Hydrazine ketoses

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. 

In the presence of hydrazine hydrate, ketose (652) (49HCA1041, 49JA3977) and aldose (653) monosaccharides reacted with 624 to give the... 

The influence, on the reaction, of different substituents in the phenyl-hydrazine molecule and the specificity due to these molecular changes have been studied. The specificity in respect to certain aldose configurations was proved, and it was also shown that D-fructose and other 2-ketoses react with such weakly basic hydrazines as (p-bromo-, (p-carboxy-, (p-carbeth-oxy- and (p-nitro-phenyl)hydrazine. Correlations between the reaction rate and ease of interconversion between cyclic and acyclic forms were also determined. Studies with tritium-labeled D-fructose showed that the... 

According to Micheel, osazone formation starts from an aldose and requires an Amadori rearrangement, so that his scheme may not account for the reaction in the ketose series. It may be concluded that the Fischer mechanism is not valid, and that further studies are needed in order to solve the problem of interaction between ketoses and substituted phenyl-hydrazines. 

For selective oxidations in the carbohydrate field, Heyns and coworkers have investigated the use of platinum catalysts in different forms. For reactions in which further oxidation of the desired product is probable (as, for example, in the oxidation of ketose and pentose derivatives ), a milder catalyst of 5 to 10% platinum on activated carbon is recommended. Care must be taken in the preparation of the catalyst otherwise, it is difficult to obtain catalysts of reproducible activity. The platinum is deposited on the carbon by hydrogenation or by reduction with formaldehyde or hydrazine sulfate. The catalyst prepared through formaldehyde... 

Bloink and Pausacker suggested a mechanism similar to that of Braude and Forbes, in which the hydrazonium salt, instead of oxidizing the hydroxyl group, oxidizes the hydrazino hydrazone formed by the action of phenyl hydrazine on the phenylhydrazone by way of (7). The hydrazino hydrazone is also an intermediate in the Weygand scheme B (see p. 145) for ketoses, where it is produced by an Amadori rearrangement. 

Fischer s formulation of phenylosazones in the acyclic structure, such as (43), was based on the fact that the same osazone is produced from two epimeric aldoses and the corresponding 2-ketose, as well as from their phenylhydrazones, indicating that, in the osazone, the phenyl-hydrazine residues are attached at C-1 and C-2 of the saccharide chain. As the asymmetry at C-2 is destroyed during the reaction, it is found that, for a given substituted hydrazine, there are eight isomeric hexose osazones (four D and four l isomers) and four pentose osazones (two d and two l). 

Saccharide hydrazones are prepared by treating aldoses, ketoses, al-dosuloses, or reducing disaccharides with unsubstituted hydrazine 81 82 with monosubstituted hydrazines having alkyl,81 acyl,30-83 84 aroyl85 sul-fonyl,36,39-40,86 8 aryl,89-93 or disubstituted tyiV-dialkyl-,81 AUY-diaryl-,94 or... 

Dinitrophenyl-hydrazine 2,4-dinitro-phenylhydrazine (0.4%, m/v) in HCI (2moir ) Heated at 105°C for 5 min Ketoses or ketals - orange 1-2 pg for most keto compounds... 

The solubility characteristics of the reaction products of the sugars with unsubstituted hydrazine (NH2—NH2) are not favorable for identification purposes. The aldoses form aldazines, and the ketoses ketazines, in which 2 moles of the sugar are combined with 1 mole of the hydrazine 246). However, hydrazine reacts readily with sugar lactones to give characteristic derivatives useful for identification. The lactones may be regenerated from the hydrazides by treatment with nitrous anhydride 247). 

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