An Optically‐Pure Hemicryptophane as NMR and ECD Responsive Probe for Chloroform

An optically pure hemicryptophane cavitand, in which the primary side of permethylated α‐cyclodextrin (α‐CD) is capped with a C 3 ‐chiral cyclotribenzylene (CTB) derivative, responds to its solution environment, either by electronic circular dichroism or 1 H NMR spectroscopy. In particular, the primary methoxy (6′‐OMe) protons of the α‐CD component behave as solvent sensitive NMR probes. For example, they are more shielded in C 2 D 2 Cl 4 than in CDCl 3 , and their chemical shifts show opposite temperature dependence. A similar contrasted behavior was observed in benzene vs. toluene, suggesting that the observed effects are related to the size of the solvent molecule. Molecular Dynamics simulations indicated that C 2 H 2 Cl 4 and CHCl 3 were included in the α‐CD component of the hemicryptophane, but not in the CTB concavity, with binding energies of –21.1 kJ×mol –1 and –32.7 kJ×mol –1 , respectively.