Aldonic acids 2-deoxy

The 2-keto-3-deoxy-aldonic acid (phosphate) aldolases from Pseudomonas strains - 3-deoxy-2-keto-L-arabonate (F.C 4.1.2.18), 3-deoxy-2-keto-D-xylonate (EC 4.1.2.28), 3-deoxy-2-keto-6-phospho-D-gluconate (EC 4.1.2.14) and 3-deoxy-2-keto-6-phospho-D-galactonate aldolase (EC 4.1.2.21) - appear to be specific even for the acceptor components, but allow stereoselective syntheses of the respective natural substrates29. 

Pyruvate-dependent lyases serve catabolic functions in vivo in the degradation of sialic acids and KDO (2-keto-3-deoxy-manno-octosonate), and in that of 2-keto-3-deoxy aldonic acid intermediates from hexose or pentose catabolism. 

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. 

Some examples of transformations involving carbonyl ylides are listed in Table 4.20. Entry 1 illustrates the conversion of P-acyloxy-a-diazoesters into a-acyloxyacrylates by ring fission of a cyclic carbonyl ylide [978]. This reaction has been used for the synthesis of the natural aldonic acid KDO (3-deoxy-Z)-manno-2-octulosonic acid), which is an essential component of the cell wall lipopolysaccharide of gram-negative bacteria (Figure 4.15). 

Acetamido-2-deoxy-D-glucose (27) is oxidized by Cr(VI) to the aldonic acid, and the reaction is proposed to occur by a reaction path involving Cr(V). However, Cr(V) intermediates could not be detected by EPR in the 0.15-1.0 M [H+] range used in the kinetic measurements.86... 

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... 

An aldonic acid dehydratase was partially purified,290 and found to convert D-fuconate into 3-deoxy-D-t/ reo-2-hexulosonate, and L-arabin-onate into the corresponding 3-deoxy-L-gZi/cero-2-pentulosonate. It did not act on L-fuconate or on D-galactonate. 

Brigl and coworkers9 discovered the first example showing that the formation of aldose amides is not restricted to the degradation of acylated nitriles of aldonic acids. By ammonolysis of 2,3,4,5,6-penta-O-benzoyl-aldehydo-n-glucose (16), they obtained l,l-bis(benz-amido)-l-deoxy-D-glucitol (17). 

The Ruff degradation,67 involving interaction of a salt of an aldonic acid, ferric acetate, and hydrogen peroxide, was employed in the synthesis of 5-deoxy-L-arabinose218 and 5-deoxy-L-Iyxose.219... 

In vivo, pyruvate lyases perform a catabolic function. The synthetically most interesting types are those involved in the degradation of sialic acids or the structurally related octulosonic acid KDO, which are higher sugars typically found in mammalian or bacterial glycoconjugates [62-64], respectively. Also, hexose or pentose catabolism may proceed via pyruvate cleavage from intermediate 2-keto-3-deoxy derivatives which result from dehydration of the corresponding aldonic acids. Since these aldol additions are freely reversible, the often unfavourable equilibrium constants require that reactions in the direction of synthesis have to be driven by an excess of one of the components, preferably pyruvate for economic reasons, in order to achieve a satisfactory conversion. 

Comparable to the situation for the sialic acid and KDO lyases (vide supra), sets of stereochemically complementary pyruvate lyases are known, e,g. in Pseudomonas strains, which act on related 2-keto-3-deoxy-aldonic acids [112]. The enzymes cleaving six-carbon sugar acid phosphates—the KdgA and 2-keto-3-deoxy-6-phospho-D-galactonate (20) aldolases (KDPGal aldolase EC 4.1.2.21) [139] — are typified as class I enzymes, whereas those acting on non-phosphorylated five-carbon substrates — 2-keto-3-deoxy-L-arabonate (21) (KDAra aldolase EC 4.1.2,18) [140, 141] and 2-keto-3-deoxy-D-xylonate (22)... 

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. 

There are three known metabolic pathways to 3-deoxyulosonic acids. In the first, aldonic acids, formed by oxidation of aldopyranoses to the corresponding lactones, are dehydrated to the ulosonic acids (see Fig. 6). Thus, D-arabinose is converted by way of D-arabinonic acid to 3-deoxy-o-ffZj/cero-pentulosonic acid. The latter is then subjected to oxidative cleavage, yielding pyruvic and glycolic acids. L-Arabinose is oxidized and dehydrated to the 3-deoxy-L-g Z2/cero-pentulosonic acid, which is further oxidized to... 

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. 

On oxidation (with hypoiodite) to the corresponding aldonic acid, of the disaccharide obtained by partial hydrolysis of chitin, and acetylation with sodium acetate in acetic anhydride, the product undergoes /3-elimination, to give the bionic acid derivative 2-acetamido-4-0-(2-acetamido-tri-0-acetyl-2-deoxy- -D-glucopyranosyl)-6-0-acetyl-2,3-dideoxy-D-erj/(firo-hex-2-enono-1,5-lactone (90). In the original work, the determination of the site... 

Aldol condensation of 2,2-diethyl-l,3-dioxolan-4-one lithium or zirconium enolates with aldehydo sugars has afforded higher carbon aldonic acid derivatives, e.g. 1. The synthesis of L-ribono-1,4-lactone has been achieved from d-isoascorbic acid by way of the tetrose and pentitol derivatives 2 and 3 and the d-ribonolactone derivative 4 has been efficiently epimerized to the L-lyxonolactone 5 (Scheme 1). A selective i yn-epoxidation of racemic 2-0-benzyl-4-alkenamides followed by hydrolysis has afforded 3-deoxy-pentono-1,4-lactones. 

Reduction of 1-nitro-l-alkene derivatives such as 65 provided 2-deoxy-aldose oximes and their elimination products such as 66 and 67, respectively (Scheme 11). The oxime 66 could be converted into the corresponding free 2-deoxy-sugar, 2-deoxy-aldononitrile and 2-deoxy-aldonic acid. Radical cyclization of 5-keto-aldose aldoximes to give aminocyclopentitol derivatives is covered in Chapter 18. 

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