Plectranthus genus (Lamiaceae) is known to be rich in bioactive abietane royleanone-type diterpenes, such as 6,7-dehydroxyroyleanone (1, Fig. 1), which have been previously found in P. madagascariensis (var. aliciae Codd). This abietane royleanone presents moderate to significant to cytoxic activity against several cancer cell lines. Moreover, 1 has one hydroxyl group suitable for deri- vatization that can be e...