GLYCYRRHETINIC ACID-DERIVATIVES AS POTENT INHIBITORS OF NA+, K+-ATPASE - SYNTHESIS AND STRUCTURE-ACTIVITY-RELATIONSHIPS

A series of ring A-modified GA derivatives (26 compounds) has been systematically synthesized and the structure-activity relationship investigated for inhibition of canine kidney Na+, K+-ATPase in vitro. The most potent inhibitory activity was found with a group of the 3-deoxygenated derivatives including 5, 6, 9, 10 and 11. The high inhibition may be closely related to the hydrophobic character of the A-ring of these compounds. This finding suggests that the ATP-binding site at the active center of the enzyme is located in a hydrophobic environment.