Acetamido-sugars

Amide derivatives have proved especially useful sugars for study by c.d. spectroscopy. The amide substituent is the same as the chromophore found in proteins, so that its optical properties have been extensively studied both experimentally and theoretically. 2-Acetamido sugars are found in many glycoproteins. The structure of 2-acetamido-2-deoxy-a-D-glucopyranose is given as an example in formula 7. 

Diethyl dithioacetals have been used for determining the position of the acetamido group in acetamido sugars by the mass-spectral method.40... 

Along with permethylated derivatives, the permethylated, LiAlH4-reduced derivatives of glycolipids are also used for mass-spectrometric analysis. The amide groups of acetamido sugars and the ceramide part are reduced to alkylamino groups, and, in the case of gangliosides, the ester... 

Morgan-Elson Test.—The color intensity produced by the 2-acetamido sugars in the Morgan-Elson test is significantly affected by substitution... 

Attempts to obtain 4-acetamido sugars from derivatives of 6-deoxy-D- or L-mannose led to the discovery of an interesting rearrangement that is suitable for the preparation of 5-acetamido-5,6-dideoxy-D- or... 

Hang HC, Bertozzi CR. Ketone isoteres of 2-V-acetamido-sugars as substrates for metabolic cell surface engineering. J. Am. Chem. Soc. 2001 123 1242-1243. 

H( C)-HMQC]. The chemical shift of C-2, 50.91 ppm, identified residue A as the acetamido sugar, a-GalNAcp. 

A. Metabolic Studies with Modified Amino Sugars and A/-Acetamido Sugars... 

The traditional method of assay of 2-acetamido sugars is the Morgan-Elson reaction. This involves treatment of the sugars in base, which produces furans, and reaction of these furans in situ with Ehrlich s reagent (p-dimethylamino-benzaldehyde in acid), which generates delocalised chromophores, as shown in Figure 7.8." ... 

The Morgan-Elson reaction for the determination of 2-acetamido sugars can be used for obtaining an indication of the position of the glycosidic links in 2-acetamido-2-deoxy-D-glucose oligosaccharides. It has been used in this way to show the presence of (1 6) links and (1— 4) links Hyalobiouronic acid was ultimately converted to a neutral... 

The Tables list oligosaccharide polymers of simple monosaccharides and of the following naturally occurring derivatives amino sugars, 2-acetamido sugars, uronic acids, and mono-O-methyluronic acids. Although it was considered desirable to include only compounds whose structures had been established beyond doubt, such a rule would have excluded many important compounds. Exceptions to this rule were, therefore, made for compounds of incompletely established structure, provided that there was sufficient evidence to show that they were unlikely to be compounds already known. 

The hydrochloride of the weakly basic acetamido sugar was precipitated from ether solution. This difficulty was later overcome by using the JV,A-phthaloyl blocking group. ... 

Aldol reactions of this type, involving 2-acetamido-2-deoxyaldohexoses, have been studied in connection with the chemical synthesis of A -acetyl-neuraminic acid (50) and related substances, and, for this reason, the choice of the dicarbonyl compound has thus far been limited to oxalacetic acid and its esters. Oxalacetic acid condenses readily with 2-acetamido-2-deoxyaldohexoses in aqueous solution at pH 11. Under these conditions, acetamido sugars partially epimerize, and the aldol reaction takes place for both of the 2-acetamido-2-deoxyaldohexoses present. The complexity of the reaction is further increased by the formation of asymmetric centers at carbon atoms 3 and 4 of the condensation products, namely, diacids (45) and (48), and this can result in the formation of four diastereo-isomers from each sugar. The reaction using 2-acetamido-2-deoxy-o-rnannose (47) has been the one most extensively studied. In this... 

The study of the reactions of amino sugars with /3-keto thiolesters was undertaken in order to obtain data on the way in which simple models of (S-acetoacetyl-Coenzyme A may react. There is no difference between the modes of reaction of ethyl thiolacetoacetate and ethyl acetoacetate with 2-amino-2-deoxy-D-glucose. In the reaction with l-amino-l-deoxy-o-fructose, the product (18) of the thiolester liberates ethanethiol very readily and forms the lactone (27). amino sugar interact, giving lactone (27). No compound similar to the pyrrole thiolester (18) was found. In this context, the investigation of similar reactions with acetamido sugars will be of interest. 

Similar stereoisomerizations at C2 are successful with 2-acetamido sugars and aldonic acids. In the case of fructose or other ketoses, the chiral center at C3 can be isomerized effectively (Scheme 4.3.4). 

The assignments of the first transition to a n— it and the second to a n—IT transition aje well established for the acetamido sugars. The appearance of n— n amide in the lower wavelength region (-210 nm) for these sugars as compared to that in a helical polypeptides ( 222 nm) is believed to be due to extensive solvation of amido groups in saccharides (9). 

II. Circular Dichroism Spectra of Oligosaccharides Containing Acetamido Sugars... 

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