Structural Study of Dopamine Agonist Lisuride

2003 ◽  
Vol 68 (11) ◽  
pp. 2150-2158
Author(s):  
Jan Čejka ◽  
Bohumil Kratochvíl ◽  
Stanislav Böhm ◽  
Ivana Císařová ◽  
Ladislav Cvak ◽  
...  
Keyword(s):  
Total Energy ◽  
Dopamine Agonist ◽  
Ergot Alkaloid ◽  
Simplified Model ◽  
Side Chain ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Conformation Analysis ◽  
X Ray Diffraction ◽  
X Ray

One monoclinic and three orthorhombic structures of natural ergot alkaloid lisuride were solved by X-ray diffraction techniques. The conformation analysis has revealed that side chain orientations of lisuride differ significantly from those observed in related terguride (trans-dihydrolisuride). The conformation found in individual lisuride molecules corresponds to another minimum of total energy calculated by ab initio quantum-mechanical calculations for a simplified model of 3-(cyclohex-2-en-1-yl)-1,1-diethylurea.

Crystal Forms of Semisynthetic Ergot Alkaloid Terguride

2002 ◽  
Vol 67 (4) ◽  
pp. 479-489 ◽  
Author(s):  
Michal Hušák ◽  
Bohumil Kratochvíl ◽  
Ivana Císařová ◽  
Ladislav Cvak ◽  
Alexandr Jegorov ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ergot Alkaloid ◽  
Simplified Model ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
X Ray Diffraction ◽  
Torsion Angles ◽  
Crystal Forms ◽  
X Ray ◽  
Independent Molecules

Two new structures of semisynthetic ergot alkaloid terguride created by unusual number of symmetry-independent molecules were determined by X-ray diffraction methods at 150 K. Form A (monoclinic, P212121, Z = 12) contains three symmetry-independent terguride molecules and two molecules of water in the asymmetric part of the unit cell. The form CA (monoclinic, P21, Z = 8) is an anhydrate remarkable by the presence of four symmetry-independent molecules in the crystal structure. Conformations of twelve symmetry-independent molecules that were found in four already described terguride structures are compared with torsion angles obtained by ab initio quantum-mechanical calculations for the simplified model of N-cyclohexyl-N'-diethylurea.

A Simple, One-Pot Synthesis of Trans-Substituted Spiro [5,5] undecane-1,5,9-triones with Aromatic Aldehydes and Meldrum's Acid as the Starting Materials

2015 ◽  
Vol 68 (10) ◽  
pp. 1599 ◽  
Author(s):  
Jingping Ou-Yang ◽  
Yu Zhao ◽  
Huailei Jiang ◽  
Lingxin Meng ◽  
Xingshu Li ◽  
...  
Keyword(s):  
1H Nmr ◽  
Aromatic Aldehydes ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Meldrum's Acid ◽  
X Ray Diffraction ◽  
Meldrum’S Acid ◽  
Reaction Conditions ◽  
One Pot ◽  
X Ray

A simple, one-pot process for the construction of substituted spiro[5,5]undecane-1,5,9-triones using aromatic aldehydes and Meldrum’s acid, and aniline as a catalyst, is reported. Fifteen compounds were synthesized, and the trans/cis ratios were calculated based on 1H NMR analyses of the unpurified products. Quantum mechanical calculations and X-ray diffraction were undertaken to identify the configuration of compound 2a. The proposed mechanisms for these reactions are presented in this paper. In contrast to previous literature, this method endows excellent diastereoselectivity to a series of trans-substituted derivatives. The method is characterized by its simple operation, commercial availability of all materials, mild reaction conditions and moderate-to-good chemical yields.

scholarly journals Interpreting Disordered PXRD Structures using Molecular Dynamics

2014 ◽  
Vol 70 (a1) ◽  
pp. C1569-C1569
Author(s):  
Kristoffer Johansson ◽  
Xiaozhou Li ◽  
Andrew Bond ◽  
Jacco van de Streek
Keyword(s):  
Molecular Dynamics ◽  
Structural Information ◽  
Supplementary Information ◽  
Rational Approach ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Crystal Properties ◽  
Solid Form

A central topic in the formulation of solid medicinal products is the identification of a suitable solid form of an active compound to obtain optimal physicochemical properties. To this end, disorder may be important for relevant crystal properties like stability. For example, disorder may account for more than 10% of the crystal volume. A rational approach to solid-form selection is typically based on structural information at atomic resolution. In practice, pharmaceutical compounds are not always well-behaved and especially in the study of polymorphs or compounds with flexible groups it can be challenging to obtain crystals suitable for single-crystal X-ray diffraction. Powder X-ray diffraction (PXRD) is a popular alternative, but it generally requires supplementary information like molecular connectivity in simple cases or computational models to solve larger structures. Computational modeling has come a long way and accurate and reliable structures of pharmaceutically relevant compounds can indeed be obtained using laboratory PXRD measurements and quantum-mechanical calculations [1]. The major limitation of quantum mechanical calculations, however, is that they do not consider time nor temperature but only static structures at zero temperature. Thus, these methods cannot model phenomena related to disorder. The molecular dynamics (MD) method can add temperature as well as time and spatial resolution to a model and has in recent years developed to be a scalable, reliable and increasingly available technique. As more and more groups from academia as well as industry employ MD in their work, the development will increase to gain momentum in the coming years. We use MD in a high-performance setting to study crystal properties that are relevant for pharmaceutical research. Using a combination of models from first principles and MD we are able to study highly disordered structures and polymorphs on the basis of PXRD data.

scholarly journals Topology of the Electron Density and of Its Laplacian from Periodic LCAO Calculations on f-Electron Materials: The Case of Cesium Uranyl Chloride

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4227
Author(s):  
Alessandro Cossard ◽  
Silvia Casassa ◽  
Carlo Gatti ◽  
Jacques K. Desmarais ◽  
Alessandro Erba
Keyword(s):  
Electron Density ◽  
Chemical Bonding ◽  
Topological Analysis ◽  
Theoretical Description ◽  
Basis Functions ◽  
Quantum Mechanical ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Orbitals ◽  
Uranyl Chloride

The chemistry of f-electrons in lanthanide and actinide materials is yet to be fully rationalized. Quantum-mechanical simulations can provide useful complementary insight to that obtained from experiments. The quantum theory of atoms in molecules and crystals (QTAIMAC), through thorough topological analysis of the electron density (often complemented by that of its Laplacian) constitutes a general and robust theoretical framework to analyze chemical bonding features from a computed wave function. Here, we present the extension of the Topond module (previously limited to work in terms of s-, p- and d-type basis functions only) of the Crystal program to f- and g-type basis functions within the linear combination of atomic orbitals (LCAO) approach. This allows for an effective QTAIMAC analysis of chemical bonding of lanthanide and actinide materials. The new implemented algorithms are applied to the analysis of the spatial distribution of the electron density and its Laplacian of the cesium uranyl chloride, Cs2UO2Cl4, crystal. Discrepancies between the present theoretical description of chemical bonding and that obtained from a previously reconstructed electron density by experimental X-ray diffraction are illustrated and discussed.

New solvates and a salt of the anti-HIV compound etravirine

2021 ◽  
Vol 77 (11) ◽  
Author(s):  
Marieta Muresan-Pop ◽  
Sergiu Macavei ◽  
Alexandru Turza ◽  
Gheorghe Borodi
Keyword(s):  
Thermal Analysis ◽  
Ir Spectroscopy ◽  
Force Field ◽  
Single Crystal ◽  
Total Energy ◽  
Hirshfeld Surface ◽  
X Ray Diffraction ◽  
X Ray ◽  
Lattice Energies ◽  
Anti Hiv

Four new solvates of the anti-HIV compound etravirine [systematic name: 4-({6-amino-5-bromo-2-[(4-cyanophenyl)amino]pyrimidin-4-yl}oxy)-3,5-dimethylbenzonitrile, C20H15BrN6O] with dimethyl sulfoxide (C2H6OS, two distinct monosolvates), 1,4-dioxane (C4H8O2, the 0.75-solvate) and N,N-dimethylacetamide (C4H9NO, the monosolvate), which exhibit conversion to the same anhydrous etravirine phase upon desolvation, and a stable etravirinium oxalate salt {6-amino-5-bromo-4-(4-cyano-2,6-dimethylphenoxy)-2-[(4-cyanophenyl)amino]pyrimidin-1-ium hemioxalate, C20H16BrN6O+·0.5C2O4 2−} were obtained. The crystal structures were solved by single-crystal X-ray diffraction and analyzed by powder X-ray diffraction, and the intermolecular interactions were explored by Hirshfeld surface analysis. Lattice energies were evaluated using the atom–atom force field Coulomb–London–Pauli (AA CLP) approximation, which distributes the total energy as four separate contributions: Coulombic, polarization, dispersion and repulsion. The formation of the solvates and the oxalate salt was further characterized by thermal analysis and IR spectroscopy.

Are mesoionic compounds aromatic?

1998 ◽  
Vol 76 (6) ◽  
pp. 869-872 ◽  
Author(s):  
Alfredo Mayall Simas ◽  
Joseph Miller ◽  
Petrônio Filgueiras de Athayade Filho
Keyword(s):  
Experimental Evidence ◽  
Key Words ◽  
Dipole Moments ◽  
The Other ◽  
Side Chain ◽  
Theoretical Studies ◽  
X Ray Diffraction ◽  
Ring Plane ◽  
X Ray ◽  
Single Bonds

We have evaluated the experimental evidence relevant to the structure and character of mesoionic compounds, accumulated for more than 100 years and including X-ray diffraction studies. We have also evaluated relevant theoretical studies. All these, including our own extensive work, lead us to conclude that mesoionic compounds are not aromatic. According to our recent definition “mesoionic compounds are planar five-membered heterocyclic betaines with at least one side chain whose α-atom is also in the ring plane and with dipole moments of the order of 5 D. Electrons are delocalized over two regions separated by what are essentially single bonds. One region, which includes the a-atom of the side chain is associated with the HOMO and negative π-charge whereas the other is associated with the LUMO and positive π-charge.” Key words: mesoionic compounds, betaines, aromaticity.

scholarly journals NMR and X-ray studies of apetalic acid isolated from Calophyllum brasiliense and of its chiral amides

2021 ◽  
Author(s):  
Marie-Rose Van Calsteren ◽  
Ricardo Reyes-Chilpa ◽  
Chistopher K Jankowski ◽  
Fleur Gagnon ◽  
Simón Hernández-Ortega ◽  
...  
Keyword(s):  
Antimycobacterial Activity ◽  
Side Chain ◽  
Carboxyl Group ◽  
X Ray Diffraction ◽  
Rain Forests ◽  
X Ray ◽  
X Ray Crystallography ◽  
Calophyllum Brasiliense ◽  
Derivatives Of

The tropical tree Calophyllum brasiliense (Clusiaceae) grows in the rain forests from Brazil to Mexico. Its leaves, as well as those of other Calophyllum species, are rich sources of chromanone acids, such as apetalic acid, isoapetalic acid, and their derivatives. Apetalic acid has shown significant antimycobacterial activity. The biological activity of apetalic acid has been related to the configuration of three asymmetric centers and the stereochemistry of the molecule; however, the C-19 configuration in the acidic side chain has not been fully resolved. For this reason, the unequivocal determination of the absolute configuration by means of X-ray crystallography in a sample of unique homogeneous apetalic acid stereoisomer was the most important point to start this study. We prepared some chiral amides using the carboxyl group. We determined the C-19 stereochemistry of apetalic acid, and its specific chiral derivatives, using NMR, X-ray diffraction methods, and molecular mechanics. Finally, we observed that steric hindrance in the side chain of apetalic acid leads to restriction of rotation around the pivotal link C-10 and C-19 establishing chiral centers at C2(R), C3(S), and C19(R). We were able to separate derivatives of these two high-rotatory-barrier conformers of apetalic acid by forming diastereoisomeric amides with phenylglycine methyl ester having a chiral center at C-2’. Our results allowed the conclusion of the existence of atropisomerism in the apetalic acid molecule.

scholarly journals New Ternary Compounds of the Composition Cu2SnTi3 and Their Crystal Structures

2020 ◽  
Vol 10 (24) ◽  
pp. 8776
Author(s):  
Sheng-Fang Huang ◽  
Yen-Cheng Chang ◽  
Po-Liang Liu
Keyword(s):  
Crystal Structure ◽  
Total Energy ◽  
Ternary Compound ◽  
Density Functional ◽  
Hexagonal Crystal Structure ◽  
X Ray Diffraction ◽  
Hexagonal Crystal ◽  
Orthorhombic Crystal Structure ◽  
X Ray ◽  
Atomic Structures

A new ternary compound Cu2SnTi3 has been synthesized by vacuum sintering at 900 °C. The atomic structures of CaCu5- and InNi2-like Cu2SnTi3 are calculated using density functional theory methods. The X-ray diffraction (XRD) analysis and selected area diffraction (SAD) patterns of the new ternary compound Cu2SnTi3 are considered to verify the atomic structures of CaCu5- and InNi2-like Cu2SnTi3. The results reveal that the InNi2-like Cu2SnTi3 model has the lowest total energy of −35.239 eV, representing the trigonal crystal structure. The orthorhombic crystal structure of the CaCu5-like Cu2SnTi3 model has the second lowest total energy of −33.926 eV. Our theoretical X-ray diffraction peak profiles of InNi2-like (CaCu5-like) Cu2SnTi3 are nearly identical to experimental one, leading to an error below 2.0% (3.0%). In addition, the hexagonal crystal structure of the CaCu5-like Cu2SnTi3 model has the highest total energy of −33.094 eV. The stability of the Cu2SnTi3 in terms of energy follows the order: the trigonal, orthorhombic, and hexagonal crystal structure.

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