Synthesis of a CCK₁ Receptor Antagonist

Significance

CCK₁ receptor antagonists are ­potential treatments for irritable bowel syndrome, nonulcer dyspepsia, biliary colic and chronic constipation. The synthesis of the CCK₁ antagonist depicted features (1) a regioselective construction of the pyrazole G through reaction of the hydrazine F with the acetylenic ketone E and (2) a (Z)-selective dehydration of the β-hydroxy ester H.