Acide glyoxylique Symétrie de la molécule libre, spectres de vibration et attribution

The infrared and Raman spectra of glyoxylic acid in the gas phase, in solution and in the solid state have been obtained in the region from 4000 to 300 cm⁻¹. p]Band structure analysis in the gaseous state shows that the configuration of formyl-carbonic acid is trans and planar. It was established that in solution some bands belong to dioxyacetic acid. p]A vibrational assignment is proposed based on a priori calculation of the spectra, using a Urey-Bradley force field intermediate between those of glyoxal and oxalic acid.     

Calcul de l'Énergie de Corrélation pour l'État Fondamental de la Molécule d'Acétylène

Correlation effects in the acetylene molecule are studied by a method using the technique of Feynman-like diagrams. The introduction of the reduced atomic electronic integrals decreases considerably the value of correlation energy.     

Sur la Stoechiométrie de la Variété Allotropique γ de Bi2O3

On the Stoichiometry of the Allotropic Variation γ-Bi₂O₃ The study of the solid solutions Bi₁₂[BBi□_1/5]O₂₀ (B^+V = As, V) with 0 ? x ? 0,80 leads for x = 0,77 to a phase whose cubic centered symmetry and parameter (10.255 Å) correspond to those previously announced for γ-Bi₂O₃. The présence of impurities seems required to obtain such a phase whose theoretical stoichiometry should be Bi₁₂[Bi□_1/5]O₂₀ i. e. Bi₂O_3,125.     

Un nouvel exemple de nucléoside à sucre ramifié insaturé: la désoxy-3′-méthylidène-3′-adénosine

A Novel Example of Unsaturated Branched-chain Sugar Nucleoside: 3′-Deoxy-3′-methylidene-adenosine Starting from 5-O-benzoyl-3-C-methylidene-3-deoxy-1,2-O-isopropylidene-α-D -erythro-pentofuranose ( 11 ) the title compound 8 has been prepared. Its α-anomer ( 9 ) and the acyclic sugar nucleoside 10 have been obtained as by-products. Adenosine deaminase slowly deaminated 8, 9 being not affected. Compound 8 exhibited no antiviral activity, whereas one of its saturated analogues ( 13 ) inhibited the multiplication of the herpes-1 (HF) virus.     

Une Nouvelle Classe de Polymeres d′α-Olefines ayant une Régularité de Structure Exceptionnelle

The exceptional properties of a new class of linear polymeric hydrocarbons, obtained by the polymerization of α-olefins, are described. The high melting points, the high degree of crystallinity, the low solubility, and the special mechanical properties of these polymers are attributed to a particular regularity of structure, due to the existence, in each macromolecule, of a long sequence of asymetric carbon atoms, all having the same steric configuration. It is suggested that this special type of order of asymetric carbon atoms in linear macromolecules be called “isotactical.”     

Réactions induites par les halogénures de pyridinium. XXIV. Sur la synthése de dibenzofurannes à partir de diméthoxy-2,2′ biphényles

Dibenzofurans were obtained by the cyelization of 2,2′-dihydroxybiaryls using pyridinium bromide. The 2,2′-dihydroxy-biaryls were obtained by demethylation via pyridinium chloride from 2,2′-dimethoxybiaryls. The dealkylation which is followed by cyelization into the dibenzofurans with pyridinium bromide is complicated by indirect transmethylation. Acyl derivatives of 2,2′-dimethoxybiaryles lose their acyl group when dealkylated by pyridinium halides, whether or not cyelization follows this process.     

Etude des Dérivés de la Vitamine B6. Conformation des Complexes de Lanthanides avec le Pyridoxal-5′-phosphate et la Pyridoxamine-5′-phosphate en Phase Aqueuse à pD = 1,3

A suitable procedure is described for establishing the conformational analysis of flexible molecules coordinated to lanthanide cations from ¹H and ¹³C NMR paramagnetic shift data. The examples of pyridoxal 5′-phosphate (PLP) and pyridoxamine 5′-phosphate (PMP) in aqueous solution at pD = 1.3 values are discussed. In the two cases, a hindered rotation around P? O-5′, with Gaussian distribution is proposed. The values of angles and distances between rare earth cations and ligand nuclei are determined.     

Etude de la réactivité de la fonction carbonyle avec le cétène en présence d'un alcoxyde de titane. 1ère communication. Nouvelle méthode de synthèse de β-hydroxyesters

A new synthesis of β-hydroxyesters involving a reaction between a carbonyl compound, ketene and an alkyl-orthotitanate is described. The following carbonyl compounds have been studied: aldehydes, ketones, α-diketones, α- or γ-ketoesters. A reaction mechanism is proposed.     

Les β-cétonitriles groupes protecteurs de la fonction amine. Préparation d'amino-alcools

β-Ketonitrile-Derived Protecting Groups of the Amino Function. Synthesis of Amino Alcohols The amino group of natural L -amino acid esters is protected by condensation with 2-oxocyclopentanenitrile ( 1 ) or 2-formyl-2-phenylacetonitrile ( 10 ). Only the ester group of the formed cyanoenamino esters 2 and 11 reacts with nucleophilic reagents such as organometallics (RMgX, RLi), borohydrides, or metal amides, whereas the cyanoenamino group is unchanged (Schemes 1 and 2). Cyanoenamino alcohols obtained by reduction of cyanoenamino esters 2 are hydrolyzed under acidic conditions to amino alcohols with retention of the configuration of the starting amino acid. This sequence of reactions allows to prepare derivatives of L -tyrosinol from (?)-L -tyrosine (see, e.g., Scheme 4). Cyanoenamino esters 11 are readily methylated at the N-atom to give N-methylated cyanoenamino esters (Scheme 3). This property is exploited on the way of a multistep procedure to obtain N-methylated amino alcohols homologous to natural (?)-(1R,2S)-ephedrine.     

Systemes aromatiques à 10 électrons π dérivés de l'aza-1-pentalène. I. Recherches dans la série du pyrazolo[3,4-d]-v-triazole

After the structure of the N-methyl derivatives has been established in an univocal manner, the reactivity of a pyrazolo-[3,4-d]-v-triazole derivative toward various methylation agents has been investigated. A structure is suggested for the N? NO and N? COR derivatives.     

Etude par spectrométrie de masse d'une série d'alcanediphtalimides-α,ω

Mass spectrometric study of a series of alkane-α,ω-diphthalimides Alkane-α,ω-diphthalimides with three to seven aliphatic C-atoms were synthesized and their mass spectral behaviour investigated in detail with the aid of the deuteriated derivatives of hexane-1,6-diphthalimide. Besides the expected hydrogen rearrangements, an interesting skeletal rearrangement has been observed.     

Etude par spectrométrie de masse de la fragmentation du désoxy-3-di-O-isopropylidène-1,2: 5,6-méthylidène-3-α-D-hexofurannose et de quelques analogues substitués en C(3′)

Electron Impact Mass Spectrometry of the 3-Desoxy-1,2: 5,6-di-O-isopropylidene-3-methylidene-δ-D -hexofuranose and Some C(3′)-Substituted Analogues The mass spectra of the 3-desoxy-1,2:5, 6-di-O-isopropylidene-3-methylidene- α-D -ribo-hexofuranose and of some C(3′)-mono- and -disubstituted derivatives have been investigated. Deuterium labelled molecules allow fragmentation modes to be proposed.     

Aziridines N-Non substituées. Détermination des Paramètres Thermodynamiques ΔG°, ΔH°, ΔS° Liés à l'Equilibre Conformationnel à partir de Mesures RMN 1H à Haut Champ

Although nitrogen inversion in unsubstituted aziridines has been shown by ¹H NMR, it was only possible to study quantitatively the distribution of both invertomers and determine the thermodynamic parameters by a systematic high field NMR study (CAMECA 250 MHz). Thermodynamic parameters have been determined for 32 compounds. In C-aryl aziridines, the steric hindrance of the aromatic group and its variation with other aziridine ring substituents can be studied. These observations are in agreement with a conjugation phenomenon between the aromatic system and the aziridine ring.