Boronic monosaccharide complexes

Figure 17.4 (a) Preparation of the boronic acid complex, (b) Preparation of the monosaccharide imprinted polyphenol, (c) The competitive assay for the detection of D-glucose using the D-glucose-lmprinted polymer. Reproduced with permission from [46]. 

II. 3, 6 can complex several monosaccharides such as glucose, mannose, galactose and talose to form intramolecular 2 1 boron / saccharide complexes (Figure 1)[8]. The highest affinity (/ ass = 19000 M ) was observed for glucose[8]. Thus, this is the first... 

J. Zhang, C. D. Geddes, and J. R. Lakowicz, Complexation of polysaccharide and monosaccharide with thiolate boronic acid capped on silver nanoparticle. Anal Biochem., 332 (2004) 253-260. 

Another hybrid MIP example is represented by the copolymerization of phenol with a covalently constructed complex between 3-hydroxyphenyl boronic acid (functional monomer) and monosaccharide (template). The copolymer was deposited on a gold electrode by cyclic voltammetry using two successive scans [46]. The obtained polymer presented an irregular morphology with an average thickness of 36 nm. 

Arimori et al utilized the electrostatic interaction to generate dimeric boronic acid-appended porphyrins. Anionic porphyrin 25 and cationic porphyrins 16 form 1 1 complexes, which give the specific exci ton-coupling bands in CD spectroscopy only in the presence of glucose and xylose. The CD sign is characteristic for the absolute configuration of the saccharides. Structural examination established that only these monosaccharides can bridge two porphyrins by ester formation with boronic acid and twist them asymmetrically. 

The reversible formation of boronic esters by the interaction of boronic acids and polyols in water was first examined in the seminal study of Lorand and Edwards [49]. This work followed an equally important study on the elucidation of the structure of the borate ion [124]. By measuring the complexation equilibrium between phenylboronic acid and several model diols and monosaccharides using the method of pH depression, ester formation was shown to be more favorable in solutions of high pH where the boronate ion exists in high concentrations (Equation 19, Figure 1.12). This study also confirmed the Lewis acid behavior of boronic acids and the tetracoordinate structure of their conjugate base, i.e., the hydroxyboronate anion (Section 1.2.2.4). Another conclusion is that free boronic adds have lower Lewis add strengths than their neutral complexes with 1,2-diols. For example, the pJC, of PhB(OH)2 decreases... 

Zinc porphyrin 248 developed by Hirata contains two boronic acid arms, which can rotate around their ethynyl axes." " This rotation allows the distance between the boronic acid receptors to vary between 0.1 and 2.4 nm (Scheme 46). In particular the zinc complex of 248 produces strong CD signals on binding both monosaccharides and oligosaccharides. 

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