Formation of isomers of anionic hemiesters of sugars and carbonic acid in aqueous medium. (16th June 2016)

• Record Type: Journal Article
• Authors: dos Santos, Vagner B.; Vidal, Denis T.R.; Francisco, Kelliton J.M.; Ducati, Lucas C.; do Lago, Claudimir L.
• Is Part Of: Carbohydrate research. Volume 428(2016)
• Page Start: 18
• Page End: 22
• Publication Date: 2016-06-16
• Subjects: Hemiester of carbonic acid -- Monoalkyl carbonate -- Sugar carbonate -- Isomers -- NMR spectroscopy; Carbohydrates -- Periodicals; Chemistry, Organic -- Periodicals; Biochemistry -- Periodicals; Carbohydrates -- Periodicals; Chimie organique -- Périodiques; Glucides -- Périodiques; Biochemistry; Carbohydrates; Chemistry, Organic; Periodicals; Electronic journals; 507.78
• DOI: 10.1016/j.carres.2016.04.007
• Languages: English
• ISSNs: 0008-6215

Abstract

Highlights: Hemiesters of carbonic acid and sugars are spontaneously formed in aqueous solutions. Isomers are formed according to the reactivity of the hydroxy group. Higher concentrations of carbonate are observed for sugars with a primary alcohol. d -Glucopyranose 6-carbonate corresponds to 74% of the glucose carbonate in water. Graphical abstract: Abstract: Hemiesters of carbonic acid can be freely formed in aqueous media containing HCO3 − /CO2 and mono- or poly-hydroxy compounds. Herein, 13 C NMR spectroscopy was used to identify isomers formed in aqueous solutions of glycerol (a prototype compound) and seven carbohydrates, as well as to estimate the equilibrium constant of formation ( Keq ). Although both isomers are formed, glycerol 1-carbonate corresponds to 90% of the product. While fructose and ribose form an indistinct mixture of isomers, the anomers ofd -glucopyranose 6-carbonate correspond to 74% of the eight isomers of glucose carbonate that were detected. The values of Keq for the disaccharides sucrose (4.3) and maltose (4.2) are about twice the values for the monosaccharides glucose (2.0) and fructose (2.3). Ribose ( Keq = 0.89)—the only sugar without a significant concentration of a species containing a –CH2 OH group in an aqueous solution—resulted in the smallest Keq . On the basis of the Keq value and the concentrations of HCO3 − and glucose in blood, one can anticipate a concentration of 2–4 µmol L –1 for glucose 6-carbonate, which corresponds to ca. of 10% of its phosphate counterpart (glucose 6-phosphate).