Synthesis, Conformation, and Binding Properties of Cyclodextrin Homo- and Heterodimers Connected through Their Secondary Sides

Using soft-pulse 2D NMR techniques, nearly complete assignments of the 600 and 800 MHz NMR spectra of an octamethylene-spaced β-cyclodextrin (CD) homodimer (1, L=(CH2)8) and a heterodimer with one α- and one β-CD can be made. These clearly show the self-inclusion of the aliphatic spacer in one of the CD units. When, for example, a short ethylene spacer is used to connect the CDs, this self-encapsulation can not occur. This difference in behavior markedly affects the binding properties of the different dimers. L=(CH2)2,(CH2)8,2,2′-bipyridyl.