Compounds of the invention are useful in inhibiting carboxypeptidase U and associated thrombotic occlusions having the structure (I) and pharmaceutically acceptable salts thereof, wherein t is N or N(R2'), u is C(R3) or N(R2'), and v is C(R2), N or N(R2), provided that, 1) when t is N and u is C(R3), then v is N(R2); 2) when t is N and u is N(R2'), then v is C(R2), and 3) when t is N(R2') and u is C(R3), then v is N or N(R2).