The pupal defensive secretion of the coccinellid beetle Epilachna borealis
is composed principally of a combinatorial library of several hundred macro
cyclic polyamines. This new family of natural products is characterized by
extremely large-ring monocyclic polylactones, which are derived from the ol
igomerization of three homologous (omega-1)-(2-hydroxyethylamino)alkanoic a
cids. The characterization and quantification of these novel macrocyclic al
kaloids as well as of related open-chain oligomers are described. Via HPLC-
MS analyses of suitable derivatives, macrocycles with ring sizes from 24 to
over 150 members were characterized. Whereas the three building blocks app
ear to be randomly incorporated into these oligomers, comparison with other
ladybird beetle species suggests that the spectrum of ring sizes produced
is carefully regulated.