Hexulosonic acids

The features common to 2-deoxy ribose 5-phosphate and the two 3-deoxy hexulosonic acid 6-phosphates are that they all have a deoxy group next to the carbonyl group and that they can form only the furanoid ring (35, 78a, 80a) as long as the phosphate group is attached to the terminal, primary alcohol. However, they can all assume the pyranoid ring... 

Figure 1. Separation of isomeric S-deoxy D-erythro-hexulosonic acid phosphates.

DAG (-)-2,3 4,6-di-0-isopropylidene-2-keto-L-gulonic acid hydrate [L-a /Zo-2-hexulosonic acid, bis-O-(l-methylethylidine)-]... 

Figure 10.12 Stereoselective synthesis ofthe amino acid portion of nikkomycin antibiotics and hexulosonic acids using KDPGIc aldolase.

Several glyculosonic acids have been identified as components of bacterial polysaccharides. D-/yxo-Hexulosonic acid, as Q -D-pyranosyl residues (23), is a component of the extracellular polysaccharide from a Rhodococcus species. The LPS from Acinetobacter calcoaceticus NCTC 10305 contains - D-g/ycero-D-/a/o-octulosonic acid (24). It is isosteric with 3-deoxy-D-mnnno-octulosonic acid (25), which is a constituent of bacterial LPS and links the polysaccharide part to the lipid A region. It seems possible that D-g/ycero-D-tfl/o-octulosonic acid replaces 3-deoxy-D-/wan o-octulosonic acid in the A. calcoaceticus LPS. 

Synthesis of New Methyl Esters of 3-Deoxy-D- ry /rro-2-hexulosonic acid (KDG) analogs, inducers of the Expression of Pectinase Genes in Bacteria Erwinia chrysanthemi... 

The most important oxidation product of L-gulono-1,4-lactone (I) is, without a doubt, L-ascorbic acid (6 vitamin C), and the most important oxidation product of L-gulonic acid (3) is L-xyZo-2-hexulosonic acid (5), which serves as a key intermediate in the commercial production of L-ascorbic acid. The literature covering the methods by which 1 or 3 (or derivatives thereof) has been converted into 6 or 5, as well as other methods for the preparation of 6, has been reviewed,1 and will not be discussed here. 

Investigations of the mechanism of decarboxylation of hexuronic acids have largely involved kinetic and tracer studies. When either D-xylo-5-hexulosonic acid or D-glucuronic acid is converted into 27 in acidified, tritiated water, the resulting 27 contains 18% and 15%, respectively, of the activity of the solvent as carbon-bound tritium.21 Further degradation studies showed that the isotope is situated on the furan ring at either position 3 or 4, or both these atoms correspond to C-3 or C-4 of the starting uronic acid. 

Kurata and Sakurai124 have investigated the mechanism of dehydration of L-ascorbic acid by examining the products from it and from L-xyZo-hexulosonic acid after treatment for 1 hour at 100° at pH 2.2, or with 5% sulfuric acid at 100°. In both experiments, 2-furaldehyde and 3-deoxy-L-threo-pentosulose (isolated as the phenylhydrazone) were the major products no pentose was detected. 

The formation of 76a is essential, as the enol 76 would not be expected to be decarboxylated. When allowed to react in tritiated water, both L-ascorbic acid and D-amfomo-hexulosonic acid produced 2-furaldehyde having an activity approximately 60% of that of the solvent most of the activity was situated at the a-carbon atom. The failure to detect any pentose is probably ascribable to the high reactivity of the 1,2-enediol (77). 

Oxidation of D-glucose at C-l and C-5 gives D-xyZo-5-hexulosonic acid, which is an effective chelating agent for calcium. The structure of calcium (D-xy/o-5-hexulosonate)2 dihydrate (8) was reported by... 

The composition of aqueous solutions of all of the 2-hexuloses, of several 3-hexuloses, 2-pentuloses, and their deoxy derivatives, and some of the hexulosonic acids is shown in Table IV. 

Deoxy-L-g/ycero-pentulosonic acid was found to be present in Klebsiella K38 polysaccharide249 and 3-deoxy-D-threo-hexulosonic acid was identified as a component of Azotobacter capsular polysaccharide.2S0 O-Specific polysaccharides of Pseudomonas aeruginosa and Shigella boydii were shown2SI... 

Synthesis by Way of D-xyZo-5-Hexulosonic Acid ( 5-Keto-D-gluconic... 

A summary of the methods by which 29 has been converted into 1 by base-catalyzed cyclization is shown in Table I. The most attractive, base-catalyzed, cyclization procedure appears to be that using the salt of a weak acid, such as sodium hydrogencarbonate, sodium acetate, or related basic salts. L-xy/o-2-Hexulosonic acid (28) has been re-... 

Summaries of the methods by which 2,3 4,6-di-0-isopropylidene-L-xf/Zo-2-hexulofuranosonic acid (27), L-xyZo-2-hexulosonic acid (28),... 

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