Synthèse de l'apiose et de composés voisins par des réactions de wittig

Treatment of 1,2-O-isopropylidene-α-D-glycero-tetros-3-ulofuranose (7) with cyanomethylenetriphenylphosphorane gave in excellent yield a mixture of the geometrical isomers of the corresponding cyanomethylenic derivative. After treatment with potassium permanganate, and then with sodium borohydride, this unsaturated, branched-chain sugar derivative was stereospecifically converted into 3-C-hydroxymethy]-1,2-O-isopropylidene-β-L-threofuranose. Similarly, treatment of the L-enantiomer of 7 with methylthiomethylenetriphenylphosphorane gave the expected methylthiomethylenic analogs, from which 3-deoxy-3-C-methyl and 3-deoxy-3-C-dimethoxymethyl derivatives were prepared. Wittig reactions thus allow the synthesis of branched-chain sugars bearing the side-chain on the more hindered side of the ring, compounds which are difficult to obtain by other methods.     

Synthèse et propriétés physicochimiques de 5,6-didésoxy-6-halogéno-hept-5-éno-1,4-furanurononitriles

The four 5,6-dideoxy-6-halogeno-1,2-O-isopropylidene-3-O-methyl-α-d-xylo-hept-5-eno-1,4-furanurononitriles (bromo, chloro, fluoro, and iodo) were prepared by treatment of 1,2-O-isopropylidene-3-O-methyl-α-d-pentodialdo-1,4-furanose with the corresponding (cyanohalogenomethylene)triphenylphosphorane. The geometrical isomers were separated by liquid chromatography. Spectral data of the four nitriles and of corresponding enurononitriles were used for identification of configuration and conformation.     

Dérivés du 2,5-anhydro-D-ribononitrile N-oxyde

When the mixture of syn and anti isomers of 2,5-anhydro-3,4-O-isopropylidene-aldehydo-D-ribose oxime was treated with chlorine, two gem-chloronitroso derivatives, epimers at C-1, were formed; they were in equilibrium with three dimers and were transformed by prototropy into the corresponding hydroxymoyl chloride. Treatment of the latter compound with a base gave a nitrile oxide which forms a dimer, or undergoes transformation into a furazan, or reacts with phenylacetylene to give a mixture of an acetylenic oxime and of the corresponding 3-glycosyl-5-phenylisoxazole.     

Dérives C-glycosyliques : XIII. Nitrones de sucres

Various N-methylnitrones of sugars having a free carbonyl group were prepared by treatment with N-methylhydroxylamine. In each case, only one geometric isomer was obtained, to which the anti (Z) configuration is ascribed on the basis of the n.m.r. spectra, in particular of those obtained in the presence of an europium complex.     

Dérivés d'acides 3-(β-d-érythrofuranosyl)-pyrazolecarboxyliques

Treatment of 2,5-anhydro-1-bromo-1-deoxy-2,3-O-isopropylidene-1-p-nitrophenylhydrazono-d-ribose with methyl acetylenecarboxylate gave methyl 3-(2,3-O-isopropylidene-β-d-erythrofuranosyl)-1-p-nitrophenylpyrazole- (8) and 5-carboxylate (9). Amidification at C-5 of 8 was easier than at C-4 of 9. Similarly, dimethyl 3-(2,3-O-isopropylidene-β-d-erythrofuranosyl)- 1 - p-nitrophenylpyrazole-4,5-dicarboxylate gave specifically a 5-carbamoyl derivative, the structure of which was established by comparison of the ¹³C-n.m.r.spectrum with those of a series of glycosylpyrazoles. The correlation between the experimental values of the chemical shifts of the carbon atoms of the pyrazole ring and the values calculated by addition of the contributions of the various groups linked to the ring was better (R 0.98) than the correlations obtained by calculation by the CNDO/2 method of the total electron population (R 0.92) or of the π-electron population of each carbon atom (R 0.85).     

Influence des effets orbitalaires sur l'équilibre conformationnel des sucres à insaturation terminale de configuration E

The glycenoses and alkenes bearing an alkoxy group on the allylic carbon atom and having the general formula RCH(OR)′CHCHX (E configuration) preferentially adopt, in solution, a conformation in which the alkoxylgroup eclipses the double bond. This conformation is particularly favored when X is an electron-withdrawing group by resonance; it becomes less favored or totally unfavored when X is electron-donating by resonance. This phenomenon, which cannot be attributed to steric hindrance, is explained by inter-orbital interactions.     

The molecular-weight range of mucosal-heparin preparations.

A recently reported method describes the determination of the molecular-weight range of heparins by using an electrofocusing procedure to isolate individual molecular species. Commercially available heparins were fractionated on a column of polyacrylamide-agarose gel to give fractions whose molecular weights were estimated by viscometry. Fractions with mutually exclusive molecllar-weight ranges gave an appreciable number of common bands when subjected to the electrofocusing procedure; therefore, each of these bands cannot be formed from a single molecular species of heparin. Other mucopolysaccharides also gave band sequences indistinguishable from those of heparin; they differed in position and intensity with different ampholyte batches, and probably arose from individual molecular species of the ampholyte rather than the mucopolysaccharide. The molecular-weight range of the heparin was observed to be broader than that usually reported.     

Structural studies of the klebsiella type 47 capsular polysaccharide

The structure of the capsular polysaccharide from Klebsiella Type 47 has been investigated. Methylation analysis and characterization of oligosaccharides obtained on acid hydrolysis were the principal methods used. The polysaccharide is composed of tetrasaccharide repeating-units, and a structure for these units is proposed.     

2-amino-2-desoxy-6-O-(D-glykofuranosylurono-6,3-lacton)-D-galaktopyranosen

Condensation of 2-amino-2-deoxy-D-galactopyranose with D-glucuronic acid or D-mannurono-6,3-lactone in the presence of hydrochloric acid gave the corresponding 2-amino-2-deoxy-6-O-(D-glycofuranosylurono-6,3-lactone)-D-galactopyranoses. The α-D configuration of the disaccharide derived from D-glucuronic acid was determined by its resistance towards β-D-glucuronidase.     

Chlorination and phosphorylation of cotton cellulose by reaction with phosphoryl chloride in N,N-dimethylformamide

Native cotton yarn reacts rapidly with phosphoryl chloride in N,N-dimethylformamide to produce highly chlorinated cellulose (degree of substitution of 0.5 or greater), phosphorylated cellulose, and cellulose formate. The ratio of chlorination to phosphorylation was readily controlled by varying the concentration of phosphoryl chloride in N,N-dimethylformamide.Reaction variables studied were the reagent concentration, reaction temperature, and reaction time. The effect that each of these variables has on the tensile and flammability properties of the resultant yarns was investigated. Yarns containing large proportions of chlorine have high tensile-strength and are unusually extensible, whereas yarns containing phosphorus have high flame-resistance. A mechanism for the selective chlorination or phosphorylation of the cotton cellulose is advanced.     

Marqueurs Á spin construits directement sur le squelette carboné de sucres

Treatment of aldehydo-sugars with 2,3-bis(hydroxyamino)-2,3-dimethylbutane gave the corresponding 1,3-dihydroxyimidazolidines. Oxidation of these compounds gave, successively, unstable, free radicals having a 3-hydroxyimidazolidine 1-oxyl structure, then stable, free radicals having a 2-glycosyl-2-imidazoline 3-oxide 1-oxyl structure, which were reduced to stable 2-glycosyl-2-imidazoline 1-oxyl compounds. The orientation of the two last-named series of compounds around the σ bond between carbohydrate and heterocyclic residues that bears the radical centre is indicated by the value of the hyperfine coupling aH of the carbohydrate proton nearest to the nitrogenous heterocyclic residue. The study of numerous compounds of both series shows that the value of the hyperfine coupling depends greatly on the structure of the carbohydrate residue. A general explanation based on the preponderance of eclipsed forms and on the primary influence of steric hindrance due to the substituents of the carbohydrate residue is proposed. This study also gives some indirect information on the conformation of diamagnetic compounds that show little sterical difference, and about which ¹H-n.m.r. spectroscopy does not provide useful information.