Esters of Glycuronic Acids

Far fewer biosynthetic, 1-esterified D-glucuronic acids than D-gluco-siduronic acids have thus far been described in part, this may be due 

Attempts to use a Lewis acid to anomerize the ester linkage at C-l from /3 to a have thus far been mostly unsuccessful however, application of Bonner s249 procedure, involving anomerization of acetylated aldoses in an acid anhydride containing an acid catalyst, was found246 to be applicable to the acetylated D-glucopyranuronate series also. Thus, /3 — a anomerization of methyl tri-0-acetyl-l-0-propanoyl-/3-D-glucopyranuronate (prepared by the silver salt method) was achieved 

All attempts to obtain free 1-esters from 77 by alkaline hydrolysis failed,246 because the splitting of the 1-ester linkage always occurred before deacetylation of the molecule was complete. Thus, the use of methanolic ammonia, or various molar ratios (1 1 to 5 1) of methan-olic sodium methoxide, led invariably to formation of the corresponding aglycon amide and methyl ester, respectively with catalytic amounts (ratio 100 3) of sodium methoxide, most of the starting material remained unchanged. 

Access to the unprotected, 1-esterified D-glucopyranuronic acids was provided251 by way of synthesis of the perbenzylated 1-O-acyl derivatives (78), followed by catalytic debenzylation. Thus, reaction of the benzylated intermediate 13 (having OH-1 free) with aliphatic acids in the presence of DGC, or with aroyl chlorides in pyridine, led 

Chemical Shifts (6 Values) of Anomeric and Acetoxyl Methyl Protons of Methyl 2,3,4-Tri-O-acetyl-l-O-acyl-D-glucopyranuronates  

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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. 

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). 

Base-catalyzed esterification of D-glucurono-6,3-lactone proceeds smoothly at room temperature.242 The acetylated glycuronic acids, and the per-O-acetylglycosyluronic halides of their methyl esters, are important precursors for the synthesis of glycosiduronic acids. D-Glucofuranurono-6,3-lactone... 

Oxidations involving 2-ketose or glycuronic acid residues also give satisfactory data ° the acids being best examined in the ester form in order to minimize overoxidation. Periodate oxidation is effective as well for structural elucidation of sialic acid-containing oligosaccharides. ... 

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