2 ISOMERIC GLYCOSIDE SESQUITERPENES FROM MACHAERANTHERA-TANACETIFOLIA

From the aerial parts of Machaeranthera tanacetifolia the known 12-hyd roxy-ent-kauren-16-en-19-oic acid and the two previously unknown (-)-1 1-O-alpha-D-arabinopyranosyl-beta-eudesmol and (+)-11-O-beta-L-arabino pyranosyl-beta-eudesmol were isolated. The structure elucidation of th ese compounds was based on spectroscopic and chemical evidences. (+)-1 1-O-beta-L-Arabinopyranosyl-beta-eudesmol was fully characterized by X -ray analysis of its peracetate derivative. According with these resul ts, we propose that the previously reported (+)-11-O-alpha-arabinopyra nosyl-beta-eudesmol and 11-O-alpha-D-arabinopyranosyl-beta-eudesmol ar e identical to (+)-11-O-beta-L-arabinopyranosyl-beta-eudesmol. (C) 199 8 Elsevier Science Ltd. All rights reserved.