Xian-Ye-Xuan-Fu-Hua, the flowers of Inula linariaefolia Turcz (Compositae), is a commonly known Chinese medicinal herb and used as expectorant as well as for the treatment of some malignant tumors. The chemical investigation of its active principles by our early work in 1964 resulted in the isolation of a new sesquiterpene lactone (m.p. 190-192`C, (α)D-24 in CHCl3), which possesses significant inhibitory action against Hela cells and fungi in vitro. Besides, it also shows some expectorant activity in preliminary pharmacological tests. Analyses of the spectral data (IR, UV, ^1H NMR, 13C NMR, MS) and our early results of chemical reactions suggested that the compound is the same as britanin 1 (m.p. 192-194`C, (α)D-26 in CHCl3) studied Chugunov in 1971. However its stereochemistry remained unsolved. On careful examination of the 360 MHZ 1H NMR data (in CDCl3 and in C6D6) and the Cotton effects of ORD spectra of its saturated lactone and cyclopentanone derivatives, we considered that britanin must be ambros-11(13)-en-2β, 4β, 6α, 8α-tetraol-12-oic-(12,8)- lactone, 2, 6-diacetate (7). Since the large values for J6,7, J7,8, J8,9, J9,10 and J1,10 indicate the existence of successive a-a trans coupling in all vicinal protons form C6 to C1, the cofnformation of the cycloheptane ring must be in chair from. The other constitutent isolated from the same plant has been identified as taraxasteryl palmitate.

Key words: LACTONES, CHEMICAL COMPOSITION, SESQUITERPENE, INULA JAPONICA