Two New Retigerane-Type Sesterterpenoids from the Lichen Leprocaulon microscopicum

Two new sesterterpenes, 1 and 2, have been isolated from the lichen Leprocaulon microscopicum. In addition to classic chromatographic methods, a liquid-liquid chromatography technique, namely centrifugal partition chromatography (CPC) was applied for the purification of compound 2. The structures were determined by analyses of mass spectrometry and 1D- and 2D-NMR data. The relative configuration of the isolated compounds was assigned on the basis of 2D-NOESY experiments. The two compounds possess a rare pentacyclic carbon skeleton typical for lichen metabolism, and quite unusual in the vegetal kingdom.