Abstract
The plants of the genus Hypericum (family Clusiaceae) have been used as traditional remedies in several parts of the world. These plants are known to contain various types of compounds (e.g. terpenoids, naphtodianthrones, xanthones, flavonoids, and prenylated acylphloroglucinols). During our search for structurally interesting compounds from Hypericum spp., we investigated three spices of the Hypericum plants, and isolated eight new meroterpenoids, biyoulactones A-C(1-3), yezo'otogirins A-C(4-6), and yojironins A (7) and B (8). Biyoulactones A-C(1-3) were isolated from the roots of Hypericum chinense. The gross structure and relative stereochemistry of biyoulactone A (1) were assigned on the basis of spectroscopic evidences, and which were confirmed by a single crystal X-ray diffraction analysis. The analysis was also disclosed the absolute stereochemistry of 1. Biyoulactone A (1) is a meroterpenoid with a unique dilactone structure containing C-C bonded bi- and tricyclic γ-lactone moieties. Biyoulactones B (2) and C (3) were elucidated to be stereoisomers of 1 by the 2D NMR analysis. The investigation of the aerial parts of H. yezoense resulted in the isolation of yezo'otogirins A-C (4-6). They were assigned as tricyclic compounds possesing fused cyclohexene, cyclopentane, and tetrahydrofuran rings by the analysis of spectroscopic data. The absolute stereochemistries of 4-6 were elucidated based on the analysis of CD spectrum. The structures including the relative stereochemistries of yojironins A (7) and B (8), which were isolated from the whole plants of H. yojiroanum, were also assigned. Yojironin A (7) is a meroterpenoid having a y-butyrolactone moiety, and yojironin B (8) is an epimer of 7. Yojironin A (7) exhibited antimicrobial activity.
