Xylose phenylosazone

Fischer and Armstrong17 suggested the application of the benzaldehyde method for the decomposition of D-xylose phenylosazone, and a slight modification of this method180 was later employed in obtaining D-xylosone for the synthesis of D-isoascorbic acid,12-181-182 and L-xylosone182 for the... 

Although Fischer described a lactose phenylosazone anhydride in 1887, little attention was paid to substances of this type until 1935 when Diels and Meyer reported the isolation of monoanhydrides of D-glucose phenylosazone, D-galactose phenylosazone, D-xylose phenylosazone, L-arabinose phenylosazone, lactose phenylosazone, and cellobiose phenylosazone, as well as a dianhydride of maltose phenylosazone, by boiling the corresponding osazones in alcoholic solution with a little sulfuric acid. Because of the apparent identity of the D-glucose phenylosazone anhydride with the 3,6-anhydro-D-glucose phenylosazone of Fischer and Zach, Diels and Meyer formulated these compounds as 3,6-anhydrides. 

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... 

Osotriazole aus 1-Xylose-, f-Rhammose- und d-Chinovose-phenylosazon, by E. Hardegger and H. El Khadem, Helv. Chim. Acta, 30 (1947) 900-904. 

The phenylosazone from D-xylose 39 can be converted into the pyrazoles 313 [242]. Isoma-Itulose 314 affords the glycosylated aromatic compound 315 [243]. On acidic acetylation the ulosonic acid ester 316 forms concomitantly the glycal derivative 317 and the furanoic acid derivative 318 [244] (O Scheme 63). 

Pyrazole from xylose. The phenylosazone of o-xylose is converted to a pyrazole on... 

The rate of formation of osazones and their solubility, which differ substantially from case to case, can also serve as characteristic features useful in the identification of sugars. For example, osazones of glucose and fructose precipitate shortly after the heating of the solution, while saccharose requires 20 — 30 min of heating. Osazones of lactose and maltose precipitate only after cooling. In addition, phenylosazones of D-glucose, D-fructose, and D-mannose (which are identical) are insoluble in cold acetone, in contrast to phenylosazones of xylose, arabinose, rhamnose, and fructose. 

Fig, 13, Formation and periodate oxidation of n-lAreo-pentose phenylosazone. Xylose (1) was converted to the osazone (2) which was oxidized with periodic acid to yield formate and mesoxalaldehyde l,2-bis(phenylhydrazone) (3),... 

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