Boronic acid-saccharide interactions

One of the clearest pieces of evidence for the reversibility of some covalent interactions came from the work of Gunther Wulff at the University of Dusseldorf, Germany [172], He used imprinted polymers of o-aminomethyl phenylboronic acids as chromatographic stationary phases for the separation of saccharides. Older studies [173] also point to the reversible nature of the boronic acid-saccharide interaction. The pioneering studies of fluorescent transduction of this phenomenon by Czarnik and Yoon [174] (Ohio State University), Aoyama et al. [175] (Kyushu University, Japan), and Shinkai et al. [176] (Kyushu University, Japan) have been reviewed previously [9], Our concern in this review is particularly with the systems that clearly involve PET. Czarnik and Yoon s 93 [177] which interacts with catechol derivatives to produce 94 also belongs here. It... 

Photoinduced electron transfer (PET) has been wielded as a tool of choice in fluorescent sensor design for protons and metal ions. Design of fluorescent sensors for neutral organic species presents a harsher challenge due to the lack of electronic changes upon inclusion. The design of a fluorescent sensor based on the boronic acid saccharide interaction has been difficult due to the lack of sufficient electronic changes found in either the boronic acid moiety or in the saccharide moiety. Furthermore, facile boronic... 

Another possible transcription method is to use chiral metal complexes. Tris[2,2 -bipyridine(bpy)]-metal complexes have inherent A vs. A chirality. It occurred to us that two pyridine rings may be asymmetrically oriented by a boronic acid-saccharide interaction and the metal complexes thus formed may contain an excess... 

Mixed receptors containing boronic acids and charged functionalities were also developed for the recognition of sugar acids [517] and even for heparin [311], a polysul-fated saccharide. Boronic acids also interact strongly with a-hydroxycarboxylic acids [518], and receptors selective for tartrate were reported [519],... 

The final point to be considered in boronic acid - saccharide binding is the predisposition of boronic acids to interact with different kinds of diols. The stability constants (K) between various polyols and boronic acids were first quantified by Lorand and Edwards and it is the case that the trends established now appear inherent in all monoboronic acids. ... 

The observed stability constants (Afobs) for compounds 140( =3)-145( =g) and 146(pyrene) with saccharidcs, which have the ability to form a furanose ring with a jjn-periplanar anomeric hydroxyl pair (o-glucose, melibiose, o-fructose and lactulose) are large, consistent with our understanding of the boronic acid diol interaction. Equally, the low or zero values of the observed stability constants (Afobs) for saccharides unable to form a furanose ring with a. syw-periplanar anomeric hydroxyl pair (maltose and leucrose) are also consistent with current thinking. 

James TD, Sandanayake KRAS, Iguchi R et al (1995) Novel saccharide-photoinduced electron-transfer sensors based on the interaction of boronic acid and amine. J Am Chem... 

Appropriate combinations of boronic acid and fluorophores lead to a remarkable class of fluorescent sensors of saccharides (Shinkai et ah, 1997, 2000, 2001). The concept of PET (photoinduced electron transfer) sensors (see Section 10.2.2.5 and Figure 10.7) has been introduced successfully as follows a boronic acid moiety is combined intramolecularly with an aminomethylfluorophore consequently, PET from the amine to the fluorophore causes fluorescence quenching of the latter. In the presence of a bound saccharide, the interaction between boronic acid and amine is intensified, which inhibits the PET process (Figure 10.42). S-l is an outstanding example of a selective sensor for glucose based on this concept (see Box 10.4). 

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