LAUSR

Four new ent-kaurene diterpenoids, phyllostachysins M–P (1–4) have been isolated from the aerial parts of Isodon phyllostachys. Compound 1 features a novel dihydro-2H-pyran ring motif, which was formed by an unusual cleavage in ring-A. 2 and 3 bear a rare 20-nor-ent-kaurene structure, but 4 has a rare 7,20-cyclo-ent-kaurene skeleton. Their structures were elucidated on the basis of extensive spectroscopic analyses. Compounds 1, 3, and 4 were evaluated for their cytotoxic activity against five human tumor cell lines.