Protease inhibitors. Part 2. Weakly basic thrombin inhibitors incorporating sulfonyl-aminoguanidine moieties as S1...

Two series of derivatives have been prepared and assayed as inhibitors of two physiologically relevant serine proteases, human thrombin and human trypsin. The first series includes alkyl-/ aralkyl-/aryl- and hetarylsulfonyl-aminoguanidines. It was thus observed that sulfanilyl-aminoguanidine possesses moderate but intrinsically selective thrombin inhibitory properties, with KI values around 90 and 1400 nM against thrombin and trypsin respectively. Further elaboration of this molecule afforded compounds that inhibited thrombin with KI values in the range 10-50 nM, whereas affinity for trypsin remained relatively low. Such compounds were obtained either by attaching benzyloxycarbonyl- or 4-toluenesulfonylureido-protected amino acids (such as D-Phe, L-Pro) or dipeptides (such as Phe-Pro, Gly His, beta-Ala-His or Pro-Gly) to the N-4 atom of the lead molecule, sulfanilyl-aminoguanidine, or by attaching substituted-pyridinium propylcarboxamido moieties to this lead. Thus, this study brings novel insights regarding a novel non-basic S1 anchoring moiety (i.e., SO2NHNHC(=NH)NH2), and new types of peptidomimetic scaffolds obtained by incorporating tosylureido-amino acids/pyridinium-substituted-GABA moieties in the hydrophobic binding site(s). Structure-activity correlations of the new serine protease inhibitors are also discussed based on a QSAR model described previously for a large series of structurally-related derivatives (Supuran et al. (1999) J. Med. Chem., in press).