Cyclodextrins as chiral complexing agents in water, and their application to optical purity measurements

The interaction of β‐cyclodextrin with propanolol hydrochloride was shown by NMR to produce diastereomeric pairs observable in D2O solution at 400 MHz. By addition of racemate to pure (–)‐isomer, the usefulness of this novel technique in being able to measure optical purity in water down to the 1% level was demonstrated. Using changes in chemical shifts and NOE effects, a possible structure for the inclusion complex is proposed. γ‐Cyclodextrin induced larger shifts in the spectrum than the β‐equivalent, whereas α‐cyclodextrin had no effect.