Galactono-1,5-lactone synthesis

A. Chiocconi, C. Marino, E. Otal, and R. M. de Lederkremer, Photoinduced electron transfer and chemical a-deoxygenation of D-galactono-1,4-lactone. Synthesis of 2-deoxy-D-/yxo-hexo-furanosides, Carbohydr. Res., 337 (2002) 2119-2126. 

Scheme 3 Synthesis of L-galactono-1,5-lactones from 2,4-hexadienoates...

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. 

Lactone 30 on oxidation at C2 gives ketolactone (31), which on hydrolysis in acetic acid-water afforded L-ascorbic acid (Scheme 16). This synthesis and the Bakke-Theander synthesis are among the few syntheses that do not have as the last step the lactonization of an appropriate 2- or 3-keto sugar acid or derivative. The approach shown in Scheme 16, the protection of either the C2 or C3 hydroxyl group in an appropriate 1,4-lactone followed by the oxidation of the unprotected hydroxyl to a ketone and then by hydrolysis, can be generally used to convert L-gulono-, L-galactono, and L-talono-l,4-lactone to L-ascorbic acid (50). 

M. Bols, I. Lundt, and C. Pedersen, Simple synthesis of (R)-carnitine from D-galactono-1,4-lactone, Tetrahedron, 48 (1992) 319-324. 

Romero Zaliz C.L., Varela O., Facile synthesis of a o-galactono-1,6-lactone derivative, a precursor of a copolyester, Carbohyd. Res., 341, 2006, 2973-2977. 

Mapson, L. W., and Breslow, E., 1958, Biological synthesis of L-ascorbic acid L-Galactono-y-lactone dehydrogenase, Biochem. J. 68 395-406. 

Oba, K., Fukui, M., Imai, Y., Iriyama, S., and Nogami, K., 1994, L-Galactono-7-lactone dehydrogenase Partial characterization, induction of activity and role in the synthesis of ascorbic acid in wounded white potato tuber tissue, Plant Cell Physiol. 35 473-478. 

Confirmation that the synthesis of n-ascorbic acid m vwo does in fact proceed via these or very similar routes was obtained in work in which the enzymic oxidation in vitro of L-galactono-7-lactone to L-ascorbic acid by plant mitochondria was demonstrated (Mapson et al., 1954). The enzymes responsible were located entirely within the cytoplasmic particles (mitochondria), and their activity depended on the maintenance of the mitochondria in an intact condition. 

Since the change L-galactono-y-lactone — L-ascorbic acid involves the transfer of hydrogen, the presence of a suitable hydrogen acceptor was essential. Of several tried, oxygen was the only one found to be effective in its absence there was no synthesis. 

Chirality from D-mannose was used to establish most of the chiral centres in a synthesis of the lichen metabolite (+)-aspicillin (32 sugar carbons numbered).30 The known lactone (33), accessible in two steps from d-galactono-y-lactone, was used to prepare the fragment (34) containing the chirality of C(21) - C(27) of the antineoplastic bryostatins.31 OH... 

Isbell made use of this reaction to S3mthesise vitamin C from L-galactono-y-lactone. The latter was first converted into the 2-0x0 derivative (see p. 83). A commercial synthesis of ascorbic acid is also based on this isomerisation. Bertrand s sortose bacterium, Acetobacter xylinium, converts sorbitol to L-sorbose (XCI) and this on condensation with acetone yields the 2,3 4,5-di-O-isopropyhdene derivative (XCII). Oxidation and hydrolysis of this... 

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