DITERPENOID LEAF-GLAND PIGMENTS - 11 COLEONS AND ROYLEANONES FROM COLEUS-CARNOSUS HASSK

Diterpenoid Leaf‐Gland Pigments: 11 Coleons and Royleanones from Coleus carnosus HASSK. The above mentioned plant has been investigated for its leaf‐gland pigments. The following diterpenoids have been isolated (listed according to their elution from Sephadex LH‐20, SiO2 and polyamide; in parentheses the yield of each product in g/kg dried leafs): royleanone (1)/6,7‐dehydroroyleanone (2) (0.004, as a mixture); 7α‐acetyloxyroyleanone (3, 0.009); a novel dimeric diterpene of hitherto unknown structure (0.03); horminone (4, 0.08); 6β‐hydroxyroyleanone (5, 0.04, new as a natural product); 7α‐acetyloxy‐6β‐hydroxyroyleanone (6, 5.45); 6β, 7α‐dihydroxyroyleanone (7, 1.20); 7α‐acetyloxy‐6β, 20‐dihydroxyroyleanone (8, 0.046, a novel compound); coleon U (9, 1.32); coleon V (10, 13.84); carnosolone (6α, 11, 12‐trihydroxy‐6,20‐epoxymethano‐abieta‐8, 11, 13‐trien‐7‐one (11), 1.25, a novel compound). Therefore, this plant is one of the richest one in royleanones and coleons so far investigated by us (pure crystalline compounds 2,3%, estimated total amount > 3% of dry weight). Among the isolated compounds carnosolone (11) is of special interest being the first of a group of colourless diterpenoids from Coleus‐ and Plectranthus‐ species turning blue on TLC. Its oxydation product 12 is one of the rare 4‐acyl‐ortho‐quinones having high reactivity and characteristic spectral properties. Copyright © 1979 Verlag GmbH & Co. KGaA, Weinheim