Socialane, a Nonaprenyl Terpene Hydrocarbon Surface Lipid from the Collembola Hypogastrura socialis

Springtails use unique compounds for their outermost epicuticular wax layer, often of terpenoid origin. We report here the structure and synthesis of socialane, the major cuticular constituent of the Collembola Hypogastrura socialis. Socialane is also the first regular nonaprenyl terpene with a cyclic head group. The saturated side chain has seven stereogenic centers, making the determination of the configuration difficult. We describe here the identification of socialane and a synthetic approach using the building blocks farnesol and phytol, enantioselective hydrogenation, and alpha-alkylation of sulfones for the synthesis of various stereoisomers. NMR experiments showed the presence of an anti-configuration of the methyl groups closest to the benzene ring and that the other methyl groups of the polyprenyl side-chain are not uniformly configured. Furthermore, socialane is structurally different from [6+2]-terpene viaticene of the closely related H. viatica, showing species specificity of the epicuticular lipids of this genus and hinting at a possible role of surface lipids in the communication of these gregarious arthropods.