Aldonic acids, synthesis

Dideoxyaldonic acids have been prepared by hydrogenation of derivatives of the intermediate ( )-2,3-dideoxyald-2-enonic acids in the aldonic acid synthesis of Kochetkov and Dmitriev.41... 

Much of the chemistry of monosaccharides is the familiar chemistry of alcohols and aldehydes/ketones. Thus, the hydroxyl groups of carbohydrates form esters and ethers. The carbonyl group of a monosaccharide can be reduced with NaBH4 to form an alditol, oxidized with aqueous Br2 to form an aldonic acid, oxidized with HNO3 to form an aldaric acid, oxidized enzymatically to form a uronic acid, or treated with an alcohol in the presence of acid to form a glycoside. Monosaccharides can also be chain-lengthened by the multistep Kiliani-Fischer synthesis and can be chain-shortened by the Wohl degradation. 

Aldono-1,5-lactones and free aldonic acids react with alcohols in the presence of hydrogen chloride to give the corresponding alkyl aldonates (84). The reaction is slower with 1,4-lactones. Because esterification takes place very slowly in the absence of an acidic catalyst, aldonic acids and their lactones may be recrystallized from boiling alcohols without appreciable esterification (85). However, in some instances, alkyl esters are formed under these conditions. For example, essentially pure ethyl L-mannonate was isolated (6.4% yield) from the mother liquors of crystallization L-man-nono-1,4-lactone, obtained by Kiliani synthesis from L-arabinose (86). Similarly, repeated recrystallization from ethanol of crude 2,3,4,6-tetra-O-acetyl-D-glucono- 1,5-lactone afforded the corresponding ethyl gluconate derivative (87). 

Glucose Oxidase-catalysed Synthesis of Aldonic Acids 323... 

We have devised a very simple procedure for the preparative synthesis of various aldonic acids from the corresponding aldoses. This green chemistry process takes advantage of the availability of cheap, robust industrial enzymes. 

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). 

G. Limberg, I. Lundt, and J. Zavilla, Deoxyiminoalditols from aldonic acids. VI. Preparation of the four stereoisomeric 4-amino-3-hydroxypyrrolidines from bromodeoxytetronic acids. Discovery of a new a-mannosidase inhibitor, Synthesis (1999) 178-183. 

The first surface-initiated enzymatic polymerization reported was the synthesis of amylose brushes on planar and spherical surfaces [145]. For this, silica or silicone surfaces were modified with self-assembled monolayers of (3 amino-propyl)trimethoxysilane or chlorodimethylsilane, respectively. To these functionalities, oligosaccharides were added via (a) reductive amidation of the oligosaccharides to surface-bound amines, (b) conversion of the oiigosaccharide to the according aldonic acid lactone and reaction with surface bound amines, and (c) incorporation... 

Among the classic methods for the extension of the aldose chain by one carbon atom from the reducing end [9J, the Kiliani-Fischer cyanohydrin synthesis [10] is a milestone in carbohydrate chemistry. However after 110 years from discovery and numerous applications [11], including the preparation of carbon and hydrogen isotopically labeled compounds for mechanistic and structural studies [12], there are still several drawbacks that make the method impractical. These are the low and variable degree of selectivity and the harsh reaction conditions that are required to reveal the aldose from either the aldonic acid or directly from the cyanohydrin. Synthetic applications that have appeared in recent times confirmed these limitations. For instance, a quite low selectivity was registered [13] in the addition of the cyanide ion to the D-ga/acfo-hexodialdo-l,5-pyranose derivative 1... 

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. 

C. Pedersen Synthesis of bromodeoxy compounds from hexoses, polyols and aldonic acids... 

Fully acetylated aldonic acids can be prepared by oxidation of aldehydo-sugar peracetates. Direct acetylation of certain aldonic acid salts is possible, and addition of cadmium salts, in particular, affords high yields of acetates. The synthesis can also be accomplished by deamination of the readily prepared, acetylated amides with nitrous acid or nitrosyl chloride. Examples of the various methods are given in Ref. 86. 

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. 

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