Galactonic acids

The cyclization of pentaacetyl-o-gluconic thioamide with chloroacetone and of pentaacetyl-D-galactonic acid thioamide with phenacyl bromide give the corresponding 4-substituted 2-(D-galactopentaacetoxypentyl)-thiazoles (27) (660) but in low yield (23 to 27%) (Scheme 13). The products may be deacetylated in the usual way. These compounds are interesting from a pharmacological point of view. 

Lacton-bindung, /, lactonic linkage, -saure, /. lactonic acid, lactone acid (a compoimd which is both an acid and a lactone) lactonic acid, D-galactonic acid. 

The 2-keto acids such as 2-keto-D-galactonic acid (XXIV) can be derived from the corresponding osone (XXIII) by oxidation with bromine.10 Oxidation of L-gulosone by the same method has provided 2-keto-L-gulonic acid. The success of this oxidation depends to a large extent upon the purity of the osone subjected to oxidation and this, as previously stated, is controlled by the purity of the osazone. 

By analogy with the biosynthesis of L-ascorbic acid and with other oxidation-reduction enzyme systems, it seems likely that D-galactose is oxidized to D-galacturonic acid (XXIII) on reduction at Cl, this yields L-galactonic acid (XXIV), the 1,5-lactone (XXV) of which, on reduction at Cl, would give L-galactose (XXII). 

D-Glucose — D-glucuronic acid — L-gulonic acid — L-ascorbic acid D-Galactose — D-galacturonic acid — L-galactonic acid — L-ascorbic acid... 

Fleet reported the synthesis of a new class of carbopeptoid-cyclodextrin, cyclo[(6-amino-6-deoxy-D-galactonic acid)4] with a 28-membered ring in which... 

DL-galactonic acid (39). 1,4-Anhydro-DL-talitol (3,6-anhydro-DL-altritol) (40) gave 2-0-(carboxymethyl)-DL-threaric acid (41) and 1,4-anhydro-D-mannitol (42) gave 2-0-(carboxymethyl)erythraric acid (43). 

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