The interaction of the boronic acids with sugar is shortly illustrated
in Scheme 1 [16]. Phenyl boronic acids are weak Lewis acids
with pKas 9. The interaction with a diol increases the electrophilicity
of the boron group, and typical pKas 6 are than observed. At a pH between 6.5 and 8.5, the boronic acid exists under its neutral
form (A, Scheme 1) while, in presence of sugars, its exists under its
anionic form (B and C, Scheme 1).