Joseph Kiss

β-Eliminative Degradation of Carbohydrates Containing Uronic Acid Residues

Publisher Summary This chapter discusses that carbohydrates containing uronic acid residues occur in nature in a wide variety of polysaccharides and other sugar conjugates of animal, plant, and micro-organism origin. By using modern methods of preparative, analytical, and physical chemistry, it has become possible, during the past two decades, to elucidate the paths and mechanisms of some reactions in this field. Carbohydrates having many asymmetric centers in their pyranoid and furanoid ring-systems have proved to constitute an area rich in stereochemical questions and complex reaction-mechanisms. The purpose of this chapter is to record the progress that has been made during the past 20–25 years in the special field of uronate-sugar conjugates. Besides the theoretical interest of many uronate-sugar conjugates, their medicinal and industrial applications are constantly growing. The chemistry and biochemistry of D-glucuronic acid and its structurally simple conjugates have been reviewed in the chapter.

Synthesis of heparin saccharides—V : Anomeric o-benzyl derivatives of l-idopyranosyluronic acid☆

Abstract Derivatives of the anomeric benzyl l -idopyranosides and l -idopyranosiduronates have been synthesized from d -glucose as models for conformation studies. The two key reactions in the synthesis are: (a) inversion of configuration at C(5) of the d -glucofuranose derivative 4 , and (b) catalytic oxidation of the l -idopyranosides 19 , and 22 to uronic acids.

Glycosphingolipids (Sugar-Sphingosine Conjugates)

Publisher Summary Glycosphingolipids are a group of sphingolipids containing mono or oligosaccharide residues. The sugar residues are in direct or indirect glycosidic conjugation with the primary hydroxyl group of the N -acylated sphingosine or dihydrosphingosine molecule. In nature, only a relatively small number of glycosphingolipids exist in which the secondary hydroxyl group of the sphingosine moiety is in covalent conjugation with fatty acids or with fat-aldehyde residues or the sugars are connected to the long-chain, acylamido polyhydric alcohol through a phosphatidylinositol bridge. Significant structural variation is visualized in the natural glycosphingolipids. The fatty acids bound on the amino group of the sphingosine can differ. The chemical structure of the longchain, amino alcohol skeleton can also be varied. The solubility characteristics are considered essential in the biological roles of the glycosphingolipids when they function as biomembrane components. In specific, the fatty acid group and the sugar moiety in the sphingosine moiety have opposing effects. The long-chain fatty acids are extremely soluble, having strongly hydrophobic character. On the other hand, the sugar moiety of the glycosphingolipids represent the hydrophilic part of the molecule.

Synthesis and O.R.D./C.D. spectra of the anomers of 2-amino-5-ethoxyphenyl d-glucopyranosiduronic acid and some derivatives thereof

Abstract Metabolites of phenetidine and phenacetin, namely, 2-amino-5-ethoxyphenyl β- d -glucopyranosiduronic aicd and 2-acetamido-5-ethoxyphenyl β- d -glucopyranosiduronic acid were synthesized from 5-ethoxy-2-nitrophenol and the d -glucosyluronic bromide, by the method of Koenigs and Knorr. The β anomers of the d -glucopyranosiduronic acid were obtained; these were identical with the natural metabolites. For proof of the anomeric configuration, the corresponding α-anomers of the aryl d -glucosides and d -glucosiduronic acids were also synthesized: condensation of the above aglucon with the Brigl anhydride led to the α- d -glucopyranoside, which was then oxidized to the corresponding α- d -glucopyranosiduronic acid. The o.r.d. and c.d. spectra of these aryl α- and β- d -glucopyranosides and - d -glucopyranosiduronic acids were recorded, and preliminary indications as to a relationship between the sign of the Cotton effect in the region of 274–280 nm and the anomeric configuration were obtained. Furthermore, some data from the n.m.r. spectra of the pure anomers of these d -glucosides and d -glucopyranosiduronic acids are given.

An Allylic Rearrangement Arising from Reaction of Fluoride Ion and A 3-Chloro, 4,5-Unsaturated Uronate Derivative

Abstract Reaction of methyl [benzyl 2-[(benzyloxycarbonyl)-amino]-3-chloro-2,3,4-trideoxy-β-L-threo-hex-4-enopyrano-sid]uronate,3,4-trideoxy-β-L-threo-hex-4-enopyranosidjuronate (7) with silver fluoride gave the 5-fluoro, 3,4-unsaturated uronate derivative 8, which, on treatment with methanolic ammonia, afforded the corresponding 5-meth-oxy, uronamide 9. The structures of 8 and 9 were confirmed by spectral data and by x-ray crystallographic analysis of 8. 1H NMR spectroscopy parameters for 9 and its diastercomen 11 have been used to probe the conformational preferences in solution.