Glyoxal, phenylosazone

Several mechanisms34 have been proposed for this reaction. That of Weygand,36 in which an Amadori rearrangement is proposed, has considerable merit.37 Illustrations of unusual osazone formation are described by Bonner and Drisko.38 When phenyl /S-D-xylopyranosyl sulfone (XXII) or /J-D-glucopyranosyl sulfone (XXIV) is oxidized by periodic acid, a dialdehyde oxidation product (XXIII or XXV), which is susceptible toward further oxidation, is obtained. The reaction of XXIII or XXV with phenylhydrazine yields glyoxal phenylosazone and benzenesulfinic acid. Surprisingly, both XXII and XXIII react with phenylhydrazine to form D-xylosazone and D-glucosazone, respectively. 

Diels, Meyer and Onnen studied the effect of boiling alcoholic solutions of osazones with potassium hydroxide (1%). n-Glucose phenylosazone gave glyoxal phenylosazone and l,2-bis(phenylazo) ethylene, and in general, glyoxal phenylosazone was obtained in the other cases examined, except for cellobiose phenylosazone. Evidently fission takes... 

The non-aqueous oxidation of various ketones and aldehydes to hydroxyaldehydes and hydroxy ketones has been carried out in two steps the first step is a bromination and the second a hydrolysis, or replacement of the bromine atoms by hydroxyl groups. Fischer and Landsteiner " brominated acetal in the presence of calcium carbonate (reaction 20). The bromoaldehyde Avas then treated with cold barium hydroxide solution (reaction 21) the resulting glycolic aldehyde was identified by conversion to glyoxal phenylosazone (reaction 22) and by the formation of calcium glycolate, after oxidation with bromine (reaction 23). 

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. 

Although no D-glucosone was obtained by the action of formaldehyde on D-glucose phenylosazone,19 Briill28 successfully decomposed the osazone with an excess of pyruvic acid. An improved procedure has been described, and the decomposition of D-glucose phenylosazone with glyoxal has been reported.18... 

The extent of oxidation, when determined by the reaction of the product with phenylhydrazine, is 85%. Hydrolysis of the oxidized xylan should produce approximately equimolar quantities of D-glyceraldehyde and glyoxal. Experimental determination of glyceraldehyde indicates 67 % of the theoretical when the oxidized xylan is distilled with sulfuric acid and the evolved methylglyoxal measured as the phenylosazone. Glyoxal is isolated in 63% yield, when separated as the phenylosazone or as the dioxime. Aldehyde groups in the oxidized xylan may be further... 

Treatment of methyl sulfoxide solutions of D-mannose or other sugar phenylhydrazones or melibiose phenylosazone with potassium tert-butoxide and a trace of oxygen at room temperature showed no evidence of the paramagnetic species characteristic of glyoxal bis(phenylhydra-... 

Since deacetylation of LXXXII and subsequent ozonization and treatment with water afforded glyoxal (isolated as the phenylosazone) it followed that the ethylenic linkage must be between carbon atoms 2 and 3.204 Reduction of LXXXII, followed by deacetylation, yields ethyl 2,3-didesoxy-D-alloside (LXXXIII). Alternatively, LXXXI could be converted into 4,6-diacetyl-2,3-didesoxy-D-allose, which on glycosidation as above yielded ethyl 4,6-diacetyl-2,3-didesoxy-D-alloside. In this instance the product was a mixture of isomers, since on deacetylation, two forms (m. p. 72-72.5° and 90°, respectively) were isolated. Derivatives of 2,3-didesoxy-L-ribose81 have been prepared from 3,4-diacetyl-L-arabinal,... 

Glycothioses, I, 135 Glycuronide, III, 131 Glyoxal, methyl-, phytochemical reduction of, IV, 80 —, methyl-, III, 127 phenylosazone, III, 117, 122 Glyoxylic acid, ethyl ester, II, 89 IV, 128 Goepp, Rudolf Maximilian, Jr., obituary, III, xv-xxiii... 

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