Galactonate

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-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. 

Figure 10.11 Aldol reactions catalyzed in vivo by the 2-keto-3-deoxy-6-phospho-o-gluconate and 2-keto-3-deoxy-6-phospho-o-galactonate aldolases.

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... 

Procedure Synthesis of Xylonic, Galactonic, Mannonic, 2-Deoxygluconic Acid and Synthesis of 2-Amino-2-deoxy-gluconic Acid (Glucosaminic Acid)... 

This enzyme [EC 4.2.1.6] catalyzes the conversion of D-galactonate to yield 2-dehydro-3-deoxy-D-galactonate and water. 

This enzyme [EC 4.1.2.21], also referred to as 6-phospho-2-dehydro-3-deoxygalactonate aldolase, catalyzes the reversible conversion of 2-dehydro-3-deoxy-o-galactonate 6-phosphate to pyruvate and o-glyceraldehyde 3-phos-phate. 

GALACTOSYLCERAMINIDASE GALACTOKINASE GALACTONATE DEHYDRATASE GALACTOSE 1-DEHYDROGENASE GALACTOSE OXIDASE... 

Fleet et al. have described some oligomers of 0-protected-6-amino-6-deoxy-o-allonate [66] and o-galactonate [67], as intermediates in the preparation of poly-hydroxylated Nylon 6 analogs. 

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