L-galactono-1,4-lactone

Acetals of L-galactono-1,4-lactone (an abundant byproduct of the sugar beet industry) have thermotropic liquid crystalline properties. Acetalization in DMF containing H2S04 in the presence of anhydrous CuS04 gave (after 12 to 24 h at 40 °C) yields of 20-35% (Scheme 8.27). 

The major pathway probably proceeds via D-galacturonic acid and L-galactono-1,4-lactone, as these are converted to L-ascorbic acid by mitochondria prepared from peas and mung beans, but neither L-gulono-1,4-... 

L-Galactono-1,4-lactone (16) is prepared in three steps (51%, overall yield) from 2a applying two successive asymmetric dihydroxylations (ADs) [25] (Scheme 6). 

Acetals of o-GlcpNAc 28a (Z=NHAc) [99] and o-Glcp 28b [55] were prepared by condensation of the appropriate aldehyde or aldehyde dimethyl acetal with the unprotected carbohydrate. An improvement of the classical methods of acetalation (microwave irradiation of montmorillonite) made it possible to synthesize various 5,6-0- -alkylacetals of L-galactono-1,4-lactone [100]. 

It was also found that L-gulono-1,4-lactone (21) is enzymically oxidized to L-ascorbic acid (1) in 40% yield by using an enzyme system isolated from a variety of natural sources, including rat livers and germinating peas.378 L-Galactono- 1,4-lactone (16) was also oxidized to 1 with this enzyme system. 

Keywords L-galactono-1,4-lactone, aldehyde, montmorillonite, microwave irradiation, acetals... 

Plants form ascorbate from GDP-mannose via GDP-L-galactose, L-galactose and L-galactono-1,4-lactone. The latter is oxidized to L-ascorbic acid by a mitochondrial L-galactono-1,4-lactone dehydrogenase, using cytochrome c as electron acceptor. The biosyntheis of L-ascorbic acid has been reviewed.337... 

M. Csiba, J. Cleophax, S. Petit, and S. D. Gero, Expedient and practical three-step synthesis of vitamin C from a byproduct of the sugar industry the L-galactono-1,4-lactone pathway, J. Org. Chem., 58 (1993) 7281-7282. 

Baig, M.M., Kelly, S., and Loewus, F., 1970, l-Ascorbic acid biosynthesis in higher plants from L-gulono- or L-galactono-1,4-lactone. Plant Physiol. 46 277-280. 

GALDH shows a high enantio-preference for L-galactono-1,4 -lactone (13). Reoxidation of the two-electron reduced enzyme by cytochrome c occurs in two single-electron steps and involves the intermediate formation of the red anionic flavin semiquinone (Fig. lb). Related aldonolactone oxidoreductases act as true oxidases, which suggests that they provide a better access of molecular oxygen to the active site. 

It has been reported by Coleby that, when solutions of n-glucono-l, 4-lactone, D-gulono-1,4-lactone, L-galactono-1,4-lactone and L-gulono-1,4-lactone are irradiated with x-rays (210kVp, 10mA), 7-rays (Co ), and fast electrons (4 Mev) under vacuum, the lactones are converted into the corresponding ascorbic acids. 

Chromatographic methods have also been developed for quantitative determination of the AUC of pectin. Uronic acids have been analyzed using gas-liquid chromatography (GLC) after conversion to L-galactono-1,4-lactone via potassium borohydride reduction and lactonization using methanolic hydrogen chloride. The derived lactone was then analyzed by GLC as the trimethylsilyl derivative (Perry... 

Preparation. L-Lyxose may be prepared from L-galactono-1,4-lactone by the Ruff degradation method.36... 

Because of their interest in products with liquid crystalline and surfactant properties, Csiba et al. [15] synthesized some amphiphilic derivatives of L-galactono-1,4-lactone 24, a by-product of the sugar beet industry available in large quantities. Reactions between 24 and hexyl, heptyl, octyl, decyl, dodecyl, and myristyl aldehydes on montmorillonite KSF or KIO were performed in a focused open-vessel micro-wave system for 10 min in the absence of solvent (Scheme 12.10). Protected derivatives 25a-f were afforded with yields (60-89%) considerably better than those (22-38%) obtained by conventional heating for 24 h in the presence of sulfuric acid. 

Bleeg, H. S., and Christensen, F., 1982, Biosynthesis of ascorbate in yeast. Purification of L-galactono-1,4-lactone oxidase with properties different from mammalian L-gulonolactone oxidase, Eur. J. Biochem. 127 391-396. 

L-Glyceraldehyde, readily prepared in high optical purity from L-galactono-(1-4.)-lactone, was condensed with dihydroxyacetone to yield, after treatment with acetone-sulphuric acid, 2,3 4. 5-di-O-isopropylidene-L-fructopyranose. Attempts to apply the... 

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