Conformational Analysis of Cyclodextrins and Their Methylated Analogs

The NMR chemical shifts and coupling constants for -, permethyl--, -and permethyl--cyclodextrins in neutral aqueous media were assigned based on the 470MHz spectra. In order to obtain accurate chemical shifts and coupling constants the experimental spectra were analyzed with the Raccoon spin simulation program. The rotamer distribution around the bond of the cyclodextrins evaluated from the coupling constants of and . In our calculation of the -, and -cycliodextrin showed that gg conformers were most favorable form and tg conformers were least favorable form. It is very interesting to note the changes in , coupling constants of permethylated - and -cyclodextrins from unmodified one. The gg conformers were more increased than unmodified one and instead of tg conformers gt conformers were least favorable one upon methylation.