Michel Momenteau

Alkane hydroxylation catalyzed by metalloporhyrins : evidence for different active oxygen species with alkylhydroperoxides and iodosobenzene as oxidants.

Abstract A comparative study of cyclohexane and n-heptane hydroxylations by cumylhydroperoxide and iodosobenzene, catalyzed by various metalloporphyrins, indicates that different active oxygen species, presumably the cumyloxy radical and a metal-oxo intermediate, are involved in these reactions.

Proton magnetic resonance characterization of the intermediate (S=1) spin state of ferrous porphyrins

The temperature dependence of the paramagnetic shifts in square planar ferrous complexes has been investigated for a number of porphyrin derivatives. Large anomalies in the Curie law have been observed in newly synthesized substituted tetraphenylporphins in which the environment of both faces of the tetrapyrrolic ring is strictly controlled. The pseudocontact and contact contributions to the measured hyperfine shifts as well as their temperature dependence have been interpreted in terms of a model with two electronic states. Following this model, the nature of the ground state of the ferrous ion depends critically upon the energy of the dz2 orbital relative to that of the degenerate dxz and dyz orbitals. For most of the porphyrin derivatives, the ground state is 3A2g, strongly perturbed by the closely lying 3Eg excited state. This strong mixing by spin–orbit coupling explains the large orbital contribution to the magnetic susceptibility of these complexes. A small axial perturbation can induce a reversal ...

Catalytic properties of iron and manganese glycoconjugated porphyrins

Abstract The catalytic properties of new family of tetrapyrrolic macrocycles containing some glycosylated groups are described. Of particular interest is the structure of the catalysts.

Oxidation of monosubstituted olefins by cytochromes P-450 and heme models: Evidence for the formation of aldehydes in addition to epoxides and allylic alcohols

Aldehydes RCH2CHO are formed in addition to epoxides and allylic alcohols upon oxidation of the monosubstituted olefins RCH=CH2, styrene and 6-phenoxy-hex-1-ene, either by liver microsomal systems in the presence of NADPH and O2 or C6H5IO, or by iron-porphyrin- C6H5IO model systems. These aldehydes do not derive from rearrangement of the corresponding epoxides suggesting that they are formed by an hydrogen migration within an interdiate formed by reaction of the olefin with the active oxygen-iron complex. Heme model studies show that the competition between the three possible routes of oxidation of these olefins is greatly dependent upon the environment of the iron.

TETRAPYRROLIC GLYCOSYLATED MACROCYCLES FOR AN APPLICATION IN PDT

The synthesis and characterization of amphiphilic glycoconjugated porphyrins, benzochlorin, and azaporphyrins were reported. Among these molecules, several were found to be efficient photosensitizers in an in vitro assay using the human tumoral cell line HT29. Moreover, glycosylated benzochlorin and azaporphyrins, whose absorption bands in the red region of the visible spectrum are substantially increased as compared to porphyrins, display a good photocytotoxicity on tumor cells after irradiation with wavelength above 590 nm.

Definitive evidence for a proximal effect of pyridine in the NaOCl/Mn(porphyrin)x / pyridine catalytic oxygenation system

Abstract Using pyridine-attached manganese porphyrins, it has been possible to obtain definitive evidence that pyridine behaves as a proximal ligand in the NaOCl/Mn(porphyrin)X catalytic oxygenation system.

Synthesis, characterization and photocytotoxicity of a glycoconjugated meso-monoarylbenzochlorin

Abstract Amphiphilic glycoconjugated benzochlorin was prepared efficiently from meso monoaryl porphyrin and 3-(dimethylamino)acrolein by regiospecific Vilsmeiers reaction followed by cyclisation under acidic conditions and glycosylation. This compound displays a good in vitro photocytotoxicity on tumor cell lines after irradiation with light > 590 nm.

Synthesis of interlocked basket handle porphyrins

Abstract The synthesis and the characterization by UV-visible and 1 H NMR spectroscopic analyses of interlocked basket handle porphyrins in which the two subunits are assembled by the Cu(I) complex of phenanthroline residues inserted into superstructures are reported.

Glycosylated Porphyrins: Characterization of Association in Aqueous Solutions by Absorption and Fluorescence Spectroscopies and Determination of Singlet Oxygen Yield in Organic Media

The behavior of a series of porphyrins substituted at meso positions by para‐phenyl‐β‐d‐glucose groups is examined in aqueous solutions by absorbance and fluorescence spectroscopies. This series includes tetra‐, tri‐ and diglycosylated compounds, the last being substituted at adjacent or opposite meso positions. The other subsituents are alkyl chains and, in one case, a fluorophenyl group. Although all these compounds dimerize in aqueous solutions, the dimerization constants span over four orders of magnitiude (Kd= 1.3 × 105–1.9 × 109 M−1). The dimer stability is strongly dependent on the nature and the arrangement of the substituents. The diglycosylated derivative substituted at adjacent meso positions yields the most stable dimer that is likely to present an offset stacked geometry. The dimer structures expected from the symmetry of the various compounds correlated well with the optical spectra that display exciton splitting in the Soret band. The fluorescence of the dimers is quenched in all derivatives with the noticeable exception of the adjacent diglycosylated derivative. All the compounds studied photosensitize the formation of singlet oxygen with yields ranging between 0.54 and 0.81. A fairly linear correlation between the yield and the number of aryl groups at meso positions is observed.

Enantioselective epoxidation of olefins by single-oxygen atom donors catalyzed by managanese-glycoconjugated porphyrins

New chiral porphyrins bearing glycosyl substituents (glucose, maltose or lactose) at ortho or meta positions of the meso-phenyl groups have been synthesized. Their manganese complexes, associated with hydrogen monopersulfate, lithium hypochlorite, hydrogen peroxide, or iodosylbenzene, have been used as enantioselective catalysts for the epoxidation of 4-chlorostyrene and 1,2-dihydronaphthalene.