Potent glucosidase inhibitors: de-O-sulfonated ponkoranol and its stereoisomer.

Ponkoranol, a glucosidase inhibitor isolated from the plant Salacia reticulata, comprises a sulfonium ion with an internal sulfate counterion. An efficient synthetic route to de-O-sulfonated ponkoranol and its 5'-stereoisomer is reported, and it is shown that these compounds are potent glucosidase inhibitors that inhibit a key intestinal human glucosidase, the N-terminal catalytic domain of maltase glucoamylase, with K(i) values of 43 +/- 3 and 15 +/- 1 nM, respectively.