Osazones preparation

The mixed osazones prepared by Henseke and Binte during studies on the osones and related compounds brought forth new facts regarding the mechanism of formation. They postulated a linkage of glycosyl to nitrogen, whereas the bond between a disubstituted hydrazine residue and C-2 is veiy labile and is subject to hydrazone wandering. 

Later, Machell and Richards and Whistler and BeMiller isolated the compound as a sirup (in yields of about 1%) by treatment of maltose with 0.05 N sodium hydroxide and of cellobiose with 0.05 N potassium hydroxide. There was a divergence in the reported specific optical rotations (in water), namely, —24.1° and -fll°, respectively, which might be attributable to degradation of this labile compound during isolation or storage. The crystalline (2,4-dinitrophenyl)osazone prepared in both investigations was further characterized as its crystalline triacetate. ... 

Formation of Osazones.—Osazones are readily formed from 3-deoxy-o-erythro-hexosuloae in the presence or absence of acid. However, the only crystalline osazones that have been obtained are the (4-nitrophenyl)osa-zone, the (2,4-dinitrophenyl)osazone, and the (2,5-dichlorophenyl)-osazone. The first two are identical with the respective osazones prepared from 3-deoxy-D-n 5o-hexose. The last two derivatives yield crystalline triacetates.The high melting points of many of these derivatives are not satisfactory for characterization, but their high optical rotations are a useful criterion of purity. ... 

Aryl- and benzoyl-hydrazones of 2,4-0-ethyIidene-D-erythrose have been prepared and acetylated. D- /> cero-Tetrulose phenyl- and 4-substituted-phenyl-osazones (prepared from D-erythrose) gave l-aryl-3-formylpyrazoIe A-acetylarylhydrazones on boiling with acetic anhydride (Scheme 36). The... 

Phenylhydrazine is usually dissolved in acetic acid for hydrazone formation if a salt of phenylhydrazine with an inorganic acid is used, it must be mixed with an excess of sodium acetate (see preparation of osazones, p. 137). 

Osazone formation. The preparation of glucosazone has already been given (p. 137). It may be carried out on a small scale by either of the following methods, according as (a) the phenyl hydrazine base, or (Z>) one of its salts, is used. 

Osazone formation. Forms an osazone, m.p. 206 (see however footnote, p. 140) this osazone, unlike glucosazone, is soluble in hot water. See p. 139 for preparation. Examine the crystals under the microscope and note the sheaves of plates, not needles (Fig. 63(B),... 

Osazone formation. Forms a yellow osazone, m.p. 208° soluble in hot water. See p. 137 for preparation. If examined under the microscope very characteristic clusters of hedge-hog crystals will be seen (Fig. 63(c), p. 139). The difference in the crystalline appearance of lactosazonc and maltosazone should be very carefully noted, as this difference forms the chief and most reliable method of differentiating between these two sugars. 

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. 

L-Rhamnosone was prepared by the action of hydrochloric acid on L-rhamnose phenylosazone9 and was identified by reconversion to the osazone. This method was later employed186 as a stage in the synthesis of the ascorbic acid analog, L-rhamnoascorbic acid. The benzaldehyde decomposition of the osazone gave a low yield of osone93 and o-nitrobenzaldehyde was not a satisfactory aldehydic substitute. 

Morrell and Croft obtained L-rhamnosone by treating the free sugar with Fenton s reagent,38 and identified it by preparing the p-bromophenyl-osazone.114... 

Reichstein and Demole186 prepared L-fucosone from the osazone by the hydrochloric acid method in the synthesis of L-fucoascorbic acid. 

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... 

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