Inhibition of O-GlcNAcase by PUGNAc is dependent upon the oxime stereochemistry

The potent O-GlcNAcase inhibitor PUGNAc was synthesized and two isomers based on the E and Z stereochemistry of the oxime moiety were separated, defined, and tested for activity. Several lines of evidence were examined in an effort to define the correct stereochemical assignments of each form of PUGNAc. The ability of the Z stereoisomer to undergo the Beckmann rearrangement was ultimately the most definitive proof. It was determined via both in vitro and intact cell experiments that the Z form of PUGNAc was vastly more potent an inhibitor of O-GlcNAcase than the E form.