Investigation into the stability and reactivity of the pentacyclic alkaloid dehydroevodiamine and the benz-analog thereof

Abstract

Limited synthetic approaches to obtain the biologically active alkaloid dehydroevodiamine (DHED) are known to date. Undesired demethylation in the most widely applied route was found to be a hampering side reaction for the benz-DHED derivative leading to a quinazolinone, which represents a benz-rutaecarpine derivative. For rutaecarpine, a related plant alkaloid, many different synthetic approaches have been described. Alternative reaction procedures to obtain DHED such as methylation of rutaecarpine and oxidation of evodiamine were investigated to make DHED more easily accessible and the latter method proved to be the most successful one. Furthermore, the remarkable equilibrium between the ring closed quinazolinium and the ring open form of the compounds was systematically investigated by UV–vis measurements. The ring open form and the quinazolinium salt, form the same species when incubated in buffer solution for 24 h. A better soluble form, i.e., ‘hydroxyevodiamine’, seems to represent the biologically active form that has not yet been described.