Conformationally Constrained 1,3-Diamino Ketones:  A Series of Potent Inhibitors of the Cysteine Protease Cathepsin K MarquisRobert W. YamashitaDennis S. RuYu LoCastroStephen M. OhHye-Ja ErhardKarl F. DesJarlaisRenee L. HeadMartha S. SmithWard W. ZhaoBaoguang JansonCheryl A. Abdel-MeguidSherin S. TomaszekThaddeus A. LevyMark A. VeberDaniel F. 1998 Conformationally Constrained 1,3-Diamino Ketones:  A Series of Potent Inhibitors of the Cysteine Protease Cathepsin K