Twenty-four m- and p-(phenoxyalkoxy)beiizamidines bearing a terminal sulfonvl fluoride moiety were synthesized and evaluated as irreversible inhibitors of trypsin; all were excellent reversible inhibitors with Ki = 0.7-3.6 μM. Eight (2, 3, 5, 6, 19-21, 24) were excellent active-site-directed irreversible inhibitors when assayed at a Ki concentration giving 88-100% inactivation. Four (13, 15-17) showed no irreversible inhibition when assayed at an 8K! concentration. The remaining twelve were poor irreversible inhibitors at a >Ki concentration. One of the excellent irreversible inhibitors of trypsin was p-[p-(p-fluorosulfonyibenzamido)phenoxypropoxy]benzamidine (2), which showed no irreversible inhibition of a related “gtryptic” enzyme, namely, thrombin; this specificity is presumably due to the probability that the SO2F moiety of 2 forms a covalent bond “outside” the active site where structural differences between trypsin and thrombin are apt to be present. The possibility of design of inhibitors of opposite specificity, that is, inactivation of thrombin with no inactivation of trypsin, by appropriate modification of benzamidine and phenylgttanidine is discussed. © 1969, American Chemical Society. All rights reserved.
