Catherine Fontaine

Insertions photochimique et spontanée d'oxygène dans les liaisons cobaltcarbone des alcoylcobaloximes

Abstract Some alkyl(pyridinato)cobaloximes irradiated with visible light insert molecular oxygen into the cobaltcarbon bond to give stable peroxidic compounds; the alkyldioxycobaloximes. This insertion reaction also occurs without light with alkylcobaloximes having a cobaltcarbon bond in a benzylic position.

Etude de quelques facteurs influencant l'insertion photoinduite d'oxygene dans la liaison cobalt—carbone des alcoylcobaloximes

Abstract The photo-induced insertion of oxygen into the cobalt—carbon bond of alcoylcobaloximes occurs by the way of a pentacoordinated complex obtained by photolytic cleavage of the cobalt—base bond. This bond is reformed immediately after the insertion of oxygen to give the alkylperoxycobaloxime.

Photochemical substitution reactions of some alkylcobaloximes by hydroperoxides and the crystal structure of cumyl peroxide (pyridine) cobaloxime

Abstract Alkyl(pyridine) cobaloximes irradiated with visible light in the presence of tert-butyl or cumyl hydroperoxide give rise to tert-butyl or cumyl peroxide(pyridine)cobaloxime by photochemical substitution reaction. We report the structure of the cumyl peroxide(pyridine)cobaloxime determined by X-ray diffraction

Pyrazole alkaloids from Newbouldia laevis

Abstract Phytochemical analysis of the root bark of Newbouldia laevis revealed the presence of four pyrazole alkaloids. These were characterized using various spectroscopic data as withasomnine, and the novel 4′-hydroxy-withasomnine, newbouldine and 4′-hydroxynewbouldine.

Enantioselective synthesis of (2S,3S)- and (2R,3R)-pyrrolidine-2,3-dicarboxylic acids : conformationally constrained (S)- and (R)-aspartic acid analogues

Abstract The title compounds were prepared from the key intermediate 2 and its enantiomer at C2, derived from chiral synthons 1 - ( R ) and 1 - ( S ), respectively, by ethoxycarbonylation, desulfonylation and conversion to carboxylic acid.

A new method for the synthesis of branched ribonucleotides

Abstract A new route, using phosphotriester intermediates, for the synthesis of branched ribonucleotides is described.

Electron spin resonance study of free radical intermediates in the photolysis of some alkylcobaloximes and peroxycobaloximes using the technique of spin trapping

The anaerobic photolysis of methyl- and benzyl-pyridinecobaloximes and some analogous compounds proceeds via an electron transfer reaction to form a CO11 species containing the original axial ligands. Using the technique of spin trapping with 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) we have recorded an ESR spectrum which corresponds to the hydrogen atom adduct of DMPO. By use of selective deuteration and preparation of a BF2 derivative we have shown that the ejected hydrogen atoms originate from the equatorial ligands of the complexes. The anaerobic photolysis of isopropylpyridinecobaloximes and analogous complexes also yields hydrogen atoms, but the products of photolysis arise from a CoC bond cleavage. Anaerobic photolysis of alkylperoxycobaloximes in the presence of DMPO reveals the formation of both hydrogen atoms and RO• radicals.

Stylotelline, a new sesquiterpene isocyanide from the spongeStylotella sp. application of 2D-NMR in structure determination

Abstract The sesquiterpene isocyanide stylotelline isolated from the marinesponge Stylotella sp. was assigned the structure 1a (absolute stereochemistry) on the basis of spectral - essentially 2D-NMR - and chemical data.

Monomargine, a nitrogenous cytotoxic pigment from Monocarpia marginalis

Abstract Monomargine 1 , a new nitrogenous pigment, was isolated from the bark of Monocarpia marginalis and its structure elucidated by 2D NMR analysis. 1 exibited cytotoxic activity in vitro against the growth of KB and P388 cells (IC 50 0.7 μ/ml).

Synthèse du système cyclique de l'aza-triquinane linéaire par trois cyclisations radicalaires en cascade

Abstract Treatment of the acyclic allyl-octa-4,7-dienyl N-chloroamine 5 by titanium trichloride induces a chain process including three consecutive regio- and stereo-selective homolytic cyclisations. As a result of these selectivities, the main product of the reaction is an original linear cis-syn-cis aza-triquinane, the structure of which was assigned by high field (400 MHz) Nuclear Magnetic Resonance study.