two isomeric glycoside sesquiterpenes from machaeranthera tanacetifolia

Abstract

From the aerial parts of Machaeranthera tanacetifolia the known 12-hydroxy-ent-kauren-16-en-19-oic acid and the two previously unknown (-)-11-O-alpha-D-arabinopyranosyl-beta-eudesmol and (+)-11-O-beta-L-arabinopyranosyl-beta-eudesmol were isolated. The structure elucidation of these compounds was based on spectroscopic and chemical evidences. (+)-11-O-beta-L-Arabinopyranosyl-beta-eudesmol was fully characterized by X-ray analysis of its peracetate derivative. According with these results, we propose that the previously reported (+)-11-O-alpha-arabinopyranosyl-beta-eudesmol and 11-O-alpha-D-arabinopyranosyl-beta-eudesmol are identical to (+)-11-O-beta-L-arabinopyranosyl-beta-eudesmol. (C) 1998 Elsevier Science Ltd. All rights reserved.