Of glycuronic acids

A polysaccharide (glycan) composed entirely of glycuronic acid residues is named byreplacing -icacid by -an . The generic name for this group of polysaccharides is glycuronan . 

The c.d. spectra of glycuronic acids have been measured in a number of laboratories. " These sugar derivatives, named after the corresponding aldohexose, have the exocyclic hydroxymethyl group on C-5 replaced by the carboxyl chromophore. The structure of /3-D-mannopyranuronic acid is given as an example in formula 9, and the structures of the parent compounds in Fig. 1. 

Martens, D.A. and Frankenberger, Jr., W. T., Determination of glycuronic acids by high-performance anion chromatography with pulsed amperometric detection, Chromatographia, 30, 651, 1990. 

Little information is available on the decarboxylation of glycuronic acids, other than from those derived from hexoses. Machida103 reported that both D-xyluronic acid and D-arabinuronic acid undergo decarboxylation in boiling, 12% hydrochloric acid, but the yields of... 

The final stages of the biosynthetic process may include transfer of a polysaccharide chain from an intermediate acceptor to a final acceptor, or liberation of the free polysaccharide. Monosaccharide residues included in a polymeric chain may be subjected to further enzymic modifications, such as incorporation of O-linked substituents (see Section III,6) or the epimeri-zation at C-5 of glycuronic acid residues mentioned in Section 111,1,c. 

Aldonic and aldaric acids are usually obtained by oxidation methods from the corresponding aldoses, whereas a glycoside is the usual starting material for the synthesis of glycuronic acids, important natural sugars that are constituents of many polysaccharides. 

Methods for the chemical synthesis of glycuronic acids include (i) reduction of the monolactones of aldaric acids, (ii) oxidation of the primary alcoholic group of aldose derivatives, (iii) oxidative degradation procedures, (iv) chain-extension reactions on dialdoses, and (v) epimerization reactions. 

The literature on /3-D-glucosiduronic acids is particularly voluminous, and the subject has been extensively reviewed from several aspects. Section III, dealing with this class of compounds, is devoted more to a general overview of their preparation, characterization, and reactions than to individual members. On the other hand, the categories of 1-esters of glycuronic acids and of (glycosylamine)uronic acids, which appear not to have been treated previously as separate topics, receive relatively more attention. 

Nucleosides of glycuronic acids have been examined356 by 1H-n.m.r., o.r.d., and i.r. spectroscopy as suitable, model compounds of the rotamer states about the nucleosidic C-N bond. The carboxylate group on C-4 of an oxidized nucleoside has also been used357 as a protecting device its production from the nucleoside (by oxidative methods), and regeneration therefrom (by reduction with sodium... 

In human pregnancy urine, the hormone is chiefly oestrone in urine of the cow or mare, it is chiefly oestriol. Both oestrogens are excreted as inactive esters of glycuronic acid, until the onset of labour, when they appear in the free form (Cohen and Marrian, 1935). 

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