Sugar-boronic acid

The same research group has also exploited the sugar-boronic acid interactions as shown with 7, to create oriented supramolecular assemblies [67-75]. 

Yamamoto, M. Takeuehi. M. Shinkai. S. Tani, F. Naruta, Y. Chirality control of a Cu(I) (phenanthroline)2 complex by a sugar-boronic acid interaction. A preliminary step toward the total chain helicity control by a chain-end sugar-binding. J. Chem. Soc., Perkin Trans. 2 2000 (I), 9-16. 

Since transport is dependent on the rate of diffusion through the membrane, it is anticipated that transport rates should increase as the membrane becomes thinner. This correlation should continue, of course, until the rate of membrane diffusion becomes faster than the kinetics of sugar-boronic acid association. Since the effective membrane thickness associated with a stirred BLM is substantially greater than a SLM, it is expected that transport fluxes will be.greatly increased when the above transport experiments are repeated with SLMs (77,72). Our most recent results with SLMs indicate this to be true (27). 

Takeuchi, M., Chin, Y., Imada, T., and Shinkai, S. (1996) Sugar-boronic acid interactions in the formation of novel chiral porphyrin dimers with various porphyrin-porphyrin angles, J. Chem. Soc., Chem. Commun., 1867-1868. More recently, it was shown that the more likely structure for the D-threitol moiety in the D-threitoM72 complex involves the two six-membered rings rather than the two... 

Further interest is related to the design of adjustable hosts that permit to mimic cooperative interactions present in many biological functions, e.g., for the transport of sugars across cell membranes. In this respect, crown ethers have been functionalized with boronic acid units, e.g., compound 172, so that the... 

Shinkai S. (1997) Aqueous Sugar Sensing by Boronic-Acid-Based Artificial Receptors, in Desvergne J.-P. and Czarnik A. W. (Eds), Chemosensors of Ion and Molecule Recognition, NATO ASI series, Kluwer Academic Publishers, Dordrecht, pp. 37-59. 

Nakazawa, 1. Suda, S. Masuda, M. Asai, M. Shimizu, T. pH-dependent reversible polymers formed from cyclic sugar- and aromatic boronic acid-based bolaamphiphiles. Chem. Commun. 2000, 881-882. 

These gels are based on immobilised alkyl boronic acids. They have a selective affinity for 1,2- or 1,3-diol groupings such as those found in catechol-containing molecules such as dopamine and in sugars or glycosides. 

While most reporter molecules have been designed to interact with cations, Plenio and Diodone [326] reported fluorine containing cryptands, which interact with perchlorate. London and Gabel [327] reported fluorobenzene boronic acid, which interacted with specific sugars. 

Farrall and Frechet recognized the possibility of forming polymer-bound boronic acids in 1976.66 Supported pnra-benzeneboronic acid groups were generated by direct lithiation of polystyrene, giving a para-lithio intermediate that could be used to generate a host of other resins also (Scheme 27). Conversion to the boronic acid was one of the more successful transformations. The purpose of this transformation was to allow the attachment of sugars to the solid phase via the boronate. 

Boronic acid-agarose Compounds with c/s-diol groups sugars, catecholamines, ribonucleotides, glycoproteins... 

Attachment of the alkene monomers to the template (Fig. 6.5), which must be reversible - readily formed and readily broken - to permit removal of the template after polymerisation, can generally be accomplished in two ways covalently or non-covalently. While the latter interactions (ionic, hydrophobic, n-n, hydrogen bonding) can easily be reversed, there is less scope for reversible covalent linkages. One of these is the formation of boronic esters - from boronic acid units of the monomers and OH groups of sugar templates. 

Fig. 8.13 Dendritic sugar sensor based on boronic acid/glycol interaction (G2 = 2nd generation according to Shinkai etal.)-For the sake of clarity only two of the eight end groups are shown in the boxed formula...

Figure 10.2 Equilibrium and conformation of different forms of the boronic acid group with and without sugar. Reprinted with permission from Ref. 69. Copyright 2001 American Chemical Society.

Scheme 20 Boronic acid-modified spiropyran 32 for reversible sugar binding.

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