Aldonic acids 2-amino-2-deoxy

The bromodeoxyaldonolactones have been used for the preparation of aminodeoxy aldonic acids and aminodeoxy sugars via azido derivatives (45,46). Likewise, a- and /J-aminopolyhydroxy acids have been prepared by treatment of the bromodeoxyaldonolactones with liquid ammonia (47). Thus, 3-amino-3-deoxy-D-threonic acid and 3-amino-3-deoxy-D-arabin-onic acid (40b) were obtained from 2-bromo-2-deoxy-L-threono- or D-xy-lono-1,4-lactone (38). It was shown that 2,3-epoxy carboxamides (namely, 39) are intermediates of the reaction. Heating at 90° for long periods led to the 3-amino-3-deoxyaldonamides, which upon acid hydrolysis yielded the corresponding aldonic acids. 

Aldonic acids, characterization of, 373 —, 2-amino-2-deoxy-, deamination of, 191 —, 2,5-anhydro-, properties of, 220-229 Aldonolactones, 2-amino-2-deoxy-, deamination of, 189... 

This section deals with acids, that are formally modified aldonic acids, such as keto, deoxy, and branched-chain acids (including the so-called saccharinic acids). The aminoaldonic acids, which are oxidation products of amino sugars, and, in particular, the important nonulosaminic acids (neuraminic acids) and muramic acid, are not discussed here. The formation of saccharinic acids by the treatment of sugars with alkali, and the mechanisms involved, are likewise outside the scope of this chapter. 

Mode of synthesis A. cyanohydrin, by way of 2-nmino-2-deoxy-aldonic acid B. scission of sugar derivative epoxide with ammonia C. interconversion of hexosamine series D. hemihydrogenation of a-amino nitrile466 E. rearrangement of ketosyl-amine F. Removal of last carbon atom of hexosamine G. Hydrazinolysis (with inversion) of 2-0-tosyl-pentose. 6 Physical constants taken from this reference. c Derivatives (only) isolated. 

The chemical shifts observed in the 13C-n.m.r. spectra of amino-deoxy sugars are strongly dependent on the pH of the sample solution, and the spectra of such compounds should, therefore, be measured with control of the pH. Comparison of, 3C-n.m.r. spectra, measured at low or high pH, that is, for compounds having protonated or free amino groups, may be used for the assignment of carbons a and /3 to the amino groups.11,16,81 82 Similar, but smaller, effects are.observed in the spectra of other ionizable compounds, such as aldonic or uronic acids.60,83... 

The first question concerns the nature and relative proportions of constituent monosaccharides. In principle, this is obtained by acidic hydrolysis (Biermann 1988) but, in practice, it must be carefully applied as there are a certain number of important specific cases. Hydrochloric, sulfuric, and trifluoroacetic acids are used whose 1 N solutions have a pH of 0.1, 0.3, and 0.7, respectively. When hydrolysis liberates monosaccharides fragile in an acidic medium, a delicate balance between the risk of incomplete hydrolysis and partial destruction of the hydrolysis product must be maintained. The fragile sugars are pentoses, deoxy sugars, and uronic and aldonic acids. When sialic acid is kept for 30 min at 90°C in 0.01 M HCl, 20% decomposition occurs. With neutral polysaccharides, decomposition can be limited to less than 9%. The acetyl groups of acetamides are hydrolysed and relatively stable protonated amino sugars are obtained. 

Further examples have been reported of the synthesis of aldonic acids by carbon-carbon bond-forming reactions. 2,3 4,5-Di-0-isopropylidene-D-arabinose (3) with methyl acetoacetate gave the Knoevenagel product (4), which is a branched-chain, unsaturated heptonic acid derivative. This rearranged on treatment with trifluoroacetic acid to afford the spiro-product (5) (Scheme 1). This same compound was obtainable from the 2,5-anhydroaldose derivative (6) by similar treatment. The synthesis of destomic acid, 6-amino-6-deoxy-L- /ycew-... 

Sugars Unusual sugars (amino, deoxy and methyl sugars, and sugars with branched chains). Reduction products (sugar alcohols, cyclitols, streptidine). Oxidation products (uronic acids, aldonic acids, sugar dicarboxylic acids). 

By Chain extension. — Addition of the glycine anion equivalent 3 to aldehydo-sugar derivatives such as L-arabmo-2, led to various 2-amino-2-deoxy-aldonic acids, such as 2-amino-2-deoxy-D-g/ycero-L-ga/flcto-heptonic acid 4 which was obtained in 35% overall yield (Scheme 1). ... 

Similar reaction sequences have been observed with 2-amino-2-deoxy-D-mannose (epichitosamine) and 2-amino-2-deoxy-D-galactose (chondrosa-mine) and their derived aminodeoxy aldonic acids. 

---