Of glycosylamines

The following protocol for synthesis of glycosylamines from reducing sugars is based on the method of Likhosherstov et al. (1986). 

Bajugam and Flitsch [217] have described the synthesis of glycosylamines from mono-, di-, and trisaccharides by direct microwave-assisted Kochetkov amination (Scheme 6.110). The reaction was found to be effective with just a fivefold excess (w/w) of ammonium carbonate with respect to the sugar, as compared to the 40-or 50-fold excess needed under thermal conditions. All transformations were completed within 90 min in dimethyl sulfoxide as solvent, maintaining the vessel temperature at an apparent 40 °C using the heating-while-cooling technique (see Section 2.5.3). 

The initiating reaction between aldoses and amines, or amino acids, appears to involve a reversible formation of an N-substituted aldosyl-amine (75) see Scheme 14. Without an acidic catalyst, hexoses form the aldosylamine condensation-product in 80-90% yield. An acidic catalyst raises the reaction rate and yet, too much acid rapidly promotes the formation of 1-amino-l-deoxy-2-ketoses. Amino acids act in an autocat-alytic manner, and the condensation proceeds even in the absence of additional acid. A considerable number of glycosylamines have been prepared by heating the saccharides and an amine in anhydrous ethanol in the presence of an acidic catalyst. N.m.r. spectroscopy has been used to show that primary amines condense with D-ribose to give D-ribopyrano-sylamines. ... 

There are two theories as to the mechanism of the formation of imidazole and pyrazine compounds, namely, (a) the prior formation of glycosylamines and aminodeoxy sugars, and (b) the fragmentation mechanism. 

Figure 2.29 Formation of glycosylamine, the initial step in Maillard browning.

The subject of glycosylamines has already been reviewed in this Series,80 and the nomenclature of these compounds, formerly called JV-glycosides, amides, anilides, etc., was discussed. 

Results of the many investigations into the mechanism of the Maillard reaction support one of two main theories. The first assumes the formation of glycosylamines which undergo the Amadori (or, for ketoses, the Heyns) rearrangement. The 1-amino-1-deoxyketose derivative (or 2-amino-2-de-... 

Linderman and his group applied so-called convertible isonitriles [47] for this type of glycosylamine-based Ugi reaction. The Osilylprotected isonitrile 32 was reacted with tri-O-pivaloylarabinosyl imines or tetra-O-pivaloylgalactosyl imines (Scheme 22). The diastereoselectivity ranked in the same range as that given in Table 4.3. 

The formation of glycosylamines from the reaction of amino groups and sugars is... 

Figure 3-8 Reversible Formation of Glycosylamines in the Browning Reaction. Source From D.T. Hurst, Recent Development in the Study of Nonenzymic Browning and Its Inhibition by Sulpher Dioxide, BFMIRA Scientific and Technical Surveys, No. 75, Leatherhead, England, 1972.

The literature on /3-D-glucosiduronic acids is particularly voluminous, and the subject has been extensively reviewed from several aspects. Section III, dealing with this class of compounds, is devoted more to a general overview of their preparation, characterization, and reactions than to individual members. On the other hand, the categories of 1-esters of glycuronic acids and of (glycosylamine)uronic acids, which appear not to have been treated previously as separate topics, receive relatively more attention. 

Indirect methods have also been used. One, introduced by Sabalitschka, consists of heating the amine with an 0-acetylglycosyl halide and subsequently deacetylating the product. Other indirect methods for preparing acetates of glycosylamines are outlined on p. 112. 

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