic 11-hydroxy-3,3-dimethyl-7,12-dioxo- 1,2,3,4,6,6a,7,12,12a,12b-decahydrobenzo[a]anthracen-1-yl acetate as the sole stereoisomer by regio- and stereo-selective cis endo addition. Aromatization of the Diels Alder adduct followed by hydrolysis of the acetate and oxidation of the resultant 1-hydroxy group gives the target angucyclinone, 11-hydroxy-3,3-dimethyl-1,2,3,4,7,12-hexahydrobenzo[a]anthracene-1,7,12-trione, in an overall yield of 37% from 5-hydroxynaphthoquinone. The regio- and stereo-selectivity of the Diels Alder addition is confirmed by a combination of 13C n.m.r. spectroscopy and X-ray crystallography.

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