D-galacturonic Acid Derivatives Research Articles

Efficient microwave-promoted synthesis of glucuronic and galacturonic acid derivatives using sulfuric acid impregnated on silica

Monomode microwave-assisted syntheses of d-glucuronic and d-galacturonic acid derivatives are reported in the presence of a solid acid catalyst, consisting of sulfuric acid loaded onto silica. This approach affords a variety of surface-active monoglycosylated glucofuranosidurono-6,3-lactones and disubstituted galacturonic adducts in excellent yields in less than 10 min at 85°C. This study illustrates the application of microwave heating mode, in combination with a cost-effective solid catalyst, as an efficient, selective, and eco-friendly methodology in carbohydrate chemistry.

Fungal Glucuronoyl Esterases and Substrate Uronic Acid Recognition

Glucuronoyl esterases are enzymes involved in microbial plant cell-wall degradation. In this study we purified and characterized two recombinant Phanerochaete chrysosporium glucuronoyl esterases, PcGE1 and PcGE2. The catalytic activity of these and previously described glucuronoyl esterases was investigated on new synthetic substrates, methyl esters of uronic acids and their glycosides, prepared by esterification with ethereal diazomethane.The data obtained indicate that the enzymes hydrolyzed efficiently not only esters of 4-O-methyl-D-glucuronic acid, but also methyl esters of D-glucuronic acid carrying a 4-nitrophenyl aglycon. Moreover, the fact that they did not recognize the 4-epimers of these compounds, the D-galacturonic acid derivatives, supports the hypothesis that these carbohydrate esterases attack ester linkages between 4-O-methyl-D-glucuronic acid of glucuronoxylan and lignin alcohols.

D-Galacturonic acid derivatives as acceptors and donorsin glycosylation reactions

Jones oxidation of suitably protected allyl β- d-galactopyranosides and subsequent esterificationwere reinvestigated. Partial deprotection of the resulting d-galacturonic acid derivatives afforded compounds suitable for transformation into glycosyl acceptors. The synthesis of 2-, 3-, and 4-trityl ethers, relying on efficient differential protecting-group strategies, is described. Trityl-cyanoethylidene condensation of these trityl ethers, leading to the protected disaccharide units β- d-Gal pA-(1 → 2)- d-Gal pA and β- d-Gal pA-(1 → 3)-Gal pA with high stereoselectivity, is demonstrated. A β- d-Gal pA-(1 → 4)- d-Gal pA disaccharide was also prepared.

D-Galactose-derived d-galacturonic acid derivatives suitable as glycosyl acceptors

Allyl ( 1a) and benzyl ( 1b) β- d-galactopyranosides were converted into methyl [allyl (and benzyl) 2- O-acetyl-3,4- O-isopropylidene-β- d-galactopyranosid]uronates, ( 6a and 6b) by three different routes. The carboxyl group was introduced by Jones oxidation of suitably protected precursors and esterified directly. The chemical behaviour of 6- O-trityl-, 6- O-(4,4′-dimethoxytrityl)-, and 6- O-(2-methoxypropane-2-yl)-derivatives was investigated. The overall yields obtained were strongly influenced by the protecting groups used, in particular their stability in acidic solution.

Purdie reagent-induced C(5)-epimerization of D-galacturonic acid derivatives in the presence of methyl sulphide

Purdie reagent-induced C(5)-epimerization of D-galacturonic acid derivatives in the presence of methyl sulphide

Separation of trimethylsilyl ethers of methyl(methyl 4-deoxy-O-methyl-β- l- threo-hex-4-enopyranosid)uronate by gas chromatography

may be found among the products of the methylation of D-glucuronic or D-galacturonic acid conjugates’-3. This class of substance is formed by p-elimination reactions of esterified uranic acid derivatives under alkaline4-6 and neutral conditions’ and may also be formed by the action of certain enzymes 8 *O. Elimination reactions in uranic acids have been extensively studied”-l4 and it can be concluded that this type of reaction is a general means of degradation of heteropolysaccharides and poly(hexopyranosid)uronates in nature. As a result of /I-elimination in hexuronic acids, the asymmetric centre at C4 is no longer present and, therefore, the same olefins are formed from D-glucuronic and D-galacturonic acid derivatives. The separation of O-methyl derivatives of methyl(methy1 a-D-glucopyranosid)uronate has been described earlier’“. In this paper, we describe the separation of methyl(methyl 2,3,4-tri-O-methyl-a-D-glucopyranosid)uronate (1) and methyl (methyl 2,3,4-tri-0-methyl-a-D-galactopyranosid)uronate (2) in admixture with differently substituted olefinic saccharides (3-6). In view of the possibility of determining the number and the location of the methyl groups in the derivatives of methyl 4-deoxy-P-L-rhreo-hex-4-enopyranosiduronic acid by mass spectrometry lb, this work is a contribution to the analysis and unequivocal identification of compounds l-6 by combined gas chromatography-mass spectrometry (GC-MS).

Properties of a polygalacturonic acid-synthesizing enzyme system from Phaseolus aureus seedlings

A cell-free enzyme system from Phaseolus aureus seedlings, which is capable of catalyzing the synthesis of polygalacturonic acid, was found to utilize UDP- d-galacturonic acid in preference to other nucleoside diphosphate d-galacturonic acid derivatives. It did not incorporate d-galacturonic acid residues from UDP-methyl- d-galacturonate into polygalacturonic acid. Maximum rate of polymerization occurs where preparations from seedlings germinated for 3 days are reacted with substrate at 30 °, pH 6, in the presence of 1.7 m m MnCl 2 and 0.4 m sucrose. The enzyme system has an apparent Michaelis constant of 1.7 × 10 −6 m, and at a substrate concentration of 3.7 × 10 −5 m will catalyze the polymerization of d-galacturonic acid residues at the rate of 4.7 mμmoles per milligram protein per minute. The enzyme is inactivated spontaneously, the rate of which is a function of temperature and pH. The addition of MnCl 2 delays inactivation.

246. Some derivatives of D-galacturonic acid

246. Some derivatives of D-galacturonic acid