Novel bis(benzamidino) compounds with an aromatic central link. Inhibitors of thrombin, pancreatic kallikrein, trypsin, and complement.

A series of novel aromatic diamidines was synthesized and evaluated for antiproteolytic activity. The compounds were distignuished by inclusion of an aromatic ring structure--either benzene or bisbenzene or naphthalene--in the link between two amidinobenzene moieties. A highly potent inhibitor of bovine thrombin was discovered in alph, alph'-bis(4-amidino-2-iodophenoxy)-p-xylene with a Ki value of 1.1 X 10(-7) M (pH 8.1, 37 degrees), while alpha, alpha'-bis(4-amidino-2-iodophenoxy)-m-xylene was found to be an outstanding inhibitor of porcine pancreatic kallikrein (Ki = 3.1 X 10(-8) M). Several of the compounds investigated also demonstrated a considerable blocking effect on typsin and on the complement-dependent immune lysis of red cells.