Synthesis of 3H- and 14C-cisapride

Cisapride, (±)-cis-4-amino-5-chloro-N[1-[3(4-fluorophenoxy) propyl]-3-methoxy-4-piperidinyl]-2-methoxybenzamide, is a new gastrokinetic drug with a potent stinulating effect on the gastrointestinal motor activity. Metabolic studies required the synthesis of cisapride labelled at one of the three major moieties. Hence, cisapride was tritiated either in the fluorophenyl moiety by means of reductive dehalogenation, or via reductive amination in the piperidine ring. 14C-Cisapride was labelled in the benzamide function. The title compounds were obtained at a specific activity of 17.0 ci/mmol, 59.8 mCi/mmol and 7.8 mCi/mmol, respectively and with HPLC purities of > 98 %. (author)