Abstract
Two new sesquiterpenoids, compounds I (3) and II (4), were isolated from the fresh rhizoma of the cultivated Curcuma sp. in Miyakojima island, Okinawa prefecture. The plane structures of the new compounds have been estimated by the NMR spectroscopic studies. Both compounds have the same plane structure bearing a hydroxy group at the C-7 position of curdione (1) or neocurdione (2), indicating that the relationship between the compounds I and II is of diastereoisomer at the C-7 position, as in the relationship between 1 and 2. In spite of the same relative configuration of 3 as 2, the CD spectrum of 3 showed the opposite sign to that of 2. The similar phenomenone was also observed in 4 and 1. Examination of the absolute stereochemistries for 3 and 4 by the CD spectroscopy as well as by the calculation of molecular dynamics using the program of Discover ver. 2.9.5 revealed that both compounds 3 and 4 have the hydrogen-bonding between the carbonyl group at the C-8 and the hydroxyl group at the C-7, causing a conformational change. The absolute stereochemistries of 3 and 4 have thus been established as 4S, 7S-configuration for 3 and 4S, 7R-configuration for 4.
