The occurrence of 19,28-bisnorlanostane derivatives in a plant fossil: A novel geochemical degradation process of triterpenoids

Four novel triterpene ketones bearing 24-methyl-28-nor- and 24-methyl-19,28-bisnor-5α-lanostane skeletons were identified in a fossil of a stem of a plant belonging to the Lauraceae family. The structures of these compounds have been determined by comparison of their spectral data with those of authentic specimens derived from lanosterol and 24-methylenecycloartanol. This is the first finding of compounds bearing a 19,28-bisnorlanostane skeleton, which implies a novel possible microbiological pathway of degradation of lanostanes in the sedimentary environment.