The correlation of H-1′ to C-1 (δC 162.3), C-2 (δC 110.8) and C-3 (δC 163.9) indicated that 4-hydroxy-3-methyl-2-butenyl unit was located at C-2 of ring A, while those H-1′′ to C-7, C-8 (δC 139.0) and C-8a (δC 112.8) established that the 8-hydroxy-3,8-dimethyl-oct-2-enyl group was attached to C-8 of ring B.