3- deoxy-3-acetamido sugars

In contrast to the non-reaction of 4-O-substituted 2-acetamido-2-deoxy sugars, 3-O-substituted derivatives react far more readily (to give Chromo-... 

In contrast, the Barbier reactions of 2-acetamido-2-deoxy sugars with ketones showed a preference for the formation of 1,2-m-C-glycoside products (Scheme 7.39). This was attributed to the complexation of the C2-acetamido group to the glycosyl samarium, thereby reducing the configurational lability of the organometallic species.78,80,81... 

This Sml2-induced C-glycosylation was extended to the s)mthesis of C-linked glycosides of 2-acetamido-2-deoxy sugars [88,89,90]. Reductive samariation of the 2-pyridyl sulfone of A-acetylglucosamine 184 in the presence of aldehyde 167 leads selectively to the a-C-gly-cosyl dimer 185 [90] (O Scheme 38). 

Trimethylsilylated disaccharides containing a 2-acetamido-2-deoxy-hexose residue generally give a detectable molecular-ion. The nature of the monomers can be determined by inspection of the A-series of fragments. A 2-acetamido-2-deoxy sugar at the reducing position could be determined by the abji-fragment at m/e 538 (48). 

A new method for iV-deacetylation of 2-acetamido-2-deoxy-sugars has appeared. A mixture of trifluoroacetic anhydride-trifluoroacetic acid was used to transacylate the A-acetylamido compound and trifluoroacetylate all free hydroxy-groups treatment with either methanolic ammonia or ethanolic sodium borohydride removed all the trifluoroacetyl groups. When applied to capsular polysaccharides of Diplococcus pneumoniae minimal degradation was observed. ... 

The selectivity of conventional pivaloylation (pivaloyl chloride - pyridine) of 2-acetamido-2-deoxy sugars has been studied. The order of reactivity of the hydroxyl groups for 2-acetamido-2-deoxy-D-glucose and its methyl pyranosides was HO-6 > HO-3 (>HO-l) > HO-4, rendering, for example, anomeric dipivaloates (8) available in 69% yield. From the methyl a-glycoside of H acetylmuramate only the primary monopivaloate (9) could be... 

The determination of the presence of carbohydrate in a sample is obtained by performing the Mohsch test [1] (see section 3.4 in Chapter 3 for the chemistry involved in the Molisch test). The test is sensitive down to 10 p,g/mL and is relatively broad but specific for all types of carbohydrates, with the exception of sugar alcohols, 2-deoxy sugars, and 2-amino-2-deoxy sugars or 2-acetamido-2-deoxy sugars. 

Deoxy sugars 2-deoxy-araWno-hexose, 6-deoxyglucose and 2-deoxy-eo thro-pentose, fucose and rhamnose, 2-acetamido-2-deoxyhexoses ... 

Aryl glycosides of 2-amino-2-deoxy sugars, as might be expected, can be prepared by similar techniques as was illustrated by the synthesis of phenyl 3,4,6-tri-0-acetyl-2-acetamido-2-deoxy-p-D-glucoside and -D-galactoside by toluene -sulphonic acid catalysed reactions between phenol and the hexosamine penta-acetates These products were then anomerised using zinc chloride as catalyst to provide means of obtaining -anomers. 

Let us now go back to polysaccharide 9.16. The H NMR spectrum at 500 MHz shows seven signals, labelled A to F, which are characteristic of anomeric protons. There are also seven resonances typical of anomeric carbon in the C NMR spectrum. Other noteworthy signals are those of two methyl groups which can be ascribed to 6-deoxy sugars and two methyl groups corresponding to acetamido functions. 

All carbohydrates except sugar alcohols, 2-amino and 2-acetamido, and 2-deoxy sugars. A11 pentoses except 2-deoxypentoses, which are dehydrated very slowly. 

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