Uronate—sugar conjugates

II. Common Structural Feature of Uronate-Sugar Conjugates, and the... 

V. Selective /3-Eliminative Cleavage of Natural Uronate-Sugar Conjugates.. . 238... 

The amount of the aforementioned uronate-sugar conjugates produced yearly in Nature is very large. Like cellulose and starch, they are among the most abundant natural substances produced by living organisms on the Earth. 

It is difficult to test more exactly the stereochemistry of the different types of endocyclic, enolacetal-forming, /8-elimination processes on the natural, macromolecular, uronate-sugar conjugates. Hence, model compounds have been synthesized on which the alkali-catalyzed, /8-elimination processes could be conducted under well controlled conditions. In addition, the exact determination of certain parameters, such as the conformation of the starting materials used for the experiments and of the reaction products, was much easier than for the macromolecular conjugates. 

Carbohydrates containing uronic acid residues occur in Nature in a wide variety of polysaccharides and other, sugar conjugates of animal, plant, and micro-organism origin. 

Pyranuronates and furanuronates having an enolacetal linkage are readily prepared, for example, by the alkali-catalyzed, sulfonate or phosphate j3-elimination reaction. Such unsaturated uronates have proved to be valuable starting-materials in the preparation of divers rare sugars and sugar conjugates. Nevertheless, only a few publications in this interesting field have thus far appeared. 

A (D-glucosylamine)uronic acid derivative has been identified331 as the metabolite of carbamazepine (5//-dibenz[fe,/]azepine-5-carbox-amide, an anti-epileptic agent) by means of permethylation, g.l.c., and mass spectometry. Analytical data for the conjugate (identified in the bile of the isolated, perfused, rat liver) indicated that the carboxamide nitrogen atom is linked to C-l of the sugar moiety. 

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