Carbonic anhydrase inhibitors. V: Pyrylium salts in the synthesis of isozyme-specific inhibitors.

Syntheses and physicochemical properties of 2,4,6-tri-, 2,3,4,6-tetra-, or 2,3,4,5,6-pentasubstituted 1-(2-sulfonamido-1,3,4-thiadiazol-5-yl)pyridinium perchlorates are presented. The new compounds, putative inhibitors of membrane-bound carbonic anhydrase, were tested for inhibitory action on the bovine red cell enzyme.