To develop an efficient sugar extractant on the basis of the mechanistic view a phenylboronic acid bearing a trioctylammonium group at the ortho position (4) was synthesized. To avoid the complexity we employed a simple two-phase solvent-extraction system which corresponds to the first step in membrane transport, i.e., extraction from a donating aqueous phase to an organic liquid membrane phase. The extraction rates and equilibria were estimated using α-p-nitrophenyl-D-glucopyranoside as a sugar and 1,2-dichloroethane as an organic phase and compared with those of a 2-methylphenylboronic acid (5)/trioctylmethylammonium chloride (TOMAC) 1:1 binary system. The extraction rates for 4 were faster by 2.5-29 fold than those for 5 + TOMAC. The distribution coefficients were also enhanced by 5-8 fold. The results indicate that the intramolecular quarternary ammonium group is very effective to neutralize the anionic charge developed in the boron atom upon sugar-binding and create extractable zwitterionic sugar complexes.
All Science Journal Classification (ASJC) codes
- Drug Discovery
- Organic Chemistry