As a continuation of the previous work, the structures of four minor products, which were obtained by HCOOH-acetone (1 : 2) treatment of 5α, 6α-epoxy-eudesman-8β, 12-olide (1) along with previously elucidated four products : A (2), B (3), C (4), and D (5), have been elucidated as E (6), F (7), G (8), and H (9). It has become clear that 1 was converted to five eremophilanolides (A, B, D, F, and H) via a biogenetic-type 1, 2-shift of the angular methyl at C-10, and the structure requirement for the ready conversion has been discussed. In addition, preparative liquid chromatography was undertaken to clarify the accurate product composition of the above acid treatment.
