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Search Results: 1 - 10 of 8940 matches for " Gustavo Portalone "
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Solid-phase molecular recognition of cytosine based on proton-transfer reaction. Part II. supramolecular architecture in the cocrystals of cytosine and its 5-Fluoroderivative with 5-Nitrouracil
Gustavo Portalone
Chemistry Central Journal , 2011, DOI: 10.1186/1752-153x-5-51
Abstract: Reaction of cytosine (Cyt) and 5-fluorocytosine (5Fcyt) with 5-nitrouracil (Nit) in aqueous solution yielded two new products, which have been characterized by single-crystal X-ray diffraction. The products include a dihydrated molecular salt (CytNit) having both ionic and neutral hydrogen-bonded species, and a dihydrated cocrystal of neutral species (5FcytNit). In CytNit a protonated and an unprotonated cytosine form a triply hydrogen-bonded aggregate in a self-recognition ion-pair complex, and this dimer is then hydrogen bonded to one neutral and one anionic 5-nitrouracil molecule. In 5FcytNit the two neutral nucleobase derivatives are hydrogen bonded in pairs. In both structures conventional N-H...O, O-H...O, N-H+...N and N-H...N- intermolecular interactions are most significant in the structural assembly.The supramolecular structure of the molecular adducts formed by cytosine and 5-fluorocytosine with 5-nitrouracil, CytNit and 5FcytNit, respectively, have been investigated in detail. CytNit and 5FcytNit exhibit widely differing hydrogen-bonding patterns, though both possess layered structures. The crystal structures of CytNit (Dpka = -0.7, molecular salt) and 5FcytNit (Dpka = -2.0, cocrystal) confirm that, at the present level of knowledge about the nature of proton-transfer process, there is not a strict correlation between the Dpka values and the proton transfer, in that the acid/base pka strength is not a definite guide to predict the location of H atoms in the solid state. Eventually, the absence in 5FcytNit of hydrogen bonds involving fluorine is in agreement with findings that covalently bound fluorine hardly ever acts as acceptor for available Br?nsted acidic sites in the presence of competing heteroatom acceptors.Our more recent knowledge of both the detail and the variety of DNA structures themselves, and the manner in which they are recognized by regulatory proteins, mutational compounds and drugs, is starting to pave the way to more profound levels of
A redetermination of 2-nitrobenzoic acid
Gustavo Portalone
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809011830
Abstract: The crystal structure of the title compound, C7H5NO4, was first reported by Kurahashi, Fukuyo & Shimada [(1967). Bull. Chem. Soc. Jpn, 40, 1296]. It has been re-examined, improving the precision of the derived geometric parameters. The asymmetric unit comprises a non-planar independent molecule, as the nitro and the carboxy substituents force each other to be twisted away from the plane of the aromatic ring by 54.9 (2) and 24.0 (2)°, respectively. The molecules form a conventional dimeric unit via centrosymmetric intermolecular hydrogen bonds.
Cytosinium orotate dihydrate
Gustavo Portalone
Acta Crystallographica Section E , 2013, DOI: 10.1107/s1600536812049057
Abstract: The title compound, C4H6N3O+·C5H3N2O4 ·2H2O or Cyt+·Or ·2H2O, was synthesized by a reaction between cytosine (4-amino-2-hydroxypyrimidine, Cyt) and orotic acid (2,4-dihydroxy-6-carboxypyrimidine, Or) in aqueous solution. The two ions are joined by two N+—H...O (±)-(CAHB) hydrogen bonds, forming a dimer with graph-set motif R22(8). In the crystal, the ion pairs of the asymmetric unit are joined by four N—H...O interactions to adjacent dimers, forming hydrogen-bonded rings with R22(8) graph-set motif in a two-dimensional network. The formation of the three-dimensional array is facilitated by water molecules, which act as bridges between structural sub-units linked in R32(8) and R32(7) hydrogen-bonded rings. The orotate anion is essentially planar, as the dihedral angle between the planes defined by the carboxylate group and the uracil fragment is 4.0 (4)°.
Acetoguanamine N,N-dimethylformamide solvate
Gustavo Portalone
Acta Crystallographica Section E , 2008, DOI: 10.1107/s1600536808023842
Abstract: The structure of acetoguanamine (or 2,4-diamino-6-methyl-1,3,5-triazine) has been determined as the N,N-dimethylformamide solvate, C4H7N5·C3H7NO. The molecular components are associated in the crystal structure to form ribbons stabilized by three N—H...N and one N—H...O hydrogen bonds which involve NH groups as donors and the N atoms of the heterocyclic ring and the carbonyl O atom of the solvent as acceptors.
Redetermination of 2,6-dimethoxybenzoic acid
Gustavo Portalone
Acta Crystallographica Section E , 2009, DOI: 10.1107/s1600536809001408
Abstract: The crystal structure of the title compound, C9H10O4, was first reported by Swaminathan, Vimala & Lotter [Acta Cryst. (1976), B32, 1897–1900]. It has been re-examined, improving the precision of the derived geometric parameters. The asymmetric unit comprises a non-planar independent molecule, as the methoxy substituents force the carboxy group to be twisted away from the plane of the aromatic ring by 56.12 (9)°. Due to the antiplanar conformation adopted by the OH group, the molecular components do not form the conventional dimeric units, but are associated in the crystal in chains stabilized by linear O—H...O hydrogen bonds, involving the OH groups and the carbonyl O atoms, which form C(3) motifs.
A new polymorph of 2,6-dimethoxybenzoic acid
Gustavo Portalone
Acta Crystallographica Section E , 2011, DOI: 10.1107/s1600536811049075
Abstract: A new crystalline form of 2,6-dimethoxybenzoic acid, C9H10O4, crystallizing in a tetragonal unit cell has been identified during screening for co-crystals. The asymmetric unit comprises a non-planar independent molecule with a synplanar conformation of the carboxy group. The sterically bulky o-methoxy substituents force the carboxy group to be twisted away from the plane of the benzene ring by 65.72 (15)°. The carboxy group is disordered over two sites about the C—C bond [as indicated by the almost equal C—O distances of 1.254 (3) and 1.250 (3) ], the occupancies of the disordered carboxym H atoms being 0.53 (5) and 0.47 (5). In the known orthorhombic form reported by Swaminathan et al. [Acta Cryst. (1976), B32, 1897–1900], due to the antiplanar conformation adopted by the OH group, the molecular components are associated in the crystal in chains stabilized by linear O—H...O hydrogen bonds. However, in the new tetragonal polymorph, molecules form dimeric units via pairs of O—H...O hydrogen bonds between the carboxy groups.
4-Methoxybenzamidinium 2,6-dimethoxybenzoate
Gustavo Portalone
Acta Crystallographica Section E , 2012, DOI: 10.1107/s160053681105519x
Abstract: The title compound, C8H11N2O+·C9H9O4 , was synthesized by the reaction of 4-methoxybenzamidine (4-amidinoanisole) and 2,6-dimethoxybenzoic acid. The structure consists of non-planar pairs of hydrogen-bonded 4-methoxybenzamidinium cations and 2,6-dimethoxybenzoate anions. In the cation, the amidinium group is tilted by 27.94 (10)° with respect to the benzene ring. In the anion, the sterically bulky ortho-methoxy substituents force the carboxyate group to be twisted away from the plane of the benzene ring by 73.24 (6)°. The ions are further associated in the crystal into chains along the b-axis direction by intermolecular N—H...O hydrogen bonds.
Biguanidinium dichloride
Gustavo Portalone
Acta Crystallographica Section E , 2008, DOI: 10.1107/s1600536808006144
Abstract: The asymmetric unit of the title compound, C2H9N52+·2Cl , is composed of one diprotonated biguanidinium cation and two chloride anions. The diprotonated cation consists of two planar halves twisted by 36.42 (6)°. The ions are associated in the crystal structure by extensive hydrogen bonding into a three-dimensional network; the diprotonated biguanidinium cation is hydrogen bonded to the chloride anions.
Redetermination of 5-iodouracil
Gustavo Portalone
Acta Crystallographica Section E , 2008, DOI: 10.1107/s1600536807068043
Abstract: The title compound (systematic name: 2,4-dihydroxy-5-iodopyrimidine), C4H3IN2O2, which was first reported by Sternglanz, Freeman & Bugg [Acta Cryst. (1975), B31, 1393–1395], has been redetermined, providing a significant increase in the precision of the derived geometric parameters. The asymmetric unit comprises a non-planar molecule in a slightly distorted B25 boat conformation. The molecules are associated in the crystal structure to form ribbons stabilized by N—H...O hydrogen bonds which involve NH groups and two carbonyl O atoms.
Redetermination of orotic acid monohydrate
Gustavo Portalone
Acta Crystallographica Section E , 2008, DOI: 10.1107/s160053680800562x
Abstract: The crystal structure of the title compound, which is also known as vitamin B13 (systematic name: 2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylic acid monohydrate), C5H4N2O4·H2O, was reported for the first time by Takusagawa & Shimada [Bull. Chem. Soc. Jpn (1973), 46, 2011–2019]. The present redetermination provides more precise values of the molecular geometry. The asymmetric unit comprises a planar diketo tautomer and a solvent water molecule. In the crystal structure, molecules are connected by O—H...O, N—H...O and C—H...O hydrogen bonds involving NH groups, two carbonyl O atoms and the solvent water molecule.
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