Propriétés chimiques du benzisosélénazole-1,2

The nitration and the bromination of 1,2-benzisoselenazole give mono derivatives at 5- or 7-position. With potassium amide 3-amino-1,2-benzisoselenazole is obtained from the unsubstituted ring. We observe a ring opening by action of organolithium compounds. We describe also the synthesis of functional derivatives at the 3-position from 3-styryl-1,2-benzisoselenazole and selenonaphthenequinone.     

Dérivés du C-méthyl-3-xylofurannose

3-C-Methylxylofuranose Derivatives 3′-C-methyladenosine has been known for almost ten years whereas its 3′-epimer is still to be prepared, because of the difficulty of synthesizing the 3-C-methylxylo-furanose. In this communication, the synthesis of 1,2-O-isoproypylidene acetal 9 and its derivatives is described. Vicinal dihydroxylation of 5-O-benzoyl-3-deoxy-1,2-O-isopryopylidene-3-C-methylidene-α-D -erythro-pentofuranose ( 6 ) led to the branchedchain sugar derivative 7 which was selectively tosylated to 8 whose reduction gave 9 . These reactions, as well as the derivatizations of 7 , 8 and 9 , took place with good to excellent yields.     

Dérivés d'énose- et d'ynosephosphonates et composés voisins. Communication préliminaire

Derivatives of enose- and ynosephosphonates and related compounds. Preliminary communication The gem-dibromo terminal enoses 1 and 7 are convenient sources of glycosylacetylenes which upon reaction with phosphorus electrophiles gave the phosphorusbearing acetylenic sugars 4, 5 and 8 . Compounds 5 and 8 underwent cycloaddition reactions leading to isoxazolyl-C-glycosides 6 and 9 respectively. The nitroolefinic sugar derivative 11 gave upon bromination-dehydrobromination the first example of a new kind of potentially useful synthetic intermediates, the gem-bromonitroenose 12 . The enosephosphonate 13 was also prepared from 11 . The diglycosylhydroxylamine 18 represents another type of phosphorus-bearing acetylenic sugar derivative. Some ¹H- and ¹³C-NMR. data relative to the new types of phosphorus-containing sugar derivatives synthesized are given.     

RMN du 13C de Composés Méthylés Soufrés

A ¹³C NMR study of a series of methyl sulphur compounds is described. The results are discussed in terms of the deshielding effects on the methyl carbon exerted by –SH, –SMe, –SSMe, –SSEt, –SSMe, –SC(O)Me, –SC(S)Me, –SC(S)SMe. The ¹³C NMR chemical shifts of a series of S-methyl thioesters and dithioesters are compared with corresponding esters and connected with chemical properties.     

Dérivés de sucres benzimidazoliques et benzothiazoliques

Benzimidazole and benzothiazole sugar derivatives Simple aldehydosugars such as 1 or 2 , by reaction with o-phenylenediamine, gave the corresponding benzimidazoles 3 and 4 . Whereas the unperturbed α, β-unsaturated aldehydosugar D gave the benzodiazepine E upon treatment with o-phenylenediamine, the formyl-bearing alkenyl acetals 5 and 8 led, in the same conditions, to the benzimidazoles 6 and 9 respectively or, on reaction with o-aminothiophenol, to the benzothiazoles 7 and 10 respectively. This difference in reactivity is explained by the electrondonor ability of the oxygen atom of the alkenyl acetal function as shown by the ¹³C-RMN. spectra.     

Étude en RMN du 13C de Dérivés de la Pipéridone-4 Stériquement Encombrés et des Oximes Correspondantes

The regiospecific differences in chemical shifts caused by the oximino group, such as Δδ as Δδ parameters, are useful to estimate conformational distortions directly from ¹³C spectra. Particularly, twist-boat conformations resulting from oximation of sterically hindered piperidones are unambiguously detected.     

Synthèse d'hydroxyspirocétals insaturés et hétérocyclisation en méthyl-5 trioxa-2,6,11 tricyclo[5.3.1.01.5]undécane

The photochemical irradiation of unsaturated ketoacetals 4 gives unsaturated hydroxyspirocetals 6 . The mixture of these stereoisomers yields by thermal or ionic treatment a trioxatri-cyclo compound 7 .     

Dérivés C-glycosyliques. XXIV. Glycosyl-4-thiazoles

4-C-glycosylthiazoles have been prepared by reacting thiourea or thioacetamide with a 6-S-benzyl-6-chloro-1,2-O-isopropylidene-3-O-methyl-α-D-xylo-6-thiohexofuranos-5-ulose (7). The latter compound which constitutes an interesting synthetic intermediate in carbohydrate chemistry has been obtained by successive oxidation and chlorination of 6-S-benzyl-1,2-O-isopropylidene-3-O-methyl-α-D-6-thioglucofuranose.     

Cyclisation des amides d'acides phénylthio-1 glyoxaliques avec les dérives carbonylés

The carbonyl-containing compounds react with the amides of phenyl-1-thioglyoxalic acids ( 3 ), and if methyl iodide is present, cause cyclisation into 4-methylthio-5-phenyl-2,5-dihydrooxazol-5-ols ( 4 ). The ketal hydroxyl group of the latter can be methylated. When a hydrogen atom exists in the 2-position (cyclisation with an aldehyde), its elimination provides an oxazole 7 .     

Influence de composés à hétérocycle azoté et particulièrement d'azoles non condensés sur des réactions «prébiotiques» de condensation d'acides α-aminés induites par les polyphosphates en milieu aqueux

Influence of Nitrogen Heterocyclic Compounds and of Non Condensed Azoles in Particular on ‘Prebiotic’ Condensation Reactions of α-Amino Acids Induced by Polyphosphates in Aqueous Solution In previous experiments aqueous solutions of α-aminoacids in the presence of cyclic or linear polyphosphates, pH range 7–11, yielded up to 40% of dipeptide but only 0.3-0.5% of tripeptide [1] [2]. By addition of imidazole the yield of tripeptide could be increased about ten times [2]. Therefore, we have studied for the condensation reaction of glycine the influence of the addition to aqueous solutions 0.1 M in glycine and 0.1 M in trimetaphosphate at room temperature, pH range 6.7–8.9, of several azoles (pyrrole, pyrazole, imidazole, 1,2,4-triazole and tetrazole), of adenine, guanine, uracil, cytosine, and of several nucleosides (adenosine, guanosine, uridine and cytidine). Among the products studied, only 1,2,4-triazole and imidazole improve appreciably, by a factor of about 15, the yield of triglycine (up to 7.8%). While it is very likely that imidazole has played an important role during prebiotic chemical evolution, it is not clear at present whether 1,2,4-triazole has a prebiotic significance.     

Polymétallorotaxanes conjugués contenant des unités pentacoordinantes

Conjugated polymetallorotaxanes containing pentacoordinating units. The present paper reports the synthesis and cyclic voltammetry study of new conjugated polyrotaxanes containing penta-coordinating units around copper or zinc centres. The gathering and threading effect of these metal centres has been used to prepare the desired prerotaxanes, whose macrocyclic and linear components incorporate a tridentate chelate of the terpy type (terpy = 2,2′,6′,2″-terpyridine) and a phen (phen = 1,10-phenantroline) derivative, respectively. Electrochemical oxidative coupling of the end groups (thiophene or pyrrole) leads to the corresponding polymers. Ion-exchange processes, induced by demetalation/remetalation, have been investigated as well as the conductivity of the polymer films prepared.     

Réduction alkylante de quelques composés hétéroaromatiques polyazotés

The reduction-aldylation of quinoxaline, phthalazine and pyrido[2,3-b] pyrazine by potassium borohydride in a carboxylic acid medium is described. Formic, acetic, chloroacetic and propinic acids were used. The diazine ring of the molecule was reduced and alkylated into an N,N¹-dialkyltetrahydro compound. With quinoxaline and formic acid, N-formylation may be an important factor. Sodium borodeuteride allows one to prepare an hexadeuterated compound.     

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.     

Structure électronique de dérivés sulfurés : Partie V. spectres électroniques d''hétérocycles thio-carbonylés

The experimental and theoretical spectra of thiocarbonyl heterocyclic compounds with two heteroatoms in the position to the thiocarbonyl group have been studied.

The theoretical interpretation of the CNDO/S results including an extension to the third period, i.e. 3d orbitais, is in good agreement with the saturation effect as well as with the influence of the intracyclic heteroatoms on the typical absorptions of the thiocarbonyl group.     

Analogues azotés de dérivés de l'acide orotique

The synthesis of two new types of compounds with 3-oxo-5-thioxo- and 3,5-dithioxo-6-ethoxycarbonyl-2,3,4,5-tetrahydro-1,2,4-triazines are described. Their reactivity towards alkylating reagents and towards hydrazine has been studied.     

Thiazoles polycycliques. I. Substitution par les nucléophiles anioniques des dérivés 2-méthylsulfonylés de la thiazolo[5,4-b]-pyridine et du benzothiazole

Substitution reactions of 2-methylsulfonyl thiazolo[5,4-b]-pyridine (3) and 2-methylsulfonyl benzothiazole (10) by nucleophilic anionic reagents were studied. In N,N-dimethylformamide, at 20°, these reactions are fast, particularly with compound 3 . Also studied were the kinetics of the substitution by sodium methylate, and the pK_a′s of the acidic compounds. This work allows the comparison of benzothiazole with its “7-aza” analog.     

Couplages J des groupes méthyle dans les phényltriméthylsilanes p-substitués: Effets de solvants

The J coupling constants of a series of p-substituted phenyltrimethylsilanes were measured in CH₂Cl₂ and CCl₄ solutions. The solvent effect is discussed; it is too large to allow any straightward conclusion on ring-substituent interaction.     

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.     

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.     

Radicaux libres dérivés de sucres. V. Dérivés d'osamines N-hydroxylées et composés voisins Communication préliminaire

Free sugar radicals. V. Deoxyhydroxylaminosugar derivatives and related compounds We describe several synthetic routes to deoxyhydroxylaminosugar derivatives of the type Glyc-N(OH)-R where Glyc stands for a sugar moiety linked by any of its C-atoms except the anomeric one and R for one of the following substituants: H-atom, acyl, phosphoryl groups, aminoacid or sugar residues. Compounds of the above structure are potentially close analogs, homoisosteres, ? NOH? replacing ? O? , of biochemically important molecules. Under aerobic conditions, solutions of these derivatives contain minute concentrations of the corresponding nitroxide radicals which do not decrease significantly the resolution of the NMR. spectra but render these compounds usable as a new kind of spin labels. Spectroscopic properties (¹H-NMR., ¹³C-NMR., ESR.) of some of these compounds are reported.