Matériaux réactifs à base de collagène

Studies on the functionalisation of collagen by the introduction of polymerisable unsaturated groups, by analogy with the transformation of -OH or -NH₂ groups in proteins using acryloyl chloride as reagent, are presented. These unsaturated groups participate in copolymerisation reactions with vinyl monomers to produce interpenetrating networks. The influence of the parameters temperature, amount of acryloyl chloride and pH on the degree of transformation of the conjunctive protein (evaluated by IR spectroscopy and by dosage of free amine functions) is presented. It was established that pH has a significant influence on the nature of formed bonds (amine or ester type) and on the degree of transformation. Electron microscopy to analyse the products of copolymerisation between functionalised collagen and water-soluble monomers (acrylamide) was used. Interpenetrating networks with complex morphology were observed.     

Synthèse en une étape de N-méthoxyindolinones, de N-méthoxymaléimides et d’anhydrides maléiques à partir d’acides hydroxamiques α-halogénés

α-Halo hydroxamic acids were used in the synthesis of N-methoxyindolinones, symmetric and dissymmetric N-methoxymaleimides in good yields. The hydrolysis of N-methoxymaleimides constitues a new and good route to maleic anhydrides.     

Synthèse de nouveaux dérivés tétrahydroquinoléines et quinoléines via la réaction d'aza-Diels-Alder suivie d'aromatisation

The Aza-Diels-Alder reaction of aldimines with isoeugenol is described. New 1,2,3,4-tetrahydroquinoline and quinoline structures are reported. The stereo- and regioselectivities of the [4+2] cycloaddition are discussed.     

Cycloadditions [3+2] et [4+2] de l'α-nitrosostyrène sur le 2-hydroxyméthylène indanone et ses dérivés

The preferred [3+2] cycloaddition before hetero-Diels-Alder reaction of 2-hydroxymethylene indanones derivatives with α-nitrosostyrene is described. New fused spiro-pyrroles-1′-oxide and spiro-1′,2′-oxazines structures are reported. The stereospecificity and regiospecificity of the cycloadditions are discussed.     

Synthèse et propriétés photochimiques de modèles imides et amides contenant des structures norbornadiènes pentaméthylés

Four pentamethylated norbardiene (NBD) models containing imide, bis-imide and diamides were synthesized in the first step of this work with a good yield and characterized by IR, ¹HNMR and ¹³CNMR spectroscopies. These models were used for study, by UV-Visible spectrophotometry, of the photochemical isomerisation under solar radiations of NBD residues, which they contain to quadricyclane (QC). Acquired results show, for all these models, that more than 70 % of NBD are transformed into QC after only 30 minutes of solar radiations and following a first order rate.     

Alcoylation par l'iodure de butyle,de l'enolate de tetrabutylammonium de l'acetylacetone; nature de l'entite reagissante

The alkylation of tetrabutylammonium acetylacetonate with butyl iodide was studied in order to specify the nature of the reactive anionic species during the nucleophilic reaction of an ambident anion, under similar conditions to those of phase transfer catalysis. The C/O alkylation ratio changes with neither the solvents nor the enolate concentration; however k_obs, varies with the solvent but does not depend on the énolate concentration. The results and spectrophotometric UV data show that only one reactive species, the ion-pair, is involved.     

Obtention de phosphore élémentaire et de phosphures de nickel par électrolyse de solutions de pentoxyde de phosphore dans des bains à base de cryolithe

By electrolysis of cryolitic solutions of P₂O₅, elementary pure phosphorus is obtained on carbon cathode and Ni phosphides on Ni cathode. The most probable mechanism of phosphorus formation in these conditions seems to be the final dissociation of P₂O₅ in P⁵⁺ and O^2? and the primary electrodic discharge of these ions.     

Stéréochimie des réactions de réactifs de grignard au niveau de l'atome de silicium d'un cyclosilane asymétrique

The stereochemistry of coupling reactions of Grignard reagents and symetrical organomagnesium compounds with the silicon atom of 1,2,3,4-tetrahydro-2-(1-naphthyl)-2-silanaphthalene is studied. The results show that the electrophilic at the leaving group, by the metal atom is not a main factor for the retention of the configuration. It is possible to give a first explanaion of the stereochemical pathway of these reactions by considerig the “hard and soft” character of the attacking organometallic as well as polarisability of the leaving group.     

Cycloaddition d'azides aux sels de nitrilium; obtention de sels de tetrazolium et de tetrazolines

The reaction of nitrilium salts with azides allows the synthesis with good yields of 1,4,5-alkyl or -aryl-substituted tetrazolium salts. The mechanism of this reaction is discussed. Reduction or alkylation of these tetrazolium salts leads to the corresponding tri- or tetra-substituted tetrazolines.     

Etude par spectrométrie de masse de l'ionisation de benzonitriles,de phénylacétonitriles et de N,N-diméthylanilines substitués

Molecular ionization potentials for series of compounds of the type X? C₆H₄? CN, X? C₆H₄CH₂? CN and X? C₆H₄? N(CH₃)₂ have been measured using the retarding potential difference technique (RPD. technique). The effect of the various substituents X is better correlated through the electrophilic Brown σ_p⁺ constants than through Hammett's σ_p values. No meta-para orientation effect is observed. For all the disubstituted phenyl compounds studied, the effect of the second substituent is affected by the electron-releasing power of the original substituent. Ionization potentials calculated by using the semi-empirical method of equivalent orbitals are in good agreement with the experimental values.     

Sinthese de copolymeres sequences de l'acetate de vinyle et de l'acrylate d'ethyle par telomerisation

A new two-step procedure for the synthesis of ethyl acrylate - vinyl acetate block copolymers is described : the first stage is the telomerisation of ethyl acrylate with carbon tetrachloride by redox catalysis, the second being another telomerisation of vinyl acetate, using the trichloromethyl end group of the first block as the telogen agent, with peroxydic initiation.     

Isolement de nouveaux complexes de zinc de dipyrrométhènes formés au cours de la synthèse de la méso-tétramésitylporphyrine par la réaction de Rothemund

Three new zinc bis(dipyrromethene) complexes have been isolated in the preparation of meso-tetramesitylporphyrin by the Rothemund zinc template based condensation process.     

Constantes de couplage de vinylallènes

In order to define the influence of an allenic type conjugation, the NMR spectra of vinylallene and of some of its methyl derivatives are analysed The signs of the coupling constants are also determined. These compounds are characterised by a planar s-trans structure of the two noncumulated double bonds. A discussion of the parameters, and especially of the methyl replacement effects, evidences the importance of the π type contributions. The theoretical calculations of the coupling constants by the methods of finite perturbation CNDO and INDO corroborate this interpretation.     

Application de la réaction de Wittig à la synthèse de dérivés de bromoénosuloses et d'esters bromoénuroniques. Note de laboratoire

Use of the Wittig reaction for the synthesis of derivatives of bromoenosuloses and bromoenuronic esters Treatment of 3-O-benzyl (or 3-O-methyl)-1, 2-O-isopropylidene-α-D -xylo-pentodialdo-1, 4-furanoses ( 2 or 1 ) with acetylbromomethylidenetriphenylphosphorane ( 3 ), benzoylbromomethylidenetriphenylphosphorane ( 4 ) or bromoethoxycarbonylmethylidenetriphenylphosphorane ( 5 ) gave in good to excellent yields the expected enose ( 6--11 ). In all cases but one ( 8 where some 10% of the E-isomer was formed) the reaction led to the exclusive formation of the Z-isomer whose configuration was established by NMR.     

Effet de longueur d'onde et controle par la geometrie de l'etat fondamental de la photoisomerisation de derives de l'hexatriene-1,3,5

Irradiations at different wavelengths (313, 254, 229 and 214 nm) of the 4 geometric isomers of 5-phenyl-1,3,5-heptatriene show that the photochemical behaviour of these trienes is mainly controlled by their ground state equilibrium.