Uronic acids ester deriv

Uronic acid azides constitute important precursors for A -glycosyl amino acids and their various peptide derivatives, and may be formed by a comparable pathway. Thus, the treatment of acetyl-protected uronic acid esters with tri-methylsilyl azide and SnCU gives the desired acetylated 1,2-trans methyl (o-glycopyranosyl azide)uronates in crystalline form. " Whereas the yields for the gluco 61 and galacto derivatives 62 are satisfactory, the manno analog 63 was obtained in only 11 % yield. Even with an excess of trimethylsilyl azide, the results could not be improved. ... 

Dissociation constants of o-glucuronic acid, o-galacturonic acid, their methyl ethers, and the corresponding 4,5-unsaturated derivatives have been measured and rationalized in terms of various operating electronic factors. Observations on details of the reduction of uronic acid esters to hexopyrano-sides, on nitrogen-containing derivatives, and on branched-chain uronic acids are made in Chapters 3, 9, and 13, respectively. 

Uronic acid derivatives are also known among the guanosine 5 -pyrophosphate esters. A mixture of the a-D-mannopyranosyluronic acid ester (20) and, presumably, the /J-L-gulopyranosyluronic acid ester (21) was isolated from the brown alga Fucus gardneri,88 The conversion of the uronic acid in the ester 20 into D-mannitol, and that... 

Chromatographic separation of free nucleotides from various sources usually gives the glycosyl esters of uridine 5 -pyrophosphate in three fractions, containing fhe derivatives of neutral monosaccharides, uronic acids, and 2-acetamido-2-deoxyglycoses, respectively. 

The sole component of the uridine diphosphate uronic acid fraction from animal tissues,10,124,139 Chlorella,4 red algae,83 and some bacteria118,119 is uridine 5 -(a-D-glucopyranosyluronic acid pyrophosphate) (32), whereas a similar preparation from Pneumococcus140 contains only the a-D-galactopyranosyluronic acid derivative. Both esters have been shown to occur in extracts of mung bean.141,142... 

Oxidation of methyl 3,4-isopropylidene-2-desoxy-a-D-galactoside with potassium permanganate in the presence of potassium hydroxide afforded methyl 3,4-isopropylidene-2-desoxy-a-D-galacturonoside (LXXXIV) as its potassium salt. This could readily be converted into methyl 2-desoxy-a-D-galacturonoside (LXXXV) and both LXXXIV and LXXXV afforded crystalline esters and amides.230 The uronic acid derivative could be reduced by lithium aluminum hydride in ethereal solution to give methyl 3,4-isopropylidene-2-desoxy-a-D-galactoside.230 Although 2-des-... 

Quillaia bark or soapbark is derived from the tree Quillaja saponaria (Rosaceae) and other Quillaja species found in Chile, Peru, and Bolivia. The bark contains up to 10% saponins, a mixture known as commercial saponin , which is used for its detergent properties. Quillaia s surfactant properties are occasionally exploited in pharmaceutical preparations where it is used in the form of quillaia tincture as an emulsifying agent, particularly for fats, tars, and volatile oils. The bark contains a mixture of saponins which on hydrolysis liberates quillaic acid (Figure 5.62) as the aglycone, together with sugars, uronic acids, and acids from ester functions. 

Ault, Haworth and Hirst47 first synthesized the methyl a-D-glycoside methyl ester of 2,3,4-tri-O-methyl-D-mannuronic acid by successive treatment of potassium (methyl a-D-mannopyranosid)uronate with dimethyl sulfate and sodium hydroxide, and then methyl iodide and silver oxide. Although no crystalline derivatives were isolated, there is little doubt about its structure, since the authors48 subsequently proved the presence of a pyranose ring in the starting material for the synthesis, methyl 2,3-O-isopropylidene-a-D-mannoside. The uronic acid has also been synthesized by Smith, Stacey and Wilson,28 who oxidized methyl... 

Methyl-,4C D-glucuronate was prepared44 from the D-glucofuran-uronic acid derivative 22 (obtained by benzylidenation of D-glu-curonic acid in the presence of zinc chloride) by treating its sodium salt with methyl-14C iodide, followed by hydrogenolysis of the ester 23 in the presence of palladium-on-carbon the infrared (i.r.) spectrum of the product was identical to that of authentic 2. 

In other approaches, the glycosidic bond is synthesized in some masked form. Thus, in Barett s reductive glycosylation [634] (Scheme 4.61), an ester bond is created first at the anomeric center using the uronic acid derivative 293. Thionation of the carbonyl group of 294 was followed by reductive desulfurization to give the disaccharide 296. 

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