Based on X-ray crystallographic data of complexes of chlorodysinosin A with the enzyme thrombin, a series of analogs were synthesized varying the nature of the P1, P2, and P3 pharmacophoric sites and the central octahydroindole carboxyamide core. In general, introduction of a hydrophobic substituent on the d-leucine amide residue dramatically improved the inhibition of the enzyme. This is rationalized based on a better fit of the P3 ...