Aminomethylphenylboronic acid

A new PET-based chemosensor for uronic and sialic acids utilizing the cooperative action of boronic acid and metal chelate was reported by Shinkai and co-workers. This group synthesized a novel fluorescent chemosensor molecule bearing both an o-aminomethylphenylboronic acid group for diol binding to a saccharide and a l,10-phenanthroline-Zn(II)chelate moiety for the carboxylate binding, which enables this sensor to discriminate between neutral monosaccharides and acidic compounds [110],... 

Many monosaccharides possess at least two binding sites, by which they may be distinguished from each other. Thus, by careful manipulation of the spatial disposition of two 2-aminomethylphenylboronic acid groups, it should be possible to con-... 

Koumoto demonstrated that azobenzene derivatives bearing one or two aminomethylphenylboronic acid groups 32 and 33 can be used for practical colorimetric saccharide sensing in neutral aqueous media. The observed stability constants (ATohs) for 33 were 433 for D-fructose and 13.0 M for o-glucose in 1 1 (v/v) methanol/water at pH 7.5 (phosphate buffer). 

Figure 2.2 Modes of boron-nitrogen interaction in an o-aminomethylphenylboronic acid and their resonances in a NMR spectrum.

The rules affecting modes of interaction between boron and nitrogen were further studied by Anslyn et al in 2009. They conducted analyses with the boronate ester formation of several o-aminomethylphenylboronic acids with different degrees of substitution around the nitrogen atom (Scheme 2.8). The experimental results showed that in polar protic solvents increasing the number of substituents on the amine group correlated with a slight increase in the ratio of N-B dative bond to solvent insertion in polar protic solvents. 

Scheme 2.8 Boronate ester formation from o-aminomethylphenylboronic acids.

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