Osazones Osones

D,L-Mannitol has been obtained by sodium amalgam reduction of D,L-mannose. The identical hexitol is formed from the formaldehyde polymer, acrose, by conversion through its osazone and osone to D,L-fmctose (a-acrose) followed by reduction (83). 

The 2-keto acids such as 2-keto-D-galactonic acid (XXIV) can be derived from the corresponding osone (XXIII) by oxidation with bromine.10 Oxidation of L-gulosone by the same method has provided 2-keto-L-gulonic acid. The success of this oxidation depends to a large extent upon the purity of the osone subjected to oxidation and this, as previously stated, is controlled by the purity of the osazone. 

It has recently been reported21 that a mixed osazone of 3,4-di-O-methyl-D-glucose can be converted, by treatment with p-nitrobenzaldehyde, into an osone which reacts with phenylhydrazine to give 3,4-di-O-methyl-D-glucose phenylosazone. Von Lebedev29 claimed to have obtained D-glu-cosone 6-phosphate, isolated as an amorphous lead salt, by the action of hydrochloric acid on the phenylosazone prepared from D-fructose 6-phosphate. 

The benzaldehyde method has advantages, however, where high purity of the osone is desirable.98 When the reagent is employed, the purity of the osazone is of prime importance,90 and recrystallization from absolute ethanol may be usefully carried out for the xylose phenylosazones104 as well as for the arabinose phenylosazones.183... 

LaForge and Hudson194 prepared an osone from the phenylosazone obtained from sedoheptulose (D-aZ(ro-heptulose). The osone reduced Fehling solution strongly, formed the original osazone with phenylhydrazine, and gave a crystalline derivative with o-phenylenediamine. 

Lactosone was first prepared by the hydrochloric acid decomposition of the phenylosazone,1 although it had been noted that, in acid solutions, lactose phenylosazone forms an anhydride.197 Since its discovery,17 the benzaldehyde method has usually been employed,6-10-28 because it avoids the risks of osone hydrolysis and of alteration to the osazone. Lactosone is hydrolyzed by hot, dilute, mineral acid to D-glucosone and D-galactose.1-6 It reacts with cyanide to form an analog of iminoascorbic acid which, on acid treatment, is converted into a mixture of D-glucoascorbic acid and D-galactose.10... 

D-Galactosido-D-glucosone and D-glucosido-D-galactosone were prepared by Fischer and Armstrong203 by the action of benzaldehyde on the osazones of synthetic disaccharides. Both osones were hydrolyzed by emulsin. There is some doubt as to the precise structure of the parent sugars.206... 

Like all hydrazones, osazones lose phenylhydrazine when heated with hydrochloric acid. Naturally, it is not the sugar originally taken which is thus recovered, but an oxidation product, a so-called osone. In the example chosen the osone is ... 

Problem 22.12 Osazones are converted by PhCHO to 1,2-dicarbonyl compounds called osones. Use this reaction to change glucose to fructose. 

Attention should be given to the difference between osazones and osones. An osone is formed by reaction of an osazone with HCI, e.g,. glucosone. CH2OH(CHOH))CO CHO. 

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. 

Osones.—We are not yet done with the interesting reactions of these compounds for the osazones when warmed with concentrated hydrochloric acid, take up water and split off the two phenyl hydrazine residues and yield a compound containing both the aldehyde and the ketone groups of the original aldose and ketose sugars. The resulting compound is known as an osone. 

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