Discovery and Synthesis of (S)‐3‐[2‐(3,4‐Dimethoxyphenyl)ethoxy] ‐2‐(4,6‐dimethylpyrimidin‐2‐yloxy)‐3,3‐diphenylpropionic Acid (LU 302872), a Novel Orally Active Mixed ETA/ETB Receptor Antagonist.