Identification et synthèse de nouveaux depsides isolés de la mousse de chêne (Evernia Prunastri (L.) ACH.). 4e Communication

Identification and synthesis of new depsides isolated from oakmoss (Evernia Prunastri (L .) ACH .) Lecanoric acid 5 and 4 new depsides have been isolated from oakmoss (Evernia Prunastri (L .) ACH .) extracts by means of silicagel column chromatography. Various spectral methods including ¹³C-NMR. were used in determining the structure of 4,2″-O-methylgyrophoric acid ( 1 ), lecanoric acid ( 5 ), 2′-O-methylevernic acid ( 2 ), 3′-methylevernic acid ( 3 ) and methyl 3′-methyllecanorate ( 4 ).     

Composants volatils de la «mousse de chêne» (Evernia Prunastri (L.) ACH.) 3e communication

Volatiles constituents of “Oakmoss”(Evernia Prunastri (L .) ACH .) The chemical consititution of different fractions of two oakmoss oleoresines were investigated by GC./MS. using SCOT. and capillary columns. Besides many known compounds, over 52 (sesquiterpenes, aliphatic and aromatic hydrocarbons) have not yet been reported as constituents of oakmoss.     

Triterpènes de la «mousse de chêne» (Evernia Prunastri (L.) ACH.). 5e Communication

Triterpenoids from ‘Oakmoss’ (Evernia Prunastri (L .) ACH .) Seven triterpenoids have been isolated from ‘oakmoss’ (Evernia Prunastri (L .) ACH .) extracts by column chromatography and identified as friedelin ( 1 ), taraxerol ( 2 ), 29-nor-21 α-hopan-3,22-dione ( 3 ), moretenone ( 4 ), ursolic acid ( 5 ), lupeol ( 6 ) and lanosterol ( 7 ).     

Synthèse et réactivité de dihydrotriazines et de dihydrotriazolotriazines

Generally, 4,5-dihydro-3triazinones have been prepared by a basic hydrolysis of 3-methylmercapto-4,5-dihydrotriazines. Of the serveral methylation methods, namely, diazomethane, methyliodide, dimethyl sulfate all in the presence of sodium methylate or silver carbonate, only methyl bromide in the presence of phase transfer catalyst was sucessful in producing all of the N-2 and/or N-4 methylate compounds. Two unequivocal syntheses of dihydrotriazolo[4,3-b]triazine are reported.     

Etude des composés flavoniques et xanthoniques dans les feuilles de Gentiana ciliataL

Study of the flavonic and xanthonic compounds in the leaves of Gentiana ciliata L . Fifteen 1,3,7,8-oxygenated xanthones ( 1 – 15 ) were isolated from the leaves of Gentiana ciliata L. (genus Gentianopsis). Among these were six new glycosides: glucosyl-1-decussatin 6 , glucosyl-1-gentiacaulein ( 8 ), primeverosyl-8-isogentiacaulein ( 9 ), glucosyl-3-isogentiacaulein ( 10 ), glucosyl-1-swertianin ( 12 ) and primeverosyl-7-swertianin ( 13 ). Three known flavone C-glucosides were also found ( 16 – 18 ).     

Oscillations chimiques lors de l'oxydation de dicétones par le bromate en présence d'un catalyseur (Réaction du type Belousov-Zhabotinsky)

New ketonic compounds have been found to generate temporal chemical oscillations in Belousov-Zhabotinsky – type reactions: fluorinated acetylacetone, acetonylacetone (2,5 hexanedione) and, acetone itself.     

Caractérisation de nouveaux dérivés et analogues de la nétropsine et identification de leurs intermédiaires de synthèse par spectrométrie de masse FAB

The fast-atom bombardment (FAB) mass spectra of a series of netropsin derivatives and analogues were examined in positive-ion and when necessary negative-ion modes. Behaviour of these derivatives was related to that of oligopeptides. Some compounds protected by t-butoxycarbonyl groups were also investigated using this technique and showed characteristic fragmentations.     

Isomérisation de 2,3‐époxypinanes fonctionnels en présence d'acides de Lewis

Isomerization of Functionalized 2,3‐Epoxypinanes in the Presence of Lewis Acids The functionalized 2,3‐epoxypinanes 1b – i were submitted to isomerization in the presence of ZnBr₂ at 110° (Table 1) or of BF₃⋅Et₂O at different temperatures (Table 2), and their behavior was compared with that of the non‐functionalized parent 1a and with similar known transpositions. The produced campholenals 2 , pinocamphones 3 , and in some cases, fencholenals 4 were isolated and characterized. A mechanism involving a concerted oxirane ring opening is proposed (Scheme 4).     

Stabilité dans le méthanol et propriétés thermodynamiques de transfert des cryptates de certains cations de transition et de métaux lourds

Stability in Methanol and Thermodynamic Transfer Properties of the Cryptates of some Transition Cations and Heavy Metals The nature and stability of the macrocyclic and macrobicyclic complexes of Ag⁺, Cd²⁺, and Pb²⁺ (Mⁿ⁺) with 21, 22, 211, 221 and 222 in anhydrous methanol 0.05M in Et₄N⁺ClO^?₄, at 25° (see Scheme) have been determined by potentiometry and spectrophotometry. Binuclear complexes M₂L²ⁿ⁺ have been observed in all cases, besides the mononuclear MLⁿ⁺ complexes. The macrobicyclic 1:1 complexes MLⁿ⁺ exhibit an important ‘cryptate effect’ with Mⁿ⁺=Ag⁺, Pb²⁺ and Cd²⁺, but not with Cu²⁺ and Zn²⁺; their stability is in all cases maximum with 221. The applicability to our results of the recent extrathermodynamic hypothesis involving MLⁿ⁺ cryptates is examined.     

Ionisation Chimique de Composés Aromatiques Nitrés

The collision induced dissociations of [MH – 30]⁺ ions observed in the chemical ionization (methane) mass spectra of some nitro aromatic compounds show that these ions are formed by reduction in the ion source with subsequent protonation and not by the previously reported losses of NO^· from the protonated molecular ions.     

Régiospécificité et stéréosélectivité de la cycloaddition de l'oxyde de benzonitrile sur les pyrazolines-3

Pursuing our study on the cycloaddition of benzonitrile oxide with Δ₃-pyrazolines (1,2), we can now affirm that this reaction is regiospecific and stereoselective. The behaviour in acidic medium was studied. We have then discussed the process of epimerization and degradation observed according to the C₄ substituent of the bicyclic molecule and the solvent used.     

Oxydations et halogénations régiosélectives et réactions carbéniques de dérivés de sucres portant un groupement thioéther

Regioselective Oxidations, Regioselective Halogenations and Carbene Reactions of Sugar Derivatives Bearing a Thioether Group Regioselective stoechiometrically controlled procedures are described for the oxidation of thiosugars either at the sulfur atom (to sulfoxides or sulfones) or at a hydroxymethylene group (to ketosugars). Ruthenium tetraoxide reacted at both sites. Chloration (SO₂Cl₂) of β-ketothioether sugar derivative 3 took place exclusively at C(6). Evidence is given that a chlorosulfonium intermediate C was formed when the dichloroketothiosugar derivative 6 was treated with SO₂Cl₂. The carbene generated from the tosylhydrazone 16 rearranged to the enoses 17–20 , the migrating group coming in equal proportions from C(4) and C(6). Some stereochemical aspects of these reactions are discussed.     

Etudes configurationnelles et conformationnelles de quelques chlorures de désoxy-6 β-L-héxopyrannosyle chlorosulfonyles et de leurs glycosides de méthyle

A total analysis of the NMR spectra of 6-deoxy-L -hexopyranoses in the α-configuration and of the corresponding β-anomers was carried out. The parameters obtained are characteristic of a 1C (L ) chair conformation, having the anomeric substituent in an axial orientation for the methyl α-fuco-, α-rhamno- and α-chinovopyranosides and for the α-fuco- and α-rhamnopyranosyl chlorides. The structure is also of a 1C (L ) chair type for the methyl β-fuco- and β-chinovopyranosides; the geometry is the same for the β-fuco- and β-rhamnopyranosyl chlorides despite the anomeric effect of a chlorine atom. However, the NMR parameters of the β-chinovopyranosyl chloride are not explicable on the basis of a chair conformation with an equatorial chlorine or a boat structure.     

Synthese d'lsosélénazoles et de benzisosélénazoles-1,2

A general preparation of the isoselenazole ring by addition of bromine followed by ammonia on cis-β–methylseleno-2-propenal is described. This reaction was successfully applied to 1,2-benz-isoselenazole, a new heterocyclic system.     

Addition du chlorure de nitrosyle et de l'oxyde d'azote(III) sur l'allyltriméthylsilane et sur l'allylbenzyldiméthylsilane

Additions of Nitrosyl chloride and Dinitrogen trioxide to Allyltrimethylsilane and Allylbenzyldlmethylsilane. The reaction of nitrosyle chloride and dinitrogen trioxide with allyltrimethylsilane and allylbenzyldimethylsilane leads to nitrosochlorides and to pseudonitrosites. The structures of these compounds are proved by reduction to amines.