REGIOSELECTIVE AND STEREOSELECTIVE DEUTERIUM LABELING OF BETA-CYCLODEXTRIN

Reliable methods for the selective deuteration of β‐cyclodextrin are described. Kinetic studies of the proton‐deuterium exchange catalysed by Raney nickel in deuterium oxide show dramatically different behaviours of positions 2, 6 and 3 and allow selective labelling. Deuteration of protons at position 2 can be achieved by performing the exchange procedure at room temperature or preferably at 310 K. Under these conditions, no other positions are affected. At refluxing temperature, protons of the methylene group rapidly exchange and, at longer reaction times, deuteration at C3 takes place. A combination of direct and back exchange cycles affords cyclodextrins labelled on any of the sensitive positions. “Organic shift reagents” are used to assist the NMR analysis of labelled samples and have shown some stereoselectivity for deuteration of the C6 methylene group protons. Copyright © 1990 John Wiley & Sons, Ltd.