Sugars boronates

Sugar-derived enol triflates were also elfective in (3-aIkyl Suzuki coupling reactions with sugar boronates and provide a route to fused polycyclic ether like ciguatoxin [292]. 

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). 

Nagai, Y., Kobayashi, K., Toi, H., and Aoyama, Y. (1993) Stabilization of sugar-boronic esters of indolylboronic acid in water via sugar-indol interaction A notable selectivity in oligasaccharides. Bull. Chem. Soc., Jpn., 66, 2965-2971. 

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... 

Syntheses of 6-Deoxy-2- and 3-O-methyl-D-allose and Some 6-Deoxyhexopyranoside Phenyl-boronates," J. S. Brimacombe, A. Husain, F. Hunedy, and M. Stacey, Adv. Chem. Sen, No 74 ( Deoxy-sugars") (1968) 56 - 69. 

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... 

Boronate/diol reaction Chemical stimulation (e.g., sugar) [32]... 

It is of interest to note that the anomeric effect directs the boron substituent into the a-configuration in the case of mannose, despite the considerable steric demand. NMR studies in solution indicate that the usual 4Q conformation of the pyranose is retained, with the boron substituent in the axial position. Depending on the sugar moiety, tumor uptake is observed when the compounds are given to tumor-bearing animals. Accumulation is, however, only transient, and within a fairly short time, the boron is lost from the tumor, and from other tissues. Even at... 

Fig. 2. Concept of molecular imprinting - the covalent approach. 1. Derivatization of sugar template with p-vinylphenyl boronate. 2. Polymerization in the presence of a cross-linker...

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. 

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