Analyse Conformationnelle de Pseudoprotoberbérines Naturelles. II. Etude Structurale par RMN de 13C des Tétrahydropseudoprotoberbérines provenant de I'Isopyrum thalictroïdes

The four pseudoprotoberberins extracted from Isopyrum thalictroides L. were reduced with sodium borohydride to the corresponding tetrahydropseudoprotoberberins. Comparison between the ¹³C NMR spectra of these and of synthetic protoberberins allowed us to assign a trans-1 configuration to the four reduced alkaloids and also to provide for this particular configuration an unequivocal criterion for the differentiation (based on the chemical shift of C-8) between tetrahydroprotoberberins (9, 10 substituted) and tetrahydropseudoprotoberberins (10, 11 substituted).     

De la chimie des ptérines. 15e communication. Hydroxylation non-enzymatique de la phénylalanine en tyrosine à l'aide de ptérines tétrahydrogénées

The non-enzymatic hydroxylation of phenylalanine to tyrosine has been effected by atmospheric oxygen in aqueous solution in the presence of 5,6,7,8-tetrahydropterines, Fe^II or Fe^III, and EDTA, in a phosphate buffer at pH 6,9. A possible reaction mechanism is discussed.     

De la chimie des ptérines. 19e communication [1]. Essai d'interprétation des propriétés chimiques des ptérines au moyen de calcul d'orbitales moléculaires

HMO and semi-empirical SCF calculations on pterine systems of biochemical interest have been performed. The most basic center of each molecule has been determined by correlating the perturbation effect on the transition energy and the spectroscopic data. Additional calculations attempt to show why the redox-system which interfers in hydroxylation reactions consists of 5,6,7,8-tetrahydropterine and a quinoidic form. Finally the formation of radicals in the oxidation step of hydrogenated pterines is discussed.     

De la chimie des ptérines. 78e Communication.. Synthèse de l'ester tripolyphosphorique de la tétrahydro-5, 6, 7, 8-D-néoptérine. Essai d'interprétation de la biosynthèse de la L-sépiaptérine

Synthesis of 5, 6, 7, 8-Tetrahydro-D -neopterine tripolyphosphate. Attempt to Interpret the Biosynthesis of L -Sepiapterine The synthesis was achieved by phosphorylation of tetrahydro-5, 6, 7, 8-D -neopterine with polyphosphoric acid. The product is sensitive to light, moisture and oxidation like the other tetrahydropetrines. After oxidation in aqueous solution, D , L -sepiapterine was isolated in 5% yield. The oxidation of non-phosphorylated tetrahydro-5, 6, 7, 8-D -neopterine under the same conditions led to D -sepiapterine without inversion of the configuration. These findings were used to give a tentative explanation for the biosynthesis of natural L -sepiapterine from the D -neopterine.     

Réarrangements 1,3 en série hétérocyclicque. II. Synthese d'alcoxy-5 et aryloxy-5 phényl-2 oxadiazoles-1,3,4

The 5-Chloro-2-Phenyl-1,3,4-oxadiazole has been prepared in fair yield. This product is a convenient starting material for the synthesis of O-alkylated or O-arylated derivatives of the 5-hydroxy-2-phenyl-1,3,4-oxadiazole.     

Analyse isotopique de mélanges d'éthanols deutériés C2H5-nDnOH

The qualitative and quantitative isotopic analysis of mixtures of nuclear isomers of ethanol C₂H_5–nD_nOH is described. The samples are obtained by reduction reactions and in each of them an isomer is markedly predominant. After a mass spectrometric determination of the amount of isotopic species with the same overall deuteration, these species are identified by proton and deuteron NMR, by combining the spectral schemes of all the isomers which can be assumed until agreement is reached with experimental spectra; isotope effect on δ is taken into account. The importance of the isotopic varieties are then determined by integrating some characteristic lines, with variable accuacy. For each sample, the total intensities of methyl and methylene signals are also compared in proton and deuteron resonance. By elevating the temperature of the sample, one can see the fine structure of a methylene signal broadened by the deuteron quadrupole relaxation.     

Structure du méthyl-3 phénylamino-4 phényl-5 triazole-1,2,4

The crystal structure or 3-methyl-4-phenylamino-5-phenyl-1,2,4-triazole has been determined by X-ray diffraction. It allows one to choose between the two reaction mechanisms which can be taken into account for the reaction of hydrazine upon N-acylated hydrezonates.     

Synthèses stéréospécifiques et étude organoleptique comparée de onze triméthyl-2,2,3-exo-norbornyl-5-exo-cyclohexanols racémiques

The stereospecific syntheses of the eleven racemic 2,2, exo-3-trimethyl-exo-5-norbornyl-cyclohexanols related to the formula VI have been achieved. Moreover, the fragrant properties of these isomeric and stereomeric cyclohexanols have been carefully estimated by a team of four well-experienced perfumers. In good agreement with our earlier observations [1 ab], it was concluded that the axial 3-(2,2, exo-3-trimethyl-exo-5-norbornyl)-cyclohexanols, threo (XXIV) and erythro (XXIX), are the only isomers which display a very powerful and genuine sandalwood odour. The other cyclohexanols were found to be about 20–100 times less fragrant (4 compounds), or practically odourless (5 compounds).     

Dérivés de l'hydroxyméthyl-5 furfural. I. Synthése de dérivés du di- et terfuranne

Addition of α, β-unsaturated sulfones or ketones to 5-hydroxmethyl-furaldehyde or related furanaldehydes in the presence of a thiazolium salt gives di or tetraketonic furan compounds. Dehydrative cyclizationled to di- and terfuryl derivatives.     

Spectrométrie de Masse D'Hétérocycles Azotés. VI—Tautomérie en Phase Gazeuse d'Isoxazolones-5

A comparison of the fragmentation under electron impact of isoxazol-5-ones with those of their methylated derivatives (5-methoxy isoxazoles, 2-methyl isoxazol-5 ones and 4-4-dimethyl isoxazol-5 ones) shows that in the vapor phase and prior to the fragmentation, the isoxazol-5 ones exist in the CH tautomeric form. Furthermore, in the case of the 5-methoxy isoxazoles, it has been established that the rearrangement isoxazole→azirine→oxazole which occurs thermally, leads to a variation in the intensities of some ions depending on the experimental conditions.     

Synthèse d'acides acyl-3 ylidéne-5 tétroniques

A general synthetic route to new 3-acyl-5-ylidenetetronic acids by rearrangement in the presence of bases of 4-carbethoxy-2-ylidene[2H]-3-furanones is described.     

Synthèse d'hydroxyspirocétals insaturés et hétérocyclisation en méthyl-5 trioxa-2,6,11 tricyclo[5.3.1.01.5]undécane

The photochemical irradiation of unsaturated ketoacetals 4 gives unsaturated hydroxyspirocetals 6 . The mixture of these stereoisomers yields by thermal or ionic treatment a trioxatri-cyclo compound 7 .