Systèmes aromatiques à 10 électrons π derivés de l'aza-3a pentalène. XVII. Tautomérie azido/tétrazole dans la série du pyrazole

The IR and NMR study of twelve 3- (or 5-) azidopyrazoles shows that the azide is the only tautomer present under neutral conditions. The most stable isomer (tautomer) is 3-azido in N-acetyl and N-H derivatives. 3-Azidopyrazoles are the only polyazoles in which coupling with the N-H in NMR (solvent: DMSO) is observed. In a basic medium, the corresponding anions of the 3-azidopyrazoles N-H are formed: these anions slowly evolve, following first-order kinetics, to the bicyclic anions of pyrazolo-[1,5-d] tetrazoles, derived from 3a-azapentalene. This evolution has been checked by means of IR and NMR spectroscopy.     

Oligomérisation anionique de l'ethylène. III. Application à la synthèse d'alcools à longue chaine

Living oligomers of ethylene obtained by n-BuLi complexed with TMEDA have been deactivated by ethylene oxide. The nuclear magnetic resonance study of the product obtained allowed us to follow the influence of TMEDA toward the functionalization. Three products have been characterized: By increasing the ratio [TMEDA]/[n-BuLi] one obtains a decrease of the functionalization reaction.     

Systèmes aromatiques à 10 électrons π dérivés de l'aza-3a penlalène. VIII. Recherches dans la série du pyrazolo[3,2-c]-s-triazole

It has been shown that the reaction of β-ketoesters with 1,2-diamino-1,3,4-triazoles affords pyrazolo[3,2-c]-s-triazoles. These results induces us to propose a 7,8-dihydro-9H-s-triazolo[4,3–6]-[1,2,4] triazepin-8-one structure for the intermediate in this synthesis.     

L'isomérie géométrique d'amidines mono-substituées de l'acide benzothiazole-carboxylique-2. Isomères anti à carboxyle normal,isoméres syn à carboxyle énolisé

The condensation of methyl benzothiazole-2-iminicarboxylate with α-amino-acetic esters gives rise to amidines possessing only one (I) of the two possible tautomeric structures. Both syn and anti isomers have been characterized of the single tautomer. This is the first demonstration of geometrical isomerism around the imine group in amidines. The carboxylic esters and the free acids of the syn fro exist exclusively as the enol, whereas the anti derivatives prefer the carboxyl structure. The existence of these isomers has been confirmed by their IR., UV., and NMR. spectra as well as by the inversion of their configuration and the formation of cyclic derivatives.     

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.     

Synthèse de systèmes comportant deux cycles thiophéniques orthocondensés à un hétérocycle à sept chainons

The reduction of the carbonyl group of bithienyls carrying on each thiophene ring a formyl group bonded to the carbon atom next to the intercyclic bond leads to the expected primary di-alcohols. These dialcohols can give the corresponding bis-halogeno-methylated bithienyls. The dehydration of the alcohols and the action of sodium sulfide or amines upon the obtained halides leads respectively to the dihydrodithieno[c,e] oxepines, thiepines and azepines. The tetramethyl derivatives of the previous oxepines have been obtained from diacetylbithienyls.     

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.     

Identification de stérols à chaîne latérale oxygénée dans une éponge de l'espèce Hyrtios

Thirty-two sterols are identified in the sponge Hyrtios sp. In addition to fourteen monohydroxylated compounds, the sterol fraction contains eight functionalized sidechain sterols, three of them new: 3 β-hydroxy-24-norchol-5-en-23-al (19) , (22-trans)-3 β-hydroxycholest-5, 22-dien-24-one (20) and (22R, 23R, 24S) or (22S, 23S, 24S)- 22,23-epoxy-24-methylchoest-5-en-3 β-ol (24). The probable biological origin, rather than artifact production, of these undescribed components is discussed.     

Contribution à la connaissance des o-menthols et des o-menthones (carquéjanols et carquéjanones) - 1ère communication

The mixture of carquejanols obtained from carquejol of carqueja oil has been converted in ketones. The alkohols obtained respectively by hydrogenation on Pt(O₂), by lithium-aluminiumhydride reduction and by Meerwein-Ponndorf-Verley reaction have been separated by vapour phase chromatography. The ketones obtained from the Beckmann oxidation of the alkohols has been identified as carquejanone and isocarquejanone by application of the Auwers-Skita rule.     

Analogues de la showdomycine à activité antitumorale

Antitumor showdomycin analogues A series of 3-glycosylidenesuccinimides ( 3 ) and 3-glycosylidene-1-phenyl-succinimides ( 5 ) have been prepared in good yields using a Wittig reaction. In each case, the preponderant, or even the exclusive, isomer formed was E. As expected from orbital considerations, the contribution to the conformational equilibrium of the rotamer whose H? C (γ) and H? C(δ) bonds were antiparallel was low. One of these succinimide derivatives 3a showed interesting anticancer activity, similar to that of the sugar enone C. These compounds probably act as somewhat selective alkylating agents.     

Résonance Magnétique Nucléaire en phase nématique. Exploration de la barrière d'empêchement à la libre rotation de la monofluoroacétone

The NMR spectra of monochloro-, monobromo- and monofluoroacetone (CH₃? CO? CH₂X with X = Cl, Br, F) oriented in a nematic phase have been measured and the direct dipolar coupling constants determined. The barrier to internal rotation for the CH₂F group has been studied for fluorine compound using various hypotheses. The best agreement with IR data has been obtained using the potential equation V(θ) = Σ_n V_n × (1 – cos nθ)/2 and a Boltzmann distribution of the CH₂F group (V₁ = 250 ± 50 cal.mol^?1, V₂ = 1650 ± 100 cal.mol^?1, V₃ = ?1000 ± 100 cal.mol^?1).     

Voies d'accès à un analogue pyrannique de la puromycine

In a continuation of our studies with methyl 3-amino-3,4-dideoxypetopyranosides, two pyranic analogues of puromycin 3A and 3b have been synthesized by two routes starting from methyl 2,3-anhydro-4-deoxy-or D, L -erythro-pentopyranosides. In the first one, both amino group and erythro stereochemistry have been introduced before the introduction of the purine moiety; in the second one the introduction of the erythro stereochemistry and of the 3-butrigeb atom has, more advantageously, been performed in the same step using an intermediate (22) with a suitable conformation. The two diastereoisomerws 3A and 3B have been separated and, after assignment of absolute configuration and the heterocyclic studies, will permit and evaluation of the role plays played by the heterocyclic oxygen atom by comparison with previous studies on cyclohexyl puromycin analogues (Vince et al.).     

Constitution moléculaire d' α,ω-difluoro-μ-oxo-poly(méthylphosphanoxy diméthylsilanes): Mise en evidence d'une forte tendance à l'alternance régulière des centres siliciés et phosphorés à l'equilibre

The purpose of this study was to gain a closer knowledge of the molecular constitution of the linear fluorine-terminated oxygen-bridged methylphosphanoxy/dimethylsilane polymers, for example, to find evidence for preferential sorting (or, on the contrary, for random scattering) of the substituents and building units. The title polymers were prepared by reaction of MeP(O)F₂ with cyclic dimethylsiloxanes (Me₂SiO)_n (n = 3 or 4). An equilibrium is reached in the redistribution of fluorine vs. bridging oxygen atoms among the phosphorus and silicon-based centers, and among the resulting building units, after about 2 months at 120°C. The excellent resolution of the ¹H-NMR spectra (Fig. 2), even at 60 MHz, allowed identification of seventeen different fragments (Table II). Nineteen equilibrated samples of varied overall compositions (R = F/(Si + P); R′ = P/(Si + P)) have been analyzed (Table IV), and their molecular constitution is described by a set of four basic constants. The fundamental features which govern the structure of these polymers are as follows. (a) The regular (Si-O-P) alternation of the two different centers, which is thermodynamically favored, as shown by the linkage constant K₀ = [Si-O-Si][P-O-P]/[Si-O-P]² ? 10⁴, which describes the sorting of the silicon and phosphorus atoms on the bridging oxygens, and which deviates by four orders of magnitude from its random value of 0.25. (b) A somewhat surprising lack of preferential distribution of fluorine and oxygen between the two centers (K_I = [MeP(O)F₂][Me₂SiO_1/2]₂/[Me₂SiF₂]-[MeP(O)(O_1/2)₂]) differs little from (a), which contrasts with the preferential affinity of fluorine for silicon and oxygen for phosphorus (K_I ? 10⁷) that was found when F atoms and OCH₃ groups were exchanged between the same centers. (c) The sorting of the fluorine atoms and oxygen bridges on each center, to give neso molecules and the terminal and medium building units, resulting in a slight preference for the formation of the terminal units, as expressed by      

Agglomération contrôlée de latex par formation de complexes tensioactifs anioniques : copolymères à blocs à base de poly(oxyde d’éthylène)

For polystyrene–poly(ethylene oxide) (PS–PEO) diblock copolymers, as micellar dispersions in aqueous medium, the formation of complexes with anionic surfactants, such as sodium dodecylsulfate (SDS) could be confirmed. The number of SDS molecules fixed per EO unit is close to the values reported for the SDS–PEO homopolymer interaction. Advantage of this type of complexation was taken to develop a controlled agglomeration process for SDS stabilized PS and PVC latexes by using as agglomerants ‘hairy’ latexes of PS and PVC that have been synthesized in the presence of PS–PEO block copolymers and that carry therefore a fringe of PEO sequences on their surface. The complexation of SDS by these surface-anchored PEO chains leads to the destabilization of the anionic latex, which has a tendency to precipitate onto the surface of the agglomerant latex. The average particle size and the size distribution of the agglomerated particles were studied as a function of the weight and number ratio of the two types of latexes involved in the agglomeration process, as well as in function of the surface coverage by SDS and PEO respectively. By adjusting these parameters, it was possible to obtain, with an efficiency of almost 100%, latex agglomerates with a monomodal distribution in the size range of 1 to 40 μm. An agglomeration mechanism could be outlined taking into account the complexation capacity and the specific surface of the agglomerating ‘hairy’ latex. To cite this article: P. Peter et al., C. R. Chimie 6 (2003).     

Hétérocycles à fonction quinone. 7. Benzo[f]quinazolinediones-7,10 à action antitumorale potentielle

Few benzo[f]quinazoline-7,10-diones 4a-c are prepared by oxidation, with potassium nitrosodisulfonate, of the corresponding benzo[f]quinazolinamines, made by reduction of the nitro analogues which were obtained from 8-methoxybenzo[f]quinazolin-1(2H)-one. The compound 4a shows an interesting cytotoxicity.     

Synthèse électrochimique du cycle époxydique. Communication préliminaire

The polarographic behaviour of ditosyloxy alkanes TsO(CH₂)_nOTs in aprotic medium suggests that intramolecular cyclisation takes place after reductive cleavage of a single SO₂? O bond at the dropping electrode. This hypothesis was verified by controlled potential electrolysis of the lower homologues at a mercury cathode. High yields of epoxy compounds are obtained by this method.     

Equation de Karplus appliquée à des systèmes sp2–sp3

A method of best fitting for the calculation of vicinal coupling constants is presented for sp²-sp³ systems. Results for 68 vicinal coupling constants from 32 different products are presented. We obtain the best Karplus-type equation to date with a dispersion factor of 31,01%.     

Isomérisations en chimie des sucres. II Fermetures de cycles par attaque nucléophile intramoléculaire sur des carbones sp2 à caractère électrophile: Furannoses hybridés sp2 en C3

When heated with one equivalent of H₂O, the 1,2: 5,6-di-O-isopropylidene-α-D-ribo- and -xylo-hexofuranos-3-uloses loose one molecule of acetone and yield the 3, 6-anhydro-1, 2-O-isopropylidene-α-D-ribo- and -xylo-hexofuranos-3-ulose ketohydrols. The carbonyl group of the starting material seems to provide some kind of intramolecular electrophilic assistance to the hydrolysis of the 5, 6-O-isopropylidene group. When the oxygen of the carbonyl group is replaced by cyanomethylene, an analogous cyclisation takes place under base catalysis, provided that C6 bears a free hydroxyl group.     

Synthèse d'azido dithiényl-1,2 éthènes et éthanes

Two convenient preparations of azido-1,2-dithienylethenes are described. The synthesis of azido-1,2-dithienylethanes proceeds via metalation (n-Buli) and subsequent treatment by tosylazide of bromo-1,2-dithienyl-ethanes. The structures of the obtained derivatives were established on the basis of ¹H nmr, ir, and mass spectral data.     

Synthèse de nouveaux types de dérivés C-glycosyliques à partir de sucres acétyléniques ou de leurs équivalents synthétiques partiels

Synthesis of Novel Types of C-Glycosyl-derivatives from Acetylenic Sugars or Partial Synthetic Equivalents thereof The concept of synthetic equivalent is not unequivocal and, for example, α-fluoroenamines may behave in some cases as synthetic equivalents of ynamines and, in other situations, quite differently. Some uses of these α-fluoroenamines, ‘partial synthetic equivalents’ of ynamines, for the synthesis of C-glycosyl derivatives of coumarins, chromones, quinolines, quinolones, thietenes and isoxazoles are described. We also report the preparation of a series of mono- and diglycosylthiophenes by reacting HS^? with mono- and diglycosylbutadiynes. Acetylenic sugar derivatives have also been used for the synthesis of a diglycosylazaphosphorine and a spirooxolenone.