Thiasugars as potential glycosidase inhibitor

Abstract

The potential of synthetic thiasugars, the ring sulfur analogs of carbohydrate, as glycosidase inhibitor was discussed in terms of activity and specificity, based on our own studies. The syntheses of these analogs including di- and tri-saccharide derivatives were also outlined. 5-Thiofucose was the first thiapyran to show a Ki value of micromolar range against a glycosidase. The structure-activity relationship studies indicated that its fucosidase inhibition was due in part to a hydrophobic interaction between the ring sulfur and the enzyme. A sulfylimine compound having a thiafuran structure was created as a transition-state analog inhibitor of glucosidases and found to have a weak activity. The same thiafuran structure was later found by another group in a natural product, salacinol, which is a sulfonium derivative and is a strong glucosidase inhibitor. The structure-activity relationship study with synthetic analogs of salacinol indicated importance of the sulfonium ion and its internal counter anion, sulfate, for the inhibition activity.