Aldose oximes

Hydrogenation of aldose oximes (aldoses D-arabinose, D-mannose and D-galactose) at 50 °C over 5 % Pt/C catalyst, under 100 bar hydrogen, resulted in quantitative conversion of the oximes to a mixture of mono- and dialditylamines from which the latter were isolated in fairly good yield (26-80%) [44]. 

WOHL - WEYGAND Aldose degradation Degradation of sugar oximes via cyanohydrins by means of an acid chloride/pyridine (Wohl) or of... 

Conversion of the aldehyde into a nitrile is accomplished by treatment of an aldose with hydroxvlamine to give an oxime (Section 19.8), followed by dehydration of the oxJme with acetic anhydride. The Wohl degradation does not give particularly high yields of chain-shortened aldoses, but the reaction is general for all aldopentoses and aldohexoses. For example, D-galactose is converted by Wohl degradation into n-lyxose. 

The fact that an aldose reacts chemoselectively with amino derivatives such as hydroxylamines or hydrazones generating oximes or hydrazones,... 

Bovine aldose reductase Inhibited by ahphatic, cychc and aromatic oximes, using benzyl alcohol as substrate 123... 

Wohl prepared the acylated nitriles of the aldonic acids by heating the aldose oximes with a mixture of sodium acetate and acetic anhydride. With careful control of the reaction, this method may be used for preparative work with fairly good results. 

In the case of the oximes of the aldose sugars, the situation is more complicated because of the possibility of both open-chain and cyclic structures. That aldose oximes can react in the open-chain form follows from the formation of the nitriles and from the isolation of acylated open-chain aldose oximes as secondary products in preparation of nitriles. For example, Wolfrom and Thompson, by the action of sodium acetate-acetic anhydride on n-glucose oxime, not only obtained pentaacetyl-D-glucononitrile, in 40% yield, but also isolated a small amount of hexaacetyl-oWeAydo-D-glucose oxime (V) identical with that prepared by mild acetylation of pentaacetyl-aWe%do-D-glucose oxime (IV) whose structure was assured by its formation from pentaacetyl-aldehydo-D-glucoae (III). 

Acetylated aldose oximes with a ring structure have also been obtained during the preparation of the nitriles, both with sodium acetate-acetic anhydride and with pyridine-acetic anhydride. Thus it appears that under these conditions at least a certain amount of the oxime is present in the ring form. 

An Nitrone lassen sich Alkene 1,3-dipolar addieren. Dies nutzt eine asymmetrische Syn-these von L-5-Oxa-prolin aus. Das Nitron aus 2,3 5,6-Di-0-isopropyliden-mannose-oxim mit Glyoxylsaure-tert.-butylester in situ) cyclisiert mit Ethen, wobei das (JS)-Dihstereo-mer spontan kristallisiert (3R)- bzw. (3S)-3-tert.-Butyloxycarbonyl-2-(2,3 5,6-di-0-iso-propyliden-ct-D-mannofuranosyl) l,2-oxazolidin[9i%, 54% de (S43%].Nachder Abspaltung des Aldose-Restes erhalt man (S)-5-Oxa-prolin-tert.-butylester (3-tert.-Butyl-oxycarbonyl-1,2-oxazolidin 90% Schmp. 52-530)4 ... 

Problem 22.10 Outline the steps in the Wohl degradation, which employs a dehydration of an aldose oxime and is thus a reversal of the Kiliani-Fischer step-up method. 

Shen C, Sigman DS. New inhibitors of aldose reductase anti-oximes of aromatic aldehydes. Arch Biochem Biophys 1991 286 596-603. 

H. Kiliani, as Fischer always emphatically acknowledged, discovered and developed the method of building up the aldose series by the cyanohydrin reaction to give nitriles from the nitrile, the next higher aldonic acid could then be prepared. In 1890, A. Wohl, working in Fischer s Berlin laboratory, elaborated the dehydration of an aldose oxime to the nitrile, from which the next lower aldose could be prepared by loss of hydrocyanic acid. Fischer exploited the possibilities of sugar extension and degradation afforded by the use of these two important methods. 

Reacts with aldoses to yield oximes as the first step in the Wohl degradation of aldoses (Section 25.6). 

The well-known Ruff degradation of aldonic acids to aldoses with one less carbon was first applied with bromine as the oxidant. Calcium D-gluconate was treated with an excess of bromine at 20° for ten hours the acidity of the solution was kept low with lead carbonate. The filtrate was processed and D-arabinose was obtained in small yield as the oxime. However, Ruff found that the effect of hydrogen peroxide was much better and abandoned the use of bromine. Fenton noted the same effect in the oxidation of tartaric acid to dihydroxymaleic acid the action of oxygen was more effective than that of the halogens. It was assumed that a keto aldonic acid was the intermediate in the degradation of the aldonic acid to the new aldose, and the apparent stability of the keto acids to further oxidation by bromine may be the reason for the low yields with this oxidant. 

Degradation of aldoses. It has been used in a Wohl-type degradation in which an aldose oxime is treated with 2,4-dinitrofiuorobenzene to form the oxime aryl ether, which decomposes to the next lower aldose, 2,4-dinitrophenoI, and hydrogen cyanide. ... 

Hydrolysis of a Schiff base to carbonyl compound and amine occurs analogously to that of oximes and hydrazones. It is dependent on the basicity of the amine and the reactivity of the aldehyde into which the azomethine is cleaved. Hydrolysis can be achieved in relatively mild conditions, e.g., by short warming in dilute mineral acid, occasionally in dilute alcohol or acetic acid. The condensation products of amines and aldoses are decomposed by even traces of acid Schiff bases are generally resistant to alkali. As in oximes and hydrazones, the aldehyde residue of Schiff bases can be replaced by another aldehyde residue there is a preference for formaldehyde in this case.620... 

The similar polarographic behavior of semicarbazones, hydrazones, phenylhydrazones, and oximes of D-glucose, D-galactose, and n-mannose was described in another paper. For the aldoses studied, the equilibrium and rate constants for the formation of their oximes, semicarbazones, and hydrazones were determined at several different pH values, and it was found that their reactivity increases in the order D-glucose < D-galactose < D-mannose < D-xylose < n-arabinose < D-ribose < D-lyxose. ... 

The O-methyloximes of several aldoses have been examined in solution by C-n.m.r. and by g.l.c. and the authors conclude that the 0-methyl oximes exist as acyclic modifications. Those derived from simple aldoses existed as the anfi-isomer, whereas those derived from 2-deoxyaldoses existed as anti- and jyn-mixtures.The oxime of D-glucose, however, exists as a mixture of the syn- and anft-forms and the two pyranose forms. All four isomers have been separated by t.l.c. and identified spectroscopically. ... 

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