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.

One-pot synthesis of 5-(8-ethoxycarbonyl-1-naphthyl)-10,15,20-triphenyl porphyrin (ENTPP) and spontaneous resolution upon crystallization

2011 ◽  
Vol 15 (03) ◽  
pp. 197-201 ◽  
Author(s):  
Juanxia Yang ◽  
Jiaxun Jiang ◽  
Weiguang Fang ◽  
Xiaoxu Kai ◽  
Chuanjiang Hu ◽  
...  
Keyword(s):  
Soret Band ◽  
Ester Group ◽  
Spontaneous Resolution ◽  
Cd Spectra ◽  
One Pot ◽  
Nmr Spectrum ◽  
X Ray ◽  
X Ray Crystallography ◽  
H Nmr ◽  
Entire Structure

5-(8-ethoxycarbonyl-1-naphthyl)-10,15,20-triphenyl porphyrin (ENTPP) has been synthesized in a one-pot reaction, and the corresponding chiral crystalline samples have been obtained by spontaneous resolution. 1 H NMR spectrum suggests it is mononaphthyl substituted species and an ethyl group is over the porphyrin plane. The structure has been further confirmed by X-ray crystallography. ENTPP·C6H14 (C57H50N4O2 ): monoclinic, P21, a = 10.707(2) Å, b = 12.203(2) Å, c = 17.858(4) Å, β = 103.06(3)°, V = 2272.8(8) Å3, Z = 2. The 8-position substituent, ester group, lies above the porphyrin plane and leads to the conformational chirality. The entire structure is built up with homochiral molecules, which leads to a chiral crystal through packing in P21 space group. Circular dichroism (CD) spectra have exhibited remarkable absorptions in the Soret band region, which further confirms the homochirality of the crystalline samples.

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.

Preparation and characterization of Tl(1,2-C2H4Cl2)B(OTeF5)4: a metal complex of a least coordinating solvent and a least coordinating anion

1992 ◽  
Vol 70 (3) ◽  
pp. 726-731 ◽  
Author(s):  
Paul K. Hurlburt ◽  
Oren P. Anderson ◽  
Steven H. Strauss
Keyword(s):  
Metal Ion ◽  
Chelate Ring ◽  
Ion Solvation ◽  
Crystalline Compound ◽  
Triclinic Space Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
Solid Salt ◽  
Solvent Metal

Addition of B(OTeF5)3 to TIOTeF5 in the weakly coordinating solvents dichloromethane, 1,2-dichloroethane, and 1,1,2-trichlorotrifluoroethane produces solutions of M(solv)x+B(OTeF5)4−. When the solvent was 1,2-dichloroethane, the crystalline compound Tl(1,2-C2H4Cl2)B(OTeF5)4 was isolated and studied by X-ray crystallography: triclinic, space group [Formula: see text], a = 9.221 (4), b = 11.396(5), c = 12.538 (4) Å, α = 110.75 (3)°, β = 101.72(3)°, γ = 99.74 (3)°, Z = 2, T = −116 °C. The Tl(1,2-C2H4Cl2)+ cation contains a five-membered chelate ring with Tl—Cl distances of 3.138 (4) and 3.179 (3) Å. The metal ion is weakly bonded to four B(OTeF5)4− counterions, with nine Tl—F interactions that range from 2.950 (5) to 3.981 (8) Å. When the solvent is dichloromethane or 1,1,2-trichlorotrifluoroethane, only the unsolvated solid salt TlB(OTeF5)4 can be isolated by crystallization. This salt is thermally unstable, slowly forming TlOTeF5 and volatile B(OTeF5)3. Keywords: noncoordinating anion, noncoordinating solvent, metal ion solvation.

scholarly journals The dimensions and shapes of the furanose rings in nucleic acids

1972 ◽  
Vol 130 (2) ◽  
pp. 453-465 ◽  
Author(s):  
S. Arnott ◽  
D. W. L. Hukins
Keyword(s):  
Nucleic Acids ◽  
Model Building ◽  
Molecular Model ◽  
Relative Orientation ◽  
Ring Conformation ◽  
Mean Values ◽  
Pyrimidine Base ◽  
X Ray ◽  
X Ray Crystallography ◽  
Ring Puckering

A survey was made of the geometry of furanose rings in β-nucleotides and β-nucleosides (as monomers related to nucleic acids) for which structures have been determined by X-ray crystallography. Mean values, and estimated standard deviations from them, were calculated for bond-lengths, bond-angles and conformation-angles. For parameters with values dependent on ring-puckering, separate calculations were made for each ring type. (The rings are puckered in one of three conformations: C-2- or C-3-endo or C-3-exo; C-2-exo has not been observed.) The results were used to compute standard furanose rings with C-2-endo, C-3-endo and C-3-exo conformations for use in nucleic acid molecular model-building. The survey also showed that the only other conformation-angle in nucleotides dependent on the furanose ring conformation corresponds to the relative orientation of the purine (or pyrimidine) base and the ring.

scholarly journals Mixed Chirality α-Helix in a Stapled Bicyclic and a Linear Antimicrobial Peptide Revealed by X-Ray Crystallography

2021 ◽  
Author(s):  
stéphane Baeriswyl ◽  
Hippolyte Personne ◽  
Ivan Di Bonaventura ◽  
Thilo Köhler ◽  
Christian van Delden ◽  
...  
Keyword(s):  
Antimicrobial Peptide ◽  
Md Simulations ◽  
Isobutyric Acid ◽  
Cd Spectra ◽  
X Ray ◽  
X Ray Crystallography ◽  
Left Handed ◽  
Amino Isobutyric Acid ◽  
Α Helix ◽  
Protein Environment

<p></p><p>The peptide α-helix is right-handed when containing amino acids with L-chirality, and left-handed with D-chirality, however mixed chirality peptides generally do not form α-helices unless the non-natural residue amino-isobutyric acid is used as helix inducer. Herein we report the first X-ray crystal structures of mixed chirality α-helices in short peptides comprising only natural residues at the example of a stapled bicyclic and a linear membrane disruptive amphiphilic antimicrobial peptide (AMP) containing seven L- and four D-residues, as complexes of fucosylated analogs with the bacterial lectin LecB. The mixed chirality α-helices are superimposable to their parent homochiral α-helices and form under similar conditions as shown by CD spectra and MD simulations but are resistant to proteolysis. The observation of mixed chirality α-helix with only natural residues in the protein environment of LecB suggests a vast unexplored territory of α-helical mixed chirality sequences and their possible use for optimizing bioactive α-helical peptides.</p><br><p></p>

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.

Conformational transformation coupled with the order–disorder phase transition in 2-methyl-1,3-cyclohexanedione crystals

2000 ◽  
Vol 56 (5) ◽  
pp. 872-881 ◽  
Author(s):  
Andrzej Katrusiak
Keyword(s):  
Phase Transition ◽  
Chair Conformation ◽  
Continuous Phase ◽  
Conformational Transformation ◽  
X Ray Diffraction ◽  
Ring Conformation ◽  
X Ray ◽  
Disorder Phase Transition ◽  
Methylene Groups ◽  
Large Amplitude Vibrations

The half-chair conformation of the dynamically disordered molecular ring of 2-methyl-1,3-cyclohexanedione, C_7H_{10}O_2, transforms to a sofa below T_c = 244 K, when the crystal undergoes a continuous phase transition induced by the onset of halting large-amplitude vibrations of methylene groups C(4)H_2 and C(5)H_2. The temperature dependence of the crystal structure has been investigated by X-ray diffraction. The Ibam symmetry of the crystal reduces below T_c to space group Pccn. The mechanism of the phase transition and of the conversion of the ring conformation is discussed.

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.

DNA polymorphism in crystals: three stable conformations for the decadeoxynucleotide d(GCATGCATGC)

2016 ◽  
Vol 72 (6) ◽  
pp. 780-788 ◽  
Author(s):  
Arunachalam Thirugnanasambandam ◽  
Selvam Karthik ◽  
Gunanithi Artheswari ◽  
Namasivayam Gautham
Keyword(s):  
Metal Ion ◽  
Helical Structure ◽  
Mixed Population ◽  
Helical Conformation ◽  
Cd Spectra ◽  
X Ray ◽  
X Ray Crystallography ◽  
Double Helical Structure ◽  
Flexible Molecule ◽  
Dna Fragment

High-resolution structures of DNA fragments determined using X-ray crystallography or NMR have provided descriptions of a veritable alphabet of conformations. They have also shown that DNA is a flexible molecule, with some sequences capable of adopting two different structures. Here, the first example is presented of a DNA fragment that can assume three different and distinct conformations in crystals. The decanucleotide d(GCATGCATGC) was previously reported to assume a single-stranded double-fold structure. In one of the two crystal structures described here the decamer assumes both the double-fold conformation and, simultaneously, the more conventional B-type double-helical structure. In the other crystal the sequence assumes the A-type double-helical conformation. These results, taken together with CD spectra, which were recorded as the decamer was titrated against four metal ions and spermine, indicate that the molecule may exist as a mixed population of structures in solution. Small differences in the environmental conditions, such as the concentration of metal ion, may decide which of these crystallizes out. The results also support the idea that it may be possible for DNA to change its structure to suit the binding requirements of proteins or drugs.

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.

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