An improved synthesis of butyl 4-[(4-amino-5-chloro-2-methoxybenzoyl)amino]-1-piperidineacetate (AU-224).

A new and facile route for the synthesis of the novel gastrointestinal prokinetic butyl 4-[(4-amino-5-chloro-2-methoxybenzoyl)amino]-1-piperidineacetate (1b), which exhibited potent gastro- and colon-prokinetic activities by oral administration without significant side effects, was established. The key intermediate, butyl 4-amino-1-piperidineacetate (16), was prepared from commercially available 4-amino-1-benzylpiperidine (2) in a high yield with four steps. Compound 1b was prepared by condensation of commercially available 4-amino-5-chloro-2-methoxybenzoic acid (7) with 16 in 84% yield. This improved synthetic route was appropriate for large-scale synthesis of 1b.