Osazones reduction

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). 

Hydrolysis of the diacetamides is effected by acids. Dilute hydrochloric, sulfuric and nitric acid have been used. An aldose with one carbon atom less than the original nitrile is then liberated from the combination. Only exceptionally can this aldose be isolated in pure condition without transforming it into an insoluble derivative in these instances, the method has been employed for preparative work. In most cases the sugar has been characterized as an osazone. The aldose, without great purification, has been employed successfully for reduction - or oxidation experiments. ... 

Another 2,3-bis(phenylhydrazone), namely, l,5 4,6-dianhydro-2,3-hexodiulose bis(phenylhydrazone) (62a), was also found to cyclize to a pyrazoline (63a) by the action of copper(II) sulfate or benzalde-hyde, which usually convert osazones into aldosuloses or osotria-zoles.65 Reduction of this bicyclic compound (63a) led to the pyrazo-lidine 64, and periodate oxidation of 63a gave the expected aldehyde 65. 

Problem 22.34 (a) Write shorthand structures for the three o-2-ketohexoses other than o-fructose. (b) Which one does not give a meso alditol on reduction (c) Which one gives the same osazone as does D-galactose (Problem 22.22)7 <... 

Reaction (reduction) with phenylhydrazine (osazone test) The open chain form of the sugar reacts with phenylhydrazine to produce a pheny-losazone. Three moles of phenylhydrazine are used, but only two moles taken up at C-1 and C-2. 

A hexose, C6H1206, which we shall call X-ose, on reduction with sodium amalgam gives pure D-sorbitol, and upon treatment with phenylhydrazine gives an osazone different from that of D-glucose. Write a projection formula for X-ose and equations for its reactions. 

It will be observed that the hypothesis of intramolecular transformation advanced by us to explain the interconversion of glucose, fructose and mannose should be modified or rather extended. It would seem appropriate to postpone these theoretical considerations until the constitution of the new sugars has been established. It is to be noted, however, that the theory takes into consideration the existence of a great number of ketoses, it being possible for an intramolecular transformation of the kind indicated to take place among several carbons in the chain of the sugar. Fructose, for example, can produce in this way two new ketoses with a C==0 on carbon 3, which can be transformed, by reduction, into four different hexitols, and yet can form one and the same osazone. 

This sugar is also an aldo-pentose and is stereo-isomeric with arabinose. It is known as wood sugar because it is obtained by the hydrolysis of wood gum, i.e.f of the pentosans present in this gum. It is crystalline and melts at 140°- 60°. It is optically active, being dextrorotatory. Its osazone melts at 160°. By reduction it yields a penta-hydroxy alcohol and by oxidation it yields tri-hydroxy glutaric acid. 

The aldopentose (—)-ribose forms the same osazone as (--)-arabinose. Since (— )-arabinosc was shown to have configuration X, ( — )-ribose must have configuration IX. This configuration is confirmed by the reduction of (—)-ribose to the optically inactive (meso) pentahydroxy compound ribitol. 

The typical aldehyde reactions of D-(-H)-glucose—osazone formation, and perhaps reduction of Tollens and Fehling s reagents—are presumably due to a small amount of open-chain compound, which is replenished as fast as it is consumed. The concentration of this open-chain structure is, however, too low (less than 0.5%) for certain easily reversible aldehyde reactions like bisulfite addition and the Schiff test. 

An improved synthesis of dehydroascorbic acid has been reported (42). The oxidation of ascorbic acid in absolute methanol with oxygen over activated charcoal catalyst is reported to aflFord 28 in 95% yield. Dehydroascorbic acid has been characterized in solution as the monomer, 28 (43), and as the dimer (44,45) and its tetra acetyl derivative 29 (46). Several studies of mono- and di-hydrazone (48-53) and osazone (54) derivatives of dehydroascorbic acid have been reported. Hydrazone derivatives of dehydroascorbic acid have been used in the reductive synthesis of 2,3-diaza-2,3-dideoxy- and 2-aza-2-deoxyascorbic acid derivatives 30, 31, and 32 (55,56). Recently the reaction product of dehydro-L-ascorbic acid and L-phenylalanine in aqueous solution has been isolated and identified as tris(2-deoxy-2-L-ascorbyl)amine, 33, based on spectral and chemical data and its symmetry properties (57). 

At a temperature of —20° C. and in chloroform solution, the y-pyrones take up 2 molecules of ozone. This means that only the C=C bonds react with ozone, which was also found when ozone reacted with other heterocyclic rings, such as pyridine, pyrrole, and furan. The ozonides were decomposed by reduction with hydriodic acid, whereby carbonyl compounds are formed, as well as acetic acid and in some cases formic acid. By reacting the carbonyl compounds with p-nitrophenylhydrazine, the corresponding nitrophenylhydrazones or p-nitrophenylosazones are formed. The separation of the mixture of hydrazones and osazones is carried out by a chromatographic method. The quantitative determination of the separated nitrophenylosazones (or hydrazones) is carried out by means of spectrographic measurements. 

The apparent dissociation constant of different substituted osazones has been measured in acetic acid, and shown to follow Hammett s equation. The reduction potential has been followed polarographically and used, as noted previously (see p. 159), to demonstrate the chelated nature of osazones. 

By the catalytic reduction of the phenylosazone from lactose, Kuhn and Kirschenlohr obtained both /3-n-gaIactopyranosyl-(l— 4)-l-amino-l-deoxy-D-fructose and /S-n-galactopyranosyl- (1- -4) -2-amino-2-deoxy-D-glu-cose. The A -acetyl derivative of the latter was found to be identical with a disaccharide obtained from the partial hydrolysis of a blood-group substance. The structure of a disaccharide obtained from the partial hydrolysis of heparin was likewise confirmed by comparison of the disaccharide with a synthetic product obtained by catalytic hydrogenation of the osazone from maltose. - Here, too, both the 1-amino-l-deoxy and the 2-amino-2-deoxy compounds were obtained. 

---