Covilanone: A New Rearranged Labdane-Type Diterpene.

Abstract— A bicyclic diterpene triol with a new rearranged labdane carbon skeleton was isolated from the aerial parts of Halimiumviscosum (Willk.) Pinto da Silva (S. Joa˜o da Pesqueira). Its structure was established by FAB MS and two-dimensional NMRexperiments ( 1 H/ 1 H, 1 H/ 13 C) and its stereochemistry by NOE and X-ray study. © 2002 Elsevier Science Ltd. All rights reserved. Labdane diterpenes with a [4.3.0]nonane ring B sys-tem are quite rare in the literature. Compound I iso-lated from Gypothamun pinifolium 1 a -hydroxyketonewith an acetyl group on C-7 of the enantiomericseries and Chapaecoderins B and C ( II and III ) iso-lated from Echinodorus macrophillus 2 with a buteno-lide ring are between them.In our studies of Cistaceae components of the IberianPeninsulae, we have isolated from the aerial parts of Halimium viscosum (Willk.) P. da Silva 3–6 bicyclicditerpenes with labadane or halimane skeleton or tri-cyclic diterpenes as valparane and valparolane.The room temperature ethyl acetate extract of