Formation of isomers of anionic hemiesters of sugars and carbonic acid in aqueous medium.
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 of d-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 -CH2OH 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).
Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, São Paulo, SP 05508-000, Brazil.
Vagner B
VB
Dos Santos
Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, São Paulo, SP 05508-000, Brazil.
Denis T R
DT
Vidal
Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, São Paulo, SP 05508-000, Brazil.
Kelliton J M
KJ
Francisco
Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, São Paulo, SP 05508-000, Brazil.
Lucas C
LC
Ducati
Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Av. Prof. Lineu Prestes, 748, São Paulo, SP 05508-000, Brazil. Electronic address: claudemi@iq.usp.br.
Claudimir L
CL
do Lago
D002241:Carbohydrates / Q000737:chemistry*; D066241:Carbon-13 Magnetic Resonance Spectroscopy / Q000379:methods; D002255:Carbonic Acid / Q000737:chemistry*; D004952:Esters / Q000138:chemical synthesis* / Q000737:chemistry; D005990:Glycerol / Q000737:chemistry; D007536:Isomerism; D015394:Molecular Structure; D014867:Water / Q000737:chemistry
D002241:Carbohydrates; D004952:Esters; D014867:Water; D002255:Carbonic Acid; D005990:Glycerol
Hemiester of carbonic acid; Isomers; Monoalkyl carbonate; NMR spectroscopy; Sugar carbonate