Carbohydrates aminosugars

Benzoyl chlorides, like other acyl chlorides, react readily with alcohols to form the corresponding esters (259). The reaction requires 19 h to be completed, and it has been studied in the analysis of carbohydrates, aminosugars, and glycosides (260). Because the preparation of acyl derivatives of monosaccharides is difficult, phenyldimethylsilyl chloride has been also investigated as an alternative label (261). After dissolving the analytes in dimethylformamide and addition of... 

The aminopolyol adducts obtained with carbohydrates can be manipulate further to produce aminosugars (Scheme 7.27) [26, 75]. For example, starting with D-arabinose 207 and a cleavable amine, such as 208 or 213, followed by conversion to a protected aminopolyol 211 and ozonolysis of the alkene forms the protected mannosamine 212 in good overall yield and purity. 

Naturally occurring polysaccharides can occur either as individual carbohydrate molecules or in combination with other naturally occurring substances, such as proteins (glycoproteins) and lipids (glycolipids). In all cases the polysaccharide section may have linear or branched chain structures, which often contain the derivatives of both monosaccharides and aminosugars (Figure 1.20). 

In this way various protected carbohydrates and aminosugars are obtained. There is a matching correspondence between a-branched (5) or (/ )-configurated aldehydes and (S) or (/ )-pro-Une, respectively. Thus, the reaction of 25 with the (R)-configurated 2,3-di-O-isopropylidene-D-glyceraldehyde gives the double acetonide of D-psicose in 76% yield. Acidic deprotection with Dowex gives the parent D-psicose. A similar route has been reported by Cordova and co-workers [144]. 

Carbohydrate-based polyamides and polyurethanes constitute two major families of polymers and hence the interest in preparing aminosugars and, from them, the corresponding isocyanates. This wide research field has produced very interesting materials including the first chiral nylon-type polyamides [16]. 

Reaction of glycosylamines or aminosugars 1 with diethyl (ethoxymethyl-ene)malonate to give the corresponding enamine derivatives 2 was found [32-34] to be quite an efficient procedure for protecting amino moieties in carbohydrates, stable in both acidic and basic conditions (Scheme 1). Deprotection is carried out in moist dichloromethane with chlorine or bromine, to give hydrochloride or hydrobromide 3, usually crystalline. 

Neurochemistry of Aminosugars. Neurochemistry and Neuropathology of the Complex Carbohydrates , ed. E. G. Brunngraber, C. C. Thomas, Springfield, 1979. 

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