Sugar tweezer

M. Takeuchi, T. Imada, S. Shinkai, Flighly selective and sensitive sugar tweezer designed from a boronic-acid-appended /z-oxobis[porphinato-iron(lll)], Journal of the American Chemical Society 1996, 118, 10658. 

Takeuchi, M., Imada, T., Shinkai, S. (1996) Highly selective and sensitive "sugar tweezer" designed t rom a boronic-acid-appended i-oxobis[porphinatoiron(III)], J. Am. Chem. Soc., 118, 10658-10659 Idem (1998) Molecular design of highly selective and sensitive "sugar tweezers" from boronic-acid-appended a-oxobis[porphinatoiron(III)]s, Bull. Chem. Soc. Jpn., 71,1117-1123. 

Chemists have known about racemates since Pasteur, at 26 years of age, told the Paris Academy of Sciences how he used tweezers to separate two types of crystals of salts of tartaric acid, which rotate polarized light clockwise (d, dextro) or counterclockwise (l, levo). Unfortunately, this correspondence does not always hold true. In fact, the magnitude and even the direction of optical rotation are complicated functions of the electronic structure surrounding the chiral center. For example, the common enantiomer of the sugar fructose is termed d because of the stereochemical orientation about the chiral atom. But this enantiomer actually rotates the plane of polarization to the left, and its mirror image, L-fructose, rotates the plane of polarization to the right. 

One characteristic of a mixture is that it can be separated into its components by physical processes. The word physical means that the process does not change the chemical identity of a substance. How could you separate a sand/sugar mixture into pure sand and pure sucrose The simplest physical means would be to look at it with a microscope and separate the bits of sugar and sand with tweezers. You are right in thinking that there must be an easier way. 

Scheme 4 Schematic representation showing the two possible ways of binding for the molecular tweezer 25 with sugars.

FIGURE 17.4 (a) Schematic diagram of enzyme entrapment inside a CNTF by liquid-induced shrinkage. The photograph shows a freestanding enzyme-CNTF ensemble film that can be manipulated with tweezers, (b) A stand-alone, self-powered miniature sugar monitor, at the tip of which an FDH SITF ensemble film was wound, (c) A number of the self-powered... 

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