Claude Béguin

Effet de la concentration en acide fluorhydrique dans la pyridine sur la regio-selective de la fluoration par deamination d′α-amino-esters : syntheses de composes cargoxyles-β-fluores.

Resume Fluorodeamination of α-amino-esters with sodium nitrite in HF-pyridine gives mainly β-fluoro-esters. The molar ratio HF-pyridine is the main parameter for the α-β regioselectivity.

Biomimetic studies related to the azide-inhibited Cu,Zn superoxide dismutases

Azide binding to imidazolate-bridged dinuclear copper(II) complexes of macrocyclic (L′) and macrobicyclic (L) ligands has been investigated by EPR, UV-visible spectrophotometry and kinetics. The EPR spectra show that an azido bridge replaces the imidazolate bridge in the macrobicyclic complex while the azide anion is bound to one copper and the imidazolate bridge is broken in the macrocyclic complex. The rate constant of azide binding is very low for the complexes without labile coordination and relatively large for those with labile coordination, whatever the macrocycle or macrobicycle structure of the ligand.

An imidazolate-bridged heterobinuclear (copper–zinc) complex of a macrobicyclic ligand, a model of the active site of superoxide dismutase

The first imidazolate-bridged heterobinuclear copper–zinc complex of a unique macrobicyclic ligand (cryptand) was prepared and characterized by X-ray diffraction; the complex-catalysed dismutation of superoxide anion survives in the presence of bovine serum albumin.

Stereochemical assignment of the meridional isomer of the trisbidentate chelate complex Ga(fox)3 (fox = 5‐fluoro‐8‐hydroxyquinoline) by two‐dimensional correlated NMR

The complete assignments of all 19F, 1H and 13C resonances for the mer isomer of Ga(fox)3 (fox = 5‐fluoro‐8‐hydroxyquinoline) by analysis of scalar (COSY) and dipolar (NOESY) connectivities were demonstrated, resulting in an unambiguous structural determination of the complex under investigation. Detailed one‐ and two‐dimensional multinuclear NMR investigations were carried out to obtain the spectral patterns characteristic of the Ga(fox)3 complex. Copyright

Structure and properties of copper-(II) and -(I) complexes with 2,6-bis[2-(thiophen-2-ylmethylimino)ethyl]pyridine

Positive-ion FAB mass spectroscopy, elemental analysis, EPR spectroscopy and X-ray diffraction analysis have revealed the structure of the copper(II) complex of 1 : 2 (Cu : L) stoichiometry obtained by mixing in methanol 1 equivalent of Cu(ClO4)2·6H2O and 1 equivalent of 2,6-bis[2-(thiophen-2-ylmethylimino)ethyl]pyridine (L). The copper(II) ion is co-ordinated to six nitrogen atoms in an octahedral arrangement not involving the thiophene S atoms. The planes of the two trans pyridine subunits are perpendicular (94°); the Cu–N bond distances are 1.924 and 1.983 A for the pyridine, 2.098, 2.118 and 2.284, 2.330 A for the imine indicating slight distortion in the structure. Cyclic voltammetry in acetonitrile showed reversible behaviour for the [CuIIL2]2+-[CuIL2]+ couple, and the redox potential E was –0.61 V vs. 10 mmol dm–3 Ag–Ag+ in MeCN. Spectroscopic investigation of acetonitrile solutions having a 1 : 1 Cu : L molar ratio indicated the formation of species with 1 : 1 overall stoichiometry. The electrochemical measurements revealed that these complexes decompose during the electron transfer leading to the [CuIIL2]2+–[CuIL2]+ redox process.