The structure and (local) stability constants of borate esters of mono- and di-saccharides as studied by 11B and 13C NMR spectroscopy.
The formation of borate esters of various mono- and di-saccharides in aqueous solution was studied by 11B and 13C NMR spectroscopy. Association constants K(B-L) at a carbohydrate-borate molar ratio of 1:1, pH 7, and 25 degrees C were determined and compared with literature values obtained from potentiometry. The association constants K(B-L) were converted into local association constants Kloc(B-L) by using the distribution of the various anomeric forms in D2O. In this way, values of Kloc(B-L) were obtained, which appear to be characteristic of the configuration concerned. They explain the favourable effect of borate in the alkaline isomerisation of lactose into lactulose. At a low molar ratio (1:3) of carbohydrate-borate, predominantly diborate esters (B-)2L were formed.
van den Berg
R
R
Laboratory of Organic Chemistry and Catalysis, Delft University of Technology, Netherlands.
Peters
J A
JA
van Bekkum
H
H
D001881:Borates; D001895:Boron; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002247:Carbon Isotopes; D004187:Disaccharides / Q000737:chemistry*; D004355:Drug Stability; D004952:Esters; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008969:Molecular Sequence Data; D009005:Monosaccharides / Q000737:chemistry*
D001881:Borates; D002247:Carbon Isotopes; D004187:Disaccharides; D004952:Esters; D009005:Monosaccharides; D001895:Boron