Préparation de phosphonates de sucres ramifiés par addition nucléophile conjuguée. Communication préliminaire

Preparation of unsaturated sugars phosphonates using nucleophilic conjugate addition Different types of phosphorus nucleophiles underwent conjugate addition reaction with one of the branched-chain sugars 4, 5 or 11 the addition taking place either on the endo or the exo face of the furanose ring (or on both faces in the case of 11 ). The configuration at C(3) of these new phosphorus-bearing types of sugars as well as the configuration at the phosphorus atom of the cyclic phosphinates 9 and 10 was established by NMR. (³J_P,H–C(2), ³J_P,C(1)). Small amounts (7%) of the spiro enol phosphonate 16 were formed when 11 reacted with trimethyl phosphite.     

Conformation et Spectrometrie de RMN. III. Spectres 13C de Diméthylamino Cyclanols et Dérivés

The ¹³C NMR spectra of 2-dimethylaminocyclohexanols and the four trans-3-dimethylamino-2-decahydronaphtols are described. The gauche interactions allow precise estimation of chemical shifts for each carbon atom; thus, band attribution can be resolved without mistake. In the case of the cis and the trans diequatorial compounds, the conformational perturbations which we have suggested before are verified by our present measurements on the substituted carbon atoms. We also show effects on adjacent atoms, which were unobservable with the usual IR and ¹H NMR techniques.     

Alcoylation d'acridanone-9. Premiers exemples de O-alcoylation dans cette série de composés

The results of nucleophilic substitution of the 2-methoxy-9-acridone are discussed in terms of competition between both ionic sites N^? and O^?, of the molecule. They are the first examples of O-alkylation of substituted 9-acridone.     

Facteurs stériques influençant la transposition de Wagner-Meerwein des carbocations de type pinanyle

Steric factors influencing Wagner-Meerwein rearrangement of pinanyl carboniumions. The course of the Wagner-Meerwein rearrangement of ions obtained by protonation of substituted α- or β-pinenes is strongly dependent on the configuration of the substituents. The situation is complicated by the possibility of double bond isomerisation (α-→β-pinenes) before rearrangement. Simple rules for predicting the products are given.     

Etudes stéréochimiques XIV. Adduits de Diels-Alder en série résiniques; action des peracides et ouvertures acido-catalysées d'époxydes

Studies in Stereochemistry XIV. Diels-Alder adducts in the resin series; action of peracids and acid-catalysed ring opening of epoxides The synthesis of Diels-Alder compounds of type 2 with a 17-nor-13(14)-atisène skeleton is described (cf. Schemes 1–3). Depending on the nature and configuration of substituents R¹ and R² on the carbon atoms 15 and 16, an epoxide ( 24–33 ) or a ketone ( 35–38 ) or a mixture of epoxide, ketone and lactone is obtained by the action of p-nitroperbenzoic acid on the double bond of these adducts (cf. Scheme 4). A simplified reaction scheme is suggested to explain the formation of the various products. In an acid-catalysed reaction, the epoxides isomerize mainly into ketones. Nevertherless, in some cases, dienes (e.g. 52 ) or hydroxy-γ-lactones of (13R*, 14S*)-configuration (e.g. 50 ) resulting from the opening of the epoxide ring with retention of configuration were obtained.     

Dérivés Alléniques de l'Étain,du Plomb et du Mercure. Signes Relatifs des Constantes de Couplage Métal-Proton á Travers Deux et Quatre Liaisons

Satellites corresponding to metal-proton coupling constants through two and four bonds are observed in PMR spectra of Pb, Sn and Hg allenic derivatives. The relative signs of these coupling constants are deduced from analysis of the satellite spectra: ²J(X? H) and ⁴J(X? H) are of opposite signs for X = ²⁰⁷Pb, ¹¹⁹Sn, ¹¹⁷Sn and of same sign for X = ¹⁹⁹Hg. Probable absolute signs of reduced coupling constants are discussed in relation to published data: ²K(X? C? H) is probably positive for X = ²⁰⁷Pb, ¹¹⁹Sn, ¹¹⁷Sn and ¹⁹⁹Hg. ⁴K(X? C?C?C? H) is probably negative for X = ²⁰⁷Pb, ¹¹⁹Sn, ¹¹⁷Sn and positive for X = ¹⁹⁹Hg.     

Utlisation d'ylides du phosphore en chimie des sucres. XIII. Synthèse de dérivés des hydroxyméthyl-3-D-glucose et-D-galactose et de composés voisins

The treatment of the 1, 2:5, 6-di-O-isopropylidene-α-D -ribo- and xylo-hexofuranos-3-uloses with cyanomethylenetriphenylphosphorane led in each case, and in almost quantitative yields, to a pair of geometrical isomers of C-cyanomethylenic sugars having respectively the ribo and the xylo configurations. Permanganate oxidation of these branched-chain unsaturated sugars afforded the corresponding gem-hydroxyformyl compounds bearing the formyl group on the more hindered face of the molecule. The formyl group of these sugars is easily derivatized to an oximino or reduced to a hydroxymethyl. The configuration at the new asymmetric carbon has been established by comparison with known compounds or by synthesis of a C(3) epimer by the classical route involving a Grignard reagent.     

Etude des formes fermées et ouvertes de spiropyrannes benzothiazoliniques en RMN 13C et 1H par transformée de Fourier

Benzothiazolinic spiropyrans, merocyanines and photomerocyanines, thermally stabilised to a high degree, have been studied by means of Fourier transform ¹H and ¹³C NMR. The results show the polarity of open forms such as merocyanines and photomerocyanines, their trans configuration, the alternation of the electronic density on the dimethine bridge between the ‘benzothiazolinic’ and ‘phenolate’ part of these molecules, and also a favoured configuration when photomerocyanines have an alkoxy or aryloxy group on the 3 position.     

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.     

Influence de la substitution sur la structure de la benzophenone. X.—Etude conformationnelle de benzaldehydes,acetophénones et benzophénones substitués par complexation avec les lanthanides

Low temperature ¹H NMR was unsuccessful in conformational analysis of substituted benzophenones. However, induced lanthanide chemical shifts study permitted us to check satisfactorily the results obtained by Rayleigh depolarised light scattering and dipole moment studies on meta and ortho substituted benzophenones. The existence in solution, of a conformational equilibrium in these cases is confirmed.     

Structure des Complexes de Meisenheimer Complexes de Courte Duree de Vie et Complexes Stables Formes par Action des Ions Méthoxydes sur les Dinitro-4,6 Anisoles X-2 Substitues

The NMR study of the reaction of methoxide ions on several substituted 2-X-4,6-dinitroanisoles (X = F, Cl, CF₃, CN) permitted the identification of various Meisenheimer complexes formed by the attack of CH₃O^? ions on the non-substituted 5- and 3-carbons. The shortlived 1,5- and 1,3-complexes undergo a fast conversion to the stable 1,1-complexes. The chemical shifts of anisoles and complexes are dependent on electronic and steric effects of the X-substituent. The influence of the negative charge held by the ring and the geometrical changes of the skeleton are shown by a comparison between the NMR parameters of anisoles and the corresponding complexes. When X = F, a study of the relative signs of the coupling constants shows that ³J(F? H) and ⁵J(F? H) are of opposite signs for the anisole and the 1,1-complex.     

Etude en RMN du 13C de Mérocyanines Benzimidazoliniques

A series of α-oxobenzimidazolinic merocyanines differently substituted on the ‘phenolate’ part and bearing a paraffinic chain on one heterocyclic nitrogen, has been studied by ¹³C NMR. Electron donating substituents bring about an increase of the electronic density on the 3 methine carbon and an increase of the alternation of electron density on the 3,4-dimethine bridge. A bathochromic shift of the lower energy electronic transition is also observed. Furthermore, the low field resonance of the 3 methine proton is probably due to a specific interaction between this proton and the ‘phenolate’ oxygen atom. This implies the existence of a favoured trans configuration for merocyanine dyes.     

Interactions Intramolécularies—XVII Calcul des constantes de couplage en RMN du cyclohexane et de cyclohexanes substitués. Comparaison des méthodes de Pople et Santry et des perturbations finies

Proton–proton ³J, ⁴J and ⁵J NMR coupling constants have been calculated for cyclohexane and monosubstituted cyclohexane conformers (substitiuents: Li, CH₃, OH, F) by the two methods mentioned. Comparing the two methods on the basis of group theory, we show the necessity to use the second. The results from this method are compared with those of the literature.     

Polymérisation radicalaire du pentadiène-1,3. II. Microstructure des résidus pentadiéniques dans les homo- et copolymères des cis et trans pentadiènes-1,3 avec l'acrylonitrile

The microstructure of diene units was investigated in radical homopolymers of the cis and trans isomers of 1,3-pentadiene and copolymers with acrylonitrile, synthetized in bulk and emulsion. Experiments were carried out by infrared spectroscopy, 100 MHz ¹H-NMR, and 25 MHz ¹³C-NMR studies. No difference between the bulk and emulsion samples was noted. The microstructure of poly(1,3-pentadiene) is practically independent of the cis or trans configuration of the diene monomer and is as follows: 56–59% trans-1,4, 15–17% cis-1,4, 16–20% trans-1,2 7–10% cis-1,2 and 0% 3,4. On the other hand, up to about 30% of incorporated acrylonitrile (10% in the feed), the microstructure of the pentadiene fraction in the copolymers is not affected. This finding suggests that the penultimate unit has very little influence on the polymerization process involving the terminal pentadienly unit. Beyond 10% of acrylonitrile in the feed, the proportions of the structural units were linearly dependent upon the acrylonitrile content: trans-1,4 content increased whereas the amounts of cis-1,4 trans-1,2 and cis-1,2 decreased (except the cis-1,2 fraction, constant in the copolymers from the cis-diene). These results are discussed on the assumption that the microstructure of pentadiene residues is strongly associated with the acrylonitrile comonomer in the feed.     

Étude des spectres infrarouges de divers dialcoyl-diméthoxy-stannanes

The infrared absorption spectra of some dialkyldimethoxystannanes have been investigated in the 400–1500 cm^?1 region. The bands associated with v_s(SnC₂) and v_s(SnO₂) vibrations have been found at 510–521 cm^?1 and 466–475 cm^?1. The group of bands between 560 and 620 cm^?1 is assigned jointly to v_a(SnC₂) and v_a(SnO₂) vibrations. v(C? O) of the methoxy groups linked to tin appears at 1064–1068 cm^?1.     

Polymérisation anionique des diènes. V. Configurations des oligopolyisoprènyl–lithium en milieu benzènique et en présence de dioxanne. Étude par résonance magnétique protonique: Haute résolution (RMP-HR)

By PMR, three dioxane–Li⁺ complexes have been detected for the oligopolyisoprenyl–lithium–dioxane mixtures in benzene solution. The (4-1) living end isomerizes into the cis configuration when the sample temperature or the dioxane concentration is increased, but the isomerization phenomenon is reversible only if dioxane/Li⁺ ratios are smaller than unity. The specificity of the vinyl addition (86%), mainly (4-3) (70%), due to the stronger negative charge at the C_γ carbon atom is effective only at low temperature (+15°C). At higher temperature, because of the steric hindrance of the methyl group, this stereospecificity decreases.     

Action de nucléophiles sur des sucres ramifiés cyanovinylidéniques: Addition conjuguée,stéréomutation,migration de doubles liaisons. Communication préliminaire

When treated with a series of nucleophiles cis-3-cyanomethylene-3-deocy-1,2:5,6-di-O-isopropylidene-α-D-ribo-hexofurannose ( 1 ) may yield its trans isomer, a product of allylic isomerization or a product of conjugate addition, depending on the nature of the nucleophile. The configuration of the starting material is also important as shown by the differences in reactivity between 1 and its trans-xylo isomer 8 .     

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.     

Synthèse de composés cyclopentaniques chiraux,di, tri et tétrasubstitués. Application à la synthèse de dérivés Oxa-13-prostanoïques

The cyclopentenecarbaldehyde 1a , acetals 2a , 2b and the cyclopentenone 2c have been transformed through regio and stereocontrolled reactions into a variety of enantiomerically pure substituted cyclopentanes. Using appropriately selected Wittig reagents, aldehyde 1a furnished the condensation products 3 , 4 , 5 . Michael addition of diethyl malonate on the α,β-unsaturated aldehyde 1a under phasetransfer conditions led efficiently to 7 . Reduction of the cyclopentenone 2c gave 21 in high yield. The cyclopentenes 2a , 2b and 23 , submitted to hydroboration-oxidation furnished the cyclopentanols 10 , 13 and 24 , respectively, in 30, 70 and 50% yields, reflecting the substitution pattern of the starting alkenes. The salient feature of these reactions is the stereospecificity due to the chiral centre of the molecules 1a , 2a , 2b and 2c , leading to compounds with two, three and four asymmetric centres. The straightforward synthesis of 11α-hydroxy-13-oxaprostanoic acid 20 is described and an approach towards the preparation of 9α, 11α-dihydroxy-13-oxaprostanoic acid 34 is also presented. The structure of these products has been determined by ¹H- and ¹³C-NMR spectroscopy.     

Détermination par Résonance Magnétique Nucléaire de la Configuration d'alcools Bicycliques [4.2.0] et Tricycliques [6.4.0.02,7] ou [5.4.0.02,6]

The configuration of various bicyclo[4.2.0]octanols has been established by ¹H NMR spectroscopy, with Eu(dpm)₃ as shift reagent. The intrinsic parameters Δ and K have been obtained and used as structural probes. Moreover, detailed data analysis showed that, contrary to the generally accepted concept, the vicinal coupling constant between trans cyclobutanic protons can be larger than that between cis protons. The chemical shifts obtained by ¹³C NMR spectroscopy are consistent with the proposed structures. The results have been extensively used to determine unambiguously the configuration of tricyclo[6.4.0.0^2,7]dodecanols and tricyclo[5.4.0.0^2,6]undecanol.