Limits of the Inversion Phenomenon in Triazolyl-Substituted β-Cyclodextrin Dimers

摘要

Six different β-cyclodextrin (β-CD) dimers have been synthesized by copper-catalyzed azide alkyne cycloaddition. The nature of the spacer connecting the two β-CDs has been varied in length and hydrophilicity. For each dimer, a detailed NMR study was carried out in D_2O. It was found that, whereas β-CD dimers having short spacer exhibited only one conformation, β-CD dimers having long and/or hydrophobic spacers showed two different conformations. Indeed, the latter underwent an inversion process leading to self-inclusion of the spacer in one of the two CD cavities. The behavior of the six β-CD dimers in water has thus been rationalized and this allowed the proportion of "free" cavities actually available for molecular recognition to be determined.