Pyrrolizidine alkaloids: evidence for N-(4-aminobutyl)-1,4-diaminobutane (homospermidine) as an intermediate in retronecine biosynthesis

Abstract

[1-amino-¹⁵N; 1-¹³C]Putrescine (3) is incorporated into retronecine (2) in Senecio isatideus plants with a labelling pattern consistent with the formation of a symmetrical C₄–N–C₄ intermediate; the intermediate is shown to be homospermidine (4) by ¹⁴C-labelling experiments.