Preparation and screening of diboronate arrays for identification of carbohydrate binders

Boronic acids and their anionic counterpart, boronates, are known to bind reversibly to polyols, such as carbohydrates, under aqueous conditions. Monoboronic acids generally display a common selectivity rank exemplified by fructose > galactose > mannose > glucose. This order can however be modulated by the use of diboronic acids, which may give increased selectivity for e.g. glucose. Diboronic acids have previously typically been prepared and tested individually, but this paper reports a solid-phase method for parallel synthesis of diboronate arrays, along with visual screening of the compounds for carbohydrate binding by competitive binding to alizarin. Diboronate arrays were prepared based on Fmoc-Lys(Boc) and related amino acids, and screening identified diboronates with enhanced affinity to melibiose and glucose.