A synthetic dodecanolide library for the identification of putative semiochemicals emitted by mantellid frogsElectronic supplementary information (ESI) available: Mass spectra of synthetic macrolides and 1H and 13C NMR spectra. See DOI: 10.1039/c7ob00849j

Aliphatic macrolides are used by various organisms as semiochemicals or pheromones, e.g. by the endemic Madagascan frog family Mantellinae. Volatile, methyl-branched aliphatic macrolides occur in various species, but their identification by MS is difficult, while isolation is not possible due to the low amounts produced. Therefore, we synthesized a library of methyl-branched 11-dodecanolides to identify unknown macrolides secreted by Gephyromantis moseri , a mantelline frog restricted to the rainforest and characterized by largely terrestrial habitats. The syntheses used metal-organic epoxide opening and ring-closing-metathesis as key steps. All library members 2-, 4-, 6-, 8-, and 10-methyl-11-dodecanolide were thus identified as part of the secretion by comparison of their mass spectra and their gas chromatographic retention indices. These compounds comprise new natural products. Novel methyl-branched 11-dodecanolide semiochemicals were identified and synthesized in the femoral secretion of Madagascan frog Gephyromantis moseri .