Four diterpenoids were isolated from the dried leaves and stems of Isodon japonicus HARA. Two of them were shown to be identical with the known isodonal (2) and epinodosin (3). Spectroscopic investigation and a chemical conversion into epinodosin dihydroderivative (10) established the structure and absolute configuration of sodoponin as 11. The structure and absolute configuration of epinodosinol were elucidated as 16, on the basis of spectroscopic data and some chemical evidence. Finally, sodoponin (11) was converted into epinodosinol (16), which confirmed their structures unequivocally.
