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 13 C‐NMR analysis of the royleanones 1b, 1c, 1e, 1g , and 1h lead to the complete assignment of their spectra.