Degradation osazones

The trihydroxypropyl derivative 63 was prepared from dehydro-L-ascorbic acid phenylosazone (62) by opening the lactone ring with warm alkali and acidifying the mixture after a few minutes, whereupon the pyrazolinone 63 separated immediately.63 The structure of this compound was established by degradation,63 and confirmed by a study of its n.m.r. spectrum.64 The p-tolyl-, p-(bromophenyl)-, and p-(iodophenyl)-osazones of dehydro-L-ascorbic acid were also converted into the corresponding l-aryl-4-phenylazo-3-(trihydroxy-propyl)-5-pyrazolinone, and their acetylation and benzoylation products were prepared.64... 

These compounds are formally derived from aldoses by oxidation of a secondary hydroxyl group to a ketone group. The well-known aldos-2-uloses (usually termed simply aldosuloses or osones in former usage) have long been known in the form of their bis(hydrazone) derivatives, the osazones. Deoxyaldosuloses have been implicated as intermediates in a variety of degradation reactions. Aldos-3-, -4-, and -5-uloses have been prepared, principally as intermediates for synthesis. 

Degradation of beet arabinan and yeast mannan afforded osazones which, on hydrolysis in ethanolic solution with a cationic exchange resin in the acid state, yielded arabinose and a mannobiose, respectively, together with glycerosazone. These results, and also the nitrogen content of the polymeric materials recovered after Barry degradations, show that... 

The sugar T is levorotatory and has the formula C HjoOj it reduces Tolicns reagent and Benedict s solution. T is oxidized by bromine water to optically active CsHioO, and by nitric acid to optically inactive C5HHO7. T forms an osa/one that is identical with the osazone obtained from another pentose, (- )-U. Degradation of (- )-U, followed by oxidation by nitric acid, yields optically inactive C4Ht,Oft. 

Acid hydrolysis, as described, gives a largely uncontrolled degradation. Stepwise degradation of oligosaccharides can often be achieved by the selective hydrolysis of their osazones on an acid-type ion-exchange resin. This procedure was used by Howard to confirm the structure proposed for a D-xylose trisaccharide. 

Later, Machell and Richards and Whistler and BeMiller isolated the compound as a sirup (in yields of about 1%) by treatment of maltose with 0.05 N sodium hydroxide and of cellobiose with 0.05 N potassium hydroxide. There was a divergence in the reported specific optical rotations (in water), namely, —24.1° and -fll°, respectively, which might be attributable to degradation of this labile compound during isolation or storage. The crystalline (2,4-dinitrophenyl)osazone prepared in both investigations was further characterized as its crystalline triacetate. ... 

The osazones are unstable toward alkalis and are rapidly degraded thereby. From the reaction mixture of n-aroWno-hexulose phenylosazone and ethanolic potassium hydroxide, Diels and coworkers isolated glyoxal phenylosazone and oxalic acid. Under similar conditions, the osazone from cellobiose yielded a colorless compound Ci7H2 08N2, formulated by Diels as (83), a structure which needs further confirmation. 

In a final study,arabinogalactan B was subjected to a Barry degradation (oxidation with periodate, followed by treatment with phenylhydra-zine-acetic acid). One-third of the L-arabinose was removed as the osazone, as a result of the degradation. Since no furanosidic linkages were hydrolyzed... 

Saccharide osazones (183) are relatively stable in cold concentrated alkalies. but degrade progressively with time. The degradation starts at the... 

Aldohexoses A and B form the same osazone. A is oxidized by nitric acid to an optically active aldaric acid, and B is oxidized to an optically inactive aldaric acid. Ruff degradation of either A or B forms aldopentose C, which is oxidized by nitric acid to an optically active aldaric acid. Ruff degradation of C forms D, which is oxidized by nitric acid to an optically active aldaric acid. Ruff degradation of D forms (-l-)-glyceraldehyde. Identify A, B, C, and D. 

Reduction of an aldose forms one alditol reduction of a ketose forms two alditols. Br2 oxidizes aldoses, but not ketoses ToUens reagent oxidizes both. Aldoses are oxidized to aldonic acids or aldaric acids. Aldoses and ketoses react with three equivalents of phenyUiydrazine, forming osazones. C-2 epimers form identical osazones. The Kiliani-Fischer synthesis increases the carbon chain of an aldose by one carbon— it forms C-2 epimers. The Ruff degradation decreases the carbon chain by one carbon. The OH groups of monosaccharides react with acetyl chloride to form esters and with methyl iodide/silver oxide to form ethers. 

When polyols were oxidized electrolytically at platinum electrodes in the absence of an electrolyte 111), aldoses and ketoses were formed and isolated as osazones or hydrazones. Acids also were formed, and, with erythritol, a keto acid was produced. When the oxidation was carried out in the presence of sodium bromide using carbon electrodes, ketoses were obtained free of degradation products 11 ). 

It had been previously established that quinic acid readily forms a lactone, called quinide. Quinide was shown to have a 7-lactone structure by conversion of the trimethyl ether to 3-hydroxy-4-methoxybenzoic acid (isovanillic acid). At the same time, this reaction established that the hydroxyl at carbon 6 and the carboxyl must be on the same side of the ring. Since the hydroxyl derivative obtained through the Grignard reaction consumes one mole of lead tetraacetate and from the results of the Curtius degradation, it follows that carbon 2 must have both a carboxyl and hydroxyl attached. Furthermore, since the resultant ketone cannot form an osazone, carbons 1 and 3 must be free of hydroxyl groups. By elimination, therefore, the remaining two hydroxyls must be at carbons 4 and 5. Finally, these must... 

Otsuka et al. (1986) used TLC to isolate and partially characterize degradation products of 2,3-diketo-L-gulonic acid (intermediates in the biosynthesis of ascorbic acid) the products were characterized by different spectrometric methods. Mandrou et al. (1988) devised a TLC procedure to determine ascorbic and dehydroascorbic acids in fruit juices and wine the sample was reacted with 2,4-dinitrophenylhydrazine to form the osazones the osazones were spotted on the TLC plate and quantified by. in situ densitometry at 494 nm. 

Glucose, mannose, and the ketose, fructose, form the same osazone. In alkaline solution the three are interconvertible through a common enol form, but further degradation and breakdown into smaller fragments occurs easily. 

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