Of D-galacturonic acid

The partial specific volume of the monomeric unit in PGA was found to be approximately 3 per cent higher than the value of D-galacturonic acid... 

The pyranose structure of D-galacturonic acid, which lactonizes with great difficulty, has been confirmed by Levene and Kreider66 from a study of the methylated ester of the uronoside. Methyl a-D-galacturonoside (XXXIII) was methylated with silver oxide and methyl iodide and there was obtained methyl 2,3,4-trimethyl-a-D-galacturonoside methyl ester (XXXVI) which on oxidation was converted to d,l(2,3,4-trimethylmucic) acid (XXXVII) and h-arabo-trimethoxyglutaric acid (XXXVIII). 

A series of crystalline salts of D-galacturonic acid has recently been prepared by Isbell and Frush.62 Some of these, e. g., calcium sodium D-galacturonate, are suitable for the separation of D-galacturonic acid from plant materials. 

Side chains of D-galacturonic acid residues in the pyranose or furanose forms may be attached to one or both of the positions R and R. ... 

The three acid-derived components of the hexuronic acids, namely, 5, 47, and 48, are essentially end products in the reaction. This is quite surprising, as 48 required only decarboxylation to form 2-furaldehyde. However, the rate of decarboxylation of the furoic acid was <2% of that of D-galacturonic acid under similar conditions. Furthermore, no trace of pentoses was noted in any of the reaction mixtures, which eliminates previous suggestions of their role in the mechanism of 2-furaldehyde for-... 

Polymers of uronic acids are encountered in nature in structures known as pectins, which are essentially chains of D-galacturonic acid residues linked al -> 4, though some of the carboxyl groups are present as methyl esters. These materials are present in the cell walls of fruit, and the property that aqueous solutions under acid conditions form gels is the basis of jam making. 

The sugar composition of the pectic polysaccharides obtained from these cell wall preparations (Table II) also suggested differences in the structural features of the different cell wall preparations. Detailed structural information is only available for the pectic polysaccharides obtained from the endosperm cell wall The main fraction of endosperm pectic polysaccharide was separated into two fractions, a neutral sugar-rich fraction and a fraction with a very high content of D-galacturonic acid (8). Structural... 

Closely related to plant gums are those mucilages discussed later which are the complex acid polysaccharides extractable from endosperms of seeds of such plants as flax, quince and lucerne (see below). The acid nature of these mucilages is due to the presence of D-galacturonic acid residues in the complex molecule. ... 

The crude gum tragacanth is a mixture of the salt of a complex acid polysaccharide and a neutral polysaccharide composed principally of L-arabinose residues. Starch is also present in the gum. The acid character of this gum is due to units of D-galacturonic acid and not D-glucuronic acid and it is of interest to note that in its ability to form gels it resembles pectin and the plant mucilages, which also contain D-galacturonic acid. 

In this clas of materials is grouped the majority of the seed mucilages, the acidity of which is due to a uronic acid (usually D-galacturonic acid) or to a methyl ether derivative of a uronic acid. This presence of D-galacturonic acid as the acidic component of the polysaccharide differentiates the mucilages from the gums, the acidity of the majority of which is due to the presence of D-glucuronic acid, or to one of its methyl ether derivatives (see above). 

The PGA salt of D AP has shown pharmacological results (peak timer shifted to a later time, increased Imax) corresponding to an increased contact time [12]. PGA consists of linear chains of D-galacturonic acid units (pyranose form), joined in a(l- 4)-glycosidic linkages, with a molecular weight ranging from 25 103 to 100 x 3. It formed a soluble salt or polyanionic complex with the... 

A cyclic diacetal of this type was employed by Ohle and Berend34ta) and by Link and his coworkers34(b)(o) in the synthesis of D-galacturonic acid. These investigators found that l,2 3,4-diisopropylidene-D-galac-tose was converted by permanganate oxidation in alkaline solution to the... 

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