iduronate and guluronic-acid

l-Iduronic acid is a key constituent of heparin and heparan sulfate polysaccharides due to its unique conformational plasticity, which facilitates the binding of polysaccharides to proteins. At the same time, this is the synthetically most challenging unit of heparinoid oligosaccharides; therefore, there is a high demand for its replacement with a more easily accessible sugar unit. In the case of idraparinux, an excellent anticoagulant heparinoid pentasaccharide, we demonstrated that l-iduronic acid can be replaced by an easier-to-produce l-sugar while maintaining its essential biological activity. From the inexpensive d-mannose, through a highly functionalized phenylthio mannoside, the l-gulose donor was prepared by C-5 epimerization in 10 steps with excellent yield. This unit was incorporated into the pentasaccharide by α-selective glycosylation and oxidized to l-guluronic acid. The complete synthesis required only 36 steps, with 21 steps for the longest linear route. The guluronate containing pentasaccharide inhibited coagulation factor Xa by 50% relative to the parent compound, representing an excellent anticoagulant activity. To the best of our knowledge, this is the first biologically active heparinoid anticoagulant which contains a different sugar unit instead of l-iduronic acid.

Topics: Anticoagulants; Heparinoids; Iduronic Acid; Mannose; Oligosaccharides

A sensitive high-performance liquid chromatographic (HPLC) method for the determination of uronates isolated from polysaccharides found in natural products such as glycosaminoglycans and alginate is described. Preparation of iduronate, guluronate, and mannuronate as analytical standards for high performance liquid chromatography was achieved by depolymerization of dermatan sulfate and alginate in 2.5 mol L(-1) trifluoroacetic acid at 100°C for 6h. Structures of resulting products (iduronate, guluronate, and mannuronate) were characterized by 600 MHz (1)H NMR. Five uronates (glucuronate, iduronate, mannuronate, guluronate, and galacturonate) were separated on a Dionex CarboPac PA1 column using an isocratic elution with 8 mmol L(-1) acetate buffer (pH 4.84) and were monitored by fluorescence detection using 1.5% 2-cyanoacetamide as a post-column fluorogenic reagent. As little as 50 pmol of each uronate could be detected with excitation at 331 nm and emission at 383 nm.

Topics: Alginates; Chromatography, High Pressure Liquid; Dermatan Sulfate; Fluorometry; Glucuronic Acid; Hexuronic Acids; Iduronic Acid; Polysaccharides; Temperature; Trifluoroacetic Acid; Uronic Acids