SYNTHESIS AND KINETIC-STUDIES OF AN AMIDINE-CONTAINING PHOSPHONOFLUORIDATE - A NOVEL POTENT INHIBITOR OF TRYPSIN-LIKE ENZYMES

The amidine-containing alpha-amino alkylphosphonofluoridate 3 (Cbz-(4- AmPhGly)(P)(OPh) (F)) is a very potent inhibitor of trypsin-like enzym es. It was prepared by hydrolyzing the corresponding phosphonate diphe nyl ester 4 followed by reaction of fluoride with the phosphonochlorid ate prepared from the intermediate phosphonic acid monoester 5. Compou nd 3 is the most potent amidine-containing organophosphorus inhibitor yet reported for trypsinlike enzymes. It inhibits trypsin and thrombin with second-order rate constants (k(obs)/[I]) of 2.6 x 10(5) M-1 s(-1 ) and 1.0 x 10(5) M-1 s(-1), respectively, showing a 130-fold and a 12 50-fold rate enhancement over the corresponding diphenyl ester (4). It also inactivates trypsin 2 orders of magnitude more potently than sim ple phosphonofluoridates such as DFP,(1) Sarin and soman. The phosphon ofluoridate 3 does not inhibit other serine proteases such as porcine pancreatic elastase (PPE) and the esterase acetylcholinesterase (AChE) . The phosphonofluoridate 3 is hydrolyzed rapidly in buffer solution a nd has a t(1/2) of 4.5 s at pH 7.5. (C) 1998 Elsevier Science Ltd. All rights reserved.