Isopimarane and nor-diterpene glucosides from the twigs and leaves of Lyonia ovalifolia

Abstract

Eight new isopimarane diterpene glucosides (1–8) and one new nor-diterpene glucoside (9) were isolated from the twigs and leaves of Lyonia ovalifolia. The structures of the new compounds (1–9) were determined based on extensive spectroscopic analysis, including HRESIMS, and 1D and 2D NMR data. The absolute configuration of compounds 1a (the aglycone of 1) and 6a (the aglycone of 6) were established using X-ray crystallography, those of compounds 2, 4, and 5 were established by ECD experiments, and that of compound 9 was established using a modified Mosher method. These isopimarane diterpenes are the first isolated from the Ericaceae family. Compound 9 is the first diterpene glucoside found in nature with the novel 14,15-dinor-9,10-seco-labdane skeleton. Anti-bacterial testing showed that compounds 3–7 have inhibitory effects against different strains at the concentration of 10−4 moL/L.