Discovery of a Factor Xa Inhibitor (3R,4R)‐1‐(2,2‐difluoro‐ethyl)‐pyrrolidine‐3,4‐dicarboxylic Acid 3‐[(5‐Chloro‐pyridin‐2‐yl)‐amide] 4‐{[2‐Fluoro‐4‐(2‐oxo‐2H‐pyridin‐1‐yl)‐phenyl]‐amide} as a Clinical Candidate.