Subscribe to RSS
DOI: 10.1055/s-0032-1321149
Unusual sesterterpenes from the lichen Leprocaulon microscopicum
Leprocaulon microscopicum is a lichen belonging to anamorphic Lecanorales, growing in various countries and widely spread in humide areas of Limousin, France. Its chemical composition is partially described in the literature and publications still mention some unknown substances1. A phytochemical study of acetonic and hydro-methanolic extracts led to the isolation of (-)-usnic acid, dibenzofuran derivatives and terpenes. Among terpenoids, the common triterpene zeorin as well as two new sesterterpenoids (1) and (2) have been characterized in L. microscopicum. Structures were established on the basis of mass spectrometry and 2D NMR experiments. With molecular formulae C25H42O and C25H42O2, the new compounds featured a rare pentacyclic skeleton, closely related to retigeranic acid, the only sesterterpene isolated from lichens2. Thus, the present work notably extends the knowledge of the genus Leprocaulon and lichen chemistry. References: 1. Lamb and Ward (1974) Journ. Hattori Bot. Lab. 38: 499–553. 2. Kaneda et al. (1972) Tet. Let. 13: 4609–4611.