HL 752: a potent and long-acting antispasmodic agent.

Ester analogues of methyl-2-(4-(2-piperidinoethoxy)benzoyl)-benzoate hydrochloride (pitofenone) (2) were prepared with an aim to find a more potent and metabolically stable antispasmodic compound. The compounds were evaluated for their in vitro and in vivo antispasmodic activity, and stability to in vitro enzymatic hydrolysis. Of the compounds synthesised, HL 752 (21) showed the most potent and long-lasting antispasmodic activity and was selected as the candidate for clinical development.