Cydodextrin dimers

Figure 1.7 The rigid substrate 13 binds in water to cyclodextrin dimer 14 with extremely strong affinity, and the doubly linked cydodextrin dimer 15 binds substrates even more strongly.

Sequence-selective binding of peptides and small proteins is of considerable interest. We saw that some cyclodextrin dimers could selectively doubly bind peptides in water with appropriately placed hydrophobic side chains. This built on our earlier collaborative work on the selective binding of peptides by simple cydodextrin. We then showed that we could break up a protein dimer and a protein tetramer with appropriate cydodextrin dimers in water, since such protein aggregation ordinarily involved hydrophobic side chains that our dimers could bind to. In perhaps the most striking example, our cydodextrin dimers and trimers were able to inhibit the protein aggregation involved in the formation of Alzheimer s plaques. ... 

Breslow, R. and Zhang, B., %ry fast ester hydrolysis by a cydodextrin dimer with a catalytic linking group, /. Am. Chem. Soc., 1992,114, 5882 5883. 

In the next larger cydodextrin, j8-CyD, aliphatic inserts are less popular, although the crystal structures of [3]pseudorotaxanes with aliphatic mono- [25] and diacids [18, 26, 27], diols [28], and bis-imidazolyl hydrocarbons [29] have been reported. j8-CyD/monocarboxylic acid complexes pack in channel structures and create supramolecular polymers, whereas 8-CyD/diacid complexes break the channel structure, contrary to what could be anticipated based on the propensity of acids to dimerize. With the wide y-CyD and aromatic guests, such as Congo Red [14] and ( )-stilbene [15] dimerization of the guest inside y-CyD is observed to form [4] and [3]pseudorotaxanes. Irradiation of crystalline complexes of the latter yielded syn-tetraphenylcyclobutane as a single isomer. 

FIGURE S9.S Monomer(E)- l/dimer(3) equilibrium of a permethylated a-cydodextrin azobenzene dyad. The equilibrium is disturbed by ( )-l- (Z)-l photoisomerization and may be reformed after thermal (2)-l—>( )- isomerization. (From Fujimoto, T Nakamura, A. Inoue.Y., Sakata, Y, and Kaneda, T Tetrahedron Lett., 42(45), 7987,2001. Reprinted with permission from Elsevier Science. Copyright 2001.)... 

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