Abstract
In continuing studies on the elucidation of essential factors for the favorable biogenetictype angular methyl migration starting from 5α, 6α-epoxy-eudesman-8β, 12-olide (1) leading to several eremophilanolides, four related eudesmane-type 5, 6-epoxides (4, 5, 6, 7) have been prepared and treated under four different acid conditions. Based on the product analyses, it has been demonstrated that the following three factors seem to be important for the biogenetic-type 10-methyl migration of 1 giving eremophilane-type derivatives : i) the presence of 5α, 6α-epoxide function, ii) the spatial interaction between 10-methyl and 4β-methyl which would bring about distortion of the ring A, and iii) the presence of cis-γ-lactone moiety attached to C-7 and C-8.
