Structure of the BPA-Fructose Complex

Abstract

The fructose complex of Boronophenylalanine (BPA) is commonly used for in vivo administration, due to its improved water solubility.1 Until now, however, the detailed molecular structure of the BPA-fructose complex was not yet reported, although the structures of complexes between fructose and p-tolylboronic acid were recently published.2 In this contribution, we present the results of 13C NMR studies of aqueous solutions of BPA and fructose mixtures at varying concentration ratios. Our approach was to directly identify the fructose isomer interacting with BPA, using 2D exchange spectroscopy,3 and propose the structure which most likely results from this interaction. Kitazawa and Yoshino4 independently arrived at an identical structure by analyzing the 1Jcc coupling constants in the NMR spectrum of the complex.