NMR studies of conformations of N-dansyl-L-leucine-appended and N-dansyl-D-leucine-appended beta-cyclodextrin as fluorescent indicators for molecular recognition

The structures of N-dansyl-L-leucine-appended beta-cyclodextrin (1) and N-dansyl-D-leucine-appended beta-cyclodextrin (2) were; estimated by the combined use of 1D and 2D NMR techniques (1D and 2D TOCSY, ROESY, PFG MQF-COSY, PFG HSQC, and NOE difference spectra). The dansyl moiety of 2 is included in its own cavity more deeply than that of 1. The difference in the properties between 1 and 2 was interpreted by the difference in the inclusion depth of the dansyl moieties. Their conformational changes upon addition of 1-adamantanol were also studied by NMR. The chemical shifts and patterns of H-1 resonances far the protons of the dansyl, leucine, and cyclodextrin parts were changed upon addition of the guest. These changes indicated the exclusion of the dansyl moiety from the cyclodextrin cavity to bulk water upon addition of the guest.