Photochemical behavior of the drug atorvastatin in water

Atorvastatin undergoes a self-sensitized photooxygenation by sunlight in water. The main photoproducts, isolated by chromatographic techniques, have been identified by spectroscopic means. They present a lactam ring arising from an oxidation of pyrrole ring and an alkyl/aryl shift. A mechanism involving singlet oxygen addition and an epoxide intermediate is suggested.     

Thermodynamic studies on the addition of molecular oxygen to Co(II)-1,4,8,12 tetraazacyclopentadecane in aqueous solution at 25°C

Aqueous solutions containing Co²⁺ and the macrocyclic ligand 1,4,8,12-tetraazacyclopentadecane (L) are able to bind reversibly molecular oxygen to form the species Co₂L₂O ₂ ⁴⁺ between pH 5 and 7. This species at pH greater than 8 is replaced by the complex Co₂L₂O₂ (OH) ₂ ²⁺ whose concentration in the solution increases to about pH 10.5. At pH greater than 10.5, Co(II) exists totally in this -peroxobisydroxo complex. Both the above mentioned oxygenated forms suffer a relatively slow irreversible oxidation to Co(III). From oxygen binding curves, approximate values of the equilibrium constants were calculated for the addition of oxygen to CoL²⁺ to form the -peroxo and the -peroxo-bishydroxo complexes. The enthalpies of formation of this latter complex starting from both Co²⁺ or CoL²⁺ have been obtained by means of calorimetric measurements. The effects of the size of the macrocyclic ligand on the affinity and the enthalpy of oxygen binding have been considered.Presented at the sixth Italian meeting on Calorimetry and Thermal Analysis (AICAT) held in Naples, December 4–7, 1984.     

Model compounds of nylons—II : The crystal structure of N,N′-bis (β-chlorethyl)-glutaramide

The crystal structure of N,N′-bis(β-chloroethyl)-glutaramide (NNCEG) has been determined by X-ray diffraction analysis, as part of a research programme on simple model compounds for synthetic polyamides. It crystallizes in the monoclinic system, space group P2₁ Z = 2, with A = 4·941, B = 28·123, C = 4·835 Å and β = 113°53′. The structure was solved by the heavy atom method and refined to a final R value of 0·079. Each molecule forms hydrogen bonds along two directions (almost the a and the c directions with an angle close to 60°) giving rise to bidimensional layers (parallel to the ac plane with width b/2). A similar system of hydrogen bonds could be postulated for some nylons with odd number of CH₂'s between amide groups. The molecular conformation different from an all trans conformation is discussed in terms of the barriers to rotation around each bond considered by several authors. The twinning observed in most of the examined crystals is rationalized in terms of simple symmetry operations on molecular conformations of opposite chirality.     

Structural properties and dissociative fluxional motion of 2,9-dimethyl-1,10-phenanthroline in platinum(II) complexes

A dynamic 1H NMR study has been carried out on the fluxional motion of the symmetric chelating ligand 2,9-dimethyl-1,10-phenanthroline (Me2-phen) between nonequivalent exchanging sites in a variety of square-planar complexes of the type [Pt(Me)(Me2-phen)(PR3)]BArf, 1-14, (BArf = B[3,5-(CF3)2C6H3]4). In these compounds, the P-donor ligands PR3 encompass a wide range of steric and electronic characteristics [PR3 = P(4-XC6H4)3, X = H 1, F, 2, Cl 3, CF3 4, MeO 5, Me 6; PR3 = PMe(C6H5)2 7, PMe2(C6H5) 8, PMe3 9, PEt3 10, P(i-Pr)3 11, PCy(C6H5)2 12, PCy2(C6H5) 13, PCy3 14]. All complexes have been synthesized and fully characterized through elemental analysis, 1H and 31P{1H} NMR. X-ray crystal structures are reported for the compounds 8, 11, 14, and for [Pt(Me)(phen)(P(C6H5)3)]PF6 (15), all but the last showing loss of planarity and a significant rotation of the Me2-phen moiety around the N1-N2 vector. Steric congestion brought about by the P-donor ligands is responsible for tetrahedral distortion of the coordination plane and significant lengthening of the Pt-N2 (cis to phosphane) bond distances. Application of standard quantitative analysis of ligand effects (QALE) methodology enabled a quantitative separation of steric and electronic contributions of P-donor ligands to the values of the platinum-phosphorus 1J(PtP) coupling constants and of the free activation energies DeltaG++ of the fluxional motion of Me2-phen in 1-14. The steric profiles for both 1J(PtP) and DeltaG++ show the onset of steric thresholds (at cone angle values of 150 degrees and 148 degrees , respectively), that are associated with an overload of steric congestion already evidenced by the crystal structures of 11 and 14. The sharp increase of the fluxional rate of Me2-phen can be assumed as a perceptive kinetic tool for revealing ground-state destabilization produced by the P-donor ligands. The mechanism involves initial breaking of a metal-nitrogen bond, fast interconversion between two 14-electron three-coordinate T-shaped intermediates containing eta1-coordinated Me2-phen, and final ring closure. By use of the results from QALE regression analysis, a free-energy surface has been constructed that represents the way in which any single P-donor ligand can affect the energy of the transition state in the absence of aryl or pi-acidity effects.     

Mo(CO)6-Catalyzed oxidation of furan derivatives to E- and Z-enediones by cumyl hydroperoxide

E- and Z-Enediones are easily accessible by controlled oxidation of 2,5-disubstituted furans with Mo(CO)₆/cumyl hydroperoxide system. The use of t-butyl hydroperoxide, as oxygen donor, leads to the formation of 2H-pyran-3(6H)-one derivatives.     

Energy forms on conformal C1‐diffeomorphic images of the Sierpinski gasket

The energy form on a conformal C¹‐diffeomorphic image G of the Sierpinski gasket K is constructed by integrating the Lagrangian LG on G, which is given in terms of the pullback of the Lagrangian LK on K and of the differential of the diffeomorphism. The extension of this approach to the class of nested fractals is outlined. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Weighted isoperimetric inequalities on ℝn and applications to rearrangements

We study isoperimetric inequalities for a certain class of probability measures on ?ⁿ together with applications to integral inequalities for weighted rearrangements. Furthermore, we compare the solution to a linear elliptic problem with the solution to some “rearranged” problem defined in the domain {x: x₁ < α (x₂, …, x_n)} with a suitable function α (x₂, …, x_n). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural Study and Conformational Behavior of the Two Different Lipopolysaccharide O‐Antigens Produced by the Cystic Fibrosis Pathogen Burkholderia multivorans

Lipopolysaccharides (LPSs) are virulence factors expressed by Gram‐negative bacteria; they are among those mainly responsible for bacterial virulence. In this work we define the primary structure and the conformational features of the O‐chain from the LPS produced by the highly virulent clinical isolate Burkholderia multivorans strain C1576, an opportunistic human pathogen isolated in a cystic fibrosis center and causative of an outbreak with lethal outcome. We demonstrate that the LPS from this clinical isolate consists of two O‐polysaccharide chains present in different amounts and made up of repeating units, both containing deoxy sugar. Additionally, conformational studies have been performed to establish and compare the spatial arrangements of the two polysaccharides and differences in their shape have been highlighted. The comprehension of the structural and conformational features of the two repeating units may help to explain their biological significance, the molecular shape of the bacterial external surface, and the comprehension at the molecular level of the recognition mechanisms of the antibodies.     

An approach via symmetrization methods to nonlinear elliptic problems with a lower order term

In this paper we consider a class of nonlinear elliptic problems of the type