Cyclodextrins as Building Blocks for Supramolecular Structures and Functional Units

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.

ESI-mass spectrometry analysis of unsubstituted and disubstituted β-cyclodextrins: fragmentation mode and identification of the AB, AC, AD regioisomers

“…[1][2][3][4][5]. The performance is also due to the CD versatility, attributable to the presence of a large number of hydroxy groups on the upper and lower rim, which provide unique opportunities to obtain a virtually unlimited number of derivatives by suitable modification with different neutral or charged groups [6,7], thus allowing a fine tuning of their complexation and recognition properties as well as of their solubility in various solvents. However, the three types of hydroxy groups present at the 2-, 3-, and 6-positions compete for the derivatizing agent making the challenge of selective conversion a daunting task.…”

“…However, the three types of hydroxy groups present at the 2-, 3-, and 6-positions compete for the derivatizing agent making the challenge of selective conversion a daunting task. Many efforts and strategies have been devised in order to obtain selectively functionalized CD derivatives: a great number of mono-and per-functionalized CDs have been reported, whereas only few di-and tri-modified derivatives are known, on account of the difficulties encountered in the preparation and structure determination of the regioisomers [1,6,7]. Regiospecific functionalization is generally achieved by using an excess of a reagent (p-toluenesulphonyl chloride, mesityl chloride, or 3-nitrobenzenesulphonyl chloride) [8,9] or appropriate capping reagents (4,6-dimethoxybenzene-1,3-disulphonyl chloride, benzophenone-3,3'-disulphonyl chloride, biphenyl-4,4'-dis-ulphonyl chloride) [10 -12], which are rigid systems bearing the reactive sulfonyl chloride groups at the right distance for obtaining sulphonated AB, AC, and AD regioisomers with high selectivity.…”

Formation and Function of Nano- and Microstructures by the Self-assembly of Cyclic Oligosaccharides ‘Cyclodextrins’

“…The ability of CDs to form inclusion complexes with guest molecules has been studied academically, and their applications in various industrial fields including food, cosmetics, and pharmaceuticals have been developed (1,2). CDs have many hydroxyl groups on the upper and lower rims of their doughnut-shaped rings, and thus can self-assemble through hydrogen bonding between their hydroxyl groups to form aggregates.…”

Hydrogels having tubular α-cyclodextrin structure: effect of nano-tube structure on long alkyl chain partitions

“…a-, b-, and g-CDs have 18, 21, 24 hydroxyl groups, so that many researchers have tried to modify the groups to improve the physicochemical properties such as aqueous solubility, chemical and physical stability, selective binding, and so on [4]. Recently, CDs are used as a building block for supramolecular structures [5,6]. In the 1990s, a new type of supramolecular assembly consisting of CDs and linear polymers has been reported by Harada et al [7 -9].…”