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.     

Equilibres conformationnels de dérivés de sucres à insaturation terminale

The conformation in solution of several unsatured sugars of the general type XHC?CH—glycosyl has been studied by NMR. In the trans series, the population of the sterically permitted gauche conformer increases with the M-ability of X. In the cis series, the population of the trans conformer increases with the space requirements of X. These phenomena are discussed.     

Dérivés C-Glycosyliques XXXI. Utilisation en chimie des sucres du synthon bromo-2-cyano-2-éthényle. Communication préliminaire

C-Glycosyl derivatives XXXI. Some uses in Carbohydrate Chemistry of the 2-bromo-2-cyano ethenyl synthon Sugars bearing the synthon 2-bromo-2-cyano-ethenyl, ? CαH?Cγ(Br)C?N, reacted with binucleophiles, gave rise to α, α, α, β or α, γ ring-forming reactions. C-glycosyl-dioxolanes, -aziridines, -dithianes, -pyrimidines, -furanes and -pyrazoles were so obtained. The stereochemical paths of some of these reactions are discussed.     

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.     

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.     

Déconjugaison d'énones dérivées de sucres Communication préliminaire

Deconjugation of sugars enones. Preliminary Communication Branched-chain sugar enones 1 and 2 ( R = Ac) deconjugated toposelectively (only the E isomers reacting) to 3 . The same phenomenon was noted in the case of Z- 4 which gave E- 5 . The kinetic parameters of these reactions favored a concerted mechanism, i.e. a [1, 5]-sigmatropic shift.     

Dérivés C-glycosyliques. VII. Synthèse et réactions de nitrones dérivées de sucres. Communication préliminaire

The syntheses of three types of sugar nitrones (aldonitrone, ketonitrone and α-β unsaturated aldonitrone) are described. On 1,3-dipolar cycloaddition with phenylacetylene, the aldonitrone gave two Δ₄-isoxazolines epimeric at the new asymetric carbon, while the same reaction on the ketonitrone led to a spiro-Δ₄-isoxazoline. The reaction of these nitrones with carbon nucleophiles like phenylethynylmagnesium bromide constitutes a novel chain-extension reaction in carbohydrate chemistry.     

Triazènes et benzotriazines dérivés de sucres

Sugar triazenes and benzotriazines Several triazenylsugars have been prepared, generally in good yields, by treating an amino sugar with a substituted benzenediazonium salt. The triazenylsugars bearing a hydrogen atom on the triazenyl group are acetylated on the nitrogen atom closest to the glycosyl moiety (N(1)), even when the proton exchanged sites between N(1) and N(3). When an acetyl or a methoxycarbonyl group was present in the ortho position of the benzene ring cyclization took place leading to a 3,4-dihydro-4-methylidene-1,2,3-benzo[d]triazine or a 3,4-dihydro-1,2,3-benzo[d]triazin-4-one respectively.     

Systèmes Aromatiques à 10 Électrons π Dérivés de l'Aza-3a-pentalène: XXVI—Etude de quelques Dérivés Polyazapentaléniques en Résonance du Carbone-13

The ¹³C n.m.r. study of nine azapentalenes was carried out and all the signals were assigned. In one case, very unusual couplings between the carbon atoms and the proton bonded to the pyrrole nitrogen atom were observed. The usefulness of ¹³C n.m.r. spectroscopy for the study of annular tautomerism is demonstrated.     

Ylides du soufre dérivés de sucres Communication préliminaire

S-Methylation of 6-S-benzyl-6-deoxy-1,2-O-isopropylidene-3-O-methyl-α-D-xylo-6-thiohexofuranos-5-ulose ( 1 ) gave the expected sulfonium salt 2 which on alcaline treatment yielded the stable sulfur ylide 3 . This compound constitutes an useful synthetic intermediate in carbohydrate chemistry. On heating in 1,2-dimethoxyethane, it underwent a Stevens rearrangement which led to an extension of the carbon chain of the sugar and, reacted with Michael acceptors, it gave cyclopropanation reactions.     

Dérivés C-glycosyliques XXIII. Radicaux libres stables dérivés de sucre Communication préliminaire

Treated with 2,3-dimethyl-2,3-bis-(hydroxylamino)-butane, aldehydo-dialdofuranoses ( 1 ) gave a mixture of two compounds: a 1,3-dihydroxyimidazolidine ( 2 ) and a 1-hydroxyimidazoline ( 3 ). Oxidation (PbO₂) of compounds 3 gave stable free radicals having the structure of 2-C-Glycosyl-4,4,5,5-tetramethylimidazolines 1-oxyl ( 4 ), whereas 2-C-Glycosyl-4,4,5,5-tetramethylimidazolines 3-oxide 1-oxyl ( 5 ) were formed by oxidation of 2 . The ESR. spectra of compounds 4 and 5 establish the structure of the imidazoline part of these radicals and provide informations on the sugar moiety.     

Substitutions homolytiques intramoléculaires. 17. Décomposition de peroxydes de ϵ-alcényle et de t-butyle. Accès à des tétrahydropyranes substitués

The induced decomposition of t-butyl hex-5-enyl peroxide in good hydrogen donor solvents led to 2-substitude tetrahydropyrans and adduct peroxides. The presence of substituents on the hexenyl moinety influenced seriously the relative ratio of the heterocycle and the adduct peroxide.     

Etude théorique des cycloadditions à partir dM'ylures d'azinium ou de composés homologues

Using a perturbation model the theoretical studies of the title reactions have been carried out and the results compared with experimental data.     

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.     

Dérivés de l'hydroxyméthyl-5 furfural. I. Synthése de dérivés du di- et terfuranne

Addition of α, β-unsaturated sulfones or ketones to 5-hydroxmethyl-furaldehyde or related furanaldehydes in the presence of a thiazolium salt gives di or tetraketonic furan compounds. Dehydrative cyclizationled to di- and terfuryl derivatives.     

Dérivés C-glycosyliques VIII. Synthèse de C-glycosyl-3-pyrazoles à partir d'une nitrilimine dérivée de l'anhydro-2,5-D-ribose. Compétition entre cyclo-additions dipolaires-1,3 et cyclisations non concertés

Several 3-(2,5-anhydro-ribosyl)-pyrazoles of potential medicinal interest have been synthesized by reacting alkynes or alkynylmagnesium bromides with the p-nitrophenylhydrazone of 2,5-anhydro-ribonyl bromide. From a mechanistic standpoint, it has been shown that the sugar-nitrilimine used in these studies reacts more readily as an electrophile than as a dipole. Thus, the hydrazonyl bromide gave exclusively the corresponding phenylethynylhydrazone when treated with phenylethynylmagnesium bromide and led to a 1:1 mixture of phenylethynylhydrazone and pyrazole when reacted with phenylacetylene. This proves that nucleophilic additions onto nitrilimines are much faster than Huisgen's 1,3-dipolar cycloadditions.     

Esters phosphoriques,phosphonates et oxydes de phosphine dérivés de sucres. Communication préliminaire

Some sugar phosphates, phosphonates and phosphine oxides, Preliminary communication Some new phosphates of 1, 2-O-isopropylidene-α-D-ribofuranose have been prepared. Reactions of 3-C-cyanomethylidene-3-deoxy-1, 2-O-isopropylidene-5-O-trityl-α-D -erythro-pentofuranose (9) have been studied. On treatment with phosphorus nucleophiles, 9 led to phosphorus bearing branched-chain sugar derivatives. Branched-chain cyanosugars as 15 and 16 prepared by cis-vic-dihydroxylation of 9 constitute interesting potential precursors of new types of cyclic sugar phosphates.     

Etude de la fragmentation par impact électronique de dérivés du benzothiazole

Study of Electron-Impact Fragmentation of Benzothiazole Derivatives The mass spectra of eighteen substituted benzothiazoles are reported and discussed. All these compounds are thermodynamically stable and give an intense molecular ion, which undergoes different types of fragmentation depending on the nature of the substituent which is rarely eliminated directly. β-Cleavage with respect to the heterocyclic double bond is often observed. Specific ²H-, ¹³C-, ¹⁵N- and ³⁴S-labelling have been used in order to confirm the fragmentation patterns.     

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 diglycosyliques. Communication préliminaire

Diglycosyl Derivatives. Preliminary communication Novel types of diglycosyl compounds, some of them bearing a resemblance to natural di- or tri-saccharides are described: a diglycosyldiyne ( 1 ), a diglycosylthiophene ( 2 ), a diglycosylaziridine ( 3 ), a diglycosyldioxolane ( 4 ), as well as six C,N-diglycosylnitrones, 9b–9f and 14 . These C,N-diglycosylnitrones, on treatment with an acetylenic Grignard reagent, led to the expected acetylenic diglycosyl-hydroxylamine 11 , whereas diglycosylisoxazolines (f. ex. 10 ) were obtained when these nitrones underwent 1,3-dipolar cycloaddition to acetylenic compounds.