A modified Polonovski reaction has been employed to obtain the N-demethylated metabolite of the neuroleptic drug cyamemazine. The synthesis involves N-oxide formation, isolation of the corresponding N-oxide, and a FeSO4· 7H2O mediated Polonovski reaction to afford the desired monodesmethyl cyamemazine. In a subsequent step the hapten N- demethylcyamemazine-hemiglutarate was synthesized and its conjugated to bovine ...