Enhanced fructose, glucose and lactose transport promoted by a lipophilic 2-(aminomethyl)-phenylboronic acid

A lipophilic 2-(aminomethyl)-phenylboronic acid (1a) was prepared and used to transport saccharides across a thin supported liquid membrane. The result was the highest recorded fructose flux promoted by a monoboronic acid under near-neutral conditions, and one of the highest fructose/glucose transport selectivities (12.9). The application of a pH gradient across the membrane further enhanced carrier-mediated fructose flux but fructose/glucose selectivity was decreased. The first effective transport of a disaccharide, lactose, was achieved using supported liquid membranes containing a high concentration of 1a (250 mM). A strong carrier concentration effect on lactose transport and a battery of mass spectrometry evidence point to the involvement of 2:1 boronate/lactose esters in this transport process.