orlistat open ring acid impurity

Orlistat open ring acid impurity is a degradation byproduct formed via hydrolytic cleavage of the cyclohexane ring in orlistat's α,β-unsaturated δ-lactam core, resulting in a linear carboxylic acid moiety conjugated to the remaining fluorophenylbutyrate chain. The compound retains the (S)-configuration at the chiral center adjacent to the hydrolyzed lactam, featuring a terminal hydroxyl group and a conjugated enone system. This structural alteration disrupts the parent drug's lipase-inhibitory pharmacophore. It serves as an HPLC reference standard for quantifying orlistat degradation pathways under acidic stress conditions.