Glucuronic acid, bromination

The reducing group in uronic acids can be oxidized by nitric acid or bromine to yield aldaric acids. Uronic acids, as salts, can be quantitatively reduced to aldonic acids by borohydride.239 Lactones are readily reduced, as in the controlled conversion of D-glucurono-6,3-lactone into D-gluco-hexodialdose. The carboxyl group of glucuronic acids may be reduced to a primary alcoholic group. 

The brominated sugars are usually quite stable and can be useful for a variety of purposes [151]. Substitution of bromine with deuterium can be used for preparation of labeled carbohydrates, while substitution with hydrogen sometimes can be used for inverting the stereochemistry. Noteworthy is the conversion of D-glucuronic acid derivative 61 into the corre-... 

When borneol (ROH) is fed to a dog, this toxic substance is excreted as compound P, QHgOe—OR, where R stands for the bornyl group. Compound P does not reduce Benedict s solution. It reacts with aqueous NaHC03 with the liberation of a gas. Treatment of P with aqueous acid yields borneol (ROH) and D-glucuronic acid (Table 34.1), which is oxidized by bromine water to D-glucaric acid. 

Conversion of alditols to aldoses without the need to protect all hydroxy groups has been achieved by monotosylation of one primary hydroxy group, displacement with azide ion and photolysis in methanol to yield the aldimine,which was then hydrolyzed to the aldose. The procedure was illustrated using 3 4-0 isopro ylideno-D-mannitol to produce D-mannose. The synthesis of D-[U- Cjgalactose from methyl <-D-[n- Cjglucopyranoside via aqueous bromine oxidation to the 4.-uloside, reduction by sodium borohydride and hydrolysis has been described, along with the isolation of D-glucuronic acid and methyl o( D-mannopyranoside as by-products. 

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