No abstract

Cyclodextrins are frequently used as building blocks, because they can be linked both covalently and noncovalently with specificity. Thus one, two, three, seven, fourteen, eighteen, or twenty substituents have been linked to one β‐cyclodextrin molecule in a regioselective manner. Furthermore, Cyclodextrins may serve as organic host molecules. Their internal cavity is able to accommodate one or two guest molecules. Conversely, suitable guest molecules can be used to thread one, two, or many (one hundred or more) cyclodextrin rings. The resulting supramolecular structures are often formed in solution, which allows characterization by high‐resolution spectroscopic methods. Chemical conversion of these structures provides molecular architectures such as catenanes, rotaxanes, polyrotaxanes, and tubes, which are not readily prepared by other methods. The particular properties of Cyclodextrins can also be employed, for example, for the chromatographic separation of complex mixtures of substances, even racemates, by molecular recognition. Cyclodextrins and their derivatives have been found to be remarkably active catalysts as well. Finally, since Cyclodextrins can favorably influence the release of drugs, many new applications will certainly be developed in the near future.

9] Whereas N-C1Ac-~-piperidine-2-carboxylic acid (N-CIAc-L-pipecolic acid) is a good substrate, N-C1Ac-piperidine, N-C1Ac-piperidine-3-carboxylic acid, and N-ClAc-piperidine-4-carhoxylic acid are not hydrolyzed.[lo] A. Yaron, D. Mlynar, Biochem. Biophy.7. Res.

The first preparation of thin films of cellulose itself is reported. Cellulose exhibits excellent wetting behavior, is extremely stable against oxidation and other chemical degradation and in thin‐film form would have a number of applications. The method involves the preparation of LB films of trimethylcellulose (see Figure) and the in situ conversion of these thin films on silicon substrates to cellulose.