The biosynthesis of retronecine

Abstract

An experiment with putrescine, doubly labelled intramolecularly, with 15N and 13C at the adjacent C-atom, demonstrates that a C4–N–C4 compound with C2v symmetry serves as a precursor of retronecine, the most common base of the Senecio alkaloids. The C4–N–C4 compound is, in turn, generated from two ornithine-derived precursor units. This was demonstrated by a degradation sequence whereby the distribution of label from [5-14C]-, [5-3H]-, and [4-3H]ornithine within retronecine was fully accounted for.