Ignez Caracelli

Crystal structure, DNA binding studies, nucleolytic property and topoisomerase I inhibition of zinc complex with 1,10-phenanthroline and 3-methyl-picolinic acid

Crystal structure analysis of the zinc complex establishes it as a distorted octahedral complex, bis(3-methylpicolinato-κ2N,O)2(1,10-phenanthroline-κ2N,N)-zinc(II) pentahydrate, [Zn(3-Me-pic)2(phen)]·5H2O. The trans-configuration of carbonyl oxygen atoms of the carboxylate moieties and orientation of the two planar picolinate ligands above and before the phen ligand plane seems to confer DNA sequence recognition to the complex. It cannot cleave DNA under hydrolytic condition but can slightly be activated by hydrogen peroxide or sodium ascorbate. Circular Dichroism and Fluorescence spectroscopic analysis of its interaction with various duplex polynucleotides reveals its binding mode as mainly intercalation. It shows distinct DNA sequence binding selectivity and the order of decreasing selectivity is ATATxa0>xa0AATTxa0>xa0CGCG. Docking studies lead to the same conclusion on this sequence selectivity. It binds strongly with G-quadruplex with human tolemeric sequence 5′-AG3(T2AG3)3-3′, can inhibit topoisomerase I efficiently and is cytotoxic against MCF-7 cell line.

Factors affecting nucleolytic efficiency of some ternary metal complexes with DNA binding and recognition domains. Crystal and molecular structure of Zn(phen)(edda)

The binding selectivity of the M(phen)(edda) (M=Cu, Co, Ni, Zn; phen=1,10-phenanthroline, edda=ethylenediaminediacetic acid) complexes towards ds(CG)(6), ds(AT)(6) and ds(CGCGAATTCGCG) B-form oligonucleotide duplexes were studied by CD spectroscopy and molecular modeling. The binding mode is intercalation and there is selectivity towards AT-sequence and stacking preference for A/A parallel or diagonal adjacent base steps in their intercalation. The nucleolytic properties of these complexes were investigated and the factors affecting the extent of cleavage were determined to be: concentration of complex, the nature of metal(II) ion, type of buffer, pH of buffer, incubation time, incubation temperature, and the presence of hydrogen peroxide or ascorbic acid as exogenous reagents. The fluorescence property of these complexes and its origin were also investigated. The crystal structure of the Zn(phen)(edda) complex is reported in which the zinc atom displays a distorted trans-N(4)O(2) octahedral geometry; the crystal packing features double layers of complex molecules held together by extensive hydrogen bonding that inter-digitate with adjacent double layers via pi...pi interactions between 1,10-phenanthroline residues. The structure is compared with that of the recently described copper(II) analogue and, with the latter, included in molecular modeling.

Preaustinoid A: a meroterpene produced by Penicillium sp.

The title meroterpene preaustinoid A (systematic name: methyl 15-hydroxy-2,6,6,10,13,15-hexamethyl-17-methylene-7,14,16-trioxotetracyclo[11.3.1.02,11.05,10]heptadecane-1-carboxylate), C26H36O6, features a fused four-ring arrangement. Three rings are in different distorted chair conformations and the other is in a distorted boat conformation. The absolute configuration was established based on [αD] = −4.97° (c = 1.10 g l−1, CH2Cl2). In the crystal, the molecules are connected into supramolecular chains via O—H⋯O hydrogen bonds.

(Z)-Ethyl 2-hydroxyimino-2-(4-nitrobenzyl)ethanoate

The title molecule, C11H10N2O6, has a Z conformation about the C=N bond of the oxime unit. There are significant twists from planarity throughout the molecule, the most significant being between the hydroxyimino and ester groups which are effectively orthogonal with an N—C—C—Ocarbonyl torsion angle of 91.4u2005(2)°. The crystal packing features oxime–benzoyl O—H⋯O contacts that lead to chains along [010] and C—H⋯O interactions also occur.

Ethyl (E)-2-methoxy-imino-2-(4-nitro-benzo-yl)acetate.

The title molecule, C12H12N2O6, features an E conformation about the oxime group. The methoxyimino and ester residues are effectively coplanar with each other (r.m.s. deviation for the nine non-H atoms = 0.127u2005Å) and almost orthogonal [with dihedral angles of 99.44u2005(13) and −77.85u2005(13)°, respectively] to the carbonyl and nitrophenyl groups which lie to either side of this central plane. The crystal structure is consolidated by C—H⋯O contacts.

Bis[(4-methyl-phen-yl)ethyn-yl] telluride.

The tellurium atom in the title bis-ethynyl telluride, Te(C9H7)2 or C18H14Te, is located on a crystallographic twofold axis, the C—Te—C angle being 92.23u2005(15)°. The dihedral angle between the rings is 87.27u2005(7)°. In the crystal structure, molecules are connected in chains parallel to the b axis and mediated by C—H⋯π interactions.

3-(1-Hydroxy-2-phenylprop-2-en-1-yl)phenol

Two independent pseudo-enantiomeric molecules comprise the asymmetric unit in the title compound, C15H14O2. While the central O—C—C—C residue approaches planarity [torsion angles = −15.8u2005(3) (molecule a) and 15.4u2005(3)° (molecule b)], the benzene rings are approximately orthogonal [the dihedral angles formed between the benzene rings are 62.89u2005(12) (molecule a) and 80.15u2005(12)° (molecule b)]. Two-dimensional arrays in the ab plane sustained by O—H⋯O hydrogen bonding are found in the crystal structure.

Neoaustin: a meroterpene produced by Penicillium sp.

The title meroterpene neoaustin {systematic name: (1S,2R,3S,7R,9S,11S,12R)-11-hydr-oxy-2,2,2,9,12-penta-methyl-6,15-dimethyl-ene-2,6-dihydro-13-oxaspiro-[pyran-3,5-tetra-cyclo-[7.5.1.0(1,11).0(2,7)]penta-deca-ne]-6,10,14-trione}, C(25)H(30)O(6), comprises five rings, three six-membered and two five-membered. The absolute configuration was established based on [α(D)] = +166.91° (c 1.21, CH(2)Cl(2)). In the crystal, the mol-ecules are connected into a supra-molecular helical chain via O-H⋯O hydrogen bonds reinforced by C-H⋯O contacts.

1-Benzoyl-5-phenyl-2-(propan-2-yl)-1,2,3,4-tetra­hydro­pyrimidin-4-one

The tetrahydropyrimidinone ring in the title compound, C20H20N2O2, is in a half-boat conformation with the N—C—N C atom 0.580u2005(2)u2005Å out of the plane defined by the remaining five atoms. In the crystal structure, molecules are connected into centrosymmetric dimers via N—H⋯O interactions. The dimeric aggregates are linked into supramolecular chains along the a axis via C—H⋯π interactions.

2,2,6-Trimethyl-5-[2-(4-methylphenyl)ethynyl]-4H-1,3-dioxin-4-one

The 1,3-dioxin-4-one ring in the title compound, C16H16O3, is in a half-boat conformation with the quaternary O—C(CH3)2—O atom lying 0.546u2005(1)u2005Å out of the plane defined by the remaining five atoms. The crystal structure is consolidated by C—H⋯O contacts that lead to supramolecular layers.