8α,9α‐Epoxy‐7‐oxoroyleanon, ein Diterpen‐Epoxychinon aus einer abessinischen Plectranthus‐Art (Labiatae)

8α,9α‐Epoxy‐7‐oxoroleyanone, a Diterpenoid Epoxyquinone from an Abyssinian Plectranthus Species (Labiatae) Reexamination of the title plant, in additon to the previously identified abietanoid hydroxy‐1,4‐benzoquinones 1a, 1b, 1c, 1e, 1f, 1g, and 1h, yielded the known 7α‐acetoxyroleanone ( = 7‐O‐acetylhorminone; 1d) and the novel 8α, 9α‐epoxy‐7‐oxoroyleanone (2a). Spectroscopic methods, partial synthesis by epoxidation of 7‐oxoroyleanone (1h), and chiroptical correlation establish the structure 2a. Royleanone 2a is the first diterpenoid epoxyquinone isolated so far. Moreover, a detailed 13C‐NMR analysis of the royleanones 1b, 1c, 1e, 1g, and 1h lead to the complete assignment of their spectra.