Résonance magnétique nucléaire du noyau 14N par Transformée de Fourier

¹⁴N-NMR. measurements using the Fourier Transform technique are presented and compared to C. W. experiments. The F. T. technique is especially advantageous for relaxation time measurements. However, since ¹⁴N-nuclei may have widely different relaxation times, it is often not possible to have optimal gain in sensitivity (as compared to C. W. measurements) in a single F. T. experiment for different ¹⁴N-nuclei contained in the same sample. Different experiments have to be performed, optimizing the spectrometer parameters for each ¹⁴N-resonance of appreciably different linewidth. The technique is applied to three different problems. ¹⁴N-relaxation in symmetrical ammonium salts is shown to arise from reorientation of the water dipoles. The use of a double spin-probe, ¹³C-¹⁴N, allows the determination of the electric field gradients in cyclic ammonium salts. The electronic distribution is especially distorted from tetrahedral symmetry in the highly strained N, N-dimethyl-aziridinium cation. Finally, electric and dynamic effects in ion pairing may be studied as shown on the case of tetrabutylammonium iodide in water and in benzene.     

Thiosucres. III. Réactions du substituant (benzylthio)-acétyle. Communication préliminarie

Thiosugars. III. Some reactions of the (benzylthio)-acetyl substituent Preliminary Communication The (benzylthio)-acetyl substituent as found in 6-benzylthio-6-deoxy-1, 2-O-isopropylidene-3-O-methyl-α-D-xylo-hexofuranos-5-ulose ( 1 ) constitutes and useful synthon which can be transformed into ‘second generation’ synthons as, for example, the sulfylidene 10 or the chlorinated derivative 14 . S-Debenzylating C-acylation of 10 leading to 11 is described as well as the ring-forming condensation of 10 with the sulfene 12 . Depending on the nature of the nucleophile reacted with 14 , one can obtain the product of the substitution of the chlorine atom or of the chlorine atom and the benzylthio group or reactions taking place at both the carbonyl group and the terminal carbon atom, among them binucleophilic cyclizations. Some reactions of the conjugate base of 14 are also described.     

Biosynthèse de la farnésylacétone-(E,E) par les glandes androgènes du crabe carcinus maenas

Biosynthesis of E, E-farnesylacetone by the andogenic glands of the crab Carcinus maenas Using sodium acetate-1,2-[¹⁴C] or mevalonic acid-2-[¹⁴C], the biosynthesis of (E,E)-farnesylacetone 1 by the androgenic glands of the crab Carcinus maenas, kept as organ subculture is demonstrated. Ozonolysis of the NaBH₄ reduction product 3 leads to three fragments the radioactivity of which has been measured after isolation by GC. It is thus established that the biosynthesis of 1 proceeds through geranylgeraniol. The hexahydroderivative 2 is not labelled in the two experiments.     

Synthése totale d'α-disaccharidyles de tridésoxy-2,5,6-streptamine apparentés aux aminosides à partir du maltose et du lactose

Total synthesis of α-disaccharidyl-2,5,6-trideoxy-streptamines related to aminoglycoside antibiotics derived from maltose and lactose The synthesis of the hitherto unknown 4-O-substituted α-linked pseudo-tri-saccharides 1,2 and 3 is described. The key intermediates required in the reaction sequence are the glycals 12, 13 and 14 , prepared from maltose, lactose and the chiral ditosyloxy-cyclohexanol 15 , readily accessible from quinic acid. The pivotal step in the reaction's scheme - a stereospecific α-glycosylution procedure -, is an acid-catalyzed addition of the alcohol 15 to the glycals 12, 13 and 14 leading to the corresponding 2,3-unsaturated trisaccharides. The latter compounds were transformed to the target α-glycosides of 2,5,6-trideoxystreptamine 1, 2 and 3 which were devoid of significant antibacterial activity. These results indicate that the presence of an ether linkage at the position 4′ is probably critical for antibacterial activity.     

Copolymeres du chlorure de vinyle et de l'acrylate de glycidyle

A study of the radical copolymerization of vinyl chloride (C) and glycidyl acrylate (A) at 60° in dichloroethane solution leads to the following reactivity ratios r_c = 0·14 ± 0·02 and r_A = 7·4 ± 0·3According to the nature of the solvent, the reaction of protonic acids may cause either cationic polymerization of epoxy groups or addition of HCl or water onto the same groups. The HCl addition is observed during the thermal degradation of the copolymers so that HCl evolution is greatly delayed.     

Détermination du Site de Protonation de l'Azido-2 thiazole et du Thiazolo[2,3-e]tétrazole à Partir de la Largeur des Raies des Signaux Protoniques

The signals of protons bonded to carbon atoms in α position to the pyridinic nitrogen atom in thiazole and in γ position in thiazolo[2,3-e]tetrazole are broadened. This broadening disappears on irradiation at the ¹⁴N resonance frequency, on cooling, and in an acidic medium (in which the protonation sites in both molecules can be determined).     

Synthèse du méthanesulfonate de (pyrimidyl-2)-1-(méthylène)-(dioxy-3, 4-benzyl)-4-pipérazinium (Piribedil) marqué au 14C

The synthesis of crystalline 1-(2-pyrimidyl)-4-(3, 4-methylenedioxybenzyl)-piperazin methanesulfonate (ET 495) labelled with ¹⁴C fixed on the piperazine nitrogen N(4) has been realized in five steps from barium carbonate ¹⁴C; Specific activity of the final product: 32,8 mCi/mmol (110 m?Ci/mg); radiochemical purity: around 99%. The mass spectrum of the labelled compound is in agreement with the chemical structure and the labelling position expected.     

Synthese de diterpenes tetracycliques du type hibane

Hibaone has been synthesized from manool through a photochemical cycloaddition of Δ⁸⁽¹⁴⁾ podocarpene-13-one to ethylene or 1,2 dichloroethylene.     

Préparation du cyclohexadiène-1,4 à partir du benzène par voie organosilicique

3,6-Bis(trimethylsilyl)-1,4-cyclohexadiene, obtained from direct disilylation of benzene in an inert atmosphere, is hydrolysed at 0–5° in a strongly basic medium to 1,4-cyclohexadiene.     

Synthese d'antibiotiques triterpeniques a partir d'acides biliaires-II : Introduction du methyle 14α associe á Δ-8,9

The synthesis of methyl 14α-methyl-15-oxo-5β-chol-8-en-24-oate derivatives from cholic acid is described, as are the spectroscopic data of the various intermediates. A route to tetracyclic triterpene acids related to polyporenic acid is thus opened.     

Etude du comportement électrochimique du manganèse dans le tampon borate

The anodic behavior of the manganese electrode in borate buffer solutions have been studied by potentiostatic and galvanostatic electrochemical techniques. Three distinct steps determined on the charging curves are attributed to the formation of Mn (OH)₂, MnOOH and MnO₂. The manganese dioxide formed anodically in pH 11 borate solution may be reduced cathodically with high faradaic efficiency.     

Sur la présence d'un ester du décadiénol-2(E), 4(Z) et de diterpènes dans l'huile essentielle de cyprès (Cupressus sempervirens L.)

Decadien-2(E), 4(Z)-yl isovalerate, sandaracopimara-8(14), 15-diene, dehydroabietane and manoyl oxide have been isolated from the cypress essential oil. The determination of the structure and the spectral parameters of this compounds is described.     

Purete radionucleidique du solute injectable d'eau tritiee

Conclusion Nous avons mis au point une méthode simple permettent de détecter les impuretés β^-, à l'aide d'un compteur à scintillation liquide. La courbe établie en mesurant la variation du taux de comptage en fonction du seuil de discriminateur pour la préparation à l'essai, doit être parallèle à celle obtenue, dans les mêmes conditions, avec une solution étalon d'eau tritiée. Le mélange scintillant dioxane-naphtalène, 2,5-diphényloxazole (PPO), 1,4-bis-2-(4-méthyl-5-phényloxazolyl)-benzène (diméthyl POPOP) [1 litre/100 g/7 g/0,3 g] permet de détecter la présence d'au moins 0,005% de³⁵S, 0,004% de¹⁴C et 0,04% de⁴⁵Ca.

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The radionuclidic purity of tritiated water is checked by an easy and rapid method using a liquid scintillation counter. The liquid scintillator: dioxane (1 liter)/naphtalene (100 g)/(PPO (7 g)/dimethyl POPOP (0.3 g) allows the detection of, at least, 0.005% of sulfur—³⁵S, 0.004% of carbon—¹⁴C and 0.004% of⁴⁵Ca.

     

Utilisation d'ylides du phosphore en chimie des sucres. XII Dérivés du D-arabino-hexène-1-tétrol-3,4,5,6

The preparation of several kinds of derivatives of 1-substituted D -arabinc-hex-1-ene-3,4,5,6-tetrols is described. Some of these compounds, having a ‘pseudo-formyl’ group (? CH?CHCN, ? CH?CHSO₂CH₃) are ‘pseudo-aldehydo-sugars’. Their ability to react as aldehydo-sugars was examined in light of their ¹³C-NMR. spectra which provide information on their electron density at C(1) and C(2).     

Hexacoordination du phosphore par complexation intramoleculaire

An equilibrium occurs between penta- and hexacoordinated phosphorus when a basic function is located at the end of a branched ligand on pentacoordinate phosphorus. Generally the hexacoordinated form are thermodynamic stable species in solution at room temperature. Eight hexacoordinated compounds (9–11, 13, 14, 18–20, Tables 2 and 3) have been isolated. In few cases, in solution, the pentacoordinated form (15–17, 24) can be observed. The parameters from these equilibria are discussed.     

Sulfoquinovosyldiacylglycerins from <Emphasis Type="Italic">Scaphechinus mirabilis</Emphasis>

A sulfolipid, the structure of which was established by NMR spectroscopy, electrospray-ionization mass spectrometry (ESI-MS), and GC–MS, was isolated for the first time from the sea urchin Scaphechinus mirabilis. The sulfolipid was identified as a sulfoquinovosyldiacylglycerin (SQDG) and was the sum of related compounds. The fatty acids (FAs) of the SQDGs included saturated 14:0–24:0 FAs (95.8% of total FAs) and mono-unsaturated 20:1-24:1 FAs (4.2%). The principal FAs were saturated 14:0 (33.1%) and 16:0 (54.2%). ESI-MS/MS detected 15 molecular species of SQDGs, among which the contents of 14:0/14:0 and 16:0/16:0 were relatively high although 16:0/14:0 dominated.     

μ-Oxalato Complexes du Molybdène(V) et (VI) et du Niobium(V)

Molybdenum(V) and (VI) and Niobium (V) μ-Oxalato Complexes The complexation of the « oxalato » ligand as bis-(bidentate) bridge in the solid compounds {(C₂H₅)₄N}₂ {M₂^VO₂X₆(C₂O₄)} or {(C₂H₅)₄N}₂ {M^VIO₄X₄(C₂O₄)} (with M^V = Mo or Nb; M^VI = Mo and X = F, Cl, Br) is characterized on the basis of their infrared spectra and analytical data. The behaviour, of the Mo^V dimer compounds in near corresponding mononuclear species at room temperature, because of the low interaction between metallic ions.     

Determination continue du carbone-14 et du soufre-35 en milieu aqueux par un dispositif a scintillation: Application aux effluents chromatographiques

A recording apparatus is described for determining soft radiations (¹⁴C,³⁵S) in aqueous medium, especially adapted for continuous analysis of Chromatographie effluents It is based upon the spreading of the liquid in a thin layer in contact with a plastic scintillator coupled to a coincidence circuit The efficiency is comparable to that of a thin end-window GM counter in the absence of auto-absorption.     

Nouveaux modeles polysilicies a partir d'indoles,du benzothiophene et du benzofuranne

Direct polysilylation of bicyclic heterosubstrates was performed without (in the case of indole or its N-methyl or N-trimethylsilyl derivatives) or with (benzothiophene, benzofuranne) ring-opening. Hexasilylation from benzothiophene occurred with desulfurization.     

Reactivite des carbanions benzyliques : VIII. Etude de la structure d'alkyl-9 lithio-10 dihydro-9,10 anthracenes par rmn du proton et spectrometrie d'absorption electronique; influence du substituant,du solvant et de la temperature

The structure of the 9,10-dihydroanthracenyl anion and of a series of 9-alkyl-10-lithio-9-10-dihydroanthracenes (9-R-10-LiDHA, I–V where R = H, Me, Et, i-Pr, t-Bu) was studied in solution by electronic absortion spectrometry and proton magnetic resonance. Our electronic absorption results, in addition to those of other authors, show that the contact ion pairs (c.i.p.) have an absorption at λ_max}- 400 nm (I–III) and 415 nm (V) whereas the loose ion pairs (l.i.p.) absorb at λmax}- 450 nm (I–V). In the NMR the chemical shift of the proton para with respect to the carbanionic center was examined as a function of solvent (THF, THF/HMPA, and in some cases ether or pure HMPA) and temperature (+20 to ?40°C). The para proton is shielded significantly with regard to the aromatic protons of the hydrocarbon (Δδ(H_para) ca. 1–1.7 ppm). The weakest shielding was observed in ether, in agreement with the existence of c.i.p. The largest shielding (THF/HMPA or pure HMPA) is in connection with the presence of l.i.p. where the negative charge is less localised at position 10. Moreover, in the same solvent, and at the same temperature, Δδ(H_para) was observed to increase with the substituent bulk, up to the point that there are only l.i.p. present. As found previously (namely for the fluorenyl anion) the l.i.p./c.i.p. ratio increases when temperature decreases. The results of this structural study allow to rationalize the protonation stereochemistry of 9-alkyl-10-lithio-9,10-dihydroanthracenes in the above-mentioned solvents.