Dotofide, a Guanidine-Interrupted Terpenoid from the Marine Slug Doto pinnatifida (Gastropoda, Nudibranchia)

An unusual natural product (dotofide, 1), in which the terpenoid skeleton is interrupted by a guanidine moiety was obtained from the marine slug Doto pinnatifida. The absolute configuration of compound 1 was deduced by ozonolysis and subsequent CD spectroscopy. D. pinnatifida subsists on the hydrozoan Nemertesia antennina (Cnidaria), which however does not contain dotofide, suggesting that the snail is able to perform the biosynthesis of the metabolite by itself. D. pinnatifida is grouped into the chemically hardly investigated taxon Cladobranchia (Opisthobranchia, Gastropoda). All members of this taxon completely lack a shell and are thought to employ toxic secondary metabolites or alternatively cnidocysts sequestered from their cnidarian prey organism as defence strategy.