Aldoses 6- amino-6-deoxy

The cyclic acetals have been of great assistance in the preparation of, for example, methylated sugars, - deoxy sugars, and amino-deoxy sugars. The specific syntheses of many di- and tri-saccharides have been described - in these, a suitable acetal of the aldose is caused to react with a poly-O-acetylglycosyl halide or a bromo- or chloro-hydrin derivative. 

Aldoses containing acetamido-, amino-, deoxy-, and thio-groups have been examined by g.l.c. of their peracetylated aldononitrile derivatives. Chemical... 

The generic term monosaccharide (as opposed to oligosaccharide or polysaccharide) denotes a single unit, without glycosidic connection to other such units. It includes aldoses, dialdoses, aldoketoses, ketoses and diketoses, as well as deoxy sugars and amino sugars, and their derivatives, provided that the parent compound has a (potential) carbonyl gTOup. 

The results of inhibition studies with aldonolactones and 5-amino-5-deoxyaldonolactams may be summarized as follows y -D-glycosidases are inhibited by 1,5-lactones and the lactams some 100- to > 10,000-fold better than by the parent aldoses, with Kj values from 200 //Mto <0.1 nM. Al-dono-1,4-lactones are probably no better inhibitors than aldoses or polyols of comparable structure, with the possible exception s of 2-acetamido-2-deoxy-D-glucono-1,4-lactone. 

Amino-2-deoxy aldoses. The behaviour of O-unprotected sugars is exemplified in D-gluco series after basic hydrolysis of the starting 2-benzamidoglycoside followed by buffering the medium with carbon dioxide and treatment with thiophosgene, an intermediate isothiocyanate was obtained.320 However, NMR revealed a temperature-dependent equilibrium of this isothiocyanate with a trans-fused OZT (Scheme 5). 

Amino-5-deoxy aldoses. Similarly to the precedent approach, a regio-selective access to C-5 anchored OZTs was developed from 5-amino-5-deoxy-1,2-<9-isopropylidene-a-D-gluco- and a-L-idofuranose through condensation with carbon disulfide (Scheme 13) 22,23... 

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. ... 

The Knovenagel condensation under basic conditions was first investigated with D-glucosamine chlorhydrate (28.HC1) as the sugar. The condensation of this reducing amino sugar with pentane-2,4-dione 1 in aqueous acetone in the presence of sodium carbonate afforded the pyrrole derivative 29 in 85% yield [99] (Scheme 5). The reaction was extended to other 2-amino-2-deoxy-aldose and carbon nucleophiles [100-104]. 

An account of the methods of synthesis of amino sugars has been given in an earlier Volume of this Series1 attention is devoted in this Section to methods recently developed. Several general methods have been employed for the synthesis of 2-amino-2-deoxy-aldoses these respectively involve direct amination of suitable sugar derivatives, interconversion of sugar series, and ascent or descent of a series with or without concomitant amination or molecular rearrangements. 

An N-alkyl group is not removed under the reaction conditions, and an iV-substituted 2-amino-2-deoxy-aldose is formed. Under the same reaction conditions, anA-benzyl group is cleaved (with the uptake of a further mole of hydrogen per mole), to give the free 2-amino-2-deoxy-aldose and toluene ... 

Amino-1-deoxy-2-ketose or 1-Amino-2-deoxy-2-aldoses -3H2O... 

Monosaccharides may possess functionalities other than hydroxyls. Amino sugars are aldoses or ketoses which have a hydroxyl group replaced by an amino functionality. 2-Amino-2-deoxy-glucose is one of the most abundant amino sugars it is a constituent of the polysaccharide chitin. It also appears in mammalian glycoproteins, linking the sugar chain to the protein. Monosaccharides may also be substituted with sulfates and phosphates. Furthermore, deoxy functions can often be present, and important examples of this class of monosaccharides are L-fucose and L-rhamnose. 

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