Sesquiterpene coumarins and related derivatives from Ferula pallida

Six new compounds-two sesquiterpene coumarins, pallidones A and B (1, 2), and four related derivatives, pallidones C-F (3-6), as well as two known sesquiterpene coumarins, feselol (7) and conferol (8), have been isolated from the EtOAc extracts of the roots of Ferula pallida. All structures of these compounds were determined on the basis of spectral evidence, especially 2D NMR ((1)H-(1)H COSY, HSQC, HMBC, and NOESY) and HRMS. The possible biosynthetic pathway of pallidones C-F (3-6) is discussed.