Structure-Activity Relationship of Cantharidin Derivatives to Protein Phosphatases 1, 2A1, and 2B.

The effects of structural modification of cantharidin on the inhibition of protein Ser/Thr phosphatases are described. Removal of the methyl substituents at C2 and C3 in cantharidin improved the inhibition of PP2B. In contrast, introduction of a substituent to C1/C4-position drastically decreased inhibition of PP1 and PP2A1. PP2B was found to be quite tolerant to modifications at the C5 position.