Glycosylamines structure

Ellis and Honeyman80 have raised strong doubts as to the validity of the structural determinations that have been applied to glycosylamines these doubts are based on the fact that such compounds are readily isomerized, as evidenced by their mutarotation. The formation of a trityl ether cannot be considered valid evidence for the presence of a primary hydroxyl group in the compound tritylated, and periodate oxidation, which is often excessive, may lead to faulty conclusions. 

Although much work has been done in an attempt to elucidate the structure of iV-substituted glycosylamines, rigid proof of their structures has not yet been achieved.43 Spectroscopic evidence is inconclusive,69 whilst chemical methods are of limited value because equilibrium between open-chain, pyranose, and furanose forms is possible. However, all such derivatives as ethers and esters so far prepared directly from A-glycosylamines have been shown to be pyranoid, and periodate oxidation of some N-glycosylamines has confirmed this conclusion.70 71... 

In the case of aliphatic and aromatic amines as the starting material, where the carboxyl group is absent, the isolation of the corresponding glycosylamines has been reported (3). Structure analyses revealed the compound to be a /3-pyranoid having a C -(D) conformation. 

In the Maillard sequence, the initial reaction between a carbonyl group and a trivalent nitrogen atom is perhaps the most thoroughly investigated and best understood. As early as 1963, Reynolds (14) published a review with 140 references limited largely to the studies of reactions of aldoses with amines, the determination of the structures and properties of the first products of reaction (a glycosylamine), and the rearrangement of the latter to a more stable ketoseamine. 

One important use of glycosylamines, for the characterization of methyl ethers of sugars obtained during structural studies on polysaccharides, has already been mentioned (see p. 110). 

Voto6ek and Wichterle " investigated the reaction of JV-substituted gly-cosylamines with hydrocyanic acid, but they did not start with the isolated glycosylamine. The sugar and amine were heated in alcohol, the hydrocyanic acid was added, and the mixture was allowed to cool. The structure of the crystalline nitrile isolated was not determined. Because the hydrogen cyanide could have added to the carbonyl group of the ketose after an Amadori rearrangement had occurred, the constitution of their products is open to question. 

On the basis of these results, Hakomori and coworkers53,54 proposed a l-deoxy-l-(N-peptidyl)-D-ketose structure for the linkage of the peptide and carbohydrate components of UGP I, II, and III this kind of structure is identical with that of the product of the Amadori rearrangement of glycosylamines. 

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