Diterpenoids from the Rhizomes of Alpinia calcarata

Four new labdane-type diterpenoids, calcaratarins A-D (1-4), along with six known labdane-type diterpenoids, a known elemane-type sesquiterpenoid, and a known coumarin, were isolated from the rhizomes of Alpinia calcarata. The structures of 1-4 were elucidated on the basis of spectroscopic studies.