The mutarotation, hydrolysis, and rearrangement reactions of D-glucosylamine, D-mannosylamine, and D-xylosylamine have been studied, and rationalized on the basis of the formation of an intermediate, acyclic imonium ion. Rate constants are given for the hydrolysis reaction under various conditions. The formation of diglycosylamines is explained as a type of transamination in which a second molecule of the glycosylamine reacts with the first (in the imonium ion form) with the subsequent elimination of ammonia. Unsubstituted D-glucosylamine has been found to undergo an Amadori rearrangement in glacial acetic acid or in some of the methylenic compounds found by Hodge and Rist to be effective in the rearrangement of N-substituted glyeosylamines. Intramolecular mechanisms are suggested to account for the effectiveness of carboxylic
The tendency of the acetyl groups in the sugar acetates and glycosyl halides to form intramolecular condensation products depends upon the stereomeric arrangement of the groups within the molecule. In this paper the stereomeric factors which control the formation of orthoesters are discussed in light of the oppositeface concept for the Walden inversion, and it is shown that cyclic orthoacetates are formed when an acetyl group can approach the face of a neighboring carbon opposite a replaceable halogen atom. This concept was tested by application of the Koenigs-Knorr reaction to pentaacetyl-a-d-a-guloheptopyranosyl bromide and to heptaacetyl-a-neolactosyl chloride. Both of these compounds gave, as anticipated, the corresponding methyl orthoacetates.
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