The structure and (local) stability constants of borate esters of mono- and di-saccharides as studied by 11B and 13C NMR spectroscopy

✍ Scribed by Ron van den Berg; Joop A. Peters; Herman van Bekkum

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 833 KB
• Volume: 253
• Category: Article
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(94)80050-2

✦ Synopsis

The formation of borate esters of various mono-and di-saccharides in aqueous solution was studied by "B and 13C NMR spectroscopy. Association constants K(B-L) at a carbohydrate-borate molar ratio of 1: 1, pH 7, and 25°C were determined and compared with literature values obtained from potentiometry. The association constants K(B-L) were converted into local association constants K&B-L) by using the distribution of the various anomeric forms in D,O. In this way, values of K,,(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-),L were formed.